低蛋白质饲粮对滩羊生长性能、消化代谢、屠宰性能及肉品质的影响

Effects of Low Protein Diet on Growth Performance,Digestion and Metabolism,Slaughter Performance and Meat Quality of Tan Sheep

本试验旨在研究低蛋白质饲粮对滩羊生长性能、消化代谢、屠宰性能及肉品质的影响。选择3月龄健康、体况相似、平均体重在(21.58±7.94)kg的滩羊36只,随机分为4组,每组3个重复,每个重复3只。对照组饲喂蛋白质水平为13%的饲粮,3个试验组分别饲喂比对照组饲粮蛋白质水平降低1%(试验Ⅰ组)、2%(试验Ⅱ组)和3%(试验Ⅲ组)的能氮平衡的饲粮。预试期10 d,正试期60 d。结果显示:1)滩羊的初始体重、终末体重以及干物质采食量各组间均无显著差异(P>0.05);对照组与试验Ⅰ组的平均日增重显著高于试验Ⅱ组与试验Ⅲ组(P<0.05);料重比以试验Ⅰ组最低,与对照组差异不显著(P>0.05),但显著低于试验Ⅱ组与试验Ⅲ组(P<0.05)。2)干物质、中性洗涤纤维和酸性洗涤纤维的表观消化率各组之间均无显著差异(P>0.05)。3)对照组的进食氮显著高于试验Ⅱ组和试验Ⅲ组(P<0.05),粪氮、尿氮显著高于试验Ⅰ组、试验Ⅱ组和试验Ⅲ组(P<0.05);然而,各组在沉积氮、氮消化率、氮利用率上的差异均不显著(P>0.05);相比之下,试验Ⅰ组、试验Ⅱ组和试验Ⅲ组的氮生物学价值分别较对照组提高2.13%(P<0.05)、1.54%(P>0.05)和0.54%(P>0.05)。4)饲喂低蛋白质饲粮对滩羊的宰前活重、头重、蹄重、骨重、骨肉比无显著影响(P>0.05),对GR值、眼肌面积、尾部脂肪重、胴体脂肪重也均无显著影响(P>0.05);胴体脂肪重随着饲粮蛋白质水平的降低而降低;此外,试验Ⅰ组的屠宰率相较对照组、试验Ⅱ组、试验Ⅲ组分别提高5.12%、10.32%、4.65%,但各组之间差异不显著(P>0.05)。5)饲喂低蛋白质饲粮对滩羊肉的pH45 min、失水率、剪切力、熟肉率、肉色的红度和黄度值、脂肪颜色以及大理石纹评分均没有显著影响(P>0.05);对照组的滴水损失率显著高于试验Ⅲ组(P<0.05);试验Ⅲ组的肉色亮度值显著高于对照组与试验Ⅰ组P<0.05)。6)各组滩羊肉中水分、粗灰分及粗脂肪含量均差异不显著(P>0.05);对照组与试验Ⅰ组滩羊肉中粗蛋白质含量显著高于试验Ⅲ组(P<0.05)。综上所述,在能氮平衡的基础上将饲粮蛋白质水平由13%降至12%,不仅可减少氮排放,且不会对滩羊的生长性能、消化代谢、屠宰性能及肉品质产生负面影响。

The objective of this experiment was to study the effects of low protein diet on the growth perform⁃ance,digestion and metabolism,slaughter performance and meat quality of Tan sheep.Thirty⁃six healthy 3⁃month⁃old Tan sheep,with similar body condition and average body weight of(21.58±7.94)kg,were selected and randomly split into four groups with three replicates and each replicate with three sheep.Sheep in control group were fed a diet with 13%protein,while those in trial groupsⅠ,ⅡandⅢwere fed diets with protein levels that were 1%,2%and 3%lower than that of control group diet based on the energy⁃nitrogen balance.The pre⁃feeding period was 10 d and the formal period was 60 d.The results were as follows:1)there were no significant differences in the initial body weight,final body weight and dry matter intake of Tan sheep among the four groups(P>0.05).The average daily gain of the control group and trial groupⅠwas significantly higher than that of trial groupsⅡandⅢ(P<0.05).The lowest feed to gain ratio was observed in the trial groupⅠ,which was not significantly different from that of control group(P>0.05),but significantly lower than that of trial groupsⅡandⅢ(P<0.05).2)There were no significant differences in the apparent digestibility of dry matter,neutral deter⁃gent fiber and acid detergent fiber of Tan sheep among the four groups(P>0.05).3)The nitrogen intake of the control group was significantly higher than that of the trial groupsⅡandⅢ(P<0.05),and the fecal nitrogen and urine nitrogen were significantly higher than those of the trial groupsⅠ,ⅡandⅢ(P<0.05),but no significant differences in the retention nitrogen,nitrogen digestibility and nitrogen utilization efficiency were observed a⁃mong four groups(P>0.05).In contrast,the biological value of nitrogen of the trial groupsⅠ,ⅡandⅢwas higher than that of control group,with an increase of 2.13%(P<0.05),1.54%(P>0.05)and 0.58%(P>0.05),respectively.4)Feeding low protein diets had no significant effects on live weight before slaughter,head weight,hoof weight,bone weight and bone/meat ratio(P>0.05),and had no significant effects on the GR val⁃ue,loin eye area,tail fat weight and carcass fat weight of Tan sheep(P>0.05).However,the carcass fat weight decreased correspondingly with the reduction of dietary protein level.The trial groupⅠhad a 5.12%,10.32%and 4.65%increase in slaughter rate compared with the control group and trial groupsⅡandⅢ,respectively,but the difference among groups was not significant(P>0.05).5)Feeding low protein diet had no significant effects on pH45 min,water loss rate,shear force,cooked meat rate,meat color redness and yellowness values,fat color and marbling score of Tan sheep(P>0.05).The drip loss of the control group was significantly higher than that of the trial groupⅢ(P<0.05).The meat color brightness value of trial groupⅢwas significantly higher than that of control group and trial groupⅠ(P<0.05).6)There were no significant differences among the groups in mois⁃ture,ash and ether extract contents of mutton for Tan sheep(P>0.05).The crude protein content of mutton for Tan sheep of the control group and the trial groupⅠwas significantly higher than that of the trial groupⅢ(P<0.05).In conclusion,based on the energy⁃nitrogen balance,dietary protein level is decreased from 13%to 12%,it can not only reduce nitrogen emission,but also have no negative effects on the growth performance,di⁃gestive and metabolism,slaughter performance and meat quality of Tan sheep.