76 Effect of season on the superstimulation response, embryo quality, and pregnancy establishment in dromedary camel (Camelus dromedarius)

2021 ◽  
Vol 33 (2) ◽  
pp. 146
Author(s):  
H. A. Abouhefnawy ◽  
N. A. Wani
Keyword(s):  
Breeding Season ◽  
Embryo Quality ◽  
Treatment Protocol ◽  
Uterine Horn ◽  
Dromedary Camel ◽  
Corpora Lutea ◽  
Dromedary Camels ◽  
Nonbreeding Season ◽  
Single Intramuscular Injection ◽  
The Mean

The present study was conducted to study the effect of season on the superstimulation response, embryo quality and pregnancy establishment in the dromedary camels. Two donors each were superstimulated in the month of June 2019 (non-breeding season) and January 2019 (breeding season) by a combination of 2500IU of equine chorionic gonadotrophin (eCG, Folligon; Intervet), given as a single intramuscular injection on Day 1 of the treatment protocol, and 400mg of pFSH (Folltropin; Bioniche) injected twice daily in declining doses of 2×80mg, 2×60mg, 2×40mg, and 2×20mg over 4 days, also beginning on Day 1. They were scanned by rectal ultrasonography and follicles counted before mating with a fertile bull on Day 11 after the start of treatment. An injection of 20µg of gonadotrophhin-releasing hormone (Receptal, Intervet) was given immediately after mating to induce ovulation. The number of corpora lutea (CL) were counted, and the embryos collected by the non-surgical method on Day 7 after ovulation. All embryos were washed and graded before they were transferred individually into the left uterine horn of recipient animals, synchronized to be on Day 6 after ovulation. All recipients were screened by ultrasonography on Day 22, Day 60, and Day 90 for pregnancies. The data were analysed using a two-sample t-test (Minitab statistical software, Minitab Ltd.). No difference was observed in the mean number of follicles developed (20.5 vs. 18.5) between the donors in breeding and non-breeding season, respectively. The percent mean±s.e.m. of ovulations as observed by counting the CL in nonbreeding season (80.7±3.4) were not different from those in breeding season (85.4±3.7). A total number of 16 embryos collected during non-breeding season and 20 embryos in breeding season were transferred to recipients. The percent mean±s.e.m. of pregnancies established on Day 22 (56.6±3.4 vs. 67.5±7.5) and on Day 90 (47.2±2.8 vs. 60±0.0) were similar in both groups. These observations indicate that embryo transfer technology can be applied to camels during the summer months, which is considered the non-breeding season, and pregnancies can be established at par with breeding season. In conclusion, to the best of our knowledge, this is the first study in camels wherein we have demonstrated that donor camels can be superstimulated, embryos can be collected, recipient animals can be synchronized, and pregnancies can be established in the summer (non-breeding) months. The embryos collected from elite donors can be transferred to synchronized recipients to establish pregnancies or preserved for future use. Some owners do not want calves to be born in summer months, so protocols need to be established for storing these embryos for a few months before their transfer to recipients, to have the calves delivered in the desired winter months.

scholarly journals Testicular expression of NGF, TrkA and p75 during seasonal spermatogenesis of the wild ground squirrel (Citellus dauricus Brandt)

2015 ◽  
Vol 59 (3) ◽  
Author(s):  
H. Zhang ◽  
Y. Wang ◽  
J. Zhang ◽  
L. Wang ◽  
Q. Li ◽  
...  
Keyword(s):  
Breeding Season ◽  
Sertoli Cells ◽  
Seasonal Changes ◽  
Ground Squirrel ◽  
Leydig Cells ◽  
Testicular Function ◽  
Nonbreeding Season ◽  
Function Change ◽  
The Mean ◽  
Neuronal Systems

