Metabolic and hormonal acclimation to heat stress in domesticated ruminants.
By U. Bernabucci, Nicola Lacetera, L. Baumgard, R. Rhoads, B. Ronchi, A. Nardone. Animal, 2010
861 citations recorded by the source corpus.
Environmentally induced periods of heat stress decrease productivity with devastating economic consequences to global animal agriculture. Heat stress can be defined as a physiological condition when the core body temperature of a given species exceeds its range specified for normal activity, which results from a total heat load (internal production and environment) exceeding the capacity for heat dissipation and this prompts physiological and behavioral responses to reduce the strain. The ability of ruminants to regulate body temperature is species- and breed-dependent. Dairy breeds are typically more sensitive to heat stress than meat breeds, and higher-producing animals are more susceptible to heat stress because they generate more metabolic heat. During heat stress, ruminants, like other homeothermic animals, increase avenues of heat loss and reduce heat production in an attempt to maintain euthermia. The immediate responses to heat load are increased respiration rates, decreased feed intake and increased water intake. Acclimatization is a process by which animals adapt to environmental conditions and engage behavioral, hormonal and metabolic changes that are characteristics of either acclimatory homeostasis or homeorhetic mechanisms used by the animals to survive in a new 'physiological state'. For example, alterations in the hormonal profile are mainly characterized by a decline and increase in anabolic and catabolic hormones, respectively. The response to heat load and the heat-induced change in homeorhetic modifiers alters post-absorptive energy, lipid and protein metabolism, impairs liver function, causes oxidative stress, jeopardizes the immune response and decreases reproductive performance. These physiological modifications alter nutrient partitioning and may prevent heat-stressed lactating cows from recruiting glucose-sparing mechanisms (despite the reduced nutrient intake). This might explain, in large part, why decreased feed intake only accounts for a minor portion of the reduced milk yield from environmentally induced hyperthermic cows. How these metabolic changes are initiated and regulated is not known. It also remains unclear how these changes differ between short-term v. long-term heat acclimation to impact animal productivity and well-being. A better understanding of the adaptations enlisted by ruminants during heat stress is necessary to enhance the likelihood of developing strategies to simultaneously improve heat tolerance and increase productivity.
Subfields: Animal Science and Zoology, Mechanical Engineering, Physiology
View Paper: https://www.semanticscholar.org/paper/ba9615718779c8865b2a53e5d45e622cbb552dae
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Citations in the corpus
- Climate Change and Global Food Systems: Potential Impacts on Food Security and Undernutrition. (2017, background): “Studies have documented that increased heat stress in cattle and pigs—with regard to both individual extreme events and accumulated excessive heat over time—decreases productivity, food intake and weight, chances of survival, and fertility (17, 110).”
- Adaptation to hot climate and strategies to alleviate heat stress in livestock production. (2012, background): “On average, conception rate drops by 24% during summertime (Bernabucci et al., 2010).”
- Physiological and biochemical blood variables of goats subjected to heat stress – a review (2018, background): “Changes in biological functions of the animals due to exposure to heat stress include physiological, hormonal, hematological, and biochemical responses, which make the goats resistant and able to survive in adverse environments (Bernabucci et al. 2010).”
- Feeding and nutrition management of heat-stressed dairy ruminants (2018, background): “Animals go through heat stress (HS) when the body temperature is higher than the optimal range specified for the normal activity because the total heat load is greater than the capacity for heat dissipation (Bernabucci et al. 2010).”