A moderate threonine deficiency differently affects protein metabolism in tissues of early-weaned piglets

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A moderate threonine deficiency may affect differently tissue protein metabolism. In this study, we compared protein metabolism in the small and large intestines, the liver, and the carcass of piglets ( Sus scrofa) pair-fed either a control well-balanced diet (C: 9.3 g threonine/kg diet) or a low threonine diet (LT: 6.5 g threonine/kg diet) for 2 weeks. In the small intestine, the LT diet did not modify protein deposition, fractional protein synthesis rate ( K S) and AA protein composition. Ubiquitin mRNA level, a component of the ubiquitin-dependent proteolytic pathway, was significantly decreased in the jejunum of the LT piglets. Protein deposition measured in the carcass and the colon, and K S measured in the semitendinosus muscle and the colon, did not differ between LT and C piglets. Nevertheless, in these compartments, threonine content was reduced indicating deposition of proteins less rich in threonine. In the liver, protein retention was reduced, K S was increased and AA protein composition was modified in the LT compared to the C piglets. In conclusion compared to the other compartments, small intestinal protein metabolism seems to be less sensitive to a moderate dietary threonine deficiency. This indicates that dietary threonine extraction by the small intestine may reduce threonine availability for the other tissues when young piglets were fed a diet marginally deficient in threonine.