Using markers to estimate apparent dry matter digestibility, faecal output and dry matter intake in dairy ewes fed Italian ryegrass hay or alfalfa hay

Thirty six individual digestibility balances with eight diets were conducted. Experimental diets were (1) high-quality Italian ryegrass (Lolium multiflorum) hay (160 g CP/kg DM) (RG1), (2) the former hay (RG1) plus 0.6 kg/day of concentrate, (3) medium-quality Italian ryegrass (134 g CP/kg DM) hay (RG2), (4) the former hay (RG2) plus 0.6 kg/day of concentrate, (5) low-quality Italian ryegrass (81 g CP/kg DM) hay (RG3), (6) the former hay (RG3) plus 0.6 kg/day of concentrate, (7) medium-quality (181 g CP/kg DM) alfalfa (Medicago sativa) hay fed alone and (8) the former alfalfa hay supplemented with 0.6 kg/day of concentrate. Indigestible acid detergent fibre (IADF), acid detergent lignin (ADL), indigestible acid detergent lignin (IADL) and rumen-undegraded dry matter (RUDM), as internal markers, and chromic oxide (Cr2O3) as an external marker were used to estimate digestibility and faecal output of DM, respectively. By combining RUDM and Cr2O3 to predict forage intake, the following best equations were obtained for ryegrass (1) y = 233.87 + 0.832x (n = 10; r = 0.94; p < 0.001; residual SD = 73.7) and alfalfa (2) y = 423.84 + 0.771x (n = 10; r = 0.98; p < 0.001; residual SD = 119.1), y and x being measured and estimated DM intake, respectively. In conclusion, it was possible to estimate individually the dry matter intake by dairy ewes kept in groups with minimal disturbances in their social and competitive feeding behaviour. (C) 1999 Elsevier Science B.V. All rights reserved.