饲养管理方式对甘南牦牛繁殖力及杂交后代影响的研究

[目的]为了研究加强种公牛和母牦牛的饲养管理对母牦牛的繁殖效果和杂交后代生长发育的影响.[方法]本试验用大通牦牛和其冻精杂交甘南牦牛,通过对试验组的种公牛、母牦牛和杂交后代进行补饲、延长放牧时间和提前断奶等措施,研究了203头母牦牛的繁殖效果和其杂交后代的生长发育情况.[结果]表明,自然交配试验组发情率、受胎率、繁殖成活率分别比对照组提高9.19%、11.03%、14.10%,流产率和犊牛死亡率降低3.3%、3.87%;人工授精组发情率、受胎率、繁殖成活率分别提高6.74%、5.48%、10.52%,流产率和犊牛死亡率降低4.07%、4.62%.加强母牦牛的饲养管理,所产犊牛的初生重比传统饲养管理条件下母牦牛所产的犊牛初生重公母分别增加2.92 kg和2.07 kg,提高19.80%和14.22%.6月龄体重分别增加12.82 kg和12.23 kg,提高17.45%和16.88%.[结论] 用大通牦牛改良甘南牦牛,采用人工授精和自然交配都有良好的效果,加强种公牛、母牦牛饲养管理是提高牛群繁殖力的有效方法,对后代生长发育影响明显.     

红安格斯牛改良郏县红牛的试验效果

[目的]在保持郏县红牛优良特性的前提下,为了增大郏县红牛体格,提高载肉量和商品率.[方法]遵照以本品种选育为主,适当导入外血(1/2～1/4)杂交改良的选育方向,从2010年开始在河南农业大学大学相关专家的指导下,由平顶山市畜牧局和郏县畜牧局等相关部门相互协作,在平顶山市郏县红牛良种繁育中心引进红安格斯牛对当地饲养的郏县红牛进行杂交改良.[结果]表明安郏F1公牛初生重平均为31.65 kg,母牛为29.03 kg,比郏县红牛初生重分别提高了13.09 kg和10.65 kg;6月龄安郏F1公母牛比同龄郏县红牛的体重分别提高13.52 kg和20.48 kg;12月龄安郏F1公母牛比同龄郏县红牛的体重分别提高46.92 kg和6.90 kg;安郏F1公母牛比同龄郏县红牛的体高、体长、胸围和管围也有较大提高,6月龄安郏F1郏县红牛的体高、体长、胸围和管围分别提高5.91,5.93 cm,12.75,1.37和1.73,5.45,15.67,0.81 cm;12月龄安郏F1公母牛比同龄郏县红牛的体高、体长、胸围和管围分别提高2.93,2.54,13.21,2.07和13.49,3.84,21.14,1.78 cm.[结论]说明利用红安格斯牛改良郏县红牛效果十分显著.     

后期饲养战略对于早期断奶牛生产速度的影响

[目的]为探索适宜当地的犊牛早期断奶时间,促进犊牛早期生长发育和使母牛尽快恢复体况,进入下一个繁殖周期。[方法]选择体格大小一致、健康无疾病、体重接近,父本相同,3月龄西杂犊牛20头作为试验牛,随机分成A组和B组,每组10头(公、母数量相同)。A组经过1个月断奶精料、粗料和多汁饲料的过渡性适应,4月龄断奶,并根据犊牛生长发育逐渐增加精料、多汁饲料,B组按照养殖场饲喂方法饲养,并于6月龄断奶,A组与B组犊牛6月龄断奶后自由采食粗饲料、按体重1%饲喂精饲料,分别在犊牛6,12,18月龄称重。[结果]结果表明:肉牛18月龄时A、B组犊牛的平均体重分别为638 kg,546 kg,A组高于B组92.00 kg(P0.01),表明犊牛早期断奶、在满足营养需要的前提下,后期的生长速度比6月龄断奶高。[结论]犊牛早期断奶技术是一项实用技术,值得在养殖场和规模养殖户中大力推广的应用。     

