JOURNAL OF ANIMAL AND VETERINARY ADVANCES, vol.12, no.1, pp.42-47, 2013 (SCI-Expanded)
The aim of this study was to determine effects of heat stress on egg production and quality characteristics, revealed THI distribution among cage blocks. Ambient dry bulb temperature and relative humidity measurements were recorded for cages and all of layer house in 31 days during July and August. The egg production in selected cages was recorded daily in this study. To determine egg weight, shape index, shell thickness, albumen index, yolk index and Haugh units scores, 30 eggs were collected daily from selected each cages. For indoor temperatures and relative humidity, average values were obtained as 31.15 degrees C and 44.68%, respectively. The average outdoor temperature and relative humidity were about 34.11 degrees C and 59.91%, respectively during study period in region conditions. The differences between cage rows, cage tiers and direction were not statistically significant for THI value (p>0.05). When the THI values increased from 25-29, heat stress reduced egg production by 25%. The converse effect of heat stress was most likely mediated through a reduction in feed consumption, reducing the available nutrients for egg production. Based on results of statistical analysis, variation on egg quality characteristics versus THI values is not statistically significant for whole study period.