Enhanced Protein Accretion and Vital Organ Growth with Intermittent Bolus Compared to Continuous Feeding in Neonatal Pigs

Abstract Text: Enhancing the efficiency of protein utilization through dietary interventions may provide new avenues for improving profitability in farm animals. In addition, neonatal pigs can serve as dual-use models for nutrition research in animal agriculture and biomedical fields. Recently, we showed that intermittent compared to continuous feeding enhances lean tissue accretion by increasing muscle protein synthesis in neonatal pigs. The aim of this study was to determine if these feeding modalities affect vital organ protein accretion and growth. Neonatal pigs (n = 6/treatment, 6-d-old) were fed the same diet in equivalent amounts continuously (CON) or intermittently (INT; meal every 4 h) for 21 d. Plasma branched-chain amino acids and insulin and fractional protein synthesis rates in liver, kidney, jejunum and ileum were determined on the last day of feeding. Fractional rate of protein synthesis in organs was measured using the flooding dose method, and activation of translation initiation factors was determined by polyacrylamide gel electrophoresis. Weight gain was greater (P < 0.05) for INT than for CON pigs and resulted in heavier body weights from 9 d of feeding onwards. Arterial branched-chain amino acid and insulin concentrations measured on the last day of feeding were greater for INT after the meal than for CON pigs (P < 0.05). Phosphorylation of ribosomal protein S6 kinase were higher in ileum and liver in INT compared to CON fed pigs indicating increased translation initiation signaling (P < 0.05). The proportion of rpS8 mRNA associated with polysomes in liver was greater in the INT compared to CON fed group (P < 0.05). Protein synthesis increased by 14% in jejunum, 48% in ileum, and 22% in liver (P < 0.05), while for the kidneys the increase was only modest. Jejunum, ileum, liver and kidneys were 41, 36, 73 and 55% heavier for pigs in the INT as compared to the CON group (P < 0.05). These results suggest that intermittent feeding, as compared with continuous feeding, enhances protein accretion in vital organ growth by up-regulating protein synthesis. Supported by NIH AR444474 and USDA/ARS 6250-51000-055.

Keywords: branched-chain amino acids, protein synthesis, insulin