May J D, Reece F N
Poult Sci. 1986 Apr;65(4):801-6. doi: 10.3382/ps.0650801.
Broilers, obtained from a commercial hatchery, were reared in two environmental chambers with controlled temperature, humidity, and lighting in three trials. Lighting was continuous for 0 to 7 days and 12L:12D thereafter. Temperatures, initially 32.2 C in Trials 1 and 3 and 29.4 in Trial 2, were gradually lowered during rearing. At the end of the trials, temperatures were 21.1, 10.0, and 23.9 C in Trials 1, 2, and 3, respectively. Feed and water were provided ad libitum until 21 days in Trials 1 and 3 and 28 days in Trial 2. During the subsequent 14 days in each trial, feed was provided 12 hr/day with one chamber receiving feed during photophase (LF) and the other receiving feed during scotophase (DF). Plasma samples for 3,5,3'-triiodothyronine (T3) and thyroxine (T4) assay were obtained at 3-hr intervals throughout a 24-hr period at the end of the 14-day treatment period. During the 14-day treatment period, the weight gain of the DF broilers averaged 90% of the LF broilers for the three trials. This demonstrates broilers adapted very well to feeding during scotophase. The T4/T3 ratio increased during fasting and decreased when feed was available, but photoperiod had no discernible effect. The change in T4/T3 ratio over 24 hr was greater at high than at low environmental temperatures.
从一家商业孵化场获取的肉鸡，在三个试验中饲养于两个温度、湿度和光照可控的环境舱内。0至7日龄时光照为持续光照，之后为12小时光照：12小时黑暗。试验1和3最初温度为32.2℃，试验2最初温度为29.4℃，饲养期间温度逐渐降低。试验结束时，试验1、2和3的温度分别为21.1℃、10.0℃和23.9℃。试验1和3中，自由采食和饮水至21日龄，试验2中至28日龄。在每个试验随后的14天里，每天提供12小时饲料，一个舱在光照期（LF）喂食，另一个舱在黑暗期（DF）喂食。在14天处理期结束后的24小时内，每隔3小时采集血浆样本用于检测三碘甲状腺原氨酸（T3）和甲状腺素（T4）。在14天处理期内，三个试验中DF组肉鸡的体重增加平均为LF组的90%。这表明肉鸡非常适应在黑暗期进食。禁食期间T4/T3比值升高，有饲料供应时降低，但光周期没有明显影响。在高环境温度下，24小时内T4/T3比值的变化比低环境温度下更大。
