Genotype-by-environment interaction with broiler genotypes differing in growth rate. 2. The effects of high ambient temperature on dwarf versus normal broilers. Poultry Sci

ABSTRACT One cycle of high-intensity selection on BW was conducted to study correlated effects on perfor-mance under high ambient temperature (AT). From a large flock of a commercial sire-line, 3 males and 15 fe-males 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 (Key words: selection, ambient temperature, water consumption, body temperature, weight gain