Deeb N, Cahaner A
The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot, Israel.
Poult Sci. 2002 Mar;81(3):293-301. doi: 10.1093/ps/81.3.293.
One cycle of high-intensity selection on BW was conducted to study correlated effects on performance under high ambient temperature (AT). From a large flock of a commercial sire-line, 3 males and 15 females with the highest BW at 35 d of age were mated and produced a group of 120 BW-selected chicks. Three average-BW males and 15 average-BW females from the same flock were mated to produce a control group of 120 chicks. On Day 17, the two groups were equally divided between two temperature-controlled chambers and housed in individual cages. One chamber was set to a normal AT (NAT; constant 22 C) and the second chamber to high AT (HAT; constant 32 C). Under NAT, the relative advantage of the selected broilers over the controls did not change from 17 to 42 d of age, averaging about 15% for BW gain and 9.7% for feed consumption. These differences were halved under HAT from Days 17 to 28 and were reversed from 28 to 42 d of age, when the selected broilers consumed significantly less feed and gained less BW than the controls. Water-to-feed ratio was measured in each AT treatment. From 28 to 42 d of age, averaged over the two groups, birds under HAT consumed 2.5 g water/g of feed compared to only 1.5 g water/g feed under NAT. The diminished superiority of the selected broilers under HAT led to a substantial genotype-by-environment interaction involving high AT and within-stock genetic differences in growth rate. It appears that broilers selected for rapid growth under optimal conditions do not achieve their genetic potential under high AT. Thus, specific indicators of adaptation to heat, possibly water consumption or body temperature, should be added to commercial selection for rapid growth to improve broiler performance in hot climates.
进行了一轮关于体重（BW）的高强度选择，以研究在高环境温度（AT）下对生产性能的相关影响。从一个大型商业父系鸡群中，挑选出35日龄时体重最高的3只雄性和15只雌性进行交配，产生了一组120只经体重选择的雏鸡。从同一鸡群中挑选出3只平均体重的雄性和15只平均体重的雌性进行交配，产生了一个由120只雏鸡组成的对照组。在第17天，将两组雏鸡平均分配到两个温度控制的鸡舍中，饲养在单独的笼子里。一个鸡舍设置为正常环境温度（NAT；恒定22℃），另一个鸡舍设置为高环境温度（HAT；恒定32℃）。在NAT条件下，从17日龄到42日龄，所选肉鸡相对于对照组的相对优势没有变化，体重增加平均约为15%，饲料消耗平均约为9.7%。在HAT条件下，从第17天到第28天，这些差异减半，从第28天到第42天则相反，此时所选肉鸡的饲料消耗量和体重增加量均显著低于对照组。在每种环境温度处理中都测量了水料比。从第2日龄到第42天，两组的平均值显示，HAT条件下的鸡每克饲料消耗2.5克水，而NAT条件下仅为每克饲料消耗1.5克水。所选肉鸡在HAT条件下优势的减弱导致了显著的基因型与环境互作，涉及高环境温度和鸡群内生长速度的遗传差异。似乎在最佳条件下选择快速生长的肉鸡在高环境温度下无法发挥其遗传潜力。因此，在商业快速生长选择中应增加适应热的特定指标，可能是水消耗量或体温，以提高肉鸡在炎热气候下的生产性能。
