The effect of estrus duration and number of artificial inseminations on fertility of gilts and multiparous sows having a four-day wean-to-estrus interval

Abstract

Objective: To determine the relationship between duration of estrus (DE) and farrowing rate and litter size of gilts and sows receiving a single or double artificial insemination. Methods: Gilts (n=503) and multiparous sows having a 4-day wean-to-estrus interval (n=901) received either a single or double artificial insemination. Gilts were inseminated the afternoon of the day of detection of their second estrus and, where indicated, again the next morning. Sows were inseminated 24 hours after detection of estrus and, where indicated, again the next morning. Gilts were grouped by DE of <24, 24 to 36, and >36 hours and sows by DE of <36, 36 to 48, and >48 hours. Results: Insemination frequency had no overall effect on farrowing rate of gilts, but within insemination frequencies, farrowing rates were lower in gilts having a longer DE, and, also, those having the longest DE had a lower farrowing rate with a single insemination. Within the entire sow population, and in sows having a DE 36 hours,farrowing rate was lower after a single insemination. Within insemination frequencies, farrowing rates were lower in sows having a longer DE. Litter size was unaffected by insemination frequency or DE in gilts or sows. These results suggest that a single insemination is usually adequate when DE is relatively short, but where a relatively long DE is expected, multiple inseminations are indicated. Before a breeding management protocol is implemented on any farm, average DE should be determined in gilts and in sows having different wean-to-estrus intervals.