Department of Animal Science, Pennsylvania State University, University Park 16802.
Department of Animal Science, Pennsylvania State University, University Park 16802.
J Dairy Sci. 2022 Jan;105(1):495-508. doi: 10.3168/jds.2021-20588. Epub 2021 Oct 14.
Among other regulations, organic cows in the United States cannot receive antibiotics and preserve their organic status, emphasizing the importance of prevention of illness and benefit of high genetic merit for disease resistance. At the same time, data underlying national genetic evaluations primarily come from conventional cows, drawing concern to the possibility of a genotype by environment interaction whereby the value of a genotype varies depending on the environment, and potentially limits the relevance of these evaluations to organic cows. The objectives of this study were to characterize the genetics of and determine the presence of genotype by environment interaction for health traits in US organic dairy cows. Individual cow health data were obtained from 16 US Department of Agriculture certified organic dairy farms from across the United States that used artificial insemination and maintained detailed records. Data were obtained for the following traits: died, lameness, mastitis, metabolic diseases (displaced abomasum, ketosis, and milk fever), reproductive diseases (abortion, metritis, and retained placenta), transition health events (any health event occurring 21 d before or after parturition), and all health events. Binary phenotypes (1 = diseased, 0 = otherwise) for 38,949 lactations on 19,139 Holstein cows were used. Genotypes from 2,347 cows with 87.5% or greater Holstein breed-based representation were incorporated into single-step multitrait threshold animal models that included stayability (1 = completed lactation, 0 = otherwise). Gibbs sampling was used. Genomic predicted transmitting abilities (gPTA) from national genetic evaluations were obtained for sires for production, fitness, health, and conformation traits. We approximated genetic correlations for sires using these gPTA and our estimated breeding values. We also regressed health phenotypes on cow estimated breeding values and sire gPTA. Heritabilities (± standard error) ranged from 0.03 ± 0.01 (reproductive diseases) to 0.11 ± 0.03 (metabolic diseases). Most genetic correlations among health traits were positive, though the genetic correlation between metabolic disease and mastitis was -0.42 ± 0.17. Approximate genetic correlations between disease resistance for our health trait categories and disease resistance for the nationally-evaluated health traits generally carried the expected sign with the strongest correlation for mastitis (0.72 ± 0.084). Regression coefficients carried the expected sign and were mostly different from zero, indicating that evaluations from primarily conventional herd data predicted health on organic farms. In conclusion, use of national evaluations for health traits should afford genetic improvement for health in US organic herds.
除其他规定外，美国的有机奶牛不能使用抗生素并保持其有机状态，这强调了预防疾病和利用高遗传优势提高抗病能力的重要性。同时，国家遗传评估的基础数据主要来自常规奶牛，这引起了人们对基因型与环境互作的关注，即基因型的价值取决于环境，并且可能限制了这些评估对有机奶牛的相关性。本研究的目的是描述美国有机奶牛健康性状的遗传特征，并确定基因型与环境互作的存在。个体奶牛健康数据来自美国 16 个美国农业部认证的有机奶牛场，这些奶牛场使用人工授精并保留详细记录。数据取自以下特征：死亡、跛行、乳腺炎、代谢疾病（真胃移位、酮病、产乳热）、生殖疾病（流产、子宫内膜炎和胎衣不下）、过渡健康事件（分娩前或后 21 天内发生的任何健康事件）和所有健康事件。使用了 19139 头荷斯坦奶牛 38949 个泌乳期的二元表型（1=患病，0=否则）。将 2347 头具有 87.5%或更高荷斯坦品种代表性的奶牛的基因型纳入包括可持续性（1=完成泌乳期，0=否则）的单步多性状阈动物模型中。采用 Gibbs 抽样。从全国遗传评估中获得了生产、适应性、健康和体型性状的 sire 基因组预测传递能力（gPTA）。我们使用这些 gPTA 和我们估计的育种值来估计 sire 的遗传相关性。我们还将健康表型回归到 cow 估计的育种值和 sire gPTA。遗传力（±标准误差）范围从 0.03±0.01（生殖疾病）到 0.11±0.03（代谢疾病）。健康性状之间的大多数遗传相关性为正，尽管代谢疾病与乳腺炎之间的遗传相关性为-0.42±0.17。我们健康性状类别的疾病抵抗力与全国评估的健康性状的疾病抵抗力之间的近似遗传相关性通常具有预期的符号，其中与乳腺炎的相关性最强（0.72±0.084）。回归系数具有预期的符号，且大多与零不同，表明主要来自常规畜群数据的评估预测了有机农场的健康状况。总之，在有机畜群中使用全国健康性状评估应能提高健康性状的遗传改良。
