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The objective of this study was to test the response of piglets to diets differing in total sulfur AA supply on the AA composition of body protein and the characterization and quantification of the main muscular proteins in piglets. Two diets (based on wheat, peas, soybean meal and corn starch) were formulated differing in Met supply (0.20 and 0.41% Met on a standardized ileal digestible basis) and total sulfur AA (0.45 and 0.70% Met+Cys). A total of 18 piglets (6 blocks of 3 pigs each) at 42 d of age were used in a comparative slaughter study. After slaughter, the whole animal was divided into five body components (carcass, blood, intestines, liver, and remaining parts). Samples of Longissimus dorsi (LD) were analyzed for collagen, actin and myosin contents. A deficient supply of sulfur AA resulted in decrease in the Met content of proteins in the whole body, blood, LD muscle, and remaining parts. The Cys content was lower in blood protein and tended to be lower in liver protein. A deficient supply of sulphur AA also reduced the Met content in protein gain in the whole body and LD muscle and tended to decrease the Met content of carcass protein gain. The myosin and actin content (per 16 g N) was reduced with age but was not affected by the sulfur AA content in the diet. The myosin to actin ratio was not affected either. In conclusion, the AA supply appears to affect the AA composition of body protein and different body proteins are affected to a different extent. This questions the use of a constant ideal amino profile, but also illustrates the plasticity of the animal to cope with nutritional challenges.
JA Conde-Aguilera, R Barea, and J Van Milgen. 2009. Book of Abstracts EAAP, Barcelona, 584.
