The production of living sheep eggs

Abstract

1. In the 1954–5 and 1955–6 breeding seasons, 117 ewes of the Border Leicester, Welsh Mountain and Suffolk breeds were used in order to investigate the effects of PMS treatments on (a) the length of the dioestrous cycle, (b) the number of ovulations per ewe, (c) the proportion of eggs which were cleaved, uncleaved or abnormal when recovered, and (d) the ability of fertilized superovulated eggs to develop normally.2. In the 1954 and 1955 anoestrous periods, ninety-four 2-tooth and mature ewes of mixed breeds were used in order to investigate (a) the proportion of ewes which could be induced to ovulate and exhibit oestrus as a result of treatment with progesterone and PMS, (b) the proportion of the mated ewes which had cleaved, uncleaved or abnormal eggs, and (c) the ability of fertilized eggs shed during anoestrum to develop normally up to the 21st day of pregnancy.3. Dioestrous cycles in untreated ewes were significantly shorter for Welsh Mountain than for Border Leicester ewes, and their length was not affected by the year in which they were measured. The first and second cycles of the breeding season tended to be shorter than the third cycle.4. The length of the dioestrous cycle was shortened by treatment of both Border Leicester and Welsh Mountain ewes with PMS. The average extent of this reduction was 0·6 days, and the effect was significant.

Embryo transfer and related technologies in sheep reproduction

“…Pregnant mare serum gonadotrophin (PMSG) [6], pituitary extracts of different origin [28,69,96] and human menopausal gonadotrophin [92] are commonly used for superovulation in sheep. The biological properties of the gonadotrophins used for superovulation have been described in detail elsewhere [13]; for review see [45] [67] or later, during early embryonic development as a result of unbalanced hormonal profiles [3,51] [66], association of these two gonadotrophins [91], single versus multiple injections [30,64], or inclusion of GnRH or growth hormone in the treatments [36,111].…”

Transfer of Sheep Ova

“…296 J. L. Hancock and G. J. R. Hovell Management of the flocks and experimental procedures followed were based on the methods developed in the A.R.C. Unit of Reproductive Physiology and Biochemistry at Cambridge (Hunter, 1954;Hunter, Adams & Rowson, 1955;Averill & Rowson, 1958;Averill, 1958 Vasectomized ('teaser') rams marked with coloured raddle were used to detect the onset of oestrus ; the ewes were inspected twice daily for evidence of heat until the rams were removed about the end of January.…”

Egg Transfer in Sheep. Factors Affecting the Survival and Development of Transferred Eggs

“…In no case did any of these authors report more than 35% of ewes lambing following egg transfer. However, improve¬ ments in technique developed by Hunter, Adams & Rowson (1955), and used extensively by Averill ( 1958), Averill & Rowson ( 1958) and Moore & Rowson (1959), resulted in much higher survival rates of transferred eggs. Averill (1958) Recovery and transfer of eggs.…”

“…However, improve¬ ments in technique developed by Hunter, Adams & Rowson (1955), and used extensively by Averill ( 1958), Averill & Rowson ( 1958) and Moore & Rowson (1959), resulted in much higher survival rates of transferred eggs. Averill (1958) Recovery and transfer of eggs. The procedures adopted for the recovery and transfer of eggs were essentially those described by Hunter et al (1955).…”