This study endeavoured to characterise the effects of breed and calving liveweight (CW) on postpartum (pp) ovarian activity in 16 Friesian (F) and 16 Jersey (J) heifers. Half of the animals within each breed were differentially fed (High vs Low: H vs L) during the 8 weeks before calving to achieve CWs (24 h pp) of 404 (FH), 354 (FL), 334 (JH) and 279 (JL) kg. They were fully fed as one group after calving. Ovarian ultrasonography showed that the FL group had the longest postpartum anovulatory interval (PPAI) of 77 days compared to 47 days among other groups. The second dominant follicle pp emerged 6 days later in FL heifers. Breed, but not CW, affected follicle patterns in the first normal oestrous cycle. Underfeeding of Friesian heifers during late pregnancy extended the PPAI whereas Jerseys were not affected to the same extent.
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 35-38, 1995
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