Evaluation of environmental temperature in pullet weight gain and uniformity

There is still a deficit of conclusive answers about what is the appropriate thermal environment for pullets. So far, tropical countries have worked with thermal ranges recommended by the international genetic improvement companies. However, it is likely that pullets raised in a tropical climate have adapted to higher temperatures. The growing phase is important for the body development of pullets. During this period, the greatest development of muscles and bones occur. Therefore, it is important to avoid thermal stress before pullets start laying so they can develop appropriate body structure for egg production. The objective of this study was to evaluate the effect of thermal environments on pullet weight and uniformity during the growing phase. The research was conducted with 140 pullets (Lohmann LSL Lite). From day 1 through 6 weeks of age, birds were reared with standard temperature and humidity according to their age and the Lohmann production manual. At the 7th week, the pullets were submitted to one of four thermal environments, Thermal Comfort (20ºC) (TC), Mild Heat Stress (25°C) (MiHs); Moderate Heat Stress (30°C) (MoHs); Severe Heat Stress (35°C) (SeHs). During the night period pullets in all thermal environments were subjected to thermal comfort, from 7:00 p.m. to 7:00 a.m. Pullets were individually weighed weekly. There was a significant difference in body weight between treatments (P<0.05). Pullets in the SeHs had reduced body weight compared to those exposed to TC and MiHs (P<0.05). The uniformity was higher for pullets in SeHs. Mortality was not different between temperatures tested.