@conference {40451,
	title = {The relationship between breeding index and conception rate and the cost of delayed conception},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {53},
	year = {1993},
	month = {Jan},
	pages = {41-42},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Programmes for controlled calving and controlled breeding were evaluated with a group of large herds of dairy cows and heifers. The former procedure involved an injection of an analogue of prostaglandin F2a (PGF) at about Day 274 of gestation. Groups totalling 650 cows mainly calved in the following 4 days, with a peak between 36 to 60 h. The maximum calving rate was 138 cows within one 24 h period. Although calf survival rate was high (97\%) and the incidence of calving difficulties low (3\%), 14 cows were subsequently culled because of complications caused by retained foetal membranes. The controlled breeding programmes involved the use of CIDR-B devices for 8 days (cows) or 10 days (heifers) combined with a capsule containing 10 mg of oestradiol benzoate at device insertion (all cows and heifers), and with an injection of PGF at 6 days after insertion (cycling cows and all heifers), or an injection of equine chorionic gonadotrophin (eCG) at device removal (anoestrous cows). These systems were used with herds of 3009 and 500 heifers, as well as with 350, 400, 480 and 904 lactating cows. Every heifer was inseminated initially at about 48 h after device removal, but cows were inseminated on detection over 4 days. All inseminated animals were retreated with a previously used CIDR device to re-synchronise oestrus before a second insemination about 21 days later. A second re-synchrony was also applied with some cows before their third insemination. These programmes produced 4-day submission rates in the cows of 87\% to 95\% and 48 h synchrony rates of 94\% and 95\% in the heifers. The consequences of these programmes mean that about 90\% of animals in each herd will have conceived to AB or natural mating within 6 weeks. The rate of use of induced calving next season should be reduced to about 5\%.  The increased concentration in calving is expected to reduce the incidence of treatments for anoestrum (from as high as 44\% in one of the herds) to about 10\%. Additional advantages include time saving, less labour, reduced labour stress, more cows and heifers to calf to AB sires, fewer bulls and earlier culling of bulls and empty cows. The maximum daily numbers were 904 CIDR devices inserted in 5 h, 504 heifers inseminated in 4 h and 689 cows inseminated in 5 h. Whereas calving and breeding had previously been major constraints in herd management, the use of these systems can realistically allow the herd size to be increased to more than 1000 cows. Many of the identified advantages will be equally applicable to herds of less than 200 cows.},
	issn = {1176-5283},
	author = {Wheadon MC}
}
