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Biomedical subjects

J Thimonier

Publications and source records attributed to J Thimonier.

At least 37 records · Page 2Linked to original sources
PubMed1986

Induction and persistence of pituitary and ovarian activity in the out-of-season lactating dairy goat after a treatment combining a skeleton photoperiod, melatonin and the male effect.

Thirty-two out-of-season Saanen dairy goats were involved in a 2 X 2 factorial experiment using (1) extra-light treatment (equivalent to long days) from 18 January to 19 March, at the end of gestation and the onset of lactation and (2) daily melatonin injections (equivalent to short days) from 20 March to 30 June. Hence, there were 4 groups of 8 goats each: CC (control-control), EC (extra-light-control), CM (control-melatonin) and EM (extra-light-melatonin). In each group teasers (males and androgenized females) were introduced on 30 May. Serial blood samples were taken for measurement of LH pulsatility on 30 April and 30 May. Ovarian activity was followed by plasma progesterone assay and laparoscopy. Oestrous behaviour was checked daily from 30 May to 15 July. The number of LH pulses was not modified by the treatments (extra light or melatonin). Melatonin treatment increased the basal concentration of LH (Groups CC + EC = 0.30 ng/ml; Groups CM + EM = 0.38 ng/ml; P less than 0.02) and the amplitude of pulses (Groups CC + EC = 1.24; Groups CM + EM = 2.44 ng/ml; P less than 0.02); the highest amplitude was observed for females in Group EM. Melatonin-treated females ovulated earlier after introduction of teasers than did untreated goats (Groups CM + EM = 2.3 days; Groups CC + EC = 6.1 days; P less than 0.001), but treatments did not modify ovulation rate (mean 2.1) or percentage of goats experiencing a short luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Preovulatory LH characteristics and time of ovulation in the prolific Booroola Merino ewe.

In 4 separate experiments involving 133 ewes the timing of the onset of the LH discharge relative to the onset of oestrus was compared in prolific Booroola Merinos and in other Merinos of low ('C' and 'O' genotypes) and medium ('T' genotype) prolificacy. Despite different average ovulation rates of 3.05, 1.85, 1.18 and 1.37 for Booroola, 'T', 'O' and 'C' ewes, respectively, there were no consistent differences in the time of the LH discharge which occurred on average 4.5 h after the onset of oestrus. Time of ovulation was studied, in two experiments involving 430 Booroola, 'T', 'O' and 'C' ewes, by laparoscopic ovarian examination of subsamples of ewes at 20, 24, 28 or 32 h after onset of oestrus. Ovulation occurred significantly (P less than 0.001) earlier (7.5 h) in Booroola ewes than in those of the other genotypes.

Animals↗
PubMed1982

[Seasonal variations in creole heifer cyclicity: effect of growth, age and emotivity].

The ovarian and estrous activities in creole heifers have been studied in Guadeloupe in a tropical environment. We carried out two experiments. In the first one, all the heifers from the research station's herd were blood-sampled twice every 2 months at a 10-day interval to determine their ovarian activity. The observations were ranked in order of ascending live weight, and the percentage of heifers showing ovarian activity was calculated for consecutive 10-kg increments in live weight from 115 to 275 kg. The percentage showing ovarian activity (Y) was subjected to probit transformation and related to live weight (X); probit Y = 12.4 log10 X - 23.7. The equation for observations ranked in order of ascending age and the percentage of heifers showing ovarian activity calculated for age increments over 2 consecutive months was: probit Y = 7.06 log10 X - 3.9. Furthermore, the percentage of cyclic heifers in the herd varied from 40 p. 100 in September 1979 to 0 p. 100 in July 1980 and then to 30 p. 100 in September 1980. The percentage of cyclic heifers at a given period of observation was highly correlated with the mean daily increase in body weight (r = 0.86). In the second experiment, 12 heifers with a high feed level were blood-sampled weekly and checked for estrous daily with an androgenized female with a chin ball mating harness. The mean duration of a "normal cycle" (interval between two estruses: more than 15 but less than 31 days) was 21 days. There was no variation of ovarian activity with the month of the year, but the incidence of silent ovulation was high (23.7 p. 100). The seasonal variation of this percentage is shown. Female emotivity was also an important factor: emotional heifers had a higher percentage of silent ovulations than unemotional heifers (27 vs 17 p. 100) and a smaller mean daily gain (180 vs 280 g).