甘南牦牛杂交改良综合饲养管理模式初探

[目的]为了提高甘南牦牛的个体生产性能,研究放牧条件下甘南牦牛的饲养管理模式,[方法]本课题通过引进大通牦牛,加强种公牛、母牦牛的饲养管理,对杂种犊牛进行全哺乳暖棚育肥试验,[结果]表明,甘南牦牛的发情率、受胎率、繁殖成活率都显著升高,流产率和犊牛死亡率下降明显.所产犊牛的初生重大,生长发育快.经全哺乳培育和暖棚育肥的犊牛,初生重和体尺与对照组相差不大,到6月龄断奶和12月龄体重都显著高于对照组.[结论]通过试验研究总结出一套适宜甘南牦牛杂交改良的综合饲养管理模式,从而指导甘南牦牛的生产.     

断母乳日龄对红安格斯杂交犊牛生长性能的影响

本试验旨在研究肉用犊牛的适宜断母乳日龄,为肉用犊牛的早期培育提供依据。选用60头红安格斯与西门塔尔杂交犊牛,按体重和日龄一致的原则分为5个处理,其中试验组4个,犊牛分别在28、42、56、70 d断母乳并饲喂统一的代乳品至90 d完全断代乳品,对照组犊牛随母牛哺乳至150 d。所有犊牛从29 d起自由采食开食料和粗饲料直至150 d试验结束。每2周测定犊牛的体重、体尺,每日观测腹泻情况。结果表明:70 d前各组间犊牛平均日增重和体尺指标存在差异(P0.05),28 d断奶犊牛日增重数值较低;71~150 d阶段试验组犊牛在增重、体高、体斜长、胸围、腹围等方面显示出优势。全期各试验组犊牛的增重、体尺指标及腹泻率均差异不显著。结论表明,断母乳日龄对犊牛体增重和体尺指标的影响在70 d前较为显著,但在70 d后减弱;早期断奶犊牛具有明显的增重和发育优势;红安格斯与西门塔尔杂交肉犊牛可在42 d时以代乳品替代母乳而不影响其生长性能。     

安格斯牛杂交繁育技术试验

为在我区发展以安格斯牛为主要品种的高端肉牛养殖产业,提高安格斯肉牛繁育生产效率,扩大群体规模,培养地方优质肉牛品种,笔者在2016年4月~2018年9月之间,开展了引进国外优质高产安格斯种公牛冻精,利用人工授精技术、杂交改良技术,对区内部分优质荷斯坦奶牛实施配种的试验工作,经过科学饲养,提升了我区杂交安格斯牛繁育生产效率,解决了安格斯肉牛种源稀缺、生产速度慢的难题。本次试验共筛选荷斯坦奶牛母本100头,其中情期配种成功率达到78%,产犊率达到96%,杂交一代犊牛成活率100%。此次试验共获得杂交一代安格斯牛75头,犊牛平均初生重32 kg,6月龄断奶体重198 kg,平均出栏体重550 kg(20月龄),达到优质肉牛品种标准的较高水平。     

不同日龄断奶对犊牛生长发育的影响观测研究

[目的]为了探索不同的断奶日龄对犊牛生长发育的影响,并确定符合甘肃省中部干旱地区生态条件下、饲养管理水平的犊牛早期断奶最佳时期。促进犊牛早期生长发育和使母牛尽快恢复体况,进入下一个繁殖期。[方法]选择南德温(♂)×秦川牛(♀)杂交新生犊牛40头,按体重和出生时间基本相近的原则随机分为4组,其中:试验Ⅰ、Ⅱ、Ⅲ组分别60日龄、90日龄、120日断奶,对照组按照传统180日龄断奶,在相同的饲养管理条件下,观察期90日龄、120日龄、180日龄、360日龄犊牛生长发育。[结果]表明:90日龄断奶有利于犊牛早期的生长发育,其360日龄体重、体高、体斜长、胸围、平均日增重比60日龄断奶犊牛提高64.6kg(P0.01)、29.5cm(P0.01)、24.5cm(P0.01)、17.8cm(P0.01)、0.42kg(P0.01);比120日龄断奶分别提高62.0kg(P0.01)、19.5cm(P0.01)、14.5cm(P0.01)、18.0cm(P0.01)、0.23kg(P0.05);比传统180日龄断奶分别提高24.5kg(P0.05)、9.5cm(P0.05)、9.0cm(P0.05)、11.5cm(P0.05)、0.28kg(P0.05)。[结论]农户舍饲饲养的南德温与秦川杂交犊牛,最佳适宜断奶时间为90日龄。90日龄断奶与当地群众饲养管理水平相符合,又比传统6月龄断奶提前90d。犊牛早期断奶技术是一项实用技术,值得在养殖户中大力推广的应用。     

