Document Detail

Strategies for managing reproduction in the heat-stressed dairy cow.
MedLine Citation:
PMID:  15526779     Owner:  NLM     Status:  MEDLINE    
Establishment and maintenance of pregnancy is difficult in lactating dairy cows exposed to heat stress because of reductions in estrous detection rate and the proportion of inseminated cows that maintain pregnancy. The most common approach to ameliorate heat stress in developed countries has been to alter the cow's environment through provision of shade, fans, sprinklers, and so on. Nonetheless, seasonal variation in reproductive function persists. Increased understanding of bovine reproductive function and its alteration by heat stress has led to additional strategies for reducing deleterious consequences of heat stress on reproduction. These include hormonally induced timed artificial insemination, which can reduce losses in reproductive efficiency caused by poor detection of estrus, and embryo transfer, which can increase pregnancy rate by allowing embryos to bypass the period when they are most sensitive to elevated temperature (i.e., in the first 1 to 2 d after breeding). Other efforts are directed toward developing methods to protect the embryo from harmful actions of elevated temperature. Approaches being studied include manipulation of embryonic synthesis of heat shock proteins and use of antioxidants to reduce free radical damage associated with heat stress. It may also be possible to reduce the magnitude of hyperthermia caused by heat stress. This might be possible physiologically, for example by feeding of agents that affect thermoregulatory systems, or genetically by selecting for specific traits conferring thermal resistance. Finally, the development of bovine somatotropin as a lactational promotant means that it may be possible to extend lactations beyond 305 d and voluntarily discontinue inseminations during periods of heat stress.
P J Hansen; C F Aréchiga
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Review    
Journal Detail:
Title:  Journal of animal science     Volume:  77 Suppl 2     ISSN:  0021-8812     ISO Abbreviation:  J. Anim. Sci.     Publication Date:  1999  
Date Detail:
Created Date:  2004-11-05     Completed Date:  2004-11-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8003002     Medline TA:  J Anim Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  36-50     Citation Subset:  IM    
Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611-0920, USA.
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MeSH Terms
Cattle Diseases / physiopathology*
Embryonic Development
Fetal Death / etiology
Heat Stress Disorders / complications,  genetics,  physiopathology,  veterinary*
Pregnancy Maintenance

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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