Effect of grape (Vitis vinifera L. cv. Pinotage) pomace supplementation on nutrient utilization in finisher lambs

The objective of the study was to evaluate the effects of feeding varying levels of sun-dried red grape pomace (DGP; Vitis vinifera L. cultivar Pinotage) on nutrient digestibility, rumen fermentation, microbial nitrogen (N) supply, N retention and efficiency of N utilization in lambs. Twenty-one Dohne Merino wether lambs (6.0 +/- 1.0 months and 51.6 +/- 4.70 kg initial body weight) were randomly assigned to three diets containing 0, 100 and 200 g DGP per kg of diet dry matter in pelleted total mixed rations (TMR). The experiment consisted of 14 days for adaptation to the diets and 7 days for data collection. Intake of neutral detergent fiber (aNDFom) and starch decreased linearly (P <= 0.05) while ether extract intake increased linearly (P <= 0.05) with the addition of DGP. Apparent total tract aNDFom digestibility decreased linearly (P <= 0.05) with increasing levels of DGP. Total volatile fatty acids (VFA) production was quadratically (P <= 0.05) influenced by DGP addition. Increasing levels of DGP led to a linear decrease (P <= 0.05) in concentrations of butyrate and valerate. Allantoin, microbial N supply, total purine derivatives excreted linearly declined (P <= 0.05) with DGP addition. Nitrogen retention and the efficiency of N utilization were not influenced by diet (P > 0.05). Overall, addition of DGP in the lamb finisher diets reduced carbohydrate intake, microbial N yield, total purine derivatives excreted and increased total VFA concentration but did not have adverse effect of DGP on N retention and the efficiency of N utilization.