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Effects of different transition diets on energy balance, blood metabolites and reproductive performance in dairy cows
Livestock Production Science 84 (2003) 195 – 206 www.elsevier.com/locate/livprodsci
Effects of different transition diets on energy balance, blood metabolites and reproductive performance in dairy cows S. McNamara a,b, J.J. Murphy a,*, M. Rath b, F.P. O’Mara b b
a Teagasc, Dairy Production Research Centre, Moorepark, Fermoy, Co. Cork, Ireland Department of Animal Science and Production, University College Dublin, Belfield, Dublin 4, Ireland
Received 26 June 2002; received in revised form 26 February 2003; accepted 24 March 2003
Abstract The objective of this study was to evaluate the effect of diets differing in energy density (ED) in the last 4 weeks of the dry period and in the first 8 weeks of lactation on energy balance (EB), blood metabolites and reproductive performance. Three diets (grass silage:straw 75:25 on a dry matter basis (SS), grass silage (S) and grass silage+3 kg/day of concentrates (C)) precalving and two diets (4 kg (LC) or 8 kg/day of concentrates (HC)+grass silage ad libitum) post-calving were combined in a 32 factorial design. Sixty second-lactation Holstein – Friesian cows were blocked according to expected calving date and body condition score into groups of six and were then allocated at random to the treatments. Individual feeding started on average 34 days prior to parturition and measurements were made until the end of the 8th week of lactation. Net energy (NE) intake increased (5.6, 6.5 and 9.0 UFL/cow per day; (standard error of the difference (S.E.D.)=0.22) and EB improved pre-calving as the ED of the diet increased. Post-calving, milk energy output was significantly different between pre-calving treatments at 10.5, 11.6 and 12.7 UFL/day (S.E.D.=0.48) for SS, S and C respectively. Cows on the highest ED diet pre-calving (C) had a greater degree of negative energy balance (NEB) than cows on the lowest ED diet pre-calving (SS) for 7 of the first 8 weeks of lactation. At calving, cows on C had a lower plasma urea concentration than those on S and cows on SS had a lower plasma bile acid concentration than those on S. At week 2 post-calving, C had a higher plasma h-hydroxybutyrate concentration than SS and a higher plasma protein concentration than SS or S. Post-calving, cows receiving HC had higher NE intakes averaged over the first 8 weeks of lactation and lower NEB in each of the first 8 weeks of lactation than those on LC. Plasma glucose and bile acid concentrations were higher on HC compared to LC at week 2 post-calving. Plasma urea concentrations were lower (P < 0:05) on HC compared to LC. D 2003 Elsevier B.V. All rights reserved. Keywords: Dairy cattle; Negative energy balance; Reproductive performance; Dry cow; Lactation; Blood metabolites
1. Introduction In modern agriculture, genetic selection for intense production has resulted in animals that produce food * Corresponding author. Tel.: +353-25-42-222; fax: +353-2542-340. E-mail address: [email protected] (J.J. Murphy). 0301-6226/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0301-6226(03)00093-9
for mankind at a rate beyond the capability of their inherent metabolic machinery (Patton and Poley, 1996). This has led to a situation with the dairy cow where she has difficulty in consuming enough energy to meet her requirements for maintenance and milk production, especially in early lactation. In the last month of pregnancy the energy requirements of the dairy cow increase by 23% to support
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foetal and gravid uterus growth (Moe and Tyrrell, 1972). From 1 week prior to parturition, to 1 day before calving, mammary uptake of glucose increases by 400%, acetate uptake by 180% and blood flow increases by 200% (Bell, 1995). To compound the difficulty of increased energy requirements close to calving, dry matter intake (DMI) starts to decline approximately 3 weeks before parturition and reduces dramatically in the last 7 days. The level of decline has been as high as 30% (Bertics et al., 1992; Chandler, 1995; Grummer, 1995). Increasing the energy concentration of the diet precalving has increased voluntary intake and consequently energy intake, increased body weight gain, reduced the mobilisation of adipose tissue as parturition approaches and lowered plasma non-esterified fatty acid (NEFA) concentrations (Bertics et al., 1992; Minor et al., 1998; Dann et al., 1999; Vandehaar et al., 1999; Dewhurst et al., 2000). The rise in plasma NEFA around the time of parturition is partly due to hormonal changes and stress associated with pregnancy and reduced DMI. The importance of postpartum energy balance (EB) on the recommencement of normal ovarian cycles in high producing dairy cows has been recognised (Butler and Smith, 1989). The degree of negative energy balance (NEB) in the early postpartum period has been correlated with both the level of milk production and the number of days to first ovulation (Butler et al., 1981; Ducker et al., 1985). Bauman et al., (1988), Dunshea et al., (1989) and Canfield and Butler (1990) found a high correlation between NEFA and EB. High NEFA concentrations reflect a degree of under-nutrition and more severe NEB (Topps and Thompson, 1984). The quality of the pre-calving diet is often neglected on dairy farms and research on pre-calving nutrition in high grass silage systems is limited. There are little data with grass silage based diets on the effect of increasing energy density (ED) of the diet in the pre-calving period on EB in early lactation and reproductive performance. The objective of this study was to determine the effects of offering diets differing in ED both pre- and postpartum on EB around calving, blood metabolite concentrations and reproductive performance of Irish bred Holstein – Friesian dairy cows.
2. Materials and methods 2.1. Treatments Sixty spring-calving Holstein – Friesian dairy cows, calving for the second time, were blocked and assigned to treatments 4 weeks before expected calving dates as described by McNamara et al. (2003). The treatments were: 1. Grass silage/barley straw mixture on a 75:25 dry matter basis offered ad libitum (SS) pre-calving, with ad libitum grass silage and 4 kg/cow per day of concentrate post-calving (LC). 2. SS pre-calving with ad libitum grass silage and 8 kg/cow per day of concentrate post-calving (HC). 3. Grass silage offered ad libitum (S) pre-calving with LC post-calving. 4. S pre-calving with HC post-calving. 5. Grass silage offered ad libitum plus 3 kg/cow per day of concentrate (C) pre-calving with LC postcalving. 6. C pre-calving with HC post-calving. The treatments were imposed from, on average, 34 days before actual calving day. The feeding and management of the cows were as described by McNamara et al. (2003). 2.2. Measurements Milk yield (kg) was recorded on a daily basis at both the morning and the evening milking. Milk fat, protein and lactose concentrations were determined once weekly on successive morning and evening milk samples. These data in conjunction with the respective morning and evening milk yields were used to calculate a daily composite fat, protein and lactose concentration. Liveweight (LW) (kg) was measured weekly. The dry cows were weighed before feeding in the morning and the lactating cows were weighed after morning milking. DMI was measured on a daily basis. Reproductive performance of the cows was recorded. Oestrus was detected by thrice daily observation with the aid of tail paint. First observed heat post-calving was recorded for all cows prior to the start of the breeding season. First service (cows were bred at the first heat after April 22, which is typical
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for seasonal spring calving herds) was the first time cows were bred and conception was the first positive scan examined by ultrasonography, using a 5-MHz rectal transducer (Aloka SSD-500V, Japan), which corresponded to a service date. Pregnancy examinations were carried out by ultrasound at 30 –40 days post insemination and 1 month after the end of the breeding season. This gave the following fertility measurements: calving to first service, calving to conception interval, services per conception, pregnancy rate and infertile rate. The breeding season lasted 13 weeks. All cows were served with semen from the same bull and inseminated by one technician to eliminate any variation in fertility due to either different bulls or inseminators. Blood samples were taken from all cows within 12 h of parturition, and at 2 and 8 weeks post-calving. All blood samples were taken from the coccygeal vessels in the morning before feeding. At the time of blood sampling, samples were collected into two different vacutainers, one containing lithium heparin and the other containing fluoride oxalate as anticoagulants. The samples were immediately placed on ice packs and centrifuged within 30 min of sampling. Samples were centrifuged at 1800 g at 0 jC for 10 min. The plasma was decanted into screw-capped tubes, frozen, and stored at 20 jC until analysis. All blood analysis was carried out using appropriate kits and an ABX Mira autoanalyzer (ABX Mira, Cedex 4, France). The metabolites analysed were glucose, NEFA, BHB, urea, protein and bile acids. Glucose was determined in fluoride oxalate plasma and the other analyses were performed on lithium heparin plasma. Laboratory analysis of feedstuffs and milk composition was carried out as described by McNamara et al. (2003). 2.3. Energy balance calculations EB was estimated as the difference between energy intake and the sum of energy for maintenance and milk production (or pregnancy in the pre-calving period). The French net energy (NE) system was used (Jarrige, 1989). The NE content of the concentrates offered was determined using the NE values (UFL) of ingredients (INRAtion, 1989). One UFL is the NE content for milk production of 1 kg of air-dry standard barley (Jarrige, 1989). The NE value of
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silage was related to its in vitro dry matter digestibility concentration (O’Mara et al., 1997). The following equations were used to determine the energy required for maintenance and pregnancy and the energy output in milk: Energy requirement for maintenance : UFL=day ¼ 1:4 þ 0:6BW=100 Energy requirement for pregnancy : UFL=day ¼ 0:00075*BWO*expð0:0165*ð286 DBCÞÞ Energy output in milk : UFL=kgofmilk ¼ 0:0054FC þ 0:0031PC þ 0:0028LC 0:015 where BW=body weight, BWO=body weight of calf at calving, DBC=day before calving, FC=fat content, PC=protein content and LC=lactose content all in g/kg. 2.4. Statistical analysis One cow was removed from the experiment for reasons not connected with the treatments. Repeated measures analysis of variance for the effects of the pre-calving treatments on energy balance and NE intake was carried out using the GLM procedure of SAS (SAS Institute, 1991). Treatment, time and treatment by time interactions were tested. Repeated measures analysis of variance for the effects of pre-calving and post-calving treatments on energy balance, NE intake and blood metabolite concentrations in the post-calving period was carried out, again using the GLM procedure of SAS (SAS Institute, 1991). The model used included terms for precalving treatment, post-calving treatment, time, and all the interactions. Actual calving day and length of time on the pre-calving diet were used as co-variates. Analysis of variance was used to analyse the reproductive data for variables such as calving to service interval, calving to conception interval and calving to first observed heat. Chi-square analysis was used to analyse overall pregnancy rate and pregnancy to each service. There was no significant interaction between the pre- and post-calving treatments for any of the variables measured. Therefore, pre- and post-calving treatment effects are presented separately. The differ-
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ences between pre-calving treatments and post-calving treatments were tested for significance (separately) using Students t-test. Cows were grouped into those that conceived or failed to conceive to either first service or to overall services and the energy balance data for these groups analysed by analysis of variance using the GLM procedure of SAS (SAS Institute, 1991). Correlation coefficients between EB and some of the blood metabolites were obtained using the proc corr procedure of SAS (SAS Institute, 1991).
