Effects of delayed fat supplementation on post-prandial rumen metabolism, lamb quality and fatty acid composition of rumen effluent

Sheep farmers have an option to incorporate fat supplements into the ration of grazing ruminants. Farmers choosing this option will have to select a time for offering that supplement. It might be practical to feed the supplement in the morning or evening. However, the time at which that supplement is fed should not compromise nutrient digestion or the enhancement of ruminant product fatty acid composition. Consequently, the effects of feeding a fat enriched supplement, at a delayed time on rumen metabolism, lamb quality, and fatty acid composition of effluent digesta were investigated in three experiments. In experiment 1, treatment (time of supplementation) of a soybean oil and soybean meal supplement on diurnal rumen activity and total tract nutrient digestion of lambs fed orchard grass hay were investigated. Treatment did not affect differences in hay intake, urine production, urine NH 3-N, nitrogen retention, or nutrient digestibility. However, time of supplementation did affect ruminal digestion and kinetics. In experiment 2, the afternoon feeding effects of fat, protein, and fat enriched protein supplements on performance and tissue fatty acid composition of grazed lambs were evaluated. The type of fat supplement that was fed to lambs influenced grazing activity, forage intake, lamb growth and fatty acid profile of tissues. Lastly, in experiment 3, the impact of delayed supplementation with fat, protein or a fat enriched protein blend, on diurnal changes in fermentative digestion, forage digestibility and effluent digesta fatty acid composition in continuous culture fermenters were investigated. In this study, delayed fat supplementation did not alter post-prandial fermentation or compromise fermentative digestion and nutrient digestibility. Producers who wish to utilize low levels of supplemental soybean oil to high forage fed lambs may not be overly concerned about the time at which that supplement is fed