ABSTRACT

1. The effects of housing system and stocking density on growth performance and carcase yield of a commercial strain of broiler chickens reared under tropical environmental conditions may differ from temperate conditions.

2. In two experimental periods, carried out during two contrasting seasons of the year (winter and summer), 240 Cobb 500 male chickens were randomly assigned in groups of 60 to 1 of 4 treatments, with 6 replicates in each, low stocking density with outdoor access (LO, 5 birds/m²); high stocking density with outdoor access (HO, 10 birds/m²); low stocking density indoors (LI, 5 birds/m²); high stocking density indoors (HI, 10 birds/m²). From 21 to 42 d old, body weight (BW) and feed intake (FI) were weekly recorded. Mortality was measured daily and carcase weight at slaughter. Indoor and outdoor temperature and relative humidity were measured daily.

3. There was a tendency for chickens raised in the outdoor access to be heavier than those raised in the indoor treatments. Chickens raised in the low-density treatments in the first experimental period were significantly heavier, gained more weight and had lower value for feed conversion ratio (FCR) than those reared at high density. In the second experimental period mortality significantly increased on week 4 due to heat stress. Birds raised with outdoor access had an increased carcase yield compared to those raised exclusively indoors.

4. In conclusion, low stocking density in combination with low environmental temperatures had enhancing effects on BW, BWG, FI and FCR, and the effects of housing system depended on stocking density. Low stocking density and outdoor access had positive effects on carcase yield.

摘要

1. 饲养系统和放养密度对热带环境条件下饲养的商品肉鸡生长性能和胴体产量的影响可能与温带条件不同。

2. 在一年中两个对比季节（冬季和夏季）进行的两个试验期中，240 只 Cobb 500 雄性鸡被随机分配到 4 个处理中的 60 到 1 个组中，每组 6 个重复，放养密度低，室外通道（LO，5 只鸟/m ²）；具有室外通道的高放养密度（H2O，10 只/m ²）；室内放养密度低（LI，5 只/m ²）；室内放养密度高（HI，10 只/m ²）。从 21 到 42 日龄，每周记录体重 (BW) 和采食量 (FI)。每天测量死亡率和屠宰时的胴体重量。每天测量室内外温度和相对湿度。

3.室外饲养的鸡有比室内饲养的重的趋势。与高密度饲养的鸡相比，在第一个试验期低密度饲养的鸡明显更重，体重增加更多，饲料转化率（FCR）值更低。在第二个实验期，由于热应激，第 4 周死亡率显着增加。与仅在室内饲养的鸟类相比，在室外饲养的鸟类的胴体产量增加。

4. 总之，低放养密度和低环境温度对BW、BWG、FI和FCR有增强作用，而鸡舍系统的影响取决于放养密度。低放养密度和室外通道对胴体产量有积极影响。