3. Results 3.1. Effect of pre-calving diets 3.1.1. NE intake The mean NE intakes for the pre-calving period were 5.5, 6.5 and 9.0 UFL/day (standard error of the difference (S.E.D.)=0.22) for SS, S and C respectively and were all significantly different from each other (P < 0:001). There was a significant time by NE intake interaction in the pre-calving period (Fig. 1a). On C
Fig. 1. Effect of (a) pre-calving and (b) post-calving diets on NE intakes (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Treatments SS, S, and C correspond to the pre-calving treatments of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/day of concentrate, respectively. Treatments LC and HC correspond to the post-calving treatments of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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and SS NE intake increased between week 4 and week 2 pre-calving but it tended to decrease on S. NE intake decreased on all treatments between week 2 and week 1 (which corresponds to the last week of gestation) but the greatest decrease occurred on C. There was also an interaction between pre-calving treatment and time post-calving for NE intake. NE intakes were different between the pre-calving treatments for weeks 1, 2 and 3 post-calving. Treatment C had the greatest NE intake, SS the lowest with S being intermediate between the two. Between weeks 4 and 8 inclusive
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post-calving NE intakes were similar on the three treatments. Mean NE intake (UFL/day) was higher on C (13.8) than SS (13.2) for weeks 1 –8 (P < 0:05) (S.E.D. 0.28) of lactation but it was not different between S (13.4) and C or between S and SS. 3.1.2. Milk energy output There was a significant week by pre-calving treatment interaction in milk energy output for the first 8 weeks of lactation (Fig. 2a). The difference between treatments decreased as lactation week increased.
Fig. 2. Effect of (a) pre-calving and (b) post-calving diets on milk energy output (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Diets SS, S, and C correspond to the pre-calving diets of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/ day of concentrate, respectively and diets LC and HC correspond to the post-calving diets of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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Treatments SS, S and C had maximum milk energy outputs in lactation weeks 5, 2 and 3 respectively. The average NE output for SS, S and C was 10.5, 11.6 and 12.7 UFL/day (S:E:D: ¼ 0:48 ) respectively all of which were significantly different from each other. 3.1.3. NE balance pre- and post-calving EB was different (P < 0:001 ) between the three treatments for each of the four pre-calving weeks (Fig.
3a). Mean EB for the pre-calving period was 2.2, 1.17 and +1.17 UFL/day (S.E.D. 0.197) for SS, S and C respectively. There was a significant time by treatment interaction, pre-calving. In C, EB improved from week 4 to week 2 pre-calving and then declined whereas in S, EB tended to disimprove from week 4 to week 1 pre-calving. The differences in EB of greater than 1 UFL between SS and S at 4 weeks pre-calving had decreased to about 0.5 UFL in the
Fig. 3. Effect of (a) pre-calving and (b) post-calving diets on Energy Balance (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Diets SS, S, and C correspond to the pre-calving diets of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/day of concentrate, respectively and diets LC and HC correspond to the post-calving diets of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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final week of gestation. For all treatments, EB declined most rapidly in the final week of gestation. Post-calving, there was no significant time by precalving treatment interaction as the pattern of change in EB was generally the same for the 3 treatments over the 8-week period. Mean EB for the first 8 weeks post-calving was 1.52, 2.60 and 3.72 UFL/day (S.E.D. 0.435) for SS, S and C respectively. Cows on all pre-calving treatments were in NEB for the first 8 weeks post-calving (Fig. 3). For 7 of the 8 weeks post-calving (excluding week 7), C had in a greater NEB (P < 0:01 ) than SS. Treatment S had an EB intermediate between SS and C with a mean NEB value more severe (P < 0:05) than SS. The magnitude of the NEB declined as week post-calving increased going from 3.72, 4.01 and 6.18 UFL/day in week 1 to 0.57, 1.59 and 2.16 UFL/day in week 8 for S, SS and C, respectively. 3.1.4. Blood metabolites At calving, C had a lower plasma urea concentration than S and SS had a lower plasma bile acid concentration than S (Table 1). At week 2 postcalving, C had a higher plasma BHB concentration than SS and a higher plasma protein concentration than SS or S. At week 8 post-calving, plasma NEFA and protein were higher in C than in SS or S. Also plasma urea concentration was lower in SS than in S. 3.1.5. Reproductive performance No effects of pre-calving treatment were detected on any of the reproductive variables recorded. Pregnancy rate to first service ranged from 0.45 to 0.65 and overall pregnancy rate from 0.78 to 0.95. First observed heat was on average 33 days after calving. Calving to conception interval was 105, 100 and 105 days for SS, S and C respectively. 3.2. Effect of post-calving diet 3.2.1. NE intake Weekly NE intakes are shown in Fig. 1b. There was a significant time by post-calving treatment interaction on NE intake. Mean NE intake was higher (P < 0:01) on HC compared with LC (15.10 vs. 11.94 UFL/day). Weekly NE intake increased from approximately 10 and 12 UFL/day on LC and HC to just over 12 UFL/ day on LC and approximately 16 UFL/day on HC.
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Table 1 Effect of pre-calving diet on mean plasma metabolite concentrations 1
At calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
SS
S
C
2
5.40 0.38 0.35 5.46a,b3 68.2 65.4a
5.23 0.36 0.34 5.78a 68.5 130.1b
5.30 0.44 0.35 4.72b 70.6 115.5a,b
0.459 0.064 0.038 0.458 1.78 26.69
S.E.D.
Week 2 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.73 0.35 0.53a 4.64 68.9a 228.4
3.64 0.46 0.60a,b 5.41 68.8a 245.6
3.63 0.45 0.77b 4.72 74.3b 224.6
0.122 0.071 0.114 0.407 1.80 26.06
Week 8 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
4.02 0.10a 0.43 4.84a 74.8a 258.7
3.97 0.10a 0.48 5.79b 74.1a 274.6
4.03 0.17b 0.42 5.25a,b 80.4b 227.9
0.098 0.031 0.041 0.397 1.94 0.562
1
SS=silage/straw 75/25 on a DM basis ad lib; S=silage ad lib; C=silage ad lib+3 kg/day of concentrate. 2 Standard error of difference. 3 Within rows means not sharing a common superscript differ significantly (P < 0:05).
