半舍饲条件下淘汰母牦牛育肥及犊牦牛培育技术研究

旨在研发半舍饲条件下淘汰母牦牛育肥及犊牦牛培育技术。选取带犊母牦牛和公犊牛各66头,分别随机分为试验组和对照组。在犊牛培育期间（2017年12月4日—2018年3月5日）,对试验组母牦牛进行补饲,试验组犊牦牛断乳前（3月5日断乳）随母牦牛哺乳,并进行补饲;对照组母牦牛不进行补饲,按常规放牧方式饲养,对照组犊牦牛进行断乳并补饲。育肥期间（2018年3月5日至出栏）对试验组母牦牛进行补饲,于6月错峰出栏;对照组母牦牛不进行补饲,于集中出栏时间出售（9月或10月）。在犊牦牛培育期间,观察试验组母牦牛的体重变化情况;每月4日测定2组犊牦牛的体重和体尺指标,并进行统计学分析。计算试验组母牦牛错峰出栏收益。结果表明,在犊牦牛培育阶段,由于试验组犊牦牛随母牦牛哺乳,试验组母牦牛体重平均下降1.17 kg/头;2018年1月4日,试验组犊牦牛的体重极显著（P<0.01）高于对照组,体斜长和胸围显著（P<0.05）高于对照组;2018年2月4日和3月4日,试验组犊牦牛的体重、体高、体斜长、胸围均极显著（P<0.01）高于对照组。试验组母牦牛错峰出栏的效益为1 063.05元。研究结果为提高半舍饲条件下淘汰母牦牛养殖效益以及提升犊牛培育质量提供了技术支撑。     

尿素糖蜜多营养舔砖补饲牦牛效果的研究

分别在天祝县和碌曲县选用９０头天祝白牦牛和６０头甘南牦牛进行了冷季放牧牦牛尿素糖蜜多营养舔砖的补饲试验，尿素糖蜜多营养舔砖含尿素１０％，糖蜜１０％，采食量为０．５ｋｇ／（ｄ·头）。经５个月补饲后，天祝白牦牛和甘南牦牛的活重损失分别减少８０．３％和４６．８％，产奶量分别提高２０％和１３．６％，怀孕率分别提高１７．４和２０．０个百分点，投入产出比分别达到１∶３．５０和１∶２．１１。处理组与对照组之间存在极显著差异（Ｐ＜０．０１），证明尿素糖蜜多营养舔砖是实施高寒牧区放牧牦牛冷季补饲的一条新的有效途径     

Postpartum oestrous cycling resumption of yak cows following different calf weaning strategies under range conditions

Early weaning can improve body condition and reproductive performance of cows. The objectives of this study were to examine and compare oestrous cycling resumption, behaviour and blood parameters of yak cows following four different strategies of calf weaning. Twenty‐six yak cows (4–8 years) and their calves (94.3 ± 2.4 days) were studied in which calves were: weaned naturally with free access to their mothers (NW; n = 13); weaned abruptly and separated permanently from their mothers (PW; n = 5); separated temporarily from their mothers for 15 days (TW; n = 5); and fitted with nose plates for 15 days, but allowed free access to their mothers (NP; n = 3). Yak cows with sucking calves (NW) spent more time grazing in the cold season (from d 39 to 84). Based on serum progesterone concentrations, none of nine NW yak cows resumed oestrous cycling during the study, while seven of nine yak cows with weaned calves resumed cycling (3/3 for PW; 2/3 for TW; and 2/3 for NP yaks). We concluded that early weaning improved postpartum reproductive performance of yak cows on the Qinghai‐Tibetan plateau and that abrupt and permanent weaning was an appropriate strategy.     

