Changes in milk yield and composition at oestrus in dairy cows

Abstract

SUMMARYA New Zealand dairy herd of 73 cows was observed at pasture during the breeding season. Individual cow milk yields and composition analyses were obtained before, during and after oestrus. There was an overall reduction in yield at the first, and a rebound enhancement at the second milking after onset of oestrus. Changes in fat content followed the same time course and there was a slight increase in lactose content. Protein and somatic cell content were unaffected. There were considerable individual differences in both the duration and intensity of oestrous behaviour on the one hand, and the extent and timing of the effects on milk production on the other. However no relationship was found between the degree of behavioural excitement shown by a cow in oestrus and its change in milk production.