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

This study was conducted to define health traits and to estimate their genetic parameters by using on-farm management data in dairy cattle.

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.

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.

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.