Abstract:
The effect of rumen escape protein on carcass characteristics of rapidly growing prepubertal dairy heifers R. Dobos , K. Riley , K. Nandra , R. Kellaway , W. Fulkerson and I. Lean `NSW Agriculture Elizabeth Macarthur Agricultural Institute, Camden NSW 2570 2Department of Akmal Science, University of Sydney, Camden NSW 2570 3NSW Agriculture 9 Wollongbar Agricultural Institute, Wollongbar NSW 2477 1 1 1 2 3 2 Dairy heifers grown rapidly during the prepubertal period, 4 to 12 months of age, have an increased amount of fat deposited in their mammary glands (Valentine et al. 1987). An experiment investigated the use of rations high in rumen escape protein to alleviate the problem of increased fat deposition in the mammary gland associated with rapid prepubertal growth rates. This paper reports on the carcass characteristics fkom that experiment. Three groups of 21 randomly selected Friesian heifers were fed isoenergetic (11 MJ ME) rations as follows: l period, heifers were run as one group and offered pasture, silage, lucerne hay and diet B pellets. Six heifers per group were slaughtered when they were between the 10th and 18th day of their oestrus cycle. Table 1 summarises the carcass characteristics of the slaughtered heifers. The lower fat content of heifers rapidly grown on diet C needs to be economically evaluated if consideration of this strategy is to be utilised for meat and milk production. Also, the implications on future reproduction of these heifers has to be considered. Diet A contained 14% CP with 15% rumen escape protein (REP); Diet B contained 18% CP with 15% REP; and Diet C contained 18% CP with 30% REP. References Valentine, SC., Dobos, R.C., Lewis, P.A., Bartsch, B.D. and Wickes, RB (1987). Effect of liveweight gain before or during pregnancy on mammary development and subsequent milk production of Australian Holstein-Friesian heifers. Australian Journal of Experimental Agriculture 27,195204. l l All heifers were offered the diets ad libitum in a feedlot from 4 to 10 months of age. Mer the experimental feeding Table 1 Mean (* se) growth rates and carcass characteristics of prepubertal dairy heifers fed the 3 diets. Recent Advances in Animal Nuttition in Australia 1997 University of New England, Annidale NSW 2351, Australia