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1.
Our objectives were to investigate the effects of genotype, yield and composition of milk, and changes in BW and body condition on the initiation of cyclic ovarian activity in nonsuckled beef and dairy cows milked twice daily. Nulliparous heifers were selected from three breeds, 12 Angus, 13 Simmentals, and 26 Holsteins, based on their EBV for milk yield. Cows were machine-milked twice daily, and daily milk yield was recorded; composite samples of milk were collected twice weekly for analyses of milk components. Blood was collected from all cows thrice weekly for 75 d postpartum, and concentrations of progesterone in serum measured by RIA were used to estimate day of first postpartum ovulation. Holstein cows produced more (P less than .05) milk (unadjusted or 3.5% fat-corrected) than Angus or Simmental cows during the first 30 d of lactation. Holstein cows had higher (P less than .01) peak yield of milk than Simmental and Angus cows. Days to peak milk yield were similar for Simmental and Holstein cows, and both were more (P less than .05) than those for Angus cows. Percentages of fat, protein, and total solids in milk were highest (P less than .05) for Simmental cows, whereas milk of Holstein cows had the highest (P less than .05) percentage of lactose and lowest (P less than .05) concentration of somatic cells. Average BW at ovulation differed (P less than .05) among breeds. Estimated daily changes in BW from calving to first ovulation were different (P less than .05) for Holstein and Simmental cows but were similar to those of Angus cows.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
Over six calf crops, 524 exposures of Angus cows to three sire breeds resulted in 432 weaned calves for an 82.4% calf crop. Least-squares means for weaning rate by sire breed were 81.8, 80.5 and 83.9% for Angus, Charolais and Holsteins, respectively. Sire breed effect was not significant for calving rate, calf mortality or overall weaning rate, but was significant for all growth traits from birth to 18 mo. Angus-sired calves were smallest at birth, grew at a slower rate and were lightest in weight at all ages. Charolais-sired calves were heaviest at all weigh periods and Holstein-sired calves were intermediate. Holstein-sired calves scored significantly lower for both grade and condition than did Angus- and Charolais-sired calves. Charolais-sired calves had the highest grade. Calving rate tended to be influenced by the effect of cow (P less than .10) and sire breed X year (P less than .001). Calving rate was highest for 3-yr-old and for 6- to 10-yr-old cows and was also 1.5 percentage units higher for crossbred matings. Cow productivity (kg of calf weaned/cow exposed) is a combined measure of fertility, calf survival and weaning weight. Although sire breed did not significantly affect cow productivity (P less than .20), actual values favored cows producing crossbred calves by 14 and 9 kg for Charolais and Holstein crosses, respectively. Likewise, weight differences at 18 mo favored these crosses by 50 and 32 kg for heifers and 72 and 62 kg for steers. Among the two crossbred types, Charolais X Angus heifers were 28 kg heavier (P less than .05) than Holstein X Angus heifers at 18 mo but the 10 kg difference in steers was not significant. The fact that the large sire breeds produced calves with heavier weaning weights without demonstrating significant increases in overall productivity points out the importance of high weaning rates.  相似文献   

