Abstract:
Proc. Aust. Soc. Anim. Prod. I996 Vol. 2 I EFFECT OF A SUPPLEMENTARY PROTEIN SOURCE ON MICROBIAL NITROGEN FLOW FROM THE RUMEN M.M. KOLADE and J.H. TERNOUTH Dept of Agriculture, The University of Queensland, St Lucia, Qld 4072 Rumen microbial turn-over and diet utilisation are greatly influenced by the intake and degradability of the carbohydrate and N components of the diet (Theurer 1986). This study investigated the adequacy of different protein sources to supply rumen degradable nitrogen for microbial protein synthesis. Fishmeal (FM), corn gluten (CG) and soybean meal (SBM) (protein sources of varying rumen degradabilities) were fed with either sorghum or wheat as six iso-nitrogenous (140g crude protein/kg DM) diets (34% chopped Pangola hay) to six Braford steers (206 k 5.9 kg liveweight) in a 2 x 3 factorial experiment (2 grain types and 3 sources of protein). The cattle were housed in metabolism crates, and after an 8 week period of transition and adjustment to the grain-based diets, were offered their respective diets ad libitum for periods of 2 weeks with total urine collection on the last 5 days of the second week. In a second and third period the steers were fed the same grain but different sources of protein, allowing 9 days between changing diets and sampling (Smith and McAllan 1970; Spicer et al. 1986). Urinary allantoin analysis was as described by Borchers (1977) and microbial-N flow was estimated from excretion of allantoin (Kolade et al. 1994). The results are presented as means for the grains as there was no interaction between grain type and protein source. Table 1. Intake of organic matter (OM) and nitrogen, rumen ammonia-N concentration, daily excretion of allantoin and the estimated microbial nitrogen (MN)' flow from the rumen of steers Intake of organic matter by cattle was similar for all protein sources. In spite of the significant differences (PcO.01) in ruminal degradability (in sacco) of protein sources (FM 0.30, CG 0.36 and SBM 0.69) and in ammonia concentrations in the rumen there were no differences in allantoin excretion and hence estimated microbial nitrogen flow. This indicates that microbial protein flow to the rumen is affected by factor(s) other than these protein sources when added to grain-based diets BORCHERS, R. (1977). Anal. Bioch. 79: 612-7. KOLADE , M.M., GUNN, K.J. and TERNOUTH J.H (1994). Proc. Amt. Sot. Anim. Prod. 20: 387. THEURER, C.B. (1986). J. Anim. Sci. 63: 1649-62. SMITH, R.H. and McALLAN, A.B. (1970). Br. J. Nutr. 24: 545-56. SPICER, L.A., THEURER, C.B., SOWE, J. and NOON, T.H. (1986). J. Anim. Sci. 64: 521-30. 447
