Association of -Casein Glycosylation with Milk Production and Composition in Holsteins

¹ Department of Animal Science, Macdonald College of McGill University, Ste. Anne de Bellevue, PQ, Canada H9X 1C0

A total of 545 milk samples were collected from 53 Holstein cows for 1 yr. On test day, morning milk yields were recorded; milk samples were analyzed for N-acetylneuraminic acid, protein, fat, casein, -casein, and SCC. The relationship between the degree of glycosylation of -casein and morning milk yield and composition was investigated. Data were analyzed using least squares procedures with a model that included test day, parity, stage of lactation, SCC, and phenotype for -casein as fixed effects and N-acetylneuraminic acid content of -casein as covariate. After adjustments were made for effects of environmental and genetic factors, the degree of glycosylation of -casein was associated with morning milk yield, protein, and casein content. Milk yield increased linearly with an increase of N-acetylneuraminic content up to approximately 70 µg/mg of -casein.

Key Words: -casein glycosylation • milk yield • milk composition

Submitted on February 4, 1991
Accepted on June 3, 1991