Abstract
Simple SummaryAn 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. 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.
Highlights
Introduction conditions of the Creative CommonsDriven by high consumer demand, commercial broilers have been intensively selected to achieve high production performance
The native chickens (NT) chickens exposed to thermal stress exhibited lower values of final body weight and ADG (p < 0.05), but the BWG and Feed intake (FI) between control and stressed NT groups were not significantly different
As for feed-to-gain ratio (F/G), the values were trending upward when the birds were exposed to cyclic thermal stress, no significant differences (p ≥ 0.05) between control and treatment groups were found in the chicken strains
Summary
Introduction conditions of the Creative CommonsDriven by high consumer demand, commercial broilers have been intensively selected to achieve high production performance. Modern broilers are more sensitive to thermal stress than their counterparts from 1950s and the ancestral wild jungle fowl [2], as broiler breeding was mainly focused on rapid growth and a heavy breast mass, but their respiratory and cardiovascular systems did not seem to develop at the same speed [3]. Their feathers work as thermal insulation, preventing heat dissipation, and their body parts that are not covered by feathers are in a smaller proportion. The thermal sensitivity of the birds is higher with an increasing age and weight [13]
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