Duration of melatonin treatment and ovarian activity in ewes

1988 ◽  
Vol 1988 ◽  
pp. 92-92
Author(s):  
S. Wigzell ◽  
J.J. Robinson ◽  
J.M. Wallace ◽  
R.P. Aitken
Keyword(s):  
Breeding Season ◽  
Ovarian Activity ◽  
Similar Reaction ◽  
Melatonin Treatment ◽  
Oral Dosing ◽  
Starting Time ◽  
Highly Effective ◽  
Natural Photoperiod ◽  
The Mean

Daily oral dosing in mid afternoon with 3 mg of the indoleamine, melatonin, from early June onwards is highly effective in advancing the breeding season of both Greyface and Scottish Blackface ewes kept under a natural photoperiod; the mean reaction interval from initial dosing to the onset of ovarian activity in Scottish Blackface ewes being around 65 days compared with 110 days for untreated controls (Robinson et al 1985). Advancing the starting time for the melatonin treatment to mid-March gave a similar reaction interval with behavioural oestrus occurring in late May/early June (Wigzell et al 1986a). Following this reversal of the breeding season by melatonin, continued melatonin treatment in unmated ewes resulted in a period of oestrous cyclicity lasting 4 to 5 months. Thereafter the ewes became refractory to melatonin and returned to anoestrus at a time when untreated controls were commencing ovarian activity (Wigzell et al 1986b). These observations prompted us to investigate the effects of different durations of melatonin treatment on ovarian activity.

The onset of the breeding season in Southdown ewes in subtropical Australia

1966 ◽  
Vol 66 (2) ◽  
pp. 295-296 ◽  
Author(s):  
I. D. Smith
Keyword(s):  
Breeding Season ◽  
Ovarian Activity ◽  
Summer Solstice ◽  
Ewe Lambs ◽  
The Mean ◽  
Age At Puberty ◽  
Annual Means ◽  
Subtropical Australia

Observations on the onset of the breeding season in a flock ofSouthdown ewes in subtropical Australia (latitude 27° S.) indicated that the mean date of onset during the years 1962-65 was 3 March, with annual means ranging from 11 February to 17 March. There was evidence that, under some circumstances, ovarian activity may be initiated before the summer solstice.The onset of the breeding season was later in ewe lambs than in yearling and adult ewes and the mean age at puberty was 239 days.

The effect of the oral administration of melatonin at two times of the year on ovarian activity in ewes

1986 ◽  
Vol 1986 ◽  
pp. 53-53 ◽  
Author(s):  
S. Wigzell ◽  
J. J. Robinson ◽  
R. P. Aitken ◽  
W. A. C. McKelvey
Keyword(s):  
Oral Administration ◽  
Breeding Season ◽  
Daily Administration ◽  
Ovarian Activity ◽  
Melatonin Treatment ◽  
Breeding Activity ◽  
Normal Period

It has previously been shown (Robinson et al., 1985) that the normal breeding season of Greyface and Scottish Blackface ewes can be advanced by the daily administration of the indoleamine melatonin; the administration of the melatonin beginning midway during the anoestrous period. If melatonin is administered towards the end of the normal breeding season, oestrous activity can be extended, but only for a period of about six weeks until the ewe becomes refractory to the melatonin treatment (Nett and Niswender, 1981). There is no information on the administration of melatonin at the beginning of the anoestrous period.In the following experiments we report results for the influence on the subsequent breeding activity of Greyface ewes of the oral administration of melatonin at the beginning of their normal period of anoestrus. We also report the results of an investigation on the effects of melatonin in advancing the breeding season of Scottish Blackface ewes maintained on either a high or low plane of nutrition. The experiments were carried out under natural daylength conditions at 57°N.