3.
Angus, Boran and Red Poll sires were mated to Ankole, Boran and small East African Zebu (Zebu) females to produce the cows characterized in this study, which produced calves by Friesian, Brown Swiss, Simmental, Boran and Red Poll sires. Individual traits included cow parturition weight, cow weight at weaning, cow mean weight and cow weight change from parturition to weaning; maternal traits included calf crop born percentage, preweaning viability percentage, overall viability percentage, birth weight, weaning weight, weight at 12, 18 and 24 mo and calf weight weaned per cow exposed to breeding (productivity index). Cows by Angus and Red Poll sires significantly exceeded cows by Boran sires (all cows in this comparison had Ankole and Zebu dams) in weaning weight of progeny and in cow weight at parturition and at weaning. Cows by Red Poll sires significantly exceeded cows by Boran sires in birth weight of progeny. Progeny of cows by Boran sires significantly exceeded progeny of cows by Angus and Red Poll sires in 24-mo weight. Cows by Angus and Red Poll sires did not differ (P greater than .05) in any of the traits analyzed. Cows with Ankole and Boran dams significantly exceeded cows with Zebu dams (all cows in this comparison had Angus and Red Poll sires) in progeny weight at birth, 18 mo and 24 mo and in cow weight at parturition and at weaning. Cows with Boran dams significantly exceeded cows with Zebu dams in weaning and 12-mo weight of progeny and significantly exceeded cows with Ankole dams in weaning weight of progeny. The significantly heavier weaning weight and significantly lighter 24-mo weight of the 3/4 Bos taurus progeny of cows with Angus and Red Poll sires relative to the 1/2 Bos taurus progeny of cows with Boran sires suggest that cattle that are 1/2 Bos taurus breed composition have greater general adaptation than cattle with 3/4 Bos taurus breed composition in the postweaning nutritive and climatic environment under which this experiment was conducted. Significantly heavier weights of Angus and Red Poll crossbred cows relative to Boran crossbred cows (all breeds crossed on Ankole and Zebu cows) indicate that the two Bos taurus breeds exceed the Boran (Bos indicus) breed in additive direct genetic effects for size when they have general adaptation to the environment.  相似文献   

4.
Production data were collected on mature cows produced by mating Angus and Hereford (pooled AH), Brahman (Bh) and Boran (Br), and Tuli, a tropically adapted Bos taurus, sires by AI or natural service to Angus and Hereford cows. These cows were mated to Charolais bulls for the purpose of this study. Within each sire breed of cow, cows were assigned randomly to one of three feeding rates, 49 or 76 g of DMI/ BW0.75 or ad libitum (10 to 12 cows/feeding rate group), with weekly individual animal feed consumption recorded. Lactation yields were recorded via the weigh-suckle-weigh protocol at approximately 14, 28, 56, 84, 112, 140, 168, and 196 d postpartum for each cow/calf pair. Means for milk yield at peak lactation, total milk yields, calf birth weight, age-adjusted weaning weights, preweaning daily gain, and feed efficiency were estimated. Peak yield (kg/d) for Bh (10.3 +/- 0.36) was greater (P < 0.05) than for Tuli (9.0 +/- 0.31). Total yield (kg, 212 d) for Bh (1802 +/- 68) was greater (P < 0.05) than for Tuli (1532 +/- 59). Birth weight of AH (44 +/- 0.9) was heavier than for Bh and Br (P < 0.05). Preweaning daily calf gain (g/d) and adjusted weaning weight (kg) of Bh (813 +/- 28, 212 +/- 6.1) and Br (766 +/- 24, 202 +/- 5.1) differed (P < 0.05) from AH (589 +/- 24, 169 +/- 5.2) and Tuli (634 +/- 24, 176 +/- 5.3). Efficiency estimates (grams of adjusted weaning weight/kilograms DMI of the cow) for Bh (88 +/- 2.5) and Br (85 +/- 2.1) exceeded (P < 0.05) those for Tuli (74 +/- 2.1) and AH (73 +/- 2.1). Bos indicus breed crosses exhibited greater peak and total yield, lower birth weight, greater daily gain and adjusted weaning weight, and higher feed efficiency than did Bos taurus breed crosses (P < 0.05). Total yield, daily gain, adjusted weaning weight, and feed efficiency were higher (P < 0.05) for cows sired by bulls from tropically adapted breeds, and the peak yield was less (P < 0.10). Tuli exhibited lower total yield and birth weight than did Angus/Hereford (P < 0.05). The efficiency of crossbred Tuli cows did not differ from Angus/Hereford F1 females, but neither equaled the efficiency of crossbred cows produced using Bos indicus breeds.  相似文献   

