基于牧场管理数据的奶牛健康性状定义及遗传参数估计

Definition and Genetic Parameters Estimation for Health Traits by Using on-Farm Management Data in Dairy Cattle

【目的】利用牧场管理数据定义奶牛健康性状,并对各健康性状进行遗传分析。为奶牛抗病选育和研究提供参考。【方法】收集了华北地区46个规模化牧场的奶牛健康事件记录,通过对原始记录中1 326种健康事件进行整理,将所有健康事件分为5类,并在每类中筛选出记录数相对较多的常见健康事件,共计18个。根据各健康事件在每个泌乳期内是否至少发生一次,定义了18个二分类的单一健康性状(观测值为0或1);为了考虑奶牛对某类健康问题的整体抗性,根据每个泌乳期内是否至少发生一次某类健康事件,定义了5个二分类的类别健康性状(观测值为0或1)。利用单性状和二性状重复力动物模型估计了新定义的23个健康性状的遗传参数。【结果】健康性状的遗传力在0(瘤胃酸中毒)至0.03(产乳热)之间。5个类别健康性状中,乳房健康类、繁殖障碍类和代谢障碍类为遗传力最高的3个性状,遗传力均在0.02左右,而消化障碍类(0.01)和肢蹄健康类(0.007)的遗传力相对较低。其中,繁殖障碍和消化障碍中,考虑整体抗性的类别健康性状的遗传力高于其对应类别内的任一单一性状,而乳房健康、代谢障碍和肢蹄健康类别性状的遗传力均分别低于类别内遗传力最高的单一性状。不同类别的健康性状之间,存在较低的遗传相关;同类别健康性状之间,存在一定程度的遗传相关。其中,肢蹄健康类各健康性状间的遗传相关最高,为0.63(蹄叶炎与腐蹄)—0.99(蹄叶炎与蹄底溃疡);繁殖障碍中,胎衣不下分别与子宫炎(0.47)、子宫内膜炎(0.46)存在中等遗传相关;消化障碍中,腹泻与肠炎(0.94)、消化不良与前胃迟缓(0.80)分别存在较高的遗传相关;代谢障碍中,酮病与胎衣不下(0.42)存在中低遗传相关。【结论】基于当前我国奶牛群体健康事件的数据记录质量以及本研究的分析结果,本研究建议将5个单一健康性状(临床乳房炎、子宫炎、酮病、真胃变位及产乳热)和2个类别健康性状(消化障碍及肢蹄健康)作为我国奶牛群体健康性状研究和选育中重点关注的目标性状。本研究探究了基于牧场管理数据定义奶牛健康性状的可行性,利用我国牛群数据对健康性状进行了系统的遗传分析,为我国奶牛疾病抗性的选育和研究提供了参考信息,有助于我国奶牛群体的平衡育种。

【Objective】This study was conducted to define health traits and to estimate their genetic parameters by using on-farm management data in dairy cattle.【Method】In this study, the health event records were collected by extracting from farm management software from 46 large-scale dairy farms in Northern China. Totally, 1 326 kinds of health events were grouped into five categories by standardizing the acronyms of on-farm records, 18 kinds of most frequent health events were selected from five categories. According to whether a health event occurred at least once within a lactation, 18 binary individual health traits corresponding to the 18 selected health events were defined(observations being 0 or 1). Furthermore, in order to define cow’s general resistance to certain type of health problem, five binary general health traits were defined according to whether health problems within a health category occurs at least once in a lactation(observations being 0 or 1). The single trait and two traits linear animal models were used to estimate the genetic parameters for 23 newly defined health traits. 【Result】The estimated heritabilities for 23 health traits ranged from 0(rumen acidosis) to 0.03(milk fever). Udder health, reproductive disorders and metabolic disorders had the highest heritability(approximately 0.02) among five general health traits, whereas digestive disorders and hoof health had relatively low heritability(less than 0.01). Clustering health events into categories resulted in higher heritability for reproductive disorders and digestive disorders, while heritabilities of udder health, metabolic disorders and hoof health were lower than that of single health traits with the highest heritability in their respective category. The low genetic correlations between different health category traits were found;however, the moderate genetic correlations among some health traits from same category were observed. The health traits within the hoof health had the high genetic correlations with each other, ranged from 0.63(Laminitis and Footrot) to 0.99(Laminitis and Sole ulcer). For reproductive disorders, retained placenta had medium genetic correlations with metritis(0.47) and endometritis(0.46), respectively. For digestive disorders, relatively high genetic correlations were found between diarrhea and enteritis(0.94) as well as dyspepsia and antony of forestomachs(0.80). The ketosis and abomasum displacement had a genetic correlation of 0.42.【Conclusion】Based on the current data quality of health records in Chinese dairy farm and the results from the current study, it was suggested that five individual health traits(clinical mastitis, metritis, ketosis, abomasum displacement and milk fever) and two general health traits(digestive disorders and hoof health) could be considered as target traits, and they should be intensively considered in research and breeding practice for improving health traits genetically in Chinese Holstein population. This study proved the feasibility of defining health traits using on-farm management data in Chinese dairy cattle. The results from the current study provided a reference for research and genetic selection of disease resistance in dairy cattle, and could help to promote balanced breeding in Chinese dairy cattle population.