Feeding behavior and ruminal environment of lambs fed only pasture indoors or grazing

Abstract

The effect of two feeding methods (indoors vs. grazing.) was studied in ovines. Twelve lambs fed fresh forage (predominant­ly Lotus corniculatus) during 6 h per day were allocated in 2 groups: forage cut and offered to animals housed indoors (I) or at pasture (P). Feeding behavior, ruminal pH and ammonia (N-NH3) concentration, and in vitro ruminal liquor activity using the gas production technique were studied. The feeding behavior of the lambs was different according to the treatment, particular­ly, the time spent ruminating. Lambs at pasture spent less time ruminating than indoors lambs (mean values: 49 and 4 minutes during the first 6 hours relating to the meal beginning, I and P respectively, P=0.004). Ruminal pH was not affected by the way of access to forage (mean values: 6.94 and 6.62, I and P respec­tively, P=0.715) but lambs at pasture had higher N-NH3 concen­tration (mean values: 23.5 and 30.1 mg/dL, I and P respectively, P<0.001). The in vitro ruminal liquor activity of lambs indoors and at pasture was similar (mean volumes of gas until hour 96 of incubation: 205 and 169 mL/incubated DM, I and P respective­ly, P=0.317). These results suggest that lambs at pasture would have presented a more intense selection of diet, eating more quantity of leaves than lambs indoors, without changes in the rumen fermentative activity.