Pre-hatch thermal manipulation and post-hatch guanidinoacetic acid supplementation enhance meat quality under chronic heat stress in broiler chickens

This study aimed to evaluate the effects of pre-hatch thermal manipulation (TM) and post-hatch guanidinoacetic acid (GAA) supplementation on meat quality in male broiler chickens exposed to chronic heat stress (CHS). A total of 710 Ross 308 eggs were incubated under two conditions: a control group maintained at 37.8°C with 56% relative humidity and a TM group (39.5°C and 65% RH for 12 h/day, from embryonic days 7 to 16). After hatching, chicks were divided into four experimental groups (n=12 birds/pen; 5 replicates/treatment): control (C), control with 1.2 g/kg GAA supplementation (GAA), pre-hatch TM (TM), and TM with 1.2 g/kg GAA supplementation (GT). All birds were exposed to heat stress conditions (32-36°C, 6 h/day) from days 28 to 42. Experimental treatments significantly influenced the ultimate pH, lightness (L), and redness (a) values of the pectoral (p≤0.05). The GT and Control groups exhibited the highest and lowest ultimate pH, respectively. In the Texture analysis, the GT group breasts had a higher juiciness compared to the control, (p=0.0002), while other sensory parameters remained unaffected. GT and GAA increased the pectoralis major yield (1.58%). No significant differences were observed in myopathy rates among treatments. These findings suggest that pre-hatch TM and post-hatch GAA supplementation improve meat quality attributes, including pectoralis major yield, juiciness, and color, in broilers under CHS.