Journal of Animal Science, Vol 74, Issue 5 944-949, Copyright © 1996 by American Society of Animal Science

JOURNAL ARTICLE

Relationship of weaning-to-estrus interval to timing of ovulation and fertilization in sows

B. Kemp and N. M. Soede
Wageningen Institute of Animal Sciences, Wageningen Agricultural University, The Netherlands.

Data from two experiments were used to study the relationship between weaning-to-estrus interval (WEI, varying from 3 to 6 d) and the duration of estrus, the interval from onset of estrus to ovulation and fertilization results at 120 h after ovulation, in 201 multiparous sows. An increase in WEI resulted in a decrease in the duration of estrus (Duration of estrus (h) = [81 (exp1) or 88 (exp2)]-.33 x WEI, R2 = .25, P < .001) and a decrease in the interval from onset of estrus to ovulation (onset estrus to ovulation (h) = [54 (exp1) or 59 (exp2)]-.20 x WEI, R2 = .23, P < .001). Sows that were inseminated between 0 and 24 h before ovulation showed consistent high fertilization results (91% normal embryos), irrespective of WEI. Sows that were inseminated outside this range showed an increased proportion of unfertilized eggs (P < .001). This increase occurred similarly in all weaning to estrus intervals. These results suggest that negative effects of a longer WEI on subsequent litter sizes and farrowing rates as described in literature might be a result of suboptimal timing of insemination relative to ovulation and not of poor fertility in these sows.

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