Relationships between puberty and production traits in the gilt. 2. Oestrous symptoms at puberty

Abstract

The aim of this study was to investigate the relationships between oestrous symptoms at puberty and production traits. The gilts studied were of Swedish Yorkshire breed and belonged to a selection experiment for lean tissue growth rate. They were penned indoors in groups of six. Oestrus was checked twice daily from 160 to 260 days of age in the presence of a boar. Oestrous symptoms were carefully recorded. Blood samples for progesterone were taken regularly and puberty was defined as the first ovulation, as determined by plasma progesterone levels. Of the 547 gilts included in the study, 481 reached puberty during the experimental period. Of these, 77 gilts did not show the standing reflex at their first ovulation. However, most of the gilts had a red and swollen vulva. Gilts with low backfat thickness (high lean percentage) had less intense and shorter reddening and swelling of the vulva at puberty than gilts with high backfat thickness (low lean percentage). The backfat thickness had no influence on the ability to show the standing reflex or on the length of standing oestrus at puberty. The growth rate did not influence oestrous symptoms at puberty. The backfat thickness also influenced the levels of plasma progesterone after the first ovulation. Gilts with high backfat thickness had high levels of plasma progesterone. Age at puberty was found to have an influence on plasma progesterone levels and on vulvar symptoms. Gilts with early puberty showed intense and long durations of reddening and swelling of the vulva, and high plasma progesterone levels.