奶牛产后首次发情行为变化规律及影响因素分析

本实验旨在通过对奶牛场发情监测设备数据的综合分析,探究奶牛产后首次发情行为变化规律及胎次、季节、泌乳水平等因素对发情行为的影响,提高牛场数字化管理水平.本研究采集了2018年7月-2019年8月北京延庆某奶牛养殖场315头产后母牛首次发情信息,共计20475项相关数据,包括发情日期、活动量、反刍量、胎次、产奶量等,运用...     

Prevalence of Michigan dairy herds infected with Mycobacterium avium subspecies paratuberculosis as determined by environmental sampling

A cross-sectional, stratified random survey of Michigan dairy herds was conducted to estimate the prevalence of herds infected with Mycobacterium avium paratuberculosis (MAP), the causative agent of Johne's disease, in Michigan using targeted environmental sampling. One pooled sample each from the primary manure storage area and a high-traffic common cow area from each herd was collected and cultured for MAP using the ESP^® culture system II. A herd was classified as positive if at least one sample was culture positive for MAP. State, agricultural district, and herd size stratum prevalence were calculated. Information on past MAP testing and cattle purchase history was collected, and logistic regression was performed to determine their importance to the MAP status of the herd. One hundred twenty-seven herds were contacted, and 94 agreed to participate in the study. The environment of 38 (40.4%) herds cultured positive for MAP. MAP was found in all herds (n = 15) with greater than 200 lactating cows. Herds that had tested for MAP or purchased cattle in the previous 5 years were 4.6 and 3.1 times, respectively, more likely to be infected than herds that had not. MAP continues to be prevalent on Michigan dairy farms, especially those with greater than 200 lactating cows. The environmental sampling protocol used in this study is an economically attractive alternative for monitoring herd level prevalence and the progress of Johne's disease control programs at the state or national level. Implementation of such a program would aid states in monitoring Johne's control program progress, and guide changes over time.     

Estimation of milk production losses due to sub-clinical mastitis in dairy cattle in Costa Rica

Five dairy farms, situated on the slopes of the volcano Poás in the pre-mountain cloud forest ecological zone, Alajuela and Heredia Provinces, Costa Rica, provided data for estimation of the production losses due to sub-clinical mastitis. Within the same farm, cows with proven sub-clinical mastitis were matched with cows without signs of sub-clinical mastitis, according to breed, lactation number and days in lactation. A total of 529 cows were detected with sub-clinical mastitis, of which only 200 could be paired with control cows free of mastitis; each pair was used only once.

Crude milk production losses per cow with sub-clinical mastitis were estimated at 1.56 kg day⁻¹for daily milk yield. Milk production loss per affected quarter due to sub-clinical mastitis was estimated to be 17.6% on average. The decrease in milk production in heifers with sub-clinical mastitis did not differ significantly from the decrease in production in older cows. No significant difference in milk production loss was detected when the data were stratified on parity or the number of quarters affected.     

屡配不孕母牛发情开始后八天内血清促黄体素（LH）含量的变化

本实验采用放射免疫测定技术(RIA)分析了9头屡配不孕母牛和6头正常母牛于发情开始后8天内的血清促黄体素(LH)的含量变化。测定结果表明:屡配不孕母牛的LH排卵峰值低于正常母牛,其峰值分别为2.71±1.00ng/ml和4.70±1.71ng/ml,差异显著(P<0.025)。为了初步验证LH峰值与屡配不孕之间的关系,对20头屡配不孕母牛在发情开始至配种前肌肉注射外源性LH180IU,其配种后60天的受胎率为70％(14/20),而未用LH处理的11头屡配不孕母牛的受胎率为18％(2/11),两者差异极显著(P<0.01)。上述实验结果提示:体内LH排卵峰值降低可能是导致乳牛屡配不孕的重要原因之一。     

Nationwide seroprevalence of Neospora caninum among dairy cattle in Japan

Serum samples from 2420 clinically healthy dairy cattle, randomly selected from stored sera in 18 districts of Japan, were tested for the presence of Neospora caninum antibodies using an indirect fluorescent antibody test (titer > or =1:200). Nationwide seroprevalence is estimated at 5.7% (139/2420). Seropositive cattle were detected in all surveyed districts despite the evidence of confirmed case reports of bovine neosporosis, showing that N. caninum is widely distributed throughout Japan. Age-specific seroprevalence did not increase with cattle age, suggesting that Neospora infection is likely to be transmitted vertically rather than horizontally in Japan. Considering that N. caninum seropositive cows are thought to be more likely to abort, substantial fetal losses may be induced by N. caninum infection in Japan. Devising strategies are needed to reduce the economic impact on the Japanese dairy industry. This is the first study to investigate the nationwide seroprevalence of N. caninum in cattle in Asia.     

保护性赖氨酸对荷斯坦牛挥发性脂肪酸及菌体蛋白的影响

本试验选用3头装有永久性瘤胃瘘管和十二指肠瘘管的荷斯坦牛,分4个阶段,分别饲喂日粮Ⅰ(基础日粮+保护性赖氨酸Ⅰ30g/d)、日粮Ⅱ(基础日粮+保护性赖氨酸Ⅱ30g/d)、日粮Ⅲ(基础日粮+保护性赖氨酸Ⅲ30g/d)和日粮Ⅳ(基础日粮),研究以不同比例棕榈油脂肪粉包被的赖氨酸对瘤胃液挥发性脂肪酸和菌体蛋白的影响。结果表明,添加瘤胃保护性赖氨酸对瘤胃液挥发性脂肪酸和菌体蛋白均无明显影响(P>0.05)。瘤胃保护性氨基酸没有改变瘤胃内环境,不影响瘤胃微生物的生长和菌体蛋白的合成。     

奶牛生产寿命和产奶量的相关性研究

本研究利用陕西省西安市现代农业开发区第二奶牛场1990年～2002年间249头已淘汰奶牛的胎次及产奶量记录等资料,对奶牛的生产寿命即第一胎次至淘汰的泌乳天数和生产效益的关系进行了研究。结果表明,奶牛的生产寿命与终生产奶量之间存在强正相关,相关系数为0．99。奶牛的使用年限和产奶量之间存在显著的曲线相关(P＜0．05)。此外,研究结果表明,该奶牛场奶牛不同胎次产奶量以第5胎次为最高。     

热烫拉伸条件对乳扇拉伸性能和出品率的影响

本研究利用热处理的酸乳清对牛乳进行预酸化处理,研究不同热烫条件对乳扇热拉伸性和产量的影响,并对工艺条件进行优化。结果表明,乳扇热烫拉伸最佳工艺条件为温度70℃、pH6.0,该条件下乳扇的拉伸性较好并且出品率较高（7.11%）。     

CIDR与GnRH诱导同期发情效果比较

[目的]为了观察CIDR与GnRH诱导同期发情的效果。[方法]本实验利用GnRH＋PG＋GnRH和CIDR＋EB＋P4＋PG对荷斯坦奶牛进行同期发情。CIDR组：在奶牛发情周期的任意一天（发情当天除外）,于奶牛阴道内放CIDR同时肌注2mgEB和50mgP4,人为诱导卵泡的发生,在放入CIDR的第8d肌注PG;应用GnRH组与CIDR组同步进行同期发情处理：肌注GnRH7d后肌注PG,2d后再次肌注GnRH。[结果]表明：利用CIDR与Gn—RH两种同期方法同期发情率、情期受胎率差异均不显著。[结论]在实际生产中,GnRH便于操作,且发情略高于CIDR组。