The liveweight gain response of cattle grazing Setaria sphacelata pastures when supplemented with formaldehyde treated casein

Abstract

Proc. Amt. Sot. ArCn. Prod. I994 Vol. 20 THE LIVEWEIGHT GAIN RESPONSE OF CATTLE GRAZING SETARIA SPHACELATA PASTURES WHEN SUPPLEMENTED WITH FORMALDEHYDE TREATED CASEIN T. MBONGOA, D.P. POPPIA and W.H. WINTERB of Agriculture, The University of Queensland, Old. 4072 0 Division of Tropical Crops and Pastures, St. Lucia, Qld. 4067 There is a need to improve the annual liveweight gain of cattle in the tropics, and one strategy is to increase wet season liveweight gain by supplementing with protein. Stobbs et al. (1977) showed that milk production in cows grazing Chloris gayana pastures could be increased by as much as 20% by protein supplementation. In this experiment, the liveweight gain response of steers grazing Setaria sphacelata (Setaria) pasture in summer and autumn and supplemented with formaldehyde treated casein (F-casein) was measured. Sixteen Belmont Red steers with an average liveweight (LW) of 272 2 5.0 kg were allocated to 4 treatment groups as follows: control (no F-casein), and 0.6 g, 1 .O g and 1.9 g F-casein/kg LW.day for low, medium and high protein supplement respectively. All animals received 300 g of sugar/day. The casein was treated at the rate of 1% of formaldehyde using the method of Stobbs et al. (1977). The disappearance of casein from nylon bags incubated in the rumen of a steer on a similar basal diet was approximately 5% for the F-casein and 99.5% for the untreated casein after 24 hours. The animals grazed fresh Setaria pasture for 14 weeks between January and May 1992 and the supplement was fed daily in individual stalls. The quality of the diet selected by 4 oesophageal fistulated animals on 1 occasion and of samples plucked at 2 week intervals was 13% crude protein (CP), 67.6% neutral detergent fibre (NDF), 90.6% organic matter (OM) and 13.7% CP, 59.7% NDF, 88.4% OM respectively. Intake was calculated with reference to faecal output (chromic oxide capsules) and in vitro digestibility of extrusa (49.5% + 2.23). Liveweight was monitored weekly. The low and medium levels of F-casein significantly increased liveweight gain by 29% and 19% respectively (Table 1). There was no response obtained from the high level of supplementation possibly as a consequence of catabolising excess protein. Faecal nitrogen concentration increased with increasing protein supplementation, but there was no significant difference between the low and medium treatments. Forage intake was not affected by the treatments. Table 1. F-casein supplementation on liveweight gain, DM intake and faecal nitrogen in steers grazing Setaria The liveweight gain response to extra protein by these animals is an indication that the protein in Setaria pasture is not sufficient to support maximum growth in young steers. It can therefore be concluded that steers grazing tropical grass do require extra intestinal protein in order to maximise their Growth rates and the values derived here can be used as a target for commercial supplements. a STOBBS, T.H., MINSON, D.J. and MACLEOD, M.N. (1977). J. Agric. Sci., Camb. 89: 137-41. 342