Body condition score and dairy form as indicators of dairy cattle disease and reproductive performance

by Dechow, Chad.

The objectives of this research were to estimate heritabilities and correlations between body condition score (BCS) from various sources, determine the genetic relationship among BCS, dairy form, cow health and reproductive performance and investigate various models to analyze BCS and dairy form. BCS was obtained from herds using PCDART dairy management software and from linear type appraisals by Holstein classifiers. Cow health data was obtained from several herds recording disease treatments. Genetic evaluations for cow health in Denmark were also obtained. Reproductive data and yield data were provided by DRMS and AIPL-USDA. Heritabilities and correlations among traits were estimated with REML using animal and sire models. Random regression and repeatability sire models were compared. Fixed effects for all models included contemporary group effects, age, and days in milk (DIM) when available. Random effects were sire or animal and error. The heritability estimate of BCS from linear type appraisal was 0.22. The genetic correlation estimate between BCS from PCDART records and linear type appraisals was 0.87, between BCS and dairy form was –0.72 and between BCS and strength was 0.69. The genetic correlation estimates from random regression models between DIM 0 in lactation 1 and DIM 305 in lactation 3 were estimated to be 0.77 for BCS and 0.60 for dairy form. Higher BCS and lower dairy form were significantly correlated with lower milk yield, less metabolic disease and fewer days open. The relationship among BCS, dairy form, cow health and reproductive disease remained significant after adjustment for milk yield. The relationship between BCS and cow health and reproductive performance tended to be non-significant after adjustment for dairy form. Supplementing direct genetic evaluations for days open with evaluations for dairy form increased reliability of days open by an average of 0.06 for 19 recently proven bulls. Selection for lower dairy form or higher BCS will slow the deterioration of cow health and reproductive performance that accompanies selection for increased yield. iv