5.
Net returns were defined as a function of the monetary returns (revenue) generated by the outputs less the monetary costs generated by the variable inputs. Outputs included total weaning weights of steers and heifers, weight of cull cows and weight of open heifers. Inputs included both feed and nonfeed costs. The net returns equation was incorporated as the objective function in a linear programming model. By maximizing the objective function, the breeding system that generated the highest net returns could be identified considering certain resource constraints. Breeding systems included purebred Herefords; small rotational dual purpose (SR), utilizing the breeds Angus, Pinzgauer, Gelbvieh and Tarentaise; large rotational (LR), a three-way rotational cross with the breeds Charolais, Simmental and Maine-Anjou; and Angus-sired terminal (AL) utilizing Angus as the sire breed and LR heifers as the maternal breed. Large rotational generally produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size), calving rates, management systems, environment, beef to feed price ratios and purchased or farm-produced (inexpensive) feed utilized. Only under the conditions of a herd size constraint and farm-produced feed did AL exceed SR in net returns. Hereford had larger net returns than LR only when the two breeding systems were evaluated in an environment assumed to be reproductively stressful to LR. Ranking of breeding systems were dependent on specific conditions and indicated that one must consider each resource constraint and environment in which cattle are expected to produce before making breeding system recommendations.  相似文献   

6.
Three-year-old Angus x Gelbvieh beef cows nutritionally managed to achieve a BCS of 4 +/- 0.07 (479.3 +/- 36.3 kg of BW) or 6 +/- 0.07 (579.6 +/- 53.1 kg of BW) at parturition were used in a 2-yr experiment (n = 36/yr) to determine the effects of prepartum energy balance and postpartum lipid supplementation on cow and calf performance. Beginning 3 d postpartum, cows within each BCS were assigned randomly to be fed hay and a low-fat control supplement or supplements with either high-linoleate cracked safflower seeds or high-oleate cracked safflower seeds until d 60 of lactation. Diets were formulated to be isonitrogenous and isocaloric, and safflower seed supplements were provided to achieve 5% of DMI as fat. Ultrasonic 12th rib fat and LM area were lower (P < 0.001) for cows in BCS 4 compared with BCS 6 cows throughout the study. Cows in BCS 4 at parturition maintained (P = 0.02) condition over the course of the study, whereas cows in BCS 6 lost condition. No differences (P = 0.44 to 0.71) were detected for milk yield, milk energy, milk fat percentage, or milk lactose percentage because of BCS; however, milk protein percentage was less (P = 0.03) for BCS 4 cows. First-service conception rates did not differ (P = 0.22) because of BCS at parturition, but overall pregnancy rate was greater (P = 0.02) in BCS 6 cows. No differences (P = 0.48 to 0.83) were detected in calf birth weight or ADG because of BCS at parturition. Dietary lipid supplementation did not influence (P = 0.23 to 0.96) cow BW change, BCS change, 12th rib fat, LM area, milk yield, milk energy, milk fat percentage, milk lactose percentage, first service conception, overall pregnancy rates, or calf performance. Although cows in BCS of 4 at parturition seemed capable of maintaining BCS during lactation, the overall decrease in pregnancy rate indicates cows should be managed to achieve a BCS >4 before parturition to improve reproductive success.  相似文献   

7.
Mitochondrial respiratory metabolism and performance of cattle   总被引：1，自引：0，他引：1  
Two groups of cows were sampled to study variation of mitochondrial metabolism. The first group included 10 lactating and five gestating Holstein cows, representing available phenotypic extremes for milk yield. The second group included 13 Angus, 13 Brangus and 13 Hereford cows, representing available extremes within breeds for growth breeding value ratios. Consistently poor mitochondrial samples were obtained from gestating cows; these were excluded from analyses. Linear correlations of Holstein mitochondrial respiratory activities with sire-predicted difference for milk and milk fat ranged from -.35 to .15. Correlations of dam and cow indices and cow yields for milk with acceptor-stimulated mitochondrial respiration, oxidative phosphorylation efficiency (adenosine diphosphate:oxygen ratio [ADP:O ratio]) and adenosine triphosphate (ATP) synthesis rate were .25 to .48, consistently higher than for milk fat, -.06 to .17. No differences among beef breeds in mitochondrial respiration rates, coupling of respiration to phosphorylation, ADP:O ratio or ATP synthesis rate were detected by repeated measures analyses of variance. No patterns were evident among correlations of the mitochondrial characteristics and growth and milk traits in beef cattle. These initial findings indicate that variability in the mitochondrial respiratory activities measured has less relation to weaning and yearling growth traits of beef cattle than to milk yield of Holstein cattle.  相似文献   