Effect of strategic feed supplementation on productive and reproductive performance in yak cows

A total of 2230 yak cows (5-13 years of age) in two populations with different milking systems were investigated. One population had a system of milking once a day (MOD), and the other population twice a day (MTD). The average milk yield of MOD cows was 0.7 +/- 0.2 kg/day within a milking period of 109 +/- 9 days. This compared with an average of 1.24 +/- 0.3 kg/day in 127 +/- 6 days in MTD yaks (p < 0.01). The cows showed a calving rate of 71% under the MOD system and 51.4% under the MTD system. Three farms with a total of 104 MTD cows between six and 12 years of age were used to provide three different feeding groups. The groups were fed with, or without oat hay or highland barley straw in amounts of 1-1.5 kg/head/day from December to April. The three farms were designated as Farm I, Farm II, and Farm III. Farm I had 41 cows with body weight of 230 +/- 67 kg each for grazing with no supplement (GNS). Farm II had 30 animals with body weight of 216 +/- 28 kg each for grazing + oat hay (GOH). Farm III had 33 animals body weight of 221 +/- 34 kg each for grazing + highland barely straw (GBS). The calving rates of the cows in GOH and GBS were 23 and 19% higher, respectively, than GNS cows (p < 0.01), and the highest rate reached 76.7% in GOH. The live weight loss of the cows in GNS was considerably higher (p < 0.01) than in the two other groups. Ten GOH cows and 12 GNS cows were used to collect milk samples for measuring the progesterone concentration using RIA kits provided by IAEA/FAO: Milk was sampled every five days from calving until 90 days postpartum. In the unsupplemented group, milk progesterone (P4) levels suggested that cows had started cyclic ovarian activity by 40 days postpartum, whereas only 25% had been observed in estrus. In the supplemented group, 80% of cows had started cyclic ovarian activity by the same time and 70% had been seen in estrus. Two types of cyclic activity in terms of progesterone changed were found. With Type I (normal), 50 and 80% of cows from GNS and GOH, respectively, had cyclic changes of P4 in milk at 40 days postpartum. With Type II, the P4 levels in the milk remained 0.89 ng/ml until 90 days postpartum. A total of 46 grazing cows between five and 13 years of age (body weight 214 +/- 68 kg) was used to collect blood samples to measure concentrations of nutrient of metabolites at two weeks pre-calving and at two weeks, two months and four months postcalving, respectively. The concentrations of nutrient metabolites [albumin, globulin, urea, beta-hydroxybutyrate (BHB) and inorganic phosphorus] suggested general underfeeding of energy and protein in the winter/late pregnancy period with some recovery in lactation. Energy constraints appeared again as the summer progressed. No dietary phosphate deficiency was found. BHB and albumin testing on serum yaks could be a useful tool to identify poor nutritional status during the winter and so illustrate the need for supplementation.     

怀孕后期补饲浓缩料后对牦牛犊牛出生重的影响

[目的]为了增加高原生态环境下犊牦牛的初生重,提高犊牦牛成活率。[方法]本研究采取了在母牦牛怀孕后期补饲的方法,在怀孕后期,母牦牛自然放牧回圈后,每晚每头母牦牛补饲250g母牦牛浓缩精料补充料,连续补饲3个月。[结果]表明,试验组犊牦牛的初生重显著大于对照组(P0.01);而且母牦牛产后掉膘少,产后发情率高。[结论]对地处高海拔地区的自然放牧母牦牛围产期补饲母牦牛浓缩精料补充料后,能有效提高犊牦牛的初生重。     

娟姗公牛引入牧区生理机能变化与种用效果分析

为全面掌握娟姗种公牛在高寒牧区的适应性和生理机能变化情况,将6月龄娟姗种公牛引入牧区后观测生理机能变化情况,待体成熟后与牦牛开展自然交配。对牦牛自然交配和人工授精方式下的繁殖性能进行对比分析,结果表明：自然交配方式下母牦牛受胎率、产犊成活率、繁殖率比采用人工授精技术的母牦牛相应指标分别高19.26%、25.71%和23.12%,流产率和初生犊牛死亡率则比采用人工授精技术的母牦牛分别低8.54和5.64个百分点。同时对两种杂交技术下牦牛所产的后代娟犏雌牛进行犊牛生产性能对比分析,结果表明：自然交配母牦牛所产的后代娟犏雌牛犊比人工授精的母牦牛所产娟犏雌牛犊的初生重、12月龄体重、初胎初乳量、初胎年均泌乳量分别高4.92 kg、21.86 kg、0.36 kg、197.89 kg,两组数据经差异显著性检验,自然交配组的娟犏雌牛犊初生重、12月龄体重、初胎年均泌乳量均极显著的高于人工授精组的相应指标（P＜0.01),初胎初乳量差异显著（P＜0.05)。     

