Abstract:
Animal Production in Australia 1998 Vol. 22 THE EFFECTS OF ALKALIS AND OXIDANTS ON THE NUTRITIVE VALUE AND IN SACCO DISAPPEARANCE OF RHODES GRASS HAY (Chloris gayana cv. Callide) B.C. GRANZINAB, G. McL. DRYDENA and A.S. CHAUDHRYA A B Dept of Animal Production, The University of Queensland Gatton, Qld 4345 Present address: NSW Agriculture, Wollongbar Agricultural Institute, Wollongbar, NSW 2477 Limited information exists on the effects of alkalis and oxidants on the nutritive value of tropical grasses. With the exception of the observations by Dixon and Escobar (1984) and Brown et al. (1987), amounts of alkalis and oxidants applied to tropical grasses have been based on recommendations for temperate forages. Given the diversity in cell wall structure, tissue types and concentrations of lignin and non-core lignin between temperate and tropical forages, treating tropical forages with these recommended levels of alkalis and oxidants may not necessarily give optimum improvements in intake and digestibility. In a completely randomised experiment replicated three times, three alkalis (NaOH, Ca(OH) 2, and CaO) and two oxidants (NaOCl and H2O2) were added to 500 g of Rhodes grass hay (Chloris gayana cv. Callide) in opaque, plastic bags at rates of 0, 20, 40, 60 and 80 g/kg DM. Water (250g/sample) was also added. After mixing, the samples were stored at 22oC for 28 days. Increasing additions of NaOH, Ca(OH)2 and CaO significantly reduced neutral detergent fibre (NDF) content and improved 48 hour in sacco disappearance of organic matter (Table 1). While NaOCl had a significant effect on NDF content, it had no effect on in sacco disappearance, and H2O2 had no effect on either variable. Of the chemicals used, NaOH had the greatest effect on nutritive value. When applied at 80 g/kg DM, NaOH reduced concentrations of NDF from 681 to 553g/kg DM and acid detergent fibre from 363 to 335 g/kg DM. Forty-eight hour in sacco disappearance of organic matter increased from 682 to 874 g/kg DM. Financial assistance from the Australian Research Council is acknowledged. Table 1. Effect of alkali or oxidant treatments on Rhodes grass hay; regressions of neutral detergent fibre concentrations (Y) or 48 hour in sacco disappearance of organic matter (Y) on level of treatment (X; g/kg DM) Treatment Neutral detergent fibre NaOH Ca(OH) 2 CaO NaOCl HO 48 hour in sacco disappearance of organic matter NaOH Ca(OH) 2 CaO NaOCl HO a 2 2 2 2 Regression Y= Y= Y= Y= not Y= Y= Y= not not 697 - 1.66 669 - 0.69 713 - 1.60 671 - 0.68 significant X X X X P 0.0001 0.0004 0.0001 0.0035 0.9242 0.0001 0.0001 0.0001 0.4757 0.7820 R 2 s.e. a 0.92 0.81 0.92 0.53 15.8 18.9 13.9 19.1 629 + 2.38 X 686 + 1.08 X 685 + 1.24 X significant significant 0.94 0.79 0.88 18.8 15.5 13.6 Residual standard error of regression BROWN, W.F., PHILLIPS, J.D. and JONES, D.B. (1987). J. Anim. Sci. 64, 1205-1214. DIXON, R.M. and ESCOBAR, A. (1984). Trop. Anim. Prod. 9, 53-61. 386
