Milk Production Response to Shifting Cows Between Intraherd Groups

Abstract

Seven dairy herds, each divided into two or more groups of lactating cows, were studied for effects of shifting between groups on production. Herds averaged 140 cows and from 4858 to 7037kg milk. Treatments were shifting 2, 4, 6, 8, 10, 12, or 14% of milking cows between production groups within 1 wk after regular Dairy Herd Improvement test. Milk production, butterfat percent, days in milk, cow age, and body weight were obtained from test. Second test-day milk weights were normally recorded third and fourth milkings following cow shift.Multivariate analysis of 6731 cow observations showed differences in actual and percent changes in milk after shifting for herds, months, treatments, groups, group by treatment interaction, days in milk, and butterfat percent Milk decreased .53±3.11kg or 2.28% between test days. Cows shifted declined .99kg while those remaining in the high group declined .33kg. Initially production decreased most in those herds that began shifting at the start of this study. Decreased losses in subsequent months indicated possible adaptation.