Strategies of supplementation of female suckling calves and nutrition parameters of beef cows on tropical pasture

The performance of female calves in creep feeding under different strategies of supplementation and milk production, intake, and digestibility of grazing Nellore and crossbred cows (Nellore?×?Holstein) during the dry-rainy transition season were assessed. Forty-four female beef suckling calves, with initial age between 90 and 150?days and average initial body weight of 117.7?±?4.3?kg, and their respective dams (24 Nellore and 20 crossbred) with average initial body weight of 417.5?±?8.3?kg, were used. The experimental treatments consisted of: control group-mineral mixture only; strategy 1-supplementation from 112?days prior to weaning (0.375?kg/animal/day); strategy 2-supplementation from 112?days prior to weaning, in increasing amounts of 0.15, 0.30, 0.45, and 0.60?kg/animal/day through the four experimental periods, respectively; and strategy 3-supplementation from 56?days prior to weaning (0.750?kg/animal/day). Calves from strategy 1 had greater (P??0.05) for nutrient digestibility among genetic types. It can be concluded that strategies of supplementation that present an equitable distribution of supplement provides greater weight gain in suckling female beef calves. Crossbred cows produce more milk and present greater DMI than Nellore cows. There are no differences in the nutrient digestibility between Nellore and Nellore × Holstein crossbred cows.     

新疆帕米尔牦牛生产性能的试验研究

[目的]为了探讨新疆帕米尔牦牛的生长发育、繁育性能及泌乳性能等特性。[方法]选取新疆帕米尔母牦牛50 头,通过非配对法人工受孕,检测母牛受配率和受胎率等繁育性能指标,记录产奶量、乳脂指标等评价泌乳性能,并在犊牛初生后分别于第0、1、3、6、12、18及24月龄时测量体重、体尺、体斜长等生长指标。[结果]18月龄新疆帕米尔牦牛的体重达343 kg,显著高于同时期的其他市售牦牛,证明新疆帕米尔牦牛的生长性能良好;繁殖率在75%以上,受胎率在90%以上,发情期集中在8月,繁殖成活率在90%以上,犊牛断奶成活率高达98%,证明新疆帕米尔牦牛具有良好的繁育性能;牛乳的乳脂率和乳蛋白率都达到生乳食品安全国家标准,产奶量也属于同类中的偏上水平,表明新疆帕米尔牦牛具有优良的泌乳性能。[结论]新疆帕米尔牦牛具有生长发育快、生产性能好、经济价值高等优势,是一种乳肉役兼用型的地方优良牦牛品种。     

补饲精料对青草期放牧牦牛增重的影响

在青草期进行８８天放牦牛放牧加补饲精料试验。试验组和对照组分别有混合群牦牛１０３头，６２头，试验每日每头补饲混合精料０．２５ｋｇ。试验结果：２岁牦牛增重效果最好，增重率提高２０．１个百分点，３岁牦牛次之，增重率提高１４．５个分点，４岁牦牛最差，增重率４．０个百分点；在同，４岁牦牛差异不显著。     

Effect of restricted suckling on milk yield,composition and flow,udder health,and postpartum anoestrus in grazing Holstein cows

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.     

Effect of calves’ supplementation on performance, nutritional and behavioral characteristics of their dams

