Effects of Cyclic Thermal Stress at Later Age on Production Performance and Meat Quality of Fast-Growing, Medium-Growing and Thai Native Chickens

SIMPLE SUMMARY: An increase in global surface temperature has raised a serious concern, as it can remarkably decrease broiler production, hence altering food security. This study investigated the effects of cyclic thermal stress, mimicking the rise of temperature during the day in tropical regions on production performance and meat quality of fast-growing commercial broilers (BRs), slow-growing Thai native (NT) chickens and medium-growing ones obtained from crossbreeding between BR and NT. The results indicated that, upon an exposure to thermal stress (35 ± 1 °C, 6 h daily) for 3 weeks prior to their specific market ages, all three chicken strains showed reduced final body weight and decreased average daily weight gain in comparison to their control counterparts. The adverse effects on production performance were less pronounced in the medium-growing and slow-growing chickens, with no significant alteration in their meat quality indices. ABSTRACT: The present study aimed at assessing the impact of cyclic thermal stress on production performance and meat quality of commercial broilers (BRs), Thai native chickens (NT) and the hybrids between BR and NT (H75; crossbreed 25% NT). At the age of 3, 5 and 9 weeks for BR, H75 and NT, respectively, each strain was equally divided (n = 50) into control and treatment groups. The controls were raised at a constant 26 ± 1 °C, while the treatments were subjected to thermal stress (35 ± 1 °C, 6 h daily) for 3 weeks. The results indicated that final weight and average daily gain of BR and NT treated groups were significantly lower than those of their control counterparts. Reduced body weight gain of BR and H75, as well as feed intake of H75, was observed in the treatment groups (p < 0.05). The stressed BR breasts showed decreased moisture, fat and carbohydrate, accompanied by increased protein, ash, L *-value, b*-value and shear force (p < 0.05). No significant effects (p ≥ 0.05) of the thermal stress on meat quality indices were found for H75 and NT breast samples. Pectoral myopathies were observed in BR and H75 chickens, but the numbers of cases were decreased in the thermally treated groups.