Comparison of luteal function between ewe lambs and ewes during breeding and non breeding season

1998 ◽  
Vol 1998 ◽  
pp. 184-184
Author(s):  
T.H. Khan ◽  
N.F.G. Beck ◽  
M. Khalid
Keyword(s):  
Embryo Development ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Corpora Lutea ◽  
Luteal Function ◽  
Previous Evidence ◽  
Ewe Lambs

Reproductive performance of ewe lambs is lower than that of adult ewes (Quirke. 1979). This is mainly the result of preimplantation losses which can exceed 50% in ewe lambs as compared with 20-30% in ewes (Quirke et al.,1981). Previous evidence from this laboratory suggests that these losses may be associated with inadequate luteal function in ewe lambs (Davies and Beck, 1993). Inadequate luteal function may not only delay the embryo development but also impair the ability of the embryo to communicate its presence to the maternal system. There is also a possibility that inadequate corpora lutea may be refractory to luteotrophic factors produced by the developing embryo. The present study was designed to investigate whether the luteal function varies between ewe lambs and ewes. Another objective of this study was to compare the luteal response to hCG challenge between ewe lambs and ewes and its variation with season.

Comparison of luteal function between ewe lambs and ewes during breeding and non breeding season

1998 ◽  
Vol 1998 ◽  
pp. 184-184
Author(s):  
T.H. Khan ◽  
N.F.G. Beck ◽  
M. Khalid
Keyword(s):  
Embryo Development ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Corpora Lutea ◽  
Luteal Function ◽  
Previous Evidence ◽  
Ewe Lambs

Reproductive performance of ewe lambs is lower than that of adult ewes (Quirke. 1979). This is mainly the result of preimplantation losses which can exceed 50% in ewe lambs as compared with 20-30% in ewes (Quirke et al.,1981). Previous evidence from this laboratory suggests that these losses may be associated with inadequate luteal function in ewe lambs (Davies and Beck, 1993). Inadequate luteal function may not only delay the embryo development but also impair the ability of the embryo to communicate its presence to the maternal system. There is also a possibility that inadequate corpora lutea may be refractory to luteotrophic factors produced by the developing embryo. The present study was designed to investigate whether the luteal function varies between ewe lambs and ewes. Another objective of this study was to compare the luteal response to hCG challenge between ewe lambs and ewes and its variation with season.

Comparison of ovarian oestradiol and progesterone secretion, in vitro, between ewe lambs and ewes

2005 ◽  
Vol 2005 ◽  
pp. 149-149
Author(s):  
M. A. Younes ◽  
N. F. G. Beck ◽  
M. T. Rose ◽  
B. Davies
Keyword(s):  
Reproductive Performance ◽  
Steroid Hormone ◽  
Corpora Lutea ◽  
Ovarian Hormone ◽  
Hormone Production ◽  
Previous Evidence ◽  
Ewe Lambs ◽  
Progesterone Secretion ◽  
Ewe Lamb

Reproductive performance of ewe lambs is lower than that of adult ewes (Quirke 1979). This is mainly the result of preimplantation losses, which can exceed 50% of fertilised eggs. Previous evidence from this laboratory suggests that these losses may be associated with abnormal ovarian hormone production (Davies and Beck 1993). Khan (1999) demonstrated that blood progesterone levels during the oestrous cycle and pregnancy were lower in ewe lambs than in ewes. Furthermore, both progesterone and oestradiol concentrations were lower in ewe lambs, than in ewes, following gonadotrophin stimulation (Khan, Beck and Khalid 1999). These results suggest that ewe lamb corpora lutea and follicles secrete less progesterone and oestradiol, respectively, than those of ewes. The aim of this study was to determine whether there is a difference in vitro steroid hormone production by corpora lutea and follicles, from ewe lambs and ewes.

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.

Early reproductive losses are a major factor contributing to the poor reproductive performance of Merino ewe lambs mated at 8–10 months of age

2014 ◽  
Vol 54 (6) ◽  
pp. 762 ◽  
Author(s):  
B. L. Paganoni ◽  
M. B. Ferguson ◽  
S. Fierro ◽  
C. Jones ◽  
G. A. Kearney ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
First Record ◽  
Reproductive Rate ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Mating Period ◽  
Breeding Values ◽  
Pregnancy Failure ◽  
Ewe Lambs ◽  
Reproductive Losses

