Impact of Dietary Protein Levels and Gender on Carcass Characteristics and Meat Quality in Slow-Growing Ducks

The aim of the present study was to investigate the effects of different dietary protein levels on the carcass traits, meat quality characteristics, and nutrient composition of slow-growing ducks. At 22 days of age, the ducks were randomly divided into two groups and fed with low- or high-protein diets for 41 days, from 22 to 63 days of age. Each group consisted of six replicates, with each replicate containing 500 ducklings per pen (10 m × 10 m). The results showed that dietary protein had no significant effects on carcass traits, meat quality, amino acid profiles in breast muscle and thigh muscle, and fatty acid contents in breast muscle. However, it increased the contents of C14:0, C16:0, C16:1, C18:1, C20:4, SFA, MUFA, and ω-6 fatty acids (p < 0.05), and reduced the contents of C22:6, ω-3 fatty acids, and ω-3/ω-6 ratio in thigh muscle (p < 0.05). Female ducks fed with a low-protein diet had the contents of aspartic acid, threonine, serine, glutamic acid, glycine, tyrosine, and arginine in the breast muscle, along with a higher pH24 value (p < 0.05). Thigh muscle accumulated more isoleucine and histidine contents, and lower lysine and arginine in female ducks fed with a low-protein diet. Male ducks fed with a low-protein diet had higher contents of alanine, valine, methionine, isoleucine, leucine, and lysine in the breast muscle (p < 0.05). Furthermore, male ducks exhibited higher contents of C16:0, C18:1, C18:2, C18:3, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), ω-3, and ω-6 in breast muscle (p < 0.05). Male ducks fed with low-protein diets had higher C16:0 content in breast muscle, and female ducks fed with a low-protein diet had lower C16:1 and C17:0 contents (p < 0.05). In conclusion, this study suggests that dietary protein modulation can differentially regulate amino acid and fatty acid deposition in slow-growing ducks through gender-specific metabolic pathways and exert distinct effects on fatty acid metabolism.