Effect of immune system stimulation and dietary methionine plus cysteine intake on protein deposition and digestibility in growing pigs

摘要

Immune system stimulation (ISS) can result in substantial reductions in animal productivity. In growing animals, reductions in whole body protein deposition (PD) that are induced by chronic ISS can be attributed largely to reductions in protein gain in muscle, as a result of increased protein degradation and decreased protein synthesis in this tissue (Breuille et al., 1997). Amino acids (AA) released from muscle are redirected towards organs involved in the animal's immune response. Previous reportshave suggested additional requirements for the sulphur containing AA(SAA), methionine or cysteine, during ISS for synthesis of metabolites that have important roles in the animal's immune response, such as glutathione, homocysteine, taurine, polyamines,choline and carnitine (Malmezat et al., 2000; Yu et al, 1993). An increased need for SAA may be linked directly to increased muscle protein degradation during ISS. Also, ISS can cause morphological and physiological changes in the gastrointestinal tractsuch as edema, change in gut motility, permeability, and microflora (Yamada, 1995). However, the impact of ISS on protein and AA digestibility has not been evaluated. Our objectives were to determine the impact of ISS on PD, protein and AA digestibility, and to explore whether additional dietary SAA supply can reduce the negative impact of ISS on PD in growing pigs.