Studies on the breeding season of Icelandic ewes and ewe lambs

Dýrmundsson, Ó. R.

doi:10.1017/s0021859600055350

Cited by 31 publications

(14 citation statements)

References 16 publications

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“…Ortavant et al (1985) reported that the Texel breed presents estrus in the summer or beginning of the fall, and it ends at the end of the winter or beginning of summer. Dyrmundsson (1978) and Robinson (1981) claim that breeds originated from latitudes between 35º N and 35º S tend to display estrus all year long, while ewes from higher latitudes tend to present marked reproductive seasonality, probably due to the effects of photoperiod, temperature and radiation.…”

Section: Resultsmentioning

confidence: 99%

Frequency of estrus in Santa Inês, Texel and Ile de France ewes in the northwest of Paraná State, Brazil

et al. 2013

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-The incidence of estrus in nulliparous Santa Inês (n = 16), Texel (n = 16) and Ile de France (n = 15) ewes fed two levels of crude protein (CP, 12 or 16%) was monitored from July 2005 to December 2006, and seasonality in the Santa Inês breed in the south of Brazil was characterized. The solar radiation data were recorded daily, and samples of blood were collected biweekly for determination of the plasma concentration of progesterone in Santa Inês lambs at, on average, 11±1 months of age. The female Santa Inês lambs, in the experimental period, stayed among teaser rams with a powdered-dye-ink mixture placed on their chest to mark the females that accepted to be mounted. Santa Inês ewes did not manifest estrus in the first fortnight of November and in December 2005, nor in the last fortnight of December 2006. Estrus activity was not observed on any of the three breeds in October 2006. Breeds differed at the level of 12% CP. Santa Inês and Ile de France females did not differ as for the probability estrus manifestation and both presented higher probabilities then Texel. When the effect of 12 or 16% CP on each breed was evaluated separately, it was verified that levels of 12 or 16% of crude protein did not change the probability of estrus manifestation in any of the studied breeds. The concentration of plasma progesterone in Santa Inês ewes during the spring of 2005 and 2006 indicated that there is difference between 12% CP (0.68±1.32 ng/mL) and 16% CP (1.28±1.99 ng/mL) and between the years 2005 (0.39±0.78 ng/mL) and 2006 (1.47±2.08 ng/mL), demonstrating the anestrous seasonality of Santa Inês in South Brazil.

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Section: Resultsmentioning

confidence: 99%

Frequency of estrus in Santa Inês, Texel and Ile de France ewes in the northwest of Paraná State, Brazil

et al. 2013

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“…Portanto, esse achado é contrário ao que se observa com ovelhas jovens tendo em vista existirem relatos mencionando que essas fêmeas apresentam menor desempenho reprodutivo na primeira estação de monta do que fêmeas com prévia experiência sexual [7,14]. Essa observação poderia ser válida para as fêmeas que exibiram estro após o 15 o dia da estação de monta tendo em vista apresentarem baixa receptividade a corte do macho [14] e essa timidez de comportamento sexual determinar estros de baixa intensidade [8]. Em trabalho posterior e corroborando com os dados obtidos nesse trabalho [13], concluíram que a inexperiência sexual das fêmeas jovens não é sinônimo da falta de proceptividade ao macho e, assim sendo, não é responsável pelo desencadeamento tardio dos estros numa estação de monta de fêmeas jovens.…”

Section: Discussionunclassified

Role of Male effect on Reproductive Efficiency of Nulliparous Santa Inês and Morada Nova ewes raised in Different Regions

Filho

Ferreira-Silva

Nascimento

et al. 2016

Acta Scientiae. Vet.

