Growth patterns and heat tolerance analysis of dwarf chicken with frizzled feather

Chickens are covered with feathers, lack sweat glands, and are sensitive to the thermal environment. Previously, our group bred a novel dwarf chicken strain with frizzled feather, named as dwarf chicken with frizzled feather (DFC). The cumulative growth of the chicken body weight and size were analyzed with 3 mathematical models. Subsequently, chickens were grouped to investigate the impact of heat stress (HS) on their slaughter performance, histomorphological development and gene mRNA change (HSP70, muscle development and appetite-related factors) using quantitative real-time PCR, tissue sections and Western Blot. In the HS group, chickens were placed at 34 ± 1°C for 8 hours (9:00 am - 17:00 pm) a day and lasted for 2 weeks, while in the control group, chickens were fed at 26 ± 1°C. Chicken tissue samples were collected at the age of 120 days to evaluate production performance, histological changes, and gene expression changes. Our results found that the Gompertz model was the best for fitting the body weight of DFC. The integrity of muscle, liver, spleen, and small intestine tissues was affected under HS conditions. Correspondingly, the length of the ileum was significantly decreased (P < 0.05), the thigh muscle development factor MYOD1 expression was down-regulated (P < 0.05), while the expression of MSTN was up-regulated (P < 0.001). In addition, the jejunum VH / CD was reduced significantly (P < 0.05). The mRNA of appetite-promoting factors AMPKα-1 and AGRP in the gut-brain axis were down-regulated (P < 0.05), while appetite-restrain factors CCK, GHRL, and CART were significantly up-regulated (P < 0.05 or P < 0.01). Moreover, the intestinal transport and absorption factors ZO1, OCLN, PepT1, SGLT1, and CAT1 were up-regulated (P < 0.05 or P < 0.01), and GLUT1 was down-regulated (P < 0.05). These results indicated that HS mainly impacted the appetite of chickens and did not significantly disrupt the nutrient absorption function of these chickens. The DFC appeared to be more tolerant to the hot environments for their frizzled feathers, small body size, and low basal metabolic rate.