LIPID ACCUMULATION IN YOUNG AND MATURE CULL HOLSTEIN COWS FED A HIGH ENERGY DIET

Abstract

Eleven young and eight mature lean Holstein cows were fed a high energy (high moisture corn and haylage) diet to appetite. In addition, six young and six mature cows were slaughtered at the start of the trial to estimate initial body composition. The cows were slaughtered at random over a period ranging from 68 to 103 days after start on feed. The left side of each carcass was broken into eight wholesale cuts that were further separated into bone, lean tissue and fat (subcutaneous and intermuscular). The lean and fat tissues from each meat cut were ground separately and analyzed for their moisture and lipid contents. Mature cows had significantly more lipid in the fat depots of three meat cuts (average increase of 84 g lipid/kg adipose tissue) than young cows at the start of the trial, but the overall effect of cow maturity on meat cut composition was minor. The feeding period, however, resulted in large significant increases in the lipid content of all meat cuts. Averaged over the eight meat cuts, the lipid contents of lean tissue, intermuscular and subcutaneous fat increased by 55.9%, 16.5% and 17.6%, respectively. There were no maturity differences in the rate of lipid accumulation indicating that young and mature cows had a similar pattern of lipid accumulation as they increased in size. Rate of lipid accumulation in subcutaneous fat was highest for the shank and rib and lowest for the flank and hip (growth coefficients were 1.54, 1.29, 0.68 and 0.68). Rate of lipid accumulation in the intermuscular fat was highest in the chuck and flank and lowest for the brisket, plate and hip (growth coefficients were 1.92, 1.85, 0.57, 0.59, and 0.64). Rate of lipid accumulation in lean tissue from all the meat cuts (intermuscular fat) was highest for the shank and brisket and lowest in the plate (growth coefficients were 1.37, 1.19 and 0.67). It was concluded that the lipid contents of lean and fat tissue from young and mature cull Holstein cows followed a pattern of differential accumulation, and that there was a major increase in lipid concentration in all fat tissue and lean from each of the meat cuts as fattening proceeded. Key words: Cows, chemical composition, carcass, lipid