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Leucine supplementation of a restricted protein diet improves lean growth in neonatal pigs
Early weaning of neonatal pigs frequently results in a reduction in food intake due to stress, environmental changes, and a shift from liquid to solid diet. In humans, many low birth weight infants also experience growth failure due to feeding intolerance resulting in reduced nutrient intake. The branched-chain amino acid, leucine, has been shown to have anabolic effects on skeletal muscle. The objective of the study was to determine if prolonged enteral leucine supplementation improves lean growth in neonatal pigs fed a restricted protein diet. Five-day-old pigs (N = 46; 1.8 ± 0.3 kg initial BW) were fed by gastric catheter either a normal protein (NP; 22.5% protein, 2.4% leucine) or restricted protein (RP; 11.2% protein, 1.2% leucine) milk replacement diet or RP supplemented with leucine to the same level as in the NP diet (RPL). Pigs were fed 40 ml/kg BW per meal every 4 h for 21 d. Body composition was determined by dual-energy x-ray absorptiometry on d 0 and 20. Data were analyzed using the PROC MIXED procedure of SAS. Feeding the NP diet resulted in greater total body weight (5.2 vs. 4.5 ± 0.20 kg) after 21 d and change in lean body mass (3.0 vs. 2.5 ± 0.17 kg) compared to RP fed pigs (P < 0.05). Mass of the longissimus dorsi muscle (68 vs. 53 ± 4.2 g), heart (29 vs. 24 ± 1.2 g), and kidney (27 vs. 20 ± 2.1 g) were also greater in the NP than RP fed pigs (P < 0.05). Body weight (4.8 kg), lean body mass change (2.6 kg), and mass of the longissimus dorsi (61 g), heart (27 g), and kidney (23 g) in pigs fed the RP+L diet were intermediate to the RP and NP fed pigs. Prolonged leucine supplementation of a restricted protein diet has the potential to improve overall growth in neonatal pigs and infants with restricted protein intake through an increase in lean tissue growth.
This project was supported by NIH HD072891 and USDA NIFA 2013-67015-20438.
Keywords: protein, neonatal pig, body composition, lean growth, leucine