Effect of climatic variables on production and reproduction traits of colored broiler breeder poultry

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.

A retrospective study of Newcastle disease in Kenya

Newcastle disease (ND) is a major constraint to Kenya’s poultry production, which is comprised of approximately 80% indigenous chickens (ICs; caged and free-range system) and 20% exotic chickens (intensive system). This study analyzed cases reported as suspected ND in Kenya between 2005 and 2015. Of the suspected 332 ND reported cases from the three production systems in 27 locations within six Kenyan Agro-Ecological Zones (AEZs), 140 diagnosed as infected with avian orthoavulavirus 1 (AOaV-1; formerly Newcastle disease virus) were present in every year in all AEZs. The numbers of AOaV-1-positive cases differed significantly (p < 0.05) between the production systems across the years depending on the season, climate, and location. In the free-range system, both ambient temperatures and season associated significantly (p = 0.001 and 0.02, respectively) with the number of cases, while in the intensive and caged systems, the positive cases correlated significantly with season and relative humidity, respectively (p = 0.05). Regardless of the production systems, the numbers of clinically sick birds positively correlated with the ambient temperatures (r = 0.6; p < 0.05). Failure to detect AOaV-1 in 58% of the ND cases reported, and mortalities exceeding the observed numbers of clinically sick birds suggest deficiencies in the current ND reporting and diagnostic system. Intensive farmers were the slowest in reporting the cases and diagnostic deficiencies were most evident by failure to test the exposure of ICs to natural infection with AOaV-1 and for the AOaV-1-negative cases lack of testing for other pathogens and/or AOaV-1 variants. This study indicates a need for improved surveillance and diagnostics in Kenyan domestic poultry.

Genetic selection for growth performance and thermal tolerance under high ambient temperature after two generations using heat shock protein 90 expression as an index

Genetic selection for productive performance in high ambient temperatures was performed on two chicken strains, Rhode Island Red and Sinai, for two generations, and the heritable responses to tolerance were estimated using heat shock protein 90 (HSP90) gene expression. The results are summarised as follows: (1) heat stress negatively affected some economic traits, mainly bodyweight. This effect was more pronounced in the parent stock than in the first generation (F1) and second generation (F2). (2) This effect was modulated by the chicken strain, and the decreased bodyweight was more pronounced in RI strain than in the Sinai strain, indicating that the Sinai strain is more tolerant to high ambient temperature. (3) The offspring (F1 and F2) of both strains were more tolerant to high ambient temperature; this trend was also true for the parents of these two strains. (4) HSP90 mRNA expression was the same in both strains under normal conditions in all three generations. (5) Under high ambient temperature conditions, the Sinai strain (all generations) showed significantly increased HSP90 mRNA expression compared with the Rhode Island Red strain. These findings suggest that heat tolerance is passed from parents to offspring. We recommended that selection for heat-stress tolerance be applied to producing commercial strains reared in hot climate conditions.