Nutritionally directed compensatory growth and effects on lactation potential of developing heifers

Our objective was to determine the extent to which a stair-step compensatory nutrition regimen regulated the growth and subsequent lactation performance of developing beef heifers. Forty crossbred beef (Angus x Gelbvieh) heifer calves were assigned to either a control or stair-step compensatory nutrition regimen. Heifers fed the stair-step compensatory nutrition regimen were fed according to an alternating schedule beginning with a high energy diet (130% of the metabolizable energy recommended by the National Research Council) for 2 mo, followed by an energy restricted diet (70% of the recommended metabolizable energy) for 3 mo, and concluding with the high energy diet again for 2 mo. Thereafter, all heifers received the control diet. The average daily gain of heifers fed the stair-step compensatory nutrition regimen was 2-fold higher than that of control heifers during the final high energy phase. The RNA and protein contents in the mammary tissues of heifers fed the experimental regimen in early lactation were greater than those of control heifers. Lipid content was significantly reduced in the mammary tissues of heifers fed the experimental regimen. The expression of beta-casein in the mammary tissues of heifers fed the experimental regimen was higher than that of the control heifers. Heifers fed the stair-step regimen yielded 6% more milk than did those fed the control regimen. Total protein and casein in milk of heifers fed the experimental regimen were higher than those in milk of control heifers. These results indicate that the stair-step compensatory nutrition regimen enhanced mammary development and subsequent lactation performance.