红安格斯种后不同输精时间对受胎率影响

红安格斯牛原产英国,是世界著名中型早熟专门化肉牛品种,且产肉率高、肉质优良、风味好、大理石花纹明显,倍受消费者青睐;不仅如此,其母牛还具有母性强、产仔能力强、性成熟早、产奶充足、犊牛成活率高、后躯发育好、遗传性能稳定的特点,为理想的三元杂交品种,深受广大养牛朋友喜欢。由于红安格斯牛品种在我国引入时间较晚,输精时间对受胎率影响相关研究较少,为了撑握最佳的授精时间,提高红安格斯母牛的情期受胎率,笔者对不同发情阶段冷配受胎率的影响进行了研究,现报告如下:1材料与方法1.1试验母牛健康,繁殖机能正常,年龄1.5～7岁。1.2冷配…     

繁殖母牛围产期补饲对犊牛初生重和体尺指标的影响

为研究繁殖母牛妊娠后期额外补饲对犊牛初生重和体尺的影响,本试验选择45头西门塔尔牛×西杂黄牛的杂交成年母牛,根据配种时间、杂交代数将母牛分为2组,其中一组为对照组,按农户的传统方法饲养;一组为试验组,传统饲养方法并额外补饲,产前30 d和产后额外每天补饲500g配合精料,分别测定产后犊牛的初生重和60日龄的体重。结果表明:试验组和对照组的犊牛初生重分别为46.2、1.5 kg,体高为75.6、71.8 cm,犊牛60日龄的体重为111.9、104.6 kg。试验组犊牛初生重、初生体高、60日龄体重、60日龄体高明显高于对照组(P<0.05),但两组间犊牛60 d内的日增重没有差异(P>0.05)。表明在营养状况较差时,妊娠母牛后期和哺乳母牛补饲明显提高犊牛初生重和60日龄的体重。     

母牛带犊繁育技术

母牛带犊繁殖技术是由受体母牛哺乳产后犊牛,犊牛断奶后,通过科学的饲养管理,对受体母牛进行营养调控和繁殖系统护理,尽快恢复母牛的繁殖功能,以继续进行胚胎移植孕育犊牛。采用母牛带犊繁育技术饲养母牛和初生犊牛,对母牛的整个生殖过程及犊牛的生长进行专业的饲养管理及营养调控,显著降低了犊牛饲养成本,降低母牛的难产率和助产率,提高了受体母牛的繁殖效率和犊牛日增重和成活率。     

Comparison of F1 Bos indicus x Hereford cows in central Texas: I. Reproductive, maternal, and size traits.

