Evolution of viscera and muscle fractional protein synthesis rate in lean meat selected hybrids and castrated Duroc pigs fed under moderate crude protein restriction

Differences in producing performance and organoleptic meat characteristics among pig genotypes and/or types are widely known. These parameters also subjected to the animal’s development, feeding management. Detailed knowledge of effects production phase (PP), type (PT), dietary protein availability their interactions on nutrient digestibility, nitrogen balance metabolism is essential information improve precision techniques. The experiment was a 2 (PP) × (PT) (diet) factorial design conducted with 32 male pigs, 16 entire F2 pigs progeny Pietrain sires Duroc Landrace dams, castrated purebred Durocs belonging two phases (growing: 29.5 ± 3.19 v. fattening: 88.6 6.26 kg BW), assigned one CP levels, either standard (SP: 17% growing 15% fattening) or low (LP: 13% fattening). Viscera muscle fractional synthesis rates (FSRs; %/day) were through single infusion L-[ring-2H5]-phenylalanine, subsequent blood sampling from 12 40 min, sample collection liver, duodenum, biceps femoris longissimus dorsi skeletal muscles after sacrifice. Fattening animals acquired greater feed ingestion capacity, average daily gain (P < 0.01) apparent ileal whereas showed higher FSRs both viscera (duodenum liver) dorsi. gain, retention FSR liver 0.01). Nevertheless, digestibility all amino acids lower compared 0.05). Protein barely influenced by content, although fed LP registered lowest for most SP-fed pigs. This may reveal differences acid requirements between PTs, receiving excess acids.