8.
The objectives of this study were to quantify the relationships between traits observed before the first breeding season and fertility of 946 Angus and 351 Simmental heifers and to use those traits to develop prediction equations for heifer fertility. Logistic regression methodology was used. Traits investigated were Julian birth date, age of the heifer's dam, birth weight, actual weaning and yearling weights, weaning and yearling weight ratios, 205-d weight, 365-d weight, and birth-weaning, weaning-yearling, and birth-yearling ADG and relative growth rate (RGR). In both breeds heifers that were younger at the start of the breeding season were less likely to conceive, but this effect was more important for Angus (logistic regression coefficient, b = -.032; P less than .01) than for Simmentals (b = -.015; P = .06). Weaning weight ratio was positively associated with heifer fertility (b = .025; P = .01 and b = .028, P = .04, respectively, for Angus and Simmental), whereas actual weaning weight was related curvilinearly to fertility of Angus heifers. The likelihood of conception was highest for Angus heifers weighing greater than or equal to 240 kg at weaning. The only postweaning trait associated with heifer fertility was weaning-yearling RGR. The likelihood of conception was highest for Angus heifers growing between .15 and .30% per day (P = .01), whereas fertility increased continuously (P = .04) for Simmental heifers as weaning-yearling RGR decreased. The maximum variations in fertility explained by models including all possible explanatory variables were 11.5 and 9.2% for Angus and Simmental, respectively. Results suggested that growth-related traits were relatively more important as a predictor of fertility for Simmental heifers and that age at the start of the breeding season was more important for Angus heifers. The combination of Julian birth date and weaning-yearling RGR produced the best models to predict heifer fertility for both breeds.  相似文献   

9.
Observations of 3,029 matings over 17 yr on an Ozark upland range were used to estimate heritability of pregnancy rate in Angus, Hereford and Polled Hereford cows. Pregnancy rate, the percentage of cows exposed that produced a live calf in the spring, was transformed using the empirical logit transformation and then analyzed for each breed separately by weighted least squares using a mixed model procedure. A numerator relationship matrix for sires of cows was incorporated into the sire model to account for relationships among sires. Variation among years significantly affected pregnancy rate in all three breeds. Age of dam significantly affected pregnancy rate in the Angus and Hereford groups. Paternal half-sib estimates of heritability from the observed binary data (h2b) for pregnancy rate were calculated on first-calf heifers and mature cows for each breed. Respective h2b estimates for heifers and mature cows were .17 and .09 in the Angus group, .04 and .01 in the Hereford group and .05 and .05 in the Polled Hereford group. The heritability estimates when binary records were transformed to the probit scale (h2) were .04 +/- .003 and .02 +/- .001 for Angus, .01 +/- .002 and 0 for Hereford and .01 +/- .001 and .02 +/- .001 for Polled Hereford for heifers and mature cows, respectively. Heritability estimates in this study are in agreement with the literature, indicating little opportunity for improvement in pregnancy rate by selection within a breed.  相似文献   

10.
丙酸镁对泌乳早期奶牛体况、泌乳性能和代谢参数的影响   总被引：1，自引：0，他引：1  
选用36头经产奶牛,根据泌乳期、上一泌乳期305 d产奶量和预产期,采用随机区组设计分为4组,对照组饲喂基础日粮,处理1,2和3组分别在基础日粮基础上添加丙酸镁50,100和150 g/d,研究丙酸镁对泌乳早期奶牛采食量、泌乳性能、血液代谢参数和尿酮浓度的影响。结果表明,添加丙酸镁对奶牛的采食量、乳脂率、乳蛋白率、乳糖率和乳干物质率无显著影响,添加丙酸镁100和150 g/d对产乳量、饲料转化效率、体况及代谢参数有改善,该二处理组产奶量、饲料转化效率、体况评分、能量平衡、血浆葡萄糖和胰岛素浓度均显著高于对照组(P<0.05),而血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05),尿酮浓度(除100 g/d组产后7 d测定值与50 g/d组无显著差异外)显著低于对照组和50 g/d组(P<0.05)。根据试验结果,丙酸镁适宜添加量为100 g/d。  相似文献   

