Physiological response of Nigerian locally adapted chickens with different heat shock protein 70 genotypes to acute heat stress

Abstract

Slow growth rate and acute heat stress are among the major constraints to indigenous chicken production in Nigeria. Characterization of heattolerance genes is a requisite for selective breeding of poultry for improved heattolerance and productivity. Therefore, this study investigated variation in HSP70 gene and its association with heat-tolerance traits of Nigerian locally adapted chickens. One-day old chicks comprising 118 Yoruba Ecotype Chicken-YEC and 138 FUNAAB Alpha Chicken-FAC were tagged and fed ad-libitum on starter (0 - 6 weeks) and grower (7-24 weeks) diets. At week 12, blood was sampled, DNA was extracted, amplified and electrophoresed following standard procedures. HSP70 gene was genotyped using MmeI restriction endonuclease. At week 23, 36 chickens (six chickens per identified HSP70 genotypes) selected from each of YEC and FAC were exposed to 40±1°C for one hour. Cloaca temperature, respiratory rate (RR) and pulse rate (PR) were recorded and heat stress index (HSI) calculated. Data were analysed using descriptive statistics and ANOVA. Alleles A and B with genotypes: AA, AB, and BB were detected. After acute heat-stress, YEC with BB had higher RR value compared to those with AA and AB. The PR value of FAC with genotype BB was significantly higher (p<0.05) than those of AA, but similar to chickens with AB. Within FAC, HSI of BB-HSP70 was lower than AA-HSP70 but similar to AB-HSP70, while within YEC HSI of BB-HSP70 was similar to those of AA-HSP70 and AB-HSP70. The HSP70 gene was polymorphic in the studied chickens and genotype BB-HSP70 was associated with thermo-tolerance.

Keywords

• indigenous chickens
• improved breed
• heat stress
• hsp70
• heat stress index
• pcr-rflp