Effects of melatonin and a dopamine agonist and antagonist on seasonal changes in voluntary intake, reproductive activity and plasma concentrations of prolactin and tri-iodothyronine in red deer hinds

1990 ◽  
Vol 125 (2) ◽  
pp. 241-249 ◽  
Author(s):  
J. A. Milne ◽  
A. S. I. Loudon ◽  
A. M. Sibbald ◽  
J. D. Curlewis ◽  
A. S. McNeilly
Keyword(s):  
Dopamine Agonist ◽  
Breeding Season ◽  
Red Deer ◽  
Plasma Concentrations ◽  
Control Group ◽  
Rapid Decline ◽  
Dopamine Antagonist ◽  
Plasma Prolactin ◽  
Melatonin Treatment ◽  
The Mean

ABSTRACT Three experiments were conducted in the period between July and November with non-lactating red deer hinds to describe the effects of treatment with melatonin during this period on voluntary food intake (VFI), the onset of the breeding season, coat changes and plasma concentrations of prolactin and tri-iodothyronine (T3), and to examine whether prolactin mediated the observed effects. In experiment 1, eight animals were treated orally each day with either 10 mg melatonin at 16.00 h or 10 mg melatonin at 16.00 h plus 10 mg domperidone (a dopamine antagonist) given twice daily for 120 days from July; eight animals were maintained as controls. In experiment 2, the same numbers of animals per treatment were used to compare treatments in which 10 mg melatonin or 20 mg bromocriptine (a dopamine agonist) were given orally each day at 16.00 h for 119 days from late June and compared with an untreated control group. In experiment 3, six animals were treated daily for 105 days from mid August with 5 mg domperidone given i.m. and compared with six control animals. In experiments 1 and 2, the VFI of control animals reached a peak in late August and thereafter declined. Melatonin-treated animals showed a similar pattern but the peak in VFI was significantly (P<0·05) advanced by 2 weeks compared with controls, although the VFIs of both groups were similar in November. The mean date of onset of the breeding season of the melatonin-treated animals was advanced significantly (P < 0·05) by 23 days in both experiments and the coats of these animals had less undercoat and were pale coloured and patchy compared with the controls. The changes in VFI, coat and the onset of the breeding season were associated with the rapid decline in plasma prolactin concentration after the start of the melatonin treatment and significantly (P<0·01) lower plasma T3 concentrations than those of control animals. In experiments 1 and 3, plasma prolactin concentrations in animals treated with domperidone were higher than those of controls for periods of 2–3 weeks. These short-term increases in plasma prolactin concentration were not associated with changes in VFI, coat or onset of the breeding season compared with controls. In experiment 2, the pattern of decline in plasma prolactin concentrations was the same in bromocriptine-treated animals as in the melatonin-treated animals; plasma T3 concentrations were also similar in the two groups. The pattern of change in VFI over time in bromocriptine-treated animals was significantly (P<0·05) different from that of melatonin-treated animals and there was also a reduced amount and length of winter coat in the bromocriptine-treated animals. The mean date of onset of the breeding season in bromocriptine-treated animals was not significantly different from that of controls. It was concluded that a reduction in plasma prolactin concentration induced by bromocriptine produced different effects from that induced by melatonin treatment and that the effects of melatonin are unlikely to be induced through changes in contemporary plasma prolactin concentrations. Journal of Endocrinology (1990) 125, 241–249

The influence of the stag on pubertal development in the red deer hind

1995 ◽  
Vol 60 (3) ◽  
pp. 503-508 ◽  
Author(s):  
M. W. Fisher ◽  
L. M. Meikle ◽  
P. D. Johnstone
Keyword(s):  
Breeding Season ◽  
Social Factors ◽  
Red Deer ◽  
Pubertal Development ◽  
Ovarian Activity ◽  
Melatonin Treatment ◽  
Timing Of Puberty

AbstractThe possible influence of social factors on the timing of puberty in the hind was investigated utilizing seasonally advanced (melatonin-treated) hinds and stags. Melatonin treatment of both sexes resulted in a significant advancement in the onset of pubertal ovarian activity (26 days, P < 0·001) and calving (27 days, P < 0·001) in the treated hinds and antler casting (25 days, P < 0·001) in the treated stags. Ovarian activity and calving were not influenced by melatonin treatment of the stags alone and similarly, antler casting was not affected by melatonin treatment of the hinds alone. However, a group of hinds without stags until after the onset of the breeding season, reached puberty later (5 days, P < 0·05) than hinds with stags, suggesting the presence of the male is important in determining the timing of puberty.

