| Beta-hydroxy-beta-methylbutyrate(HMB), the metabolite of leucine, plays an important role in muscle protein metabolism and it can be used as a nutritional supplement to promote muscle growth.This present study was conducted using White Feather Broilers as trial animals and in ovo feeding(IOF) HMB into embryo during incubation period, to explore the mechanism of the growth of muscle in broiler chickens through the three experiment of incubation and feeding broilers. The main research contents and results were described as follows.Experiment 1. Effects of In Ovo Feeding of HMB on Hatchability, Growth Performance,Carcass Composition and Meat Quality in BroilersA total of 720 fertile eggs from Arbor Acre breeder were allotted into 3 treatments with 6replicates and 30 eggs in each replicate. HMB(1 mL, 0.1%) was injected into the air cell on day 7 and day 14 of incubation and into the amnion of embryos on day 18 of incubation with 1mL 0.1% HMB, a control group without injection was also included. After hatching, 72 male chicks from each treatment were divided into 6 replicates with 12 birds. The results showed as follow: 1) IOF of HMB significantly increased the hatchability of broilers(P<0.05), promote the growth of early broiler body weight gain, no significant improvement in feed conversion efficiency(F/G), 7 and 18 embryonic were have the advantage for injection than in 14 embryonic in production performance. 2) IOF of HMB resulted in more breast muscle and less abdominal fat at 21 d posthatch(P<0.05), no obvious effects on leg muscle percentage. 3) IOF of HMB improved when the broiler plasma GLU content at 21 d(P>0.05), effects on plasma total protein, uric acid, creatinine were not obvious. 4) IOF of HMB did not change the color, pH value, drip loss, cooking loss and shear force of breast muscle in broilers at42 d posthatch(P>0.05). Together, IOF of HMB promoted hatchability and body weight gain in male broilers. IOF of HMB did not change feed conversion efficiency, plasma protein metabolism and breast meat quality.Experiment 2. Effects of In Ovo Feeding of HMB on Growth Performance, Meat Production, Blood Hormones Level and Hormone Receptor mRNA Expression in BroilersA total of 720 fertile eggs from Arbor Acre breeder were allotted into 3 treatments with 6 replicates and 40 eggs in each replicate. HMB(1 mL, 0.1%) was injected into the air cell on day 7 of incubation and into the amnion of embryos on day 18 of incubation, a control group without injection was also included. After hatching, 96 male chicks from each treatment were divided into 6 replicates with 16 birds. The results showed as follow: 1) Compared with the control group, IOF of HMB significantly increased the BW at hatch(P<0.05). At 42 d posthatch, IOF of HMB on 18 d of incubation increased body weight than the control(P<0.05). IOF HMB had no significant effect on feed conversion efficiency. 2) Broilers with IOF of HMB on day 18 of incubation had significantly higher breast muscle percentage than that of the control group at 3 d, 5 d and 42 d posthatch in broilers(P<0.05), breast muscle rate of broilers with IOF of HMB on day 7 of incubation was higher than that of the control group at 3 d and 42 d posthatch(P>0.05). For all groups, leg muscle percentage of broilers had no significant difference. 3) IOF of HMB significantly increased plasma growth hormone(GH) and insulinlike growth factor 1(IGF-1) content in prenatal and posthatch broilers(P<0.05), the influence of Triiodothyronine(T3), Thyroxine(T4) and insulin(INS) was not significant. 4) IOF of HMB can significantly improve the GH receptor(ghr) mRNA expression of breast muscle at hatch, 21 and 42 d posthatch of broilers(P<0.05) and significantly improve breast muscle IGF-1 receptor(igf-1r) mRNA expression at hatch(P<0.05). Hence, IOF of HMB can speed up growth in the early period of broilers,increase GH and IGF-1 content in the blood circulation, thus promote the chicken muscle development.Experiment 3. Effects of In Ovo Feeding of HMB on Growth Performance, Satellite Cells Mitotic Activity and Myogenic Regulatory Factors mRNA Expression in BroilersA total of 720 fertile eggs from Arbor Acre breeder were allotted into 3 treatments with 6 replicates and 40 eggs in each replicate. HMB(1 mL, 0.1%) was injected into the air cell on day 7 of incubation and into the amnion of embryos on day 18 of incubation, a control group without injection was also included. After hatching, 96 male chicks from each treatment were divided into 6 replicates with 16 birds. The results showed that: 1) IOF of HMB increased hatchability by 4.34%(P<0.05) and 3.34%(P>0.05). At hatching, broilers in both IOF-HMB groups had greater BW than those in control group(P<0.01). 2) Compared with the control group, IOF of HMB significantly increased the breast muscle percentage at 5, 7 and 21 d posthatch in broilers(P<0.05). 3) IOF of HMB increased the myofiber diameterat of skeletal muscle 3 and 5 d posthatch(P<0.05). Compared with the control group, broilers with IOF of HMB on 7 d of incubation had significantly graeter myofiber diameterat of skeletal muscle(P=0.039). 4) At hatch and 7 d posthatch, HMB group of skeletal muscle satellite cells mitotic activity index were significantly higher than of control group(P<0.05). 5) At hatch and 3 d posthatch, MyoD mRNA expression of breast muscle were significantly increased in IOF of HMB groups(P<0.05) and at3 and 5 d posthatch, broilers with IOF of HMB had significantly higher MyoG mRNA expression of breast muscle than that in the control group(P<0.05). Together, IOF of HMB can improve the hatchability, promote BW at hatch, speed up growth in the early period, increase muscle satellite cells mitotic activity index, thus promote the chicken muscle development, IOF of HMB does not affect feed conversion efficiency of broilers.In summary, IOF of HMB increased the performance and breast muscle yield of broilers by activating the GH/IGF-1 axis, improving GH and IGF-1 contention and breast muscle ghr and igf-1r mRNA expression. IOF of HMB promoted the differentiation and proliferation of satellite cells,improve broiler breast growth ultimately. IOF can be used as an effective method of early nutritional regulation of broilers. IOF of HMB via air cell partially improved the hatchability of broilers. |
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