Effects of dietary supplementation with alfalfa (Medicago sativa L.) saponins on lamb growth performance, nutrient digestibility, and plasma parameters

Fifty Hu male lambs (aged three to four months with a body weight of 22.3 ± 0.15 kg) were chosen to study the effects of supplementation with dietary alfalfa saponins (AS) on growth performance, nutrient digestibility, and plasma parameters. Lambs were assigned to five groups with 10 lambs per group in a completely randomized design. Different diets were offered at a 50:50 forage to concentrate ratio in which different amounts of AS were provided (0, 500, 1000, 2000, or 4000 mg/kg of dry matter intake). Diets were offered twice daily (at 08:30 and 16:30) for a period of 90 days (three months). Growth performance, apparent nutrient digestibility, body measurement indexes, and plasma parameters were determined each month. The final body weight differed among treatment groups during the initial (P = 0.011) and final months (P = 0.039) of the trial, respectively. However, no detectable effects of AS treatment on average daily gain (P = 0.072) or feed conversion ratio (P = 0.113) were found. Nutrient digestibility increased with AS dose, especially the digestibility of dry matter (P = 0.005), crude protein (P = 0.005), and acid detergent fiber (P = 0.013) on average. No significant differences were found among treatments for all body measurement indexes. Plasma glucose (P = 0.016), triglyceride (P = 0.018), and alanine transaminase (P = 0.002) levels decreased with increasing AS dose on average. These results indicated that AS plays an important role for increasing both nutrient digestibility and levels of plasma metabolites.