11.
Energy metabolism in lactating beef heifers   总被引：1，自引：0，他引：1  
To obtain measurements of energy balance in lactating beef cows, respiration calorimetry and digestion trials were conducted using seven lactating (613 kg BW) and three nonlactating (598 kg BW) Hereford x Angus heifers fed a pelleted 75% alfalfa:25% concentrate diet. Five measurements of energy balance were obtained at 6- to 7-wk intervals beginning 6 to 10 wk postpartum in lactating heifers and at 6-wk intervals in nonlactating heifers. Milk yield was measured using a combination of weigh-suckle-weigh and machine milking to adapt heifers to milking by machine without the use of oxytocin. Heifers were milked only by machine during measurements of energy balance. Weekly milk yield averages ranged from 8.2 kg/d at wk 5 postpartum to 3.2 kg/d at wk 32 postpartum. When scaled to BW(.75), the regression of NE1 on ME intake and the regression of ME intake on NE1 were remarkably similar to previously published regressions for measurements obtained from lactating Holstein-Friesian cows. The average daily maintenance energy requirement from these regressions was 503 kJ ME/kg BW(.75), a value similar to the average value reported previously for lactating Holstein-Friesian cows (488 kJ/kg (BW.75)). This is in contrast to numerous published comparisons of the maintenance requirements of cattle breed types in the nonlactating state and current NRC standards for estimating maintenance energy requirements of beef and dairy cattle. The results of the present study suggest that when expressed on the basis of BW(.75) the efficiency of utilization of incremental ME above maintenance for milk and tissue energy (i.e., NE1) is similar among lactating Hereford x Angus heifers and lactating Holstein-Friesian cows. The breeds differ in terms of their propensity for milk yield and the resulting partition of ME between milk synthesis and tissue energy retention.  相似文献   

12.
The objective of this project was to determine the genetic control of conception rate, or pregnancy percentage in Angus beef heifers. Producers from 6 herds in 5 states provided 3,144 heifer records that included breeding dates, breeding contemporary groups, service sires, and pregnancy check information. Two hundred fourteen sires of the heifers were represented; with 104 sires having less than 5 progeny, and 14 sires having greater than 50 progeny. These data were combined with performance and pedigree information, including actual and adjusted birth weights, weaning weights, and yearling weights, from the American Angus Association database. Heifer pregnancy rate varied from 75 to 95% between herds, and from 65 to 100% between sires, with an overall pregnancy rate of 93%, measured as the percentage of heifers pregnant at pregnancy check after the breeding season. Pregnancy was analyzed as a threshold trait with an underlying continuous distribution. A generalized linear animal model, using a relationship matrix, was fitted. This model included the fixed effects of contemporary group, age of dam, and first AI service sire, and the covariates of heifer age at the beginning of breeding, adjusted birth weight, adjusted weaning weight, and adjusted yearling weight. The relationship matrix included 4 generations of pedigree. The heritability of pregnancy and first-service conception rates on the underlying scale was 0.13 +/- 0.07 and 0.03 +/- 0.03, respectively. Estimated breeding values for pregnancy rate on the observed scale ranged from -0.02 to 0.05 for sires of heifers. Including growth traits with pregnancy rate as 2-trait analyses did not change the heritability of pregnancy rate. As expected for a reproductive trait, the heritability of pregnancy rate was low. Because of its low heritability, genetic improvement in fertility by selection on heifer pregnancy rate would be expected to be slow.  相似文献   

