Δ9 desaturase protein expression and fatty acid composition of longissimus dorsi muscle in lambs fed green herbage or concentrate with or without added tannins

The aims of this study were to investigate the effect of feeding system and of supplementation of tannins(8.93% DM) on the relationship between intramuscular fat content, fatty acid composition and D9desaturase(D9d) protein expression in longissimus dorsi muscle of lamb. Twenty-eight Comisana lambs (age45 days) were fed either vetch (Vicia sativa) or concentrate. The herbage diet was (i) lower in saturatedfatty acids (especially in C16:0), C18:1 n9 and in C18:2 n6; (ii) higher in C16:1 and C18:3 n3 whencompared to concentrate. Within each feeding system the lambs were divided into two sub-groups, oneof which received the diet without tannins supplementation, and the other was fed the diets supplementedwith the tannins from Quebracho (Schinopsis lorentzii). The animals were slaughtered at age105 days. The concentrate feeding system increased (p < 0.01) the total intramuscular fat content andthe amount of SFA, MUFA and n6 PUFA and decreased the level of n3 PUFA (p = 0.05) when comparedto the vetch-fed animals but did not affect D9 desaturase protein expression. There was no correlationbetween D9d protein expression and total intramuscular fatty acids, CLA and MUFA level. It was suggestedthat in ruminants, in contrast to monogastric animals, D9d expression does not play the key rolein intramuscular fatty acids formation. Tannins supplementation resulted in higher (p < 0.05) muscle levelsof transC18:1 and C18:2 n6. It has also increased D9d expression in the case of herbage-based dietbut not in the case of concentrate-based diet. The mechanism of tannins action on the enzyme expressionneeds to be elucidated.