Variations saisonnières du comportement d'œstrus et de l'activité ovulatoire chez les brebis Chios et Serres en Grèce

-The objective of this study was to evaluate the effects of season, natural photoperiod, and room temperature at the housing facility on boar semen characteristics in Uruguay (34º66'S; 56º29'W). For this purpose, 117 ejaculates, obtained from eight adult males collected through 12 consecutive months, were assessed for sperm viability, DNA integrity, abnormalities (total, primary, and secondary), ejaculate volume, and sperm concentration. Viability, total and primary abnormalities, volume, and sperm concentration were affected by season. Sperm viability, volume, and sperm concentration were affected by natural photoperiod. In general, autumn and the decreasing photoperiod had a negative impact on most of the semen characteristics, except for volume. Housing temperature did not affect semen characteristics. In boars living in temperate climates, semen quality is negatively affected during autumn and is related to photoperiod changes; however, the effects of temperature changes in housingdo not affect these seminal characteristics. In this scenario, seasonal differences in semen quality may have a negative effect on sow fertilization. Consequently, semen quality control especially during autumn is imperative for the best boar selection to be used for insemination purposes. Seasonal differences in semen quality may have a negative effect on sow reproductive performance. This issue will be addressed in a future investigation.

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“…This aspect has been reported in other animals such as the goat (Delgadillo et al, 1991;Avdi et al, 1993;López-Fernández et al, 2001).…”

Section: Discussionsupporting

confidence: 75%

Seasonal variation in sperm characteristics of boars in southern Uruguay

2015

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“…These variations of the reproductive activity were described for all breeds outside of the tropics showing increasing seasonality with latitude. In northern Europe, the duration of anestrus can last up to 260 days [30], while in southern Europe (Greece [31]; Spain [32]) or North Africa (Morocco [33]; Tunisia [34]), the mean duration of anestrus is limited to 50-130 days, and they could be considered like reduced seasonality breeds. As stated earlier, the onset of the breeding season appeared to be a less variable trait than its offset, probably because of the synchronization of the first ovulations among ewes due to entrainment among them [23,29].…”

Section: Discussionmentioning

confidence: 99%

Amplitude of the plasma melatonin nycthemeral rhythms is not associated with the dates of onset and offset of the seasonal ovulatory activity in the Ile-de-France ewe

2003

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-We investigated if absolute (nocturnal) or relative (nocturnal/diurnal ratio) plasma melatonin concentrations were associated with the seasonal ovulatory activity in Ile-de-France ewes. Ninety-six and 121 ewes in two different groups of the same flock were used to determine the potential existence of a relationship between melatonin concentrations at the summer and winter solstices, and the dates of onset and offset of the ovulatory activity, respectively. The dates of the first and last ovulations were estimated by assaying progesterone in plasma samples taken once weekly. Mean ± SEM (1) plasma melatonin concentrations at the summer solstice and at the winter solstice were 302.4 ± 19.4 and 412.0 ± 18.7 pg·mL -1 , respectively, (2) date of onset of the breeding season 29 Jul. ± 1.6 days, (3) date of offset of the breeding season 24 Jan. ± 2.2 days. In spite of a large variability in the different traits studied here, the analyses of correlation and regression indicated that neither the absolute nor relative melatonin concentrations were significantly related with the dates of onset or offset of ovulatory activity. Therefore, we concluded that absolute or relative plasma melatonin concentrations are not linked to the seasonal breeding activity, in Ile-de-France ewes.sheep / melatonin / reproduction / seasonality / genetics

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“…With this model it was possible to separately include the individual animal and permanent environmental effects, and all available genetic relationships. The following linear model was fitted: (1) where: Y = spontaneous out-of-season ovulatory activity record (0,1); µ = overall mean; age = fixed effect of the ith age of the ewe class; weight = fixed effect of the jth weight of the ewe class; month = fixed effect of the kth calendar month of the previous lambing class; animal = random effect of the lth ewe (Variance = V a ); pe = random effect of the permanent environment of the lth ewe (Variance = V pe ); e = random residual effect (Variance = V e ).…”

Section: Statistical Models and Genetic Analysismentioning

confidence: 99%

“…Several researchers have shown differences in the duration of the breeding season of sheep raised in the same region [1,24]. The principal mechanism that triggers the onset of the breeding season relates to light.…”

Section: Introductionmentioning

confidence: 99%

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Sources of variation and genetic profile of spontaneous, out-of-season ovulatory activity in the Chios sheep

et al. 2003

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-Organising the breeding plan of a seasonally breeding species, such as sheep, presents a challenge to farmers and the industry as a whole, since both economical and biological considerations need to be carefully balanced. Understanding the breeding activity of individual animals becomes a prerequisite for a successful breeding program. This study set out to investigate the sources of variation and the genetic profile of the spontaneous, out-of-season ovulatory activity of ewes of the Chios dairy sheep breed in Greece. The definition of the trait was based on blood progesterone levels, measured before exposing the ewes to rams, which marks the onset of the usual breeding season. Data were 707 records, taken over two consecutive years, of 435 ewes kept at the Agricultural Research Station of Chalkidiki in northern Greece. When all available pedigree was included, the total number of animals involved was 1068. On average, 29% of all ewes exhibited spontaneous, out-of-season ovulatory activity, with no substantial variation between the years. Significant sources of systematic variation were the ewe age and live weight, and the month of previous lambing. Older, heavier ewes, that had lambed early the previous autumn, exhibited more frequent activity. Heritability estimates were 0.216 (±0.084) with a linear and 0.291 with a threshold model. The latter better accounts for the categorical nature of the trait. The linear model repeatability was 0.230 (±0.095). The results obtained in this study support the notion that spontaneous out-of-season ovulatory activity can be considered in the development of a breeding plan for the Chios sheep breed.reproduction / genetic parameter / sheep / ovulatory activity

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Variations saisonnières du comportement d'œstrus et de l'activité ovulatoire chez les brebis Chios et Serres en Grèce

Cited by 23 publications

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Seasonal variation in sperm characteristics of boars in southern Uruguay

Seasonal variation in sperm characteristics of boars in southern Uruguay

Amplitude of the plasma melatonin nycthemeral rhythms is not associated with the dates of onset and offset of the seasonal ovulatory activity in the Ile-de-France ewe

Sources of variation and genetic profile of spontaneous, out-of-season ovulatory activity in the Chios sheep

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