Influence of feeding accuracy on the performance of Aberdeen Angus×Ayrshire and Charolais×Ayrshire crossbred suckler cows and their progeny

Livestock Production Science 85 (2004) 65 – 79 www.elsevier.com/locate/livprodsci

Influence of feeding accuracy on the performance of Aberdeen Angus
Ayrshire and Charolais
Ayrshire crossbred suckler cows and their progeny M. Manninen a,*, J. Taponen b b

a MTT Agrifood Research Finland, North Savo Research Station, FIN-71750 Maaninka, Finland University of Helsinki, Department of Clinical Veterinary Sciences, Pohjoinen pikatie 800, FIN-04920 Saarentaus, Finland

Received 14 November 2002; received in revised form 18 March 2003; accepted 1 April 2003

Abstract Thirty-two Aberdeen Angus – Ayrshire cows (AbAy), initial live weight (LW) 425 kg in experiment 1 and 506 kg in experiment 2, and 32 Charolais – Ayrshire cows (ChAy), initial LW 450 kg in experiment 1 and 551 kg in experiment 2, were selected for the two experiments. At the onset of experiment 1, the animals were first-calf heifers pregnant to an Ab bull and in experiment 2 second-calf cows pregnant to a Hereford bull. In both experiments, four treatments in a 2
2 factorial arranged design consisted of the two breeds and two feeding accuracies (accurate and inaccurate; A and IA). In experiment 1, the day-today variation in the roughage offered ranged up to F 40%. In experiment 2, the same variation was used in 2-week periods. Forage consisted of grass silage and hay, additionally straw in experiment 2. Milled barley was offered to the cows pre- and post-partum. The objective was to study the effects of treatments on cow feed intake, live weight, body condition, milk production, dystocia, fertility and calf performance. In addition, the achieved feeding level for non-mature beef – dairy crosses was evaluated. In experiment 1, the AbAy and ChAy cows received daily during the entire indoor period an average 73.1 and 81.6; in experiment 2, 89.1 and 92.2 MJ ME, respectively. In both experiments, variation of roughages offered had only minor effects on cow performance. Reproduction was not affected by the feeding accuracy. Treatments had no effect on milk production, which averaged 10.8 and 12.6 kg/day in experiments 1 and 2, respectively. The milk protein content of the ChAy cows was higher ( P < 0.01) than that of the AbAy cows (exp. 1: 32.7 vs. 31.0 g/kg; exp. 2: 31.9 vs. 29.3 g/kg). The dystocial cases observed were not related to the treatments. In experiment 1, calves on diet IA tended to grow better pre-weaning than those on diet A ( P = 0.08, 1325 vs. 1296 g/day). In both experiments, live weight gain pre-weaning was better for males than for females (exp. 1: 1398 vs. 1224 g/day, P < 0.05 and exp. 2: 1453 vs. 1295 g/day, P < 0.05). Accurate feeding is not necessary for young beef – dairy crosses if the total amount of feed, and thus energy offered over a period of a few weeks, is adequate to fulfil the energy requirements. The amount of energy offered for both types of non-mature crossbred cows proved to be sufficient on the basis of the performance data. D 2003 Elsevier B.V. All rights reserved. Keywords: Feeding accuracy; Beef; Body condition; Milk; Reproduction

* Corresponding author. Tel.: +358-3-41883642; fax: +358-3-41883661. E-mail address: [email protected] (M. Manninen). 0301-6226/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0301-6226(03)00120-9

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1. Introduction Ruminant feeding technique is a widely reported research subject, particularly the effects of feeding frequency on milk production, beef production and beef cow production. Feeding accuracy and the accuracy requirements for ruminant feeding, however, have been studied in only a few experiments. Wiktorsson and Knutsson (1977) observed in dairy cows that a F 15% day-to-day variation in concentrate supply was followed by a 4% reduction in milk production. The variation in feed intake also had a marked effect on fertility. Only slightly negative effects were observed when growing bulls were fed concentrates with F 30% day-to-day variation and grass silage ad libitum (Aronen, 1991). Some inaccuracy in concentrate feeding and daily variation of nutrient supply may be acceptable if good quality roughage is available ad libitum and only small amounts of concentrates are fed. The accuracy requirement may be stricter, if restricted amounts of roughage are fed. In another experiment by Aronen (1992), inaccurate concentrate feeding ( F 15%, F 30%, F 45%) of growing Finnish Ayrshire bulls indicated that the rumen cellulolytic microbes tolerate some variation in feed supply. Furthermore, no differences in feed intake, diet digestion or animal performance were observed. Soto-Navarro et al. (2000) studied the effects of feeding frequency (1
or 2
daily) and 10% fluctuation in a day-to-day feed intake on digestion and ruminal fermentation in crossbred steers. Their results indicated that the total tract digestibility of organic matter, nitrogen and starch were lower when feed was offered twice daily with a 10% fluctuation in intake. The response of mature or non-mature suckler cows to changes in feeding accuracy is less defined and thus the above results may not apply to suckler cows. In addition, the importance of feeding accuracy may be emphasized during the long indoor feeding period in Finland. In practice, suckler cows are generally fed as a group with restricted amounts of roughage. Strictly accurate allotment of feed can seldom be achieved and thus may be unrepresentative of practical feeding conditions. The aim of the two experiments presented here was to study the effects of feeding accuracy of roughage on the performance of non-mature Aberdeen Angus – Ayrshire (AbAy)

and Charolais –Ayrshire (ChAy) crosses during indoor feeding and grazing. In experiment 1, the influence of feeding accuracy on the performance of AbAy and ChAy cows was studied by a random daily variation of roughage by up to F 40%. Experiment 2 was conducted to assess the effects of feeding accuracy on the performance of the same crosses with a random 14 days variation of roughage by up to F 40%. The achieved feeding level of nonmature beef –dairy crosses during the indoor feeding period was also evaluated. The effects of treatments during the experiments on cow feed intake, live weight, body condition, milk production, dystocia, fertility and calf performance are discussed in this paper.

