Nutrient composition and in sacco digestibility of Chloris gayana (Rhodes grass) treated with alkalis and a microbial inoculum.

Abstract

Nutrient composition and in sacco digestibility of Chloris gayana (Rhodes grass) treated with alkalis and a microbial inoculum A.S. Chaudhry , R.T. Cowan , B.C. Granzin and A.V. Klieve 1 1 1 2 1 Department of Animal Production, University of Queensland, Gatton College, Lawes QLD 4345 2 Animal Research Institute, Queensland Department of Primary Industries, Yeerongpilly QLD 4105 Rhodes grass (RG) is high in dry matter (DM) yield but low in digestibility and therefore is under utilized by cattle in Queensland (Cowan et al. 1993). Its utilization may be increased by conservation and feeding back to cattle, particularly ifconservation is combined with alkali treatments or microbial inoculants (MI) (Kaiser et al. 1993). NaOH and CaO have improved nutritive value of cereal straws (Chaudhry, 1996; Chaudhry and Miller, 1996) and could be beneficial for RG We compared the use of CaO, NaOH, MI and NaOH plus MI (Na+MI) in treating RG before conservation as round bales. In April 1996, RG was harvested at regrowth of 100 days, wilted, analysed for DM and sprayed with either 30 litres (L) per bale of water alone (Control, C) or with12.5kgNaOH(Na)orwith51ofMI(MI).Halfofthe Na was re-sprayed with 5 L of MI (Na+MI) after 6 hours and baled. A foal treatment was sprayed with 5 L of water, dusted with 12.5 kg CaO and re-sprayed with 25 L of water (CaO) and baled. The bales were then wrapped with polyethylene for anaerobic storage in an open paddock. In October 1996, core samples were collected from all treatments and analysed for pH, DM, organic matter (OM), neutral detergent fibre (NDF), sodium, microbial counts (MC) and in sacco DM (DMD) and OM (OMD) digestibility in rutnen-fistulated cows for 48 h. The data were statistically analysed by using SAS. The presence or absence of NaOH (+/- Na) and MI (+/MI) was then compared Treatments differed significantly (Table 1) for DM, sodium and pH, OM and DMD and OMD. Treatment with NaOH caused a significant decrease in OM and NDF and an increase in OMD and DMD by 2 l-24%. In Table 1 contrast, MI did not change (P>O.O5) nutrient composition or improve in sacco digestibility of RG. Presence of microbial counts in Na+MI suggested that an alkaline pH was not toxic or inhibitory for the inoculant. CaO was not effective compared with NaOH. NaOH was the best amongst the treatments in preserving and increasing in sacco digestibility of Rhodes grass. The nutritive value of the grass was increased substantially despite the loss of over 50% of NaOH during spraying in the field Acknowledgments to DRDC for financial support. References Chaudhry, AS. (1996). Cell wall composition and digestion in sheep of wheat straw treated with calcium oxide, sodium hydroxide and alkaline hydrogen peroxide. Proceeds ofAustralian Society ofAnimal Production 21, 389. Chaudhry, A.S. and Miller, E.L. (1996). The effect of sodium hydroxide and alkaline hydrogen peroxide on chemical composition of wheat straw and voluntary intake, growth and digesta kinetic in store lambs. Animal FeedScience Technology 60,69-86. Cowan, R.T., Moss, R.J. and Kerr, D.V. (1993). Northern dairy feed base 2001.2. Summer feeding systems. Tropical Grassland 27, 180. Kaiser, AG, Havilla, E.G, Chopping, GD. and Walker, R.G (1993). Northern dairy feed base 200 1.4. Feeding systems during winter. Tropical Grassland 27, 180. Nutrient composition and in sacco digestibility of Rhodes grass (Means, g/kg DM, and probability). Recent Advances in Animal Nutrition in Australia 1997 University of New England, Armidale NSW 2351, Australia