Invited Review: Hypophagia and hypogalactia associated with heat stress

Abstract

ABSTRACT Heat stress depresses growth, lactation, and mammary development and when occurring during in utero development, may have life-long effects on meat and milk production. These phenotypic responses result in billions of dollars in losses to US animal agriculture producers annually. Implementation of heat abatement strategies (shade, misters, sprinklers, and fans) has reduced the financial burden of heat stress, but many of these cooling methods are limited to intensive production systems and are water demanding. The extensive consequences of heat stress, increasing global temperatures, water use limitations, and water run-off concerns make it imperative that animal agriculture find alternative approaches to mitigate these heat-related production losses. This review examines the common responses to heat exposure across species, including depressed feed intake, growth, and milk production, while addressing the maternal and offspring responses to heat stress during gestation. The conservation of the hypophagia and hypogalactia induced by heat exposure among homeotherms proposes that the mechanism by which heat depresses production is conserved across species. Herein, I discuss how redistribution of blood flow from the viscera to the periphery may explain production losses and propose that by preventing the adaptive decrease in visceral blood flow, we may limit production losses.