Effects Of Early Nutrition Restriction On Growth Mode And Carcass Quality And Analysis On Its Metabolic Programming Effects In Broiler Chickens

Experiments were conducted to evaluate the effects of early nutrition restriction on growth mode and carcass quality and approach to the mechanism of nutrition distribution and metabolic programming effects in broiler chickens.A total of 600 broiler chicks (Aconred) were randomly allocated into two treatments [ad libitum group (ALG) and nutrition-restricted group (NRG)] by weight and sex, each of which was replicated three times with 100 birds per replicate. Broilers kept in cages and received commercial diets for 63 days including three stages (0-21, 22-42, 43-63 day of age). From 1 to 21 day of age, the feed of NRG was deprived for 4 hours (10:00-14:00) per day to restrict the feed intake, while the feed of ALG was given ad Iibitum. In other stages, the birds of both groups had ad libitum access to the feed. Adequate water and 24 hours light provided per day. The total test period was 63 days. The growth performance, carcass composition, meat quality and biochemical index in muscle, liver, abdominal fat and serum of female broilers were determined at 21 and 63 day of age, respectively. The main results were as follows:1. The results of feeding experiment indicated that the growth of broilers was limited after nutrition restriction and resumed from the weight loss after nutrition resumption. From 1 to 21 day of age , ADFI, ABW and ADG of NRG were decreased by 12.59% (P＜0.01), 13.33% (P＜0.01) and 14.61% (P＜0.01) respectively in contrast to ALG. The weight loss of NRG compensated by 80.72% and 86.12% respectively at 42 and 63 day of age. However, the feed gain ratio and survival rate weren't influenced by nutrition restriction.2. The results of slaughter experiment showed that nutrition restriction had remarkable effects on carcass composition of broilers. Compared to ALG, at 21 day of age, PDEC, PDPEC, PDB, PDAF, PDLM and SFS of NRG were decreased by 2.42% (P＜0.05), 2.25% (P＜0.05), 9.54% (P＜0.01), 9.23% (P＜0.05), 4.62%(P＞0.05) and 15.38% (P＜0.05), while PDL and PDS were increased by 23.78%(P＞0.01)and 17.89%(P＜0.01), respectively. At 63 day of age, PDAF and PDLM of NRG were increased by 14.14% (P＜0.05) and 4.93% (P＜0.05), while other related parameters above changes didn't change significantly.3. The results of analysis for meat quality of breast muscle showed that the content of EE was increased by 20.61% (P＜0.01) while CP was decreased indistinctively (P＞0.05) at 21 day of age. The content of EE was decreased by 15.10% (P＜0.01) while CP was increased by 1.21% (P＜0.05) at 63 day of age. The content of cholesterol increased insignificantly (P＞0.05).4. The results of determination for lipid metabolism related enzymes in liver and abdominal fat indicated that, compared to ALG, the activity of hepatic HL of NRG was increased by 9.36% (P＜0.05), while the activity of MDH, ICDH, G-6- PDH was increased (P＞0.05) indistinctively. At 63 day of age, the activity of MDH, ICDH, G-6-PDH in liver of NRG was increased by 14.68% (P＜0.01) , 15.18% (P＜0.01) and 9.43% (P＜0.05) ,while, the activity of HL was decreased by 9.38% (P＜0.05) . At the same time, the activity of MDH, ICDH, G-6-PDH, LPL in abdominal fat of NRG was increased by 8.67% (P＜0.05) ,7.01% (P＜0.05) ,13.77% (P＜0.01) and19.94% (P＜0.01)respectively, while HSL was decreased by 19.18% (P＜0.01).5. The results of biochemical parameters in serum showed that, at 21 day of age, the concentration of TG, Glucose, TP, HDL-Ch ,UA and the ratio of Glucose to NEFA was decreased by 24.36% (P＜0.01) ,18.09% (P＜0.01) , 9.87% (P＜0.05) ,3.03% (P＞0.05) , 16.41% (P＜0.01) and 32.19% (P＜0.01) respectively, while the concentration of NEFA, T-Ch, VLDL-Ch, LDL-Ch was increased by 20.80% (P＜0.01) ,7.98% (P＞0.05) ,3.44% (P＞0.05) and 46.22% (P＜0.01) . However, reverse changes were found about these parameters at 63 day of age, the concentrations of TG, Glucose, TP, HDL-Ch and the ratio of Glucose to NEFA was decreased by 4.71% (P＜0.01) , 26.85% (P＜0.01) , 17.38% (P＜0.05), 13.97%(P＜0.01)and 37.04%(P＜0.01), while the concentration of NEFA, T-Ch, VLDL-Ch, LDL-Ch and UA was decreased by 23.59% (P＜0.01) ,7.87% (P＜0.05), 18.99% (P＜0.01) ,8.94% (P＞0.05) and 1.50% (P＞0.05) respectively.6. The results from hormone analysis in serum showed that, at 21 day of age, T₃ level of NRG was decreased by 22.46%(P＜0.01), while T₄ and the ratio of it to T₃ was increased by 9.24% (P＜0.05) and 28.49% (P＜0.01), and that insulin level was decreased by 39.14% (P＜0.01), while glucagon and the ratio of it to insulin was increased by 10.14% (P＜0.01) and 33.00% (P＜0.01), respectively. At 63 day of age, glucogan level of NRG and the ratio of it to insulin was decreased by 18.04% (P＜0.01) and 19.32% (P＜0.05) , while T₃ ,T₄, insulin concentration was not changed (P＞0.05) significantly. In addition, the leptin level in serum of NRG had decrease trend at 21 and 63 day of age (P＞0.05).Results above implicate:1. The low intensity (12.59% feed quantity restriction) and long time (0-21 d) nutrition restriction could induce posterior growth compensatory, and have no influence on the body weight, feed gain ratio and survival ratio at market age.2. This nutrition restriction project could change the carcass quality of broilers at 63 day of age. The weight of leg muscle and CP content of muscle are increased, and EE content of muscle decreased and the sediment of abdominal fat increased.3. Nutrition restriction could regulate the ratio of T₄ to T₃ and of glucagon to insulin and activities of related enzymes in liver and abdominal fat, as enhances catabolism of lipid and glucose for energy supply inducing decrease of abdominal fat sediment. However, after feed resumption, lipid anabolism in abdominal fat and liver increased while catabolism decreased, as induce more sediment of abdominal fat.4. Early nutrition restriction (21 days) could induce metabolic programming of lipid and protein but the lasting time has obvious distinction. Lipid metabolism programming could not but protein metabolism programming could last for 63 days, as implicates that this project of nutrition restriction is beneficial for the production in broilers by increasing the period of restriction or bringing forward slaughter day of age.In a word, early nutrition restriction could induce nutrition distribution and metabolic programming in broilers, furthermore resulting in changes of growth mode and carcass quality. Early nutrition restriction could induce different metabolic programming effects on abdominal fat, breast and leg muscle, as cause different sediment of fat and protein in these tissues.