The present study was conducted to determined the effect of either energy restriction(ER) or quantitative diet restriction(DR) on the expressions of lipogenic genes in the liver and myogenic genes in muscle in broiler male chickens. Diet restriction in all experiments was accomplished by providing chicks with 70% or 85% energy level of control (ER70, ER85), and 70% or 85% diet intake of control (DR70, DR85). Diet restriction groups of chickens were restricted for 7 days, starting at 8 days of age. Ad libitum feeding was resumed after the restriction periods, and continued through the end of the experiment at 35 days of age. A control group was fed ad libitum throughout the experiment. The body weight and feed intake was measured every week. Tissues were collected at 14 and 35 days of age and utilized for the analyses of the gene expressions.
Chickens in the restriction groups gained less during the diet or energy restriction period. The body weight of the ER and DR groups were similar to the control group during the realimentation period. however, the ER70 group was not caught up the body weight of control group by 35 days of age. The energy or diet restrictions for 7 days during early life of chicks decrease the contents of triglycerides and cholesterol in blood but those were not different among treatments after realimentation. Fatty acid synthase(FAS) and malic enzyme(ME) genes and transcription factors including SREBP, PPAR-γ, and C/EBP-α were down regulated by restriction regimen. However, as shown in triglycerides and cholesterol, the RNA expression levels of FAS and ME genes were not different among treatment groups at 35 days of age. Except ER85, the RNA expression levels of Myo-D and Myf-5 in all treatment groups were decreased by restriction regimen compared with control group. The mRNA expression of myogenin was down regulated by restriction regimen in all treatment groups. Myf-5 gene from ER85 was highly expressed at 35 days of age, but it was not different among other treatments. The RNA expression levels of Myo-D and myogenin were not different among treatment groups after realimentation at 35 days of age in broiler chickens. These results suggest that ER85 group shows the best growth performance by realimentation and the gene expressions of muscle development are also expressed as much as control group even during restriction period. However, ER70 group does not caught up the body weight of control group by 35 days of age and the expression of FAS is still low at this time point. ER70 is severe to normal growth of broiler chickens and it is better to avoid in the restriction regimen in broiler chickens.