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Background:The male effect is an attractive strategy to increase herd production by concentrating mating events and deliveries and further allowing the adoption of genetic improvement programs. It holds similar efficiency to those chemically based estrous synchronization methods, but has the advantage of being a natural method. The work was aimed to evaluate the influence of male effect on estrous induction and synchronization, pregnancy and prolificacy of nulliparous Santa Inês and Morada Nova ewes raised in Semiarid and Zona da Mata regions of Pernambuco state. Materials, Methods & Results: Santa Inês (n = 80) and Morada Nova (n = 80) females, with age from 11 to 12 months, after being evaluated and selected, were identified with plastic ear tags, weighted and maintained isolated from males, during 30 days before experiment onset, without any physical, visual, olfactive and auditive contact. Estrous events were observed twice a day (6:00 and 16:00 h) by trained personnel, during a breeding season of 60 days, and estrous were considered synchronized when detected, within first five days of breeding season. Rams of Santa Inês (n = 2) and Morada Nova (n = 2) breeds were selected based upon reproductive capacity by an andrology exam, and were marked on the externum bone region with a wax and ink (4:1) mixture, and were marked in female lots in order to identify females in estrous. After ten days of breeding season onset, rams were again marked with the same wax and ink mixture, but with a different ink color. Pregnancy diagnosis was performed on day 30 by ultrasonography and confirmed on day 60 after the last mating. The statistical analysis was performed using SAS, version 8. Differences of 5% (P < 0.05) or lower were considered significant. The results show that estrous synchronization in the semiarid region in both breeds was detected in 10% of females. The total pregnancy on first service was 45.00% and on second was 52.94%, with 85.18% of singleton and 14.81% twin deliveries, with prolificacy de 1.15 ± 0.38. In the Zona da Mata region 10% Santa Inês and 15% Morada Nova females had synchronized estrous (P > 0.05). The total pregnancy was 42.50% on first, 64.70% on second service and total delivery was 86.20% singletons, 12.06% twins and 3.33% triples with prolificacy of 1.15 ± 0.31. On both Semiarid and Zona da Mata regions, the majority of estrous events occurred between the11th and 15th day of the breeding season for Santa Inês ewes and between 6th and 10th day for Morada Nova ewes. Discussion: The occurrence of estrous, for both breeds, in both regions, were detected throughout the breeding seasons, despite most estrous detections were within the initial fifteen days, which normally happens with cycling pluriparous females, in disagreement with findings in the literature that young females display lower reproductive performance on the first breeding season. However, the sexual inexperience of young females is not equivalent to lack of male receptivity, since then, could not be responsible for late ...

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“…dates of the first and last oestrus and the duration of anoestrus were respectively: in Iceland, at Hvanneyri (64°34'N), November, May and 219 days for the native Iceland breed (Dyrmundsson, 1978) (Wheeler & Land, 1977); in France, at Nouzilly (47°30'N), August, February and 164 days for Romanov, August, December and 210 days for Solognote ; in France, at Jouy-en-Josas (48°30'N), August, January and 179 days for Ile-de-France, July, March and 114 days for Préalpes du Sud (Thimonier & Mauléon, 1969). However, there are, in the literature, data that do not lead to the same conclusion: Hafez (1954) and Schäfer (1964) listed a number of breeds which reached the peak of their reproductive activity during the longest days, and Thimonier & Mauléon (1969) observed a short period of ovarian activity at the end of April or at the beginning of May and the first ovarian cycles in June, i.e.…”

Section: Discussionmentioning

confidence: 99%

Seasonal variations in the cyclic luteal ovarian activity in the Tadmit ewe in Algeria

Ammar-Khodja¹,

Brudieux²

1982

Reproduction

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Seasonal variations of the cyclic luteal activity were assessed by measurements of progesterone concentrations in peripheral plasma collected daily or every 4 days, throughout 15 months, in 16 Tadmit ewes, in Algeria. One female was cyclic at all times of the year; 15 ewes showed a period of cyclic luteal inactivity of less than 53 days in 10 animals and ranging between 2.5 and 3.5 months for the 5 others (mean duration 52 days). The onset of ovarian inactivity took place from the beginning of February to the end of April (mean data 19 March). The recovery of luteal function was much more definite; it occurred in May for 13 ewes (mean date for the 16 animals 10 May) when daylength was still increasing. These data suggest that at this latitude (36 degrees 30'N) and for this particular breed of sheep (Tadmit) declining daylength is not the major environmental stimulus for the resumption of breeding activity.

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Studies on the breeding season of Icelandic ewes and ewe lambs

Cited by 31 publications

References 16 publications

Frequency of estrus in Santa Inês, Texel and Ile de France ewes in the northwest of Paraná State, Brazil

Frequency of estrus in Santa Inês, Texel and Ile de France ewes in the northwest of Paraná State, Brazil

Role of Male effect on Reproductive Efficiency of Nulliparous Santa Inês and Morada Nova ewes raised in Different Regions

Seasonal variations in the cyclic luteal ovarian activity in the Tadmit ewe in Algeria

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