Relationship between body condition scores and ultrasound measurements of subcutaneous fat and m. longissimus dorsi in dairy cows differing in size and type

Abstract

AbstractIn the present study body condition scores (BCS), ultrasound fat thickness and ultrasound m. longissimus dorsi thickness as well as body measurements and management factors were recorded repeatedly during lactation in 71 Holstein-Friesians, 71 Jerseys and 71 Holstein-Jersey F1-crosses (first to ninth lactation) on four feeding regimens. BCS were analysed with ultrasound measurements as explanatory variables by mixed models. A compound symmetry structure for the variance components was applied. The models were also tested for an autoregressive error structure [AR(1)]. Ultrasound fat thickness and ultrasound m. longissimus dorsi thickness explained most of the variability in BCS. Coefficients of determination were between 0•84 and 0•85. Management factors such as feeding group and stage of lactation (week of taking measurements) and the breed type ✕ lactation interaction were, although significant, not relevant for the fit. Holsteins tended to have lower scores than F1-crosses and Jerseys and younger cows tended to have higher scores than older cows. Despite small differences between breeds, Edmonson’s BCS proved to be consistent within each breed type; thus BCS can be applied to various dairy breeds.