应用DHI对某奶牛群生产性能的综合分析

应用DHI对某奶牛群生产性能进行综合分析,探索在奶牛牧场管理过程中,牛奶体细胞数SCC与奶牛产奶量、健康、胎次的关系,以期应用DHI提高奶牛生产性能。应用奶牛生产性能测定(DHI)体系对900头产奶牛进行测定和分析,发现在奶牛泌乳的各个阶段,随着牛奶体细胞数增高,各胎次奶牛产奶量呈逐渐下降趋势;体细胞数随着胎次的增加而上升,奶牛产奶量随奶牛胎次的变化而变化。奶牛存在产犊间隔长,繁殖障碍和营养问题,需采取相应的改进措施。     

新产牛常见疾病防控

新产牛,即产犊至产后21 d的泌乳牛,该阶段的牛群最为敏感.牧场新产牛的饲养管理好坏,不仅直接或间接地影响奶牛整个胎次产量潜力的发挥,更影响到每头奶牛为牧场带来的收益.因此,在日常管理中应当非常注意对新产牛的常见疾病进行防控,以达到最佳的生产管理.     

我国荷斯坦奶牛体重体尺随胎次、泌乳和妊娠月龄的变化研究

为了解我国荷斯坦奶牛体重体尺（十字部高和胸围）随胎次、泌乳及妊娠月龄的变化情况,本研究选取我国西北、华北、中原和南方地区规模化牧场,于2019年7—11月分别对467头第1～5胎次泌乳1月的荷斯坦奶牛进行体重测定,对1 668头第1～5胎次奶牛进行体尺测量,对6 711头第1～3胎次泌乳1～10月奶牛、4046头第2～4胎次妊娠3～10月龄奶牛进行体重测定。使用单因素方差分析分别分析胎次、泌乳及妊娠月龄对奶牛体重体尺的影响。结果表明：第3胎次奶牛体重显著高于第2胎次,二者均显著高于第1胎次,3胎次后奶牛体重无显著变化,平均体重超过我国成年奶牛650 kg标准;第2～5胎次奶牛的十字部高无显著差异,均显著高于第1胎次;第1～4胎次奶牛的胸围随胎次增加而显著增加;各胎次奶牛泌乳2～4月时体重最低,在妊娠6、7月体重开始显著增加,至妊娠10月达到最高。本研究表明奶牛体重体尺受胎次、泌乳及妊娠月龄影响,规模化牧场需考虑奶牛生长规律配制日粮,设计牧场设施。     

北京奶牛生产性能测定中心参测牧场数据分析

奶牛生产性能测定(DHI)能够为牛群营养和遗传水平提供数据基础,本研究利用2020年6月-2021年5月北京奶牛生产性能测定中心(DHI中心)参测牧场数据来分析月度、季节、日产奶量、胎次对奶牛产奶量和乳成分的影响.结果表明,产奶量和乳成分的月度结果整体变化比较稳定,而受季节、日产奶量和胎次的影响较为明显.     

中国荷斯坦奶牛体况评分及其影响因素分析

为及时发现饲养管理中存在的问题并掌握奶牛的营养状况,本研究对呼图壁种牛场3个牧场的3 289头荷斯坦牛进行体况评分,对场、胎次、月龄嵌套胎次以及泌乳阶段等因素对奶牛体况评分的影响进行方差分析。结果表明:不同场、月龄嵌套胎次、泌乳阶段对体况评分的影响极显著(P<0.01),胎次对体况评分影响显著(P<0.05)。在实际生产过程中,要结合牛场本身的实际情况以及奶牛的生理时期和泌乳阶段的体况评分来调整饲养管理水平,以提高奶牛的生产性能。     