Maximum UFL intake during the trial was reached in week 5 on both treatments. 3.2.2. Milk energy output There was a significant week by post-calving treatment interaction in milk energy output for the first 8 weeks of lactation (Fig. 2b). Milk energy output tended to increase up to week 5 of lactation on HC and up to week 3 on LC and it then declined subsequently on both treatments. The difference between treatments in milk energy output was less than 0.5 UFL/day in week 1 of lactation and greater than 2 UFL by week 8 of lactation. The average energy output for LC and HC was 10.7 and 12.5 UFL/day (P < 0:001) respectively. 3.2.3. Energy Balance Cows on LC had a (P < 0:05) greater NEB in each of the first 8 weeks post-calving (Fig. 3b) compared to those on HC. The greatest NEB occurred at week 1
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post-calving at 5.33 and4.1 UFL/day for LC and HC respectively. The NEB on both treatments decreased with time after calving. At week 8 post calving, LC and HC had NEB values of 2.0 and 0.9 UFL/day, respectively. 3.2.4. Blood metabolites Plasma glucose and bile acids were higher on HC compared to LC at 2 weeks post-calving (Table 2). Plasma urea concentrations were lower on HC compared to LC. The correlation coefficients between NEFA concentrations at weeks 2 post calving and NEB level averaged over the first 4 weeks of lactation (r ¼ 0:05) and the NEB level at week 2 (r ¼ 0:04) were not significant. A correlation coefficient of r ¼ 0:29 was obtained between BHB concentrations at week 2 post-calving and the NEB levels averaged over the first 4 weeks of lactation. 3.2.5. Reproductive performance No differences were detected between the postcalving treatments for any of the reproductive variables recorded. Calving to conception interval was 102 and 105 days and calving to first observed heat was 35 and 31 days for LC and HC respectively. Pregnancy rate to first service was 0.53 and 0.56 and overall pregnancy Table 2 The effect of post-calving treatments on blood metabolites at 2 and 8 weeks post-calving 1
LC
HC
2
S.E.D.
Week 2 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.56a3 0.38 0.70 5.31a 70.9 206.3a
3.77b 0.46 0.57 4.52b 70.4 259.5b
0.099 0.082 0.093 0.332 1.47 21.28
Week 8 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.93 0.13 0.43 5.19 75.0 253.7
4.07 0.11 0.46 5.40 78.0 253.8
0.080 0.025 0.033 0.324 1.58 22.42
1
LC=grass silage and 4 kg/cow per day of concentrate post-calving, HC=grass silage and 8 kg/cow per day of concentrate post-calving. 2 Standard error of difference. 3 Within rows means not sharing a common superscript differ significantly.
rate was 0.82 and 0.87 for the LC and HC respectively. Using post hoc analysis there was no difference in the average NEB for the first 8 weeks of lactation of cows that conceived (NEB=2.73 UFL/day) and those that failed to conceive (NEB=2.45 UFL/day) to first service or those that conceived (NEB=2.60 UFL/ day) or failed to conceive (NEB=2.68 UFL/day) to all services over the first 8 weeks of lactation.
4. Discussion 4.1. Effects of pre-calving diets 4.1.1. NE intake and milk energy output NE intake increased as the ED of the diet increased from 0.73 UFL/kg DM for SS to 0.80 UFL/kg DM for S to 0.91 UFL/kg DM for C. However, the NE intakes on SS and S diets were low and would be insufficient to meet the requirements in the final month of pregnancy of a cow weighing 600 kg and producing a calf weighing 40 kg (estimated requirement of 7.6 UFL/d). This conclusion is supported by the observed loss of BCS on SS (0.09 units) and the unchanging BCS on S (0.01 units) in the final 4 weeks of gestation (McNamara et al., 2003). Milk energy outputs postcalving also increased with pre-calving NE intake and reflected the pattern of dry matter intake observed on the treatments (mean of 13.5, 13.8 and 14.2 kg DM/ cow per day on SS, S and C, respectively—McNamara et al., 2003). 4.1.2. Energy balance The association between postpartum EB and the reinitiation of normal ovarian cycles in high producing dairy cattle has been recognised (Butler and Smith, 1989). EB has been defined as the difference between the energy intake of the animal and the energy required for maintenance and pregnancy, in the gestating cow, and that required for maintenance and milk production in the lactating cow. As expected there were significant differences in EB between the three treatments before calving. The results indicate that cows on relatively good quality silage (0.8 UFL/ kg DM) alone pre-calving are in NEB in the final 4 weeks of gestation. Including a concentrate supplement resulted in positive EB at that time due to the increase in DM intake (mean of 9.9 v. 8.1 kg DM/cow
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per day on S and C, respectively—McNamara et al., 2003) of a higher ED diet. In the first week of lactation cows on all treatments were in severe NEB, with those on C being most severe. This agrees with the findings of Reid et al. (1966) and VillaGodoy et al. (1988) who stated that at least 80% of dairy cows are in NEB during early lactation. Treatment C that was in positive EB in the final 4 weeks of gestation experienced the greatest NEB in early lactation. These cows had the highest BCS at calving (2.87, 2.76 and 2.62 units on C, S and SS, respectively—McNamara et al., 2003) which allowed them to lose the greatest amount of BCS in early lactation. They were also the highest yielders in the first 8 weeks of lactation. According to Jarrige (1989), cows with a peak milk yield of 30 –35 kg/day can tolerate an average energy deficit of 2.5 UFL/d over the first 7 – 8 weeks of lactation with most of this occurring in the first 3 –5 weeks. This would suggest that cows on C in this study had too high an energy deficit with an average NEB of 3.6 UFL/day over the first 8 weeks of lactation compared to an NEB of 2.0 and 2.5 UFL/day for SS and S respectively. The degree of NEB decreased as cows progressed from week 1 to week 8 of lactation even though at this stage, all treatments were still in NEB. This trend is similar to that found by Sutter and Beever (2000) for animals offered a hay based diet where NEB declined from a maximum of 63.8 MJ of ME/day in the first week of lactation to 20.7 MJ of ME/day in week 8 of lactation. 4.1.3. Blood metabolites Plasma glucose concentrations remain stable or increase slightly during the pre-partum transition period, increase dramatically at calving and then decrease immediately after calving (Kunz et al., 1985; Vazquez-An˜on et al., 1994). Glucose concentration should remain above 3 mmol/l according to Whitaker et al. (1983). Chamberlain and Wilkinson (1998) suggested that glucose was a suitable metabolite for assessing animal energy status but the current results would not support this where pre-calving diet had no significant effect on plasma glucose concentrations, either at calving or post-calving despite significant differences in EB. Whitaker (1997) suggested that glucose was not as sensitive as NEFA or BHB to changes in EB.