The nerve growth factor (NGF) not only has an essential effect on the nervous system, but also plays an important role in a variety of non-neuronal systems, such as the reproductive system. The aim of this study was to investigate the seasonal changes in<strong> </strong>expression of NGF and its receptors (TrkA and p75) in testes of the wild ground squirrel during the breeding and nonbreeding seasons.<strong> </strong>Immunolocalization for NGF was detected mainly in Leydig cells and Sertoli cells in testes of the breeding and nonbreeding seasons. The immunoreactivity of TrkA was highest in the elongated spermatids, whereas p75 in spermatogonia and spermatocytes in testes of the breeding season. In the nonbreeding season testes, TrkA showed positive immunostainings in Leydig cells, spermatogonia and primary spermatocytes, while p75 showed positive signals in spermatogonia and primary spermatocytes. Consistent with the immunohistochemical results, the mean mRNA and protein level of NGF and TrkA were higher in the testes of the breeding season, and then decreased to a relatively low level in the nonbreeding season. In addition, the concentration of plasma gonadotropins and testosterone were assayed by radioimmunoassay (RIA), and the results showed a significant seasonal change between the breeding and nonbreeding seasons. To conclude, these results of this study provide the first evidence on the potential involvement of NGF and its receptor, TrkA and p75 in the seasonal spermatogenesis and testicular function change of the wild ground squirrel.

407 SUPERSTIMULATORY RESPONSE WITH DECREASING DOSES OF FOLLICLE-STIMULATING HORMONE v. A SINGLE DOSE OF FOLLICLE-STIMULATING HORMONE - EQUINE CHORIONIC GONADOTROPIN DURING BREEDING AND NONBREEDING SEASON IN SHEEP

2010 ◽  
Vol 22 (1) ◽  
pp. 360
Author(s):  
M. I. Cueto ◽  
F. Pereyra-Bonnet ◽  
P. Silvestre ◽  
A. E. Gibbons
Keyword(s):  
Single Dose ◽  
Breeding Season ◽  
Recovery Rate ◽  
Follicle Stimulating Hormone ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Nonbreeding Season ◽  
Embryo Recovery ◽  
The One ◽  
Stimulating Hormone

The aim of the study was to assess possible variations in superovulatory yields due to different FSH treatments at 2 times of the year. Superovulation and embryo recovery were performed during the breeding (n = 63) andnonbreeding (n = 46) seasons in Merino ewes located at 41°S latitude. Animals were kept under the same conditions, housed outdoors in a sheltered and covered pen, and were fed a liveweight maintenance ration. All animals received 60-mg medroxyprogesterone acetate intravaginal sponges (Progespon®, Syntex, Buenos Aires, Argentina) for 14 days. Ewes were then randomly assigned to 2 different superovulatory treatments: classic (n = 74) and one shot (n = 35) in both seasons. Classic superovulatory treatment consisted of 7 decreasing doses (2 × 48 mg, 2 × 24 mg, 2 × 20 mg, and1 × 16 mg NIH-FSH-P1)ofFSH (Folltropin®-V, Bioniche, Belleville, Ontario, Canada), administered twice daily from 48 h before to 24 h after pessary removal. A dose of eCG (300 IU; Novormon®, Syntex) was administered at progestagen removal. One shot superovulatory treatment consisted of a single dose of FSH (70 mg NIH-FSH-P1) plus 300 UI of eCG injected at pessary withdrawal. Embryo donors were inseminated by laparoscopy with frozen-thawed semen (100 × 106 spz) 12 h after the onset of estrus. Surgical embryo recovery was done on Day 7 after sponge withdrawal and embryos were graded for quality according to morphology (Grade 1 = excellent or good; Grade 2 = fair; Grade 3 = poor; and Grade 4 = dead or degenerated; IETS 1998). A 2 × 2 factorial ANOVA was used to test the main effects (season and superovulatory treatment) and interactions. There were no significant differences in the proportion of responding ewes (>3 corpora lutea), ovulation rate, and recovered Grades 1 to 2 embryos between the breeding and nonbreeding season (Table 1; P > 0.05). However, number of recovered ova/embryos and ova/embryo recovery rate were higher during the breeding season compared with the nonbreeding season, whereas the percentage of nonfertilized ova was lower in the breeding season than in the nonbreeding season (P < 0.05). Analysis of data comparing superovulatory treatments showed that the proportion of responding ewes, ovulation rate, recovered embryos, and recovered Grades 1 to 2 embryos were lower for the one shot treatment than for the classic treatment (P < 0.05). Embryo recovery rate and nonfertilization rate did not differ between treatments (P > 0.05). It was concluded that there was an increase in the number of total recovered ova/embryos during the breeding season compared with the nonbreeding season, although the number of recovered good-quality embryos was not affected. The use of multiple FSH injections produced a higher number of total recovered and viable embryos in Merino sheep than the one shot superovulatory treatment. Table 1.Embryo yields in ewes submitted to superovulation

