Effects of supplements on intake, growth and bacterial protein synthesis in cattle eating NaOH treated straw.

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