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M. J. D'Occhio, D. R. Gifford, R. M. Hoskinson, T. Weatherly and B. P. Setchell

Summary. Groups of heifer calves received a primary immunization against androstenedione (Group A; N = 11) or oestradiol-17β (Group E; N = 10) at 3 months of age and booster injections on 5 occasions at 2- to 3-month intervals. Controls (Group C, N = 11) were immunized against human serum albumin alone using the same protocol. Immunity was achieved against both steroids as judged by the secondary antisteroid antibody titres in Group A (1126 ± 261; reciprocal of titre) and Group E (10 357 ± 4067) heifers. In Groups A and E there was a general decline in the respective peak antibody titres after successive booster injections. From 3 to 9 months of age mean plasma concentrations of LH were higher (P < 0·05) in Group E heifers (0·89 ± 0·08 ng/ml) than in Group C (0·46 ± 0·03 ng/ml) and Group A (0·59 ± 0·05 ng/ml) heifers which did not differ from one another. There were no differences between groups in plasma FSH concentrations. At 10 months of age the LH response to exogenous LHRH was of higher (P < 0·05) amplitude for heifers in Group E (2·59 ± 0·56 ng/ml) than for those in Groups C (0·61 ± 0·07 ng/ml) and A (1·04 ± 0·22 ng/ml). Elevated plasma progesterone concentrations at 5 months of age were shown by 2 heifers in Group C, 10 in Group A, and 6 in Group E. From 8 to 14 months of age a consistently higher proportion of Group A heifers exhibited elevated progesterone compared with Group C and Group E heifers. After ovarian synchronization and booster injection at 15 months of age a corpus luteum was present in 2 heifers in Group C, 7 in Group A and none in Group E. The ovaries of Group A heifers were different from those of Groups C and E and were characterized by greater numbers of 2–4 mm follicles. It is concluded that active immunization against gonadal steroids influences both LH secretion and ovarian function in prepubertal heifers. Early increases in ovarian activity in androstenedione-immunized heifers are maintained after puberty and may therefore confer some lifetime reproductive advantages.

Keywords: heifer; gonadal steroid immunization; gonadotrophins; puberty; ovary

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N. R. Adams, S. Atkinson, R. M. Hoskinson, J. A. Abordi, J. R. Briegel, M. Jones and M. R. Sanders

Summary. Ovariectomized ewes were immunized against cortisol, oestrogen or progesterone to determine whether steroids of non-ovarian origin occur in sufficient amounts to influence the reproductive system. Ewes immunized against oestrogen (oestrone + oestradiol) had smaller uteri (P < 0·05) and a lower concentration of oestradiol in uterine tissue (P < 0·05), while the adrenal gland was heavier (P < 0·05). In the peripheral plasma of immunized ewes, the concentration of FSH, but not LH, was increased (P < 0·05). Ewes immunized against cortisol also had smaller uteri (P < 0·05) and heavier adrenal glands (P < 0·05), but gonadotrophins and the concentration of oestradiol in the uterus were unaffected. Immunization against progesterone, or injection with synthetic glucocorticoids, did not affect any of the characteristics measured.

We conclude that the adrenal gland of the ewes produced sufficient oestrogen or aromatizable androgen to have significant effects on the reproductive system. In contrast, adrenal production of progesterone did not produce detectable biological effects. Immunization against cortisol did affect the reproductive system, but the mechanism of this action could not be determined.

Keywords: ewe; adrenal; uterus; steroids; gonadotrophins

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B. W. Brown, P. E. Mattner, P. A. Carroll, R. M. Hoskinson and R. D. G. Rigby

Groups of Merino ewe lambs were immunized against GnRH either soon after birth (prepubertal) or around puberty (peripubertal) with a prototype commercial preparation and were studied over the following 2 years to determine the long-term effects on reproductive development, function and hormone concentrations. At least 60% of the GnRH-immunized ewes in either treatment group did not experience oestrus and possessed small uteri and small ovaries that lacked follicular development. Growth rates of immunized and control ewes were similar throughout the study. Compared with the increase in plasma LH and FSH concentrations with age in control ewes, the concentrations of these hormones in immunized animals were lower and remained relatively constant from 46 to 90 weeks of age. Plasma FSH concentrations were particularly suppressed in immunized ewes and were significantly (P < 0.05) lower than the control values of 61 and 90 weeks of age. LH release after injection of 1 μg GnRH at 90 weeks of age was either absent or suppressed in immunized ewes compared with controls. The findings suggest that the lack of GnRH stimulation and consequent deprivation of gonadotrophins, early in the life of ewes, may result in some degree of permanent impairment of hypothalamic and/or pituitary function.

