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Concentrate supplementation responses of the pasture-fed dairy cow
Livestock Science 104 (2006) 292 – 302 www.elsevier.com/locate/livsci
Concentrate supplementation responses of the pasture-fed dairy cow Auvo Sairanen a,*, Hannele Khalili b, Perttu Virkaja¨rvi a a b
MTT Agrifood Research Finland, North Savo Research Station, FIN-71750 Maaninka, Finland MTT Agrifood Research Finland, Animal Production Research, FIN-31600 Jokioinen, Finland Received 13 December 2005; accepted 18 April 2006
Abstract The aim of this study was to investigate the effects of increasing amounts of cereal-based concentrate on milk production. The study consisted of a series of three separate experiments in which cows were grazed in intensive rotation on timothymeadow fescue pasture. In Experiment 1, 28 multiparous Holstein–Friesian cows received 0, 3, 6 and 9 kg concentrate in a cross-over designed trial with a fixed daily herbage allowance of 21 kg DM/cow. The energy-corrected milk yield increased linearly 0.84 kg/kg DM ( P b 0.001), up to the 9kg concentrate level. The milk fat ( P b 0.001) and urea ( P b 0.001) content decreased linearly (0.41 g/kg DM and 0.15 mmol/kg DM, respectively). The milk protein content tended ( P = 0.08) to increase 0.10g/kg DM with increasing supplementation. In Experiment 2, 17 primiparous cows and 28 multiparous cows were used in a randomized-block designed trial with 3, 6 and 9 kg concentrate supplementation and a fixed 25 kg DM herbage allowance. The energy corrected milk yield increased linearly ( P b 0.01) 0.67kg/kg DM, whereas the milk urea content decreased linearly ( P b 0.001) 0.27 mmol/kg DM. The milk protein content increased and the fat content decreased, but these differences were not significant. In Experiment 3, a cross-over design was used to assess the response to concentrate supplementation of 24 multiparous cows (treatments: 6, 9 and 12 kg; fixed herbage allowance 25 kg DM) and 12 primiparous cows (treatments: 4, 7 and 10 kg; herbage allowance N 25 kg DM). The energy-corrected milk yield of the multiparous cows varied quadratically ( P quad b 0.001; 30.0, 32.5 and 32.2kg for 6, 9 and 12 kg supplementation, respectively). Supplementation linearly decreased the urea ( P b 0.001) 0.13mmol/kg DM and fat ( P b 0.001) 0.46 g/kg DM contents. The milk fat content also varied quadratically, showing the lowest content with the 12 kg level ( P quad b 0.05; 37.3, 37.3 and 34.9g/kg for 6, 9 and 12 kg supplementation, respectively). The energy-corrected milk yield of the primiparous cows increased linearly ( P b 0.001) 0.54 kg/kg DM up to 10 kg supplementation, whereas the milk urea ( P b 0.001) and fat contents decreased linearly ( P b 0.01) by 0.19 mmol/kg DM and 0.61g/kg DM, respectively. The results showed that the milk response remained linear up to the 9 kg supplementation level, but the highest level of supplementation resulted in only a marginal increase in milk yield. There was no interaction between season and milk or milk protein yield, which indicates that it is possible to maintain stable grazing conditions during the main grazing season in Nordic
* Corresponding author. Tel.: +358 17 2644823; fax: +358 17 2644851. E-mail address: [email protected] (A. Sairanen). 1871-1413/$ - see front matter D 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2006.04.009
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latitudes. The results support to some extent the hypothesis that the marginal milk response to supplementation increases with increasing milk production. D 2006 Elsevier B.V. All rights reserved. Keywords: Dairy cattle; Grazing; Concentrate feeding
1. Introduction The nutritional value of well-managed grass is high and on good quality pasture a cow’s welfare can be maintained with low levels of concentrate supplementation or even none (Kennedy et al., 2003; Woods et al., 2005). However, supplementary concentrate feeding is given to grazing dairy cows to achieve an economic production level or to ensure performance during periods of weak grass growth. Concentrate supplementation might also decrease loss of body reserves. Additional concentrate feeding increases the total dry matter intake (DMI) and, consequently, the milk yield. The average milk yield response has been 1 kg/kg concentrate (review of Bargo et al., 2003). The use of concentrate is economically justified if the marginal response (MR, kg energy-corrected milk/kg increased concentrate DM) is positive and the cost of the concentrate is lower than the value of milk yield. Pasture is usually the cheapest feed in cow feeding, but the utilization of a high herbage allowance is low (Dalley et al., 1999; Virkaja¨rvi et al., 2002) and cows may not reach their milk production potential without energy supplementation. Supplementation can also be uneconomic if the supply of good quality pasture is sufficient to meet herd demand, and the increased concentrate mostly substitutes grass. The marginal response to concentrate is dependent on many different factors such as herbage allowance (HA, kg DM), herbage quality, concentrate amount, concentrate type, cow’s energy balance, lactation stage and cow’s genetic strain (Stakelum, 1993; Khalili and Sairanen, 2000; Peyraud and Delaby, 2001; Woods et al., 2003; Horan et al., 2005). Thus, determination of the overall MR function is very complicated. The main observation is that the MR diminishes with increasing amount of ME intake (Woods et al., 2003) and increases when the quality or the amount of the basal diet is restricted (Peyraud and Delaby, 2001). Many studies have quantified the
effects of supplementation on the performance of dairy cows, but usually the weakness of these studies has been the low number of supplementation levels used to estimate the response curve. Furthermore, the amount of concentrate has often been low or moderate compared to the production potential of modern cows which make it difficult or impossible to estimate the relevant MR function. This study focuses on evaluating the MR between 0 and 12 kg of supplementation among three experiments using a fixed herbage allowance and cereal grain-based concentrate. The second aim is to clarify whether the MR is dependent on the cow’s milk production or the grazing season.
2. Material and methods 2.1. Pastures, grazing management and herbage mass measurement The study was carried out at MTT Agrifood Research Finland and consisted of a series of three different experiments which were conducted in 2000– 2002. The amount of concentrate and the lactation stage of the cows were the main differing factors among the experiments. The cows were housed in a tie stall and grazed in intensive rotation with front and back fences from the beginning of the grazing season in May. The rotation length was chosen to increase from 2weeks in June to 4 weeks in August due to differences in growth rate of the grass. The target herbage mass (HM) remained between 2000 and 3500kg DM/ha. All the paddocks were grazed five times during the summer and pastures were mechanically clipped to a height of 10cm after the second, third and fourth grazing cycles. The pastures were 1–3-year-old mixed swards established with a mixture of timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) at a ratio of 70:30 (w/w). The pastures were fertilized three times during each growing season. The
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N fertilization rate was 220kg/ha/year and the P and K applications were adjusted according to soil analyses. Fertilizers were applied as three dressings, the first before the grazing season and the other two at intervals of approximately 4 weeks. Prior to commencing the trials, the cows were offered grass silage ad libitum with a target amount of 10% refusal. In addition, the cows were offered 11 kg of an oats–barley–rapeseed expeller (40–40– 20%, w/w) concentrate containing 175 g crude protein/ kg DM. The cows were turned out to pasture at the end of May for 6 h each day until kept outdoors day and night, usually after a 1-week transition period. During this period, the amount of silage was reduced gradually and the cows were adjusted to their concentrate treatments according to the experimental design. In all the experiments, the pre-grazing HM was estimated using a modified method described by Stocdale (1984). In this method, the sward surface height of the daily grazing area was measured by a rising plate meter (3.5 kg/m2). Three representative sampling areas were chosen based on the previously measured mean pressed sward height of the current paddock. In each area, the disk height was recorded and then a frame of 20 50cm was placed on the ground and the herbage inside the frame was cut to a height of 3cm. The samples were oven-dried at 1358C for 5h and weighed. The HM/ha was corrected by multiplying by the mean disk height of the paddock/ disk height of the sample. Sward height was measured with a HFRO type sward stick (Bircham, 1981) using 20–30 measurements per strip (pre grazing) or 40–50 measurements (post grazing). The measurements were divided into three categories: frequently grazed, infrequently grazed or trampled vegetation. Possible null observations, i.e. no hits on living vegetation, were omitted from the data. 2.2. Cows and experimental design 2.2.1. Experiment 1 Twenty-eight Holstein–Friesian multiparous cows (pre-experiment milk yield 34.8 kg/day, F (S.D.) 5.7kg; 105days in milk (DIM), F43 days; live weight (LW) 602 kg, F72 kg) were used in a carry-over-effect balanced cross-over design with the aim of studying the effect of pelleted concentrate supplementation
(0 kg, 3 kg, 6kg and 9 kg/day) on the milk yield. The concentrate consisted mainly of grain and cereal byproducts (Table 1). The cows were divided into six blocks according to parity, pre-experiment milk yield, calving date and days in pregnancy and randomly assigned to concentrate supplementation sequences within the blocks. The experiment comprised three 21-day periods which were divided into a 16-day transition period and a 5-day data collection period. The first period started in the beginning of June. After each period, the cows were changed over to the next concentrate level by 1.5 kg/day steps. The increment of the concentrate supplementation was 1 kg/day when the total daily amount of concentrate exceeded 6 kg. The concentrate and mineral mixture (0.3 kg/day) was offered in the barn as four equal meals at 06:00, 08:00, 16:00 and 17:30 h. The daily herbage allowance per cow was visually estimated to remain in the range 20–30 kg DM/day for days 1–11 of each period when the cows grazed as a single herd. The herbage allowance was measured daily and fixed at 21 kg DM/cow for days 12–21 of each period when the different concentrate level groups grazed separately. 2.2.2. Experiment 2 The study involved 45 Holstein–Friesian cows (17 primiparous and 28 multiparous; pre-experiment milk yield 30.8kg/day, F 7.0kg; 131 DIM, F61 days; LW 588 kg, F57 kg) in a randomized-block design. At the end of the pre-trial period, the cows were blocked in seven blocks according to parameters described in Table 1 Ingredients of concentrates
g/kg Barley Oats Molassed sugar beet pulp Wheat bran Palm kern expeller Rapeseed expeller Molasses Rapeseed oil Vitamin + mineral mixture
Experiment 1
Experiment 2
Experiment 3
400 100 250
400 100 200
382 100 200
100 113 55 2 30
125 100 55 6 32