13.
Angus bulls (n = 16) selected for either high- or low-milk EPD but similar growth EPD were mated within location at random to Angus cows. Daughters were bred to calve at 2 yr of age and annually until 6 yr of age. Milk yield was measured four times during lactation with a portable milking machine to estimate 12-h milk yield. Milk was collected for analysis of the percentage of fat and protein. A mixed model procedure was used to analyze the weaning weight, milk yield, and milk component data. The model for weaning weight included location, genetic line of sire, gender of calf, and age of dam. Calf age at weaning was used as a covariate. The model for the milk yield and components included location, genetic line of sire, gender of calf, period, and age of dam. Random effects for all models included sire of dam nested within line, sire of calf, and year. Genetic line was a significant source of variation for milk yield (P < 0.01) and weaning weight (P < 0.01) but not for percentage of fat or protein. Location was significant for milk yield (P < 0.01), fat (P < 0.01), protein (P < 0.01), and weaning weight (P < 0.01). The interaction of line with location was not significant except for percentage of protein (P < 0.01). Age of dam was significant for milk yield (P < 0.01), weaning weight (P < 0.01), and percentage of protein (P < 0.01), but not for percentage of fat (P = 0.29). Line difference for mean weaning weight was 18.1 kg, which is similar to the difference between lines for milk EPD (19 kg). Weaning weights from high-milk EPD line daughters were heavier (P < 0.01) than low-milk EPD line daughters at each age of dam evaluated. Cows nursed by males had higher milk yields (4.33 kg/12 h) than cows nursed by heifers (4.0 kg/12 h). The difference in yields for gender was significant for 2-, 3-, and 5-yr-old cows, but not for 4- (P < 0.052) and 6-yr old (P < 0.15) cows. Correlation coefficients between weaning weight and weaning EPD, milk EPD, and total maternal EPD were greater than zero (P < 0.01) (0.76, 0.65, and 0.89, respectively). Daughters of sires with high-milk EPD produced more milk at each age and weaned heavier calves than daughters of sires with low-milk EPD. These results confirm the value of milk EPD for improvement of weaning weights in beef cattle and also validate age of dam effects on milk yield and the associated effects on weaning weights.  相似文献   

14.
甜菜碱对奶牛采食量、泌乳性能和血液指标的影响   总被引：3，自引：0，他引：3  
选用20头体重(597±11.8)kg、泌乳天数(88±4.5)d、日产奶(26.3±0.5)kg的经产奶牛,随机分为4组,采用4×4拉丁方设计,研究甜菜碱(0、50、100和150g/d)对泌乳早期奶牛采食量、泌乳性能和血液指标的影响。结果表明:日粮添加甜菜碱对奶牛的采食量、乳蛋白率、乳糖率和血糖浓度无显著影响,100g/d组和150g/d组鲜奶产量显著高于对照组和50g/d组(P<0.05);100g/d组和150g/d组4%乳脂校正乳、能量校正乳和乳脂产量显著高于对照组(P<0.05);100g/d组乳脂率显著高于对照组(P<0.05);100g/d组和150g/d组血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05)。根据以上结果推断,甜菜碱的适宜添加水平为100g/d。  相似文献   

