Comparative Study On Development Of Adipose Cells And Fatty Acids Composition Of Intramuscular Fat In Different Genotype Pigs Under Different Dietary Nutrient Levels

84 healthy Rongchang and DLY barrows(10kg BW) were randomly allocated to two treatments(higher and lower dietary nutrient level )groups, each group had 6 replicates of 7 pigs each. The lower dietary nutrient level for these two genotype pigs was designed according to recommendations of GB 7223-1987 (Nutrient Requirements of Rongchang Pig, 1987),and the higher dietary nutrient levels were according to revised nutrient requirements of Chinese lean-meat pig(for Rongchang pigs) and Nutrient requirements of swine by NRC(1998)(for DLY). One pig selected from the all groups was slaughtered when their body weights(BW) reached at 10, 20,35,50,80 and 110kg respectirly to study on development of adipose cells and fatty acids composition of intramuscular fat in different genotype pigs under different dietary nutrient levels. The results of this study were as follows.Genotype and body weight had significant effects on the deposition of subcutaneous,splanchnic and intramuscular fats. The depositions of subcutaneous,splanchnic and intramuscular fats in both Rongchang pigs and DLY pigs showed a rising tendency with their body weights increasing under different dietary nutrient levels. The values in Rongchang pigs in two dietary nutrient level groups were all higher than in DLY pigs in two dietary nutrient level groups, and the difference of contents in subcutaneous and splanchnic fats was very significant(P﹤0.01) after body weight over 35kg. There was a increasing toward to fat deposition in all the fat tissues when the dietary nutrient level was increased, but the differences was not significant (P﹥0.05). There were very significant differences(P﹤0.01) among all data for fat deposition and carcass properties. It was concluded that Rongchang pig had advantage on fat deposition and the impact of dietary nutrient level on fat deposition was not significant(P﹥0.05).The influences of genotype and body weights to adipose cells development in the tissue were remarkable, At 50～110kg of pigs body weights, the Rongchang pig's hypodermic fat deposition mainly was caused by adipocyte hypertrophy, but for the DLY pig both adipocyte hypertrophy and hyperplasia performed the function. The DLY pig's adipocyte cells obviously was smaller than the Rongchang pig's. Rongchang pig's adipocyte hypertrophy function in subcutaneous adipocyte cells was stronger than in DLY pig's. The change of dietary nutrient level had no significant effect (P﹥0.05)on differentiation,hyperplasia and hypertrophy functions of subcutaneous adipose cells in Rong Chang pig's and DLY pig's. It was indicated that the influence of genotype on hypodermic adipose cell development was very greater, but the influence of the dietary nutrient level was very weak.There were great differences in fatty acids composition of intramuscular fat for Rongchang pigs and DLY pigs under different dietary nutrient levels. Saturated fatty acids in the two genotype pigs mainly included stearic acid and palmitinic acid. But unsaturated fatty acids mainly included oleinic acid,linolic acid and palmitoleic acid. Different genotype pigs had different intramuscular fatty acid composition. The fatty acid composition of Rongchang pig's fed the two nutrient levels were C14:0,C16:0,C16:1,C18:1,C20:0,SFA,MUFA,SFA+MUFA ,which was higher than that of DLY pig's fed the two nutrient levels.The differences of contents of C18:1,SFA,MUFA,SFA+MUFA were very significant(P﹤0.01), and the differences of contents of C16:0,C16:1,C20:0,SFA were significant (P﹤0.05). Contents of C18:2,C18:3,USFA,PUFA,PUFA/SFA for the Rongchang pig's were lower than for the DLY pig's fed the two dietary nutrient levels. The differences of contents of C18:2,C18:3,PUFA,PUFA/SFA were very significant(P﹤0.01), the difference of content of USFA was significant(P﹤0.05). The influence of dietary nutrient level on intramuscular fatty acid composition was not significant(P﹥0.05). Reducing the dietary nutrient level for DLY pig's could cause extremely increase of quantities of C18:1,MUFA,SFA+MUFA in intramuscular fat, and extremely decrease of the composition of C18:2,C18:3,PUFA,PUFA/SFA(P﹤0.01). C18:1,MUFA,SFA+MUFA contents in intramuscular fat had positive correlation to meat quality properties, such as marble lines grading,IMF,flesh red degree a * and flesh grading(P﹤0.01). But the C18:2,C18:3,PUFA,PUFA/SFA contents had negative correlation to meat quality properties including marble lines grading,flesh red degree a * and flesh grading(P﹤0.01). The results indicated that both impacts of genotype and dietary nutrient level on intramuscular fatty acid composition were very greater.