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The desired plasma concentration for NEFA is below 0.7 mmol/l for cows in early lactation and below 0.4 mmol/l towards the end of pregnancy (Whitaker et al., 1983). The concentrations measured in this study were within these targets. Cows receiving concentrates pre-calving had significantly higher plasma NEFA concentrations at week 8 post-calving compared with the other treatments and had numerically higher NEFA concentrations than cows on SS at week 2 post-calving. This could be a reflection of the greater tissue mobilisation on this treatment. Plasma NEFA concentrations decrease after calving (Grummer, 1995), which was the trend observed in the present study. In the current study the correlation coefficients between NEFA concentrations at week 2 post-calving and NEB level averaged over the first 4 weeks of lactation (r ¼ 0:05) and the NEB level at week 2 (r ¼ 0:04) were not significant suggesting that NEFA also was not a very accurate indicator of NEB in early lactation in this study. The optimum concentration of BHB for lactating cows is below 1 mmol/l in early lactation and below 0.6 mmol/l for cows at the end of pregnancy (Whitaker et al., 1983) and the concentrations found in the present study were within those targets. In general the trends in plasma BHB concentrations found in this study agree with those of Kunz et al. (1985) who observed that postpartum plasma BHB concentrations were higher in cows fed generously compared to those fed at restricted levels pre-partum. There was a negative correlation of r ¼ 0:29 (P < 0:05) between BHB concentrations at week 2 post-calving and the NEB levels averaged over the first 4 weeks of lactation. At 2 weeks post-calving cows on C had significantly higher plasma BHB concentrations than those on SS. This would be consistent with the greater loss of LW and BCS post-calving observed for these cows (0.58 kg/day and 0.18 kg/day live weight change and 0.26 and 0.02 units of BCS change in the first 8 weeks of lactation on C and SS, respectively—McNamara et al., 2003) indicating greater mobilisation of body fat. These results suggest that BHB may be a more useful indicator of EB and also of BCS and LW loss than either glucose or NEFA. The lower plasma urea concentrations at calving for the cows supplemented with concentrates compared to those on silage alone may reflect a greater capture of N in the rumen due to the enhanced rumen
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fermentable energy supply from the concentrates. The differences between pre-calving treatments in plasma urea concentrations at week 8 post-calving were surprising especially since no such differences were observed at week 2 post-calving. Plasma protein concentrations were higher at week 2 and 8 after calving in the cows that received C before calving which may reflect a better protein status. 4.1.4. Fertility performance Pre-calving diet and nutrition have been reported to affect subsequent reproductive performance (Whitaker et al., 1993) although no significant effects could be detected in the current study. Flipot et al. (1988) reported that cows on the highest ED diet pre-partum had the longest calving to conception interval; however they found no differences in calving to first oestrus or services per conception. Results from Johnson and Otterby (1981) found that improving pre-partum diet had no significant effect on calving to conception interval or on services per conception. However, the fact that no significant effects were detected in the current study has to be interpreted cautiously because of the relatively low number of animals per treatment but the results are supported by the findings of Keady et al. (2001) who stated that concentrate supplementation in late gestation had no beneficial effects on subsequent fertility. In the current study no significant differences in EB in the first 8 weeks of lactation were found between cows that conceived to first service or a subsequent service with those that did not conceive. According to Butler and Smith (1989) the most likely nutritional factor to influence fertility is EB in early lactation particularly at the time of first service. A possible reason for the absence of a detrimental effect of NEB in early lactation on fertility in the present study may be the longer than normal calving to service interval. This arose because the experimental cows were the earlier calving spring cows in the herd. 4.2. Effect of post-calving diets 4.2.1. NE intake, milk energy output and energy balance Post-calving diet had a significant effect on postcalving NE intake in the first 8 weeks of lactation. This was a consequence of the greater DM intake on
the HC compared to the LC treatment (mean of 15.1 vs. 12.6 kg/cow per day—McNamara et al., 2002). NE intake was, on average, 26% greater over the first 8 weeks of lactation on HC compared to LC treatment. On both treatments, NE intake increased from calving and reached its maximum at about week 3 on LC and at week 4 on HC. Milk energy output was, as expected, higher on the more energy dense HC diet. EB was most negative on LC but its severity declined for both treatments as week of lactation increased. Butler et al. (1981) found that cows reached positive balance by day 80 post-calving on average. VillaGodoy et al. (1988) stated that greater than 50 days post-calving would be required for cows to reach positive balance. The results from the present study would support these findings. 4.2.2. Blood metabolites Plasma indicators of energy and protein status would be expected to reflect the greater mobilisation of body tissue as indicated by the greater NEB in LC compared to the HC. Plasma BHB concentrations were higher on LC compared to HC at week 2 postcalving but the difference was not significant. However, glucose concentrations were higher on HC at week 2 post-calving and were also higher but not significantly so (P ¼ 0:08 ) at week 8 post-calving. This confirms an enhanced energy status for those animals on HC. The lower plasma urea concentration on HC compared to LC at week 2 post-calving reflected the lower grass silage intake (McNamara et al., 2003) and greater rumen fermentable energy intake from concentrates on this treatment. 4.2.3. Fertility performance A significant decline in the calving rate to first service of approximately 0.9% per annum has been observed in Irish dairy herds between 1991 and 1998 (Mee et al., 1999). It has been suggested that early lactation NEB may be the underlying causative factor in the association between increased milk output and declining reproductive performance (Butler and Smith, 1989; Nebel and McGilliard, 1993; Macmillan et al., 1996). However, in this study no effect of postcalving concentrate supplementation level on reproductive performance could be detected, despite significant differences in NEB being observed. The number of animals per treatment was a limiting factor
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in detecting significant differences but no strong trends indicating an association between greater NEB and poorer fertility performance were observed.
5. Conclusions Good quality grass silage alone is not adequate to maintain cows in positive energy balance in the final 4 weeks of gestation. Increasing the ED of the diet precalving increased the NE intake and decreased the NEB pre-calving. Cows supplemented with concentrates pre-calving were in positive EB until calving but then experienced the greatest degree of NEB in the first 8 weeks of lactation. Blood metabolites did not appear to be good indicators of EB either before or after calving. Supplementing with a higher level of concentrates after calving reduced NEB but did not eliminate it. No significant differences in reproductive performance were detected despite significant differences in EB being observed between treatments.
Acknowledgements The authors would like to thank Mr. Noel Byrne and farm staff, Mr. Joe Dwyer, Ms. Justine Haugh and Ms. Norann Galvin for skilled technical assistance and Dr. Dermot Harrington for statistical advice. Funding from Irish dairy farmers is gratefully acknowledged.
References Bauman, D.E., Peel, C.J., Steinhour, W.D., Reynolds, P.J., Tyrrell, H.T., Brown, A.C.G., Haaland, G.L., 1988. Effect of bovine somatotrophin on metabolism of lactating dairy cows: influence on rates of irreversible loss and oxidation of glucose and nonesterified fatty acids. J. Nutr. 118, 1031 – 1040. Bell, A.W., 1995. Regulation of organic nutrient metabolism during transition from late pregnancy to early lactation. J. Anim. Sci. 73, 2804 – 2819. Bertics, S.J., Grummer, R.R., Cadoringa-Valino, C., Stoddard, E.E., 1992. Effect of prepartum dry matter intake on liver triglyceride concentration and early lactation. J. Dairy Sci. 75, 1914 – 1922. Butler, W.R., Smith, R.D., 1989. Interrelationships between energy balance and postpartum reproductive function in dairy cattle. J. Dairy Sci. 72, 767 – 783. Butler, W.R., Everett, R.W., Coppock, C.E., 1981. The relationships
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between energy balance, milk production and ovulation in postpartum Holstein cows. J. Anim Sci. 53, 742 – 748. Canfield, R.W., Butler, W.R., 1990. Energy balance and pulsatile LH secretion in early postpartum dairy cattle. Domest. Anim. Endocrinol. 7, 323 – 330. Chamberlain, A.T., Wilkinson, J.M., 1998. Assessing nutritional status. Feeding the Dairy Cow. Chalcombe Publications, Lincoln, UK, pp. 159 – 166. Chandler, P., 1995. Transition period of cows presents unique challenge to nutritionists. Feedstuffs 11, 11. Dann, H.M., Varga, G.A., Putnam, D.E., 1999. Improving energy supply to late gestation and early postpartum dairy cows. J. Dairy Sci. 82, 1765 – 1778. Dewhurst, R.J., Moorby, J.M., Dhanoa, M.S., Evans, R.T., Fisher, W.J., 2000. Effects of altering energy and protein supply to dairy cows during the dry period. 1. Intake, body condition and milk production. J. Dairy Sci. 83, 1782 – 1794. Ducker, M.J., Haggett, R.A., Fisher, W.J., Morant, S.V., Bloomfield, G.A., 1985. Nutrition and reproductive performance of dairy cattle. 1. The effect of level of feeding in late pregnancy and around the time of insemination on the reproductive performance of first lactation dairy heifers. Anim. Prod. 41, 1 – 12. Dunshea, F.R., Bell, A.W., Trigg, T.E., 1989. Relations between plasma non-esterified fatty acid metabolism and body fat mobilization in lactating goats. Br. J. Nutr. 62, 51. Flipot, P.M., Roy, G.L., Dufour, J.J., 1988. Effect of peripartum energy concentration on production performance of Holstein cows. J. Dairy Sci. 71, 1840 – 1850. Grummer, R.R., 1995. Impact of changes in organic nutrient metabolism on feeding the transition dairy cow. J. Anim. Sci. 73, 2820 – 2833. INRAtion, 1989, V2.7. Microsoft computer program of ration formulation for ruminant livestock. 1. Dairy cows (J.B. Coulon and P. Faverdin). 2. Sheep (F. Bocquier and A. Brelurut). 3. Growing and finishing cattle (D. Micol, J. Robelin and J. Agabriel). 4. Suckler cows (J. Agabriel). 5. Goats (D. Sauvant). J. Agabriel, P. Champciaux, C. Espinasse (Eds.). CNERTA, 26 Boulevard du Docteur Petit Jean 21000, Dijon, France. Jarrige, R., 1989. Dairy cows. Ruminant Nutrition: recommended allowances and feed tables. John Libbey, Eurotext, Paris, London, Rome, pp. 73 – 91. Johnson, D.G., Otterby, D.E., 1981. Influence of dry period diet on early postpartum health, feed intake, milk production and reproductive efficiency of Holstein cows. J. Dairy Sci. 64, 290 – 295. Keady, T.W.J., Mayne, C.S., Fitzpatrick, D.A., McCoy, M.A., 2001. Effect of concentrate feed level in late gestation on subsequent milk yield, milk composition, and fertility of dairy cows. J. Dairy Sci. 84, 1468 – 1479. Kunz, P.L., Blum, J.W., Hart, I.C., Bickel, H., Landis, J., 1985. Effects of different energy intakes before and after calving on food intake, performance and blood hormones and metabolites in dairy cows. Anim. Prod. 40, 219 – 231. Macmillan, K.L., Lean, I.J., Westwood, C.T., 1996. The effects of lactation on the fertility of dairy cows. Aust. Vet. J. 73, 141 – 147. McNamara, S., O’Mara, F.P., Rath, M., Murphy, J.J., 2003. Effects of different transition diets on dry matter intake, milk production and milk composition in dairy cows. J. Dairy Sci. (in press).