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。     

我国南方牧场奶牛流产情况调查与分析

笔者通过调查,分析了我国南方地区几个牧场奶牛的流产现状,并根据流产易发的阶段和胎次、月份等,提出一些见解,以期为其他牧场防治奶牛流产提供一定参考依据。     

荷斯坦奶牛血常规指标随胎次变化规律研究

为比较不同胎次奶牛的生理状况,为奶牛管理和疾病诊断提供理论依据,本实验于2017年夏季测定了北京地区5个牛场不同胎次的健康荷斯坦泌乳牛18项血常规指标,利用SAS 9.4软件GLM过程分析血常规指标随胎次的变化规律。所采用的固定模型考虑牛场、胎次、泌乳天数、直肠温度、体况评分和体细胞评分等因素的影响。结果表明:白细胞计数、淋巴细胞比率、淋巴细胞绝对值、红细胞计数、红细胞压积随着胎次升高而降低(P<0.05),中性粒细胞比率、平均血红蛋白量、平均血红蛋白浓度、红细胞平均体积随着胎次升高而升高(P<0.05),其余指标随胎次变化均不显著。综上,高胎次奶牛更容易受细菌感染,心血管疾病和贫血患病风险增加,因此需要采取适当措施,降低高胎次奶牛的患病概率,延长其生产寿命,从而提高牧场经济效益。     

乳酸菌微生态制剂在提高奶牛产奶量方面的应用研究

为了探究乳酸菌微生态制剂在提高奶牛产奶量方面的作用,本试验选择3个牧场进行试验。每个牧场选取胎次、泌乳天数、产奶量相近的奶牛并分为2组,对照组饲喂基础日粮,试验组在此基础上以奶牛精饲料的5%添加乳酸菌微生态制剂,试验周期30d,每天测定奶牛产奶量。结果表明,添加乳酸菌微生态制剂能够提高奶牛产奶量,并且随着乳酸菌微生态制剂使用时间的延长,奶牛产奶量不断增加,可大大提高奶牛饲养效益。     

奶牛泌乳曲线参数最小二乘均值的估计

利用Ｗｏｏｄ模型，按照总群、产犊胎次、产犊年份和不同牧场四种取样方法对黑白花奶牛泌乳曲线参数进行估计，并且进而估计不同取样角度下曲线参数的最小二乘均值的结果表明，按胎次、年份和牧场取样提高了样本的同质性和估计结果的准确性。通过方差分析剔除胎次、产犊年份、牧场及公牛的影响所获得的总群泌乳曲线参数呈现出最低的标准误。     

杨凌地区奶牛乳中共轭亚油酸含量测定及其影响因素

随机抽取杨凌地区80头荷斯坦泌乳奶牛的240个乳样，采用紫外分光光度计检测乳样中共轭亚油酸（CLA）含量。结果表明：杨凌地区奶牛乳中共轭亚油酸含量平均为2．7±0．17（mg／g fat）；奶牛乳中共轭亚油酸含量受多种因素的影响，场地、年龄、胎次、乳脂率、产奶量等均影响乳中共轭亚油酸的含量。随着年龄、胎次的增加．共轭亚油酸含量上升，不同场地奶牛乳样中共轭亚油酸含量差异较大（P〈0．05）。     

TMR粒度对日粮消化率与奶牛生产性能的影响

TMR粒度对奶牛健康养殖起着至关重要的作用,本研究选取泌乳天数、胎次、产奶量相近的200头奶牛进行配对试验,饲喂不同粒度的相同日粮,采集粪样、记录干物质采食量、收集DHI数据进行配对T检验分析。结果表明,TMR粒度较大的试验组奶牛日粮消化率较高,产奶量及乳脂率有升高的趋势,但差异不显著。     

酵母蛋白饲喂泌乳奶牛试验报告

本试验通过在荷斯坦泌乳牛日粮中添加酵母蛋白部分替代豆粕,研究其对泌乳牛干物质采食量、产奶量、乳成分及身体健康情况的影响,选取400头胎次、产奶量相近的中国荷斯坦泌乳牛分为对照组和试验组各200头,试验组每头牛每天饲喂500g酵母蛋白,通过60d的试验,结果表明试验组和对照组奶牛平均日产奶量差异不显著（P〉0.05）,分别为32.54kg/d与32.34kg/d。在产奶量不变的基础上,试验组平均干物质采食量降低1.7kg（DM）/d,产奶效率提高,与对照组相比差异极显著（P〈0.01）。     

Cow effects and estimation of success of first and following inseminations in Dutch dairy cows