The effects of supplementation of beef calves on weight gain, intake and digestibility of pasture, milk production and composition of their dams, and behavior of the pair cow–calf were assessed. Fifty-five beef cows with an initial average body weight of 449?±?8 kg and their respective offspring, with an initial average body weight of 138?+?3 kg and aged between 90 and 150 days, were used. Animals were submitted to an experimental period of 112 days. The experimental treatments consisted of: control?=?mineral mixture only, plan 1?=?high protein and high carbohydrate multiple supplement, plan 2?= high protein and low carbohydrate multiple supplement, plan 3?=?low protein and high carbohydrate multiple supplement, and plan 4?=?low protein and low carbohydrate multiple supplement. About 25 and 12.5 % of the protein requirements were supplied by the high and low protein supplements, respectively, and 15 and 7.5 % of total digestible nutrient requirements by the high and low carbohydrate supplements, respectively. Grazing behavior, performance, milk production, milk composition, intake, and digestibility of the cows were not affected (P?>?0.05) by the supplementation of the calves. The supplemented calves had greater (P?<?0.05) performance (as measured by final body weight, average daily gain, and final body condition score), intake and idle time, and lower (P?<?0.05) grazing time, but supplementation did not affect (P?>?0.05) suckling time and suckling frequency. It can be concluded that supplementation affects the behavior and feed intake of calves. However, it does not affect the suckling time and suckling frequency of calves. Additionally, performance, milk production, nutritional characteristics, and behavior of their dams are not affected.     

Seasonal and nutrients intake regulation of lipoprotein lipase (LPL) activity in grazing yak (Bos grunniens) in the Alpine Regions around Qinghai Lake

Lipoprotein lipase (LPL) is considered as a key enzyme in the lipid deposition and metabolism in tissues. To better understand fat cycling in grazing yak to adapt to the harsh environment on the Qinghai-Tibetan Plateau, and we have therefore explored seasonal and nutritional regulation of LPL in adipose tissue, liver and skeletal muscle. Sixty 3 year old growing yaks (BW. 120.3 ± 15.28 kg) were subdivided into six groups, each used to determine effects on chemical body composition and LPL activity in different tissues. The alpine pastures had the highest Crude protein (CP, 11.06%) contents and the gross energy (GE, 11.49 MJ/kg) in summer. Growth rates and body fat content were responsive to CP and GE intake regimen. Late spring up-regulation of LPL activity in the subcutaneous adipose tissue was consistent with a pronounced increase of body weight (BW) and whole body fat content. The highest LPL activity in the skeletal muscle was found in September (774 ± 64.1 mU/g tissue), which may serve to cover the increased energy demands for compensatory growth and maintenance of adiposity in the coming cold season. Furthermore, the seasonal regulation of LPL involves some factors in addition to insulin and triglycerides (TG). These results suggest that yaks could rely, in part, on LPL activity to adapt to the harsh forage environment. During the growing season, an enhanced synthesis of LPL production in the adipose tissues along with mechanisms for the recycling of fat contributes toward the rapid recovery of body weight.     

物候期对放牧牦牛瘤胃液、牧草中脂肪酸及乳脂中共轭亚油酸组成的影响及其相关性分析

为研究牧草物候期对其脂肪酸组成和放牧牦牛乳中共轭亚油酸（CLA）含量的影响及其相关关系,本研究在甘肃省甘南牧区选取平均体重为（234.9±10.5） kg的10头带犊甘南牦牛作为研究对象（自然放牧）,分别于牧草返青期、盛草期、枯草期采集试验牦牛采食牧草、乳和瘤胃液,分别测定瘤胃液、牧草中脂肪酸及乳脂中共轭亚油酸组成,并分析其相关关系,以期探明牧草物候期对牦牛瘤胃液和牧草中脂肪酸组成与放牧牦牛乳中共轭亚油酸含量的影响及其变化规律。结果表明：物候期显著影响了牧草中月桂酸、肉豆蔻酸、棕榈酸、硬脂酸、亚油酸、亚麻酸、总脂肪酸、多不饱和脂肪酸、多不饱和脂肪酸/总脂肪酸（P<0.05）,盛草期牧草中月桂酸、肉豆蔻酸、棕榈酸、亚油酸、亚麻酸、总脂肪酸、多不饱和脂肪酸、多不饱和脂肪酸含量/总脂肪酸均显著高于返青期和枯草期（P<0.05）;物候期显著影响了牦牛乳中共轭亚油酸异构体c9t11、共轭亚油酸异构体t10c12和共轭亚油酸总含量（P<0.05）,盛草期放牧牦牛乳中共轭亚油酸异构体c9t11、共轭亚油酸异构体t10c12和共轭亚油酸总含量显著高于返青期和枯草期（P<0.05）;物候期显著影响了牦牛瘤胃pH值、乙酸、丙酸、乙酸/丙酸、异丁酸、丁酸、异戊酸、戊酸、总挥发酸和反式11-油酸含量（P<0.05）,盛草期牦牛瘤胃乙酸、丙酸、丁酸、戊酸总挥发酸和反式11-油酸含量显著高于返青期和枯黄期（P<0.05）;牧草粗蛋白、粗脂肪、无氮浸出物、单宁酸、总脂肪酸和瘤胃液pH值与放牧牦牛乳中CLA含量显著正相关（P<0.05）,粗纤维和粗灰分与放牧牦牛乳中CLA含量显著负相关（P<0.05）,多不饱和脂肪酸（PUFAs）和瘤胃总挥发酸（TVFA）与放牧牦牛乳中CLA含量无显著相关关系（P>0.05）。     

