In vitro digestion of mixtures of concentrate and hay using inocula from sheep and goats

Dry matter digestibility (DMD) of 5 roughages (barley hay, sudex hay, alfalfa hay, barley straw and acacia) and their combination (1:1) with a concentrate mixture (14 percent CP, dry matter basis) was determined by a two-stage in vitro technique. The in vivo DMD values had been determined previously using 3 wether Chios sheep (S) and 3 wether Damascus goats (G) fed at restricted levels. Inoculum from two sources (sheep and goats) was used to determine in vitro DMD values. The inocula were collected from 3 sheep and 3 goats fed an alfalfa hay diet for 3 weeks. The inocula from each species were bulked to minimize variability associated with inoculum from individual animals. There were no species differences in the DMD values determined in vitro (G, 62.8 vs S, 62.1 percent). In the in vivo studies goats tended to be less efficient than sheep on the alfalfa hay plus concentrate diet, but more efficient on barley straw and acacia plus concentrate diets. When inoculum from sheep was used the correlation coefficients between in vivo and in vitro DMD values were 0.90 and 0.94 for roughages and mixtures, respectively. The corresponding correlation coefficients for goats were 0.90 and 0.77. The present data suggest that the in vitro technique can be used to determine digestibility of roughages and roughage-concentrate mixtures and that inoculum from sheep gives more accurate results for mixtures