The in situ ruminal degradability of concentrate feedstuffs in steers as affected by level of feed consumption and ratio of grass silage to concentrate

The effect of feeding level (11 and 17 g dry matter (DM)/kg body weight (BW) per day) and ratio of grass silage to concentrate (250:750, 500:500 and 750:250 g/kg DM) on the in situ ruminal degradability of concentrate ingredients was examined. Six ruminally fistulated Friesian steers were used in a six (treatments) by six (21 days period) Latin square experiment. Ruminal disappearance of DM, nitrogen (N) and organic matter (OM) from the test feeds was measured at 0, 2, 4, 8, 14, 24 and 48 h. The exponential model of Ørskov and McDonald was used to estimate degradation kinetics. r level of feeding nor forage to concentrate ratio had a significant effect on the ‘a’, ‘b’, ‘c’ values or effective degradability (ED) of DM, N and OM, except for an effect of diet on the ED of OM (P<0.05). There were no significant interactions between diet, level and/or feed for ‘a’, ‘b’ and ‘c’ values or ED for DM, N and OM when measured at an outflow rate of 0.05 h−1, except for a significant diet×level interaction for the ‘b’ value of DM (P<0.05) and the diet×level interaction for the ED of N (P<0.05). The feed incubated had a significant effect on the ‘a’, ‘b’ ‘c’ and ED of DM, N, and OM (P<0.001). In general, these data suggest that diet and feeding level do not substantially affect in situ ruminal degradabililty values for the range of concentrate feedstuffs examined in this study and therefore, any of the basal diets can be offered to the animal without affecting results obtained.