Seasonal changes in weight and body composition of yak grazing on alpine-meadow grassland in the Qinghai-Tibetan plateau of China

Forty-five male yaks (born April 2001) were studied to determine how seasonal changes on the Qinghai-Tibetan plateau affected BW and body composition. Thirty yaks were weighed monthly from birth to 26 mo of age to determine seasonal changes in BW. The remaining 15 yaks were allocated randomly to five groups (three yaks per group), designated for slaughter at 13, 15, 18, 22, and 25 mo to measure seasonal effects on body chemical composition. All yaks were grazed on the alpine-meadow grassland of the plateau without any supplementation. All BW and body composition data were calculated on an individual basis. Body weight and body composition data were both compared across seven growth periods spanning 2 yr and defined by season. From April (birth) to December 2001 of the first growing season, yak BW increased (P < 0.01); however, during the subsequent cold season (December 2001 to May 2002), BW decreased (P < 0.01). The second growing season ran from May 2002 (13 mo of age) to October 2002 (18 mo of age), and the second live weight-loss season ran from October 2002 until May 2003. The weight loss experienced by yaks during the first weight-loss season was 25.64% of the total weight gain in the first growing season. The weight loss experienced by yaks during the second weight-loss season was 29.73% of the total weight gain in the second growing season. Energy retention in the second growing season was 291.07 MJ, 50.8% of which was consumed during the subsequent cold season. Energy accumulation in the summer (from May to July) and fall (from July to October) of the second growing season did not differ (5.01 and 6.30 MJ/kg of EBW gain, respectively; P = 0.63). The energy mobilized during the second winter (from October 2002 to February 2003) was 16.49 MJ/kg of EBW, and in the second spring (from February to May 2003), it was 9.06 MJ/kg of EBW. These data suggest that the decrease in grazing yak BW during the first cold season is much less than during the second cold season, and that the energy content per unit of BW mobilized is greater (P = 0.02) in winter than in spring. Results from this study demonstrate highly efficient compensatory growth in grazing yaks following the first weight loss period during the first cold season. This benefit could be exploited by herders to improve yak production. Yaks may have developed a type of self-protection mechanism to overcome the long cold seasons in the Qinghai-Tibetan plateau.     

带犊牦牛同期发情与自然发情繁殖效果比较

[目的]为了对比带犊牦牛同期发情与自然发情繁殖效果的差异,作者根据实施的科研项目进行了两组试验,以便为甘南牦牛产业高质量发展提供参考资料。[方法]于繁殖季节在试验组母牦牛阴道内放置“孕激素阴道栓”并肌肉注射“氯前列稀醇”(CIDR+PG)诱发牦牛集中发情。[结果]结果表明,甘南牦牛在当年生产后,通过犊牛统一断奶,改变营养供给,产后3个月试验组和对照组母牦牛自然发情率分别为8%和19.2%。试验组母牦牛应用“放置孕激素阴道栓+肌肉注射氯前列稀醇”方法诱导发情后,总发情率达89.1%。试验组带犊母牦牛激素处理后受胎率为89.1%,对照组母牦牛自然发情率较低,自然交配后受胎率为100%。试验组和对照组母牦牛繁殖率、犊牛成活率分别为86.9%和19.2%、97.6%和100%,试验组犊牛的平均初生重、断奶重、6月龄重分别比对照组高1.51 kg、2.37 kg、3.28 kg,经差异显著性检验,试验组犊牛相关年龄段体重与对照组犊牛对应指标相比,初生体重差异显著(P<0.05),断奶重和6月龄体重差异极显著(P<0.01)。[结论]使用外源性激素诱发带犊母牦牛当年集中发情,母牦牛当年...     

