Effect of the addition of Nigella sativa seeds to low or high concentrate diets on intake, digestion, blood metabolites, growth and carcass traits of Barbarine lamb

This 82-day feeding experiment aimed to determine the response of sheep to high or low concentrate diets enriched or not with the seeds of Nigella sativa. Twenty eight Barbarine male lambs (Initial body weight 24.6 ± 1.87 kg) were randomly divided into four groups (n = 7). Each group was assigned to one of the following dietary treatments (as fed basis): low concentrate diet (LC) composed of 700 g/kg barley hay and 300 g/kg concentrate (Low concentrate, LC), high concentrate diet (HC) composed of 300 g/kg barley hay and 700 g/kg concentrate, LC enriched with 12 g/kg Nigella sativa seeds (LCN) and HC enriched with 12 g/kg Nigella sativa seeds (HCN). Sheep receiving HC-diets exhibited higher (P < 0.05) diet dry matter, organic matter and crude protein apparent digestibility, nitrogen retention, ruminal ammonia nitrogen (NH3-N) concentrations and average daily gain than LC-diets. Irrespective of the proportion of concentrate in the diet, the addition of Nigella seeds increased (P < 0.003) CP intake and (P < 0.05) the concentration of NH3-N (+10.7% for HC and 7.6% for LC), but it decreased (P < 0.05) protozoa population in the rumen mainly with LC diet (P < 0.001) and the concentration of plasma triglycerides. Sheep receiving Nigella seeds grew more (P < 0.001) than those fed on Nigella-free diets. The interaction between Nigella seed addition and forage to concentrate ratio decreased (P = 0.03) the feed conversion ratio (FCR) in LCN lambs. Carcass yield was not affected (P > 0.05) by forage to concentrate ratio and the addition of Nigella seeds to the diet. It is concluded that the addition of Nigella sativa seeds (12 g/day) to concentrate increased significantly the growth rate of Barbarine lamb receiving either low or high concentrate diets. Such positive impact was more important with HC than LC diet and is likely the result of the substantial increase of total dry matter intake.