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M. P. Boland, C. D. Nancarrow, J. D. Murray, R. J. Scaramuzzi, R. Sutton, R. M. Hoskinson and I. G. Hazelton

Summary. Ewes were immunized against androstenedione (Fecundin) and assigned to be mated 14 days (179 ewes Group C) or 25 days (174 ewes Group B) after a booster immunization with Fecundin. The anti-androstenedione titres at these times were 6790 and 3240 respectively (P < 0·01). The remaining 169 ewes were untreated controls (Group A). Ewes were mated to entire rams (12 rams to 180 ewes) at their second oestrus after synchronization of oestrus. Immunization against androstenedione caused a shortening of the time from sponge removal to mating (Day 0) and a decrease in the percentage of ewes mated by the rams. Also, ovulation rate was increased after immunization (P < 0·01),being 1·42, 2·16 and 1·93 for Groups A, C and B respectively.

Egg recovery rates on Day 2 were lower in immunized ewes and there was some indication that fertilization rates were lowered. On Day 13 after mating a higher proportion of blastocysts was recovered from ewes in Group A than from those in Groups B and C. Immunization resulted in lower fertilization rates and smaller blastocysts with lower mitotic indexes (P < 0·01). At Days 24–32 of pregnancy fetal weight was lower in the immunized ewes. At all sampling stages, the proportion of ewes pregnant (fertility) was lowered in immunized ewes.

The results of the present study show that significant reproductive wastage occurs in androstenedione-immunized Merino ewes, with lower rates of embryo recovery and delayed embryonic development being found in comparison to controls. Despite increases in ovulation rate of 36–52% in Fecundin-treated ewes, the number of fetuses obtained per ewe mated decreased from 1·00 (control, Group A) to 0·89 (Group B) and to 0·69 (Group C). Higher titres of androstenedione antibody were associated with higher reproductive wastage.

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J. D. Murray, C. Moran, M. P. Boland, C. D. Nancarrow, R. Sutton, R. M. Hoskinson and R. J. Scaramuzzi

Summary. Cytogenetic examination was made of 103 13–14-day-old blastocysts and 116 24–32-day-old fetuses from untreated and androstenedione-7–HSA-immunized Merino ewes. There were no differences in the chromosome composition of blastocysts or fetuses from treated or untreated ewes and so the data were combined. At Days 13–14 a 1N/2N mosaic and a 2N – 1/2N/4N mosaic embryo were observed. In addition, 52 of the blastocysts were 2N/4N mosaics, with 8 of these also containing 8N cells, and one blastocyst was a 2N/8N mosaic. No aneuploid fetuses were observed, but 80 of the 116 fetuses contained polyploid cells, including 4N, 6N and 8N cells. The polyploid cells observed in the blastocysts and fetuses should not be considered as abnormal cells as they appear to be a normal part of the developmental processes leading to trophoblast formation and fetal differentiation.

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J. D. Murray, M. P. Boland, C. Moran, R. Sutton, C. D. Nancarrow, R. J. Scaramuzzi and R. M. Hoskinson

Summary. Chromosome counts were obtained from 73 out of 177 (41%) early cleavagestage Merino embryos. A further 13 embryos were classified as probably diploid. Chromosome aberrations were found in 8 (11%) embryos, one of which was aneuploid and the remainder (9·6%) had euploid abnormalities. If the probable diploid embryos are included, the incidence of euploid aberrations falls to 8·1% Of the abnormal embryos there was one aneuploid with 2N = 55, two haploids, four haploid/diploid mosaics and one zygote with 4 haploid metaphase plates. Two additional zygotes had 4 interphase pronuclei. Four of the euploid abnormalities were attributable to the entry of two or more spermatozoa and therefore polyspermy is the largest single factor leading to chromosomally aberrant embryos in this population of Merino ewes.

