Editing and modeling of milk production data for genetic evaluation of Murrah buffaloes

Abstract: The objective of this work was to assess the effect of editing and modeling of milk production data for genetic evaluation of Murrah buffaloes. Six strategies for evaluating milk production were analyzed: observed milk production (OMP); adjustment of milk production data to 305 (MP305) and 270 (MP270) days of lactation; removal of the 5 (MP5%) and 10% (MP10%) shortest lactation periods; and milk production along the lactation period as linear covariate (MPCO). Genetic parameters were estimated using the Bayesian inference, with heritability estimates of 0.19 to 0.23 and repeatability estimates of 0.35 to 0.36. Sires classified by OMP were high correlated to those classified by the other models, however, correlations to MP270, MP305 and MPCO decreased when considering only the best 20% sires. OMP showed greater differences in absolute mean deviations when compared with MPCO, MP270 and MP305. The strategies of analysis had similar heritabilities and stabilities. However, changes in the ranking of sires with better classifications, due to overestimation of genetic values, as occurred in the models MP305, MP270 and MPCO, may lead to a decrease in the genetic progress of the herd.

摘要：本研究旨在评估泌乳期奶产量数据的编辑与建模方法对摩拉水牛（Murrah buffalo）遗传评估的影响。本研究共分析了6种奶产量评估策略：实测奶产量（observed milk production，OMP）；将奶产量数据校正至305天泌乳期（MP305）与270天泌乳期（MP270）；剔除占比5%（MP5%）与10%（MP10%）的最短泌乳期记录；以及将泌乳期全程奶产量作为线性协变量（MPCO）。本研究采用贝叶斯推断（Bayesian inference）估计遗传参数，得到的遗传力估计值范围为0.19至0.23，重复力估计值范围为0.35至0.36。采用OMP划分的种公牛排名与其他模型划分的排名相关性较高，但仅选取排名前20%的种公牛时，其与MP270、MP305及MPCO的相关性有所下降。与MPCO、MP270和MP305相比，OMP的绝对均值偏差更大。各分析策略的遗传力与稳定性较为相近。然而，MP305、MP270与MPCO模型中出现的遗传值高估问题，会导致优质种公牛的排名发生变化，进而可能降低畜群的遗传进展。