Nutritional modulation of somatotropic axis-cytokine relationships in cattle: a brief review.

The objective of this review is to summarize data on the interrelationships that exist between nutrition, the endocrine system and their modulation of plasma tumor necrosis factor-alpha responses to endotoxin in cattle. During stress, intake of nutrients often is compromised and a percentage of available nutrients are diverted away from growth processes to stabilize other physiological processes of a higher survival priority. Management practices that minimize the magnitude and duration of disease stress will aid in speeding the return to homeostatic equilibrium. However, the shift away from growth during stress is almost inevitable as a mechanism to survive. Some degree of control and management of the metabolic cost of disease stress involves understanding the integration of nutritional, endocrine and immune signals by cells and working with the natural homeostatic processes. Endocrine hormones and immune system cytokine signals participate in redirecting nutrient use during disease stress. In an intricate interplay, hormones and cytokines regulate, modify and modulate each other's production and tissue interactions to alter metabolic priorities. Levels of dietary protein and energy intake affect patterns of hormones and cytokines in the blood after endotoxin challenge and further modulate the biological actions of many of these regulatory effectors. In vivo, administration of growth hormone to young calves has significant effects to decrease the many specific physiological responses to endotoxemia. Many aspects of nutrition can attenuate or facilitate this effect.