50 104 55 12 29
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Experiment 1. Three concentrate feed levels (3 kg, 6 kg and 9kg/cow) were randomly assigned to the cows within the blocks. The experiment lasted 80 days and it was divided into three periods; June, July and August which each included an 8-day grass intake measurement period. The cows grazed as a single group, except during the intake measurement periods, with an HA of 25 kg DM/cow. The HA was higher than in Experiment 1, because it was supposed that HA 21kg might not be optimal for milk production with the cows used. The pre-grazing HA was measured daily during the intake measurement periods, otherwise every second day. Grass intake was measured during the last 5 days of each intake period as the difference between the daily pre-grazing and post-grazing herbage mass. The postgrazing HM was measured daily by cutting 2 8 rectangles of 0.1m2 for each concentrate supplementation group. 2.2.3. Experiment 3 The experiment included two separate trials with 12 primiparous (pre-experiment milk yield 27 kg/day, F2.0kg; 161 DIM, F 42 days; LW 499 kg, F27 kg) and 24 multiparous cows (pre-experiment milk yield 34 kg/day, F4.8 kg/day; 115 DIM, F 46 days; LW 590 kg, F58 kg). Three concentrate levels (4 kg, 7 kg and 10 kg/day for primiparous and 6 kg, 9kg and 12 kg/day for multiparous cows) were allocated to the cows in a balanced Latin Squares design. The primiparous cows were blocked in two and multiparous cows in four blocks according to the parameters described in Experiment 1. The cows were randomly assigned to the treatment sequences within the blocks. The length of each of the three periods was 30 days which comprised a 20-day transition and a 10-day data collection period. The multiparous cows grazed in separate groups with a HA of 25 kg DM/day during the data collection period and the primiparous cows grazed as a single herd. During the transition period all the cows grazed as a single group and the HA was visually estimated to be more than 25 kg DM/day. 2.3. Sample collection and analysis The cows were milked indoors at 07:00 and 16:00 h and the milk yields were recorded daily. The average
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values of the data collection periods for each cow were used in statistical analyses in Experiments 1 and 3, whereas averages of monthly values by cow were considered as a repeated measurement in Experiment 2. Milk samples from six consecutive milkings at the end of the data collection period (intake measurement period in Experiment 2) were analysed separately for fat, protein, lactose and urea content using an infrared analyzer (Milcoscan FT6000). The milk composition was determined based on the weighted means of the a.m. and p.m. milkings. Live weight was measured after turnout and at the end of each period. Grass samples for chemical analysis in Experiment 1 were collected during a data collection period by cutting 18 sub-samples/day to 3cm and pooled periodically to produce two representative samples. Grass samples in Experiment 2 were collected daily during the intake measurement period and otherwise once a week. The grass samples were pooled by week at the end of the experiment. Grass samples in Experiment 3 were collected during the data collection period as two independent sets of 6 samples/day and pooled at the end of the period as two separate samples. Two monthly representative samples of concentrate were collected during the summer in each experiment and pooled afterwards as two samples. The collected grass samples were stored frozen ( 238C) and then oven-dried at 60 8C for analyses. The DM content of the grass was determined by drying the samples at 1058C for 20h. The organic matter (OM) content of the feed was determined by ashing at 600 8C for 12 h, N (Kjeldahl-N) by the AOAC (1990) method, neutral detergent fibre (NDF) according to Robertson and Van Soest (1981) and in vitro OM digestibility by the cellulose method (modification of Friedel and Poppe, 1990). Metabolizable energy was calculated for grass by assessing the energy content of 11.7 MJ/kg digestible OM. The metabolizable energy of the concentrate was assessed according to feed tables (MTT, 2004). 2.4. Statistical analysis The following models were used to analyze the animal production data from the experiments according to the SAS MIXED procedure: Herbage intake and post-grazing sward height data was subjected to analysis of variance:
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Yijk ¼ l þ Bi ðPk Þ þ Dj þ Pk þ Dj Pk þ eijk
73 mm/month during Experiments 1, 2 and 3, respectively. The average daily temperatures were 15.2, 16.0 and 17.1 8C, respectively, for each experiment. The yearly average number of days over 258C was 11 during the study (6, 8 and 12days for Experiments 1, 2 and 3, respectively). The monthly precipitation, varying from 29 to 120 mm, was adequate to maintain grass growth in each year. On the other hand, the precipitation was not so high as to damage the soil surface during any period of the study. The composition of the experimental feeds and the sward characteristics are presented in Table 2. The nutritional value of the concentrates was very similar between the experiments. The herbage pre-grazing mass remained in the range 1400–4600 kg DM/ha throughout the study, averaging 2860 kg DM/ha. The HM was lowest in Experiment 1 due to the early growth stage of the grass compared to Experiments 2 and 3. This was also reflected in the highest grass in vitro OM digestibility and N content in Experiment 1. The pregrazing sward height, pre-grazing herbage mass and NDF content of grass were highest while the N and ME contents of the grass were lowest in Experiment 3. The overall variation in grass ME (10.3–11.7 MJ/kg DM, F 0.21MJ) content was quite small due to intensive rotational grazing. The milk and milk constituent outputs of the three experiments are presented in Table 3. The energycorrected milk (ECM, Sjaunja et al., 1990) response to concentrate supplementation up to 9 kg was 0.84, 0.67 and 0.96 kg ECM/kg concentrate DM for Experiments 1, 2 and 3, respectively. The highest concentrate level (12 kg) was used only in Experiment 3 where the ECM yield responded quadratical-
where l is the overall mean, B i ( P k ) is the random effect of the daily area allocated for the treatment (block) effect nested in period ( P k ), D j is the diet effect, P k is the period effect and e ijk is the residual effect. Milk production data was analysed as: Experiments 1 and 3 Yijkl ¼ l þ Ci þ Pj þ Dk þ Bl þ Dk Bl þ eijkl where l is the overall mean, C i is the random cow effect, P j is the period effect, D k is the diet effect, B l is the block effect and e is the residual effect. Sums of squares were further separated into linear and quadratic contrasts to test the effect of supplementation. Experiment 2 Yijkl ¼ l þ Di þ Pj þ Bk þ Di Pj þ Dj Bk þ eijk where l is the overall mean, D i is the diet effect, P j is the period effect, B k is the block effect and e is the residual effect. The period was used as a repeated measurement. Sums of squares were further separated into linear and quadratic contrasts to test the effect of supplementation. The significance smaller than 0.2 has been reported in the tables.
3. Results Weather conditions did not vary notably during the experimental years. Precipitation averaged 90, 57 and Table 2 Composition of experimental feeds Concentrate
g/kg DM Organic matter NDF N ME (MJ/kg DM) IVOMDa Pre-grazing HM (kg) Pre-grazing SHb (cm) a b
Grass
Experiment 1
Experiment 2
Experiment 3
Experiment 1
Experiment 2
Experiment 3
921 246 26 12.6
925 256 25 12.6
918 279 26 12.6
907 F 10 527 F 20 37 F 2 11.6 F 0.1 80 F 3 2400 F 476 30.3 F 5.4
901 F15 486 F 34 33 F 5 11.3 F 0.4 78 F 3 2700 F 519 29.8 F 6.0
904 F 22 531 F 45 30 F 6 11.2 F 0.2 77 F 3 3070 F 570 34.9 F 6.4
IVOMD, in vitro organic matter digestibility. SH, surface height.
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Table 3 Milk production of cows supplemented with increasing amount of concentrate Concentrate (kg/day) 0 Milk (kg/day)
ECM (g/kg)
Fat yield (g/day)
Protein yield (g/day)
Fat (g/kg)
Protein (g/kg)
Urea (mmol/l)
2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002
3 26.2
28.4 26.0
25.6
27.7 25.2
1025
1101 979
825
904 838
39.2
38.9 38.2
31.6
32 32.5
6.5
6.3 6.7
S.E.M. 6
9
31.7 27.7 31.4 30.3 26.3 30.0 1162 990 1169 1027 896 1017 36.8 36.8 37.3 32.5 32.6 32.6 5.7 5.9 5.4
33.8 30.1 34.0 32.0 28.7 32.5 1208 1089 1268 1093 987 1099 35.8 36.7 37.3 32.4 33.2 32.5 5.2 5.3 5.2
ly ( P b 0.001), showing a slightly negative response between 9 and 12 kg supplementation. The milk fat content decreased with increasing amount of concentrate, but there was variability between the experiments. Supplementation tended to increase ( P = 0.08 in Experiment 1) or had no effect (Experiments 2 and 3) on the milk protein content, whereas the milk urea content decreased linearly ( P b 0.001 in all experiments), on average by 0.19 mmol/kg DM. Experiment 3 included 12 primiparous cows whose milk yields are not presented in Table 3. The milk yield increased linearly ( P b 0.001), being 23.4, 25.2 and 26.2 kg ECM with concentrate supplementation of 4, 7 and 10 kg/day, respectively. Supplementation decreased the milk urea content ( P b 0.001; 6.3, 5.8 and 5.3 mmol/l for concentrate 4, 7 and 10 kg, respectively) and the fat content ( P b 0.01; 39.2, 38.3 and 36.0g/kg milk for concentrate 4, 7 and 10 kg, respectively) and had no significant effect on the milk protein content (average 33.0g/kg). It was possible to test for interaction between period and treatment in Experiment 2 due to the randomized-block design. There was no significant
12
Significance Linear
34.7
32.2
1208
1126
34.9
32.5
4.7
0.70 0.72 0.62 0.73 0.71 0.59 33.7 29.3 29.8 24.8 23.3 17.7 0.76 0.69 0.60 0.35 0.37 0.33 0.20 0.17 0.14
0.001 0.001 0.001 0.001 0.003 0.001 0.001 0.01 0.11 0.001 0.001 0.001 0.001 0.13 0.001 0.08 0.17 0.001 0.001 0.001
Quadratic
0.001
0.001
0.001
0.02
0.03
0.08
interaction in milk or milk protein yield between periods and concentrate treatments, but it was found that the MR in ECM was lowest in period 1 ( P b 0.01) being 0.48 kg/kg compared to responses of 0.82 and 0.71kg/kg in periods 2 and 3, respectively. Supplementation decreased the milk fat content by 2.4g/kg and 2.6g/kg in periods 1 and 3 but had no effect in period 2 (interaction between period and treatment P b 0.01). The live weights of the cows increased during the summer in all three experiments (0.27, 0.35 and 0.43kg/day in Experiments 1, 2 and 3, respectively). The live weights were highest with the highest levels of concentrates ( P b 0.05) in Experiments 1 and 3. There was no statistical difference in live weights between the diets in Experiment 2, but there was concentrate and period interaction ( P b 0.05) such that the live weight gain was highest with the 9 kg supplementation level. The cows consumed the concentrates very well and the average amount of refusals was less than 0.1kg/day during the experiments independent of the concentrate treatment. The measured grass intake in Experiment 2 was 14.2, 11.4 and 11.8 kg DM
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Table 4 Calculated grass intakea and post-grazing sward height of frequently grazed area Concentrate (kg)
Grass intake (kg DM/day)
Post-grazing grass height (cm)
a
2000 2001 2002 2000 2001 2002
S.E.M.