Effects of treatment with melatonin on the response of seasonally anovular ewes to the introduction of rams

1991 ◽  
Vol 53 (2) ◽  
pp. 203-207 ◽  
Author(s):  
M. Rekik ◽  
M. J. Bryant ◽  
F. J. Cunningham
Keyword(s):  
Factorial Design ◽  
Pregnancy Rate ◽  
Jugular Vein ◽  
Live Weight ◽  
Response To Treatment ◽  
Ovarian Activity ◽  
Melatonin Treatment ◽  
Plasma Melatonin ◽  
The Mean

AbstractSixty-four mature ewes (equal numbers of Bluefaced Leicester ♂ × Swaledale ♀ and Suffolk ♂ × (Bluefaced Leicester ♂ × Swaledale ♀) which had lambed in March were separated from their lambs on 1 fune. They were randomly allocated from breed and live-weight blocks to one of four treatments arranged in a 2 × 2 factorial design. All received vaginal implants, with or without melatonin, on 1 June. The implants were removed, all ewes given 20 mg progesterone in oil intramuscularly and equal numbers isolated or introduced to rams on 12 July. Ovarian activity was monitored by progesterone concentrations in blood taken three times weekly from the jugular vein. Four ewes receiving melatonin and four control ewes were bled for 24 h on 6 July to determine plasma melatonin concentrations.Melatonin treatment increased plasma melatonin concentrations during the day. All ewes were anovular prior to 12 July. There were no differences between the two ewe types in their response to treatment. The number of ewes ovulating before 27 August was: control 1; melatonin 6; ram 16; melatonin + ram 16. The mean date of emulation for both the ram and melatonin + ram groups was 21 July. The number of ewes showing oestrous behaviour was 16 and 15 for the ram and melatonin + ram treatments respectively. The proportion of ewes responding to ram introduction was judged as unusually high, possibly as a result of the favourable male:female ratio. Pregnancy rate was in excess of 80% for both treatments, with resulting litter sizes of 14 for the ram and 1·8 for the melatonin + ram treatments respectively (P > 0·05).

The effect of melatonin treatment during the seasonal anoestrus on the superovulatory response and embryo production of high-prolificacy Rasa Aragonesa ewes before culling

2003 ◽  
Vol 2003 ◽  
pp. 82-82
Author(s):  
F. Forcada ◽  
J.A. Abecia ◽  
J.A. Valares
Keyword(s):  
Embryonic Development ◽  
Breeding Season ◽  
Litter Size ◽  
Direct Effect ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Melatonin Treatment ◽  
Embryo Production ◽  
Spring Equinox

The efficacy of melatonin implants inserted around the spring equinox to improve fertility and ovulation rate or litter size in Mediterranean ewes has been previously reported (Chemineau et al., 1996; Forcada et al., 2002a.), indicating the ability of the hormone to regulate the hypothalamic activity (Viguié et al., 1995). Moreover, a direct effect of melatonin on corpora lutea and embryonic development has been also reported (Wallace et al., 1988; Abecia et al., 2002). The use of prolific Rasa Aragonesa (RA) ewes (a Mediterranean breed) before culling as embryo donors has been previously tested in the breeding season (Forcada et al., 2002b.). The aim of this experiment was to improve embryo production during the seasonal anoestrus period in selected superovulated RA ewes at the end of their reproductive lives through the use of melatonin.

scholarly journals Suppression of ovarian activity during the breeding season in suckling Japanese monkey (Macaca fuscata)

Reproduction ◽  
1991 ◽  
Vol 92 (2) ◽  
pp. 371-375 ◽  
Author(s):  
K.-I. Maeda ◽  
H. Tsukamura ◽  
S. Ohkura ◽  
T. Kanaizuka ◽  
J. Suzuki
Keyword(s):  
Breeding Season ◽  
Macaca Fuscata ◽  
Japanese Monkey ◽  
Ovarian Activity