15.
Feed intake, weaning weight and direct and maternal contributions to weaning weight were estimated for four breeding systems using data collected between 1979 and 1986 from 773 cow-calf pairs at the Elora Beef Research Centre. Breeding systems included purebred Hereford (HE), small rotational dual purpose (SR) (a four-way rotational crossing system utilizing Tarentaise, Angus, Gelbvieh and Pinzgauer breeds), large rotational beef (LR) (composed of Maine-Anjou, Simmental and Charolais) and Angus-sired large rotational beef (AL) utilizing Angus as the sire breed and LR as the maternal breed. Large rotational dams had the highest feed intakes for both dry (8.9 kg DM/d) and lactation (11.5 kg DM/d) periods. Conversely, HE calves consumed the greatest amounts of creep feed (309 kg DM), followed by AL, SR and LR. The large rotational system had the highest weaning weights (265 kg) and direct (12.3 kg greater than average of observations) and maternal (9.6 kg greater than average of observations) contributions to weaning weight, followed by AL, SR and HE for all three traits. An equation was derived for net returns that included parameters for feed intake and direct and maternal weaning weight. A linear programming model was designed to incorporate this equation as the objective function and determine the breeding system(s) that maximized net returns under various production conditions. In general, LR produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size) included in the model.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
Our objective was to evaluate differences in lactation traits and calf weights produced by F1 cows under varying daily metabolizable energy availability. Measures of milk yields and calf weight traits were recorded on mature F1 cows. The cows were produced from matings of Angus or Hereford dams with sires representing Angus/Hereford, Shorthorn, Galloway, Longhorn, Nellore, and Salers breeds. The cows' daily DM intakes of a diet composed of a corn silage or alfalfa silage plus corn silage were recorded from approximately 2 wk postpartum until the calves were weaned at an average age of 170 d. Milk yield measurements were recorded when the calves were approximately 14, 28, 56, 84, 112, 140, and 168 d of age. Sources of variation considered for the traits of interest included sire breed of the cow (SBC) and the covariates weaning age of the calf and daily metabolizable energy intake (DMEI) of the cow for lactation and calf weights. The linear and quadratic effects were evaluated for DMEI. The SBC x DMEI (linear) interaction was significant for total milk yield. Sire breed of cow differences (P < .05) were observed for milk yield at time of peak yield, persistency, preweaning ADG, and weaning weight. Salers- and Shorthorn-sired cows had greater (P < .05) peak yield than Galloway, Longhorn, or Nellore cross-bred cows but were not significantly different from the Hereford/Angus. Increasing DMEI linearly increased peak yield and total yield (P < .05). Preweaning ADG of calves from Nellore-sired cows was greater (P < .05) than all SBC. Preweaning ADG of calves from Galloway-sired cows was less than all SBC (P < .05). The linear effect of DMEI was heterogeneous across SBC for total yield. The pooled quadratic effect of DMEI was significant for all traits except birth weight. The DMEI for expression of maximum weaning weight was estimated to be 29 Mcal. Feed efficiency ratios for the test period were 28, 27, 30, 25, 28, 32, and 30 g calf weight:Mcal DMEI for reference and 1980s Angus/Hereford-, Shorthorn-, Galloway-, Longhorn-, Nellore-, and Salers-sired cows, respectively, at the DMEI level of 29 Mcal.  相似文献   

17.
The effect of restricted suckling on milk yield and composition, udder health, and postpartum anoestrus in dairy cows in pasture-based systems, was studied in 32 Holstein multiparous cows and their calves. At calving, each cow–calf pair was randomly assigned to one of two treatments: restricted suckling (RS) of the cows by her own or another calf, twice daily for 30 min or artificial rearing (AR) of the calves with milk obtained from the bulk tank, offered twice a day in buckets. Treatments were applied until week 8 after calving. The diet of the cows consisted of direct grazing in improved pastures, corn silage and a commercial concentrate which was offered at milking. Milk production and composition, udder health, body condition score of the cows, body weight and milk intake of the calves were measured weekly, and the first postpartum ovulation was determined three times a week by ovarian ultrasonography. Cows with RS management had a lower machine-milked milk yield (17.9 vs. 24.8 kg/d), a lower fat percentage (3.21 vs. 4.11%) and 4% fat-corrected milk yield (16.2 vs. 25.7 kg/d), and also a lower average milk flow (1.35 vs. 1.76 kg/min) than cows in the AR treatment. There was no effect of treatment on milk protein percentage or udder health as measured by milk electrical conductivity. The interval from calving to first postpartum ovulation was shorter in the AR cows than in the RS cows (18.5 vs. 21.8 days). The RS calves consumed more milk (7.2 vs. 5.4 kg/d), gained more body weight (0.813 vs. 0.656 kg/d), and had a higher body weight at weaning (84.3 vs. 73.3 kg) than AR calves. Restricted suckling of grazing dairy cows had a negative effect on machine-milked milk yield, fat percentage and 4% fat-corrected milk yield, but had no effect on udder health or on improved weight gain and body weight at weaning of the calves.  相似文献   

