Environmental stress and livestock productivity in hot-humid tropics: Alleviation and future perspectives

Tropical environments are characterized by persistently high temperature and relative humidity and the harsh environmental conditions pose a serious limitation on the optimal performance of the animals raised in this region. Heat stress causes deleterious effects on welfare, immunology and physiology of farm animals with a resultant impact on their productivity as the use of body resources is re-organized and the metabolic priorities of animals shift away from production, growth, health and reproduction. It is imperative to understand the mechanisms involved in the thermoregulation of animals under tropical conditions in order to develop appropriate strategies for their improvement. This review focuses on the available data on the increasing global temperature and the adverse impact of tropical conditions on animals' adaptive mechanism affected during thermal stress on production performance, intestinal and ileal microbiome, physiological responses, antioxidant system, metabolic responses, cellular and molecular response, adaptive mechanism strategies to heat stress and also strategies to palliate environmental stress on livestock under humid tropical conditions including environmental manipulation, genetic opportunity, epigenetic and feeding modification. Overall, the present review has identified the disturbance in the physiological indices of tropical livestock and the need for concerted efforts in ameliorating the adverse impacts of high ambient temperature aggravated by high humidity on livestock in tropical environments. Further research is needed on genotype-by-environment interaction on the thermotolerance of different livestock species in the tropics.

Evaluation of sweet citrus peel supplement in water on performance and ileal microbial count of broiler chickens

The effect of supplementing drinking water with sweet citrus peel powder (SCPP) on the performance, ileal microbial count, and relative weight of organs of broiler chickens reared in a tropical environment was investigated. Ninety-six (96) 1-day-old Ross broiler chickens, after brooding, were randomly allotted into four treatment groups: T1 (control) received drinking water without SCPP, while birds in T2, T3, and T4 were given water supplemented with 2, 4, and 6 g of SCPP per liter of water, respectively. Each treatment was replicated three times with eight birds per replicate in a completely randomized design. Feed intake and weight gain were not significantly (p > 0.05) different among the treatments. However, significant variations (p < 0.05) were observed in the final weight and feed conversion ratio (FCR) with birds on T4 (6 g SCPP) having the highest final weight of 2164.60 g and the lowest FCR of 2.11 compared with 1838.40 g final weight and 2.40 FCR recorded for birds in the control group. Total bacteria count (TBC) of 2.07 × 10⁶ CFU/ml (T1), 1.20 × 10⁶ CFU/ml (T2), 1.27 × 10⁶ CFU/ml (T3), and 1.33 × 10⁶ CFU/ml (T4) recorded showed no significant (p > 0.05) variations among the treatments. However, orthogonal contrast between control and SCPP treatment groups showed significant variation (p < 0.05) in TBC. Significant variations (p < 0.05) were observed in the live weight and relative weight of heart and pancreas. Higher live weight with lower FCR and TBC recorded in this study showed the positive effect of SCPP on the performance and ileal microbial count of broiler chickens.