| The study was to conducted to investigate the developmental changes of growth performance, carcass composition and fatty deposition in growing Jinhua and Landrace pigs by determing related enzyme activities, hormone, physiological and biochemical parameters, gene expression of lipid metabolism, and digestive function as well as digestive enzymes activities in gastrointestinal tract. The objective of this study was to approach to the mechanism that breed and age affecting growth performance, carcass composition and digestive function, and supply scientific foundations for technology of regulating fatty depostion in pigs and utilization of hybridization between local and foreign breeds of pigs.A total of 36 purebred piglets (sex balance in each breed, weaned at 28 days of age) were allotted to two groups according to breed. Each group has three replicates with 6 piglets (sex balance) in each replicate. The feeding experiment lasted 90 days after a 7-day of adaptation period. Jinhua pigs and Landrace were reared in the same conditions. All pigs had ad libitum access to a experimental diet and water via nipple drinkers. At their predesignated slaughter age (at 35,80, and 125 days of age),6 purebred piglets (sex balance) of each breed were randomly selected and slaughtered to determine carcass composition. Samples of serum, pituitary gland, liver, muscle as well as subcutenous adipose tissue, gastric mucosa, pancreas, duodenum, jejunum and ileum were collected for subsequent analysis.The special primers for GH, IGF-I, FAS, HSL, Leptin, LPL and P-actin were designed respectively according to the gene sequences reported previously in Genebank. The total RNA was extracted from pituitary, liver and subcutaneous adipose tissue of pigs and the target gene mRNA amplified through RT-PCR with special primers. The cDNA fragments of GH, IGF-I, FAS, HSL, Leptin, LPL andβ-actin were obtained. The PCR product was cloned into pUCm-T Vector and sequenced. Sequence analysis suggested that all the gene fragments gained in this study shared more than 98%indentity with the reported mRNA sequences (AY536527, NM214256, EF589048, AY686758, AF026976, AY686761 and DQ845171) of pig in Genebank. Based on the gene cloning, the suitable annealing temperature, Mg2+ concentration, and cycles in PCR system were discussed and the optimal semi-quantitative RT-PCR methods were construced to determine the developmetal changes of related gene expressoin of lipid metabolism in growing Jinhua and Landrace pigs.1. Results of feeding experiment showed that Jinhua pigs had lower initial weight, final weight and average daily gain compared with Landrace gilts (P＜0.05). In addition, average daily gain of Landrace pigs increased by 39.44%, and feed/gain decreased by 24.11% compared with that of Jinhua pigs (P<0.05). But average daily feed intake did not differ between the two breeds.2. Results of carcass evaluation indicated that the developmental changes of carcass composition and meat quality parameters in Jinhua and Landrace pigs followed the same age-dependent patterns. Compared with Landrace pigs, Jinhua pigs had higher carcass fat percentage, average backfat thickness, IMF, marbling score and subjective color score (P<0.05), meanwhile lower drip loss, longissimus muscle area and carcass muscle percentage (P<0.05).3. Gene expression of pituitary gland GH and hepatic IGF-I indicated that the developmental changes of GH mRNA abundance in pituitary gland of Jinhua and Landrace pigs presented the same age-dependent patterns, which decreased with age (P＜0.05). Jinhua pigs had lower GH mRNA level compared with Landrace pigs (P<0.05), and there was a negative correlation between GH mRNA level and carcass fat content in the two breeds (r:-0.790 (P<0.05) and-0.755 (P＜0.05), respectively). IGF-I mRNA level in liver of Landrace pigs increased with age (P＜0.05), whereas the the developmental changes of IGF-I mRNA level in Jinhua pigs were not observed (P > 0.05). Jinhua pigs had lower IGF-I mRNA level compared with Landrace pigs (P＜0.05). There was a negative correlation between IGF-I mRNA level and carcass fat content in Landrace pigs (r:-0.730, P＜0.05).4. Analysis of subcutanenous adipose tissue indicated that the developmental changes of FAS and HSL activities in subcutanenous adipose tissue followed the same trends in Jinhua and Landrace pigs. It was lower at 35 and 80 days of age, significantly increased at 125 days of age (P<0.05). Jinhua pigs had lower HSL activity, and higher FAS activity and FAS/HSL ratio compared with Landrace pigs (P<0.05). The developmental chnages of FAS mRNA, Leptin mRNA and LPL mRNA abundance followed the same trends in the two breeds, which increased with age (P＜0.05). Jinhua pigs had higher FAS mRNA, Leptin mRNA and LPL mRNA abundance compared with Landrace pigs (P<0.05). Althrough the developmetal changes of HSL mRNA abundance in the two breeds were not observed (P>0.05). Jinhua pigs had lower HSL mRNA abundance compared with Landrace (P<0.05). During the whole experimental period, the carcass fat content were markedly correlated with FAS mRNA, FAS/HSL mRNA ratio, Leptin mRNA and LPL mRNA abundance of Jinhua and Landrace pigs (Jinhua pigs r:0.802 (P＜0.05),0.804 (P<0.05),0.876 (P＜0.05),0.871 (P<0.05); Landrace pigs r:0.734 (P＜0.05),0.749 (P＜0.05),0.803 (P＜0.05),0.784, (P＜0.05).5. Analysis of serum sample indicated that the developmental patterns of serum GH, leptin, IGF-I, inslun, FT3, FT4 and FFA concentrations followed the same trends in Jinhua and Landrace pigs. Serum leptin, IGF-I and FFA concentrations increased with age (P＜0.05), but serum GH, FT3 and FT4 levels decreased with age (P＜0.05). Jinhua pig had higher serum leptin and insulin concentrations, and lower serum GH, IGF-I, FT3) FT4 and FFA concentrations (P＜0.05). During the whole experimental period, the carcass fat content was markedly correlated with serum leptin, IGF-I, insulin, GH and FT4 concentration of Jinhua and Landrace pigs (Jinhua pigs r.0.567 (P＜0.05),0.572 (P＜0.05),0.482 (P＜0.05),-0.443 (P＜0.05), and-0.541 (P＜0.05); Landrace pigs r: 0.607 (P＜0.05),0.578 (P＜0.05),0.534 (P＜0.05),-0.463 (P＜0.05), and-0.481 (P＜0.05).6. Results from analysis of endogenous digestive enzyme activity indicated that the developmental patterns of pepsin (in gastric mucosa and contents), typsin, amylase and lipase (in pancreas) activities followed the same trends in Jinhua and Landrace pigs, which increased with age (P＜0.05). Jinhua pigs had lower pepsin and typsin activities (P＜0.05), and higher amylase and lipase activities compared with Landrace pigs (P＜0.05). In additon, the developmental patterns of maltase, sucrase and lactase activities in small intestinal mucosa (duodenum, jejunum and ileum) followed the same trends in the two breeds. Maltase and sucrase activitie of samll intestinal mucosa increased with age (P<0.05), while lactase activity decreased with age in the two breeds (P＜0.05). Jinhua pigs have higher maltase, sucrase and lactase activities of samll intestinal mucosa compared with Landrace pigs (P＜0.05).7. Results from analysis of digestive organs morphology indicated that the developmental patterns of mucosa villi height and crypt depth in small intestine (duodenum, jejunum and ileum) followed the same trends in Jinhua and Landrace pigs. Mucosa villi height increased with age (P＜0.05), while crypt depth decreased with age (P＜0.05). Jinhua pigs had lower villi height and deeper crypt depth (P＜0.05).
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