2. Materials and methods 2.1. Animals and experimental design Two experiments were carried out during 2 successive years at Tohmaja¨rvi Research Station located in Eastern Finland (62j14V N, 30j21V E). The average vegetation growth period at Tohmaja¨rvi is 155 days (base temperature + 5 jC) and grazing period 100 – 120 days. Thirty-two AbAy cows, with initial live weight (LW) of 425 kg on 16th October in experiment 1 and 506 kg on 22nd October in experiment 2, and 32 ChAy cows, with initial LW of 450 kg in experiment 1 and 551 kg in experiment 2, were selected for the experiments. Animals of both breeds at the onset of experiment 1 were immature, firstcalf heifers and pregnant to an Ab bull. At the onset of experiment 2 the animals were second-calf cows and in calf to a Hereford (Hf) bull. In both experiments, four treatments in a 2
2 factorially arranged design consisted of the two previously described breeds (AbAy, ChAy) and two feeding accuracies (accurate, A; inaccurate, IA). Predicted calving date (gestational age assessed by ultrasonographic fetometry) and initial LW were used to allocate animals to treatments. The animals were group-fed, once daily in the morning, six to eight animals per pen and two pens per treatment. Each pen contained animals of one breed. Experiment 1 and experiment 2 consisted of

M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

two main periods, an indoor feeding period averaging 216 and 227 days, respectively, and a grazing period averaging 119 and 101 days, respectively. The indoor feeding comprised three periods: from the start to the beginning of additional concentrate feeding (116 and 92 days in experiments 1 and 2, respectively), additional concentrate feeding pre-partum (62 and 61 days) and post-partum before the grazing season (38 and 74 days). Details of the animal housing facilities have been documented previously (Manninen et al., 1998). 2.2. Feeds, feeding, feed sampling and grazing 2.2.1. Forages and grazing In both experiments, oats – Italian ryegrass (Avena sativa – Lolium multiflorum L.) bi-crop and meadow fescue – timothy (Festuca pratensis – Phleum pratense) grass silages were harvested with a flail harvester and ensiled in bunker silos with an acid-based additive, applied at 4 – 5 l/t of grass. In addition, meadow fescue – timothy hay and oat straw were harvested and baled. The forage consisted of silage and hay in experiment 1 with additional straw in experiment 2. In experiment 1, silage and hay were offered in the proportions 0.7 and 0.3 and in experiment 2 in the proportions 0.5, 0.3 and 0.2 (straw) on a dry matter (DM) basis. In experiment 1, milled barley was offered individually to all cows at 1.0 pre- and 2.5 kg/day post-calving. The corresponding values for experiment 2 were 1.5 and 3.0 kg/day. During indoor feeding in both experiments, cows received a mineral mixture rich in phosphorus, salt lick and water. A vitamin mixture was given weekly. The pasture consisted of a meadow fescue – timothy sward which was rotationally grazed, with an area of 57.4 hectares in experiment 1 and 58.4 hectares in experiment 2. Cows had free access to water and a magnesium-rich mineral mixture. Calves were creepfed on pasture milled barley 30 (exp. 1) and 37 (exp. 2) days before weaning in order to facilitate adaptation to the post-weaning diet. 2.2.2. Accuracy During feeding at 07:30 h, the cows were tied for 2 – 3 h to allow them an equal opportunity to consume the feed offered. The amount of feed

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offered and refused was recorded for each group daily. In experiment 1, animals fed diets A and IA were given equal amounts of roughage during the course of one feeding period of 28 days, but with a random daily variation of F 40% around the calculated mean for the animals on diet A. In experiment 2, A- and IA-fed animals were given equal amounts of roughage during the course of one feeding period of 28 days, but with a random 14 days variation of F 40% around the calculated mean for the animals on diet A. In both experiments, feed was offered according to Finnish recommendations which were based on those for dry dairy cows (Salo et al., 1982) documented as LW0.75/5000.75
4.0 fattening feed units (FFU) for maintenance and 0.4 FFU/kg fatcorrected milk for milk production. The feed evaluation system changed in Finland from a net energybased system to a metabolizable energy (ME)-based system after the present experiments were planned and thus the results are calculated and reported according to the present ME-based system (Tuori et al., 1996). 2.2.3. Analyses During the indoor period, feed samples for chemical analyses were taken at every feeding and pooled over a 4-week period. In experiment 1, the silage samples were pooled over a 2-week period. Silage DM content was determined by oven drying at 105 jC for 16 h and was corrected for volatile losses (volatile fatty acids, ammonia, lactic acid) according to Huida et al. (1986). Fresh silage samples were analysed for pH, water-soluble carbohydrates by the method of Somogyi (1945), lactic acid (Haacker et al., 1983), volatile fatty acids (Huida, 1973), ammonia nitrogen (N) (McCullough, 1967) and soluble and total N by the Kjeldahl method. Feed samples were analysed for organic matter (OM) by ashing at 600 jC for 16 h and neutral detergent fibre (NDF) according to Van Soest et al. (1991). The energy contents of grass silage, hay and straw were evaluated using in vitro OM digestibility (Friedel, 1990). The feed value of barley was calculated using the determined chemical composition and average digestibility coefficients reported by Tuori et al. (1996) and ME values were calculated according to MAFF (1975, 1984). Amino acids absorbed in the small intestine (AAT) were calculated according to Tuori et al. (1996).

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2.3. Live-weight, condition scoring and dystocia Cows were weighed at the beginning of the experiment, 60 days prior to the estimated calving date, 1 – 7 days pre-partum, within 48 h after parturition and at the beginning and end of the grazing season. In experiment 2, cows were weighed 12 days prior to the onset of grazing due to a shortage of experimental feed and this weight was used as the LW at the onset of grazing. Cows were condition-scored (Lowman et al., 1976) at the beginning of the experiment, 60 days before estimated calving, at calving as well as at the beginning, in the middle and at the end of the grazing season. Data from three (exp. 1) and one (exp. 2) cows on diet A, and one (exp. 1) and two (exp. 2) cows on diet IA were omitted due to uterine inflammation, stillbirth and twinning. However, the cows were included in the pregnancy rates, when possible. Calves were weighed immediately after birth, at 50 and 100 days of age and at the beginning and end of grazing, the last also representing the weaning weight. In experiments 1 and 2, data from twins and stillborn calves were omitted. Only weights from birth to age 50 days were available for the calf of the dam (ChAy, diet A) which died for unknown reason 67 days postcalving. All calvings were monitored and assistance was provided as described by Manninen et al. (2000). 2.4. Milk production and fertility In both experiments, milk production was measured for six cows from each treatment group using the machine-milking technique. The milk yield was measured on 14, 28, 42, 56, 70, 84, 98, 112, 126, 140 and 154 (exp. 2) days of lactation. The cows selected for assessing milk production were primarily the first six cows on a calving date basis per treatment, taking into account the sex of the calf. The cow and progeny were removed from the main group and the calf was separated from the dam. The cows were milked at 12:00, 18:00, 06:00 and at 12:00 h. The aim of the first milking was to empty the udder and use the sum of the last three milkings as an estimate of milk production. At every milking, the animals were given 15 I.U. of oxytocin (SYNOXR 5 I.U./ml, Orion Pharma, Orion, Espoo, Finland) intramuscularly to ensure complete emptying of the udder. Milking was

