Effects of air velocity on laying hen production from 24 to 27 weeks under simulated evaporatively cooled conditions.

摘要

Thermal conditions play a major role in production efficiency in commercial poultry production. Mitigation of thermal stress can improve productivity, but it must be achieved economically. Weather and system design can limit the effectiveness of evaporative cooling, and increased air movement has been shown to improve production efficiency in broilers. The objective of this study was to evaluate the effects of varied levels of air velocity on the productivity of laying hens housed under evaporatively cooled conditions by assessing hen-day egg production (HDEP), feed consumption (FC), feed consumption per dozen eggs (FD), feed conversion ratio (FCR), and egg weight (EW). Three treatments were tested (still air, constant 0.76 m s-1, and constant 1.52 m s-1) at 27.8 degrees C and 82% RH to mimic an evaporatively cooled poultry house in the southeastern U.S. under summer weather conditions. Air velocity test units (wind tunnels) containing cages were constructed; still air treatment groups were housed in identical cage units without the surrounding wind tunnel structure. Four trials were conducted, with two replicate treatment groups per trial, for a total of eight replicate treatment groups in the study. Hens (Hy-Line W-36 variety) were obtained from a commercial laying operation for each trial at 23 weeks of age and housed in an adjacent facility until transfer into the test cages; 48 hens were used in each trial, with eight hens per replicate treatment group, for a total of 192 hens in the study. Feed and water were provided ad libitum, and the lighting program followed primary breeder (Hy-Line) recommendations. Eggs were collected and group weighed for each treatment group for 28 days, and feed consumption was assessed weekly. Results showed that HDEP for the 1.52 m s-1 treatment group improved by 3.8% and 3.3% over still air and 0.76 m s-1, respectively. FC was observed to increase with air velocity (p<=0.05). FD increased with increasing air velocity and was significantly greater (p=0.0043) for both air velocity treatments compared to still air. Other measures of performance including EW and FCR were not different, suggesting that the improvement in HDEP resulted from increased FC. Increased convective cooling increases productivity of laying hens during hot weather by improving thermal comfort when evaporative cooling is limited by weather or system design.