不同锌源及添加水平对肉仔鸡生长性能的影响及其生物学利用率评价

本试验旨在研究碱式氯化锌(BZC)和蛋白锌(PRZ)相对于一水合硫酸锌(ZSM)的生物学利用率以及对肉仔鸡生长性能的影响。采用双因素(3×3+1)完全随机试验设计,选取720只1日龄健康雄性爱拔益加(AA)肉仔鸡,随机分为10个组,每组6个重复,每个重复12只鸡。对照组饲喂玉米-豆粕型基础饲粮,3个ZSM组分别饲喂在基础饲粮基础上添加20、40和80 mg/kg ZSM的饲粮,3个BZC组分别饲喂在基础饲粮基础上添加20、40和80 mg/kg BZC的饲粮,3个PRZ组分别饲喂在基础饲粮基础上添加20、40和80 mg/kg PRZ的饲粮。各组不同锌源添加量均以锌计。试验期42 d,分为1~14日龄、15~28日龄和29~42日龄3个阶段。分别在14和28日龄时,从各重复中选取1只接近平均体重的鸡进行屠宰,测定血浆锌含量和抗氧化指标、组织锌含量以及胰脏锌相关蛋白基因表达水平。结果表明:1)1~14日龄,与对照组相比,饲粮添加不同锌源和添加不同水平锌显著提高肉仔鸡平均日增重(ADG)和14日龄体重(P<0.05),显著降低料重比(F/G)(P<0.05),且以添加40 mg/kg BZC效果最佳;在不同锌源之间,BZC组ADG显著高于ZSM组和PRZ组(P<0.05),F/G显著低于ZSM组(P<0.05)。2)随着饲粮锌添加水平的提高,肉仔鸡14日龄血浆锌含量和14和28日龄胫骨锌含量显著提高(P<0.05);14日龄,BZC组血浆碱性磷酸酶(ALP)活性显著高于ZSM组(P<0.05),PRZ组血浆总超氧化物歧化酶(T-SOD)和铜锌超氧化物歧化酶(CuZn-SOD)活性显著高于ZSM组和BZC组(P<0.05)。3)与对照组相比,饲粮添加不同锌源和添加不同水平锌显著提高14日龄肉仔鸡胰脏金属硫蛋白(MT)mRNA表达量(P<0.05);且PRZ组14日龄胰脏MT mRNA表达量显著高于ZSM组和BZC组(P<0.05),PRZ组28日龄胰脏MT mRNA表达量显著高于ZSM组(P<0.05)。4)采用斜率比法,以ZSM生物学利用率为参照标准(100.00%),选择1~14日龄ADG、F/G和14日龄血浆ALP活性作为评价指标,BZC的相对生物学利用率分别为110.82%、113.55%和113.26%,PRZ的相对生物学利用率为102.90%、113.38%和109.64%;而以血浆T-SOD、CuZn-SOD活性和胰脏MT mRNA表达量作为评价指标,BZC的相对生物学利用率分别为98.90%、 111.58%和107.87%, PRZ的相对生物学利用率分别为113.86%、 96.56%和130.56%。综上所述,BZC对提高肉仔鸡生长性能的效果和相对生物学利用率优于ZSM,甚至达到RPZ的效果。

Effects of Different Zinc Sources and Supplemental Levels on Growth Performance of Broilers and Their Bioavailability Evaluation

This experiment was conducted to investigate the bioavailability of basic zinc chloride(BZC)and protein zinc(PRZ)relative to zinc sulfate monohydrate(ZSM)and the effects on growth performance of broilers. A total of 720 healthy male Arbor Acres(AA)broilers of one-day-old were randomly divided into 10 groups with 6 replicates per group and 12 broilers per replicate in a two-factor(3×3+1)completely randomized trial design. Broilers in the control group were fed a corn-soybean meal basal diet,those in the three ZSM groups were fed the basal diet supplemented with 20,40 and 80 mg/kg ZSM,those in the three BZC groups were fed the basal diet supplemented with 20,40 and 80 mg/kg BZC,and those in the three PRZ groups were fed the basal diet supplemented with 20,40 and 80 mg/kg PRZ,respectively. The contents of different dietary zinc sources in each group were calculated by zinc. The experiment lasted for 42 days and was divided into 3 stages of 1 to 14 days of age,15 to 28 days of age and 29 to 42 days of age. At 14 and 28 days of age,one chicken with average body weight was selected from each replicate and slaughtered to determine zinc content and antioxidant indices in plasma,zinc content in tissues and zinc related protein gene expression levels in pancreas. The results showed as follows:1)from 1 to 14 days of age,compared with the control group,the supplementation of different zinc sources and different levels of zinc significantly increased the average daily gain(ADG)and body weight at 14 days of age of broilers(P<0.05),and significantly decreased the ratio of feed to gain(F/G)(P<0.05),in which the supplementation of 40 mg/kg BZC had the best effect. Among different zinc sources,ADG in BZC group was significantly higher than that in ZSM group and PRZ group(P<0.05),and F/G was significantly lower than that in ZSM group(P<0.05). 2)With the increase of dietary zinc supplemental level,the plasma zinc content of broilers at 14 days of age and tibia zinc content at 14 and28 days of age were significantly increased(P <0.05). At 14 days of age,the plasma alkaline phosphatase(ALP)activity in BZC group was significantly higher than that in ZSM group(P<0.05),and the plasma activities of total superoxide dismutase(T-SOD)and copper and zinc superoxide dismutase(CuZn-SOD)in PRZ group were significantly higher than those in ZSM group and BZC group(P<0.05). 3)Compared with the control group,the supplementation of different zinc sources and different levels of zinc significantly increased the metallothionein(MT)mRNA expression level in pancreas of broilers at 14 days of age(P<0.05).The MT mRNA expression level in pancreas in PRZ group at 14 days of age was significantly higher than that in ZSM group and BZC group(P<0.05),and that in PRZ group at 28 days of age was significantly higher than that in ZSM group(P<0.05). 4)Adopting slope ratio method,using ZSM bioavailability as reference standard(100.00%)and selecting ADG and F/G from 1 to 14 days of age and plasma ALP activity as evaluation indices,the relative bioavailability of BZC was 110.82%,113.55% and 113.26%,and the relative bioavailability of PRZ was 102.90%,113.38% and 109.64%,respectively;using plasma activities of T-SOD and CuZn-SOD and MT mRNA expression level in pancreas as evaluation indices,the relative bioavailability of BZC was 98.90%,111.58% and 107.87%,and the relative bioavailability of PRZ was 113.86%,96.56%and 130.56%,respectively. In conclusion,the effects of BZC on improving growth performance of broilers and relative bioavailability are better than those of ZSM,and even reach the effects of RPZ.Chinese Journal of Animal Nutrition,2022,34(2):924-938]