started 5 min post-injection. During milking the calf was kept in front of the dam. After milking, the milk collected was given to the calf. Milk samples were collected during the last three milkings and pooled according to yield and analysed in the laboratory of Valio for fat, protein and lactose using a Milcoscan 605 infrared analyser (Foss electric, Hillerød, Denmark) and also for urea using a Seralyser photometer. In experiment 1, two Hf bulls ran with the cows from 22nd May to 26th August. Ultrasonographic examinations were performed on 12th August and 7th October for assessing the status of pregnancy and gestational age. In experiment 2, two Limousin (Li) bulls ran with the cows from 3rd June to 26th August. Ultrasonographic examinations were performed on 18th August and 13th October. A real-time B-mode ultrasound scanner (Aloka SSD-210DX, Aloka, Japan) equipped with a 5.0 MHz rectal linear array transducer was used for ultrasound examinations. Gestational age was assessed by ultrasonographic fetometry based on measurements of fetal diameter of the external braincase or crown – rump length. Gestational age and thus date of conception were calculated according to Ka¨hn (1989). Resumption of ovarian activity and subsequent ovarian function were assessed with progesterone (P4) profiles. Samples of whole milk for P4 determinations were collected in plastic tubes containing a tablet of bronopol from six cows from each treatment group, 24 altogether, in both experiments. The animals were different from those that were included in measurements for milk production. The samples were taken from each quarter after the morning milking. The first sample was collected 3 weeks after calving and once weekly thereafter until three successive high values of P4 ( z 15 nmol/l) were obtained. The samples were sent immediately to a commercial milk progesterone laboratory (Valio) where the concentrations of P4 were measured by use of a commercial kit (Spectria, Veterinary Progesterone, Orion Diagnostica, Orion, Espoo, Finland) according to Andresen and Onstad (1979) and Claus and Rattenberger (1979). The day of the first ovulation, and thus the day of resumption of ovarian activity, was assessed according to the following directions. In general, the P4 value was considered low when the concentration was below 9 nmol/l and high when the concentration was above 15 nmol/l. If the first elevated value was z 15

M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

nmol/l, the day of ovulation was estimated to be the day of the last low value. If the first elevated value was between 9 and 15 nmol/l, the day of ovulation was estimated to be 4 days after the day of the last low value. 2.5. Statistical analysis The GLM procedure of the Statistical Analysis System (SAS, 1999) was used to perform the analysis of variance. The animals were penned with six to eight animals per pen and two pens per treatment, and therefore, each pen was used as an experimental unit (Gill, 1989). Individual cow and calf data were used for testing cow and calf performance and milk production. Data for cows were analysed according to the following model: yijkl ¼ l þ bi þ dj þ bdij þ pk ðbdij Þ þ eijkl where yijkl was the response variable, l the general mean, bi the feeding accuracy, dj the breed, bdij their interaction, pk a normally distributed random effect due to the pen within the treatment and eijkl the residual error term. In the analysis, the pk ðbdij Þ term with four degrees of freedom was used as an error term. Data for the calves were analysed using the same model with the exception that the effect of sex ðsm Þ and interactions between sex and feeding accuracy, sex and breed, and sex, feeding accuracy and breed were included as fixed effects. In this analysis, the normally distributed pk ðbdsijm Þ term with eight degrees of freedom was used as an error term for previous sex-related fixed effects while the pk ðbdij Þ term was used as an error term for the effects of feeding accuracy, breed and their interactions. Calf birth dates were used as a covariate in the model when interpreting calf performance data.

3. Results 3.1. Chemical composition of feeds and feed intake The chemical composition and feed value of the experimental feeds are presented in Table 1. The field-

69

Table 1 Mean chemical composition of experimental feeds

Chemical composition Dry matter (DM, g/kg) Exp. 1 Exp. 2 In the DM (g/kg) Ash Exp. 1 Exp. 2 Crude protein Exp. 1 Exp.2 Crude fibre Exp. 1 Exp. 2 NDF Exp. 1 Exp. 2 Feed value, (/kg DM) ME, MJ Exp. 1 Exp. 2 AAT, g Exp. 1 Exp. 2

Grass silage Hay

Oat straw Barley

226 214

866 867

870

861 865

73 54

56 40

58

25 22

134 124

115 83

38

140 130

257 305

307 348

403

48 58

520 575

699

11.4 11.2 85 81

ND

9.4 9.3 81 73

750

6.9

54

13.1 13.2 105 105

NDF, neutral detergent fibre; ND, not determined; ME, metabolizable energy; AAT, amino acids absorbed in the small intestine. In silage: pH 4.06 (exp. 1), pH 3.94 (exp. 2). In DM (g/kg): lactic acid 42 (exp. 1) and 44 (exp. 2), acetic acid 17 (exp. 1 and exp. 2), butyric acid 1 (exp. 1) and 2 (exp. 2), ethanol 10 (exp. 1) and 8 (exp. 2), water-soluble carbohydrates 103 (exp. 1) and 64 (exp. 2). In total nitrogen (g/kg): ammonia N 34 (exp. 1) and 44 (exp. 2), soluble N 518 (exp. 1) and 613 (exp. 2).

dried meadow fescue – timothy hays used in the present experiments had a fairly low protein content, particularly in experiment 2, but despite this the energy content was average. In experiment 1, the proportion of oats – Italian ryegrass silage was 69% and in experiment 2 it amounted to 33% of the total quantity of silage used. The average daily nutrient intakes during the indoor feeding period are summarized in Table 2. In experiment 1, the total DM and ME daily intake was 6.76 kg and 73 MJ for the AbAy cows and 7.55 kg and 82 MJ for the ChAy cows. However, cows fed diet A received significantly more ( P < 0.05) DM than those fed diet IA (7.20 vs. 7.11 kg DM). The feeding accuracy did not have any significant effect on the intake of ME, OM or crude protein (CP). The ChAy

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Table 2 Mean daily intake of dry matter (DM), energy (metabolizable energy, ME), amino acids absorbed in the small intestine (AAT), crude protein (CP) and organic matter (OM) of crossbred cows during indoor feeding Breed

AbAy

Accuracy

Accurate

Number of groups DM intake, kg Grass silage Exp. 1 Exp. 2 Hay Exp. 1 Exp. 2 Oat straw Exp. 1 Exp. 2 Barley Exp. 1 Exp. 2 Total DM Exp. 1c Exp. 2d OM, kg Exp. 1 Exp. 2 ME, MJ Exp. 1 Exp. 2 CP, g Exp. 1 Exp. 2 AAT, g Exp. 1 Exp. 2