240 RELATIONSHIP BETWEEN PEAK NUMBER OF ANTRAL FOLLICLES AND FOLLICULAR WAVES, HORMONE CONCENTRATIONS, SUPEROVULATORY RESPONSE, AND EMBRYO QUALITY IN BEEF HEIFERS

2006 ◽  
Vol 18 (2) ◽  
pp. 228 ◽  
Author(s):  
F. Ward ◽  
P. Lonergan ◽  
F. Jimenez-Krassel ◽  
J. J. Ireland ◽  
A. C. O. Evans
Keyword(s):  
Recovery Rate ◽  
Embryo Quality ◽  
Corpora Lutea ◽  
Beef Heifers ◽  
High Group ◽  
Estrous Cycles ◽  
Antral Follicles ◽  
Peak Number ◽  
Follicular Waves ◽  
The Mean

Recent studies in dairy cattle demonstrate that the number of antral follicles during follicular waves is highly variable among animals, but highly repeatable within individuals, and the numbers of follicles during waves are inversely associated with serum FSH concentrations (Burns et al. 2005 Biol. Reprod. 73, 54-62). The aims of this study were to determine (1) serum FSH and estradiol concentrations during follicular waves in beef heifers categorized according to peak number of antral follicles per wave, and (2) the relationship between this categorization and superovulatory response. Estrous cycles of crossbred beef heifers (n = 90) were synchronized with two i.m. injections of PGF2� 11 days apart; animals were scanned daily for 5 days beginning 24 h after the second PG injection to determine the number of follicles during the first follicle wave in two or three consecutive estrous cycles. Heifers were grouped based on the peak number of follicles e 3 mm per wave in diameter (Low: d 15 follicles, n = 12; High: e 25 follicles, n = 11). Intermediate animals were excluded. Heifers were then re-synchronized and blood samples taken every 8 h up to Day 7 to characterize FSH and estradiol profiles. Subsequently, animals were superovulated (pFSH, Folltropin�; Bioniche Animal Health, Belleville, Ontario, Canada), inseminated, and flushed on Day 7; this procedure was repeated twice. All values for hormone concentrations were aligned relative to the peak FSH value. A mixed model, repeated-measures approach was used to determine if serum FSH and estradiol concentrations were different between groups. Differences in recovery rate (number of oocytes/embryos recovered compared to number of corpora lutea) and proportion of transferable embryos were analyzed using Chi-square analysis. The mean (�SE) peak postovulatory FSH concentration was lower (P d 0.03) for animals with high numbers of follicles. No differences in estradiol concentrations were observed. The mean superovulatory response (number of corpora lutea) was higher (P d 0.05) in the High group than in the low group (17.6 � 3.6 vs. 8.5 � 1.1). While there was no difference in the recovery rate of embryos (62 vs. 60%), significantly more (P d 0.05) oocytes/embryos (10.6 � 2.7 vs. 4.7 � 0.7) and transferable embryos (5.4 � 1.3 vs. 3.8 � 0.8) were recovered per animal in the High group. Of the embryos recovered, the proportion of transferable quality was higher for animals in the Low group (80 vs. 51%; P d 0.05). In conclusion, the number of antral follicles during a follicular wave in beef heifers is inversely related to peak postovulatory FSH concentration, but is unrelated to estradiol concentration. In addition, while the superovulatory response and number of transferable embryos were greater in animals with a high number of antral follicles, embryo quality, measured as the proportion of transferable embryos per donor, was reduced. We conclude that cattle with relatively high numbers of follicles per wave respond best to standard superovulation protocols. However, the reason the proportion of high quality embryos is reduced in cattle with high vs. low numbers of follicles per wave is unknown.

Reproduction in a laboratory colony of the marsupial mouse Sminthopsis larapinta (Mardupialia : Dasyuridae)

1969 ◽  
Vol 17 (4) ◽  
pp. 637 ◽  
Author(s):  
GK Godfrey
Keyword(s):  
Breeding Season ◽  
Maximum Size ◽  
Urogenital Sinus ◽  
Corpora Lutea ◽  
Young Females ◽  
The Third ◽  
Laboratory Colony ◽  
The Mean ◽  
Mean Cycle ◽  
North Western