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Mee, J.F., Fahey, J., Crilly, J., 1999. Breeding the dairy cow of the future—todays challenges. Dairying in the New Millennium. Teagasc National Dairy Conference, Adare, Ireland., pp. 7 – 16. Minor, D.J., Trower, S.L., Strang, B.D., Shaver, R.D., Grummer, R.R., 1998. Effects of nonfiber carbohydrate and niacin on periparturient metabolic status and lactation of dairy cows. J. Dairy Sci. 81, 189 – 200. Moe, P.W., Tyrrell, H.F., 1972. Metabolizable energy requirements of pregnant dairy cows. J. Dairy Sci. 55, 480 – 483. Nebel, R.L., McGilliard, M.L., 1993. Interactions of milk yield and reproductive performance in dairy cows. J. Dairy Sci. 76, 3257 – 3268. O’Mara, F.P., Caffrey P.J., Drennan M.J., 1997. The net energy value of grass silage determined from comparative feeding trials. Ir. J. Agric. and Fd. Res. 36 110, Abstract. Patton, R.P., Poley, G., 1996. Understanding of energy status of prepartum cow improves, Nutrition and Health/Dairy, Feedstuffs 64 No. 24. Reid, J.T., Moe, P.W., Tyrrell, H.F., 1966. Energy and protein requirements of milk production. J. Dairy Sci. 49, 215 – 223. Statistics Analysis Systems (SAS) Institute, 1991. User’s Guide: statistics, Cary, NC: SAS Institute. Sutter, F., Beever, D.E., 2000. Energy and nitrogen metabolism in
Holstein – Friesian cows during early lactation. Anim. Sci. 70, 503 – 514. Topps, J.H., Thompson, J.K., 1984. Blood characteristics and the nutrition of ruminants, Ministry of Agriculture, Fisheries and Food, Reference Book 260. Vandehaar, M.J., Yousif, G., Sharma, B.K., Herdt, T.H., Emery, R.S., Allen, M.S., Liesman, J.S., 1999. Effect of energy and protein density of prepartum diets on fat and protein metabolism of dairy cattle in the periparturient period. J. Dairy Sci. 82, 1282 – 1295. Vazquez-An˜on, M., Bertics, S., Luck, M., Grummer, R.R., 1994. Peripartum liver triglyceride and plasma metabolites in dairy cows. J. Dairy Sci. 77, 1521 – 1528. Villa-Godoy, A., Hughes, T.L., Emery, R.S., Chapin, L.T., Fogwell, R.L., 1988. Association between energy balance and luteal function in lactating dairy cows. J. Dairy Sci. 71, 1063 – 1072. Whitaker, D.A., Kelly, J.M., Smith, E.J., 1983. Subclinical ketosis and serum beta-hydroxybutyrate levels in dairy cattle. Br. Vet. J. 139, 462 – 463. Whitaker, D.A., 1997. Interpretation of metabolic profiles in dairy cows. Cattle Practice 5, 57 – 60. Whitaker, D.A., Smith, E.J., da Rosa, G.O., Kelly, J.M., 1993. Some effects of nutrition and management on the fertility of dairy cattle. Vet. Rec. 133, 61 – 64.
Effects of different transition diets on energy balance, blood metabolites and reproductive performance in dairy cows S. McNamara a,b, J.J. Murphy a,*, M. Rath b, F.P. O’Mara b b
a Teagasc, Dairy Production Research Centre, Moorepark, Fermoy, Co. Cork, Ireland Department of Animal Science and Production, University College Dublin, Belfield, Dublin 4, Ireland
Received 26 June 2002; received in revised form 26 February 2003; accepted 24 March 2003
Abstract The objective of this study was to evaluate the effect of diets differing in energy density (ED) in the last 4 weeks of the dry period and in the first 8 weeks of lactation on energy balance (EB), blood metabolites and reproductive performance. Three diets (grass silage:straw 75:25 on a dry matter basis (SS), grass silage (S) and grass silage+3 kg/day of concentrates (C)) precalving and two diets (4 kg (LC) or 8 kg/day of concentrates (HC)+grass silage ad libitum) post-calving were combined in a 32 factorial design. Sixty second-lactation Holstein – Friesian cows were blocked according to expected calving date and body condition score into groups of six and were then allocated at random to the treatments. Individual feeding started on average 34 days prior to parturition and measurements were made until the end of the 8th week of lactation. Net energy (NE) intake increased (5.6, 6.5 and 9.0 UFL/cow per day; (standard error of the difference (S.E.D.)=0.22) and EB improved pre-calving as the ED of the diet increased. Post-calving, milk energy output was significantly different between pre-calving treatments at 10.5, 11.6 and 12.7 UFL/day (S.E.D.=0.48) for SS, S and C respectively. Cows on the highest ED diet pre-calving (C) had a greater degree of negative energy balance (NEB) than cows on the lowest ED diet pre-calving (SS) for 7 of the first 8 weeks of lactation. At calving, cows on C had a lower plasma urea concentration than those on S and cows on SS had a lower plasma bile acid concentration than those on S. At week 2 post-calving, C had a higher plasma h-hydroxybutyrate concentration than SS and a higher plasma protein concentration than SS or S. Post-calving, cows receiving HC had higher NE intakes averaged over the first 8 weeks of lactation and lower NEB in each of the first 8 weeks of lactation than those on LC. Plasma glucose and bile acid concentrations were higher on HC compared to LC at week 2 post-calving. Plasma urea concentrations were lower (P < 0:05) on HC compared to LC. D 2003 Elsevier B.V. All rights reserved. Keywords: Dairy cattle; Negative energy balance; Reproductive performance; Dry cow; Lactation; Blood metabolites
1. Introduction In modern agriculture, genetic selection for intense production has resulted in animals that produce food * Corresponding author. Tel.: +353-25-42-222; fax: +353-2542-340. E-mail address: [email protected] (J.J. Murphy). 0301-6226/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0301-6226(03)00093-9
for mankind at a rate beyond the capability of their inherent metabolic machinery (Patton and Poley, 1996). This has led to a situation with the dairy cow where she has difficulty in consuming enough energy to meet her requirements for maintenance and milk production, especially in early lactation. In the last month of pregnancy the energy requirements of the dairy cow increase by 23% to support
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foetal and gravid uterus growth (Moe and Tyrrell, 1972). From 1 week prior to parturition, to 1 day before calving, mammary uptake of glucose increases by 400%, acetate uptake by 180% and blood flow increases by 200% (Bell, 1995). To compound the difficulty of increased energy requirements close to calving, dry matter intake (DMI) starts to decline approximately 3 weeks before parturition and reduces dramatically in the last 7 days. The level of decline has been as high as 30% (Bertics et al., 1992; Chandler, 1995; Grummer, 1995). Increasing the energy concentration of the diet precalving has increased voluntary intake and consequently energy intake, increased body weight gain, reduced the mobilisation of adipose tissue as parturition approaches and lowered plasma non-esterified fatty acid (NEFA) concentrations (Bertics et al., 1992; Minor et al., 1998; Dann et al., 1999; Vandehaar et al., 1999; Dewhurst et al., 2000). The rise in plasma NEFA around the time of parturition is partly due to hormonal changes and stress associated with pregnancy and reduced DMI. The importance of postpartum energy balance (EB) on the recommencement of normal ovarian cycles in high producing dairy cows has been recognised (Butler and Smith, 1989). The degree of negative energy balance (NEB) in the early postpartum period has been correlated with both the level of milk production and the number of days to first ovulation (Butler et al., 1981; Ducker et al., 1985). Bauman et al., (1988), Dunshea et al., (1989) and Canfield and Butler (1990) found a high correlation between NEFA and EB. High NEFA concentrations reflect a degree of under-nutrition and more severe NEB (Topps and Thompson, 1984). The quality of the pre-calving diet is often neglected on dairy farms and research on pre-calving nutrition in high grass silage systems is limited. There are little data with grass silage based diets on the effect of increasing energy density (ED) of the diet in the pre-calving period on EB in early lactation and reproductive performance. The objective of this study was to determine the effects of offering diets differing in ED both pre- and postpartum on EB around calving, blood metabolite concentrations and reproductive performance of Irish bred Holstein – Friesian dairy cows.