S.E.M.a

ChAy Inaccurate

Accurate

Inaccurate

Significanceb Breed

Accuracy

Interaction

0.004 0.000

*** ***

***

* **

1.93 2.61

0.011 0.014

*** ***

**

1.63

0.91

0.030

0.65 1.15

0.64 1.07

0.62 1.06

0.016 0.009

**

6.79 8.99

6.72 8.39

7.60 9.40

7.49 8.62

0.031 0.043

*** **

* ***

6.20 8.57

6.18 8.01

6.95 8.95

6.89 8.22

0.025 0.041

*** **

***

0.33 0.34

*** ***

***

2

2

2

2

4.23 3.76

4.23 3.81

4.83 3.99

4.82 4.04

1.74 2.54

1.72 2.45

1.97 2.71

1.56

0.99

0.67 1.13

73.2 91.1

72.9 87.1

81.9 94.9

81.2 89.5

***

862 887

859 863

965 925

957 891

3.0 2.5

*** ***

***

570 693

568 660

638 721

631 677

2.6 2.7

*** **

***

a

Standard error of means. *P < 0.05; **P < 0.01; ***P < 0.001. c Including mineral mixture. d Not including mineral mixture. b

cows consumed on average 11.7% more DM and ME than the AbAy cows. In experiment 2, cows fed diet A had significantly higher ( P < 0.001, 9.19 vs. 8.51 kg) DM intake than those overwintered on diet IA. On the other hand, cows on diet IA consumed more ( P < 0.001), although numerically not much, silage DM than those on diet A (3.93 vs. 3.87 kg). However, the DM intake from hay was lower ( P < 0.01) on diet IA than on diet A (2.53 vs. 2.62 kg DM). The most remarkable effect of the feeding accuracy was observed in the DM intake of straw, since the cows fed diet A consumed on average 0.64 kg more ( P < 0.001) than those fed diet IA. Cows fed diet IA could not consume all the straw offered on

days when given considerably more feed than those on diet A. The total DM and ME intakes were 8.69 kg and 89 MJ for AbAy and 9.01 kg and 92 MJ for ChAy cows, respectively. In experiment 2, the ChAy cows received 3.6% more DM and ME than the AbAy cows. At pasture, the creep-fed barley intake of calves was on the average 0.60 and 0.49 kg/day in experiments 1 and 2, respectively. 3.2. Live weight, condition score and dystocia of cows In experiment 1, the feeding accuracy had no effect on cow LW or cow body condition (Table 3). During the indoor feeding period the AbAy cows had a live

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Table 3 Live weight (LW), LW gain (LWG), body condition (BC) and change of BC of cows during indoor feeding and grazing Breed

AbAy

Accuracy

Accurate

Exp. 1, n 15 Exp. 2, n 16 LW, kg Initial Exp. 1 427 Exp. 2 504 Onset of pre-partum concentrate feeding Exp. 1 506 Exp. 2 554 Pre-partum Exp. 1 549 Exp. 2 604 Post-partum Exp. 1 488 Exp. 2 539 Onset of grazing Exp. 1 467 Exp. 2 493 End of grazing Exp. 1 512 Exp. 2 532 LWG, g/day Indoor Exp. 1 184 Exp. 2  48 At pasture Exp. 1 381 Exp. 2 341 BC Initial Exp. 1 3.11 Exp. 2 3.00 Onset of pre-partum concentrate feeding Exp. 1 3.00 Exp. 2 2.84 Calving Exp. 1 2.78 Exp. 2 2.68 Onset of grazing Exp. 1 2.57 Exp. 2 2.57 End of grazing Exp. 1 2.72 Exp. 2 2.73 Change of BC Indoor Exp. 1  0.54 Exp. 2  0.43 At pasture Exp. 1 0.15 Exp. 2 0.16 a

S.E.M.a

ChAy Inaccurate

Accurate

Inaccurate

Significanceb Breed

Accuracy

16 16

14 16c

15 14

423 508

449 551

451 552

4.4 5.0

** ***

495 546

549 610

532 591

5.8 3.6

** ***

*

538 589

600 654

581 633

8.5 5.6

** **

*

479 523

535 587

518 569

7.5 4.7

** ***

*

456 480

516 560

506 530

9.2 5.4

** ***

*

516 538

562 594

553 582

4.6 7.5

*** **

155  132

306 42

253  104

32.5 8.6

* **

506 499

390 371

398 505

55.1 26.5

3.03 3.13

2.84 2.82

2.95 3.21

0.058 0.093

2.90 2.82

2.77 2.64

2.80 2.75

0.074 0.072

2.69 2.58

2.55 2.43

2.61 2.46

0.066 0.046

2.42 2.37

2.45 2.60

2.49 2.41

0.115 0.106

2.70 2.67

2.62 2.62

2.74 2.51

0.085 0.116

 0.61  0.76

 0.39  0.22

 0.46  0.80

0.065 0.059

0.28 0.30

0.17 0.02

0.25 0.10

0.043 0.089

***

Interaction

*

**

*

*

**

Standard error of means. Exp. 1: these means were based on 16 (AbAy – IA) or 14 (ChAy – A) rather than 15 observations and the S.E.M. given should be multiplied by 0.9661 (AbAy – IA) or 1.0435 (ChAy – A) when making comparisons with other means. Exp. 2: this mean was based on 14 (ChAy – IA) rather than 16 observations and the S.E.M. given should be multiplied by 1.0690 (ChAy – IA) when making comparisons with other means. One cow died on 24th May. After that date these means were based on 15 (ChAy – A) or 14 (ChAy – IA) rather than 16 observations and the S.E.M. given should be multiplied by 1.0351 (ChAy – A) or 1.0690 (ChAy – IA) when making comparisons with other means. b *P < 0.05; **P < 0.01; ***P < 0.001. c One cow died on 24th May, after that n = 15.

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more condition ( P = 0.07, 0.26 vs. 0.16) than A-fed cows at pasture. Three calvings were classified with value 4 (very difficult calving requiring veterinarian assistance or caesarean section) in experiment 1. The causes of the dystocial cases were prolonged pregnancy with oversize fetuses (47.5 and 44.0 kg) and faulty disposition. The six calvings classified with value 3 (difficult calving) had no records except extra assistance. In experiment 2, the effects of feeding accuracy on cow LW and LWG were more pronounced than those observed in experiment 1. Already at the onset of prepartum concentrate feeding, the cows fed diet A were significantly ( P < 0.05) heavier than those fed diet IA (582 vs. 569 kg). The cows on diet A were heavier

weight gain (LWG) of 169 g/day and the ChAy cows 280 g/day ( P < 0.05), the cows fed diet A 245 g/day and the cows fed diet IA 204 g/day ( P > 0.10). However, at pasture the LWG was similar ( P > 0.10) for all cows, averaging 420 g/day. At the onset of prepartum concentrate feeding, cows fed diet A tended ( P = 0.07) to be heavier than those fed diet IA (528 vs. 513 kg). The observed changes in cow LW and LWG were analogous to the findings in the cow condition score and changes in the condition score. The initial condition score of the ChAy cows was lower ( P < 0.05) than that of the AbAy cows (2.89 vs. 3.07). At the onset and end of the grazing season there was no significant difference in cow condition between the breeds. Cows fed diet IA tended to gain