A laboratory colony of S. larapinta was established with three females and four males received from north-western Queensland. Over a period of two and a half years 109 young were born and second-generation descendants were produced. In the third breeding season oestrous cycles were irregular and, in the few instances where copulation was recorded, this was associated with almost 100% prenatal mortality. The colony became extinct without the cause being definitely established. In Adelaide S. larapinta had a well-defined breeding season with all females either pregnant or in oestrus from July to February. From March until June all the females were in anoestrus. The males produced sperm throughout the year. A technique was developed for determining the length of the oestrous cycle, based upon the incidence of epithelial cells in the urine. S. larapinta is polyoestrous, with a mean cycle length of 26.25�0.5 days. Gestation occupies 12.5 days, and a maximum of eight young remain in the pouch, attached to the teats, for 40 days. They are suckled in the nest for a further 30 days. Weaning takes place at 70 days, and the young females come into oestrus from 4 months of age onwards. Twenty female reproductive tracts were sectioned and examined and the anatomy and histology described briefly. The mean number of ova shed per ovulation was 30.6 (n = 12) with one instance of 40. The corpora lutea are formed rapidly, and reach their maximum size towards the end of pregnancy. They have completely regressed by the seventh week of lactation. The young are born through a pseudovaginal canal which extends from the median vagina to the urogenital sinus. This closes within 24-48 hr of parturition. The high "pre-pouch" and litter mortality observed during this study is discussed.

MAINTENANCE OF PREGNANCY RELATIVE TO THE PRESENCE OF FEW EMBRYOS IN THE RABBIT

1970 ◽  
Vol 48 (2) ◽  
pp. 243-249 ◽  
Author(s):  
C. E. ADAMS
Keyword(s):  
Pregnancy Rate ◽  
Follicle Stimulating Hormone ◽  
Uterine Horn ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
The Mean ◽  
Stimulating Hormone

SUMMARY Either one or two 60-h morulae were transferred to one uterine horn of Polish, Dutch or Strain A rabbits in which the mean number of ovulations was 4·3, 6·4 and 10·8. The pregnancy rate, as determined by palpation on day 10, varied from 45–65% (mean 53%) in recipients of one egg to 69–71% with two eggs. Only 20% of the does carrying one foetus maintained pregnancy to term compared with 87% of those with two implants. If pregnancy failed this usually occurred between days 15 and 20. In a further experiment, in which additional eggs were transferred to the contralateral horn, it was shown that all single conceptuses were inherently capable of surviving to term. It is concluded that irrespective of breed and ovulation rate, two conceptuses are normally required to prevent regression of corpora lutea on about day 17. Treatment with follicle-stimulating hormone in mid-pregnancy or removal of the barren uterine horn on day 13 failed to maintain pregnancies involving only one conceptus.

Immunohistochemical and Ultrastructural Features of the Seasonal Changes in the Epididymal Epithelium of Camel (Camelus dromedarius)

2019 ◽  
Vol 25 (05) ◽  
pp. 1273-1282 ◽  
Author(s):  
Dalia Ibrahim ◽  
Fatma M. Abdel-Maksoud
Keyword(s):  
Epithelial Cells ◽  
Breeding Season ◽  
Connexin 43 ◽  
Reproductive Activity ◽  
Dromedary Camel ◽  
Apical Region ◽  
Principal Cells ◽  
Nonbreeding Season ◽  
Apical Cells ◽  
Cx 43

AbstractIn order to evaluate the influence of reproductive activity on the functional role of the epididymal epithelium in the Egyptian dromedary camel, Connexin-43 (Cx-43), vascular endothelial growth factor (VEGF), and androgen receptor (AR) immunoreactivity in the epididymal epithelium and the fine structure of the principal, dark, basal, apical, and halo cells were investigated. The secretory activity of the principal cells was amplified in the breeding season, while its endocytotic function became more active in the nonbreeding season. This was evidenced by punctate strong immunoreactive signals for Cx-43, which appeared to be more intense in the apical region of these epithelial cells, and the extremely long slender stereocilia (microvilli) with multiple junctional complexes. The nonbreeding principal cells revealed granular immunoreactive signals for VEGF scattered in the apical and basal cytoplasm. Ultrastructurally, both extreme vacuolation and several multivesicular inclusion bodies were observed in their cytoplasm. Dark cell size greatly diminished in the nonbreeding season and their nuclear morphology greatly changed from oval to lobulated shape. The plasma membrane of the apical cells expressed several infoldings (microvilli) in the breeding season. However, it was almost smooth in the nonbreeding season except for a small microvillus that appeared as a bleb-like projection. In some regions, a strong dense immunoreactivity for VEGF could be recognized in the cytoplasm of the apical cells and some basal ones. Halo cells with numerous multivesicular inclusions occupying most of the cytoplasm and a lobulated eccentric nucleus were detected in the nonbreeding season. In conclusion, these findings indicate that the reproductive activity has a significant impact on the immunohistochemical and ultrastructural profiles of the epithelial cells lining the Egyptian dromedary camel epididymis.

