Yunis R, Cahaner A
Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot, Israel.
Poult Sci. 1999 Oct;78(10):1347-52. doi: 10.1093/ps/78.10.1347.
High ambient temperatures (AT) decrease the growth of broilers because of difficulty in dissipating heat through the feather coverage. Broilers selected for higher growth rate eat more and generate more heat per unit of time; hence, they may become more sensitive to high AT. Reduced feather coverage, either by decreased number or by modified shape, may help birds to dissipate internal heat more efficiently. Two broiler stocks were studied; each was segregated for four genotypes with regard to the genes for naked neck (Na) and frizzled feathers (F): heterozygous naked neck (Na/na f/f), heterozygous frizzle (na/na F/f), double heterozygous (Na/na F/f), and normally feathered (na/na f/f). One stock had a high growth rate (GR) similar to current commercial broilers, whereas the second stock had a lower GR. Birds of each stock, genotype, and sex were reared under constant standard AT (24 C) or high AT (32 C). Body weight at 4 and 7 wk, weight gain (WG) from 4 to 7 wk, breast meat yield, and feather weight were recorded. Reduction in WG from 4 to 7 wk because of high AT was greater in high-GR birds than in low-GR birds, but, in both stocks, the high AT effect was greater on normally feathered birds than on the other three genotypes. AT 32 C, in low- and high-GR stocks, the F allele increased WG from 4 to 7 wk and increased the BW at 7 wk of fully feathered (na/na) broilers but had no effect on meat yield. The effects of the Na allele were similar to or greater than those of the F allele. The Na allele did not affect breast meat yield of low-GR broilers but increased it significantly in high-GR broilers. Combining the two allles resulted in an additive effect, which was more pronounced in the high-GR stock.
由于通过羽毛覆盖散热困难，高环境温度（AT）会降低肉鸡的生长速度。选择生长速度较快的肉鸡每单位时间进食更多且产生更多热量；因此，它们可能对高环境温度更为敏感。羽毛覆盖减少，无论是数量减少还是形状改变，都可能有助于鸡更有效地散发体内热量。研究了两个肉鸡群体；每个群体根据裸颈（Na）和卷羽（F）基因分为四种基因型：杂合裸颈（Na/na f/f）、杂合卷羽（na/na F/f）、双杂合（Na/na F/f）和正常羽毛（na/na f/f）。一个群体具有与当前商业肉鸡相似的高生长速度（GR），而第二个群体的生长速度较低。每个群体、基因型和性别的鸡在恒定的标准环境温度（24℃）或高环境温度（32℃）下饲养。记录4周和7周时的体重、4至7周的体重增加（WG）、胸肉产量和羽毛重量。高环境温度导致4至7周的WG减少，高生长速度的鸡比低生长速度的鸡更明显，但在两个群体中，高环境温度对正常羽毛的鸡的影响比对其他三种基因型的鸡更大。在32℃时，在低生长速度和高生长速度群体中，F等位基因增加了4至7周的WG，并增加了7周时全羽（na/na）肉鸡的体重，但对肉产量没有影响。Na等位基因的影响与F等位基因相似或更大。Na等位基因对低生长速度肉鸡的胸肉产量没有影响，但在高生长速度肉鸡中显著增加。两个等位基因结合产生加性效应，在高生长速度群体中更明显。