0
3
6
9
16.3
14.9 14.2
8.0
8.7 9.0
13.7 12.1 14.3 8.8 9.8 11.7
12.1 10.8 13.0 9.4 10.1 11.8
12
10.4
12.3
Significance Linear
0.42 0.39 0.31 0.26 0.22 0.27
b0.001 b0.001 b0.001 b0.001 b0.001 b0.085
Quadratic
b0.01 0.057 0.124
Based on ME requirement, according to feed tables (MTT, 2004).
( P b 0.01) for treatments 3, 6 and 9 kg concentrate, respectively. Calculated grass intake (based on energy requirement of MTT, 2004) decreased linearly and the post-grazing SH increased with increasing supplementation (Table 4).
4. Discussion 4.1. Marginal response The concentrate included 10% rapeseed expellers and therefore both the energy and rumen undegradable protein intakes increased with concentrate supplementation. Undegradable protein can be a limiting factor for milk production in grazing cows at least with a high production level (Kolver, 2000; Bargo et al., 2003), and therefore a certain amount of protein concentrate was included in the ingredients of the concentrate. The energy-corrected milk yield increased linearly by an average 0.82 kg/kg and milk yield 0.93 kg/kg concentrate DM up to the 9kg supplementation level. The average MR in ECM was also statistically linear up to 10 kg supplementation with the primiparous cows in Experiment 3. Overall marginal response for multiparous cows was in line with the data from the literature presented by Bargo et al. (2003), in which the average milk response for early and mid lactating cows was 1.0 kg milk/kg concentrate up to 10kg supplementation. Peyraud and Delaby (2001) pointed out that MR depends on the energy balance of the cows. When the amount and/or quality of the basal diet is low compared to the cow’s potential milk production, the energy balance is negative and the response to
concentrate supplementation is high. Peyraud and Delaby (2001) also concluded in their review that, if the energy balance is low due to a very restricted herbage allowance, the substitution rate (SR, kg grass DM/kg increased concentrate DM) is close to zero and increases to 0.6 when sward limitations are minimized. The measured SR was 0.42 in Experiment 2 which indicated that the HA used of 25kg DM was reasonable. The estimated SR was even higher (0.65 kg/kg in Experiment 2) if we use values based on the grass intake calculated on the basis of ME. That the 25kg HA was adequate is also supported by the increasing live weight of the cows. The post-grazing sward height below that recommended (10 cm, Virkaja¨rvi et al., 2002) and the lowest live weight gain during the summer in Experiment 1 indicated that the HA of 21 kg DM was quite low taking into account of the cows’ production level and concentrate supplementation. It would have been possible that cows have used their body reserves to maintain milk production during the three experimental weeks without supplementation, but this was impossible to measure with the design used. When the HA was increased to 25 kg DM (Experiments 2 and 3), the post grazing SH of the frequently harvested areas was near to the recommendation (Virkaja¨rvi et al., 2002). Using a HA above 25 kg DM would decrease the mean MR (see Peyraud and Delaby, 2001) and would lead to poor utilization of the high HA with supplemented cows (Virkaja¨rvi et al., 2002; Dalley et al., 1999). A low herbage mass per hectare limits the intake of grass despite unrestricted availability of area. According to Mayne and Peyraud (1996), the grass intake of cows is restricted when the mass is below 2700 kg DM/ha. Here the average herbage mass
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throughout the experiments was 2700 kg DM/ha and the average pre-grazing sward height was 31.7 cm, which indicated that sward characteristics should not have been a limiting factor for intake and milk production. The timothy-meadow fescue sward height was high compared to the ryegrass widely used in grazing studies, but it is typical of Nordic pastures (Virkaja¨rvi et al., 2003). Also the average in vitro OM digestibility above the 3 cm cutting height, 781 g/kg DM, shows the good energy value of the herbage offered. It has been found in silage studies that MR is low when feeding is based on highly digestible forage (Huhtanen, 1998). The expected MR with silage containing 12.0 MJ/kg DM was 0.42 kg ECM/kg additional concentrate DM according to the discussion in Rinne (2000). However, the ECM response in the current study was higher than this. In the current study the average response of 0.16 kg milk/MJ additional ME intake was also higher than the predicted MR of 0.08 kg milk/additional MJ in the silage studies presented by Woods et al. (2003), or estimated MR of 0.11kg milk/additional MJ presented by Huhtanen (1998). A low average daily concentrate amount can explain only part of the high MR results on pasture compared to conserved forages at the same grass growth stage. Another explanation for the high MR could be that high yielding cows have to work to collect the daily amount of herbage energy and this may limit the intake despite the availability of an ample amount of grass. In theory, the herbage allowance would be ad libitum on pasture, but high yielding cows stop feeding before their energy demand is fully satisfied. Therefore, the energy balance of pasture fed cows is lower and, consequently, the MR is higher than cows fed comparable conserved grass in confinement. In Experiment 2, there was no significant interaction in milk or milk protein response between period and supplementation level. This indicates that grazing conditions were quite stable during the summer. However, a numerically slightly decreased milk response (0.71, 0.82 and 0.82 kg/kg DM for periods 1, 2 and 3, respectively) together with a decreased milk fat content in period 1 resulted in a significantly lowered ECM response in the beginning of the summer. There were no notable differences in HM during the intake measurement periods and the grass
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NDF content was highest in June (501, 452 and 448 g/ kg DM for intake measurement periods 1, 2 and 3, respectively). Thus, the changes in milk fat content are probably a consequence of variation in the effectiveness of grass NDF for maintaining milk fat content (eNDF, Mertens, 1997). 4.2. Interaction between milk production level and MR The energy demand of low-yielding cows can be satisfied even on a solely grass diet and the MR of these cows should be low according to the energy balance-dependent milk response hypothesis. This would explain the low responses to concentrate reported in earlier studies (Ettala et al., 1986; Journet and Demarquilly, 1979, Kellaway and Porta, 1993). This kind of significant interaction between milk production level and concentrate response has been reported in some but not all studies. Horan et al. (2005) reported significant genotype MR interaction such that higher-yielding type Holstein–Friesian cows had a higher MR compared to lower-yielding New Zealand type Holstein–Friesians. Stocdale et al. (1987) reported MR to fall with stall-fed cows from 1.6 to 0.7 kg/kg as lactation progressed. Kristensen and Aes (1999) found no interaction between lactation stage and MR with moderate (average milk yield during grazing season 23.7 kg/day) yielding cows. Kennedy et al. (2003) and Delaby et al. (2001) also reported no significant interaction between pre-experiment milk yield and MR. The interaction between MR and milk production level was quite weak within each experiment in the current data set. Numerically, the ECM responses were usually higher with the high-yielding groups of cows (= expected milk production-based block) within each experiment, but the variation was high and there was no statistically significant ( P N 0.2) block MR interaction in any experiment. This can be partly explained by the relatively small milk yield differences between the blocks within the separate experiments. On the other hand, the effects of milk production level and lactation stage were confounded because one experimental block contained some variation in the terms of days in milk or days pregnant. Thus, the results presented here are a combination of correlated milk production level and lactation stage.
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When MR values from all the experimental blocks were combined in a regression analysis using the year as a random factor, the MR depended significantly on the production level (MR = 0.96 (S.E. 0.46) + 0.062 (S.E. 0.016) ECM, P b 0.01, adj R 2 0.43). The slope estimate obtained is too high compared to earlier studies in which the stage of lactation or milk production level has not been reported to have so high importance in MR (Kristensen and Aes, 1999; Woods et al., 2003; Kennedy et al., 2003). The value of R 2 obtained was quite low and the quantitative generalisation of regression slope contains uncertainty, partly due to confounded lactation stage and production level effects. It could also be speculated that the MR function would be nonlinear if the observations would cover the whole lactation period despite the lack of significance of the quadratic dependency in the current data set. However, low-yielding cows have a lower intake and, therefore, a constant amount of concentrate supplementation leads to a higher percentage of concentrate in the diet of low-yielding cows compared to high-yielding cows. It is reasonable to expect that MR is small in a diet with a high proportion of concentrate (Huhtanen, 1998; Woods et al., 2003). 4.3. Curvilinearity of MR Milk yield varied curvilinearly with supplementation in Experiment 3, showing no increase in ECM yield between 9 and 12 kg supplementation. This curvilinear marginal response agrees with the observations of Valentine et al. (2000) where milk yield (average 27.7 kg/day) did not increase between 10 and 13kg DM supplementation. In the study of Walker et al. (2001), the MR was not significantly different in low-yielding cows (12–22 kg/day) between 7.0 and 10.4kg DM supplementation. Syrja¨la¨ et al. (1996) also reported no significant ECM yield increase between 6 and 9 kg concentrate (23.9 and 24.4kg ECM, for treatments 6 and 9kg concentrate, respectively). These reported results demonstrate that diminishing returns occur earlier with low-yielding cows compared to high-yielding cows. Primiparous cows have less live weight and DMI compared to multiparous cows (NRC, 2001) and therefore a constant amount of supplementation leads
to a higher percentage of concentrate in the total diet. Thus, diminishing returns should occur at a lower level of supplementation with primiparous compared to multiparous cows. However, the MR of the primiparous cows was numerically lower than that of the multiparous cows in Experiment 3 (0.54 kg/kg DM), but it remained statistically linear up to 10 kg supplementation. The primiparous cows in Experiment 2 did not show any milk response between 6 and 9 kg supplementation and the ECM response between the two highest levels was also low (0.38 kg/kg DM). Primiparous cows need both energy and protein to growth resulting lowered milk production capacity compared to multiparous cows. One reason for the negligible MR between 9 and 12 kg supplementation is that increasing the amount of concentrate is known to decrease NDF digestion due to a decreased digestion rate and increased passage rate of NDF (Huhtanen and Jaakkola, 1993; Sairanen et al., 2005). Thus, with highly supplemented diets the marginal ME intake is lower than theoretically estimated (Huhtanen, 1998). Part of the extra energy provided by supplementation is possibly deposited in live weight gain which can be seen in the highest live weights with the highest supplementation level in Experiments 1 and 3. Live weight gain was also highest ( P b 0.05) with the 9 kg concentrate supplementation in Experiment 2. A low proportion of fibre, expressed as physically effective fibre (peNDF, Mertens, 1997), in the diet decreases mastication time and also exposes the cows to health problems such as acidosis, laminitis or displaced abomasum (Mertens, 1997; Bargo et al., 2003). In Experiment 3 there were no recorded shortterm metabolic health problems despite the 11.8kg of concentrate (calculated concentrate proportion 50%) consumed daily on the highest level. The average concentrate proportion was not high, but feeding a high amount of concentrate only during milkings produces a temporary low rumen pH value and may have negative effects on the rumen environment. Even with 12 kg supplementation the concentration of total NDF in the diet (405 g/kg DM) was adequate according to NRC (2001). However, it must be kept in mind that the effectiveness of NDF in both highly digestible pasture and concentrate is lowered to maintain an adequate rumen pH and milk fat content (Mertens, 1997; Kolver and deVeth, 2002).
