The effect of “Estrumate” followed by progesterone coils on oestrus synchronization and conception of post-partum beef and dairy cows

Fertility regulation in cattle

This paper reviews the physiological, endocrinological and pharmaceutical literature pertaining to the design, development and optimisation of subcutaneous and intravaginal progestogen-containing drug delivery systems used in the control of synchrony and ovulation in cattle.

Conceptual and commercially available intravaginal veterinary drug delivery systems

In the veterinary area the utilization of the vagina as a route for drug delivery has focused on the systemic delivery of hormonal steroids to control synchrony, ovulation and fertility in a variety of livestock. There are several reasons for administering drugs to modify the menstrual cycle in humans and the estrous cycle in animals and this paper provides a comparison of the objectives of drug intervention to control reproduction in humans and livestock. In addition, the types of hormones and their concentrations found during the menstrual cycle in humans and during the estrous cycle in animals are compared. The paper also reviews the intravaginal drug delivery systems developed for the control of the estrous cycle in livestock and both conceptual and commercially available intravaginal drug delivery systems that have been described in the literature are described. The history of some of the delivery systems is included and the future directions of this area of research are discussed.

Reproductive management of dairy cattle based on synchronization of estrous cycles

High-yielding dairy cows (199) were allotted to a control group or one of two groups for synchronization of estrus. Synchronization of estrus was accomplished by either insertion of a progesterone-releasing intravaginal device (progesterone coil) for 7 days with .5 mg of the prostaglandin analogue cloprostenol (Estrumate) administered 1 day before removal of the progesterone coil, or by administration of .5 mg of Estrumate followed 13 days later by a progesterone coil inserted for 9 days. Following each estrous synchronization regimen, cows were inseminated during a fixed 6-day period (insemination week). Into one-half of the cows of each treatment group, a second progesterone coil was inserted 12 days following the fixed-time insemination for 9 days. Cows that calved within 21 days were included in a cluster and were treated and inseminated simultaneously at regular 3-wk intervals. Thus, insemination of synchronized cows was during only 6 out of each 21 days. The estrous synchronization regimens were applied so that the first fixed-time insemination for any cow occurred between 59 and 79 days after calving. Control cows were inseminated following estrus, commencing 59 days after calving. Conception rates for cows of groups 1, 2, and 3 were 50, 56, and 51%. Pregnancy rates at 25 days following the fixed-time insemination were 53, 78, and 69%, and at 100 days after calving, 57, 75, and 65%. A system of reproductive management is proposed in which observations for estrous behavior and inseminations are only during 6 days out of each 3 wk.

The time of oestrus and ovulation following various synchronisation techniques using progesterone impregnated intravaginal devices

Progesterone releasing intravaginal devices (PRIDs) were used in 4 experiments involving 67 cattle to study the effect of the stage of the oestrous cycle and of oestradiol benzoate (ODB) administration on the time interval from PRID removal to oestrus and/or ovulation. Cows in which PRIDs were inserted on days 2 to 4 of the oestrous cycle for 14 days were subsequently observed by endoscopy to ovulate significantly later than cows given identical treatments on days 13 and 14 of the cycle. The concentration of progesterone was higher in the former group at the time PRIDs were removed and remained at a higher level for 3 days thereafter. The length of the oestrous cycle of untreated heifers was significantly longer than in heifers treated for 12 days with PRIDs only inserted on day 3 of cycle (19.7 v 18.2; p less than 0.01). Treatment with PRIDs inserted for 12 days together with ODB further shortened the cycle length from 18.2 days to 16.9 days (p less than 0.01). The intervals from PRID removal to onset of standing oestrus in heifers treated with PRID only and those treated with PRID and ODB were 80h and 45h, respectively (p less than 0.01); the respective variances were 280 and 4; p less than 0.01). Plasma progesterone concentration, at PRID removal, was 3 times higher in heifers treated with PRID only than in heifers treated with PRID and ODB (p less than 0.01) and the interval from PRID removal to the lowest progesterone value following it was 3.8 ad 1.2 days for the 2 groups, respectively (p less than 0.05). The study indicated that the stage of oestrous cycle at PRID insertion is an important factor which influences the interval from withdrawal of PRIDs to ovulation. The results suggest closer synchronisation would follow insertion in the mid-luteal phase (Day 13 to 14) or use of ODB treatment at the time of insertion of PRIDs.