Pregnant Mare Serum Gonadotropin Injection Research Articles

Ovarian Response of Cows Following Pregnant Mare Serum Gonadotrophin Treatment during Two Successive Estrous Cycles

Thirteen cows (8 Holsteins, 3 Ayrshire, 2 Shorthorn; 3 to 7 years old) were treated with pregnant mare serum gonadotrophin (PMSG) during two successive estrous cycles. The gonadotrophin was injected on Day 16 of the cycle (estrus = Day 0) and again on Day 16 of the nest cycle (10 cows) or 21 days after previous PMSG injection (3 cows). Doses of PMSG injected during the first cycle were 3,000 IU (6 cows: Group A) and 2,000 IU (7 cows: Group B). These doses were reversed for the individual cow during its next estrous cycle. Cows were slaughtered 10 to 14 days after the second PMSG treatment. Response to PMSG was evaluated as number of ovulations and total follicular response (calculated by the sum of ovulations plus follicles greater than 10mm diameter). Mean ovulation rate and mean total follicular response were 19.5 (±7.80) and 20.7 (±7.96) for Group A cows and were 10.7 (±4.72) and 29.1 (±11.32) for Group B. Two cows in Group B had not ovulated before slaughter; mean ovulation rate of the remaining 5 cows was 15.0. Substantial superovulation responses may be obtained following the second of two PMSG treatments during two successive estrous cycles.

MPA impregnated intravaginal sponges for the induction of oestrus in anoestrous Border Leicester × Merino ewes. 2. Maiden ewes

In the spring of 1965 flocks of 18-month-old (flock 1) and 12-month-old (flock 2) anoestrous maiden ewes were treated for 13 days with intravaginal sponges impregnated with 17a - acetoxy 6a - methylpregn - 4 - ene - 3,20 - dione (MAP). Each ewe was given an injection of 1000 i.u. Pregnant Mare Serum Gonadotrophin (PMSG) at the time of sponge removal with half the ewes of each flock receiving a further injection of 1000 i.u. PMSG 16 days later. In the period 2-8 days after sponge removal, 45.9 and 57.1 per cent of the ewes in flocks 1 and 2 respectively were served, and of these 5.9 and 17.9 per cent respectively lambed. The second injection of PMSG produced a second oestrous period, 17-25 days after sponge removal, in 89.5 and 70.8 per cent of the ewes of flocks 1 and 2 respectively, and of these, 64.7 and 29.4 per cent, respectively, lambed. The additional administration of PMSG significantly increased the number of lambs born in flock 1 (P<0.01) but not in flock 2. Where a single injection of PMSG was used, failure to obtain a satisfactory lambing response was associated with a high incidence of 'silent heat' at the first induced ovulation, and a failure to promote regular sexual activity. No lambs were born in the untreated control groups until eight weeks after those of the treated groups.

MPA impregnated intravaginal sponges for the induction of oestrus in anoestrous Border Leicester × Merino ewes. 1. Lactating ewes

In the spring of 1965, anoestrous lactating Border Leicester X Merino ewes were treated for 13 days with intravaginal sponges impregnated with 17a - acetoxy 6a - methylpregn - 4 - ene - 3,20 - dione (MAP) 7-11 weeks after lambing. Each ewe received 1000 i.u. Pregnant Mare Serum Gonadotrophin (PMSG) at the time of sponge removal. Half of the ewes received another 1000 i.u. PMSG 16 days after sponge removal. In the 2-4 days after sponge removal 80.5 per cent of the treated ewes exhibited oestrus, and 75.8 per cent of these were pregnant at autopsy 15 weeks later. The mean number of foetuses per pregnant ewe was 2.46. It was not until approximately 15 weeks after the period of treatment that a similar number of untreated ewes had exhibited oestrus. The second injection of PMSG had no effect on either the number of ewes pregnant or on the number of foetuses present at autopsy. This was largely due to the high rate of conception at the first induced oestrus.

Pregnant mare serum gonadotrophin potency: effect of single and multiple injections.

IT has been demonstrated that a single subcutaneous injection of pregnant mare serum gonadotrophin (PMSG) is as effective as multiple injections of the same amount of PMSG on the weight increase of the immature rat ovary1,2. However, it was later shown that multiple injections of PMSG were more effective in producing an increase in testis weight of three-day-old cockerels than a single injection of the gonadotrophin3. Because of these opposing views, it was of interest to re-investigate the chick testis response with a more sensitive assay method.