equinereprolect05

equinereprolect05 - EquineReproduction AS221 Fall,2005...

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Equine Reproduction AS 221 Fall, 2005
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Some Basics • Mature female: mare • Mature intact male: stallion • Seasonally polyestrus long day breeders • Estrus cycle ~21 days in length • Period of receptivity to male ~7 days • Gestation period 335-342 days (~11  months) • Normally produce single foal
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Mare
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Reproductive efficiency • Horses often said to be less efficient  breeders than other livestock • Mostly a man-made problem – Horses selected for other traits than  reproductive efficiency – Breeding outside of normal season – Timing and technique of breeding • Estrus detection • Artificial insemination/transported semen • Hand breeding vs. pasture breeding
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Breeding season  • Normal season ensures  foals are born during  warm weather • Artificial constraints move  the start of the breeding  season to earlier in the  year • Most registries regard  January 1 st  as “official”  birthdate
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Fooling Mother Nature • The first estrus cycles of the season (and the last  in the fall) are referred to as “transitional estrus” • These cycles are frequently of irregular duration,  and the mare may or may not ovulate • To hasten the onset of regular cycling, mares are  often put under artificial lights • Hormone treatment often is used in conjunction  with artificial lighting
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Mare reproductive anatomy-- ovary • Ovary is unique in mare— “inside out” •  Cortex is interior, medulla exterior • Ovulation takes place only at ovulation  fossa and not over entire surface
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Mare anatomy—uterus/cervix • T-shaped bipartite  uterus • Normal single  pregnancy occupies  one horn and body of  uterus • Cervix in mare is less  complex than in many  other large animals
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External anatomy mare
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Stallion
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Stallion • Some seasonality in stallion as  well – Lower libido, lower sperm count during winter • During breeding season, in constant state of  sexual receptivity  – Overuse can lead to decrease in libido – Health problems can interfere with libido,  fertility • Musculoskeletal • Systemic illness, fever
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Not prime stallion material
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Stallion reproductive anatomy
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Stallion anatomy • Testes—responsible for production of semen  and male hormones • Unilateral or bilateral retained testicles 
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equinereprolect05 - EquineReproduction AS221 Fall,2005...

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