The objective of this research was to determine the contribution of cow factors to the probability of successful insemination accounting for the serial number of inseminations in analysis. The investigation was performed with 101,297 insemination records in 51,525 lactations of different cows from 1368 herds obtained from the Dutch milk production recording database. Cows that had a first insemination (AI) between 40 and 150 days post-partum with one or more inseminations (≤6 inseminations) were selected. An insemination was defined successful when not followed by another insemination and when the cow calved between 267 and 295 days after insemination, or when the cow was culled between 135 and 295 days after the last insemination. Breed, parity, days in milk, lactation curve characteristics, milk production traits, moment of AI related to peak milk yield time (before or after peak milk yield), the last calf (female, male, twin or stillbirth) and season of insemination were selected as independent parameters for a model with successful rate of insemination as dependent parameter. A multivariable logistic regression model was used within cow and farm as a random effect. The probability of successful insemination was the highest in the first insemination and decreased in the following inseminations. However, the success rate of all inseminations increased in a later stage of lactation. The improvement in the successful inseminations in a later stage of lactation was better in multiparous cows than in first parity cows. Insemination in summer and before peak milk yield time reduced the success of insemination. The success rate was the lowest in 100% Holstein Friesian cows compared with other breeds and was the highest when the last calf was a female calf compared to a male calf, twin or stillbirth. In conclusion, the success of first and following inseminations depended on parity, breed, season of insemination, last calf status, daily milk yield at insemination date, serial insemination number and days in milk at insemination date.     

Studies on the replacement policies in dairy cattle. III. Influence of variation in reproduction and production

The optimum policy of insemination and replacement of dairy cows was determined by the dynamic programming technique. The model used in the previous study was extended to allow variation in time of conception. From 2 to 7 months after calving three alternatives were considered for an open cow namely (a) inseminating the cow, with a calculated probability of success, (b) leaving her open, and (c) replacing her immediately. When it was profitable to leave a cow open, the optimum time for replacement during the lactation period was determined.The minimum production level for insemination to be the optimum choice depended on the stage of lactation and the parity of the cow. In the optimum situation the average calving interval was 371 days, while 13% of the cows had an interval of 14 months or longer.The optimum policy was greatly affected by changes in the replacement heifer price. Changes in the probability of conception and persistency of milk production had significant but smaller effects. In herds with a smaller decline in production after the peak, insemination should be continued for longer than in herds with a larger decline.The relation between production and calving interval that resulted from the optimum policy was determined. When a measure of milk production was used that was not affected by gestation, the average correlation was 0.09. The correlation increased to 0.35 when the total 305-day production was used.     

Variability of acetone in milk in a large low-production dairy herd: a longitudinal case study

The objective of this study was to relate acetone in milk with cow and management factors in one low producing dairy herd (5260 kg milk per 305-day lactation). Milk acetone was measured in regular monthly milk samples one to three times within 100 days of lactation in 4433 lactations (2639 cows, 7800 measurements) from one herd over a period of 32 months (1988-91). Associations between milk acetone and cow factors and surrogate measures of management were evaluated by variance components of multiple fixed effect models. Lactation stage, calendar month of study, production groups and milk yield were strong, and percentage milk fat and parity were weak predictors of milk acetone. There was a trend of increasing body weight loss from the first to the second month of lactation with increasing milk acetone level. A substantial increase in milk production in 1991 was accompanied by an almost twofold rise in milk acetone. It was concluded that environmental parameters had strong relationships with milk acetone even in this low-producing herd.     

Loser cows in Danish dairy herds: definition, prevalence and consequences

During the last few years, many Danish dairy farmers have expressed increasing concerns regarding a group of cows, which we have chosen to term ‘loser cows’. Until now, a loser cow has not been described scientifically. We defined a loser cow on the basis of a clinical examination of the cow. A total of 15,151 clinical examinations were made on 6,451 individual cows from 39 randomly selected, large Danish dairy herds with loose-housing systems using a clinical protocol. Scores for the clinical signs lameness, body condition, hock lesions, other cutaneous lesions, vaginal discharge, condition of hair coat and general condition were converted into a loser cow score. Cows with a loser cow score of 8 or more were classified as loser cows. The overall prevalence of loser cows was 2.15%, 4.50% and 2.98% during the first, second and third round of herd visits, respectively.