The reproductive performance of Merino ewe lambs is lower than that achieved by mature ewes and is highly variable. It is likely that embryo loss represents a major source of reproductive wastage in Merino ewe lambs, but to our knowledge no studies have attempted to determine when the major reproductive losses occur or identify predisposing factors that are likely to lead to high rates of pregnancy failures in ewe lambs. After characterising where reproductive losses occurred in Merino ewe lambs mated at 8–10 months of age, we tested the hypothesis that pregnancy failure in ewe lambs is influenced by nutrition and liveweight change around conception and the genetic potential for growth of the ewe lamb. Two-hundred and twenty-four Merino ewe lambs born from 10 sires with Australian Sheep Breeding Values were teased for 14 days using vasectomised rams, and then fed two different diets for 68 days during mating. All ewe lambs were weighed and the appearance of crayon marks on their rump was recorded most days. Blood samples for progesterone assay were collected on Days 5, 12 and 17 after the first record of a crayon mark. Ultrasonography using a trans-rectal probe was used to measure the number of corpora lutea present, as a proxy for ovulation rate, 9 days after the first record of a crayon mark during the mating period. A further trans-rectal ultrasonography was undertaken 30 days after marking from the entire ram to determine pregnancy status and count the number of embryos. Over the entire mating period 54% of ewe lambs were pregnant with 66 fetuses per 100 ewes mated. The average ovulation rate was 150% however up to 84% of this potential was lost by weaning and the major contributor to this apparent deficit was the loss that occurred during the first 17 days after mating. Pregnancy failure was not significantly related to nutrition or liveweight change during mating however, there were significant differences in pregnancy failure between different sire groups. Pregnancy failure was significantly less for ewe lambs from sires with higher breeding values for weight and fat at post-weaning age (8–10 months). Only 60% of ewe lambs had achieved puberty when rams were introduced and only 83% by 35 days after mating. In addition, almost half of the ewe lambs that were mated for the first time during the first 35 days after rams were introduced, but failed to get pregnant, then seemed to skip a cycle or did not cycle again before the end of the 68-day mating period. Liveweight at introduction of entire rams was positively related to fertility, ovulation rate and reproductive rate. This study confirms that selection of sires with higher breeding values for post-weaning weight and fat will increase the fertility and reproductive rate of Merino ewe lambs mated at 8–10 months. This response is due in part to enhancing the onset of puberty and increasing the proportion of ewe lambs cycling at the start of mating and reducing pregnancy failure.

Reproductive performance of ewe lambs in non-breeding season exposed to hCG at day 12 post mating

2015 ◽  
Vol 124 ◽  
pp. 63-67
Author(s):  
R. Catalano ◽  
M. Teruel ◽  
C. González ◽  
S. Williams ◽  
I. Videla Dorna ◽  
...  
Keyword(s):  
Breeding Season ◽  
Reproductive Performance ◽  
Ewe Lambs

Progestin priming before gonadotrophin stimulation and AI improves embryo development and normalises luteal function in the cat

2015 ◽  
Vol 27 (2) ◽  
pp. 360 ◽  
Author(s):  
Rosemary A. Stewart ◽  
Adrienne E. Crosier ◽  
Katharine M. Pelican ◽  
Budhan S. Pukazhenthi ◽  
Brandon D. Sitzmann ◽  
...  
Keyword(s):  
Embryo Development ◽  
Negative Influence ◽  
Domestic Cat ◽  
Corpora Lutea ◽  
Luteal Function ◽  
Progestin Treatment ◽  
Histological Characteristics ◽  
Targeted Gene Expression

Exogenous gonadotrophins administered before AI can adversely alter endocrine dynamics and inhibit embryo development in felids. In the present study, we tested the hypothesis that priming the domestic cat ovary with progestin mitigates the negative influence of gonadotrophin therapy by normalising early embryogenesis and luteal function. Queens were given either: (1) progestin pretreatment plus chorionic gonadotrophins (n = 8; primed); or (2) gonadotrophins only (n = 8; unprimed). Ovulatory response was assessed laparoscopically, and cats with fresh corpora lutea (CL) were inseminated in utero. Ovariohysterectomy was performed 3 days later to recover intra-oviductal embryos for in vitro culture; one ovary was prepared for histology, and CL from the remaining ovary were excised and assessed for progesterone content and targeted gene expression. Of the six primed and seven unprimed queens inseminated, embryo(s) were recovered from five individuals per group. Embryos from progestin-primed donors more closely simulated normal stage in vivo development (P < 0.05). No 2- or 4-cell embryos from either group developed beyond 16-cells in vitro; however, 50% of unprimed and 66.7% of primed (P > 0.05) 5–16-cell embryos progressed to morulae or blastocysts by Day 4 of culture. Although histological characteristics were unaffected by progestin priming (P > 0.05), luteal progesterone was unusually high (P < 0.05) in unprimed compared with primed cats (72.4 ± 5.8 vs 52.2 ± 5.5 ng mg–1, respectively). Two genes associated with progesterone biosynthesis (luteinising hormone receptor and 3β-hydroxysteroid dehydrogenase) were upregulated in unprimed versus primed individuals (P = 0.05 and P < 0.05, respectively), indicating potential mechanistic pathways for the protective influence of pre-emptive progestin treatment. Building on earlier findings that progestin priming prevents spontaneous ovulation, increases ovarian sensitivity to gonadotrophins and ensures a normative endocrine environment, the present study demonstrates that pretreatment with this steroid also benefits embryo development and normalisation of early luteal function.