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5. Conclusions The marginal response to concentrate remained linear (0.82 kg ECM/kg concentrate DM ) up to 9 kg concentrate supplementation with a daily herbage allowance of 21 or 25 kg DM/cow. The energycorrected milk yield did not increase and the milk yield increased only slightly above 9 kg supplementation. The primiparous cows showed numerically lower MR compared to the multiparous cows, but the difference was not statistically proven. There was no interaction between season and milk protein yield, which indicates that it is possible to maintain stable grazing conditions during the main grazing season in Nordic latitudes. The results support to some extent the hypothesis of an increasing marginal milk response to supplementation with an increasing milk production level. References AOAC, 1990. Official Methods of Analysis, 15th edition. Associations of Official Analytical Chemists. Bargo, F., Muller, L.D., Kolver, E.S., Delahoy, J.E., 2003. Invited review: production and digestion of supplemented dairy cows on pasture. J. Dairy Sci. 86, 1 – 42. Bircham, J.S., 1981. Herbage growth and utilization under continuous management. PhD Thesis, University of Edinburgh, 384 pp. Dalley, D.E., Roche, J.R., Grainger, C., Moate, P.J., 1999. Dry matter intake, nutrient selection and milk production of dairy cows grazing rainfed perennial pastures at different herbage allowances in spring. Aust. J. Exp. Agric. 39, 923 – 931. Delaby, L., Peyraud, J.L., Delagarde, R., 2001. Effect of the level of concentrate supplementation, herbage allowance and milk yield at turn-out on the performance of dairy cows in mid lactation at grazing. Anim. Sci. 73, 171 – 181. Ettala, E., Rinne, K., Virtanen, E., Rissanen, H., 1986. Effect of supplemented concentrates on the milk yields of cows grazing good pasture. SO: Annales Agric. Fenn. (Finland) 25, 111 – 125. Friedel, K., Poppe, S., 1990. Ein modifiziertes Zellulase Verfahren als Methode zur Scha¨tzung der Verdaulichkeit von Grobfutter. G-4-Bericht, Wilhelm-Pieck Universita¨ t Rostock, WB Tiererna¨hrung. Horan, B., Dillon, P., Faverdin, P., Delaby, L., Buckley, F., Rath, M., 2005. The interaction of strain of Holstein–Friesian cows and pasture-based feed systems on milk yield, body weight, and body condition score. J. Dairy Sci. 88, 1231 – 1243. Huhtanen, P., 1998. Supply of nutrients and productive responses in dairy cows given diets based on restrictively fermented silage. Agric. Food Sci. Finl. 7, 219 – 250.
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Huhtanen, P., Jaakkola, S., 1993. The effects of forage preservation method and proportion of concentrate on digestion of cell wall carbohydrates and rumen digesta pool size in cattle. Grass Forage Sci. 48, 155 – 165. Journet, M., Demarquilly, C., 1979. Grazing. In: Broster, W.H, Swan, H. (Eds.), Feeding Strategy for the High Yielding Dairy Cow. St. Albans, Canada Publishing Co., UK, pp. 295 – 321. Kellaway, R., Porta, S., 1993. Feeding Concentrates Supplements for Dairy Cows. Dairy Res. Dev. Corp., Australia. Kennedy, J., Dillon, P., Delaby, L., Faverdin, P., Stakelum, G., Rath, M., 2003. Effect of genetic merit and concentrate supplementation on grass intake and milk production with Holstein–Friesian dairy cows. J. Dairy Sci. 86, 610 – 621. Khalili, H., Sairanen, A., 2000. Effect of concentrate type on rumen fermentation and milk production of cows at pasture. Anim. Feed Sci. Technol. 84, 199 – 212. Kolver, E., 2000. Nutrition guidelines for the high producing dairy cow. Proceedings of the Ruakura Dairy Farmers’ Conference, vol. 52, pp. 17 – 28 (http://www.dexcel.co.nz/data/usr/kolver. pdf). Kolver, E.S., deVeth, M.J., 2002. Prediction of ruminal pH from pasture-based diets. J. Dairy Sci. 85, 1255 – 1266. Kristensen, T., Aes, O., 1999. Interaction between level of barley supplement, season and stage of lactation on performance of dairy cows at pasture. Acta Agric. Scand., A Anim. Sci. 49, 1 – 11. Mayne, C.S., Peyraud, J.L., 1996. Recent advances in grassland utilization under grazing and conversation. Grassland and Land Use Systems, 16th EGF Meeting. Gardo, Italy, pp. 347 – 360. Mertens, D.R., 1997. Creating a system for meeting the fiber requirements of dairy cows. J. Dairy Sci. 80, 1464 – 1481. MTT, 2004. Rehutaulukot ja ruokintasuositukset (Feed tables and feeding recommendations). [online]. Jokioinen: Agrifood Research Finland. Published 30.6.2004, [cited 1.10.2005]. Available at: http://www.agronet.fi/rehutaulukot/. URN:NBN: fi-fe20041449. National Research Council, 2001. Nutrient Requirements of Dairy Cattle, 7th rev. ed. Natl. Academic Press, Washington, DC. Peyraud, J.L., Delaby, L., 2001. Ideal concentrate feeds for grazing dairy cows—responses to supplementation in interaction with grazing management and grass quality. In: Garnsworthy, P.C., Wiseman, J. (Eds.), Recent Advances in Animal Nutrition. Nottingham University Press, pp. 203 – 221. Rinne, M., 2000. Influence of timing of the harvest of primary grass growth on herbage quality and subsequent digestion and performance in the ruminant animal. PhD Thesis, University of Helsinki, Finland. Robertson, J.B., Van Soest, P.J., 1981. The detergent system of analysis and its application to human foods. In: James, W.P.T., Theander, O. (Eds.), The Analysis of Dietary Fibre in Food. Marcel Dekker, New York, NY, pp. 123 – 158. Sairanen, A., Khalili, H., Nousiainen, J.I., Ahvenja¨rvi, S., Huhtanen, P., 2005. The effect of concentrate supplementation on nutrient flow to the omasum in dairy cows receiving freshly cut grass. J. Dairy Sci. 88, 1443 – 1453. Sjaunja, L.O., Baevre, L., Junkkarinen, L., Pedersen, J., Seta¨la¨, J., 1990. A Nordic proposal for an energy corrected milk
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(ECM) formula. 27th Session International Committee of Recording and Productivity of Milk Animals. July 2–6, Paris, France, pp. 156 – 157. Stakelum G., 1993. Supplementary feeding and herbage intake of dairy cow. PhD Thesis, National University of Ireland, Dublin. Stocdale, C.R., 1984. Evaluation of techniques for estimating the yield of irrigated pastures intensively grazed by dairy cow: 2. The rising plate meter. Aust. J. Exp. Agric. Anim. Husb. 24, 305 – 311. Stocdale, C.R., Callahan, A., Trigg, T.E., 1987. Feeding high energy supplements to pasture-fed dairy cows. Effects of stage of lactation and level of supplement. Aust. J. Agric. Resour. Econ. 38, 927 – 940. Syrja¨la¨, L., Tesfa, A., Tuori, M., 1996. The effects of concentrate feeding level on milk yield and composition of rotationally grazed dairy cows. In: Parente, G., Frame, J., Orsi, S. (Eds.), Grassland and Land Use Systems. Proceedings of the 16th EGF Meeting. Gardo, Italy. Valentine, S.C., Clayton, E.H., Judson, G.J., Rowe, J.B., 2000. Effect of virginiamycin and sodium bicarbonate on milk production, milk composition and metabolism of dairy cows fed high levels of concentrates. Aust. J. Exp. Agric. 40, 773 – 781.
Virkaja¨rvi, P., Sairanen, A., Nousiainen, J.I., Khalili, H., 2002. Effect of herbage allowance on pasture utilization, regrowth and milk yield of dairy cows in early, mid and late season. Anim. Feed Sci. Technol. 97, 23 – 40. Virkaja¨rvi, P., Sairanen, A., Nousiainen, J.I., 2003. Sward and milk production response to early turnout of dairy cows to pasture in Finland. Agric. Food Sci. Finl. 12, 21 – 34. Walker, G.P., Stockdale, C.R., Wales, W.J., Doyle, P.T., Dellow, D.W., 2001. Effect of level of grain supplementation on milk production responses of dairy cows in mid-late lactation when grazing irrigated pastures high in paspalum (Paspalum dilatatum Poir.). Aust. J. Exp. Agric. 41, 1 – 11. Woods, V.B., Kilpatrick, D.J., Gordon, F.J., 2003. Development of empirical models to describe the response in lactating dairy cattle to changes in nutrient intake as defined in terms of metabolisable energy intake. Livest. Prod. Sci. 80, 229 – 239. Woods, V.B., Ferris, C.P., Gordon, F.J., 2005. The weight and concentration of body components in high genetic merit Holstein–Friesian dairy cows managed on four different grassland-based feeding regimes. Anim. Sci. 81, 179 – 184.