Cows (n = 116) sired by Angus, Gray Brahman, Gir, Indu-Brazil, Nellore, and Red Brahman bulls and from Hereford dams were evaluated (when bred to the same breed of bull) for reproductive performance and cow weight and height and their calves (n = 1,161) were evaluated for birth and weaning weight in central Texas (temperate winters and subtropical summers). Cows were born from 1982 to 1985 and their calves were born from 1985 to 1999. Crossbred cows sired by Angus had a higher (P < 0.10) occurrence of calving difficulty than Gir, Indu-Brazil, Nellore, and Red Brahman crossbreds. Calves from Gir crossbreds had lighter (P < 0.10) birth weight (34.8 kg) than calves from Angus and Red Brahman crossbreds (39.4 and 37.2 kg). Calves from Angus crossbreds cows had lighter (P < 0.001) weaning weight (227.0 kg) than calves from Bos indicus crossbreds. Cows sired by Angus were lighter (P < 0.10) as mature cows (520.69 kg) than Gray Brahman, Indu-Brazil, and Red Brahman crossbreds (585.6, 571.9, and 577.6 kg, respectively). They also had smaller (P < 0.05) hip height (124.7 cm) than Bos indicus crossbreds. Mature cows sired by Indu-Brazil had greater (P < 0.05) hip height (138.3 cm) than Gir crossbreds (133.8 cm). Differences among sire breeds were noted within cow age categories (2 through 14 yr of age) for pregnancy rate, calf crop born, calf survival rate (as a trait of cow), and calf crop weaned. Angus and Indu-Brazil crossbred cows were lower (P < or = 0.10) than Gir and Nellore crossbreds for pregnancy rate, calf crop born, and(or) calf crop weaned at some, but not all, ages. Indu-Brazil crossbreds had a lower (P < or = 0.10) calf survival rate than most other breed groups at ages 11 to 14 yr. The results of this study indicate that Nellore and Gir crossbreds, but not Indu-Brazil, could perform as well or better than breeds traditionally used in cross-breeding programs of U.S. cow-calf production.     

Characterization of breeds of Bos indicus and Bos taurus cattle for maternal and individual traits

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.     

Growth and pubertal development of F1 bulls from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu sires

The objective of the study was to characterize body growth, testicular development, and puberty from 8 to 14 mo of age in bulls (n = 120) produced by mating sires from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu breeds to MARC III ((1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) cows. Traits evaluated were birth weight, weaning weight (at 215 d), yearling weight, ADG from 8 to 14 mo of age, paired testicular volume growth from 8 to 14 mo of age, age at puberty (determined by production of 50 x 10(6) sperm with 10% motility), age at freezable semen (determined by production of 500 x 10(6) sperm with 50% motility), and, at 15 mo of age, paired testicular weight and daily sperm production per testis pair. There was an effect of sire breed (P = 0.03) for age at puberty; animals with Wagyu and Swedish Red and White inheritance reached puberty at a later date (302 and 302 d of age, respectively) compared with Angus-sired bulls (268 d). Age at puberty for Hereford-, Norwegian Red-, and Friesian-sired bulls was 270, 271, and 278 d, respectively. Differences in BW were observed (P = 0.03) at birth; bulls with Hereford and Friesian were heavier at birth (43 and 41 kg, respectively) compared with those with Norwegian Red, Swedish Red and White, and Wagyu inheritance (39, 38, and 38 kg, respectively). Differences in BW were also observed at 1 yr of age (P = 0.001), where the heaviest animals were those sired by Angus (450 kg), whereas the lightest animals were those sired by Wagyu (403 kg). Bulls with Wagyu inheritance had the lowest (P = 0.04) ADG (1.12 kg/d) compared with bulls with inheritance from Hereford (1.22 kg/d), Angus (1.28 kg/d), Norwegian Red (1.24 kg/d), Swedish Red and White (1.25 kg/d), and Friesian (1.27 kg/d). Differences in scrotal growth rate were not significant (P = 0.99). They ranged from 1.95 in Angus-sired to 1.66 cm3/d in Wagyu-sired bulls. There were no differences (P = 0.80) for age at freezable semen (335 +/- 10 d). At slaughter (15 mo of age), there were no differences (P = 0.62) for paired testicular weight (603 +/- 28 g) and daily sperm production (10.6 x 10(9) +/- 0.9 x 10(9) per testis pair). Growth of bulls with Wagyu inheritance was slower, and bulls with Wagyu or Scandinavian inheritance reach puberty at an older age than bulls with Angus inheritance.     

