@conference {40822,
	title = {Hormonal induction of oestrus during the early postpartum period and the subsequent effects of nutrition on ovarian activity in dairy heifers},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {230-232},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Our working hypothesis was that a significant period of severe  underfeeding of dairy heifers during early lactation would not prevent the  continuation of normal length oestrous cycles following hormonal induction  of oestrus and ovulation in the early postpartum period (pp; 26.0 ( 0.7 d pp).  Each of 16 Friesians (F) and 15 Jerseys (J) was treated with a CIDR device  for 5 days, with one injection of prostaglandin-F2a the day before device  removal and another injection 1.0 mg oestradiol benzoate 24 h after  removal. The feed allowances of 8 F and 7 J heifers were reduced over the  following 3 oestrous cycles, to a level where live-weights and milk yields  were depressed finally by up to 15\% and 36\%, respectively, compared to  fully fed contemporaries. Ovarian ultrasonography and monitoring of  concentrations of milk progesterone (mP4) during the 1st (Cyc 1) and 3rd  (Cyc 3) oestrous cycles showed that 3 Fs (1 FH and 2 FL) did not respond to  initial treatment, and remained anovulatory throughout. Another 3 heifers (2  FL and 1 JL) became anovulatory after an initial positive response. The size  of the first dominant follicle (DF1) and concentrations of mP4 were reduced  by restricted feeding, but only during Cyc 3. This study has shown that a  hormonal treatment can induce oestrus and ovulation in the majority of  heifers which have been calved between 20 and 30 days. Subsequent  restrictions in feeding level may convert some cycling heifers into an  anoestrous state, although most will continue to cycle.},
	issn = {1176-5283},
	author = {Burke CR and Macmillan KL and Verkerk GA}
}