Table 4 Mean treatment and sex effects on calf performance Breed exp. 1

Ab
AbAy

Ab
ChAy

S.E.M.a

Significanceb

Breed exp. 2

Hf
AbAy

Hf
ChAy

Min – max

Breed

Accuracy

Accurate

Sex

Male

Female

9 6 Exp. 1, n 8 8 Exp. 2, n Average calving dated 106 91 Exp. 1 77 86 Exp. 2 Live weight, kg At birth 39.6 36.3 Exp. 1 48.3 44.8 Exp. 2 50-day 103 89 Exp. 1 122 104 Exp. 2 100-day 171 144 Exp. 1 195 168 Exp. 2 Onset of grazing 83 73 Exp. 1 152 131 Exp. 2 At weaning 260 220 Exp. 1 314 244 Exp. 2 Live weight gain, birth ! weaning, g/day 1403 1184 Exp. 1 1528 1262 Exp. 2 a

Inaccurate

Accurate

Male

Male

Female

Female

6 9c

8 7

9 6

6 8

94 77

104 82

104 85

106 86

104 88

114 87

41.4 47.7

41.3 46.2

41.6 45.2

37.2 46.1

6.5 – 10.7 3.5 – 4.3

*

1.28 – 2.13 1.06 – 1.29

98 110

94 107

103 115

96 108

105 111

96 109

1.3 – 2.2 3.0 – 3.7

**

** *

167 177

156 172

175 183

159 173

175 175

159 174

1.9 – 3.1 6.1 – 7.0

*

***

82 136

77 132

91 143

81 133

87 139

81 135

1.8 – 3.0 3.8 – 4.4

*

255 292

232 249

260 304

232 262

264 287

236 249

7.2 – 11.9 14.0 – 16.3

** **

1389 1420

1235 1300

1381 1475

1215 1308

1418 1389

1260 1310

49.1 – 81.5 59.9 – 69.5

* *

Standard error of means. *P < 0.05; **P < 0.01; ***P < 0.001. c n = 9 for birth weight and 50-day weight, then n = 8. d Day 1 = 1st January. b

Male

8 8

38.0 44.7

Sex

Inaccurate Female

8 8

37.4 45.3

Accuracy

*

** *

M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

( P < 0.05) pre- and post-partum and at the onset of grazing than those on diet IA (629 vs. 611 kg, 563 vs. 546 kg, 527 vs. 505 kg). During the indoor feeding period cows fed diet A had a LWG of  3 g/day and cows fed diet IA  118 g/day ( P < 0.001). However, at pasture the cows overwintered on diet IA had a 146 g/day better ( P < 0.01) LWG than those on diet A. After the grazing season there were no differences in LW between feeding accuracies. At the onset of experiment 2, cows on diet IA tended ( P = 0.05) to have a better condition than those on diet A (3.17 vs. 2.91). Thereafter no differences were observed in the condition score between feeding accuracies. During the indoor feeding period cows fed diet IA lost significantly ( P < 0.01) more condition than those fed diet A (  0.78 vs.  0.32) but compensated well for the losses at pasture. The AbAy cows were in better ( P < 0.05) condition at calving than the ChAy cows (2.63 vs. 2.45). After the grazing season the AbAy and ChAy cows had average condi-

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tion scores of 2.70 and 2.56 ( P > 0.10), respectively. One calving was classified with value 3 due to a faulty disposition. 3.3. Live weight of calves In experiment 1, the treatments had no effect on calf birth weight which averaged 39.2 kg (Table 4). At the ages of 50 and 100 days and at the onset of grazing the Ab
ChAy calves were 4.3 kg ( P < 0.01), 7.7 kg ( P < 0.05) and 6.1 kg ( P < 0.05) heavier than the Ab
AbAy calves. Dam feeding accuracy affected calf LWG pre-weaning so that calves born to dams fed diet IA tended to grow better than those born to cows on diet A ( P = 0.08, 1325 vs. 1296 g/day). Preweaning LWG was 1303 g/day for the Ab
AbAy calves and 1319 g/day for the Ab
ChAy calves ( P > 0.10). In experiment 2, the treatments had no significant effect on calf birth weight which averaged 46.2 kg.

Table 5 Milk production and milk composition of crossbred suckler cows Breed

AbAy

Accuracy

Accurate 6 6

Exp. 1, n Exp. 2, n Milk yield, kg/day 10.8 Exp. 1 13.5 Exp. 2 Energy-corrected milk yield, kg/day 11.3 Exp. 1 13.6 Exp. 2 Milk composition, g/kg Fat 44.3 Exp. 1 43.0 Exp. 2 Protein 31.4 Exp. 1 29.3 Exp. 2 Lactose 48.3 Exp. 1 48.7 Exp. 2 Urea, mg/100 ml 16.7 Exp. 1 Exp. 2 NDd a

S.E.M.a

ChAy Inaccurate

Significanceb

Inaccurate

Accurate

6 6c

6 5c

6 6

Breed

10.2 12.5

11.2 12.1

10.9 12.3

0.58 0.97

10.6 12.4

12.3 13.1

12.0 12.8

0.69 0.93

44.5 41.4

47.8 46.9

47.5 43.8

1.63 1.08

*

30.6 29.4

32.4 32.8

33.0 31.0

0.36 0.51

** **

49.8 49.6

48.2 49.2

48.9 48.6

0.50 0.53

17.6

19.0

19.1

0.35

ND

ND

ND

Accuracy

Interaction

**

Standard error of means. *P < 0.05; **P < 0.01; ***P < 0.001. c These means were based on six (AbAy – IA) or five (ChAy – A) rather than six observations and the S.E.M. given should be multiplied by 0.9428 (AbAy – IA) or 1.2910 (ChAy – A) when making comparisons with other means. d ND, not determined. b

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M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

Calves born from diet A were at the onset of grazing 4.2 kg ( P < 0.05) heavier than those born from diet IA. LWG pre-weaning was 1393 and 1355 g/day ( P > 0.10) for calves from diets A and IA, respectively. Pre-weaning LWG was 1377 g/day for the Hf
AbAy calves and 1370 g/day for the Hf
ChAy ChAy calves ( P > 0.10). 3.4. Milk production and milk composition In both experiments, feeding accuracy or breed had no effect on the average milk or energy-corrected milk yield (Table 5). In both experiments, the milk protein content of the ChAy cows was higher ( P < 0.01) than that of the AbAy cows (exp. 1: 32.7 vs. 31.0 g/kg, exp. 2: 31.9 vs. 29.3 g/kg). In experiment 2, the milk fat content of the ChAy cows was also higher than that of the AbAy cows ( P < 0.05, 45.4 vs. 42.2 g/kg). The milk urea content was measured only in experiment 1 and was higher for the ChAy cows ( P < 0.01, 19.1 vs. 17.2 mg/100 ml).