Birth and weaning traits in crossbred cattle from Hereford, Angus, Norwegian Red, Swedish Red and White, Wagyu, and Friesian sires

The objective of this study was to characterize breeds representing diverse biological types for birth and weaning traits in crossbred cattle (Bos taurus). Gestation length, calving difficulty, percentage of unassisted calving, percentage of perinatal survival, percentage of survival from birth to weaning, birth weight, weaning weight, BW at 205 d, and ADG was measured in 1,370 calves born and 1,285 calves weaned. Calves were obtained by mating Hereford, Angus, and MARC III (1/4 Hereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) mature cows to Hereford or Angus (British breeds), Norwegian Red, Swedish Red and White, Wagyu, and Friesian sires. Calves were born during the spring of 1997 and 1998. Sire breed was significant for gestation length, birth weight, BW at 205 d, and ADG (P < 0.001). Offspring from Swedish Red and White and Friesian had the shortest gestation length (282 d), whereas offspring from Wagyu sires had the longest gestation length (286 d). Progeny from British breeds were the heaviest at birth (40.5 kg) and at 205 d (237 kg), and grew faster (0.97 kg/d) than offspring from other breeds. Offspring from Wagyu sires were the lightest at birth (36.3 kg) and at 205 d (214 kg), and had the slowest growth (0.91 kg/d). Dam breed was significant for gestation length (P < 0.001), birth weight (P = 0.009), BW at 205 d, and ADG (P < 0.001). Offspring from Hereford cows had the longest gestation length (284 d), whereas offspring from Angus cows had the shortest (282 d). Offspring from MARC III cows were the heaviest at birth (39.4 kg) when compared with offspring from Hereford (38.2 kg) and Angus (38.6 kg) cows. Progeny from Angus cows were the heaviest at 205 d (235 kg) and grew faster (0.96 kg/d), whereas offspring from Hereford cows were the lightest at 205 d (219 kg) and were the slowest in growth (0.88 kg/d). Sex was significant for gestation length (P = 0.026), birth weight, BW at 205 d, and ADG (P < 0.001). Male calves had a longer gestation length (284 d) when compared with female calves (283 d). Males were heavier than females at birth and at 205 d, and grew faster. Sire breed effects can be optimized by selection and use of appropriate crossbreeding systems.     

Life-cycle evaluation of Bos taurus and Bos indicus X Bos taurus breed types in a dry, temperate climate: performance of mature dams

Mature dams representing Hereford, Red Poll, F1 Hereford x Red Poll, F1 Red Poll x Hereford, F1 Angus x Hereford, F1 Angus x Charolais, F1 Brahman x Hereford and F1 Brahman x Angus breed types were evaluated. All cows were bred to Limousin sires to produce two-way or three-way-cross progeny. Mature Brahman x Hereford dams produced a higher (P less than .05) percentage of live calves than Herefords, but dam breed differences in percentage of calves weaned relative to the number of cows exposed for mating were not statistically significant. Progeny of Angus x Charolais and Red Poll dams were outstanding in weaning weight, but Hereford and Brahman-cross calves were below average. Planned comparisons showed that Angus x Charolais calves were heavier (P less than .01) at weaning than Hereford (23.0 +/- 3.8 kg) or Angus x Hereford (9.6 +/- 3.2 kg) progeny. Mature Angus x Hereford mothers weaned heavier calves than did Brahman x Herefords (7.4 +/- 3.2 kg, P less than .05) or Brahman x Angus (10.9 +/- 3.0 kg, P less than .01). Analysis of the Hereford-Red Poll diallel showed evidence of maternal heterosis in calf weaning weight (4.0 +/- 2.6 kg, P less than .05), but there was no difference in the percentage of calves weaned by crossbred vs straightbred dams.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of Bos taurus-Bos indicus breed crosses with straightbred Bos indicus breeds of cattle for maternal and individual traits

Data were analyzed to compare crossbred females produced by crossing exotic Angus and Red Poll males to indigenous Ankole, Boran and Small East African Zebu (Zebu) females with straightbred females of the Ankole, Boran and Zebu breeds at the Ruhengere Field Station in the Ankole District of Southwestern Uganda. Progeny of the straightbred and crossbred dams were by Friesian, Brown Swiss and Simmental sires. Crossbred exotic X indigenous dams were favored over straightbred indigenous dams by 13.7% (P less than .01) in calf birth weight and by 14.8% (P less than .01) in calf weaning weight. Cross-bred cows exceeded (P less than .01) straightbred cows by 61.9% (48.5 kg) in calf weight weaned per cow exposed to breeding. Crossbred cows weighed 37, 46 and 42 kg more (P less than .01) than straightbred cows at parturition, weaning and cow mean weight, respectively. Angus X Boran and Red Poll X Boran crossbred dams were compared specifically with straightbred Boran dams. Exotic (Angus, Red Poll) X Boran crossbred dams exceeded straightbred Boran dams by 27.0% (P less than .05) in calf crop born, by 8.3% (P less than .05) in progeny birth weight and by 14.7% (P less than .01) in progeny weaning weight. Weight of calf weaned per cow exposed to breeding favored (P less than .01) the Angus X Boran and Red Poll X Boran crossbred dams over the straightbred Boran dams by 50.5% (50 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolizable energy for maintenance of beef-type Bos taurus and Bos indicus x Bos taurus cows in a dry, temperate climate