Age Factors↗
PubMed1981

Hormonal and follicular relationships in ewes of high and low ovulation rates.

Total follicular populations and peripheral plasma concentrations of LH, FSH, prolactin, oestradiol-17 beta and progesterone during the preceding cycle were studied in two breeds of sheep (Romanov and Ile-de-France) which differed widely in their ovulation rates (3.2 and 1.5 respectively). No LH parameters could be correlated with the follicular details measured. The second peak of FSH occurring 20-30 h after the preovulatory surge of LH was significantly larger in the Romanov ewes and the area under this peak was correlated (P less than 0.01) with the number of antral follicles present in the ovary 17 days later. This suggests that formation of the antrum during the follicular growth phase is under the control of FSH. The discharge of prolactin preceding the LH peak, although not significantly different between breeds, was correlated with several of the follicular classes measured, including the number of preantral follicles. The peak value of oestradiol-17 beta measured before the LH peak was significantly higher (P less than 0.05) in the Romanov ewes and was correlated with the number of the largest follicles present. There was no significant difference between breeds in the concentration of oestradiol at the onset of oestrus. The progesterone concentration during the luteal phase was highly correlated with the number of preovulatory follicles.

Animals↗
PubMed1981

Control of seasonal reproduction in sheep and goats by light and hormones.

Seasonal variations of reproductive ability have been demonstrated in male and female sheep and goats. For the female, there is a distinct breeding season. Whilst there are large breed differences in the duration of the sexual season, oestrous cycles generally start when daylength is decreasing and end when daylength is increasing. In some breeds, ovulation without oestrus occurs during the non-breeding season. Although males are able to mate all the year round, seasonal variations occur in the weight of the testis and seminal vesicles and in the fructose concentration of the seminal vesicles. Sexual behaviour and semen characteristics also show seasonal variations. These seasonal variations in males and females are related to hormonal levels. FSH and LH concentrations in the pituitary are reduced to 50% during the non-breeding season. In the peripheral blood, LH concentrations vary throughout the year whilst prolactin concentrations follow the pattern of daylength. Steroid hormones and their feedback actions at the hypothalamo-pituitary axis play a role in the regulation of seasonal reproduction. Three different ways are proposed to overcome these seasonal variations. (1) Males can be introduced into a flock of females before the onset of the breeding season. This leads to induction of ovulation and oestrus, although the first ovulation is frequently followed by a short luteal phase. Teasing does not necessitate contact or sight and is only effective after a period of isolation of the females from the males. (2) Oestrus and ovulation may be induced during the anoestrous period by hormonal treatments. Inducers of LH release have to be associated with a progestagen treatment; PMSG is still the most efficient inducer of LH release. Artificial insemination is useful in this context to avoid subfertility due to seasonal variations of the male. (3) The period of reproduction may be controlled by artificial light regimens. There is a photoinducible period in the circadian cycle of the ewe and it may soon be practical to breed out of season by timed exposure of ewes to short periods of light during the normal hours of darkness.

Animals↗
PubMed1979

Periovulatory gonadotrophin and ovarian steroid patterns in sheep of breeds with differing fecundity.

Plasma hormone concentrations before and during luteolysis (induced by injection of a prostaglandin analogue on Day 10 or 11 of the cycle), during the period of preovulatory follicle growth and ovulation were examined in sheep with known differences in ovulation rate (Romanov, Préalpes, Romanov x Préalpes cross, Ile de France). The number of CL at the time of treatment and the ovulation rate in the ensuing cycle were established by endoscopy. Plasma concentrations of FSH, LH, progesterone and total oestrogen were measured by radioimmunoassays in the 3 days before PG injection, then hourly for the 24 h after PG injection and 2-hourly for a further period up to about 100 h after PG injection. The onset and duration of oestrus were also recorded. Although breed differences were observed for many of the features studied, only the intervals between oestrus and the LH peak and between PG injection and the LH peak were significantly correlated with ovulation rate.

Animals↗