肉鸡体重对净能评定中总产热量和绝食产热量的影响

Effects of Body Weight on Total Heat Production and Fasting Heat Production in Net Energy Evaluation of Broilers

本试验旨在通过开放式呼吸测热装置研究4～7周龄阶段肉鸡体重对其采食过程中的总产热量、绝食产热量和绝食时间的影响。试验采用单因子试验设计，选用4～7周龄爱拔益加（ AA）肉鸡48只，每周第1天选择体重相近的肉公鸡12只为1组，分为A、B、C、D 4组（每组6个重复，每个重复2只鸡），每组为1个试验阶段。将同一组12只肉鸡随机放入6个呼吸测热室中。第1天适应小室环境，从第2天开始连续测定3 d采食过程的总产热量。从第5天09：00喂料后开始绝食，以12 h作为1个时间单位连续测定72 h的绝食产热量。结果表明：1）绝食12～36 h，各组肉鸡耗氧量、二氧化碳生成量和绝食产热量逐渐降低，A和C组肉鸡绝食到12和24 h时差异不显著（ P＞0．05），但显著高于绝食到36 h（ P＜0．05）；C和D组肉鸡绝食到12、24和36 h时差异显著（ P＜0．05）；A组肉鸡绝食到48和72 h时差异不显著（ P＞0．05），绝食到60 h时显著低于绝食到48和72 h（P＜0．05）；B组肉鸡绝食到36、48和72 h时逐渐降低，但差异不显著（P＞0．05），绝食到60 h时低于绝食到72 h，差异不显著（P＞0．05），但显著低于绝食到48 h （ P＜0．05）；C和D组肉鸡绝食到48 h以后趋于平稳，差异不显著（ P＞0．05），与绝食到36 h以前差异显著（ P＜0．05）。绝食12～72 h，不同体重肉鸡的呼吸熵处于0．65～0．75之间。相同绝食时间下不同体重肉鸡之间呼吸熵无明显规律。2）绝食产热量的对数（ y）与体重的对数（ x）的线性回归方程为y＝0．737x-0．332（ R2＝0．99，P＜0．01）。3）不同周龄肉鸡绝食到48 h时的每千克代谢体重日产热量差异不显著（P＞0．05），与由线性回归方程得到的0．47 MJ/（kg BW0．74·d）相近。4）4～7周龄阶段肉鸡耗氧量、二氧化碳生成量、总产热量和绝食产热量随不同周龄体重的增加显著提高（ P＜0．05）。综上，4～7周龄阶段的肉鸡适宜的绝食时间为48 h，单位代谢体重（BWb）的系数为0．74，绝食产热量为0．47 MJ/（kg BW0．74·d），体重对4～7周龄阶段肉鸡总产热量、绝食产热量和绝食代谢时间影响显著。

This experiment was investigated to study the effects of body weight（ BW）on total heat production （ THP）,fasting heat production（ FHP）and fasting duration of broilers at 4 to 7 weeks of age by a patented open-circuit respiratory calorimetry equipment. A single factor randomized design had been taken,a total of 48 male Arbor Acre broilers at 4 to 7 weeks of age were selected,on the first day of each week,12 birds with similar BW were assigned to 1 group,those birds were divided into 4 groups（ 6 replicates in each group and 2 birds in each replicate）：groups A,B,C and D,and each group was one experimental period. One group of 12 broilers was randomly sent into 6 same respiratory chambers for energy metabolism test. For the tested birds,after a 1-day adaptation period,3 days THP for feeding and another 3 days for fasting were recorded. After the broilers fed in the fifth day of nine o’clock,another 72 h for fasting was recorded and every 12 h was a statistical unit. The results showed as follows：1）during fasting 12 to 36 h,the O2 consumption,CO2 production and FHP in each group were gradually decreased,those indexes in groups A and C were not differ-ent after fasting 12 and 24 h（ P〉0.05）,but were significantly higher than fasting 36 h（ P〈0.05）,and those indexes in groups C and D were sharply decreased after fasting 12,24 and 36 h（ P〈0.05）. Those indexes in group A were not different after fasting 48 and 72 h（ P〉0.05）,but were significantly decreased after fasting 60 h（ P〈0.05）. Those indexes in group B were gradually decreased after fasting 36,48 and 72 h（ P〉0.05）, but were sharply decreased after fasting 60 h（ P〈0.05）. Those indexes in groups C and D were not different after fasting 48 h（ P〉0.05）,but were significantly different before fasting 36 h（ P〈0.05）. During fasting 12 to 72 h,the respiration quotient（RQ）of broilers were 0.65 to 0.75. There was no significant profile in RQ between different BW broilers during the same fasting duration. 2）The linear regression model of lgFHP（ y） and lgBW（x）was y=0.737x-0.332（R2=0.99,P〈0.01）. 3）The FHP of metabolic BW in each group were not different after fasting 48 h（ P〉0.05）and were close to 0.47 MJ/（ kg BW0.74 ·d）calculated from re-gression equation. 4）With the BW growing,the O2 consumption,CO2 production,THP and FHP of broilers at 4 to 7 weeks of age were significantly increased（ P〈0.05）. It is concluded that a fasting of 48 h is suitable for broilers’net energy measurement at 4 to 7 weeks of age. The linear regression model shows that the expo-nential coefficient of metabolic BW is 0.74 and the FHP is 0.47 MJ/（ kg BW0.74 ·d）. The BW has a signifi-cant effect on THP,FHP and fasting duration of AA broilers at 4 to 7 weeks of age.