อิทธิพลของความเครียดเนื่องจากความร้อนต่อค่าพารามิเตอร์ทางพันธุกรรม และผลผลิตไข่ในไก่พื้นเมืองไทยพันธุ์ประดู่หางดำ

Abstract

The study of the effects of heat stress on genetic parameters and egg production; and the investigation of the threshold point of heat stress in Pradu Hang Dam Thai native chickens were significant in the planning of genetic improvement and management. Data included 7,752 monthly egg production records of 672 Thai native chickens from the first to the fourth generation between September 2007 and April 2011. Data were obtained from the Research and Development Network Center for Animal Breeding (Native Chicken), Faculty of Agriculture, Khon Kaen University. Variance components and genetic parameters were estimated by the Expectation Maximization Restricted Maximum Likelihood (EM-REML) under the repeated test-day model. The results found that monthly egg production of Pradu Hang Dam Thai native chickens continuously declined from March (average THI = 78.3) until September (average THI = 78.0). This was associated with the summer and rainy seasons of Thailand. Meanwhile, from October to February (average THI = 70.5), monthly egg production increased. In addition, at the THI threshold point, the average egg production declined by 0.16 egg/bird. Heritability for monthly egg production was 0.23, while the estimation of genetic correlation between monthly egg production and heat stress effect was -0.29. The results indicated that, if the heat stress was severe, monthly egg production genetics would decline.