Réponse à la chaleur de poules pondeuses issues de lignées sélectionnées pour une faible (R - ) ou forte (R + ) consommation alimentaire résiduelle

Abstract

Effects of temperature on egg laying hens from divergent lines selected on residual feed consumption. A sample of females from the 19th generation of the ’R-’ I and ‘R+’ lines divergently selected for the residual feed intake in the laying period was separated at 18 weeks of age in climatic rooms into two groups, one kept at a constant temperature of 21 +/- 1 °C (control), the other kept at 31 +/- 1 °C (’heated’ group). Egg production was recorded until the age of 45 weeks, individual feed consumption was measured between the ages of 31 and 35 weeks, and water consumption was measured at 51 weeks. The usual effects of high ambient temperature compared to moderate temperature were observed in both lines: reduction of food intake (- 16%), egg number and egg mass (- 13%), mean clutch length, more days of pauses, depression of body weight (- 8%) and mean egg weight (- 4%). Similarly, over both treatments, the differences found previously between lines in total feed consumption (25%) and in its residual part (19%), in comb and wattle size, shank length and in water intake (51%) were observed. However, for several variables the line x treatment interaction was significant, especially for residual food intake, water intake, 48-week body weight and adult body weight variation, indicating that the ’overconsuming line’ (R+) was better adapted to the high temperature with a reduction in egg number of only 10% versus 22% for the ’underconsuming’ line (R-). The better adaptation of the R+ line may be due partly to a reduction of thermogenesis during feeding, and perhaps more probably to a higher capacity for heat dissipation. Finally, breeding for a laying hen with better food efficiency, which has been found to be advantageous in a temperate environment, shows some limits at high temperature.