Ovulation in Swine

Ovulation occurs 36 to 42 hours after the onset of standing heat in mature sows, about 12 hours earlier in gilts. On average, 10-20 ova are shed from follicles ranging from 0.7 to 1.0 cm.

Fecundity is highest in sows at 2 to 4 years of age. Gilts average 10-15 ova per cycle. Embryonic survival rate is 65%-75%, resulting in litter sizes of 8 to 12 piglets. Very high ovulation rates do not yield greater litter sizes. Heritability of litter size is low, but tremendous breed differences exist (ex. Meishan). Recent studies suggest fecundity may be linked to the presence of a specific estrogen receptor.

In addition, fecundity is strongly linked to lactational feed intake. Limiting feed intake in gestation leads to greater feed intake during lactation. High feed intake in lactation results in good milk production, high piglet weights at weaning, short wean to estrus intervals, and maximal ovulation rates.

Copyright ©1997 by the University of Pennsylvania School of Veterinary Medicine
Faculty: Dr. Paul Pitcher
Student: Sandra Springer,'99