Optimizing Energy Structure in Low-Protein Diets Reduced Body Fat Deposition in Geese

This study examined the effects of dietary crude protein (CP) level and starch: fat ratio (SFR) on glucose and lipid metabolism in geese. A total of 360 male Jiangnan White geese were allocated to a 3 × 2 factorial arrangement with two CP levels (14.5% and 16.5%) and three SFRs (SFR_20:1, SFR_11:1, and SFR_5:1) from 28 to 63 days of age. Under the low-protein condition, Both the SFR_11:1 and SFR_5:1 group enhanced body weight of geese at 63 d, but SFR _5:1 increased subcutaneous and abdominal fat deposition. Dietary SFR changed liver cholesterol metabolism and glycogen content, while CP levels mainly affected the activity of enzymes related to liver glucose and lipid metabolism: 14.5% CP increased AMPK and ACC activity, but decreased FAS, CS and G6PC activity. Both CP level and SFR altered muscle fatty acid composition, but the effect of SFR was usually more significant. An SFR of 11:1 was beneficial for improving the muscle fatty acid profile. Gene expression analysis further revealed that low protein compensatorily regulated liver energy metabolism, while excessive fat in low SFR diets led to lipid metabolism disorders. In conclusion, optimizing the energy structure of low-protein diets, especially by maintaining a medium SFR (11:1), could improve glucose and lipid metabolism in geese while increasing body weight.