The fundamentals of efficiency for production and metabolic stress in lactating dairy cows involve the interplay of energy expenditure and energy sources during lactation. Both milk yield and dietary intake, their amounts and compositions, can be recorded readily, at least on experimental farms, but body reserves of a living lactating cow cannot be measured. Body reserves is also a function of amount, or weight, and composition, or condition. Weight can be measured, but condition can be only approximated. Body condition score (BCS) is used to approximate the body condition of a dairy cow, with its crudeness unknown because of its subjectivity. It reflects largely adipose tissue stores and not protein reserves, but this is only speculation. Ultrasound measure of muscle (UTM) and backfat (UTBF) may be more objective measures, but indicators of exact what aspects of body reserves remain unknown. We in Denmark are in the process of attempting to profile body energy state of a lactating cow using repeated measures of several body condition related variables such as BCS, UTM and UTBF, and laboratory results of biochemical parameters from liver biopsy and blood samples in a data set from an experimental farm. This paper presents the changes in BCS, UTM and UTBF and their phenotypic and genetic variations during lactation.

I. L Mao, K. Sloniewski, P. Madsen, J. Jensen, N. C Friggens

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.31, 2002
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