The effects of tropical environmental conditions on the stress and immune responses of commercial broilers, Thai indigenous chickens, and crossbred chickens

Abstract

Heat stress is a life-threatening factor in commercial broilers raised in the tropics (e.g., Thailand) without temperature-controlled housing facilities. However, these temperature-controlled facilities are hardly affordable by small-scale farmers. To avoid such limitations, a Thai indigenous crossbred line (C line), selected as a candidate meat-type chicken to survive in the tropical environment, was examined for its capacity to tolerate the tropical climate and for its immune functions. Comparisons, in terms of the stress and innate and humoral immune responses using the heterophil-to-lymphocyte ratio, abdominal exudative cell phagocytic activities, and serum anti-SRBC titer, were made between C-line chicks and the corresponding cohorts from their low-meat-yielding Thai indigenous (T line) parents and from high-meat-yielding commercial broiler (B line) chickens. The responses were evaluated in the 3 different seasons of Thailand (monsoon, summer, and winter). Significantly higher stress levels (P < 0.001), based on the heterophil-to-lymphocyte ratios, were detected in the B line chicks compared with those in the T and C lines at all ages regardless of the season, suggesting that the B line chicks were vulnerable to tropical heat stress whereas the T and C lines were well adapted, with no significant differences detected between the latter two. The innate and humoral immunities of B-line chicks were significantly lower (P < 0.001) than those of T-and C-line chicks. The differences were immense in the summer, when the immunity of the C-and T-line chicks outperformed that of the B-line chicks, with mean opsonized-SRBC phagocytic activities of 7.90, 8.31, and 4.74 and mean IgG titers of 8.00, 8.40, and 5.10, respectively. This could be a consequence of the heat stress causing immunosuppression in B-line chicks, and could represent a noteworthy adaptation to the tropical conditions of the C-and T-line chicks. The apparent climate-tolerant capacity conserved in the C-line chickens, with approximately 50% T genetics, could serve as a guideline for further genetic improvement toward a high-meat-yielding chicken that retains a suitable heat tolerance.

Impacts of small-scale chicken farming activity on antimicrobial-resistant Escherichia coli carriage in backyard chickens and children in rural Ecuador

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Hematological parameters and selected intestinal microbiota populations in the Indonesian indigenous crossbred chickens fed basal diet supplemented with multi-strain probiotic preparation in combination with vitamins and minerals

“…Indeed, Tirawattanawanich et al . [ 46 ] revealed that Thai indigenous crossbred chickens had a better tolerance to heat stress than modern broiler chickens. Due to the latter study and the fact that the experiment was conducted during the rainy season (average temperature during the day was 30°C±2°C), the vitamins and minerals supplementation seemed to produce minimal effect as the Indonesian indigenous crossbred chickens less suffered from heat stress.…”

Changing risk of environmental Campylobacter exposure with emerging poultry production systems in Ethiopia

“…Stresses, such as heat stress, or food and water restriction, is known to be detrimental to the chicken's immune function, altering tissue invasion of intestinal bacteria [ 24 , 25 ]. However, different types or lines of chickens show variation in both the effect of heat stress on their immune response [ 26 ] and their ability to regulate the immune response to Campylobacter [ 27 ]. The links between management system, chicken welfare, stress and the biology of Campylobacter infections remain poorly understood, but have raised concerns about how farming systems may impact on public health risk [ 28 – 30 ].…”