Concentrate supplementation responses of the pasture-fed dairy cow Auvo Sairanen a,*, Hannele Khalili b, Perttu Virkaja¨rvi a a b
MTT Agrifood Research Finland, North Savo Research Station, FIN-71750 Maaninka, Finland MTT Agrifood Research Finland, Animal Production Research, FIN-31600 Jokioinen, Finland Received 13 December 2005; accepted 18 April 2006
Abstract The aim of this study was to investigate the effects of increasing amounts of cereal-based concentrate on milk production. The study consisted of a series of three separate experiments in which cows were grazed in intensive rotation on timothymeadow fescue pasture. In Experiment 1, 28 multiparous Holstein–Friesian cows received 0, 3, 6 and 9 kg concentrate in a cross-over designed trial with a fixed daily herbage allowance of 21 kg DM/cow. The energy-corrected milk yield increased linearly 0.84 kg/kg DM ( P b 0.001), up to the 9kg concentrate level. The milk fat ( P b 0.001) and urea ( P b 0.001) content decreased linearly (0.41 g/kg DM and 0.15 mmol/kg DM, respectively). The milk protein content tended ( P = 0.08) to increase 0.10g/kg DM with increasing supplementation. In Experiment 2, 17 primiparous cows and 28 multiparous cows were used in a randomized-block designed trial with 3, 6 and 9 kg concentrate supplementation and a fixed 25 kg DM herbage allowance. The energy corrected milk yield increased linearly ( P b 0.01) 0.67kg/kg DM, whereas the milk urea content decreased linearly ( P b 0.001) 0.27 mmol/kg DM. The milk protein content increased and the fat content decreased, but these differences were not significant. In Experiment 3, a cross-over design was used to assess the response to concentrate supplementation of 24 multiparous cows (treatments: 6, 9 and 12 kg; fixed herbage allowance 25 kg DM) and 12 primiparous cows (treatments: 4, 7 and 10 kg; herbage allowance N 25 kg DM). The energy-corrected milk yield of the multiparous cows varied quadratically ( P quad b 0.001; 30.0, 32.5 and 32.2kg for 6, 9 and 12 kg supplementation, respectively). Supplementation linearly decreased the urea ( P b 0.001) 0.13mmol/kg DM and fat ( P b 0.001) 0.46 g/kg DM contents. The milk fat content also varied quadratically, showing the lowest content with the 12 kg level ( P quad b 0.05; 37.3, 37.3 and 34.9g/kg for 6, 9 and 12 kg supplementation, respectively). The energy-corrected milk yield of the primiparous cows increased linearly ( P b 0.001) 0.54 kg/kg DM up to 10 kg supplementation, whereas the milk urea ( P b 0.001) and fat contents decreased linearly ( P b 0.01) by 0.19 mmol/kg DM and 0.61g/kg DM, respectively. The results showed that the milk response remained linear up to the 9 kg supplementation level, but the highest level of supplementation resulted in only a marginal increase in milk yield. There was no interaction between season and milk or milk protein yield, which indicates that it is possible to maintain stable grazing conditions during the main grazing season in Nordic
* Corresponding author. Tel.: +358 17 2644823; fax: +358 17 2644851. E-mail address: [email protected] (A. Sairanen). 1871-1413/$ - see front matter D 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2006.04.009
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latitudes. The results support to some extent the hypothesis that the marginal milk response to supplementation increases with increasing milk production. D 2006 Elsevier B.V. All rights reserved. Keywords: Dairy cattle; Grazing; Concentrate feeding
1. Introduction The nutritional value of well-managed grass is high and on good quality pasture a cow’s welfare can be maintained with low levels of concentrate supplementation or even none (Kennedy et al., 2003; Woods et al., 2005). However, supplementary concentrate feeding is given to grazing dairy cows to achieve an economic production level or to ensure performance during periods of weak grass growth. Concentrate supplementation might also decrease loss of body reserves. Additional concentrate feeding increases the total dry matter intake (DMI) and, consequently, the milk yield. The average milk yield response has been 1 kg/kg concentrate (review of Bargo et al., 2003). The use of concentrate is economically justified if the marginal response (MR, kg energy-corrected milk/kg increased concentrate DM) is positive and the cost of the concentrate is lower than the value of milk yield. Pasture is usually the cheapest feed in cow feeding, but the utilization of a high herbage allowance is low (Dalley et al., 1999; Virkaja¨rvi et al., 2002) and cows may not reach their milk production potential without energy supplementation. Supplementation can also be uneconomic if the supply of good quality pasture is sufficient to meet herd demand, and the increased concentrate mostly substitutes grass. The marginal response to concentrate is dependent on many different factors such as herbage allowance (HA, kg DM), herbage quality, concentrate amount, concentrate type, cow’s energy balance, lactation stage and cow’s genetic strain (Stakelum, 1993; Khalili and Sairanen, 2000; Peyraud and Delaby, 2001; Woods et al., 2003; Horan et al., 2005). Thus, determination of the overall MR function is very complicated. The main observation is that the MR diminishes with increasing amount of ME intake (Woods et al., 2003) and increases when the quality or the amount of the basal diet is restricted (Peyraud and Delaby, 2001). Many studies have quantified the
effects of supplementation on the performance of dairy cows, but usually the weakness of these studies has been the low number of supplementation levels used to estimate the response curve. Furthermore, the amount of concentrate has often been low or moderate compared to the production potential of modern cows which make it difficult or impossible to estimate the relevant MR function. This study focuses on evaluating the MR between 0 and 12 kg of supplementation among three experiments using a fixed herbage allowance and cereal grain-based concentrate. The second aim is to clarify whether the MR is dependent on the cow’s milk production or the grazing season.
2. Material and methods 2.1. Pastures, grazing management and herbage mass measurement The study was carried out at MTT Agrifood Research Finland and consisted of a series of three different experiments which were conducted in 2000– 2002. The amount of concentrate and the lactation stage of the cows were the main differing factors among the experiments. The cows were housed in a tie stall and grazed in intensive rotation with front and back fences from the beginning of the grazing season in May. The rotation length was chosen to increase from 2weeks in June to 4 weeks in August due to differences in growth rate of the grass. The target herbage mass (HM) remained between 2000 and 3500kg DM/ha. All the paddocks were grazed five times during the summer and pastures were mechanically clipped to a height of 10cm after the second, third and fourth grazing cycles. The pastures were 1–3-year-old mixed swards established with a mixture of timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) at a ratio of 70:30 (w/w). The pastures were fertilized three times during each growing season. The
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N fertilization rate was 220kg/ha/year and the P and K applications were adjusted according to soil analyses. Fertilizers were applied as three dressings, the first before the grazing season and the other two at intervals of approximately 4 weeks. Prior to commencing the trials, the cows were offered grass silage ad libitum with a target amount of 10% refusal. In addition, the cows were offered 11 kg of an oats–barley–rapeseed expeller (40–40– 20%, w/w) concentrate containing 175 g crude protein/ kg DM. The cows were turned out to pasture at the end of May for 6 h each day until kept outdoors day and night, usually after a 1-week transition period. During this period, the amount of silage was reduced gradually and the cows were adjusted to their concentrate treatments according to the experimental design. In all the experiments, the pre-grazing HM was estimated using a modified method described by Stocdale (1984). In this method, the sward surface height of the daily grazing area was measured by a rising plate meter (3.5 kg/m2). Three representative sampling areas were chosen based on the previously measured mean pressed sward height of the current paddock. In each area, the disk height was recorded and then a frame of 20 50cm was placed on the ground and the herbage inside the frame was cut to a height of 3cm. The samples were oven-dried at 1358C for 5h and weighed. The HM/ha was corrected by multiplying by the mean disk height of the paddock/ disk height of the sample. Sward height was measured with a HFRO type sward stick (Bircham, 1981) using 20–30 measurements per strip (pre grazing) or 40–50 measurements (post grazing). The measurements were divided into three categories: frequently grazed, infrequently grazed or trampled vegetation. Possible null observations, i.e. no hits on living vegetation, were omitted from the data. 2.2. Cows and experimental design 2.2.1. Experiment 1 Twenty-eight Holstein–Friesian multiparous cows (pre-experiment milk yield 34.8 kg/day, F (S.D.) 5.7kg; 105days in milk (DIM), F43 days; live weight (LW) 602 kg, F72 kg) were used in a carry-over-effect balanced cross-over design with the aim of studying the effect of pelleted concentrate supplementation
(0 kg, 3 kg, 6kg and 9 kg/day) on the milk yield. The concentrate consisted mainly of grain and cereal byproducts (Table 1). The cows were divided into six blocks according to parity, pre-experiment milk yield, calving date and days in pregnancy and randomly assigned to concentrate supplementation sequences within the blocks. The experiment comprised three 21-day periods which were divided into a 16-day transition period and a 5-day data collection period. The first period started in the beginning of June. After each period, the cows were changed over to the next concentrate level by 1.5 kg/day steps. The increment of the concentrate supplementation was 1 kg/day when the total daily amount of concentrate exceeded 6 kg. The concentrate and mineral mixture (0.3 kg/day) was offered in the barn as four equal meals at 06:00, 08:00, 16:00 and 17:30 h. The daily herbage allowance per cow was visually estimated to remain in the range 20–30 kg DM/day for days 1–11 of each period when the cows grazed as a single herd. The herbage allowance was measured daily and fixed at 21 kg DM/cow for days 12–21 of each period when the different concentrate level groups grazed separately. 2.2.2. Experiment 2 The study involved 45 Holstein–Friesian cows (17 primiparous and 28 multiparous; pre-experiment milk yield 30.8kg/day, F 7.0kg; 131 DIM, F61 days; LW 588 kg, F57 kg) in a randomized-block design. At the end of the pre-trial period, the cows were blocked in seven blocks according to parameters described in Table 1 Ingredients of concentrates
g/kg Barley Oats Molassed sugar beet pulp Wheat bran Palm kern expeller Rapeseed expeller Molasses Rapeseed oil Vitamin + mineral mixture
Experiment 1
Experiment 2
Experiment 3
400 100 250
400 100 200
382 100 200
100 113 55 2 30
125 100 55 6 32
50 104 55 12 29
