The chemical composition and in vitro digestibility of rice straws for ruminants

Abstract

Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 THE CHEMICAL COMPOSITION AND IN VITRO DIGESTIBILITY OF RICE STRAWS FOR RUMINANTS D. YULISTIANIA, J.R. GALLAGHERA, R.J. van BARNEVELDB and L. LEWIN * Dept of Animal Science, The University of Adelaide, Roseworthy, S.A. 537 1 B SARDI, Pig and Poultry Production Institute, Roseworthy, S.A. 537 1 ' Yanco Agricultural Institute, N.S.W. 2703 C Rice straw is the major component of crop residues in many tropical countries, and is commonly used as a ruminant feed. The chemical composition and in vitro digestibility of rice straw is affected by variety (Ibrahim et al. 1989) and differences in the proportions of the botanical fractions (Walli et al. 1988). The lower part of the plant is thought to be of higher quality due to lower contents of silica and lignin in the stem internodes. Winugroho and Sutardi, (1986) however, reported the ad libitum intake of the upper part was higher than the lower part. The objective of this study was to investigate the variation in the nutritional quality of the upper and lower parts of rice straw varieties. Straws from 4 varieties of rice (Doongara, Amaroo, Illabong and Millin) was divided equally by length into lower and upper parts. Nitrogen (N), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), lignin and silica content was determined for each part. In vitro organic matter digestibility (IVOMD) was also determined. Rumen fluid for the IVOMD study was taken from sheep fed on 50% luceme chaff and 50% oaten chaff. A 2 x 4 factorial design was used to analyse the data (Table 1). Table 1. Chemical composition and IVOMD of rice straw varieties (g/ kg) These results support the finding of Ibrahim et al. (1989) who found that standard chemical composition could not fully explain the variations in the in vitro digestibility of rice straw varieties. From this study it can be concluded that the chemical composition is not an appropriate method to evaluate the nutritional quality of rice straw varieties. IBRAHIM, M.N.M., TAMINGA, S. and ZEMMELINK, G. (1989). Anim. Feed Sci. Technol. 24: 83-95. WALLI, T.K., ORSKOV, E.R. and BHARGAVA, PK. (1988). Anim. Prod. 46: 347-52. WINIJGROHO, M. and SUTARDI, T. (1986). R uminant Feeding System Utilising Fibrous Agricultural Residues- 1986. pp. 127-132 (IDP: Canberra). 391