Metabolizable energy for maintenance (MEm) was estimated using 123 mature cows of eight diverse breed groups. Cows in each breed group were allotted at random 1) to limit-feeding to approximate maintenance or 2) to ad libitum access to feed. The MEm values were calculated by regression of change in body energy on ME intake. The MEm values for mature Hereford, Red Poll, Hereford x Red Poll, Red Poll x Hereford, Angus x Hereford, Angus x Charolais, Brahman x Hereford, and Brahman x Angus breed types were as follows: 145, 169, 148, 149, 144, 152, 139, and 143 kcal.kg-.75.d-1, respectively. Bos indicus-cross cows ranked lowest for MEm/kg.75. Angus x Hereford cows averaged highest in terms of grams of calf weaned per mature female exposed divided by yearly MEm requirement. Hereford x Red Poll reciprocal crosses on average required 640 kcal less total daily MEm per animal than Hereford and Red Poll straightbreds.     

Genotype x environmental interaction for mature size and rate of maturing for Angus,Brahman, and reciprocal-cross cows grazing bermudagrass or endophyte infected fescue

Mature weight and rate of maturing were estimated in 177 Angus, Brahman, and reciprocal-cross cows grazing bermudagrass or endophyte-infected tall fescue over a 4-yr period to evaluate genotype x environment interactions. Data were collected every 28 d until cows were approximately 18 mo of age and then at prebreeding, postcalving, and weaning of calf. All cows with weight data to at least 42 mo of age were included in the analysis. Mature weight and rate of maturing were estimated using the three-parameter growth curve model described by Brody (1945). Data were pooled over year and analyzed by the general linear model procedure of SAS. Included in the models for mature weight and rate of maturing were the independent variables of genotype, environment, and genotype x environment interaction. There was a genotype x environment interaction (P < 0.01) for mature body weight (BW) but not for rate of maturing. Angus cows grazing fescue pastures had greater (P < 0.01) mean mature BW than Angus x Brahman cows grazing bermudagrass (611 +/- 17 vs 546 +/- 16 kg). Angus x Brahman cows grazing bermudagrass had lower (P < 0.05) mean mature BW than Brahman x Angus cows grazing bermudagrass or endophyte-infected fescue and Brahman cows grazing bermudagrass (546 +/- 16 vs 624 +/- 19, 614 +/- 22 and 598 +/- 20 kg, respectively). Brahman cows grazing endophyte-infected fescue had smaller (P < 0.05) mean mature BW than all genotype x forage combinations except for Angus x Brahman cows grazing bermudagrass. Angus cows had a smaller (P < 0.05) mean rate of maturing than Angus x Brahman and Brahman x Angus cows (0.039 +/- 0.002 vs 0.054 +/- 0.002 and 0.049 +/- 0.002%/mo, respectively), respectively, and Angus x Brahman cows had a larger (P < 0.05) mean rate of maturing than Brahman x Angus and Brahman cows (0.054 +/- 0.002 vs 0.049 +/- 0.002 and 0.041 +/- 0.002 %/mo, respectively). There was a direct breed x forage interaction (P < 0.05) for mature BW. These data suggest that the choice of breed type is important in maintaining a crossbreeding program, in that mature BW and rate of maturing are critical to the matching of animal requirements to available production resources.     

