Embryo transfer in the Angora goat

Abstract

A total of 711 embryos was collected from 121 Angora does mated to Angora bucks. They were transferred to 667 feral recipient does, of which 361 kidded, producing 378 kids. Donors were treated with 36, 40 or 45 mg of an equine anterior pituitary extract (HAP) or 1500 i.u. pregnant mare serum gonadotrophin (PMSG) given at the end of a period of progesterone treatment (12 mg/day by intramuscular injection), while the recipients were either untreated, or their time of oestrus was controlled by progestagen-impregnated intravaginal pessaries or by the prostaglandin analogue 'Estrumate' (I.C.I.). All 121 donors exhibited oestrus after treatment, and 104 (86%) were in oestrus 48–60 h after the final injection of progesterone. Donors were naturally mated by allowing them free access to bucks, hand-mated at 12-h intervals, surgically inseminated into the uterus, or inseminated into the cervix; and in does treated with HAP the proportion of recovered eggs fertilized were respectively 88, 79, 65 and 32%. Seven does received PMSG. They were all hand-mated, and 46% of eggs recovered were fertilized. The mean numbers of corpora lutea in does treated with HAP and PMSG were 10.4 ± 0.9 and 13.7 ± 2.2, and it is suggested that the low rate of fertilization following PMSG was due to an excessive ovulatory response. Treatment with pessaries and Estrumate effectively controlled the time of oestrus in recipients and, overall, there was little difference between the proportions of treated and untreated recipients which kidded (58 v. 50% recipients kidded). Embryos were recovered from donors 3½–5½ days after they were first observed in oestrus, and they were transferred to recipients first observed in oestrus 48 h before to 48 h after their respective donors. The kidding rate of does which received day 3½ embryos was less than that of those which received older embryos (28 v. 55%), but the degree of asynchrony between respective donors and recipients had no effect upon survival.