2. Materials and methods 2.1. Treatments Sixty spring-calving Holstein – Friesian dairy cows, calving for the second time, were blocked and assigned to treatments 4 weeks before expected calving dates as described by McNamara et al. (2003). The treatments were: 1. Grass silage/barley straw mixture on a 75:25 dry matter basis offered ad libitum (SS) pre-calving, with ad libitum grass silage and 4 kg/cow per day of concentrate post-calving (LC). 2. SS pre-calving with ad libitum grass silage and 8 kg/cow per day of concentrate post-calving (HC). 3. Grass silage offered ad libitum (S) pre-calving with LC post-calving. 4. S pre-calving with HC post-calving. 5. Grass silage offered ad libitum plus 3 kg/cow per day of concentrate (C) pre-calving with LC postcalving. 6. C pre-calving with HC post-calving. The treatments were imposed from, on average, 34 days before actual calving day. The feeding and management of the cows were as described by McNamara et al. (2003). 2.2. Measurements Milk yield (kg) was recorded on a daily basis at both the morning and the evening milking. Milk fat, protein and lactose concentrations were determined once weekly on successive morning and evening milk samples. These data in conjunction with the respective morning and evening milk yields were used to calculate a daily composite fat, protein and lactose concentration. Liveweight (LW) (kg) was measured weekly. The dry cows were weighed before feeding in the morning and the lactating cows were weighed after morning milking. DMI was measured on a daily basis. Reproductive performance of the cows was recorded. Oestrus was detected by thrice daily observation with the aid of tail paint. First observed heat post-calving was recorded for all cows prior to the start of the breeding season. First service (cows were bred at the first heat after April 22, which is typical
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for seasonal spring calving herds) was the first time cows were bred and conception was the first positive scan examined by ultrasonography, using a 5-MHz rectal transducer (Aloka SSD-500V, Japan), which corresponded to a service date. Pregnancy examinations were carried out by ultrasound at 30 –40 days post insemination and 1 month after the end of the breeding season. This gave the following fertility measurements: calving to first service, calving to conception interval, services per conception, pregnancy rate and infertile rate. The breeding season lasted 13 weeks. All cows were served with semen from the same bull and inseminated by one technician to eliminate any variation in fertility due to either different bulls or inseminators. Blood samples were taken from all cows within 12 h of parturition, and at 2 and 8 weeks post-calving. All blood samples were taken from the coccygeal vessels in the morning before feeding. At the time of blood sampling, samples were collected into two different vacutainers, one containing lithium heparin and the other containing fluoride oxalate as anticoagulants. The samples were immediately placed on ice packs and centrifuged within 30 min of sampling. Samples were centrifuged at 1800 g at 0 jC for 10 min. The plasma was decanted into screw-capped tubes, frozen, and stored at 20 jC until analysis. All blood analysis was carried out using appropriate kits and an ABX Mira autoanalyzer (ABX Mira, Cedex 4, France). The metabolites analysed were glucose, NEFA, BHB, urea, protein and bile acids. Glucose was determined in fluoride oxalate plasma and the other analyses were performed on lithium heparin plasma. Laboratory analysis of feedstuffs and milk composition was carried out as described by McNamara et al. (2003). 2.3. Energy balance calculations EB was estimated as the difference between energy intake and the sum of energy for maintenance and milk production (or pregnancy in the pre-calving period). The French net energy (NE) system was used (Jarrige, 1989). The NE content of the concentrates offered was determined using the NE values (UFL) of ingredients (INRAtion, 1989). One UFL is the NE content for milk production of 1 kg of air-dry standard barley (Jarrige, 1989). The NE value of
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silage was related to its in vitro dry matter digestibility concentration (O’Mara et al., 1997). The following equations were used to determine the energy required for maintenance and pregnancy and the energy output in milk: Energy requirement for maintenance : UFL=day ¼ 1:4 þ 0:6BW=100 Energy requirement for pregnancy : UFL=day ¼ 0:00075*BWO*expð0:0165*ð286 DBCÞÞ Energy output in milk : UFL=kgofmilk ¼ 0:0054FC þ 0:0031PC þ 0:0028LC 0:015 where BW=body weight, BWO=body weight of calf at calving, DBC=day before calving, FC=fat content, PC=protein content and LC=lactose content all in g/kg. 2.4. Statistical analysis One cow was removed from the experiment for reasons not connected with the treatments. Repeated measures analysis of variance for the effects of the pre-calving treatments on energy balance and NE intake was carried out using the GLM procedure of SAS (SAS Institute, 1991). Treatment, time and treatment by time interactions were tested. Repeated measures analysis of variance for the effects of pre-calving and post-calving treatments on energy balance, NE intake and blood metabolite concentrations in the post-calving period was carried out, again using the GLM procedure of SAS (SAS Institute, 1991). The model used included terms for precalving treatment, post-calving treatment, time, and all the interactions. Actual calving day and length of time on the pre-calving diet were used as co-variates. Analysis of variance was used to analyse the reproductive data for variables such as calving to service interval, calving to conception interval and calving to first observed heat. Chi-square analysis was used to analyse overall pregnancy rate and pregnancy to each service. There was no significant interaction between the pre- and post-calving treatments for any of the variables measured. Therefore, pre- and post-calving treatment effects are presented separately. The differ-
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ences between pre-calving treatments and post-calving treatments were tested for significance (separately) using Students t-test. Cows were grouped into those that conceived or failed to conceive to either first service or to overall services and the energy balance data for these groups analysed by analysis of variance using the GLM procedure of SAS (SAS Institute, 1991). Correlation coefficients between EB and some of the blood metabolites were obtained using the proc corr procedure of SAS (SAS Institute, 1991).
3. Results 3.1. Effect of pre-calving diets 3.1.1. NE intake The mean NE intakes for the pre-calving period were 5.5, 6.5 and 9.0 UFL/day (standard error of the difference (S.E.D.)=0.22) for SS, S and C respectively and were all significantly different from each other (P < 0:001). There was a significant time by NE intake interaction in the pre-calving period (Fig. 1a). On C
Fig. 1. Effect of (a) pre-calving and (b) post-calving diets on NE intakes (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Treatments SS, S, and C correspond to the pre-calving treatments of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/day of concentrate, respectively. Treatments LC and HC correspond to the post-calving treatments of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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and SS NE intake increased between week 4 and week 2 pre-calving but it tended to decrease on S. NE intake decreased on all treatments between week 2 and week 1 (which corresponds to the last week of gestation) but the greatest decrease occurred on C. There was also an interaction between pre-calving treatment and time post-calving for NE intake. NE intakes were different between the pre-calving treatments for weeks 1, 2 and 3 post-calving. Treatment C had the greatest NE intake, SS the lowest with S being intermediate between the two. Between weeks 4 and 8 inclusive
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post-calving NE intakes were similar on the three treatments. Mean NE intake (UFL/day) was higher on C (13.8) than SS (13.2) for weeks 1 –8 (P < 0:05) (S.E.D. 0.28) of lactation but it was not different between S (13.4) and C or between S and SS. 3.1.2. Milk energy output There was a significant week by pre-calving treatment interaction in milk energy output for the first 8 weeks of lactation (Fig. 2a). The difference between treatments decreased as lactation week increased.
Fig. 2. Effect of (a) pre-calving and (b) post-calving diets on milk energy output (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Diets SS, S, and C correspond to the pre-calving diets of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/ day of concentrate, respectively and diets LC and HC correspond to the post-calving diets of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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Treatments SS, S and C had maximum milk energy outputs in lactation weeks 5, 2 and 3 respectively. The average NE output for SS, S and C was 10.5, 11.6 and 12.7 UFL/day (S:E:D: ¼ 0:48 ) respectively all of which were significantly different from each other. 3.1.3. NE balance pre- and post-calving EB was different (P < 0:001 ) between the three treatments for each of the four pre-calving weeks (Fig.
