Four male intact grade cattle (Bos indicus) and four male intact native carabaos (Bubalus bubalis Linn.) were used in a 4x4 latin square experimental design with two square to determine the digestibility of nutrients in rice straw-based rations. The four treatments each consisted of 60% rice straw and 40% concentrate mixture. The concentrate mixtures were: I-12.5% crude protein, 0 urea: II-12.5% crude protein, 2.5% urea; III-18.5% crude protein, 0 urea; and IV-18.5% crude protein, 2.5% urea.
Dry matter digestibility of rice straw by cattle or carabaos were 42.85% and 44.14%, respectively. Rice straw had a total digestible nutrients (TDN) or 40.42% and 42.32% and a digestible energy (DE) of 1701 kcal/kg. and 1704 kcal/kg. on dry basis. Most animals lost some tissue nitrogen (0.63 and 0.33 gm daily for cattle and carabao respectively). Carabaos digested crude protein (P<.05) , crude fat (P<.05) and hemicellulose (P<.01) significantly better than cattle. Significantly (P<.05) higher digestibility values of dry matter, gross energy and hemi-cellulose were obtained with concentrate mixtures containing the higher crude protein level. Dry matter digestibility was enhanced by addition of 1% urea in the ration as partial protein supplier on the lower protein level, but not on the higher crude protein level.
On dry basis, ration 1 had 51.00, 50.83% TDN: and 2145 and 2070 cal DE/kg for cattle and carabaos, respectively, ration II - 49.29% and 52.52% RDN: 2044 and 2104 kcal DE/kg: ration III - 54.03% and 55.32% TDN; 2184 and 2199 kcal DE/kg; and ration IV - 52.64% and 52.27% TDN, 2153 and 2150 kcal DE/kg significantly higher TDN (P<.01) values were obtained with carabaos than cattle.
In vitro digestion trials were conducted using rumen inocula from fistulated bull and carabull. When rice straw was the sole substrate in vitro true dry matter digestibility (IVTDMD) was lowest (69.07%). With the increase in protein level, significant (P<.01) increase in IVTDMD followed. The same trend (increased IVADMD) was likewise observed in the Tilley and Terry method. However, IVADMD values more closely approximated the in vivo DMD although highly significant (P<.01) colleralation coefficients were obtained between in vivo DMD and both IVTDMD (r=0.78) and IVADMD (r=0.93) the IVTDMD and IVADMD were also highly correlated (r=0.93)