Concept of multiple stresses and its significance on livestock productivity

Abstract

Animals reared in tropical environments are generally subjected to more than one stress at a time. This greatly influences the animal production and reproduction under such environmental conditions. Nearly all studies on the effect of environmental stress on farm animal productivity have generally implicated one stress at a time since comprehensive, balanced multifactorial experiments are technically difficult to manage, analyze, and interpret. Hence, few reports evaluating effects of multiple stresses on farm animals are available in the literature. However, researchers have described several hypothetical schemes highlighting how two stressors can synergistically influence normal physiologic functions in mammalian species. Thermal stress in livestock is aggravated when feed restriction is involved. These effects are often manifested in changes in the blood biochemical parameters, enzymes, and thyroid hormone levels in livestock. Generally, when nutrition is not compromised, livestock species cope with heat stress better. Further, several findings have shown that livestock species tolerate and adapt to nutritional stress more than thermal stress. However, when both stresses are present, severe impacts on all the biologic functions in the livestock have been observed. Hence, it may be pertinent to conclude that the combined effects of two stressors may have severe impact on biologic functions in livestock species. Further studies involving more than one stress at a time emphasized the importance of providing optimum nutrition to livestock for counteracting thermal stress during summer. These types of investigations will be instrumental in gaining a thorough understanding of the role of nutrition in mitigating adverse effects of environmental stress on livestock and how the knowledge garnered can be used to develop rational managerial strategies for optimizing productivity in livestock farms.