不同断奶模式对犊牦牛生长发育、血清生化指标及抗氧化能力的影响

【目的】 本研究通过比较不同断奶模式对犊牦牛生长发育、血清生化指标及抗氧化能力的影响,以期探索科学的犊牦牛早期培育模式。【方法】 选取体重相近、健康的新生犊牦牛24头,随机分为3个处理组,每组8头,公母各半。对照组（GF）犊牦牛出生后在天然牧场内随母放牧哺乳;早期断奶组（EW）犊牦牛随母放牧哺乳至15日龄时隔离母犊,逐渐过渡为饲喂代乳粉,提供开食料及天然牧草自由采食,至犊牦牛固体饲料采食量达到0.5 kg/d时停喂代乳粉,90日龄后停喂开食料转入天然牧场放牧饲养;早期断奶＋益生菌组（EWP）断奶过程同EW组,并在代乳粉、开食料中添加复合益生菌（乳酸杆菌、芽孢杆菌、酵母菌,≥9.98×10¹¹ CFU/g）。分别于犊牦牛30、60、90、150日龄时测定体重及体尺指标,于30、60、90日龄晨饲前采集犊牦牛颈静脉血,测定血清中生化指标、激素、免疫球蛋白水平及抗氧化能力指标。【结果】 30日龄时,EW、EWP组犊牦牛体重、体尺,血清葡萄糖（GLU）、甘油三酯（TG）、胆固醇（CHO）,生长激素（GH）、胰岛素样生长因子1（IGF-1）,以及免疫球蛋白A （IgA）、免疫球蛋白G （IgG）水平均显著低于GF组（P<0.05）,EW组皮质醇水平显著高于GF组（P<0.05）;60~150日龄各组犊牦牛体重、体尺均无显著差异（P>0.05）;60日龄时,EW、EWP组犊牦牛血清IGF-1以及谷胱甘肽过氧化物酶（GSH）含量均显著高于GF组（P<0.05）;90日龄时EW、EWP组犊牦牛血清GLU、尿素氮（BUN）、IGF-1、甲状腺素（T₄）及IgA水平均显著高于GF组（P<0.05）,且EWP组血清TG、GH含量及过氧化氢酶（CAT）活性均显著高于GF组（P<0.05）。【结论】 与随母放牧哺乳模式相比,两种早期断奶方式在断奶初期（30日龄）对犊牦牛均产生了一定负面影响,但在断奶后补饲代乳粉与开食料有利于改善犊牦牛后期的生长发育、营养代谢、机体免疫与抗氧化能力,且补充益生菌能够缓解犊牦牛的早期断奶应激,并对犊牦牛生长发育及抗氧化能力的提升有进一步促进作用。     

生长期牦牛的氮代谢及补氮技术研究

本项目在放牧条件下 ,系统地研究了生长期耗牛对不同季节牧草蛋白质的采食、消化、利用 ,并得出了牦牛在维持状态下 ,不同生长速度下的蛋白质需要量 ,还研究了牦牛对非蛋白氮的消化与利用。本项目系统地研究了高寒草甸草场牧草营养的季节动态 ,实测了各时期牧草的生物量、保存率和营养成分变化。在上述2项研究的基础上 ,本项目比较了在全年之间、牧草与家畜之间蛋白质的供需平衡情况 ,所得到的冷季与暖季增重总数据与生产实践十分吻合 ,实测得到了冷季缺额数据。针对冷季蛋白质供应的缺额 ,筛选了几种直接补氮方法。发现在能量蛋白比适当的情况下 ,用糖蜜尿素舔砖自由采食 ,可使牦牛在约200天的冷季内 ,得到的可消化蛋白增加35 %左右 ,接近维持需要水平 ,从而大大地减少体重损失。在暖季用施肥方法间接补氮 ,也可以收到同样效果 ,但2种办法只能使氮的供应达到维持水平 ,使放牧牦牛在安全越冬的条件下 ,达到不减重或少减重     