18.
Reproductive performance and body weights were studied in 81, 79 and 88 spring-calving beef cows from three groups, reasonably similar in growth rate and mature size but different in level of milk production (low [L] = Hereford x Angus, medium [M] = Red Poll x Angus and high [H] = Milking Shorthorn x Angus). Milk group did not have a significant effect on dates of first postpartum estrus and first and last breeding or in the intervals from calving to first estrus, to first breeding and to last breeding. A significant age-of-cow x milk-group interaction was found for pregnancy rate (PR, P less than .10) and calf-crop percentage (CC, P less than .05). In heifers, PR and CC were lowest for the L (85.6 and 73.6%) and highest for the M group (94.2 and 92.5%); in 2-yr-olds there were no differences, and in older cows, PR was highest for the L (94.8%) and lowest for the H group (91.6%), and there were no differences in CC. As estimated from Brody's growth curves, mature sizes were 530 +/- 5.7, 471 +/- 4.6 and 499 +/- 4.2 kg for the L, M and H groups, respectively. Of weights taken on four occasions during the year, October weight was the highest for all cows. February weight, minus the estimated gravid uterus weight, was the lowest for L and M cows, and May weight was lowest for H cows. Weight fluctuation over an annual cycle was greatest for the L group. Under these experimental conditions, cows in all groups were able to consume sufficient energy and gain or lose body reserves to achieve similar reproductive performance while differing in lactation performance.  相似文献   

19.
We hypothesized that feed resources could be deferred to a later time in the production cycle without a decrease in fertility or weight of calf produced in heifers and young cows. One-hundred and thirty-one MARC III (four breed composite: (1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) heifers were divided into three treatments: M-M-M-M (n = 46), L-H-M-M (n = 41), and L-L-L-H (n = 44). The experiment consisted of four feeding periods. Period 1 was 94 to 186 d of gestation, and heifers were fed a moderate (M) or low (L) level of feed. Period 2 was 187 d of gestation to parturition, and heifers were fed moderate, high (H), or low levels of feed. Period 3 was from parturition through 27 d of lactation, and heifers were fed moderate or low levels of feed. Period 4 was from 28 d to approximately 63 d of lactation, and heifers were fed moderate or high levels of feed. Females remained within treatments through their first parity (heifers) and second parity (cows). Feed intake of L-H-M-M and M-M-M-M treatments did not differ from each other either as heifers (P = 0.23) or as second-parity cows (P > 0.59). The L-L-L-H heifers ate less feed than L-H-M-M and M-M-M-M heifers (P < 0.001), and second-parity L-L-L-H cows ate less feed than second-parity L-H-M-M and M-M-M-M cows (P < 0.002). In the first parity, treatments did not differ in the percentage of calves weaned (P = 0.11), weight of calf weaned (P = 0.50), or percentage of cows diagnosed pregnant (P = 0.29) with a second calf. In the second parity, treatments did not differ in the percentage of calves weaned (P = 0.77), weight of calf weaned (P = 0.63), or percentage of cows expressing a corpus luteum at the start of breeding for their third calf (P = 0.21). Our findings suggest that timing nutrient availability to heifers and primiparous cows can be used to change the time that feed resources are used.  相似文献   

20.
丙酸钙对泌乳早期奶牛泌乳性能和代谢产物的影响   总被引：1，自引：0，他引：1  
选用32头经产奶牛,根据泌乳期、上个泌乳期305 d产奶量和预产期,采用随机区组设计分为4组,对照组饲喂基础日粮,处理1、2、3组分别在基础日粮基础上添加丙酸钙100、200、300 g/d.结果显示,日粮添加丙酸钙对奶牛的采食量、乳脂率、乳蛋白率、乳糖率和乳干物质率无显著影响,200、300 g/d组产奶量和饲料转化效率显著高于对照组(P<0.05).200、300 g/d组血浆葡萄糖和胰岛素浓度显著高于对照组(P<0.05),而血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05);200、300 g/d组尿酮浓度显著低于对照组和100 g/d组(P<0.05).试验结果表明,丙酸钙适宜添加量为200 g/d.  相似文献   

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