Effect of melatonin treatment on semen parameters and endocrine function in Black Racka rams out of the breeding season

2014 ◽  
Vol 116 (2-3) ◽  
pp. 192-198 ◽  
Author(s):  
I. Egerszegi ◽  
P. Sarlós ◽  
J. Rátky ◽  
L. Solti ◽  
V. Faigl ◽  
...  
Keyword(s):  
Breeding Season ◽  
Endocrine Function ◽  
Semen Parameters ◽  
Melatonin Treatment

scholarly journals Early Cessation of Breastfeeding and Determinants: Time to Event Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Ebrahim Babaee ◽  
Babak Eshrati ◽  
Mehran Asadi-Aliabadi ◽  
Majid Purabdollah ◽  
Marzieh Nojomi
Keyword(s):  
Hazard Ratio ◽  
Breastfeeding Duration ◽  
Event Analysis ◽  
Time To Event ◽  
Starting Time ◽  
Factors Influencing ◽  
The Status ◽  
The Mean ◽  
Breastfeeding Rates ◽  
Analyze Data

Background. The onset of breastfeeding has a high success rate in most countries, but the time for termination of breastfeeding varies between countries. Objective. This survey was aimed to determine the effective factors on the early termination of breastfeeding. Methods. This study was conducted in 2018, in Iran. About 410 mothers were enrolled in the study. All considered factors were evaluated as factors influencing the continuity of breastfeeding. Survival analysis was used to analyze data. Results. The mean age of the mothers was equal to 29.48 ± 5.8 years. The frequency of termination of breastfeeding before the first 2 years was equal to 34%. The mean of breastfeeding duration was equal to 21.49 ± 5.3 months. The percentage of infants who had been breastfed for 24 months was equal to 65.8%. An infant’s birth weight (2500–4000 gr) (hazard ratio: 0.54), neonatal birth order (hazard ratio: 0.69), neonatal pathologic jaundice (hazard ratio: 1.52), starting time of using complementary food (hazard ratio: 2.45), using pacifier (hazard ratio: 2.82), and the status of using artificial milk (hazard ratio: 3.29) were significantly associated with cessation of breastfeeding before 24 months of age. The probability of termination of breastfeeding at 6, 12, 18, and 24 months of age was reported by 6%, 8%, 15%, and 34%, respectively. Conclusions. There were notifiable variations in breastfeeding rates both in national and international levels. Nevertheless, in this study, the mean of breastfeeding duration was longer compared to a number of countries and previous national studies.

The effect of body size and body condition on the ovulation rate of ewes

1977 ◽  
Vol 24 (3) ◽  
pp. 377-385 ◽  
Author(s):  
M. J. Ducker ◽  
J. S. Boyd
Keyword(s):  
Body Size ◽  
Breeding Season ◽  
Body Condition ◽  
Live Weight ◽  
Ovulation Rate ◽  
Subjective Measure ◽  
Body Dimensions ◽  
The Mean ◽  
Per Se ◽  
Linear Body

SUMMARYBody size was estimated for 255 Greyface ewes using five linear body dimensions. On the basis of this calculated measure combined with a subjective measure of body size 50 small and 50 large ewes were selected for use in the experiment. Precise ovulation data were obtained by endoscopy and this technique allowed the ewes to be mated subsequently.Body size did not affect the mean ovulation rate of the ewes although, at the same level of body condition, the large ewes were 25% heavier than the small ewes. The ovulation rates and the numbers of lambs born were influenced by changes in live weight and body condition. For these reasons live weight per se was not a good indicator of ovulation rate as ewe live weight was a combination of both body size and body condition. At the same live weight small ewes in improving body condition had a significantly higher ovulation rate than large ewes in reducing body condition.The onset of the breeding season of the ewes was not affected by their body size. The mean date of onset of oestrous activity for both large and small ewes was 17 October 1972 at a latitude 55° 52′ N.

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