THE INFLUENCE OF INSULIN ADMINISTRATION AFTER WEANING THE FIRST LITTER ON OVULATION RATE AND EMBRYO SURVIVAL IN SOWS

Primiparous crossbred sows (n = 43), lactating for an average of 21.1 +/- 0.1 d and weaning 8.7 +/- 0.1 pigs, were used to evaluate the infl uence of insulin on ovulation rate and embryo survival. The sows were maintained on 2.3 kg/head/d of a 14% protein gestation diet during pre gnancy, fed ad libitum during lactation, given 2.7 kg/head/d from wean ing until re breeding and fed 2.3 kg/head/d after mating. Beginning th e day after weaning (Day 0) sows were treated with 0.4 IU/kg body weig ht (BW) insulin (n = 21) or were administered an equivalent volume of saline (n = 22) for 4 d. Beginning on Day 3 and continuing until Day 1 4 after weaning, the sows were checked for estrus twice daily and were artificially inseminated using pooled semen from 2 fertile boars. At slaughter (days 30 to 40 of gestation), ovaries and uteri were collect ed, and the ovulation rate, embryo number and viability, and uterine w eight and length were evaluated and recorded. Use of insulin decreased the average interval from weaning to estrus compared with saline by i ncreasing percentage in estrus by Day 14 after weaning (5.0 +/- 0.57 v s 6.9 +/- 0.56 d, respectively; P < 0.03). Ovulation rate, number of e mbryos, embryo survival, and average uterine length and weight were no t influenced by insulin treatment. Overall, insulin affected reproduct ive efficiency in primiparous sows by increasing the percentage of sow s in estrus. (C) 1998 by Elsevier Science Inc.