Abstract:
PI-oc. Amt. Sot. Arlirn. Prod. 1994 Vol. 20 GROWTH OF WEANER CALVES FED MOLASSES BASED DIETS R.M. DIXON and D.R. SMITH Swans Lagoon Research Station, QDPI, Millaroo, Ayr, Qld. 4807 Early weanin g of calves is used in the northern beef industry to reduce nutritional stress and increase calving rates, but involves high feed costs (Fordyce and Entwistle 1992). Most previous work has suggested that diets for very youn, calves should be based on grain rather than molasses to obtain 0 satisfactory growth rates (Moss 1993). The present experiment examined growth rates with diets based on hay, molasses and cottonseed meal (CSM) and examined the effects of restricting hay intake. Sixty Bos indicus crossbred calves (34 heifers and 26 bulls, liveweight (LW) mean 103 kg, SD 8.5 kg, range 84-114 kg) were weaned in August 1993. Following a 2 week adaptation phase the calves were moved to pens (3 calves in each of 20 pens) and allocated to 1 of 5 diets. Calves allocated to Treatments l-4 were fed a molasses/urea/CSM mixture ad Zibitum and 0.5 kg CSM/day. In addition Treatment 1 (Tl) calves were fed hay ad Zibitum, Treatment 2 (T2) calves 0.66 kg hay/day, Treatment 3 (T3) calves 0.33 kg hay/day and Treatment 4 (T4) calves 0.25 kg coarsely cracked sorghum grain and 0.66 kg hay/day. The molasses/urea/CSM mixture consisted of 100 kg molasses, 10 kg CSM, 3 kg urea, 1 kg salt, 1 kg dicalcium phosphate and 0.25 kg Rumensin Homemix (20 g monensin/kg). Treatment 5 (T5) calves were fed a concentrate mixture and hay, both ad Zibitum. The concentrate mixture contained 62% coarsely cracked sorghum, 25.5% CSM, 3.3% limestone, 3.0% sodium bentonite, 2.5% dicalcium phosphate, 1% urea, 1% molasses, 1% Rumensin Homemix, 0.1% elemental sulphur and 0.15% mineral premix. Chopped hay was of medium to good quality and consisted of a mixture (2:l) of Brachiara humidicola and wheat cut at the flower stage. Intake and calf LW were measured weeklv for 8 weeks. Table 1. Intake of dry matter (kg/day), liveweight (LW) gain (kg/day) and feed conversion (kg feed/kg LW gain) of calves fed 5 different diets (Tl-T5) Mean LW gain of the calves was at least 0.6 kg/day for each of the diets, and even the smaller calves in the experiment performed well. Restricting the amount of hay reduced LW gain but in some 0 circumstances may still be the more economical feedin, sy stem. Addition of some sorghum grain to the molasses/urea had no discernible effect. The low intake of concentrate mixture based on sorghum grain and CSM (T5) was associated with a high dietary concentration of monensin provided as Rumensin. The low growth rates observed in some previous experiments using molasses based diets may well have been due to a shortage of undegraded dietary protein. The experiment demonstrated that high growth rates can be achieved when early weaned calves are fed diets based on molasses, hay and CSM. FORDYCE, G and ENTWISTLE, K. W. (1992). Proc. Aust. Sot. Arzim. Prod. 19: 55-6. MOSS, R. J. (1993). Trap. Grassl. 27: 238-49. 345