Effects of post-weaning stress and feeding management on return to oestrus and reproductive traits during early pregnancy in swine

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Abstract
A total of 177 sows representing five two-breed crosses were used in a 2×2 factorial experiment to study the effects of post-weaning stress (changing environment and group housing) and feeding regime (flushing by feeding ad libitum until mating) on the weaning-oestrus interval and other reproductive traits up to 30 days of pregnancy.The group which was stressed had about 10% (P<0·05) fewer reproductive failures than those not stressed, while little difference was found between the two feeding regimes. About 61% of the flushed sows returned to oestrus within 7 days after weaning, 9% higher than for those not flushed. The stress treatment had little effect on the weaning-oestrus interval. Neither treatment affected ovarian and follicular-fluid weights, percentage of follicles of different sizes, ovulation rate nor number of viable embryos. The flushed group, however, had 9% lower embryo survival than the group not flushed. A positive relation was found between the number of days on ad libitum feeding and ovulation rate and embryonic mortality.Differences among breeds were significant for all the traits, except weaning-oestrus interval, weight of follicular fluids, percentage of large follicles, ovulation and survival rates. The weaning-oestrus interval was not significantly correlated with any of the reproductive traits studied.