73 Use of embryo transfer technology to salvage the germplasm of elite dromedary camels (Camelus dromedarius) infected with brucellosis

2021 ◽  
Vol 33 (2) ◽  
pp. 144
Author(s):  
H. A. Abouhefnawy ◽  
N. A. Wani
Keyword(s):  
Embryo Transfer ◽  
Treatment Protocol ◽  
P Value ◽  
Dromedary Camels ◽  
Single Intramuscular Injection ◽  
Gonadotrophin Releasing Hormone ◽  
And Control ◽  
Experimental Group ◽  
Fertile Male ◽  
Group 1

The present study was conducted to evaluate the potential of embryo transfer technology to salvage invivo-produced embryos from elite dromedary camels infected with brucellosis without transmission of the pathogen to the recipients or offspring. Ten elite racing champions who tested positive for brucella comprised the experimental group, whereas 3 donors negative for brucella acted as the control. Each donor animal received a combination of 2500IU of equine chorionic gonadotrophin (eCG; Folligon; Intervet), given as a single intramuscular injection on Day 1 of the treatment protocol, and 400mg of pFSH (Folltropin; Bioniche), injected twice daily in declining doses of 2×80mg, 2×60mg, 2×40mg, and 2×20mg over 4 days, also beginning on Day 1. They were mated with a fertile bull on the 11th day after the start of treatment. The donors of the group 1 received a combination of tetracycline, and streptomycin on alternate days for 2 weeks before mating with a fertile male. An injection of 20µg of gonadotrophin-releasing hormone (Receptal, Intervet) was given to them immediately after mating to induce ovulation. The embryos were collected by the non-surgical method on Day 7 day after ovulation as per the guidelines published by IETS. All embryos were washed at least 3 times in holding medium supplemented with antibiotics and then transferred individually into the left uterine horn of synchronized recipients. All recipients and calves born were tested for brucellosis every 3 weeks. The data were analysed using a two-sample t-test (Minitab statistical software, Minitab Ltd.). Results are shown in Table 1. No difference was observed in the number of embryos collected per flushing and pregnancies established at Day 60. The proportion of pregnancies reaching term from the total number of embryos transferred and from the pregnancies established on Day 60 did not differ from embryos obtained from brucella-infected and control donors. All recipients tested negative for brucellosis during their gestation and until weaning. All calves born were also negative for brucellosis on birth and until weaning and handing over to clients. In conclusion, this is the first study in camels wherein we have demonstrated that invivo-produced embryos from elite dromedary females infected with brucellosis could be collected and transferred to synchronized recipients without transmitting the pathogen to the recipients or offspring. Table 1. Pregnancies established from invivo-produced embryos collected from elite dromedary camels infected with brucellosis Donor group (N) Total number of flushings No. of embryos collected per flushing (n±s.e.m.) Pregnancies on Day 60 (% mean±s.e.m.) Pregnancies reaching term (% mean±s.e.m.) from: Embryos transferred Pregnancies on Day 60 Brucella (10) 30 5.4±0.6 55.1±2.6 44.4±2.3 83.2±3.6 Control (3) 6 5.3±0.6 65.7±6.3 53.3±6.8 80.9±7.7 P-value 0.969 0.173 0.262 0.797

scholarly journals 63 Chronic Femoral Osteomyelitis Case Series: Outcomes and Economic Impact at A United Kingdom Based Tertiary Centre

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
E Lau ◽  
Z Arshad ◽  
A Aslam ◽  
A Thahir ◽  
M Krkovic
Keyword(s):  
Economic Impact ◽  
Treatment Protocol ◽  
Case Series ◽  
Consecutive Series ◽  
Financial Loss ◽  
Patient Demographics ◽  
Tertiary Centre ◽  
The Mean ◽  
Eq Vas

