Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran.
Department of Animal Science, Faculty of Agriculture, University of Jiroft, Jiroft, Iran.
Trop Anim Health Prod. 2022 Aug 10;54(5):257. doi: 10.1007/s11250-022-03248-x.
The present study aimed to investigate the effect of censoring, the situations in which incomplete at the time, out of range, and/or delayed records were considered, in the estimation of genetic parameters for age at first calving (AFC) and days open (DO) in Iranian Holstein cows. The dataset included 281,772 records collected from 1991 to 2019 by the Vahdat Cooperative Company, a pioneer dairy farm in Isfahan Province, the central part of Iran. Five animal models including linear model (LM), penalty model (PM), modified penalty model (MPM), linear-threshold model (LTM), and modified linear-threshold model (MLTM) were used for genetic evaluation of the trait studied. The predictive ability of the models was assessed using cross-validation. The lowest mean square of error and highest r(y,y) were obtained under MLTM for AFC and under LTM for DO, indicating that MLTM and LTM are recommended for genetic evaluation of AFC and DO with censored records in Iranian Holstein cows, respectively. The prediction accuracy of the models for AFC was relatively similar, ranging from 0.46 (under LM) to 0.48 (under PM, LTM, and MLTM). For DO, prediction accuracy values ranged from 0.36 (under LM) to 0.47 (under PM and LTM). The posterior mean for heritability of AFC under MLTM was 0.11. There was no significant difference among posterior means for the heritability of AFC under different models. Therefore, LM is preferred for genetic evaluation of AFC in Iranian Holsteins, and taking censored records into account is unnecessary. The posterior mean for heritability of DO under LTM was 0.09. There were no statistically significant differences among the heritability estimates of DO under LTM, PM, and MLTM. But considering censored records for genetic evaluation of DO affects the estimation of heritability and improved model accuracy for this trait. Therefore, LTM is preferred and recommended for genetic evaluation of DO in Iranian Holsteins.
本研究旨在探讨删失的影响，即在时间、范围外和/或延迟记录的情况下，将其视为不完全记录的情况，对伊朗荷斯坦奶牛初配年龄（AFC）和开放天数（DO）遗传参数估计的影响。数据集包括 1991 年至 2019 年由伊朗伊斯法罕省先锋奶牛场 Vahdat 合作社收集的 281772 条记录。五种动物模型，包括线性模型（LM）、惩罚模型（PM）、修正惩罚模型（MPM）、线性阈值模型（LTM）和修正线性阈值模型（MLTM），用于研究性状的遗传评估。使用交叉验证评估模型的预测能力。在 AFC 下，MLTM 下的平均误差平方和最高 r(y,y)最低，在 DO 下，LTM 下的平均误差平方和最高 r(y,y)最高，表明 MLTM 和 LTM 分别推荐用于伊朗荷斯坦奶牛有删失记录的 AFC 和 DO 的遗传评估。模型对 AFC 的预测准确性相对相似，范围从 0.46（LM 下）到 0.48（PM、LTM 和 MLTM 下）。对于 DO，预测准确性值范围从 0.36（LM 下）到 0.47（PM 和 LTM 下）。在 MLTM 下，AFC 的遗传力后验均值为 0.11。在不同模型下，AFC 的遗传力后验均值没有显著差异。因此，LM 是伊朗荷斯坦奶牛 AFC 遗传评估的首选，不需要考虑删失记录。在 LTM 下，DO 的遗传力后验均值为 0.09。在 LTM、PM 和 MLTM 下，DO 的遗传力估计值没有统计学差异。但是，考虑到 DO 的遗传评估中的删失记录会影响遗传力的估计，并提高该性状的模型准确性。因此，LTM 是首选和推荐用于伊朗荷斯坦奶牛的 DO 遗传评估。
