Abstract:
Proc, Aust. Soc, Anim. Prod, Vol. 18 GROWTH RESPONSES OF B RAHMAN-CROSS STEERS ADMINISTERED WITH MONENSIN ALONE, OR IN COMBINATION WITH OESTRADIOL 17B R.J. THOMPSON* The rumen modifier, and/or protein meal the literature which from rumen modifiers monensin, has been fed to cattle in mixes of molasses, urea during the dry season. Standfast et al. (1989) reviewed showed a wide variation of growth responses (O-170 g/hd/d) when used in this manner. When steers are actively growing in the wet season, anabolic growth promotants have been shown to improve liveweight (LW) gains by lo-15% (Hodge et al. 1986). Little information is available on the growth responses to rumen modifiers and rumen modifier/anabolic combinations used during the wet season in the absence The experiement being reported, investigated growth responses of supplements. of steers to either oestradiol 17B or monensin alone and in combination. One hundred, forty-eight month old steers were randomly allocated to one of four treatments vie: Control; oestradiol 17B (Compudose 200); monensin sodium 32 g ('Anti-Bloat Capsule') (TM Elanco Products Company); oestradiol plus monensin. All treatment groups grazed the same.paddock of Callide Rhodes grass Live weights were monitored at six week intervals over a 130 (Chloris gayana). Statistical analysis of treatment means (Table 1) was by a 2 x 2 day period. factorial with initial live weight as a co-variate. Table 1 Liveweight gains of steers treated with Monensin and Cestradiol l7B alone and in combination over a 130 day period Means with different superscripts differ significantly (P<O.OS) Implantation of oestradiol 17B improved growth rate either alone or with monensin. However, there was no improvement in growth attributable to monensin alone and there was no synergistic response when it was used with oestradiol Standfast (1989) states that responses to rumen modifiers have been poor 17B. in cattle grazing native pastures without supplements. The results achieved in this experiment show similar results. HODGE, P-B., PLASTO, A-W., ROUND, P-J., SMITH, P.C., AUBREY, J.N. and MULDER, J-C. (1986). Proc, Aust, Soc. Anim. Prod, 16:235. STANDFAST, N-F., GULBRANSON, B. and TYLER R., (1989). 'South-East Queensland Beef Technology Forum - Rumen Modifers - An Update' Circulated Trial Report 89/l Beef Cattle Husbandry Branch, (Qld. Dept. Prim. Ind.: Brisbane). * Beef CMtle Husbandry Branch, Q.D.P.I. Ayr, Qld. 4807. 561