Reproductive performance of New Zealand Romney sheep grazed on red clover (Trifolium pratense) pastures

1961 ◽  
Vol 57 (1) ◽  
pp. 123-127 ◽  
Author(s):  
T. S. Ch'ang
Keyword(s):  
New Zealand ◽  
Corpus Luteum ◽  
Breeding Season ◽  
Reproductive Performance ◽  
White Clover ◽  
Trifolium Pratense ◽  
Red Clover ◽  
Ewe Lambs ◽  
Per Se ◽  
Endometrial Cyst

The reproductive performance of 253 female Romney sheep of different ages has been studied from 1958 to 1960. Comparisons of the reproductive performance were made between ewes grazed on red clover pastures and ewes grazed on perennial rye-grass and white clover swards. The red clovers were oestrogenic during all periods of utilization.The ingestion of oestrogenic red clovers caused the ewe lambs to accept the male before the start of the normal breeding season. No corpus luteum was found in the ovary of these lambs thus induced into oestrus. The subsequent reproductive performance of these ewe lambs at 2 years of age was not affected. The oestrus per se or the regularity of oestrus of the young (1½-year-old) or the aged (5½-year-old) ewes was not affected by the diet of oestrogenic red clover.The ingestion of oestrogenic red clover did not affect the reproductive performance of the young ewes at 2 years of age, but did cause a protracted lambing season and a reduced level of lambing performance in the aged ewes at 6 years of age. No endometrial cyst was found in the aged ewes. It was suggested that the reduced level of reproductive performance of the aged ewes could have resulted from an unfavourable environment within the ewe, for the process of fertilization or implantation of the fertilized ova during the breeding season.

Effect of previous lambing date and subsequent month of mating on reproductive performance in Mule ewes

1999 ◽  
Vol 69 (1) ◽  
pp. 217-222 ◽  
Author(s):  
L. M. Mitchell ◽  
M. E. King ◽  
R. P. Aitken ◽  
J. M. Wallace
Keyword(s):  
Factorial Design ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Fertilization Failure ◽  
Mating Period ◽  
Natural Photoperiod ◽  
Natural Breeding ◽  
Main Factor

AbstractThe objective was to determine the effect of previous lambing date and subsequent month of mating on reproductive performance in Mule (Bluefaced Leicester × Scottish Blackface) ewes. Sixty-four ewes which had previously lambed in January (13 January (s.e. = 1 day)) and 80 ewes which had previously lambed in May (15 May (s.e. = 1 day)) were allocated equally to four mating periods (30 August to 17 September, 1 November to 19 November, 3 January to 21 January and 14 February to 4 March) in a 2 × 4 factorial design. From 20 days before and during their designated mating period, January- and May-lambing ewes were separately housed in straw-bedded pens under natural photoperiod and were given 1 kg per head per day dried grass pellets. A vasectomized ram was continuously present with each group for 17 days and was replaced by a raddled, fertility tested entire Suffolk ram at the start of the mating period. Ewes were mated at a single natural oestrus and those marked by the ram were recorded daily. Ovulation rate was measured by laparoscopy on day 6 after mating. For ewes which had previously lambed in January (16 per group), numbers by month of mating that showed oestrous behaviour, ovulated and were pregnant, respectively, were: September, 16, 15 and 12; November, 16, 15 and 14; January, 15, 15 and 10 and February, 15, 16 and 7. Mean (s.e.) ovulation rates by month of mating were 2·1 (0.16), 2·5 (0.19), 2·1 (0.09) and 2·2 (0.19) corpora lutea per ewe ovulating, and lambing rates by month of mating were 1·3 (0.25), 1·9 (0.25), 1·2 (0.24) and 0·8 (0.23) lambs per ewe to the ram. For ewes which had previously lambed in May (20 per group), numbers by month of mating that showed oestrous behaviour, ovulated and were pregnant, respectively, were: September, 13, 20 and 12; November, 20, 20 and 19; January, 20, 20 and 17 and February, 20, 20 and 13. Mean (s.e.) ovulation rates by month of mating were 2·0 (0.13), 2·3 (0.11), 2·1 (0.05) and 2·2 (0.11) corpora lutea per ewe ovulating, and lambing rates by month of mating were 1·0 (0.21), 2·1 (0.15), 1·5 (0.17) and 1·2 (0.21) lambs per ewe to the ram. Ovulation, pregnancy and lambing rates were not influenced by previous lambing date, but lambing rates were significantly (P < 0·01) reduced for ewes mated in September and February compared with November. Results demonstrate that in Mule ewes acceptable ovulation rates can be achieved throughout the period September to February but lambing rates are reduced when ewes are mated at the extremes of their natural breeding season. The main factor contributing to the reduction in lambing rates was an increase in the number of ewes failing to establish pregnancy as a consequence of ovulation without oestrous behaviour, fertilization failure and (or) total embryo loss.

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