Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran.
J Dairy Res. 2023 Aug;90(3):234-243. doi: 10.1017/S0022029923000444. Epub 2023 Aug 17.
This study aimed to conduct a meta-analysis using the random-effects model to merge published genetic parameter estimates for milk coagulation properties (MCP: comprising rennet coagulation time (RCT), curd-firming time (k20), curd firmness 30 min after rennet addition (a30), titrable acidity (TA) and milk acidity or pH) in dairy cows. Overall, 80 heritability estimates and 157 genetic correlations from 23 papers published between 1999 and 2020 were used. The heritability estimates for RCT, a30, k20, TA, and pH were 0.273, 0.303, 0.278, 0.189 and 0.276, respectively. The genetic correlation estimates between RCT-a30, RCT-pH, and RCT-TA were 0.842, 0.549 and -0.565, respectively. Genetic correlation estimates between RCT and production traits were generally low and ranged from -0.142 (between RCT and casein content) to 0.094 (between RCT and somatic cell score). Moderate and significant genetic correlations were observed between a30-pH (-0.396) and a30-TA (0.662). Also, the genetic correlation estimates between a30 and production traits were low to moderate and varied from -0.165 (between a30 and milk yield) to 0.481 (between a30 and casein content). Genetic correlation estimates between pH and production traits were low and varied from -0.190 (between pH and milk protein percentage) to 0.254 (between pH and somatic cell score). The results of this meta-analysis indicated the existence of additive genetic variation for MCP that could be used in genetic selection programs for dairy cows. Because of the moderate heritability of MCP and small genetic correlations with production traits, it could be possible to improve MCP with negligible correlated effects on production traits.
本研究旨在使用随机效应模型进行荟萃分析，合并已发表的奶牛乳凝结特性（MCP：包括凝乳酶凝固时间（RCT）、凝乳形成时间（k20）、凝乳酶添加后 30 分钟的稠度（a30）、滴定酸度（TA）和乳酸度或 pH）的遗传参数估计值。总共使用了 23 篇发表于 1999 年至 2020 年之间的论文中的 80 个遗传力估计值和 157 个遗传相关系数。RCT、a30、k20、TA 和 pH 的遗传力估计值分别为 0.273、0.303、0.278、0.189 和 0.276。RCT-a30、RCT-pH 和 RCT-TA 之间的遗传相关系数估计值分别为 0.842、0.549 和-0.565。RCT 与生产性状之间的遗传相关系数通常较低，范围从-0.142（RCT 与酪蛋白含量之间）到 0.094（RCT 与体细胞评分之间）。a30-pH（-0.396）和 a30-TA（0.662）之间观察到中等且显著的遗传相关。此外，a30 与生产性状之间的遗传相关系数较低到中等，范围从-0.165（a30 与产奶量之间）到 0.481（a30 与酪蛋白含量之间）。pH 与生产性状之间的遗传相关系数较低，范围从-0.190（pH 与乳蛋白百分比之间）到 0.254（pH 与体细胞评分之间）。荟萃分析的结果表明，MCP 存在可用于奶牛遗传选择计划的加性遗传变异。由于 MCP 的遗传力中等且与生产性状的遗传相关系数较小，因此有可能在对生产性状几乎没有相关影响的情况下改善 MCP。
