Relationship between water intake, dry matter intake and daily milk yield on a German research farm

Abstract

The aim of the present study was to investigate the relationship between milk yield, water and dry matter intake and to clarify whether these relationships remained constant over the stages of lactation. Data recording was performed on the dairy research farm Futterkamp of the Chamber of Agriculture Schleswig-Holstein. A dataset of about 39,000 observations from 225 Holstein cows was used. Average milk yield, water and dry matter intakes were 34.9, 84.3 and 20.3 kg, respectively. Estimations of variance components were accomplished by applying linear mixed Fixed Regression (FR) and Random Regression (RR) models. Repeatabilities with the FR Model were assessed at 0.76 for milk yield, 0.41 and 0.34 for water and dry matter intakes and after applying the RR Model they changed during the lactation to 0.79–0.92, 0.46–0.52 and 0.43–0.50, respectively. Correlations with the FR Model between milk yield and water and dry matter intakes and between water and dry matter intakes were 0.73, 0.59 and 0.73, respectively, and after applying the RR Model they ranged in the course of lactation between 0.13 and 0.84, 0.48 and 0.93, and 0.76 and 0.82, respectively. Hence, variance components of these traits differed during lactation. Thus the use of RR models must be emphasised to analyse these traits.