Access to the outdoors during summer affects feed efficiency, carcass composition and meat quality in a slow-growing pure strain of chickens

This study assessed the effects of outdoor access on growth performance, feed efficiency, carcass composition and meat quality in a slow-growing chicken strain. Chickens were reared either entirely indoors for 78 d or with outdoor access after 28 d of age for 82 d during the summers of 2022 and 2023. Approximately 300 chickens per group were monitored each year. Individual growth and feed intake (FI) were tracked using radio frequency identification, and feed efficiency was calculated as the gain-to-feed ratio (G:F). Carcass composition, as well as the pH, color, drip loss, cooking loss, and firmness of breast meat, of all chickens were measured. The results indicated that the chickens with outdoor access gained 4% less weight than those reared indoors (P < 0.001), with similar feed intake in both environments, except for indoor females in 2023, who consumed more than outdoor-access females in 2023 (P = 0.020). This resulted in a 2% lower G:F for the outdoor-access chickens overall (P < 0.001). Outdoor-access chickens had less abdominal fat yield, particularly females (-19% vs. -12% for males; P < 0.001), but no difference in thigh or breast yield (P > 0.05). Outdoor access influenced the quality of breast meat, which had a more rapid decrease in pH postmortem, lower ultimate pH, more cooking loss and a paler and less red color (all P < 0.001), although consumers likely could not have detected the differences in color. In 2022, outdoor temperatures reached 36 °C, compared to 30 °C indoors, which was associated with significantly higher water loss in the meat (P < 0.001). These results highlight trade-offs of outdoor access for slow-growing chickens, particularly during the summer. While providing outdoor access decreases fat accumulation, it also decreases growth, feed efficiency, and meat quality. Practical applications include targeted management strategies, such as optimizing the diet to increase nutrient intake, mitigating the effects of heat in the summer, or rearing the sexes separately to address the differing effects of sex on performance. Future research should explore appropriate behavioral and physiological indicators of chickens' ability to adapt to outdoor access as well as the potential to integrate these indicators into breeding strategies.