Effect on Early Lactation of Feeding a Milk Fat—Depressing Ration Prepartum

Abstract

Cows fed a milk fat—depressing ration for five to seven weeks before parturition and continued on this feed after calving exhibited a steadily declining milk fat content for the first six to eight weeks of lactation, at which time the fat tests were substantially below controls on conventional rations. These changes appeared to parallel changes in the ratio of acetate to propionate in rumen fluid. The milk fat tests were significantly (P < .05) lower in a group of cows each of which was either fed supplementary vitamin B12 or treated with cobalt. This may have been due to the increased feed consumption observed in this group. The pattern of changes in the fatty acid composition of the milk fat accompanying reduction in milk fat synthesis during early lactation was in marked contrast with that observed in other cows, on the same feed, later in lactation. © 1969, American Dairy Science Association. All rights reserved.