3a). Mean EB for the pre-calving period was 2.2, 1.17 and +1.17 UFL/day (S.E.D. 0.197) for SS, S and C respectively. There was a significant time by treatment interaction, pre-calving. In C, EB improved from week 4 to week 2 pre-calving and then declined whereas in S, EB tended to disimprove from week 4 to week 1 pre-calving. The differences in EB of greater than 1 UFL between SS and S at 4 weeks pre-calving had decreased to about 0.5 UFL in the
Fig. 3. Effect of (a) pre-calving and (b) post-calving diets on Energy Balance (pre-calving diets E SS n S . C and post-calving diets n LC . HC). Diets SS, S, and C correspond to the pre-calving diets of silage/straw 75/25 on a DM basis ad lib, silage alone ad lib, and silage ad lib + 3 kg/day of concentrate, respectively and diets LC and HC correspond to the post-calving diets of 4 kg/d concentrate + silage ad lib and 8 kg/d concentrate + silage ad lib, respectively. The error bars correspond to the S.E.D. for the treatments.
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final week of gestation. For all treatments, EB declined most rapidly in the final week of gestation. Post-calving, there was no significant time by precalving treatment interaction as the pattern of change in EB was generally the same for the 3 treatments over the 8-week period. Mean EB for the first 8 weeks post-calving was 1.52, 2.60 and 3.72 UFL/day (S.E.D. 0.435) for SS, S and C respectively. Cows on all pre-calving treatments were in NEB for the first 8 weeks post-calving (Fig. 3). For 7 of the 8 weeks post-calving (excluding week 7), C had in a greater NEB (P < 0:01 ) than SS. Treatment S had an EB intermediate between SS and C with a mean NEB value more severe (P < 0:05) than SS. The magnitude of the NEB declined as week post-calving increased going from 3.72, 4.01 and 6.18 UFL/day in week 1 to 0.57, 1.59 and 2.16 UFL/day in week 8 for S, SS and C, respectively. 3.1.4. Blood metabolites At calving, C had a lower plasma urea concentration than S and SS had a lower plasma bile acid concentration than S (Table 1). At week 2 postcalving, C had a higher plasma BHB concentration than SS and a higher plasma protein concentration than SS or S. At week 8 post-calving, plasma NEFA and protein were higher in C than in SS or S. Also plasma urea concentration was lower in SS than in S. 3.1.5. Reproductive performance No effects of pre-calving treatment were detected on any of the reproductive variables recorded. Pregnancy rate to first service ranged from 0.45 to 0.65 and overall pregnancy rate from 0.78 to 0.95. First observed heat was on average 33 days after calving. Calving to conception interval was 105, 100 and 105 days for SS, S and C respectively. 3.2. Effect of post-calving diet 3.2.1. NE intake Weekly NE intakes are shown in Fig. 1b. There was a significant time by post-calving treatment interaction on NE intake. Mean NE intake was higher (P < 0:01) on HC compared with LC (15.10 vs. 11.94 UFL/day). Weekly NE intake increased from approximately 10 and 12 UFL/day on LC and HC to just over 12 UFL/ day on LC and approximately 16 UFL/day on HC.
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Table 1 Effect of pre-calving diet on mean plasma metabolite concentrations 1
At calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
SS
S
C
2
5.40 0.38 0.35 5.46a,b3 68.2 65.4a
5.23 0.36 0.34 5.78a 68.5 130.1b
5.30 0.44 0.35 4.72b 70.6 115.5a,b
0.459 0.064 0.038 0.458 1.78 26.69
S.E.D.
Week 2 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.73 0.35 0.53a 4.64 68.9a 228.4
3.64 0.46 0.60a,b 5.41 68.8a 245.6
3.63 0.45 0.77b 4.72 74.3b 224.6
0.122 0.071 0.114 0.407 1.80 26.06
Week 8 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
4.02 0.10a 0.43 4.84a 74.8a 258.7
3.97 0.10a 0.48 5.79b 74.1a 274.6
4.03 0.17b 0.42 5.25a,b 80.4b 227.9
0.098 0.031 0.041 0.397 1.94 0.562
1
SS=silage/straw 75/25 on a DM basis ad lib; S=silage ad lib; C=silage ad lib+3 kg/day of concentrate. 2 Standard error of difference. 3 Within rows means not sharing a common superscript differ significantly (P < 0:05).
Maximum UFL intake during the trial was reached in week 5 on both treatments. 3.2.2. Milk energy output There was a significant week by post-calving treatment interaction in milk energy output for the first 8 weeks of lactation (Fig. 2b). Milk energy output tended to increase up to week 5 of lactation on HC and up to week 3 on LC and it then declined subsequently on both treatments. The difference between treatments in milk energy output was less than 0.5 UFL/day in week 1 of lactation and greater than 2 UFL by week 8 of lactation. The average energy output for LC and HC was 10.7 and 12.5 UFL/day (P < 0:001) respectively. 3.2.3. Energy Balance Cows on LC had a (P < 0:05) greater NEB in each of the first 8 weeks post-calving (Fig. 3b) compared to those on HC. The greatest NEB occurred at week 1
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post-calving at 5.33 and4.1 UFL/day for LC and HC respectively. The NEB on both treatments decreased with time after calving. At week 8 post calving, LC and HC had NEB values of 2.0 and 0.9 UFL/day, respectively. 3.2.4. Blood metabolites Plasma glucose and bile acids were higher on HC compared to LC at 2 weeks post-calving (Table 2). Plasma urea concentrations were lower on HC compared to LC. The correlation coefficients between NEFA concentrations at weeks 2 post calving and NEB level averaged over the first 4 weeks of lactation (r ¼ 0:05) and the NEB level at week 2 (r ¼ 0:04) were not significant. A correlation coefficient of r ¼ 0:29 was obtained between BHB concentrations at week 2 post-calving and the NEB levels averaged over the first 4 weeks of lactation. 3.2.5. Reproductive performance No differences were detected between the postcalving treatments for any of the reproductive variables recorded. Calving to conception interval was 102 and 105 days and calving to first observed heat was 35 and 31 days for LC and HC respectively. Pregnancy rate to first service was 0.53 and 0.56 and overall pregnancy Table 2 The effect of post-calving treatments on blood metabolites at 2 and 8 weeks post-calving 1
LC
HC
2
S.E.D.
Week 2 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.56a3 0.38 0.70 5.31a 70.9 206.3a
3.77b 0.46 0.57 4.52b 70.4 259.5b
0.099 0.082 0.093 0.332 1.47 21.28
Week 8 post-calving Glucose (mmol/l) NEFA (mmol/l) BHB (mmol/l) Urea (mmol/l) Protein (g/l) Bile acids (Amol/l)
3.93 0.13 0.43 5.19 75.0 253.7
4.07 0.11 0.46 5.40 78.0 253.8
0.080 0.025 0.033 0.324 1.58 22.42
1
LC=grass silage and 4 kg/cow per day of concentrate post-calving, HC=grass silage and 8 kg/cow per day of concentrate post-calving. 2 Standard error of difference. 3 Within rows means not sharing a common superscript differ significantly.
rate was 0.82 and 0.87 for the LC and HC respectively. Using post hoc analysis there was no difference in the average NEB for the first 8 weeks of lactation of cows that conceived (NEB=2.73 UFL/day) and those that failed to conceive (NEB=2.45 UFL/day) to first service or those that conceived (NEB=2.60 UFL/ day) or failed to conceive (NEB=2.68 UFL/day) to all services over the first 8 weeks of lactation.
