Effects of grape seed supplementation, alone or associatedwith linseed, on ruminal metabolism in Sarda dairy sheep

Grape seed is a by-product of the winery and distillery industry which could be used inanimal nutrition. To test the hypothesis that dietary supplementation with this by-productcan decrease the biohydrogenation (BH) of healthy fatty acids (FA), the present study evalu-ated the effects of grape seed supplementation, alone or combined with linseed, on ruminalBH processes in dairy sheep. In this 60-d trial, 24 lactating Sarda dairy ewes were assignedto four homogeneous groups and fed as follows: (1) control diet (CON), (2) a diet supple-mented with 300 g/d per head of grape seed (GS), (3) a diet supplemented with 220 g/d perhead of extruded linseed (LIN), (4) and a diet supplemented with a mix of both grape seedand linseed (300 and 220 g/d per head, respectively) (MIX). Ammonia, pH, volatile fattyacids (VFA) and FA composition were determined in rumen liquor at three sampling dates(20, 40 and 60 d). Rumen pH was not influenced by diet (P>0.05). The ammonia content wasincreased (P<0.05) in GS and MIX compared with LIN and CON. The molar proportions ofacetate and propionate and their ratio were not affected by the diet (P>0.05), whereas themolar proportion of butyrate was the lowest in MIX. Rumenic acid (RA; CLA cis-9,trans-11)concentration increased in GS compared with CON (0.78 vs. 0.45 mg/100 mg FA; P<0.05),whereas the percentage of vaccenic acid (VA; C18:1 trans-11) tended to increase (P<0.10)in GS compared with CON. The concentration of VA was higher in MIX than in CON (8.18 vs.3.77 mg/100 mg FA; P<0.05), whereas RA did not differ between the same groups. The con-centration of linoleic acid (LA; C18:2 n–6) decreased and stearic acid (SA; C18:0) increasedin all supplemented groups, whereas linolenic acid (LNA; C18:3 n–3) decreased in the twogroups receiving grape seed compared with CON and LIN. The concentration of total odd-and branched-chain fatty acids (OBCFA) decreased in all supplemented groups comparedwith CON (P<0.05), evidencing that grape seed and linseed supplementation influencedthe ruminal BH processes. Grape seed was able to increase the accumulation of RA whensupplemented alone, and of VA when combined with linseed; however, the rumen accumu-lation of SA in both groups supplemented with grape seed evidenced that this by-productwas not effective in decreasing the BH of dietary polyunsaturated fatty acids (PUFA)