Beatriz Gallardo

BACKGROUND: This work aimed to study the chemical composition and in vitro digestibility of seeds and pulp from grape pomace. In sacco degradability, ruminal fermentation of grape pomace fractions and plasma lipid peroxidation were also studied in sheep fed with or without grape pomace.RESULTS: Seed and pulp fractions of grape pomace had different values for cell walls (523 vs 243 g kg⁻¹ dry matter (DM)), crude protein (CP, 104 vs 138 g kg⁻¹ DM), ether extract (EE, 99.0 vs 31.7 g kg⁻¹ DM), polyunsaturated fatty acids (PUFA, 69.6 vs 53.3%) and extractable polyphenols (55.0 vs 32.1 g kg⁻¹ DM). The in vitro true digestibility, DM in sacco degradability and CP degradability of seeds and pulp were also different (0.51 vs 0.82, 0.30 vs 0.45 and 0.66 vs 0.39 respectively). The ammonia‐N concentration and total volatile fatty acids (VFA) in ruminal liquid were significantly lower and plasma lipid peroxidation was also numerically lower in sheep that consumed grape pomace.CONCLUSION: The nutritive value of grape pomace varies depending on the proportion of seeds and pulp. The interest of this by‐product in sheep feeding could be related to its polyphenol and PUFA content, which could improve meat and milk quality. © 2016 Society of Chemical Industry

Grape pomace is a by-product resulting from the winery industry that is rich in phenolic compounds. It could play a role as an antioxidant and, owing to its high fiber concentration, it would be an alternative ingredient to partially replace forage in the diet of small ruminants. The objective of this study was to evaluate the effect of dietary supplementation of vitamin E or different doses of grape pomace associated with linseed oil on milk fatty acid profile, composition, and yield. Forty-eight Churra ewes were fed with experimental diets consisting of a total mixed ration (TMR) containing 2.7% [on a dry matter (DM) basis] of linseed oil, forage, and concentrate at a 40:60 ratio. Ewes were assigned to 1 of 4 treatments: control (without grape pomace), vitamin E (with 500 mg/kg of TMR of vitamin E), grape pomace-5 (5 g/100 g of TMR of DM of grape pomace), and grape pomace-10 (10 g/100 g of TMR of DM of grape pomace). Experimental diets did not affect DM intake and milk yield and composition. The vitamin E supplementation had only a moderate effect on milk concentration of fatty acids (increase in α-linolenic acid and 16:0 and decrease in cis-9 18:1). Grape pomace supplementation did not affect the percentages of total saturated, monounsaturated, and polyunsaturated fatty acids. Levels of α-linolenic acid reached about 1% of total fatty acids as a consequence of the presence of linseed oil in the diets, were not modified with vitamin E, and remained unaltered in grape pomace-5 and -10 treatments. Linoleic acid was increased by the highest dose of grape pomace, but this ingredient did not modify the cis-9,trans-11 18:2 milk fat content. The concentration of total odd- and branched-chain fatty acids did not diminish in grape pomace-5 and pomace-10 treatments. The presence of grape residue did not modified the trans-11 18:1 and trans-10 18:1 contents, which might indicate that, under the conditions assayed, this winery by-product would not alter the pathways of rumen conversion of dietary unsaturated fatty acids.