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Experiment 1. Three concentrate feed levels (3 kg, 6 kg and 9kg/cow) were randomly assigned to the cows within the blocks. The experiment lasted 80 days and it was divided into three periods; June, July and August which each included an 8-day grass intake measurement period. The cows grazed as a single group, except during the intake measurement periods, with an HA of 25 kg DM/cow. The HA was higher than in Experiment 1, because it was supposed that HA 21kg might not be optimal for milk production with the cows used. The pre-grazing HA was measured daily during the intake measurement periods, otherwise every second day. Grass intake was measured during the last 5 days of each intake period as the difference between the daily pre-grazing and post-grazing herbage mass. The postgrazing HM was measured daily by cutting 2 8 rectangles of 0.1m2 for each concentrate supplementation group. 2.2.3. Experiment 3 The experiment included two separate trials with 12 primiparous (pre-experiment milk yield 27 kg/day, F2.0kg; 161 DIM, F 42 days; LW 499 kg, F27 kg) and 24 multiparous cows (pre-experiment milk yield 34 kg/day, F4.8 kg/day; 115 DIM, F 46 days; LW 590 kg, F58 kg). Three concentrate levels (4 kg, 7 kg and 10 kg/day for primiparous and 6 kg, 9kg and 12 kg/day for multiparous cows) were allocated to the cows in a balanced Latin Squares design. The primiparous cows were blocked in two and multiparous cows in four blocks according to the parameters described in Experiment 1. The cows were randomly assigned to the treatment sequences within the blocks. The length of each of the three periods was 30 days which comprised a 20-day transition and a 10-day data collection period. The multiparous cows grazed in separate groups with a HA of 25 kg DM/day during the data collection period and the primiparous cows grazed as a single herd. During the transition period all the cows grazed as a single group and the HA was visually estimated to be more than 25 kg DM/day. 2.3. Sample collection and analysis The cows were milked indoors at 07:00 and 16:00 h and the milk yields were recorded daily. The average
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values of the data collection periods for each cow were used in statistical analyses in Experiments 1 and 3, whereas averages of monthly values by cow were considered as a repeated measurement in Experiment 2. Milk samples from six consecutive milkings at the end of the data collection period (intake measurement period in Experiment 2) were analysed separately for fat, protein, lactose and urea content using an infrared analyzer (Milcoscan FT6000). The milk composition was determined based on the weighted means of the a.m. and p.m. milkings. Live weight was measured after turnout and at the end of each period. Grass samples for chemical analysis in Experiment 1 were collected during a data collection period by cutting 18 sub-samples/day to 3cm and pooled periodically to produce two representative samples. Grass samples in Experiment 2 were collected daily during the intake measurement period and otherwise once a week. The grass samples were pooled by week at the end of the experiment. Grass samples in Experiment 3 were collected during the data collection period as two independent sets of 6 samples/day and pooled at the end of the period as two separate samples. Two monthly representative samples of concentrate were collected during the summer in each experiment and pooled afterwards as two samples. The collected grass samples were stored frozen ( 238C) and then oven-dried at 60 8C for analyses. The DM content of the grass was determined by drying the samples at 1058C for 20h. The organic matter (OM) content of the feed was determined by ashing at 600 8C for 12 h, N (Kjeldahl-N) by the AOAC (1990) method, neutral detergent fibre (NDF) according to Robertson and Van Soest (1981) and in vitro OM digestibility by the cellulose method (modification of Friedel and Poppe, 1990). Metabolizable energy was calculated for grass by assessing the energy content of 11.7 MJ/kg digestible OM. The metabolizable energy of the concentrate was assessed according to feed tables (MTT, 2004). 2.4. Statistical analysis The following models were used to analyze the animal production data from the experiments according to the SAS MIXED procedure: Herbage intake and post-grazing sward height data was subjected to analysis of variance:
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Yijk ¼ l þ Bi ðPk Þ þ Dj þ Pk þ Dj Pk þ eijk
73 mm/month during Experiments 1, 2 and 3, respectively. The average daily temperatures were 15.2, 16.0 and 17.1 8C, respectively, for each experiment. The yearly average number of days over 258C was 11 during the study (6, 8 and 12days for Experiments 1, 2 and 3, respectively). The monthly precipitation, varying from 29 to 120 mm, was adequate to maintain grass growth in each year. On the other hand, the precipitation was not so high as to damage the soil surface during any period of the study. The composition of the experimental feeds and the sward characteristics are presented in Table 2. The nutritional value of the concentrates was very similar between the experiments. The herbage pre-grazing mass remained in the range 1400–4600 kg DM/ha throughout the study, averaging 2860 kg DM/ha. The HM was lowest in Experiment 1 due to the early growth stage of the grass compared to Experiments 2 and 3. This was also reflected in the highest grass in vitro OM digestibility and N content in Experiment 1. The pregrazing sward height, pre-grazing herbage mass and NDF content of grass were highest while the N and ME contents of the grass were lowest in Experiment 3. The overall variation in grass ME (10.3–11.7 MJ/kg DM, F 0.21MJ) content was quite small due to intensive rotational grazing. The milk and milk constituent outputs of the three experiments are presented in Table 3. The energycorrected milk (ECM, Sjaunja et al., 1990) response to concentrate supplementation up to 9 kg was 0.84, 0.67 and 0.96 kg ECM/kg concentrate DM for Experiments 1, 2 and 3, respectively. The highest concentrate level (12 kg) was used only in Experiment 3 where the ECM yield responded quadratical-
where l is the overall mean, B i ( P k ) is the random effect of the daily area allocated for the treatment (block) effect nested in period ( P k ), D j is the diet effect, P k is the period effect and e ijk is the residual effect. Milk production data was analysed as: Experiments 1 and 3 Yijkl ¼ l þ Ci þ Pj þ Dk þ Bl þ Dk Bl þ eijkl where l is the overall mean, C i is the random cow effect, P j is the period effect, D k is the diet effect, B l is the block effect and e is the residual effect. Sums of squares were further separated into linear and quadratic contrasts to test the effect of supplementation. Experiment 2 Yijkl ¼ l þ Di þ Pj þ Bk þ Di Pj þ Dj Bk þ eijk where l is the overall mean, D i is the diet effect, P j is the period effect, B k is the block effect and e is the residual effect. The period was used as a repeated measurement. Sums of squares were further separated into linear and quadratic contrasts to test the effect of supplementation. The significance smaller than 0.2 has been reported in the tables.
3. Results Weather conditions did not vary notably during the experimental years. Precipitation averaged 90, 57 and Table 2 Composition of experimental feeds Concentrate
g/kg DM Organic matter NDF N ME (MJ/kg DM) IVOMDa Pre-grazing HM (kg) Pre-grazing SHb (cm) a b
Grass
Experiment 1
Experiment 2
Experiment 3
Experiment 1
Experiment 2
Experiment 3
921 246 26 12.6
925 256 25 12.6
918 279 26 12.6
907 F 10 527 F 20 37 F 2 11.6 F 0.1 80 F 3 2400 F 476 30.3 F 5.4
901 F15 486 F 34 33 F 5 11.3 F 0.4 78 F 3 2700 F 519 29.8 F 6.0
904 F 22 531 F 45 30 F 6 11.2 F 0.2 77 F 3 3070 F 570 34.9 F 6.4
IVOMD, in vitro organic matter digestibility. SH, surface height.
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Table 3 Milk production of cows supplemented with increasing amount of concentrate Concentrate (kg/day) 0 Milk (kg/day)
ECM (g/kg)
Fat yield (g/day)
Protein yield (g/day)
Fat (g/kg)
Protein (g/kg)
Urea (mmol/l)
2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002 2000 2001 2002
3 26.2
28.4 26.0
25.6
27.7 25.2
1025
1101 979
825
904 838
39.2
38.9 38.2
31.6
32 32.5
6.5
6.3 6.7
S.E.M. 6
9
31.7 27.7 31.4 30.3 26.3 30.0 1162 990 1169 1027 896 1017 36.8 36.8 37.3 32.5 32.6 32.6 5.7 5.9 5.4
33.8 30.1 34.0 32.0 28.7 32.5 1208 1089 1268 1093 987 1099 35.8 36.7 37.3 32.4 33.2 32.5 5.2 5.3 5.2
ly ( P b 0.001), showing a slightly negative response between 9 and 12 kg supplementation. The milk fat content decreased with increasing amount of concentrate, but there was variability between the experiments. Supplementation tended to increase ( P = 0.08 in Experiment 1) or had no effect (Experiments 2 and 3) on the milk protein content, whereas the milk urea content decreased linearly ( P b 0.001 in all experiments), on average by 0.19 mmol/kg DM. Experiment 3 included 12 primiparous cows whose milk yields are not presented in Table 3. The milk yield increased linearly ( P b 0.001), being 23.4, 25.2 and 26.2 kg ECM with concentrate supplementation of 4, 7 and 10 kg/day, respectively. Supplementation decreased the milk urea content ( P b 0.001; 6.3, 5.8 and 5.3 mmol/l for concentrate 4, 7 and 10 kg, respectively) and the fat content ( P b 0.01; 39.2, 38.3 and 36.0g/kg milk for concentrate 4, 7 and 10 kg, respectively) and had no significant effect on the milk protein content (average 33.0g/kg). It was possible to test for interaction between period and treatment in Experiment 2 due to the randomized-block design. There was no significant
12
Significance Linear
34.7
32.2
1208
1126
34.9
32.5
4.7
0.70 0.72 0.62 0.73 0.71 0.59 33.7 29.3 29.8 24.8 23.3 17.7 0.76 0.69 0.60 0.35 0.37 0.33 0.20 0.17 0.14
0.001 0.001 0.001 0.001 0.003 0.001 0.001 0.01 0.11 0.001 0.001 0.001 0.001 0.13 0.001 0.08 0.17 0.001 0.001 0.001
Quadratic
0.001
0.001
0.001
0.02
0.03
0.08
interaction in milk or milk protein yield between periods and concentrate treatments, but it was found that the MR in ECM was lowest in period 1 ( P b 0.01) being 0.48 kg/kg compared to responses of 0.82 and 0.71kg/kg in periods 2 and 3, respectively. Supplementation decreased the milk fat content by 2.4g/kg and 2.6g/kg in periods 1 and 3 but had no effect in period 2 (interaction between period and treatment P b 0.01). The live weights of the cows increased during the summer in all three experiments (0.27, 0.35 and 0.43kg/day in Experiments 1, 2 and 3, respectively). The live weights were highest with the highest levels of concentrates ( P b 0.05) in Experiments 1 and 3. There was no statistical difference in live weights between the diets in Experiment 2, but there was concentrate and period interaction ( P b 0.05) such that the live weight gain was highest with the 9 kg supplementation level. The cows consumed the concentrates very well and the average amount of refusals was less than 0.1kg/day during the experiments independent of the concentrate treatment. The measured grass intake in Experiment 2 was 14.2, 11.4 and 11.8 kg DM
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Table 4 Calculated grass intakea and post-grazing sward height of frequently grazed area Concentrate (kg)
Grass intake (kg DM/day)
Post-grazing grass height (cm)
a
2000 2001 2002 2000 2001 2002
S.E.M.
