Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 19 EFFECT OF DIET ON FAT DEPOSITION IN CATTLE G.D. TUDOR Qld Dept of Primary Industries, Animal Research Institute, Yeerongpilly, Qld 4 105. Present address: W.A. Dept of Agriculture, PO. Box 1231, Bunbury, W.A. 6230. Cattle fed on high grain diets may deposit more fat than pasture-finished cattle but it is unclear whether this is a result of the generally faster growth or diet per se. This experiment investigated the effect of high grain or pasture on fat development in cattle by controlling liveweight gain. Twenty-four, 12-15 month old Hereford steers were randomly allocated to 3 treatments each with 8 animals. Animals in treatments 1 and 2 were group-fed (4/yard) on predominantly barley (Barley) or sorghum (Sorghum) grain diets (- 3% N), while animals in treatment 3 grazed on high quality gramineous crops or pasture (- 3% N). The grain-fed groups started 1 week after the grazing group (Pasture) and growth rate was regulated by adjusting feeding level of the grain groups. The grain diets comprised 80% concentrate (including minerals, urea) and 20% chaff (2.4% N). Individual daily gains were calculated from the regression relating individual LW to time. Initial carcass weights were estimated using the equation which was derived from 11 cattle slaughtered at the start of the experiment: where y = hot carcass weight (HCW) and x = fasted LW (24 h off feed, 16 h without water). The daily gain data were subjected to analysis of variance and the carcass composition data (Table 1) were analysed by covariance to allow for variation in final weight. Table 1. Growth and carcass composition of treatment steers Means within rows with different letters are significantly different (PcO.05) Daily LW gain, carcass gain and final LW did not differ significantly although the barley-fed cattle had significantly (P<O.O5) lighter carcasses. Grain-fed cattle deposited significantly (PcO.05) more fat than the cattle finished on pasture with a corresponding reduction in water, protein and ash. The availability of starch post-ruminally (Tudor 1992) and the absorption as glucose from the small intestine (Janes et al. 1985) could be associated with the increased fat deposition in the grain-fed cattle. JANES, A. N., WEEKES, T. E. C. and ARMSTRONG, D. G.( 1985). Br. J. A&l: 54: TUDOR, G. D. (1992). Ph.D. Thesis, University of Adelaide.