Abstract:
Animal Production in Australia Vol. 15 EFFECTS OF SUPPLEMENTS ON INTAKE, GROWTH AND BACTERIAL PROTEIN SYNTHESIS IN CATTLE EATING NaOH-TREATED STRAW J.C. SPRAGG*, R.C. KELLAWAY* and JANE LEIBHOLZ* In a comparison of supplements fed to cattle eating NaOH-treated straw, liveweight gain and straw intake were similar when heifers were fed cotton-seed meal (C) or cracked barley (Spragg et al. 1982). This paper summarizes responses in two subsequent experiments in which effects of C and rolled barley (B) supplements on intake, growth rate and digesta flows were measured in cattle eating NaOH-treated straw. Oat straw was sprayed with NaOH solution (44 g NaOH in 113 g HzO/kg) followed by a mineral solution supplying (g/kg) 79 H20, 14 N, 1 S, 1.5 P and (mg/kg) 4 Cu, 0.1 Co and sprinkled with hydrated lime supplying (g/kg) 2 Ca. The treated straw was fed ad lib. to heifers receiving no supplement (0) or supplemented with 700 g/d of B or C. These diets were fed in Expt 1 to 33 Friesian heifers (210 kg live weight) and in Expt 2 to six Hereford heifers (200 kg live weightj fitted with rumen and abomasal cannulas. TABLE 1 Dry matter intake (DMI) of treated straw, liveweight gain (LWG), nitrogen leaving stomach (N flow) and bacterial N synthesized/kg organic matter apparently digested in stomach (BactN/OMAD) in heifers fed supplements with a basal diet of NaOH-treated oat straw No significant differences in straw intake were recorded in either experiment. Heifers on treatment C had significantly higher liveweight gains than those on treatment B which were significantly greater than those on treatment 0 (P < 0.05). Similarly, N leaving the stomach and efficiency of microbial protein synthesis were significantly greater for heifers on treatment C than on treatments 0 and B. The greater quantity of N leaving the stomach on treatment C was attributed half to the greater efficiency of microbial protein synthesis and half to undegraded dietary protein. As metabolizable energy intakes would have been similar on treatments B and C, the higher liveweight gain of animals on treatment C may be attributable to a higher proportion of nutrients absorbed as amino acids. SPRAGG, J.C., KELLAWAY, R.C. and KEMPTON, T.J. Prod. Z 679. 14: (1982). Proc. Aust. Soc. Anim. *Dept of Animal Husbandry, University of Sydney, Camden, N.S.W. 2570. 750