Animal Breeding and Genetics, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 980-8572, Japan.
Animal Functional Morphology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 980-8572, Japan.
J Dairy Sci. 2024 Mar;107(3):1577-1591. doi: 10.3168/jds.2022-23075. Epub 2023 Oct 6.
Mastitis is one of the most frequent and costly diseases affecting dairy cattle. Natural antibodies (immunoglobulins) and cyclophilin A (CyPA), the most abundant member of the family of peptidyl prolyl cis/trans isomerases, in milk may serve as indicators of mastitis resistance in dairy cattle. However, genetic information for CyPA is not available, and knowledge on the genetic and nongenetic relationships between these immune-related traits and somatic cell score (SCS) and milk yield in dairy cattle is sparse. Therefore, we aimed to comprehensively evaluate whether immune-related traits consisting of 5 Ig classes (IgG, IgG, IgG, IgA, and IgM) and CyPA in the test-day milk of Holstein cows can be used as genetic indicators of mastitis resistance by evaluating the genetic and nongenetic relationships with SCS in milk. The nongenetic factors affecting immune-related traits and the effects of these traits on SCS were evaluated. Furthermore, the genetic parameters of immune-related traits according to health status and genetic relationships under different SCS environments were estimated. All immune-related traits were significantly associated with SCS and directly proportional. Additionally, evaluation using a classification tree revealed that IgA, IgG, and IgG were associated with SCS levels. Genetic factor analyses indicated that heritability estimates were low for CyPA (0.08) but moderate for IgG (0.37), IgA (0.44), and IgM (0.44), with positive genetic correlations among Ig (0.25-0.96). We also evaluated the differences in milk yield and SCS of cows between the low and high groups according to their sires' estimated breeding value for immune-related traits. In the high group, IgA had a significantly lower SCS in milk at 7 to 30 d compared with that in the low group. Furthermore, the Ig in milk had high positive genetic correlations between healthy and infected conditions (0.82-0.99), suggesting that Ig in milk under healthy conditions could interact with those under infected conditions, owing to the genetic ability based on the level of Ig in milk. Thus, Ig in milk are potential indicators for the genetic selection of mastitis resistance. However, because only the relationship between immune-related traits and SCS was investigated in this study, further study on the relationship between clinical mastitis and Ig in milk is needed before Ig can be used as an indicator of mastitis resistance.
乳腺炎是影响奶牛最常见和最昂贵的疾病之一。天然抗体（免疫球蛋白）和亲环素 A（CyPA），即肽基脯氨酰顺/反异构酶家族中最丰富的成员，在牛奶中可能作为奶牛乳腺炎抗性的指标。然而，CyPA 的遗传信息尚不可用，并且关于这些免疫相关性状与体细胞评分（SCS）和奶牛产奶量之间的遗传和非遗传关系的知识也很匮乏。因此，我们旨在通过评估与牛奶 SCS 的遗传和非遗传关系，全面评估由 5 种 Ig 类（IgG、IgG、IgG、IgA 和 IgM）和 CyPA 组成的奶牛测试日牛奶中的免疫相关性状是否可用作乳腺炎抗性的遗传指标。评估了影响免疫相关性状的非遗传因素以及这些性状对 SCS 的影响。此外，根据健康状况和不同 SCS 环境下的遗传关系，估计了免疫相关性状的遗传参数。所有免疫相关性状均与 SCS 显著相关且呈正相关。此外，使用分类树的评估表明，IgA、IgG 和 IgG 与 SCS 水平相关。遗传因子分析表明，CyPA 的遗传力估计值较低（0.08），而 IgG（0.37）、IgA（0.44）和 IgM（0.44）的遗传力估计值中等，Ig 之间存在正遗传相关性（0.25-0.96）。我们还根据牛的 sire 对免疫相关性状的估计育种值，评估了 SCS 低组和高组奶牛的产奶量和 SCS 之间的差异。在高组中，与低组相比，第 7 至 30 天牛奶中的 IgA 的 SCS 显著较低。此外，在健康和感染条件下，牛奶中的 Ig 之间具有很高的正遗传相关性（0.82-0.99），这表明在健康条件下的牛奶中的 Ig 可能与在感染条件下的 Ig 相互作用，这是由于基于牛奶中 Ig 水平的遗传能力。因此，牛奶中的 Ig 是乳腺炎抗性遗传选择的潜在指标。但是，由于本研究仅研究了免疫相关性状与 SCS 之间的关系，因此在将 Ig 用作乳腺炎抗性指标之前，还需要进一步研究临床乳腺炎与牛奶中 Ig 之间的关系。
