COMPARISON OF DIFFERENT METHODS OF PREDICTING 305-DAY MILK-YIELD USING MEANS CALCULATED FROM WITHIN-HERD LACTATION CURVES
COMPARISON OF DIFFERENT METHODS OF PREDICTING 305-DAY MILK-YIELD USING MEANS CALCULATED FROM WITHIN-HERD LACTATION CURVES
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DOI：
10.1016/0301-6226(87)90049-2
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发表时间：
1987-07-01
期刊：
影响因子：
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通讯作者：
WILMINK, JBM
中科院分区：
文献类型：
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作者：
WILMINK, JBM
对305天泌乳期的未知par的预测通常基于回归模型。对于这些模型，需要知道已知的测试日产量和剩余泌乳产量之间的关系以及它们在环境影响类别内的平均值。由于环境的变化，手段可能会有很大差异。在这项研究中，提出了一个估计的方法，并比较了单回归（SR），多元回归（MR）和因子分析（FA）预测模型。MR和FA都使用所有已知的测试日收益率作为信息源。方法SR使用最后一个已知的测试日产量。在所有记录中估计每个牛群的泌乳曲线，并根据产犊年龄和季节进行调整。通过对产犊年龄和季节的后向调整，获得了属于某个产犊年龄-月份类别的一组奶牛的泌乳治愈。根据这些泌乳曲线（II型）计算预测所需的平均值。与平均值的相关性，这是直接计算的数据集（I型），范围从0.61至0.78的测试天，从0.51至0.69的剩余泌乳量。I型和II型平均值之间的平均差异几乎为零。使用II型平均值，SR、MR和FA之间无差异。当产后50天最后一次产奶量已知时，预测产奶量与实际产奶量之间的相关系数分别为0.87、0.88和0.88。第二类方法的使用导致了更精确的调整。
The prediction of the unknown par to fa 305-day lactation is usually based on regression models. For these models the relation between known test-day yields and remaining lactation yield as well as their means within classes of environmental effects need to be known. Owing to environmental changes, means may vary severely. In this study a procedure for estimation of the means is presented and single regression (SR), multiple regression (MR), and factor analysis (FA) models for prediction are compared. Both MR and FA use all known test-day yields as information sources. Method SR uses the last known test-day yield. Lactation curves were estimated per herd on all records, adjusted for age and season of calving. By back-adjustment for age and season for calving, lactation cures were obtained for a group of cows pertaining to a certain class of herd-age-month of calving. Means necessary for prediction were calculated from these lactation curves (Type II). Correlations with means, which were directly calculated in the data set (Type I), ranged from 0.61 to 0.78 for test-days and from 0.51 to 0.69 for remaining lactation milk yield. The average difference between Types I and II means was almost zero. Using Type II means, no differences were found between SR, MR and FA. The correlation between predicted and realized 305-day milk yield was 0.87, 0.88 and 0.88 respectively for parity 1, 2 and > 2, when the last test-day yield was known at 50 days postpartum. The use of Type II means resulted in a more precise adjustment.