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In 3 separate trials at 2 locations, dairy heifers (n = 396) were treated with a Controlled Internal Drug Release (CIDR) progesterone device for 9 d. On Day 7 of CIDR treatment, all heifers were injected with PGF(2alpha). Synchronized estruses were detected using a tailpaint and chalk (TPC) scoring system. An animal's tailhead was painted at device(More)
The wave-like patterns of ovarian follicular development in cattle can be manipulated by shortening the luteal phase with prostaglandin F2alpha (PGF), lengthening the period of follicle dominance with progesterone or curtailing follicle development with GnRH or oestradiol as 17beta, benzoate or cypionate. These hormones can also be used to synchronise(More)
Adult dairy cows were treated with a range of doses (0.0125mg to 0.4mg) of synthetic ACTH1-24 and the plasma cortisol response was measured. Peak response was independent of dose. Higher doses of ACTH had a more prolonged effect such that the integrated response was dose dependent. Dose response curves were examined by regression analyses. Individual cows(More)
Cows in each of 10 dairy herds were assigned to two similar groups on age, breed, production, and previous mastitis history. Only cows in one group received dry cow therapy at the end of their 1977-1978 lactations. Production of all cows was tested at bi-monthly intervals during their 1978-1979 lactations. The composite evening and morning sample for milk(More)
The purpose of this study was to reengineer a commercially available intravaginal insert containing 1.9 g progesterone (CIDR intravaginal insert) for a 7-day insertion period in cattle. The reengineering process resulted in a reduced initial drug load (1.38 g) and a reduction in the residual drug load following insertion, while at the same time maintaining(More)
The objective of the present study was to determine the effect of level of feed intake of pasture on P4 clearance rates in dairy cows. Twelve non-lactating Holstein-Friesian cows aged 4-9 years were randomly allocated to a restricted or ad libitum group. The ad libitum group had unrestricted access to irrigated pasture, whereas the restricted group had(More)
This paper describes the estrus cycles of a number of livestock breeds and reviews the controlled-release drug delivery systems that are currently available for the purpose of controlled breeding. The bovine estrus cycle is reviewed in detail, and the estrus cycles of other species are described in a manner that highlights similarities and differences(More)
A synchronization treatment was initiated when each of 1227 heifers (four trials) was tailpainted. The tailpaint was sprayed with an aerosol raddle at the end of the treatment period. The heifers were in herds of 20 to 279 animals. Each herd was observed for estrus at selected post treatment intervals. A heifer was considered to be (or to have been) in(More)
Cows with an extended interval from calving to first ovulation (PPI) have increased intervals from calving to conception and are more likely to be culled compared with cows with a short PPI. In year-round calving dairy herds, between 11 and 38% of cows are reported as anestrus by 50 or 60 d after calving. In seasonally calving dairy herds, between 13 and(More)