3.5. Puerperal anoestrous period and conception The treatments had no significant influence on the length of the puerperal anoestrous period (Table 6). In experiment 1, where the interval from calving to grazing was markedly shorter than in experiment 2, most of the variation in the length of the puerperal anoestrous period was explained by the length of the interval from calving to grazing. In experiment 2, where the average voluntary waiting period (interval from calving to grazing and bull exposure) was 74 days (minimum 59 days), 23 of the 24 cows conceived during the first 3 weeks on pasture. One cow conceived during the second oestrus. In eight cases, the cows conceived during the first oestrus after calving, while in the others, ovarian activity had resumed before the grazing period. In five cases, the first oestrous cycle was shortened. In experiment 1, the average voluntary waiting period was only 30 days, in five cases less than 3 weeks. Despite the short voluntary waiting period, in 22 of the 24 cows,

Table 6 Puerperal anoestrus period of crossbred suckler cows Breed

AbAy

Accuracy

Accurate

6 Exp. 1, n 6 Exp. 2, n Condition score Calving 2.92 Exp.1 2.63 Exp.2 Onset of grazing 2.76 Exp. 1 2.65 Exp. 2 July 3.15 Exp. 1 2.80 Exp. 2 Days Calving ! grazing 37 Exp. 1 76 Exp. 2 Puerperal anoestrus period 52 Exp. 1 3.9 S.E.M. 65 Exp. 2 9.4 S.E.M. a

S.E.M.a

ChAy Inaccurate

Accurate

Inaccurate

Breed

6 6

6 6

6 6

2.82 2.50

2.58 2.30

2.82 2.19

0.099 0.164

2.67 2.53

2.58 2.44

2.43 2.50

0.161 0.201

3.07 2.80

2.91 2.59

2.99 2.66

0.077 0.178

36 76

26 75

22 66

49 3.8 71 8.9

48 3.7 57 9.3

42 4.0 65 12.7

Significanceb

5.8 2.0

Accuracy

Interaction

*

Standard error of means. Exp. 2: these means were based on six (AbAy – IA) or six (ChAy – IA) rather than six observations and the S.E.M. given should be multiplied by 0.9428 (AbAy – IA) or 1.2649 (ChAy – IA) when making comparisons with other means. b *P < 0.05; **P < 0.01; ***P < 0.001.

M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

ovarian activity resumed during the first 3 weeks on pasture. In two cases, the first ovulation occurred 32 and 34 days after the onset of grazing. Although in nine cases the voluntary waiting period was 5 to 7 weeks, ovarian activity did not resume before the onset of grazing. All 24 cows conceived during the first or second oestrus. In two cases, the first oestrous cycle was shorter than normal. In both experiments, all cows that entered the mating period, except one ChAy fed diet A in experiment 2, became pregnant. In experiment 1, the duration from calving to conception was lower for IA-fed cows ( P = 0.10, 61 vs. 67 days). The calving interval was also shorter for IA-fed cows ( P < 0.05, 345 vs. 352 days). Breed had no effect on the duration from calving to conception or on the calving interval. In experiment 2, the treatments did neither affect the duration from calving to conception nor the calving interval.

4. Discussion 4.1. Feed value and feed intake The silages used in the experiments were of good quality in terms of both feed value and fermentation characteristics. The average chemical composition of the experimental feeds was similar in both experiments. This indicates, in addition, that the quality of feeds had no special effects on the feed intake in both experiments. In experiment 1, feeding accuracy had only a minor effect on the daily ME intake, which averaged 77.3 MJ during the entire indoor feeding period. The total DM intake was 1.3% higher for the A- than IAfed cows. Practical feeding occurred without any notable problems during the winter period and only small refusals were collected on some cold days when the day-to-day variation had been highly positive for several consecutive days. In experiment 2, the effects of feeding accuracy on DM and ME intake were considerably evident compared to those observed in experiment 1. Cows receiving diet IA did not consume all the straw and hay offered, which was the reason for the difference in total DM intake between the A and IA diets. On the other hand, the DM intake from grass silage was slightly, only 50 g, higher for the IA-fed cows.

75

Comparisons between other feeding recommendations for beef cows and measured ME intakes in the present experiments are potentially compromised due to differences in feed evaluation systems, length of the indoor feeding period, breeds, feeds and housing conditions. In experiment 1, during the entire indoor feeding period the AbAy cows received daily an average of 73 MJ ME and ChAy cows 82 MJ ME. In the present Finnish feed evaluation system (Tuori et al., 2000) the maintenance energy requirements for dry dairy cows are documented as 8.31 MJ ME + 0.0078
LW, for the 7th, 8th and 9th month of pregnancy, in addition 10.53, 18.72 and 33.93 MJ ME, and 5.15 MJ ME
kg energy-corrected milk for milk production. Compared to these recommendations the AbAy cows in experiment 1 consumed on the average 7.0 MJ and the ChAy cows 13.3 MJ extra ME which the non-mature cows could utilize for LWG. The corresponding values in experiment 2 were 10.8 and 9.7 MJ for the AbAy and the ChAy cows, respectively. The difference in energy intake between the breeds was small in experiment 2 and had only minor effects on animal performance. In both experiments the ME intakes largely agree with the NRC (1984) recommendations for non-mature beef cows. 4.2. Live weight, condition of cows and dystocia In experiment 1, there were practically no differences in LW and condition score between the A- and IA-fed animals. The results observed are in good agreement with the results reported by Aronen (1991), who found no differences in LW, LWG and feed utilization with growing bulls fed concentrate with F 30% daily variation. This was partly due to compensation of the daily variation of nutrient supply by altering the voluntary intake of grass silage. At the onset of experiment 1, the AbAy and ChAy cows had a LW of 425 and 450 kg which could be considered suitable for both types of non-mature, pregnant yearling heifer crosses. At the end of the grazing period the AbAy and ChAy cows were 89 and 107 kg heavier than at the beginning of experiment 1. The main reason for this LWG was that the cows were still growing animals. Both types of crosses had a good condition at the beginning of experiment 1. However, the 2.7 average body condition score at the end of grazing might be slightly too low for young

