| Skeletalmuscle has a lower priority in nutrient partitioningin response to thechallenges the fetus faces during development, renderingit particularly vulnerable to Maternal nutrient supply fluctuations. And previous studies have shown that low birth weight piglets retarded the development of skeletal muscle. Low birth weight piglets lower blood leucine levels may be a factor which blocked muscle development, and leicine could improve the development of neonatal piglets skeletal muscle by perfusion. Hereinthe objects of our study aim to investigate the effects of nutrition levels of gilts during gestation on offspring’s growthperformance and development of skeletal muscle and to evaluate the effects of leucinesupplementation to neonatal piglets on growth performance and development of skeletal muscle.Experiment Ⅰ.Effect of nutrition level of gilts during gestationon offspring’ development of muscle fiber in skeletal muscleThis experiment was conducted to study nutrition level of gestating gilts on offspring’s muscle growth and muscle fiber development. Thirty-three crossbred LY (Landrace×Yorkshine) gilts with similar age (254±10 d) and body weight (149.2± 7.9 kg)were randomly assigned to three treatment groups:low nutrient level group (LN, maternal low nutrients diet), appropriate nutrition group (AN, maternal adequate nutrients diet) and high nutrient level group (HN, maternal high nutrients diet) with eleven gilts for each treatment. During early pregnancy (d 1 to 30 of gestation),1.0M (Maintenance requirements of nutrient) diet was provided to AN group gilts. The nutrition provided to the AN-gilts during mid (d 31 to 90 of gestation) and late (d 91 of gestation to parturition) pregnancy was 1.2M and 1.5M, respectively. The LN-gilts fed 75% of the AN-gilts intake and HN-gilts fed 150% of the AN-gilts intake. All gilts were fed the same diet during gestation and lactation in accordance with NRC (1998), supplying 3.0 Mcal DE/kg and 14.5% crude protein from day 1 to 90 of gestation,3.2 Meal DE/kg and 15.5% crude protein during late gestation (d 91 of gestation to parturition). Six piglets with weight close the average level were selected from each group for slaughter at birth as well as at weaning. The main results were as follows:1) The birth weight and weaned body weight of piglets were highly significantly (P<0.01) increased as well as the weight of longissimus, psoas major, semitendinosus, gastrocnemius (P<0.01) in newborn piglets with the increased nutrition level fed to the gilts. The relative weight of longissimusand semitendinosus of newborn piglets in LN group were significantlydecreased (P<0.05) compared with that in AN group.2) No effects of maternal nutrition level during gestation on muscle fiber size, muscle fiber density and muscle fiber cross-section in newborn and weaning piglets were found (.P>0.05).3) The muscle proteinconcentration washighlysignificantly increasedin maternal adequate nutrient (AN) group compared with that in HN group (P<0.01) and LN group(P<0.05).4) The mRNA expression of MYHCⅡ x was significantly decreasedin maternal adequate nutrient (AN) group compared with that in LN group (P<0.05).5) The mRNA expression of Myogenic regulatory factor 4 (MRF4) in AN longissimus was significantly higher than the LN (P<0.05) and HN (P<0.05); Also has a trendon MRF4 of weaning(P=0.09), butAN was lower than the LN in weanling piglets (P=0.09).Experiment II Effect ofLeucine supplementation on growth performance and muscle fiber development of neonatal skeletal muscleThis experiment was conducted to evaluateeffect of leucine supplementation to neonatal piglets on growth performance and the development ofskeletal muscle. Twelve 7-day PIC weak piglets (intrauterine growth retardation, IUGR) and twelve 7-day PIC normal weight piglets (Normal Birth Weight, NBW) were selected.2×2 experimental design was carried out. Twelve IUGR were assigned into two treatment groups equally, fed formula milk and formula milk+1.2% LEU, respectively; twelve NBW were assigned into the other two treatments equally and fed formula milk and formula milk+1.2% LEU, respectively. During the experiment period, the waterwas provided ad libitum and the experiment period was 21 days. After the piglets were slaughtered, the muscle were obtained rapidly and placed in liquid nitrogen and then stored at-80℃ for subsequent analyses.The main results were as follows:1) The average daily dry matter intake (ADMI) of NBW piglets each stage and the whole test period was significantly higher than IUGR (P<0.01～0.07), accordingly, ADG of NBW piglets the whole test period was significantly higher than IUGR (P<0.05), and net gain was significantly higher than IUGR(P<0.05). Dietary supplementationof leucine significantly increased the third week ADMI (P<0.05), andhas a trend to improve third week (P=0.08) and the whole period ADG(P=0.1), and reduced significantly third week FCR (P<0.05).2) NBW increased significantly longissimus dorsi, semitendinosus, psoas, soleus and gastrocnemius muscle weight (P<0.01), no effect of leucine onthe weight of longissimus dorsi, semitendinosus, psoas, soleus and gastrocnemius (P>0.05).3) The levels of serum insulin and IGF Ⅰ did not influence by NBW (P>0.05), leucine elevated significantly serum insulin levels (P<0.01), but not IGF Ⅰ (P>0.05).4) No effects of body weight and leucine on myofiber type (P>0.05). The expression of Transforming growth factor betal(TGF-β1) of NBW longissimuswas significantly higher than IUGR(P<0.01), but lower in semitendinosus (P<0.05); Dietary supplementationof leucine has a tendency to increase the expression of IGF-1 of semitendinosus (P=0.06).Base on the above results, it could be concluded that:(1) Body weight of newbrn and wenling piglets were increased by the rise of maternal nutrition. But muscles growth and muscle fiber development of offspring was damaged by over and under nutrition.(2) Body weightsignificantly affect the growth performance of newborn piglets, the supplementation of leucine accelerated significantly the latter FCR, but not the development of myofiber. |
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