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M. J. D'Occhio, D. R. Gifford, R. M. Hoskinson, T. Weatherly, P. F. Flavel, P. E. Mattner and B. P. Setchell

Summary. Groups of bull calves received a primary immunization against testosterone (Group T; N = 7) or oestradiol-17β (Group E; N = 9) at 3 months of age and booster injections on four occasions at ∼2 month intervals. Controls (Group C, N = 7) were immunized against human serum albumin alone using the same protocol. Immunity was achieved against both steroids as judged by the secondary antisteroid antibody titres in Group T (730 ± 231; reciprocal of titre) and Group E (12 205 ± 4366) bulls; however, peak antibody titres generally declined with successive booster injections. Mean plasma concentrations of LH, FSH and testosterone during the period from 3 to 10 months of age were higher (P < 0·05) in Group T bulls than in Groups C and E. Group T bulls had larger testes compared with controls from 6 months of age onwards. At castration at 14 months of age, testes of Group T bulls were heavier (P < 0·05) than those of Groups C and E (179 ± 13, 145 ± 8 and 147 ± 6 g, respectively). At 10 months of age, there were no differences among treatment groups in LH responses to LHRH, but the testosterone responses were greater (P < 0·05) in bulls in Group T (26·2 ± 4·9 ng/ml) and Group E (16·6 ± 1·8 ng/ml) compared with those in Group C (6·9 ± 0·6 ng/ml). Testosterone responses to hCG determined at 13 months of age were also greater (P < 0·05) in Groups T and E relative to controls. At 14 months of age daily sperm production rates per bull (× 10−9) were higher (P < 0·10) in Group T bulls (2·2 ± 0·1) than those in Groups C (1·6±0·2) and E (1·6±0·1). These results indicate that early immunity against testosterone is associated with increased gonadotrophin secretion and accelerated growth of the testes in prepubertal bulls. Also, chronic immunity against testosterone or oestradiol-17β enhances the steroidogenic response of bull testes to gonadotrophic stimulation. If the above responses observed in young bulls are shown to be sustained, then immunity against gonadal steroids early in life may confer some reproductive advantage in mature animals.

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B. W. Brown, P. E. Mattner, P. A. Carroll, E. J. Holland, D. R. Paull, R. M. Hoskinson and R. D. G. Rigby

Groups of Merino ram lambs were immunized against GnRH either soon after birth (prepubertal) or around puberty (peripubertal) with a prototype commercial preparation and studied over the following 2 years to determine the long-term effects of such immunization on reproductive development, function and hormone concentrations. The treatment was equally effective in suppressing reproductive function and hormones when given at either time. Growth rates of immunized and controls rams were similar throughout the study. Prepubertal immunization delayed testicular growth until the rams were at least 27 weeks of age and some rams had subnormally sized testes even at 115 weeks of age. After peripubertal immunization, the mass of the testes declined and remained regressed until the rams were from 51 to 90 weeks old. There was a significant correlation between total testicular mass at 115 weeks of age and duration (weeks) of suppression of testicular growth (prepubertal, r= −0.7375; peripubertal, r= −0.7132, P < 0.001). Prepubertal immunization markedly delayed separation of the penis from the prepuce. The immunized rams did not display sexual activity until their total testicular mass reached at least 70 g. In control and immunized rams with testicular mass > 100 g, the semen did not differ in the percentage of spermatozoa that were unstained (live), of normal morphology, or showed progressive movement. Compared with the increase in plasma LH and FSH concentrations with age in control rams, the concentrations of these hormones in the immunized animals were lower and remained relatively constant from 46 to 90 weeks of age. Plasma FSH concentration was particularly suppressed in immunized rams and was significantly (P< 0.05) lower than the control values at 61 and 90 weeks of age. LH release after injection of 1 μg GnRH at 90 weeks of age was either absent or markedly suppressed in immunized rams compared with that for controls.