Abstract:
.AnimaI Production in Australia EFFECT OF MAIZE AND COTTONSEED MEAL SUPPLEMENTATION ON GROWTH OF DAIRY WEANERS GRAZING IRRIGATED TROPICAL GRASS PASTURES ** R.J. MOSS* , I.K. GOODCHILD* , A.C. BIRD* and R.M. MURRAY Low intake of digestible nutrients can limit animal production from tropical pastures. Growth rates of dairy replacements can be increased with concentrate supplementation though growth of early weaned calves may be low unless a protein concentrate is included (Byford et al. 1978). This experiment examined the effect of levels of grain and protein supplements to tropical pastures on growth of dairy weaners. Fifty-two Australian Friesian Sahiwal (AFS) calves were weaned at 70 kg live weight onto irrigated nitrogen fertilized (730 kg urea/ha/annum) couch (Cynodon dactylon) - pangola (Digitaria decumbens) pastures at Ayr Research Station, North Qld. Calves were offered maize (M) (9.1% crude protein - CP) or a mix of 5 maize (M) : 1 cottonseed meal (CSM) (14.3% CP) at 1.0 or 1.5 kg/head/day in a 2x2 factorial experiment. Animals left the experiment when they exceeded 130 kg. Increased level of supplementation as M did not increase liveweight gains. Inclusion of CSM in the isocaloric supplements increased liveweight gains and this response was greater with 1.5 kg of supplement (P (0.01) (Table 1). TABLE 1 Effect of maize or maize plus cottonseed meal on growth of AFS weaners Means in columns with different superscripts are significantly different (P<O,O5) Gains of maize supplemented calves exceeded results obtained for Friesians in other experiments in North Qld (Byford et al. 1978; Moss et al. 1978). Growth rates we obtained may be near the maximum obtainable for grain supplemented weaners grazing tropical pastures without additional protein. Addition of CSM to supplements increased liveweight gains and apparent efficiency of utilization of incremental energy. This response may be due to reduced substitution of supplement for pasture and/or an increased efficiency of utilization of energy in the total supplement. Oesophageally fistulated Friesian weaners may select a diet of 16% CP from irrigated nitrogen fertilized grass pasture (Moss unpublished data) and this is sufficient to allow growth rates up to 0.5 kg/day. If high levels of energy concentrates are used to increase liveweight gains, dietary protein intake will be inadequate for efficient utilization of the energy supplied. Where pasture intake is of lower quality then the point of protein limitation will . be reached more quickly. BYFORD.,I.J.R., CHAMBERS, G-A. and MOSS, R.J. (1978). Prod. 12: 227. ' MOSS, R.J., CHOPPING , G.D. and O'ROURKE, P.K. (1978). Prod. 12: 219 *D.P.I. Mutdapilly Research Station, M.S. 825, Ipswich, **Department of Tropical Veterinary SC. James Cook Uni., 623 Proc. Aust. Soc. Anim. Proc. Aust. Soc. Anim. Qld 4305. Townsville, Qld 4811.
