Supplementation of Grass-fed Lambs
USDA researchers designed an experiment to determine the effect of forage-based production, either grass-fed or grass-based with modest supplementation, on gastro-intestinal nematode (GIN) infection and growth of fall-born lambs.
Weaned, fall-born Katahdin lambs were rotationally grazed on predominantly grass pastures. legumes and forbs as grass quality waned. Half the lambs received no supplement. The other half were fed a grain by-product supplement (15% CP) at 0.5% of body weight per day.
In the first year of the experiment, average daily gain (ADG) was greater for the supplemented lambs than the non-supplemented ones. There was no difference in the second year. Rams gained faster than ewes. Fecal egg counts (FEC) were similar between treatment groups, but supplemented lambs had greater packed cell volume (PCV), especially 28-d post weaning.
Results suggest that moderate supplementation should result in greater weight gains in fall-born lambs and improved tolerance to GIN when forage quality is limiting. Whereas, high quality forage should result in good gain without supplementation.