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animals still growing. The decrease in condition from the middle of July till the end of grazing (3.0 ! 2.7) may result mainly from the good milk production capacity of beef – dairy crosses and from the decrease of both pasture area and grass quality. The response in LW to feeding accuracy was more evident in experiment 2 reflecting the difference in DM intake between A and IA diets. Unlike in experiment 1, before the grazing season the A cows had on the average same LW but the IA cows were 25 kg lighter than at the onset of the experiment. This may suggest that the higher LW on diet A reflected higher straw intake and thus higher rumen content. On the other hand, it can be assumed that the 2-week variation in feeding level was too much for the still nonmature cows who possibly could not compensate the nutrient deficiency, which occurred at the low feeding level by the 2-week overfeeding period. On some exceptionally cold days the freezing of grass silage affected the intake. Although the effects of feeding accuracy on LW were more evident in experiment 2, it had only a marginal effect on the condition score. At the end of the grazing season in experiment 2, the LW was suitable for the AbAy and ChAy crosses but the condition score was slightly too low. From a practical standpoint, in the case of non-mature crosses with a high milk production capacity, to avoid the decrease in condition score, the calves could be weaned earlier or else the cows need extra energy already while on pasture to respond to the increasing energy demands. Although not observed in the present study, creep feeding of calves with concentrates may also have positive effects on the dam condition. In experiment 1, three calvings were classified with value 4 and six calvings with value 3. The causes of the dystocia were not related to the treatments. In practice, in the case of first-calf heifers assistance is probably given more often and quicker to ensure minimal calf losses. In experiment 2, one calving was classified with value 3 due to faulty disposition and eight calvings with value 2 without any detailed information. In the experiment reported by Absher and Hobbs (1968), 2-year-old Ab and Hf heifers required calving assistance, although not significant when tested, in 65.0%, 50.0% and 38.1% of the cases when the feeding level offered was high (4.16 total digestible nutrients, T.D.N.), medium (3.99 T.D.N.) and low (3.24 T.D.N.), respectively.

Those calves were in addition significantly lighter than the calves born in the present experiments. In experiment 1, three AbAy cows had difficulties in accepting the newborn calf and needed extra practical handling during the first post-calving day. In experiment 2, one AbAy cow showed hostile behaviour towards her newborn calf but had no negative signs the day after. The behaviour observed in both experiments may be due mainly to overcare of the calf by the young mother and excessive maternal instincts of Ab animals. 4.3. Live weight of calves The effects of feeding accuracy on calf performance were marginal in both experiments and without any practical importance. The main reason for this finding may be that the milk production was at least sufficient for the calves in both experiments. In experiment 1, the calves on diet IA grew 29 g/day faster ( P = 0.08) pre-weaning than those on diet A. However, the minor effects of feeding accuracy on calf performance were reverse in experiment 2. The average calf LWG pre-weaning in experiment 2 was 1381 g/day, which was 64 g/day better than in experiment 1. This may be due to the difference in sire breed between experiments 1 and 2 (Ab vs. Hf), but also due to the higher milk production capacity of the second-calving cows in experiment 2. The positive effects of the ChAy dam breed on calf LW were observed in experiment 1 but not in experiment 2. Although the dam breed affected the calf LW at some age in experiment 1, finally the LWG pre-weaning was similar for both calf cross types. 4.4. Milk production and milk composition Consistent with the calf performance data, the treatments had no effect on average milk yield, which averaged 10.8 and 12.6 kg/day in experiments 1 and 2, respectively. These values are in good agreement with the results earlier reported by Manninen and Huhta (2001), although they were measured with HfAy and LiAy crosses. The results of experiment 2 indicate clearly that the dam utilizes the body reserves effectively to maintain the milk production. Studies to evaluate the effects of feeding accuracy on the milk production of suckler cows were not available.

M. Manninen, J. Taponen / Livestock Production Science 85 (2004) 65–79

Milk production is an important trait in suckler cows because it influences a major economic trait, weaning weight (Gaskins and Anderson, 1980). This statement agrees well with the results observed in the present experiments. It is also well known that the maximum milk yield occurs between 1 and 3 months post-partum, depending on the balance between the milk potential of the dam and the suckling ability of the calf indicated by live weight, vigour and health. The onset of the grazing season usually increases milk production and thus affects the time of peak milk yield. Results reported by Marshall et al. (1976) indicate that cow size and condition have little effect on the efficiency of cows weaning calves, whereas higher milk production levels estimated through weaning weight are beneficial. 4.5. Conception and puerperal anoestrous period In the present study the animals were in good condition and the LWG was positive in both feeding groups in both experiments. Hence, it was obvious, as also detected, that feeding accuracy did not have any effect on the length of the puerperal anoestrous period. However, feeding accuracy seemed to have some effect on the interval from calving to conception and the calving interval in experiment 1, but not in experiment 2. The target condition score at turn-out has been considered to be 1.5 – 2.0 which is considerably lower than the values achieved in the present experiments 1 and 2. The reproductive efficiency of beef suckler cows is a key component determining herd productivity and of considerable economic significance in a beef herd (Morris et al., 1978). To achieve a target calving interval of 365 days, the cows must conceive within 85 days of parturition. One of the major causes of poor reproductive efficiency in beef suckler cows is an extended interval from calving to first ovulation (puerperal anoestrus) (Stagg et al., 1995). Anoestrus is the major component of post-partum infertility and is affected by several minor factors: season, breed, parity, dystocia, presence of a bull, uterine palpation and carryover effects from the previous pregnancy as well as two major factors: suckling and nutrition (Short et al., 1990). From factors related to nutrition, the condition of the cow and whether she is gaining or losing weight and thus the energy intake, are major

77

determinants of the post-partum interval to the resumption of ovarian activity and oestrus (Inskeep and Lishman, 1979). The most immediate effect of underfeeding or major changes in feeding is a delay in conception and/or a reduction in the pregnancy rate (Petit and Agabriel, 1989). However, body condition at calving is often considered to play a major role in the reproduction of the beef cow because it seems to regulate the length of the post-partum anoestrus (Wiltbank et al., 1962) while the conception of cycling beef cows is usually good. Although suckling and nutrition have been reported to be major factors in determining the length of puerperal anoestrus (Short et al., 1990), grazing, and especially its onset, seemed to have a great influence on the resumption of ovarian activity. This was detected especially in experiment 1, where the interval from calving to grazing was shorter than in experiment 2. Petit and Agabriel (1989) suggested that when calving takes place in late winter, less than 2 months before turn-out, the high level of nutrition usually achieved on spring grass induces rapid return to oestrus and high fertility. It is obvious, however, that grazing may also have some other influence mechanisms on the reproductive functions, because the animals in the present study were in good condition also during the indoor feeding period.

