Seasonality of ovulation and estrus, and the ram effect in poll dorset ewes

Hall, DG; Fogarty, NM; Gilmour, AR

doi:10.1016/0093-691x(86)90055-5

Cited by 25 publications

(18 citation statements)

References 8 publications

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“…Ovarian and estrous activity in Dorset ewes have been shown to follow a similar pattern (Phillips et al, 1984;Hall et al, 1986). In these data, approximately 20% of ewes exposed in spring conceived.…”

Section: Discussionsupporting

confidence: 51%

Ewe fertility in the STAR accelerated lambing system.

Lewis

Notter

Hogue

et al. 1996

Journal of Animal Science

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Effects of environmental factors such as ewe age, season of exposure, and time from lambing to exposure on fertility were evaluated using records on 1,084 Dorset ewes in the STAR accelerated lambing system. The STAR program consisted of five 30-d concurrent breeding and lambing periods per year beginning on January 1, March 15, May 27, August 8, and October 20. Fertility in the flock changed in a cyclic and predictable fashion during the year. Changes in prolificacy were less consistent but also tended to show cyclic variation. Matings that occurred within the typical breeding season (August, October, and January) were more fertile than those occurring in March and June. However, fertility also varied with the age of the ewe and the time since the ewe's last lambing. Except in June, fertility at the first postpartum mating increased as ewes aged. In March and June matings, adult ewes that had just weaned lambs were less fertile than ewes that had failed to conceive in the previous season and therefore had longer postpartum intervals. However, in October and January, ewes that had just weaned lambs were more fertile. A matrix of expected pregnancy rates, or probabilities of fertility, was constructed using a mixed GLM to describe the combined effect of season, ewe age, and time since lambing on ewe fertility in accelerated lambing.

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Section: Discussionsupporting

confidence: 51%

Ewe fertility in the STAR accelerated lambing system.

Lewis

Notter

Hogue

et al. 1996

Journal of Animal Science

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“…In the current studies, variability in oestrus rates of untreated Control groups was observed with the proportion of ewe lambs marked by rams being 8.6% or 42.1% after 7 or 21 days, respectively, after joining with rams for Experiments 3 and 4. This variability could be due to breed of the animals and/or location as the group of ewe lambs with the increased proportion expressing oestrus were closer to the equator and thus potentially less affected by seasonal anoestrus (Rosa and Bryant, 2003) and were 50% Dorset, a breed known for an extended breeding season (Hall et al, 1986). The proportion of prepubertal ewe lambs ovulating after the U-synch treatment (95.4%; Experiment 3) was similar to that observed during the breeding season in which ewe lambs received a 12-day CIDR treatment and 300 IU eCG (98%) or no treatment (Controls; 83%) (McMillan, 1986).…”

Section: Discussionmentioning

confidence: 98%

Successful induction of oestrus, ovulation and pregnancy in adult ewes and ewe lambs out of the breeding season using a GnRH+progesterone oestrus synchronisation protocol

Martı́nez

McLeod²,

Tattersfield

et al. 2015

Animal Reproduction Science

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“…Dorset flocks have an extended breeding season with some ewes cycling at all months of the year, although there is a higher ovulation rate in the autumn than other seasons (Phillips et al 1984;Hall et al 1986). This would have contributed to the higher litter size amongst the autumn joined ewes in our study.…”

Section: Reproductive Performancementioning

confidence: 98%

“…Plant et al (1976) reported lamb marking percentages ranging from 25% to 135% in 15 Dorset flocks, with only two over 90% and identified a wide range of causes of low reproductive rate. The Dorset has an extended breeding season and high ovulation rate [peak of 1.6-1-9 (Phillips et al 1984;Hall et al 1986)] and litter size [1.7 (Haughey et al 1985) and 1 . 4 (Hall et al 1993)l.…”

Section: Introductionmentioning

confidence: 99%

Reproductive performance and genetic parameters for Australian Dorset Sheep

Brash¹,

Fogarty²,

Gilmour³

1994

Aust. J. Agric. Res.

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Reproductive performance of ewes in a large Dorset stud flock is reported. The data included 2488 ewes with 10016 joining records over 25 years. Average performance for reproductive traits were: fertility 92%, litter size 1.31, neonatal lamb survival 91%, lamb survival to weaning 85%, with overall lambs born 1.20 and lambs weaned 1.02 per ewe joined. Differences between breeds (Poll Dorset and Dorset Horn), season of birth (spring and autumn) and season of joining (spring and autumn) were significant for most reproduction traits. Linear and quadratic regressions for age of ewe at joining were highly significant for all traits (P < 0.001) with maximum performance between three and six years of age.Estimates of heritability for ewe reproductive traits were: 0.062~ 0-02 for number of lambs born and 0.04f0.01 for number of lambs weaned per ewe joined, and component traits, 0 . 0 2 f 0 -01 for fertility, 0 0 8 f 0 -02 for litter size and 0 -0Of 0.01 for lamb survival. Estimates of repeatability were less than 0.14 for all the reproduction traits, which resulted in substantially higher predicted heritabilities when repeated records were used. Heritability estimates for average ewe lifetime performance, with approximately four records, were 0.O8f 0 06 for lambs born, 0 . 1 2 f 0.05 for lambs weaned, O.O8f 0 -04 for fertility, O . l 9 f 0 -04 for litter size and zero for lamb survival. The genetic correlations between litter size and lambs born and weaned were close to unity, whereas those for fertility were lower and declined from lambs born ( 0 . 6 l f 0.22) to lambs weaned (0 -4 5 f 0.30). The estimated heritability for ewe longevity, defined as the number of years the ewe remained in the breeding flock, was 0-OGf 0-03.The potential for genetic improvement in reproductive rate is discussed in relation to other reports in the literature and in the context of the roles of the Dorset breed in the Australian lamb industry. Increased reproductive rate in Dorset flocks impacts on stud profitability and the rate of genetic improvement from selection for other traits such as liveweight. The parameter estimates derived will be used in compiling breed-specific parameter sets for genetic evaluation in LAMBPLAN,

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Seasonality of ovulation and estrus, and the ram effect in poll dorset ewes

Cited by 25 publications

References 8 publications

Ewe fertility in the STAR accelerated lambing system.

Ewe fertility in the STAR accelerated lambing system.

Successful induction of oestrus, ovulation and pregnancy in adult ewes and ewe lambs out of the breeding season using a GnRH+progesterone oestrus synchronisation protocol

Reproductive performance and genetic parameters for Australian Dorset Sheep

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