Abstract Introduction Osteomyelitis refers to an inflammatory process affecting bone and bone marrow. This study reviews chronic femoral osteomyelitis treatment and outcomes, including economic impact. Method We retrospectively collected data from a consecutive series of 14 chronic femoral osteomyelitis patients treated between January 2013 and January 2020. Data collected include patient demographics, comorbidities, pathogens, complications, treatment protocol and costs. Functional outcome was assessed using EuroQOL five-dimensional interview administration questionnaire (EQ-5D-5L™) and EuroQOL Visual Analogue Scale (EQ-VAS™). Results Of these, 92.9% had one or more osteomyelitis risk factor, including smoking and diabetes. Samples from 78.6% grew at least one pathogen. Only 42.9% achieved remission after initial treatment, but 85.7% were in remission at final follow-up, with no signs of recurrence throughout the follow-up period (mean: 21.4 months). The average treatment cost was £39,249.50 with a net mean loss of £19,080.10 when funding was considered. The mean-derived EQ-5D score was 0.360 and the mean EQ-VAS score was 61.7, lower than their values for United Kingdom’s general population, p = 0.0018 and p = 0.013 respectively. Conclusions Chronic femoral osteomyelitis treatment is difficult, resulting in significant economic burden. With previous studies showing cheaper osteomyelitis treatment at specialist centres, our net financial loss incurred suggests the need for management at specialised centres.

A note on attainment of puberty of september-born early-maturing ewe lambs in relation to level of nutrition

1991 ◽  
Vol 53 (3) ◽  
pp. 407-409 ◽  
Author(s):  
F. Forcada ◽  
J. A. Abecia ◽  
L. Zarazaga
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Plasma Progesterone ◽  
Ewe Lambs ◽  
Early Maturing ◽  
Age At Puberty

The attainment of puberty in September-born early-maturing ewe lambs was studied at Zaragoza (latitude 41° 40' N). Thirty twin Salz females were allocated to two groups receiving two nutrition levels after 3 months of age: high (500 g/day lucerne hay and 500 g/day concentrate) (H) and low (500 g/ day lucerne hay) (L). Oestrus was detected daily by aproned rams. Corpora lutea were counted after oestrus and plasma progesterone levels monitored each week.In the first breeding season (January to February) the percentage of females showing sexual activity (silent emulation or oestrus and ovulation) was higher in the H compared with the L group (67 and 20%; P < 0/05). Nonpubertal oestrus before the main breeding season was detected in 67% of animals. In the main breeding season and for H and L groups respectively, percentage of females showing silent ovulation before puberty was 67 and 33% and mean age at puberty extended to 319 (s.e. 4-8) and 314 (s.e. 3·7) days. Ovulation rate at puberty was 1·73 (s.e. 0·13) and 1·33 (s.e. 0·15) respectively (P < 0·05).

The effect of stage of breeding season or pre-mating oestrogen and progestagen therapy on fertility in ewe lambs

1994 ◽  
Vol 59 (3) ◽  
pp. 429-434 ◽  
Author(s):  
N. F. G. Beck ◽  
M. C. G. Davies
Keyword(s):  
Breeding Season ◽  
Corpora Lutea ◽  
Oestrogen Therapy ◽  
Crown Rump Length ◽  
Ewe Lambs ◽  
Oestradiol Benzoate

AbstractAn investigation was conducted to determine the effect of mating at puberty or third oestrus or after pre-mating oestrogen and progestagen therapy, designed to mimic the changes that occur in plasma oestrogen and progesterone concentrations during the 1st, 2nd or 3rd oestrous cycles, on fertility in ewe lambs. Twenty-five ewe lambs were mated at puberty on mean date of 18 October and 21 were mated at third oestrus on 3 December. Of these, 28% and 81% of animals mated at puberty and third oestrus lambed, respectively (P < 0·05). A similar number of ewe lambs were mated within 24 h of ram introduction in the groups given one, two or three consecutive applications oestrogen and progestagen (25 μg oestradiol benzoate followed 48 h later by a progestagen pessary left in situ for days). Of the 43 corpora lutea, 21 were represented by viable embryos in the 37 animals holding to service after one application compared with 34 out of 46 corpora lutea in 40 animals given three applications (P < 0·05). Furthermore, embryo crown-rump length, embryo weight and amniotic sac width was greater (P < 0·05), on day of pregnancy, in animals given one compared with three applications of oestrogen and progestagen. These results demonstrate that fertility is improved in ewe lambs mated on third oestrus or after progestagen and oestrogen therapy designed to simulate three oestrous cycles.

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