Effects of dietary starch and fiber concentration on post-prandial evolution of blood metabolites and hormones in lactating ewes and goats

This study explored the post-prandial hormonal evolution of mid-lactating ewes and goats fed a high starch diet (HS; 20.0% starch, on DM basis) and a low starch diet (LS; 7.8 starch, on DM basis) to understand why in this study ewes partitioned more energy in favor of body reserves and goats in favor of mammary gland. Blood post-prandial samplings were collected at 30, 60, 120, 180 and 240 min post feeding to analyze hormones and metabolites. Plasma NEFA (P=0.005), GH (P=0.0007) and leptin (P<0.0001) were affected by the effect of time. Plasma glucose concentration did not change during the time and was higher in ewes than in goats (60.34 vs 50.31±1.99 mg/dl; P<0.0001). Goats, had higher plasma GH (2.28 vs 1.47±0.37 ng/ml; P=0.037) and leptin concentration (21.08 vs 11.62±1.80 ng/ml; P<0.0001) whereas plasma insulin and IGF-I were higher in ewes than in goats (0.19 vs 0.14±0.02 gg/l; P=0.018; 154.31 vs 107.80±14.92 ng/ml; P=0.0036). The type of diet did not affect any of the metabolic parameters considered. In conclusion, this work suggested that the different hormonal profile observed between the two species could be the cause of the different nutrient partitioning.