Identifikasi keragaman gen penyandi tahan panas (Heat Shock Protein 70) ayam lokal serta respon fisiologisnya terhadap cekaman panas akut

Abstract

This study was designed to obtain HSP 70 genotypes of chickens which were tolerant to high ambient temperature or heat stress, while the specific objectives were: 1) To examine the HSP 70 gene polymorphism in local, Arabic, and commercial chickens, 2) To examine the genotype effect of local, arabic, and commercial chickens on their adaptability to the high environmental temperature. The study used 96 blood samples from local chicken, 94 samples from Arabic chickens, and 87 samples from commercial chickens which were taken from the brachial vein at the age of 12 weeks. Day old Kampong chickens were obtained by hatching the eggs that were collected from lowlands, medium, and high altitude areas in Lombok Island, while the day old Arabic chickens were obtained from local farmer. Day old commercial chickens were purchased from the local poultry shop. Each genotype from each chicken classes wasrepresented by 4 chickens to be challenged to heat stress at 40oC, one chicken as a control (was not exposed to given heat to heat stress), one chicken was exposed to heat stress for 0.5, 1, and 1.5 hours, respectively. The genotyping results by using PCR-SSCP analysis showed that kampong and Arabic chickens were polymorphic, while commercial chickens were classified as monomorphic. Kampong chickens had seven genotypes of HSP 70, namely AA, AB, AC, CC, AD, DD, and BC. The AD genotypes and A allele had the highest frequency in kampong chickens. Arabic chickens had six genotypes, namely AA, AB, AC, CC, AD, and BC, which AC genotype and A allele had the highest frequencies. However, the commercial chickens had only one genotype, namely DD. Seven were polymorphic sites found in applicated area, namely AG mutation at site 617, AG mutation at sites 628 and G C mutation at site 646, mutation CT at sites 661 and AG mutation at site 699, mutation GC at site 754, and AG mutation at site 792. Mutation at site 628, 646 and 661 were considered as silent mutation. HSP 70 gene in kampong and arabic chickens population in this study were in equilibrium. The values of Ho, He, and PIC of kampong and Arabic chickens were not significant. The chicken breeds (local, arabic and commercial chickens) affected the panting frequency, feces water content, and the blood hematocrit values as well, but did not affect the onset of panting, drinking water consumption, feed consumption, rectal temperature, HSP 70 expression, the serum corticosterone concentration, erythrocytes concentration, hemoglobin, leucocyte concentration, heterophils, basophils, lymphocytes, monocytes, eosinophil, and the H/L ratio. Acute heat stress caused an increase in the panting frequency, drinking water consumption, rectal temperature, feces water content, the expression of HSP 70, the serum corticosterone concentration, the heterophils, basophils, and the H/L ratio, and decreased feed intake, erythrocytes, hemoglobin, hematocrit value, leucocyte, lymphocytes, and monocytes percentages. Heat stress treatment did not affect the percentage of eosinophils. Long-term heat stress did not affect the onset of panting, drinking water consumption, feed consumption, rectal temperature, feces water content, serum corticosterone concentration, erythrocytes concentration, hemoglobin, hematocrit values, leucocyte concentration, and heterophils, eosinophils, basophils, lymphocytes, monocytes percentage. However, long-term heat stress increased the frequency of panting and HSP 70 expression. In this study, the interaction between the chicken types and the duration of heat stress was significant on water consumption and feces water content, but did not affect panting frequency, the onset of panting, feed consumption, rectal temperature, HSP 70 expression, serum corticosterone concentration, erythrocyte concentration, hemoglobin, hematocrit values, leokocyite level and leucocyte component (heterophils, eosinophils, basophils, lymphocytes, and monocytes), and H / L ratio. Genotype of HSP 70 affected panting frequency, on set of panting, rectal temperature, serum corticosterone concentration, HSP 70 expression, blood leucocyte and differentiation of leucocyte. The AD genotype of chicken showed the lowest panting frequency, panting on set, rectal temperature, serum cortikosterone concentration, HSP 70 expression, heterophile percentage and H/L ratio, but the AD genotype of Chicken had the highest leucocyte concentrations and lymphocyte percentage. DD genotype showed the other way around, while other genotypes did not show any significance differences. It is concluded that genotype of HSP 70 that most tolerant to heat stress is AD genotype and the most intolerant is DD genotype.