The associations between the loser cow state and milk production, mortality, morbidity, culling and workload for the farmer were evaluated using data from herd visits and from the Danish Cattle Database and a number of different statistical techniques. It was concluded that the loser cow state has significant negative consequences for both the farmer and the cow. On average, loser cows yielded 0.61 to 2.24 kg energy corrected milk less per day than non-loser cows depending on parity. Hazard ratio for death or euthanasia was 5.69 for loser cows compared to non-loser cows. Incidence rate ratio for disease treatments was 0.69 for non-loser cows compared to loser cows. Loser cows were often culled in an ‘unfavourable’ way and generally caused extra workload for the farmer.

A simplified version of the loser cow score was evaluated and is recommended for future research and use in practice.     

复合酶对奶牛产奶量和乳成分的影响

本试验旨在研究复合酶对奶牛产奶量和乳成分的影响。选择胎次、泌乳天数、产奶量相近的健康荷斯坦泌乳牛30头,随机分为2组,即试验组和对照组,试验组每日在TMR中添加复合酶制剂50g。结果显示,试验组奶牛日均产奶量对比照组提高了6．6％,差异显著（P〈0．05）;试验组乳蛋白率比对照组提高0．19％,差异显著（P〈0．05）,乳脂率比对照组提高0．3％,差异显著（P〈0．05）,乳糖含量比对照组提高0．2％;经济效益每天每头奶牛比对照组多盈利3．88K。说明每日在奶牛TMR中添加50g复合酶,可提高奶牛产奶量,改善牛奶品质,增加经济效益。     

Early lactation dairy cows: Development of equations to predict intake and milk performance at grazing

The objectives of this study were to examine the effect of parity and days in milk (DIM) on dry matter intake (DMI) and actual milk yield (MY_Act) of grazing spring calving dairy cows in early lactation (< 100 DIM) and to develop equations to predict DMI and milk yield for grass based systems of milk production. A dataset containing 335 observations from 134 Holstein Friesian dairy cows was assembled from two early lactation grazing studies. Observations were available for primiparous (n = 130) and multiparous (n = 205) cows during periods of DMI measurement using the n-alkane technique. Animal performance was divided into two classes of DIM: less than 50 DIM (< 50 DIM) or between 51 and 100 DIM (> 50 DIM). Parity and DIM had a significant effect on grass DMI (GDMI), total DMI (TDMI), MY_Act and milk composition. TDMI increased with parity and DIM and ranged from 13.4 kg/cow per day (primiparous animals, < 50 DIM) to 20.1 kg/cow per day (multiparous animals, > 50 DIM). Actual MY increased with parity and decreased with DIM (range: 24.1 kg/cow per day (primiparous animals, > 50 DIM) to 33.0 kg/cow per day (multiparous animals, < 50 DIM)). Multiparous cows had greater bodyweight (BW) and lower BCS than primiparous cows. In the early lactation period a number of variables had a significant effect on GDMI, TDMI and milk yield. These predictor variables included BW, BCS, potential milk yield (MY_Pot), DIM, daily herbage allowance (DHA; > 4 cm), concentrate level and parity. The equations accounted for 79%, 83% and 86% of the variation in GDMI, TDMI and milk yield, respectively. Actual milk yield was always below the MY_Pot of the cows, the mean difference was 5.8 kg/cow per day. As DHA and concentrate level increased, the difference between MY_Act and MY_Pot reduced. This study supports the concept that immediately post-calving offering a grass based diet with a medium level of concentrate supplementation is sufficient to support high milk production in grazing dairy cows.     

Association between exposure to Neospora caninum and milk production in dairy cows

OBJECTIVE: To determine association between exposure to Neospora caninum and milk production in dairy cows. DESIGN: Prospective observational study. Animals: 565 Holstein cows. PROCEDURE: Cows were classified as seropositive or seronegative to N. caninum within 7 days after calving by use of a kinetic ELISA. Milk production was compared between seropositive and seronegative cows. RESULTS: On the basis of 305-day mature equivalent milk production data, seropositive cows produced less milk (2.8 lb/cow per day) than did seronegative cows. In addition, analysis of results throughout the first 300 days of lactation revealed that after adjusting for effects of lactation number, calving season, clinical mastitis, and lameness, milk weight of seropositive cows was 2.5 lb/cow per day less than that of seronegative cows. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to N. caninum was associated with a 3 to 4% decrease in milk production. A decrease in milk production of 800 lb/cow for a typical 305-day lactation represents a loss of $128/cow.