Grazing and cattle health: a nutritional, physiological, and immunological status perspective

Abstract

Grazing is thought to contribute to behavioral and clinical aspects of cattle welfare. However, little information is available about the effect of grazing on cattle health. The aim of this review was to evaluate the impact of grazing on the physiological, immunological, and nutritional status of cattle and to discuss the means by which we should assess the health of grazing cattle. Due to a mismatch between the nutritional supply of forage and the demand of grazing cattle, grazing often induces an imbalance of protein and energy intake and a negative energy balance in cattle, which impairs hormone (insulin and IGF-1) production, fertility (ovarian cyclicity resumption, pregnancy, embryonic development, and oocyte maturation), and immunity. Grazing also affects the circulation of immune-related cells; however, the impact of grazing on immune function is unclear. In contrast, evidence shows that grazing in diverse vegetation improves the mineral intake balance and reduces oxidative stress in cattle. The impact of grazing on cattle health varies with the grazing conditions, including the pasture condition and outside environment, implying that a stereotypical view of grazing is not beneficial for cattle health. Thus, multiple parameters and a comprehensive approach are crucial to evaluating the health of grazing cattle.