0
3
6
9
16.3
14.9 14.2
8.0
8.7 9.0
13.7 12.1 14.3 8.8 9.8 11.7
12.1 10.8 13.0 9.4 10.1 11.8
12
10.4
12.3
Significance Linear
0.42 0.39 0.31 0.26 0.22 0.27
b0.001 b0.001 b0.001 b0.001 b0.001 b0.085
Quadratic
b0.01 0.057 0.124
Based on ME requirement, according to feed tables (MTT, 2004).
( P b 0.01) for treatments 3, 6 and 9 kg concentrate, respectively. Calculated grass intake (based on energy requirement of MTT, 2004) decreased linearly and the post-grazing SH increased with increasing supplementation (Table 4).
4. Discussion 4.1. Marginal response The concentrate included 10% rapeseed expellers and therefore both the energy and rumen undegradable protein intakes increased with concentrate supplementation. Undegradable protein can be a limiting factor for milk production in grazing cows at least with a high production level (Kolver, 2000; Bargo et al., 2003), and therefore a certain amount of protein concentrate was included in the ingredients of the concentrate. The energy-corrected milk yield increased linearly by an average 0.82 kg/kg and milk yield 0.93 kg/kg concentrate DM up to the 9kg supplementation level. The average MR in ECM was also statistically linear up to 10 kg supplementation with the primiparous cows in Experiment 3. Overall marginal response for multiparous cows was in line with the data from the literature presented by Bargo et al. (2003), in which the average milk response for early and mid lactating cows was 1.0 kg milk/kg concentrate up to 10kg supplementation. Peyraud and Delaby (2001) pointed out that MR depends on the energy balance of the cows. When the amount and/or quality of the basal diet is low compared to the cow’s potential milk production, the energy balance is negative and the response to
concentrate supplementation is high. Peyraud and Delaby (2001) also concluded in their review that, if the energy balance is low due to a very restricted herbage allowance, the substitution rate (SR, kg grass DM/kg increased concentrate DM) is close to zero and increases to 0.6 when sward limitations are minimized. The measured SR was 0.42 in Experiment 2 which indicated that the HA used of 25kg DM was reasonable. The estimated SR was even higher (0.65 kg/kg in Experiment 2) if we use values based on the grass intake calculated on the basis of ME. That the 25kg HA was adequate is also supported by the increasing live weight of the cows. The post-grazing sward height below that recommended (10 cm, Virkaja¨rvi et al., 2002) and the lowest live weight gain during the summer in Experiment 1 indicated that the HA of 21 kg DM was quite low taking into account of the cows’ production level and concentrate supplementation. It would have been possible that cows have used their body reserves to maintain milk production during the three experimental weeks without supplementation, but this was impossible to measure with the design used. When the HA was increased to 25 kg DM (Experiments 2 and 3), the post grazing SH of the frequently harvested areas was near to the recommendation (Virkaja¨rvi et al., 2002). Using a HA above 25 kg DM would decrease the mean MR (see Peyraud and Delaby, 2001) and would lead to poor utilization of the high HA with supplemented cows (Virkaja¨rvi et al., 2002; Dalley et al., 1999). A low herbage mass per hectare limits the intake of grass despite unrestricted availability of area. According to Mayne and Peyraud (1996), the grass intake of cows is restricted when the mass is below 2700 kg DM/ha. Here the average herbage mass
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throughout the experiments was 2700 kg DM/ha and the average pre-grazing sward height was 31.7 cm, which indicated that sward characteristics should not have been a limiting factor for intake and milk production. The timothy-meadow fescue sward height was high compared to the ryegrass widely used in grazing studies, but it is typical of Nordic pastures (Virkaja¨rvi et al., 2003). Also the average in vitro OM digestibility above the 3 cm cutting height, 781 g/kg DM, shows the good energy value of the herbage offered. It has been found in silage studies that MR is low when feeding is based on highly digestible forage (Huhtanen, 1998). The expected MR with silage containing 12.0 MJ/kg DM was 0.42 kg ECM/kg additional concentrate DM according to the discussion in Rinne (2000). However, the ECM response in the current study was higher than this. In the current study the average response of 0.16 kg milk/MJ additional ME intake was also higher than the predicted MR of 0.08 kg milk/additional MJ in the silage studies presented by Woods et al. (2003), or estimated MR of 0.11kg milk/additional MJ presented by Huhtanen (1998). A low average daily concentrate amount can explain only part of the high MR results on pasture compared to conserved forages at the same grass growth stage. Another explanation for the high MR could be that high yielding cows have to work to collect the daily amount of herbage energy and this may limit the intake despite the availability of an ample amount of grass. In theory, the herbage allowance would be ad libitum on pasture, but high yielding cows stop feeding before their energy demand is fully satisfied. Therefore, the energy balance of pasture fed cows is lower and, consequently, the MR is higher than cows fed comparable conserved grass in confinement. In Experiment 2, there was no significant interaction in milk or milk protein response between period and supplementation level. This indicates that grazing conditions were quite stable during the summer. However, a numerically slightly decreased milk response (0.71, 0.82 and 0.82 kg/kg DM for periods 1, 2 and 3, respectively) together with a decreased milk fat content in period 1 resulted in a significantly lowered ECM response in the beginning of the summer. There were no notable differences in HM during the intake measurement periods and the grass
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NDF content was highest in June (501, 452 and 448 g/ kg DM for intake measurement periods 1, 2 and 3, respectively). Thus, the changes in milk fat content are probably a consequence of variation in the effectiveness of grass NDF for maintaining milk fat content (eNDF, Mertens, 1997). 4.2. Interaction between milk production level and MR The energy demand of low-yielding cows can be satisfied even on a solely grass diet and the MR of these cows should be low according to the energy balance-dependent milk response hypothesis. This would explain the low responses to concentrate reported in earlier studies (Ettala et al., 1986; Journet and Demarquilly, 1979, Kellaway and Porta, 1993). This kind of significant interaction between milk production level and concentrate response has been reported in some but not all studies. Horan et al. (2005) reported significant genotype MR interaction such that higher-yielding type Holstein–Friesian cows had a higher MR compared to lower-yielding New Zealand type Holstein–Friesians. Stocdale et al. (1987) reported MR to fall with stall-fed cows from 1.6 to 0.7 kg/kg as lactation progressed. Kristensen and Aes (1999) found no interaction between lactation stage and MR with moderate (average milk yield during grazing season 23.7 kg/day) yielding cows. Kennedy et al. (2003) and Delaby et al. (2001) also reported no significant interaction between pre-experiment milk yield and MR. The interaction between MR and milk production level was quite weak within each experiment in the current data set. Numerically, the ECM responses were usually higher with the high-yielding groups of cows (= expected milk production-based block) within each experiment, but the variation was high and there was no statistically significant ( P N 0.2) block MR interaction in any experiment. This can be partly explained by the relatively small milk yield differences between the blocks within the separate experiments. On the other hand, the effects of milk production level and lactation stage were confounded because one experimental block contained some variation in the terms of days in milk or days pregnant. Thus, the results presented here are a combination of correlated milk production level and lactation stage.
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When MR values from all the experimental blocks were combined in a regression analysis using the year as a random factor, the MR depended significantly on the production level (MR = 0.96 (S.E. 0.46) + 0.062 (S.E. 0.016) ECM, P b 0.01, adj R 2 0.43). The slope estimate obtained is too high compared to earlier studies in which the stage of lactation or milk production level has not been reported to have so high importance in MR (Kristensen and Aes, 1999; Woods et al., 2003; Kennedy et al., 2003). The value of R 2 obtained was quite low and the quantitative generalisation of regression slope contains uncertainty, partly due to confounded lactation stage and production level effects. It could also be speculated that the MR function would be nonlinear if the observations would cover the whole lactation period despite the lack of significance of the quadratic dependency in the current data set. However, low-yielding cows have a lower intake and, therefore, a constant amount of concentrate supplementation leads to a higher percentage of concentrate in the diet of low-yielding cows compared to high-yielding cows. It is reasonable to expect that MR is small in a diet with a high proportion of concentrate (Huhtanen, 1998; Woods et al., 2003). 4.3. Curvilinearity of MR Milk yield varied curvilinearly with supplementation in Experiment 3, showing no increase in ECM yield between 9 and 12 kg supplementation. This curvilinear marginal response agrees with the observations of Valentine et al. (2000) where milk yield (average 27.7 kg/day) did not increase between 10 and 13kg DM supplementation. In the study of Walker et al. (2001), the MR was not significantly different in low-yielding cows (12–22 kg/day) between 7.0 and 10.4kg DM supplementation. Syrja¨la¨ et al. (1996) also reported no significant ECM yield increase between 6 and 9 kg concentrate (23.9 and 24.4kg ECM, for treatments 6 and 9kg concentrate, respectively). These reported results demonstrate that diminishing returns occur earlier with low-yielding cows compared to high-yielding cows. Primiparous cows have less live weight and DMI compared to multiparous cows (NRC, 2001) and therefore a constant amount of supplementation leads
to a higher percentage of concentrate in the total diet. Thus, diminishing returns should occur at a lower level of supplementation with primiparous compared to multiparous cows. However, the MR of the primiparous cows was numerically lower than that of the multiparous cows in Experiment 3 (0.54 kg/kg DM), but it remained statistically linear up to 10 kg supplementation. The primiparous cows in Experiment 2 did not show any milk response between 6 and 9 kg supplementation and the ECM response between the two highest levels was also low (0.38 kg/kg DM). Primiparous cows need both energy and protein to growth resulting lowered milk production capacity compared to multiparous cows. One reason for the negligible MR between 9 and 12 kg supplementation is that increasing the amount of concentrate is known to decrease NDF digestion due to a decreased digestion rate and increased passage rate of NDF (Huhtanen and Jaakkola, 1993; Sairanen et al., 2005). Thus, with highly supplemented diets the marginal ME intake is lower than theoretically estimated (Huhtanen, 1998). Part of the extra energy provided by supplementation is possibly deposited in live weight gain which can be seen in the highest live weights with the highest supplementation level in Experiments 1 and 3. Live weight gain was also highest ( P b 0.05) with the 9 kg concentrate supplementation in Experiment 2. A low proportion of fibre, expressed as physically effective fibre (peNDF, Mertens, 1997), in the diet decreases mastication time and also exposes the cows to health problems such as acidosis, laminitis or displaced abomasum (Mertens, 1997; Bargo et al., 2003). In Experiment 3 there were no recorded shortterm metabolic health problems despite the 11.8kg of concentrate (calculated concentrate proportion 50%) consumed daily on the highest level. The average concentrate proportion was not high, but feeding a high amount of concentrate only during milkings produces a temporary low rumen pH value and may have negative effects on the rumen environment. Even with 12 kg supplementation the concentration of total NDF in the diet (405 g/kg DM) was adequate according to NRC (2001). However, it must be kept in mind that the effectiveness of NDF in both highly digestible pasture and concentrate is lowered to maintain an adequate rumen pH and milk fat content (Mertens, 1997; Kolver and deVeth, 2002).
