Relationships of body weight and carcass quality traits with first lactation milk production in Finnish Ayrshire cows

Abstract

Relationships of body weight and carcass quality traits with first lactation milk production traits were estimated from a field data set of 28 362 Finnish Ayrshire cows, using REML methodology and animal model. Studied body weight traits included heifer and mature live weight, estimated based on heart girth circumference as part of normal milk recording system, and carcass weight recorded in the slaughterhouse. Additional carcass quality measures included carcass fleshiness and fatness as recorded in the slaughterhouse. Milk production traits included first lactation 305-d milk, fat and protein yield, and fat and protein percentage. Genetic correlations between carcass weight and yield traits were almost zero, while the genetic correlations between live weight and yield traits were of somewhat higher magnitude. This suggests a negative correlation between yield traits and killing out percentage, which might be caused by a difference in the digestive tract weight and feed intake capacity. The genetic correlations between carcass quality and yield traits were negative and low to moderate. Selection for high yield alone seems thus to lead into reduction in body condition, which in turn might lead into more negative energy balance especially in early lactation.