The transport of spermatozoa in spayed ewes is grossly impaired in comparison with that observed in entire animals (Allison, 1972). Although hormonal replacement regimens used resulted in a behavioural oestrus of similar duration to that recorded in entire ewes, the physiological state of the uterus was not maintained. These differences could be a result of the pattern of steroid release following single intramuscular injections. In particular, the pattern of oestrogen release following a single intramuscular injection is unlikely to resemble the patterns recorded in the entire ewe before and about the time of oestrus (Moore, Barrett, Brown, Schindler, Smith & Smyth, 1969; Smith & Robinson 1970). If the release of steroids in entire ewes could be reproduced precisely by intravenous infusion, normal transport of spermatozoa might be attainable in spayed ewes. The aim
A. J. ALLISON
The pattern of transport of spermatozoa in spayed ewes treated with 10 mg progesterone for 12 days followed by 24 μg ODB was compared with that in entire animals at two times of recovery following artificial insemination or natural mating. Spayed ewes had fewer spermatozoa in all sections of the tract than did entire ewes for all treatment combinations. The numbers recovered from the cervix and vagina were higher at 2 than at 24 hr after insemination, while the converse was true for the Fallopian tubes. More spermatozoa were recovered from the Fallopian tubes of naturally mated than of artificially inseminated ewes but the difference was not evident in other regions of the tract. Histological examination of the uterine endometrium indicated an early stage of atrophy in the spayed ewes. Thus, hormonal regimens which will induce behavioural oestrus of `normal' dimensions in spayed ewes will not maintain the functional integrity of the uterus and the transport of spermatozoa within the tract is grossly impaired.
A. J. ALLISON and T. J. ROBINSON
Eighty spayed ewes were used in a 4 × 4 factorial experiment (n = 5) in which four doses of oestradiol benzoate (0, 12·5, 25 and 50μg) were administered 48 hr after four progesterone regimens (0, 5, 10 and 20 mg/day for 12 days). Each ewe was inseminated 24 hr later with 0·15 ml undiluted semen (≥500 ×106 spermatozoa). After a further 24 hr, the ewes were slaughtered and the vagina, cervix, uterus and Fallopian tubes were flushed for spermatozoa. The population of spermatozoa in the cervix was highly dependent upon oestrogen (P<0·001) and appeared to be related to dose (P=0·1). There was no significant mean effect of progesterone but there was a significant interaction with oestrogen (P<0·05). High numbers of spermatozoa were associated with high doses of oestrogen and of progesterone. The numbers of spermatozoa in the vagina were not related to oestrogen and there was no relationship with the numbers in the cervix (r = −0·011). Penetration and maintenance of a cervical population of spermatozoa was related to the level of oestrogen and full expression required adequate progesterone influence preceding that of oestrogen.
J. F. SMITH and A. J. ALLISON
The volume of cervical mucus produced in the ewe appears to be controlled by the circulating levels of oestrogen (Vickery & Bennett, 1968), and is greatest during pro-oestrus and oestrus (Grant, 1934). The volume produced is of the order of 20 ml (Restall, 1967) and in spayed ewes is a linear function of the quantity of exogenous oestrogen (Lindsay & Francis, 1968).
It seems, therefore, that the disturbance in the pattern of oestrogen production in the ewe in which oestrus is controlled with progestagen-impregnated sponges (Smith & Robinson, 1970) may be reflected in the production of cervical mucus and that this could account for the changed pattern of transport of spermatozoa following progestagen treatment (Quinlivan & Robinson, 1967, 1969).
Forty-five Merino ewes, aged 5 years, randomized into three progestagen-dose-level groups of fifteen ewes
A. J. ALLISON and T. J. ROBINSON
The numbers of spermatozoa recovered from the Fallopian tubes 24 hr after insemination, fertilization rate and lambing were measured in one group of 120 normal cyclic ewes and in three groups of 120 animals which had been synchronized with intravaginal sponges impregnated with 10, 30 or 90 mg Cronolone (Searle). Half of each group received 500 i.u. pmsg. Results were as follows:
pmsg had no apparent effect on any one of the three parameters. Increasing dose of progestagen significantly increased the incidence of oestrus and was associated with an increasing ovarian response to pmsg. There was no evidence that embryonic mortality was greater in progestagen-treated than in untreated ewes.
Considering all parameters of fertility, ewes treated with intravaginal sponges containing 10 mg Cronolone yielded the fewest spermatozoa, the lowest number and percentage of fertilized eggs and the lowest percentage of lambing ewes.
Leticia E Camacho, Allison M Meyer, Tammi L Neville, Carolyn J Hammer, Dale A Redmer, Lawrence P Reynolds, Joel S Caton and Kimberly A Vonnahme
To investigate the effects of maternal selenium (Se) supplementation and nutritional intake during gestation on hormone changes, percentage body weight (BW) change, and organ mass in neonatal lambs, ewes were allocated to differing Se levels (adequate Se (ASe, 11.5 μg/kg BW) or high Se (HSe, 77.0 μg/kg BW)) initiated at breeding and nutritional intake (60% (RES), 100% (CON), or 140% (HIGH) of NRC requirements) initiated at day 40 of gestation. At parturition, all lambs were removed from dams, fed common diets, and BW and blood samples were collected until day 19. There was a Se×nutritional intake×day interaction for percentage BW change from birth. Lambs born to ASe-HIGH ewes tended to have decreased BW change compared with ASe-CON and ASe-RES groups on day 7. Lambs from HSe-HIGH ewes tended to have increased BW change compared with HSe-RES and HSe-CON groups from days 7 to 19. At birth, there was a Se×sex of offspring interaction, in which male lambs from HSe ewes had decreased cortisol concentrations compared with all other lambs. By 24 h, lambs from RES ewes had decreased cortisol compared with those from HIGH ewes, with lambs from CON ewes being intermediate. Lambs from RES- and CON-fed ewes had greater thyroxine than HIGH ewes at 24 h. Organ masses on day 19 were mainly impacted by maternal nutritional intake and sex of the offspring. Birth weight alone did not predict growth performance during neonatal life. Moreover, despite a similar postnatal diet, maternal nutritional plane and Se status did impact neonatal endocrine profiles. Exact mechanisms of how neonatal endocrine status can influence later growth and development need to be determined.