Physiological and environmental effects on milk yield in milking crossbred cows of the production system at the CNPGL/Embrapa

Abstract

This study was conducted with the data from crossbred Holstein-Zebu-Gir (H-Z) cows in the Production System which was introduced in 1977 at the National Centre of Research on Dairy Cattle (CNPGL/EMBRAPA), Coronel Pacheco, Minas Gerais State, Brazil. The effects of physiological and environmental factors on the milk production were studied. Milk yields from 395 lactation averaged 2,989±80 kg. Milk yield was affected by systems, year of parturition (lactations starting from June to August were higher than those from December to February), genetic groups (within the System they were all equivalent in production but prior to the System the 3/4 H-Z produced more milk than the 1/2 H-Z bred), and finally the calving order which reached maximum yield during the 5^th lactation. The interaction System x calving season was also observed.