4. Discussion 4.1. Effects of pre-calving diets 4.1.1. NE intake and milk energy output NE intake increased as the ED of the diet increased from 0.73 UFL/kg DM for SS to 0.80 UFL/kg DM for S to 0.91 UFL/kg DM for C. However, the NE intakes on SS and S diets were low and would be insufficient to meet the requirements in the final month of pregnancy of a cow weighing 600 kg and producing a calf weighing 40 kg (estimated requirement of 7.6 UFL/d). This conclusion is supported by the observed loss of BCS on SS (0.09 units) and the unchanging BCS on S (0.01 units) in the final 4 weeks of gestation (McNamara et al., 2003). Milk energy outputs postcalving also increased with pre-calving NE intake and reflected the pattern of dry matter intake observed on the treatments (mean of 13.5, 13.8 and 14.2 kg DM/ cow per day on SS, S and C, respectively—McNamara et al., 2003). 4.1.2. Energy balance The association between postpartum EB and the reinitiation of normal ovarian cycles in high producing dairy cattle has been recognised (Butler and Smith, 1989). EB has been defined as the difference between the energy intake of the animal and the energy required for maintenance and pregnancy, in the gestating cow, and that required for maintenance and milk production in the lactating cow. As expected there were significant differences in EB between the three treatments before calving. The results indicate that cows on relatively good quality silage (0.8 UFL/ kg DM) alone pre-calving are in NEB in the final 4 weeks of gestation. Including a concentrate supplement resulted in positive EB at that time due to the increase in DM intake (mean of 9.9 v. 8.1 kg DM/cow
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per day on S and C, respectively—McNamara et al., 2003) of a higher ED diet. In the first week of lactation cows on all treatments were in severe NEB, with those on C being most severe. This agrees with the findings of Reid et al. (1966) and VillaGodoy et al. (1988) who stated that at least 80% of dairy cows are in NEB during early lactation. Treatment C that was in positive EB in the final 4 weeks of gestation experienced the greatest NEB in early lactation. These cows had the highest BCS at calving (2.87, 2.76 and 2.62 units on C, S and SS, respectively—McNamara et al., 2003) which allowed them to lose the greatest amount of BCS in early lactation. They were also the highest yielders in the first 8 weeks of lactation. According to Jarrige (1989), cows with a peak milk yield of 30 –35 kg/day can tolerate an average energy deficit of 2.5 UFL/d over the first 7 – 8 weeks of lactation with most of this occurring in the first 3 –5 weeks. This would suggest that cows on C in this study had too high an energy deficit with an average NEB of 3.6 UFL/day over the first 8 weeks of lactation compared to an NEB of 2.0 and 2.5 UFL/day for SS and S respectively. The degree of NEB decreased as cows progressed from week 1 to week 8 of lactation even though at this stage, all treatments were still in NEB. This trend is similar to that found by Sutter and Beever (2000) for animals offered a hay based diet where NEB declined from a maximum of 63.8 MJ of ME/day in the first week of lactation to 20.7 MJ of ME/day in week 8 of lactation. 4.1.3. Blood metabolites Plasma glucose concentrations remain stable or increase slightly during the pre-partum transition period, increase dramatically at calving and then decrease immediately after calving (Kunz et al., 1985; Vazquez-An˜on et al., 1994). Glucose concentration should remain above 3 mmol/l according to Whitaker et al. (1983). Chamberlain and Wilkinson (1998) suggested that glucose was a suitable metabolite for assessing animal energy status but the current results would not support this where pre-calving diet had no significant effect on plasma glucose concentrations, either at calving or post-calving despite significant differences in EB. Whitaker (1997) suggested that glucose was not as sensitive as NEFA or BHB to changes in EB.
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The desired plasma concentration for NEFA is below 0.7 mmol/l for cows in early lactation and below 0.4 mmol/l towards the end of pregnancy (Whitaker et al., 1983). The concentrations measured in this study were within these targets. Cows receiving concentrates pre-calving had significantly higher plasma NEFA concentrations at week 8 post-calving compared with the other treatments and had numerically higher NEFA concentrations than cows on SS at week 2 post-calving. This could be a reflection of the greater tissue mobilisation on this treatment. Plasma NEFA concentrations decrease after calving (Grummer, 1995), which was the trend observed in the present study. In the current study the correlation coefficients between NEFA concentrations at week 2 post-calving and NEB level averaged over the first 4 weeks of lactation (r ¼ 0:05) and the NEB level at week 2 (r ¼ 0:04) were not significant suggesting that NEFA also was not a very accurate indicator of NEB in early lactation in this study. The optimum concentration of BHB for lactating cows is below 1 mmol/l in early lactation and below 0.6 mmol/l for cows at the end of pregnancy (Whitaker et al., 1983) and the concentrations found in the present study were within those targets. In general the trends in plasma BHB concentrations found in this study agree with those of Kunz et al. (1985) who observed that postpartum plasma BHB concentrations were higher in cows fed generously compared to those fed at restricted levels pre-partum. There was a negative correlation of r ¼ 0:29 (P < 0:05) between BHB concentrations at week 2 post-calving and the NEB levels averaged over the first 4 weeks of lactation. At 2 weeks post-calving cows on C had significantly higher plasma BHB concentrations than those on SS. This would be consistent with the greater loss of LW and BCS post-calving observed for these cows (0.58 kg/day and 0.18 kg/day live weight change and 0.26 and 0.02 units of BCS change in the first 8 weeks of lactation on C and SS, respectively—McNamara et al., 2003) indicating greater mobilisation of body fat. These results suggest that BHB may be a more useful indicator of EB and also of BCS and LW loss than either glucose or NEFA. The lower plasma urea concentrations at calving for the cows supplemented with concentrates compared to those on silage alone may reflect a greater capture of N in the rumen due to the enhanced rumen
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fermentable energy supply from the concentrates. The differences between pre-calving treatments in plasma urea concentrations at week 8 post-calving were surprising especially since no such differences were observed at week 2 post-calving. Plasma protein concentrations were higher at week 2 and 8 after calving in the cows that received C before calving which may reflect a better protein status. 4.1.4. Fertility performance Pre-calving diet and nutrition have been reported to affect subsequent reproductive performance (Whitaker et al., 1993) although no significant effects could be detected in the current study. Flipot et al. (1988) reported that cows on the highest ED diet pre-partum had the longest calving to conception interval; however they found no differences in calving to first oestrus or services per conception. Results from Johnson and Otterby (1981) found that improving pre-partum diet had no significant effect on calving to conception interval or on services per conception. However, the fact that no significant effects were detected in the current study has to be interpreted cautiously because of the relatively low number of animals per treatment but the results are supported by the findings of Keady et al. (2001) who stated that concentrate supplementation in late gestation had no beneficial effects on subsequent fertility. In the current study no significant differences in EB in the first 8 weeks of lactation were found between cows that conceived to first service or a subsequent service with those that did not conceive. According to Butler and Smith (1989) the most likely nutritional factor to influence fertility is EB in early lactation particularly at the time of first service. A possible reason for the absence of a detrimental effect of NEB in early lactation on fertility in the present study may be the longer than normal calving to service interval. This arose because the experimental cows were the earlier calving spring cows in the herd. 4.2. Effect of post-calving diets 4.2.1. NE intake, milk energy output and energy balance Post-calving diet had a significant effect on postcalving NE intake in the first 8 weeks of lactation. This was a consequence of the greater DM intake on
the HC compared to the LC treatment (mean of 15.1 vs. 12.6 kg/cow per day—McNamara et al., 2002). NE intake was, on average, 26% greater over the first 8 weeks of lactation on HC compared to LC treatment. On both treatments, NE intake increased from calving and reached its maximum at about week 3 on LC and at week 4 on HC. Milk energy output was, as expected, higher on the more energy dense HC diet. EB was most negative on LC but its severity declined for both treatments as week of lactation increased. Butler et al. (1981) found that cows reached positive balance by day 80 post-calving on average. VillaGodoy et al. (1988) stated that greater than 50 days post-calving would be required for cows to reach positive balance. The results from the present study would support these findings. 4.2.2. Blood metabolites Plasma indicators of energy and protein status would be expected to reflect the greater mobilisation of body tissue as indicated by the greater NEB in LC compared to the HC. Plasma BHB concentrations were higher on LC compared to HC at week 2 postcalving but the difference was not significant. However, glucose concentrations were higher on HC at week 2 post-calving and were also higher but not significantly so (P ¼ 0:08 ) at week 8 post-calving. This confirms an enhanced energy status for those animals on HC. The lower plasma urea concentration on HC compared to LC at week 2 post-calving reflected the lower grass silage intake (McNamara et al., 2003) and greater rumen fermentable energy intake from concentrates on this treatment. 4.2.3. Fertility performance A significant decline in the calving rate to first service of approximately 0.9% per annum has been observed in Irish dairy herds between 1991 and 1998 (Mee et al., 1999). It has been suggested that early lactation NEB may be the underlying causative factor in the association between increased milk output and declining reproductive performance (Butler and Smith, 1989; Nebel and McGilliard, 1993; Macmillan et al., 1996). However, in this study no effect of postcalving concentrate supplementation level on reproductive performance could be detected, despite significant differences in NEB being observed. The number of animals per treatment was a limiting factor
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in detecting significant differences but no strong trends indicating an association between greater NEB and poorer fertility performance were observed.
5. Conclusions Good quality grass silage alone is not adequate to maintain cows in positive energy balance in the final 4 weeks of gestation. Increasing the ED of the diet precalving increased the NE intake and decreased the NEB pre-calving. Cows supplemented with concentrates pre-calving were in positive EB until calving but then experienced the greatest degree of NEB in the first 8 weeks of lactation. Blood metabolites did not appear to be good indicators of EB either before or after calving. Supplementing with a higher level of concentrates after calving reduced NEB but did not eliminate it. No significant differences in reproductive performance were detected despite significant differences in EB being observed between treatments.
Acknowledgements The authors would like to thank Mr. Noel Byrne and farm staff, Mr. Joe Dwyer, Ms. Justine Haugh and Ms. Norann Galvin for skilled technical assistance and Dr. Dermot Harrington for statistical advice. Funding from Irish dairy farmers is gratefully acknowledged.
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