COMPENSATORY GROWTH IN DAIRY HEIFERS - THE EFFECT OF A COMPENSATORY GROWTH-PATTERN ON GROWTH-RATE AND LACTATION PERFORMANCE

The objective of this study was to improve the efficiency of growth an d lactation performance of dairy heifers fed for a stair-step growth p attern. Twenty-four young Holstein heifers were randomly assigned to e ither control or test groups. The test group was fed according to a sc hedule of 3, 2, 4, 2, 5 and 2 mo in which feed intake was alternately 20% below or 25% above requirements. Heifers that were subjected to th e stair-step growth pattern gained more body weight and consumed less dry matter, resulting in improved efficiency of growth compared with t hat of controls (7.8% vs. 8.3%). First estrus, first conception, gesta tion period, services per conception, and calving difficulty (dystocia ) were not affected by stair-step growth. Concentration of growth horm one in blood serum was elevated during feed restriction for the test h eifers; however, during refeeding, growth hormone was decreased compar ed with that in the blood serum of control heifers. Mammary tissues ob tained by biopsy from heifers in middle and late pregnancy were used f or chemical composition analysis. Stair-step growth increased DNA, RNA , protein, the ratio of RNA to DNA, and the ratio of protein to DNA. L ipid decreased in the mammary tissue of test heifers in late pregnancy (9.5 mo). Heifers in the test group yielded approximately 9% more mil k than did heifers in the control group. These results indicate that c ompensatory growth can contribute to the improvement of growth efficie ncy and lactation performance.