Heat tolerance in poultry production was obtained attention due to the need for genetic lines that can withstand climate changes. This study aimed at investigating heat tolerance in commercial and native broiler genetics, as well as the physiological and growth performance responses of HSP70 genotypes submitted to heat stress. In Experiment I, heterophil:lymphocyte (H:L) ratio, as an indicator of heat tolerance, was compared between commercial broilers (n = 100) and Thai native chickens (n = 100). Growing chickens (with similar initial weight) of each genetic strain were randomly divided into two groups: 1) thermoneutral environment (26 ^oC ± 2 ^oC) and 2) heat stress (36 ^oC ± 2 ^oC). The results showed that native chickens originating from a tropical environment presented lower H:L ratio and mortality rate compared with commercial broilers. In Experiment II, HSP70 genotypes were compared. PCR-RFLP was applied to identify the genotypes (C1C1, n = 38; C1C2, n = 38; and C2C2, n = 28). Ten-week-old chickens of each genotype were evaluated in the same environments described in Experiment I. Heat-stress indicators - respiratory rate (RR), cloacal temperature (CT), packed cell volume (PCV), and average daily gain (ADG) - were measured for three weeks. The significant difference in PCV indicated that C2C2 chickens were less tolerant to heat stress compared to other genotypes. The RR, CT, and ADG were not significantly different among all genotypes. Since the C2C2 genotype was shown to be sensitive to heat stress, C1C1 and C1C2 could be used as markers for heat-tolerant genetic strains of Thai indigenous chickens and hybrid commercial lines.

This study aimed to study the role of PPARs on fat deposition in native crossbred chicken. We studied the growth, abdominal, subcutaneous, and intramuscular fat, and mRNA expression of PPARA and PPARG in adipose and muscle tissues of four chicken breeds (CH breed (100% Thai native chicken), KM1 (50% CH background), KM2 (25% CH background), and broiler (BR)). The result shows that the BR chickens had higher abdominal fat than other breeds (p < 0.05) and the KM2 had an abdominal fat percentage higher than KM1 and CH respectively (p < 0.05). The intramuscular fat of BR was greater than KM1 and CH (p < 0.05). In adipose tissue, PPARA expression was different among the chicken breeds. However, there were breed differences in PPARG expression. Study of abdominal fat PPARG expression showed the BR breed, KM1, and KM2 breed significantly greater (p < 0.05) than CH. In 8 to 12 weeks of age, the PPARG expression of the CH breed is less than (p < 0.05) KM2. Crossbreeding improved the growth of the Thai native breed, there was also a corresponding increase in carcass fatness. However, there appears to be a relationship between PPARG expression and fat deposition traits. therefore, PPARG activity hypothesized to plays a key role in lipid accumulation by up-regulation.

Objective: The objectives of this study were to investigate the relationship between the mRNA expression of adipocyte type fatty acid binding protein (A-FABP) and heart type FABP (H-FABP) in Thai native chicken crossbreeds and evaluate the level of exotic inclusion in native chicken that will improve growth while maintaining its relatively low carcass fat.Methods: The fat deposition traits and mRNA expression of A-FABP and H-FABP were evaluated at 6, 8, 10, and 12 weeks of age in 4 chicken breeds (n = 8/breed/wk) (100% Chee breed [CH] [100% Thai native chicken background], CH male and broiler female [Kaimook e-san1; KM1] [50% CH background], broiler male and KM1 female [Kaimook e-san2; KM2] [25% CH background], and broiler [BR]) using abdominal fat (ABF) and muscular tissues.Results: The BR breed was only evaluated at 6 weeks of age. At week 6, the CH breed had a significantly lower A-FABP expression in ABF and intramuscular fat (IF) compared with the other breeds. At 8 to 12 weeks, the KM2 groups showed significant upregulation (p<0.05) of A-FABP in both ABF and IF compared to the CH and KM1 groups. The expression of H-FABP did not follow any consistent pattern in both ABF and IF across the different ages.Conclusion: Some level of crossbreeding CH chickens can be done to improve growth rate while maintaining their low ABF and IF. The expression level of A-FABP correlate with most fat traits. There was no consistency of H-FABP expression across breed. A-FABPs is involved in fat deposition, genetic markers in these genes could be used in marker assisted studies to select against excessive fat accumulation.

The mtDNA D-loops of four chicken breeds (Betong, Khao Chang, Srivijaya Naked-Neck, and Dang) from the native chicken populations of Narathiwat province and Red jungle fowl from the southern region of Thailand were analyzed to assess their genetic diversity and genetic relationships. The 558 fragments of the mtDNA D-loop were genotyped using PCR, and 20 variation sites and 23 haplotypes were detected in 326 mtDNA D-loop sequences. The haplotype diversity and nucleotide diversity of the Red jungle fowl were 0.936 ± 0.034 and 0.00806 ± 0.00087, respectively. Thai native chicken populations had a haplotype diversity of 0.000 to 0.9050, and a nucleotide diversity of 0.00000 to 0.00856, thus revealing the high genetic diversity of the native Thai chicken breeds. Analysis of molecular variance indicated that most of the variation was within the population (78.20%). The results of the median-joining network and phylogenetic tree were consistent and revealed that Thai local chicken breeds and Red jungle fowl were divided into eight main haplogroups (A-F, H, and V). The greatest number of haplotypes was classified into haplogroup B (6 haplotypes), followed by haplogroup V (5 haplotypes). Moreover, there was no breed-specific haplogroup. These results suggest that the breeds likely originated from multiple matrilineal lines, and the mtDNA D-loops assessed in this study appear to lack breed specificity.

Objective: This study was conducted to investigate polymorphisms of the melanocortin-4 receptor (MC4R) and insulin like growth factor 2 (IGF2) genes and to evaluate the growth traits affected by such polymorphisms in Thai native (Kradon) pigs.Methods: Blood samples and productive data from 91 Kradon pigs were collected. DNA was extracted and quantified, the IGF2 and MC4R genes were amplified, and the polymerase chain reaction (PCR) produces were digested using the PCR-restriction fragment length polymorphism (PCR-RFLP) technique. Genotyping was performed, and the association between genotypes and growth traits on the birth and weaning weights were evaluated.Results: The IGF2 intron7 g.162G>C variations in Kradon pigs were found in three genotypes: i) GG, ii) GC, and iii) CC. The GG genotype frequency was the highest followed by the GC and CC genotypes. The frequencies of the G and C alleles were 0.703 and 0.297, respectively. The MC4R genotype was found in only one genotype (GG). The IGF2 gene pattern was not associated with birth weight traits, whereas the IGF2 gene pattern was related to the weaning weight trait in Kradon pigs. Pigs with the CC and GC genotypes had higher weaning weights than ones with the GG genotype (p<0.001).Conclusion: Thai native Kradon pigs with the CC and GC genotypes of the IGF2 gene have higher weaning weights than pigs with the GG genotype.