Abstract
Simple SummaryLight weaning weight piglets have slow post-weaning growth performance and require longer days to reach slaughter weight. Birth weight and early postnatal nutrient intake are the main factors contributing to light weaning weight. Our results suggested that intrauterine growth-retarded (IUGR) piglets fed adequately during the suckling period do not catch up with the same muscle growth and development compared with normal birth weight piglets. Postnatal early nutritional restriction resulted in impaired skeletal muscle growth and delayed myofiber maturation of the piglets.Piglets with light weaning weight commonly have a slow post-weaning growth rate due to impaired skeletal muscle development. Therefore, the present study aimed to investigate the impact of birth weight and nutrient intake on skeletal muscle development, myofiber maturation, and metabolic status of early-weaned piglets. Twelve pairs of normal birth weight and intrauterine growth-retarded (IUGR) piglets (seven days old) were randomly assigned to receive adequate nutrient intake or restricted nutrient intake for 21 days. Serum and muscle samples were collected for further analysis. The results indicated that muscle weight, cross-sectional areas, and muscular glycogen were lower (p < 0.05) in both IUGR and restricted fed piglets. Nutrient restriction decreased the contents of RNA, the RNA to DNA ratio, and the percentages of myosin heavy chain (MyHC) IIx (p < 0.05), whereas increased the activity of β-hydroxy-acyl-CoA-dehydrogenase (HAD), the ratio of HAD to citrate synthase, as well as the percentages of MyHC I (p < 0.05). In addition, nutrient restriction significantly decreased muscular glycogen, mRNA levels of fatty acid transport protein 1, cationic amino acid transporter 1, and glucose transporter 4 in IUGR piglets compared with the other groups (p < 0.05). The results of the present study showed that IUGR impaired skeletal muscle growth and disturbed the hormone and mRNA expression of genes related to energy metabolism, which led to a more severe energy deficit when receiving postnatal nutritional restriction. Postnatal nutritional restriction resulted in delayed myofiber maturation of the piglets, which may be associated with the transformation of MyHC isoform and the change of metabolic status.
Highlights
Genetic improvement in pig production led to a dramatic increase in litter size over the last decades [1]
The present study was designed to investigate the impact of early postnatal nutritional intervention on skeletal muscle development and myofiber maturation in intrauterine growth-retarded (IUGR) piglets to delineate the role of birth weight from postnatal nutritional intervention
The present study supported this finding in that IUGR piglets had lower absolute muscle weight but greater brain to muscle weight than normal birth weight (NBW) piglets, indicating that brain development was highly prioritized in IURG piglets
Summary
Genetic improvement in pig production led to a dramatic increase in litter size over the last decades [1] Such an increase in litter size results in uterine crowding and limits intrauterine nutrient supply for the growing fetuses that induce intrauterine growth-retarded (IUGR) piglets [2]. Milk intake per individual piglet decreases as litter size increases in modern hyper-prolific sows, which in turn worsens the suckling competition for IUGR piglets. Owing to this fact, several studies reported light weaning weight in IUGR piglets compared with NBW piglets [3,4,5]. Information is lacking whether nutrient restriction could affect skeletal muscle development and myofiber maturation in piglets with light weaning weight, especially in IUGR piglets
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