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5. Conclusions The marginal response to concentrate remained linear (0.82 kg ECM/kg concentrate DM ) up to 9 kg concentrate supplementation with a daily herbage allowance of 21 or 25 kg DM/cow. The energycorrected milk yield did not increase and the milk yield increased only slightly above 9 kg supplementation. The primiparous cows showed numerically lower MR compared to the multiparous cows, but the difference was not statistically proven. There was no interaction between season and milk protein yield, which indicates that it is possible to maintain stable grazing conditions during the main grazing season in Nordic latitudes. The results support to some extent the hypothesis of an increasing marginal milk response to supplementation with an increasing milk production level. References AOAC, 1990. Official Methods of Analysis, 15th edition. Associations of Official Analytical Chemists. Bargo, F., Muller, L.D., Kolver, E.S., Delahoy, J.E., 2003. Invited review: production and digestion of supplemented dairy cows on pasture. J. Dairy Sci. 86, 1 – 42. Bircham, J.S., 1981. Herbage growth and utilization under continuous management. PhD Thesis, University of Edinburgh, 384 pp. Dalley, D.E., Roche, J.R., Grainger, C., Moate, P.J., 1999. Dry matter intake, nutrient selection and milk production of dairy cows grazing rainfed perennial pastures at different herbage allowances in spring. Aust. J. Exp. Agric. 39, 923 – 931. Delaby, L., Peyraud, J.L., Delagarde, R., 2001. Effect of the level of concentrate supplementation, herbage allowance and milk yield at turn-out on the performance of dairy cows in mid lactation at grazing. Anim. Sci. 73, 171 – 181. Ettala, E., Rinne, K., Virtanen, E., Rissanen, H., 1986. Effect of supplemented concentrates on the milk yields of cows grazing good pasture. SO: Annales Agric. Fenn. (Finland) 25, 111 – 125. Friedel, K., Poppe, S., 1990. Ein modifiziertes Zellulase Verfahren als Methode zur Scha¨tzung der Verdaulichkeit von Grobfutter. G-4-Bericht, Wilhelm-Pieck Universita¨ t Rostock, WB Tiererna¨hrung. Horan, B., Dillon, P., Faverdin, P., Delaby, L., Buckley, F., Rath, M., 2005. The interaction of strain of Holstein–Friesian cows and pasture-based feed systems on milk yield, body weight, and body condition score. J. Dairy Sci. 88, 1231 – 1243. Huhtanen, P., 1998. Supply of nutrients and productive responses in dairy cows given diets based on restrictively fermented silage. Agric. Food Sci. Finl. 7, 219 – 250.
301
Huhtanen, P., Jaakkola, S., 1993. The effects of forage preservation method and proportion of concentrate on digestion of cell wall carbohydrates and rumen digesta pool size in cattle. Grass Forage Sci. 48, 155 – 165. Journet, M., Demarquilly, C., 1979. Grazing. In: Broster, W.H, Swan, H. (Eds.), Feeding Strategy for the High Yielding Dairy Cow. St. Albans, Canada Publishing Co., UK, pp. 295 – 321. Kellaway, R., Porta, S., 1993. Feeding Concentrates Supplements for Dairy Cows. Dairy Res. Dev. Corp., Australia. Kennedy, J., Dillon, P., Delaby, L., Faverdin, P., Stakelum, G., Rath, M., 2003. Effect of genetic merit and concentrate supplementation on grass intake and milk production with Holstein–Friesian dairy cows. J. Dairy Sci. 86, 610 – 621. Khalili, H., Sairanen, A., 2000. Effect of concentrate type on rumen fermentation and milk production of cows at pasture. Anim. Feed Sci. Technol. 84, 199 – 212. Kolver, E., 2000. Nutrition guidelines for the high producing dairy cow. Proceedings of the Ruakura Dairy Farmers’ Conference, vol. 52, pp. 17 – 28 (http://www.dexcel.co.nz/data/usr/kolver. pdf). Kolver, E.S., deVeth, M.J., 2002. Prediction of ruminal pH from pasture-based diets. J. Dairy Sci. 85, 1255 – 1266. Kristensen, T., Aes, O., 1999. Interaction between level of barley supplement, season and stage of lactation on performance of dairy cows at pasture. Acta Agric. Scand., A Anim. Sci. 49, 1 – 11. Mayne, C.S., Peyraud, J.L., 1996. Recent advances in grassland utilization under grazing and conversation. Grassland and Land Use Systems, 16th EGF Meeting. Gardo, Italy, pp. 347 – 360. Mertens, D.R., 1997. Creating a system for meeting the fiber requirements of dairy cows. J. Dairy Sci. 80, 1464 – 1481. MTT, 2004. Rehutaulukot ja ruokintasuositukset (Feed tables and feeding recommendations). [online]. Jokioinen: Agrifood Research Finland. Published 30.6.2004, [cited 1.10.2005]. Available at: http://www.agronet.fi/rehutaulukot/. URN:NBN: fi-fe20041449. National Research Council, 2001. Nutrient Requirements of Dairy Cattle, 7th rev. ed. Natl. Academic Press, Washington, DC. Peyraud, J.L., Delaby, L., 2001. Ideal concentrate feeds for grazing dairy cows—responses to supplementation in interaction with grazing management and grass quality. In: Garnsworthy, P.C., Wiseman, J. (Eds.), Recent Advances in Animal Nutrition. Nottingham University Press, pp. 203 – 221. Rinne, M., 2000. Influence of timing of the harvest of primary grass growth on herbage quality and subsequent digestion and performance in the ruminant animal. PhD Thesis, University of Helsinki, Finland. Robertson, J.B., Van Soest, P.J., 1981. The detergent system of analysis and its application to human foods. In: James, W.P.T., Theander, O. (Eds.), The Analysis of Dietary Fibre in Food. Marcel Dekker, New York, NY, pp. 123 – 158. Sairanen, A., Khalili, H., Nousiainen, J.I., Ahvenja¨rvi, S., Huhtanen, P., 2005. The effect of concentrate supplementation on nutrient flow to the omasum in dairy cows receiving freshly cut grass. J. Dairy Sci. 88, 1443 – 1453. Sjaunja, L.O., Baevre, L., Junkkarinen, L., Pedersen, J., Seta¨la¨, J., 1990. A Nordic proposal for an energy corrected milk
302
A. Sairanen et al. / Livestock Science 104 (2006) 292–302
(ECM) formula. 27th Session International Committee of Recording and Productivity of Milk Animals. July 2–6, Paris, France, pp. 156 – 157. Stakelum G., 1993. Supplementary feeding and herbage intake of dairy cow. PhD Thesis, National University of Ireland, Dublin. Stocdale, C.R., 1984. Evaluation of techniques for estimating the yield of irrigated pastures intensively grazed by dairy cow: 2. The rising plate meter. Aust. J. Exp. Agric. Anim. Husb. 24, 305 – 311. Stocdale, C.R., Callahan, A., Trigg, T.E., 1987. Feeding high energy supplements to pasture-fed dairy cows. Effects of stage of lactation and level of supplement. Aust. J. Agric. Resour. Econ. 38, 927 – 940. Syrja¨la¨, L., Tesfa, A., Tuori, M., 1996. The effects of concentrate feeding level on milk yield and composition of rotationally grazed dairy cows. In: Parente, G., Frame, J., Orsi, S. (Eds.), Grassland and Land Use Systems. Proceedings of the 16th EGF Meeting. Gardo, Italy. Valentine, S.C., Clayton, E.H., Judson, G.J., Rowe, J.B., 2000. Effect of virginiamycin and sodium bicarbonate on milk production, milk composition and metabolism of dairy cows fed high levels of concentrates. Aust. J. Exp. Agric. 40, 773 – 781.
Virkaja¨rvi, P., Sairanen, A., Nousiainen, J.I., Khalili, H., 2002. Effect of herbage allowance on pasture utilization, regrowth and milk yield of dairy cows in early, mid and late season. Anim. Feed Sci. Technol. 97, 23 – 40. Virkaja¨rvi, P., Sairanen, A., Nousiainen, J.I., 2003. Sward and milk production response to early turnout of dairy cows to pasture in Finland. Agric. Food Sci. Finl. 12, 21 – 34. Walker, G.P., Stockdale, C.R., Wales, W.J., Doyle, P.T., Dellow, D.W., 2001. Effect of level of grain supplementation on milk production responses of dairy cows in mid-late lactation when grazing irrigated pastures high in paspalum (Paspalum dilatatum Poir.). Aust. J. Exp. Agric. 41, 1 – 11. Woods, V.B., Kilpatrick, D.J., Gordon, F.J., 2003. Development of empirical models to describe the response in lactating dairy cattle to changes in nutrient intake as defined in terms of metabolisable energy intake. Livest. Prod. Sci. 80, 229 – 239. Woods, V.B., Ferris, C.P., Gordon, F.J., 2005. The weight and concentration of body components in high genetic merit Holstein–Friesian dairy cows managed on four different grassland-based feeding regimes. Anim. Sci. 81, 179 – 184.