Sainfoin can be included up to 40% in the concentrate of finishing lambs without impairing their performance, rumen fermentation, and carcass quality.

Sainfoin (Onobrychis viciifolia) is an excellent forage legume to be included in sheep diets as fresh forage, but its inclusion in concentrates fed to indoor lambs reared has been scarcely studied. This study evaluated the effects of including different levels of dehydrated sainfoin in the concentrates fed to light lambs during the finishing period on animal performance, ruminal fermentation, and carcass traits. Twenty–six weaned male Rasa Aragonesa lambs (14.0 ± 0.49kg body weight) were randomly grouped and individually fed ad libitum with isoproteic and isoenergetic pelleted concentrates containing 0% (0SF; n=9), 20% (20SF; n=9) or 40% sainfoin (40SF; n=8) for 40 days, from weaning to slaughter. In addition, an in vitro assay was carried out to evaluate the concentrates. The 40SF lambs had a higher dry matter intake (P < 0.01) and tended to show an improvement in average daily gain (P < 0.10). The diet had no effect on carcass weight, dressing percentage, rectus abdominis color or subcutaneous caudal fat color (P > 0.05). Regarding the rumen study, the diet did not affect most ruminal fermentation parameters (P > 0.05), except for pH, which was greater in 40SF lambs than in 20SF lambs (P < 0.05), and the proportion of acetic acid and the acetic:propionic ratio, both of which were higher in 40SF and 20SF lambs than in 0SF lambs (P < 0.01). The results from the in vitro assay showed that the 40SF diet decreased the in vitro dry matter degradability, increased propionic, and decreased butyric proportion compared to 0SF concentrate (P < 0.05), but no effect was obtained for gas, methane, total volatile fatty acids, and ammonia formation among diets (P > 0.05). The lack of detrimental effects on lamb performance and carcass traits suggests that the inclusion of up to 40% sainfoin in the concentrate of light lambs reared indoors would be advisable to promote the use of local forages.