Effect of Pre- and Post-Partum Feed Supplementation on the Productive and Reproductive Performance of Grazing Primiparous Brahman Cows

This experiment studied the combined effect of pre- and post-calving feed supplementation on the productive and reproductive performance of primiparous Brahman cows. The animals were 4 years old (420 kg live weight) and pregnant, and grazed rotationally on Stargrass (Cynodon nlemfuensis) pastures. Supplementation was given before and after (T1, n = 15), only before (T2, n = 15) or only after (T3, n = 16) calving, and there was an unsupplemented control (T4, n = 16). The supplement (1.5 kg/animal per day, 13.4 MJ digestible energy/kg dry matter and 20% crude protein) was given for 45 days before and/or after calving. Changes in body weight and body condition score and the productive behaviour of the calves were similar (p>0.05) among treatments. The concentration of urea in the plasma was low in the control group (T4) before and after calving. The animals in all the groups had a poor reproductive performance. The percentage of cows in oestrus was higher (p<0.05) in T1 (73.3%) than in T3 (37.5%). The interval from calving to conception (148.7±53.7 days) and the pregnancy rate (48.5%) were similar (p>0.05) among the treatments. The level of supplementation offered before and/or after calving did not improve the pregnancy rate.     

果洛地区初生和1岁牦犊牛生长发育规律研究

对果洛地区1岁和当年生犊牛各7头，跟踪测定体重1年，结果：当年生犊牛体重呈平稳上升趋势，一年内增重44.61kg，1岁犊牛夏秋季生长较快，春季补偿生长迅速，科季体重有所下降，一年内增重42.06kg。     

Influence of restricted suckling and level of feed supplementation on postpartum reproductive performance of zebu and crossbred cattle in the semi-arid tropics.

This study was carried out in central Tanzania on a group of 45 Zebu and 37 crossbred cows which were 4 to 10 years old. At calving time, the animals were allocated to one of the 4 treatment groups. In addition to free access to grazing for all cows in the study, in group H:AR (n = 18), cows were fed a high level of concentrate supplementation (4kg/day) and calves were artificially reared; in group H:RS (n = 24), cows were fed a high level of concentrate supplementation (4kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. In group L:AR (n = 23) cows were fed a low level of concentrate supplementation (2kg/day) and calves were artificially reared; and in group L:RS (n = 17) cows were fed a low level of concentrate supplementation (2kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. Milk progesterone was used as a means of determining the postpartum resumption interval (PRI) and the interval from parturition to conception (PCI). The overall PRI was 47.4 +/- 0.4 days and was significantly affected by breed but not by calving season, with crossbred cows exhibiting a shorter PRI than Zebu cows. The effect of the treatments was significant, with cows in the group H:AR displaying a significantly shorter PRI than those in the other groups, while cows in group L:RS showed a significantly longer PRI than those in the other groups. The overall PCI was 149.5 +/- 3.7 days, and was not significantly affected by breed or calving season. The effect of the treatments was significant, with cows in the group H:AR having a significantly shorter PCI than cows in the other groups, while cows in group L:RS showed a significantly longer PCI than those in the other groups. Crossbred cows had higher live weights at calving (299.4 kg) than Zebu cows (272.6 kg), while all cows gained weight during the first 3 months after calving. The treatments had a significant effect on weight gain, with cows in the group H:AR gaining significantly more weight than those in the other groups. Cows which had high live weights at calving exhibited significantly shorter PRI and PCI than the lighter cows. Animals which had gained more than 5 kg during the first month after calving, or which had gained more than 8 kg during the first 3 months after calving, showed significantly shorter PRI and PCI than cows which had gained less weight. The results show that the calf rearing system and the level of feed supplementation interact with each other and can influence the postpartum anoestrous period in Zebu and Zebu crossbred cattle. Increasing the level of nutrition in restricted suckling cows tended to improve the postpartum anoestrous period, but the positive effects of supplementation could not completely compensate for the negative effects of suckling.