Maternal and reproductive performance of Brahman x Angus, Senepol x Angus, and Tuli x Angus cows in the subtropics

To determine the maternal and reproductive performance of F1 cows in the subtropics, 42 Brahman x Angus, 34 Senepol x Angus, and 50 Tuli x Angus cows were bred to Angus bulls to calve first and subsequently bred to Charolais bulls to calve as 3- to 8-yr-olds. Age at first calving did not differ among crossbred cows. Angus-sired calf birth weights were heavier (P < 0.01) from Senepol x Angus than either Brahman x Angus or Tuli x Angus cows. Weaning weights of Angus-sired calves were heavier (P < 0.01) from Brahman x Angus (213.5 kg) than either Senepol x Angus (194.9 kg) or Tuli x Angus (191.5 kg) cows. As 3- to 8-yr-old cows, calf birth weights were heavier (P < 0.05) from Senepol x Angus compared with Brahman x Angus but not Tuli x Angus cows. Weaning weights of Charolais-sired calves were heaviest (P < 0.05) from Brahman x Angus cows (268.9 kg), lightest from Tuli x Angus cows (233.4 kg), and intermediate from Senepol x Angus cows (245.0 kg). Calf crop born and calf crop weaned were lowest (P < 0.05) for Senepol x Angus cows (76.9 and 70.2%) and did not differ between Brahman x Angus (89.0 and 86.1%) and Tuli x Angus (94.7 and 86.5%) cows. Tuli x Angus cows tended (P < 0.10) to have a lower percentage of unassisted births and lower (P < 0.10) calf survival to weaning than Brahman x Angus cows but not Senepol x Angus cows. As 3- to 8-yr-olds, weaning weight per cow exposed was greatest (P < 0.05) for Brahman x Angus (234.2 kg), least (P < 0.05) for Senepol x Angus (173.0 kg), and intermediate (P < 0.05) for Tuli x Angus (209.1 kg) cows. Also as 3- to 8-yr-olds, efficiency (205-d calf weight per 100 kg of cow exposed) was similar for Brahman x Angus (42.2) and Tuli x Angus cows (40.7), and both were greater (P < 0.01) than for Senepol x Angus cows (33.8). These data indicate that, in the subtropics, maternal and reproductive performance of Tuli x Angus cows, but not Senepol x Angus cows, was comparable to Brahman x Angus cows, except for lower calf survivability and weaning weight.     

安格斯母牛初乳产量与质量测定及其新生犊牛被动免疫效果评价

【目的】 新生犊牛被动免疫转移失败（failure of passive transfer,FPT）会导致犊牛发病率和死亡率显著增高,影响后期生长发育。本试验针对国外引进的安格斯母牛初乳产量和质量进行测定,并对其新生犊牛被动免疫效果进行评估,以期为新生犊牛初乳管理措施制定提供科学依据。【方法】 随机选择健康安格斯初产母牛（24月龄）和经产母牛（36~48月龄）各15头,待母牛产犊后立即进行人工挤奶测定初乳产量、营养成分及免疫球蛋白浓度。选取初产和经产新生犊牛各15头,测定其初生重,分别采集犊牛出生后未食初乳（0 h）和食初乳后（24~36 h）血样,测定其血清总蛋白含量及各生理生化指标。【结果】 初产母牛平均初乳产量极显著低于经产母牛,但其初乳中乳蛋白、非脂乳固体、乳糖、灰分含量,以及密度和电导率均极显著高于经产母牛（P<0.01）。初产母牛和经产母牛初乳中免疫球蛋白浓度分别为28.72%和26.24%,合格率分别为93.33%和91.67%,差异均不显著（P>0.05）;初产和经产新生犊牛被动免疫失败率分别为33.3%和25.0%;初产新生犊牛平均初生重极显著低于经产新生犊牛（P<0.01）;被动免疫成功犊牛平均初生重和球蛋白含量均极显著高于被动免疫失败犊牛（P<0.01）。【结论】 新疆安格斯犊牛FPT的主要原因可能是母牛初乳产量低导致新生犊牛初乳摄入不足,初生重较低的犊牛FPT的风险性较高。本研究为制定切实可行的新生安格斯犊牛初乳补饲计划提供了科学基础。