Weller J I, Ezra E
Institute of Animal Sciences, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel.
Israel Cattle Breeders Association, Caesaria Industrial Park 38900, Israel.
J Dairy Sci. 2016 Dec;99(12):9782-9795. doi: 10.3168/jds.2016-11155. Epub 2016 Oct 5.
The objective was to test the hypothesis that more frequent but less accurately analyzed milk components may give a more representative measure of a cow's total lactation production. Daily records for milk production and fat and protein concentration collected by the AfiLab recording system (Afimilk, Kibbutz Afikim, Israel) from January 2014 to January 2016 from 47 large kibbutz (communal) herds distributed throughout Israel with a total of 37,486 Israeli Holstein cows were compared with the same statistics derived from monthly test day records derived by Bentley and Foss milk analyzers at the central laboratory of the Israel Cattle Breeders Association. The lactation means for all traits were quite similar for the 2 methods in both parities, except for fat production, which was lower for the daily records. This finding corresponded to fat lactation curves, which showed that daily results were lower with low days in milk (DIM) but almost equal to the monthly results after 125 DIM. Relative to monthly records, daily records overestimated protein percentage before 150 DIM and underestimated protein percentage in the second half of the lactation. The standard deviation for first- and second-parity daily records scored by the monthly and daily system were least similar for fat percentage, but even for this trait the difference was no more than 0.1 percentage points. The standard deviations for complete lactation production were slightly lower for the daily results for all traits but protein production. First-parity heritabilities were higher for lactations computed from daily records for all traits except for protein percentage, but differences were not significant. For daily records, coefficients of determination to predict future milk, fat, and protein lactation production from truncated lactations were greatest and root mean squared errors were least if the mean production from the last 2 weeks before the truncation date was used to estimate future production. Daily first-parity partial lactations for milk, fat, and protein production with <150 DIM predicted future lactation more accurately than corresponding monthly partial lactations. With only 30 DIM, genetic correlations between predicted and actual lactations ranged from 0.73 to 0.79 for milk, fat, and protein production. Real-time daily recording of fat and protein concentration by the daily recording system may be preferable to monthly analysis for herd-management decisions and genetic evaluation. Further study is required to compare the results of individual cows in multiple lactations.
对牛奶成分进行更频繁但分析准确性稍低的检测，可能会给出更能代表奶牛全泌乳期产量的指标。将2014年1月至2016年1月期间，由AfiLab记录系统（以色列阿菲金基布兹的阿菲米尔克公司）从分布于以色列各地的47个大型基布兹（集体）牛群中收集的47486头以色列荷斯坦奶牛的日产奶量、脂肪和蛋白质浓度的每日记录，与以色列养牛者协会中央实验室通过本特利和福斯牛奶分析仪得出的月度测定日记录中的相同统计数据进行比较。两种方法得出的所有性状的泌乳期均值在两个胎次中都非常相似，但脂肪产量除外，每日记录的脂肪产量较低。这一发现与脂肪泌乳曲线相符，该曲线表明，日产奶量在泌乳天数较少时较低，但在泌乳125天后几乎与月度结果相等。相对于月度记录，每日记录在泌乳150天之前高估了蛋白质百分比，而在泌乳后期低估了蛋白质百分比。月度和每日系统对第一胎和第二胎每日记录的脂肪百分比的标准差最不相似，但即使是这个性状，差异也不超过0.1个百分点。除蛋白质产量外，所有性状的全泌乳期产量的标准差在每日记录结果中略低。除蛋白质百分比外，所有性状根据每日记录计算的第一胎泌乳期遗传力更高，但差异不显著。对于每日记录，如果使用截断日期前最后2周的平均产量来估计未来产量，那么从截断泌乳期预测未来牛奶、脂肪和蛋白质泌乳期产量的决定系数最大，均方根误差最小。产奶量、脂肪和蛋白质产量的泌乳天数<150天的第一胎每日部分泌乳期比相应的月度部分泌乳期更准确地预测未来泌乳期。仅用30天的泌乳天数，预测泌乳期与实际泌乳期之间的遗传相关性在产奶量、脂肪和蛋白质产量方面为0.73至0.79。对于牛群管理决策和遗传评估而言，通过每日记录系统实时每日记录脂肪和蛋白质浓度可能比月度分析更可取。需要进一步研究以比较多胎次个体奶牛的结果。