5. Conclusions Day-to-day variation of roughage even by F 40% had only a minor effect on the performance of the first-calf heifers and their progeny. Two-week variation by up to F 40% in the roughage offered had some effect on cow and calf performance but, however, without practical importance. In both experiments, reproduction was not affected by the feeding accuracy. The amount of energy offered during the indoor feeding period for both types of non-mature crossbred cows proved to be suitable on the basis of the performance data. From a practical standpoint, accurate feeding is not needed for young beef – dairy crosses providing that the total amount of feed and thus energy offered, over a period of a few weeks is adequate to fulfil the energy requirements. Therefore, this investigation may be of use for practical farmers to evaluate the feeding scheme and feeding level for

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young beef –dairy crosses in marginal circumstances with a long indoor feeding period. In the present study, however, the amount of energy offered to the cows during the entire indoor period was at least sufficient and, therefore, more studies are needed to quantify more accurately these requirements if the feeding level is below the level used in the present experiments. Acknowledgements The authors are indebted to Mr. Harri Huhta, M.Sc.Agr., Mr. Helge Laamanen, Mrs. Ulla Eronen and their staff for technical assistance during the experiments. We wish to thank Dr. Ilmo Aronen for giving the initial stimulus to start this study. Thanks are due to DVM Juha Hurmalainen for his cooperation with the ultrasonic scanning programme. We thank biometrician Mr. Lauri Jauhiainen for his statistical expertise. The evaluation of the manuscript by Prof. Pekka Huhtanen and Dr. Seija Jaakkola is gratefully acknowledged. References Absher, C.W., Hobbs, C.S., 1968. Pre-calving level of energy in first calf heifers. J. Anim. Sci. 27, 1130. Andresen, Ø., Onstad, O., 1979. Brunstkontroll og drektighetskontroll hos ku ved hjelp av progesteronbestemmelse i melk. Nor. vet. tidsskr. 91, 411 – 421. Aronen, I., 1991. Influence of frequency and accuracy of supplement feeding on rumen fermentation, feed intake, diet digestion and performance of growing cattle. 1. Studies with growing bulls fed grass silage ad libitum. Anim. Feed Sci. Technol. 34, 49 – 65. Aronen, I., 1992. Influence of frequency and accuracy of supplement feeding on rumen fermentation, feed intake, diet digestion and performance of growing cattle. 2. Studies with growing bulls on restricted feeding. Anim. Feed Sci. Technol. 36, 153 – 166. Claus, R., Rattenberger, E., 1979. Improved method for progesterone determination in milk-fat. Br. Vet. J. 135, 464 – 469. Friedel, K., 1990. Die Scha¨tzung des energetischen Futterwertes von Grobfutter mit Hilfe einer Cellulasemethode. [The estimation of the energetic feeding value of roughages by means of a cellulase method]. Wiss. Ztg. Univ. Rostock N-Reihe 39, 78 – 86. Gaskins, C.T., Anderson, D.C., 1980. Comparison of lactation curves in Angus – Hereford, Jersey – Angus and Simmental – Angus cows. J. Anim. Sci. 50, 828 – 832.

Gill, J.L., 1989. Statistical aspects of design and analysis of experiments with animals in pens. J. Anim. Breed. Genet. 106, 321 – 334. Haacker, K., Block, H.J., Weissbach, F., 1983. Zur kolorimetrischen Milchsa¨ urebestimmung in Silagen mit p-Hydroxydiphenyl [On the colorimetric determination of lactic acid in silages with p-hydroxydiphenyl]. Arch. Tiererna¨hr. 33, 505 – 512. Huida, L., 1973. Quantitative determination of volatile fatty acids from rumen sample and silage by gas – liquid chromatography. J. Sci. Agric. Soc. Finl. 45, 483 – 488. Huida, L., Va¨a¨ta¨inen, H., Lampila, M., 1986. Comparison of dry matter contents in grass silages as determined by oven drying and gas chromatographic water analysis. Ann. Agric. Fenn. 25, 215 – 230. Inskeep, E.K., Lishman, A.W., 1979. Factors affecting postpartum anestrus in beef cattle. Animal Reproduction. Invited Papers Presented at a Symposium held May 14 – 17, 1978, at the Beltsville Agricultural Research Center (Barc), Beltsville, MDBeltsville Symposia in Agricultural Research, vol. 3, pp. 277 – 289. Ka¨hn, W., 1989. Sonographic fetometry in the bovine. Theriogenology 31, 1105 – 1121. Lowman, B.G., Scott, N.A., Somerville, S.H., 1976. In: Condition Scoring of Cattle. The East of Scotland College of Agriculture. Animal Production, Advisory and Development Department, p. 31, Bulletin no. 6. MAFF. Ministry of Agriculture, Fisheries and Food, 1975. In: Energy Allowances and Feeding Systems for Ruminants. Her Majesty’s Stationery Office, London, p. 79, Technical bulletin 33. MAFF. Ministry of Agriculture, Fisheries and Food, 1984. In: Energy Allowances and Feeding Systems for Ruminants. Her Majesty’s Stationery Office, London, p. 85, ADAS reference book 433. Manninen, M., Huhta, H., 2001. Influence of pre partum and post partum plane of nutrition on the performance of crossbred suckler cows and their progeny. Agric. Food Sci. Finl. 10, 3 – 18. Manninen, M., Aronen, I., Huhta, H., 2000. Effect of feeding level and diet type on the performance of crossbred suckler cows and their calves. Agric. Food Sci. Finl. 9, 3 – 16. Manninen, M., Aronen, I., Puntila, M.-L., Heikkila¨, R., Jaakkola, S., 1998. Effect of type of forage offered and breed on performance of crossbred suckler heifers and their calves. Agric. Food Sci. Finl. 7, 367 – 380. Marshall, D.A., Parker, W.R., Dinkel, C.A., 1976. Factors affecting efficiency to weaning in Angus, Charolais and reciprocal cross cows. J. Anim. Sci. 43, 1176 – 1187. McCullough, H., 1967. The determination of ammonia in whole blood by direct colorimetric method. Clin. Chim. Acta 17, 297 – 304. Morris, S.T., Pleasants, A.B., Barton, R.A., 1978. Post-partum oestrous interval of single-suckled Angus beef cows. NZ J. Agric. Res. 21, 577 – 582. NRC, 1984. In: 6th Edition. Nutrient Requirements of Beef Cattle National Academy Press, Washington, DC, p. 90. Petit, M., Agabriel, J., 1989. Beef cows. In: Jarrige, R. (Ed.), Ruminant Nutrition. Recommended Allowances and Feed Tables. INRA, Paris, pp. 93 – 108.

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Tuori, M., Kaustell, K., Valaja, J., Aimonen, E., Saarisalo, E., Huhtanen, P., 1996. In: 2nd Edition. Rehutaulukot ja ruokintasuositukset (Feed Tables and Feeding Recommendations) Yliopistopaino, Helsinki, p. 99. Tuori, M., Kaustell, K., Valaja, J., Aimonen, E., Saarisalo, E., Huhtanen, P., 2000. In: 3rd Edition. Rehutaulukot ja ruokintasuositukset (Feed Tables and Feeding Recommendations) Yliopistopaino, Helsinki, p. 88. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583 – 3597. Wiktorsson, H., Knutsson, P.-G., 1977. Effects on milk production of controlled variation in concentrate feeding. Swed. J. Agric. Res. 7, 159 – 162. Wiltbank, J.N., Rowden, W.W., Ingalls, J.E., Gregory, K.E., Koch, R.M., 1962. Effect of energy level on reproductive phenomena of mature Hereford cows. J. Anim. Sci. 21, 219 – 225.