Duration of the seasonal anestrus in sheep selected for fertility in a fall-lambing system.

Vincent, J. N.; McQuown, E. C.; Notter, D. R.

doi:10.2527/2000.7851149x

Cited by 19 publications

(20 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In addition, the ability of the March-lambing, lactating ewes to deliver fully developed lambs at term was compromised. Levels of fertility achieved by spring-bred lactating OOS ewes in this study appear to be unprecedented for temperate sheep breeds, and are consistent with results of Vincent et al (2000), Notter et al (2011) and Goff et al (2013) demonstrating that selection for fertility in May and June has extended the breeding season until at least early summer. The OOS ewes were more likely to mate and establish pregnancy during lactation than St. Croix ewes, but these advantages were negated by their lower ability to maintain those pregnancies.…”

Section: Discussionsupporting

confidence: 72%

“…Attempts to breed lactating ewes in spring have consistently been disappointing (Bourke, 1964;Whiteman et al, 1972;Cognie et al, 1975;Pope et al, 1989), and use of hormone or light manipulation to improve spring fertility has generally not been successful in lactating ewes (Restall et al, 1978;de Nicolo et al, 2006;Martemucci and D'Alessandro, 2010). Selection to improve ewe fertility in a crossbred (50% Dorset, 25% Rambouillet, 25% Finnish Landrace) sheep population mated in May and June at Virginia Tech (37°N latitude) resulted in significant selection response (Notter and Cockett, 2005) and correlated increase in duration of the breeding season (Vincent et al, 2000;Notter et al, 2011;Goff et al, 2013). However, fertility of ewes from this out-of-season breeding (OOS) line has not been evaluated during lactation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Strategies for rapid rebreeding of lactating ewes in the spring

Goff

Notter

Vanimisetti

et al. 2014

Animal

View full text Add to dashboard Cite

Rapid rebreeding of winter-and spring-lambing ewes is essential if ewes are to lamb more than once per year, but fertility of lactating ewes is often low and early weaning of lambs may be undesirable in forage-based production systems. Selection to improve fertility in spring matings has been successful and led to development of ewes with a reduced seasonal anestrus. Potential for rapid rebreeding of lactating out-of-season breeding (OOS) ewes was tested in three studies. In Experiment 1, effects of short-term lamb removal on rebreeding was evaluated over 2 years using 71 January-lambing OOS ewes. At an average of 63 days postpartum, 36 ewes had lambs removed for 72 h, and all ewes were joined with rams. Circulating progesterone levels indicated that 74% of ewes ovulated before lamb separation; 91% of ewes mated within 5 weeks of ram exposure, 85% were diagnosed as pregnant and 75% lambed. The average interval between lambings was 225 days. In contrast to results observed in cattle, none of the measured variables was affected by lamb separation ( P > 0.20). Experiment 2 compared rebreeding performance of 24 OOS and 23 St. Croix ewes that lambed in January and averaged 60 days postpartum at ram introduction. More OOS ewes ovulated, mated and became pregnant during the first 21 days of ram exposure (83.3%, 58.3%, and 41.7%, respectively; P < 0.001) compared with St. Croix ewes (26.1%, 0%, and 0%, respectively). After 39 days of ram exposure, pregnancy rates still favored OOS ewes (66.7% v. 39.1%; P = 0.06), but the percentage of ewes that lambed did not differ ( P > 0.20) between OOS (47.8%) and St. Croix ewes (34.8%). In the third study, 34 March-lambing OOS ewes were exposed to rams on May 3 at an average of 40 days postpartum to characterize their reproductive performance. After 39 days of ram exposure, 52.9 ± 8.7% of the ewes had mated, and 38.2 ± 8.5% were diagnosed as pregnant. However, only 20.6 ± 7.0% of the ewes produced viable lambs, suggesting a high level of uterine insufficiency. Spring fertility of lactating OOS ewes in these studies was one of the highest reported in the literature and indicated that selection for fertility in spring mating would improve reproductive performance in accelerated lambing programs. However, exposure of lactating OOS ewes to rams at 30 to 50 days postpartum was associated with high prenatal lamb mortality.

show abstract

Section: Discussionsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Strategies for rapid rebreeding of lactating ewes in the spring

Goff

Notter

Vanimisetti

et al. 2014

Animal

View full text Add to dashboard Cite

show abstract

“…In ewes evaluated in 1992, 1993, and 1995, the seasonal anestrus of high-fertility ewes from the S and E lines (mean EBV of 12.6%) averaged only 28.4 d and was significantly shorter than the 70.1 d of anestrus observed in low-fertility ewes (mean EBV of 0.3%). Vincent et al [46] further reported that 13 OOS ewes evaluated in 1997 all exhibited nearly continuous cyclicity during spring and summer, with a mean period of anestrus of only 11.3 d.…”

Section: Characterization Of Oos Ewesmentioning

confidence: 99%

“…mid-January through the following July and monitoring their mating behavior [46]. Only ewes that had lambed in the previous autumn (October and November) were used to ensure physiological comparability, and the same rams were used throughout the study to avoid possible induction of ram effect by introduction of novel males.…”

Section: Characterization Of Oos Ewesmentioning

confidence: 99%

Opportunities for detection and use of QTL influencing seasonal reproduction in sheep: a review

Notter

Cockett

2005

Genet Sel Evol

View full text Add to dashboard Cite

-Genetic improvement in traits associated with seasonal breeding in sheep is challenging because these traits have low heritabilities, are generally not expressed until late in life, are commonly recorded only in females, and are expressed only in some lambing seasons and management systems. Detection of quantitative trait loci and their use in markerassisted selection could therefore substantially enhance selection responses. A population of sheep with an extended breeding season was developed through selection for fertility in spring matings and provides opportunities for further study of candidate genes influencing seasonal breeding. In particular, the melatonin receptor 1a gene is polymorphic in many sheep breeds and appears to influence a number of seasonal reproductive responses. In addition, a variety of clock genes have been identified in laboratory mammals and shown to influence biological rhythms. Mutations in these clock genes have been identified and shown to influence circadian periodicities and reproductive patterns in golden hamster and mouse. In sheep, expression of clock genes in the suprachaismatic nucleus and pars tuberalis (PT) suggests that "calendar" cells in the ovine PT play a role in maintaining circannual rhythms. Thus the various clock genes represent potentially important candidate genes that may be involved in control of seasonal breeding.sheep / seasonal breeding / selection / melatonin receptor la / clock genes

show abstract

“…The genetic basis of OOS kidding has not previously been explored in depth in dairy goats, however, several studies in sheep have found a genetic component to traits related to seasonality (Quirke et al, 1986;Chemineau et al, 2010), and selection for fall lambing has been achieved (Vincent et al, 2000). Smith et al (1992) estimated a heritability of 0.23 for seasonal breeding ability, based on a binary trait of successful/unsuccessful breeding in the late spring/summer months.…”

Section: Out Of Season Breedingmentioning

confidence: 99%

Pseudopregnancy and aseasonal breeding in dairy goats: genetic basis of fertility and impact on lifetime productivity

Desire

Mucha

Coffey

et al. 2018

Animal

View full text Add to dashboard Cite

Until recently, the main selection focus in UK dairy goats has been on milk yield. To develop a selection index suitably weighted for a variety of traits, it is important to understand the genetic relationships between production, health and fertility traits. This study focussed on three aspects of reproduction that are of interest to goat breeders. (1) Out of season (OOS) kidding ability: goats are highly seasonal breeders so achieving consistent, year-round dairy production presents a challenge. It may be possible to select for extended or shifted breeding cycles, however, there are no published studies on the genetic basis of seasonal kidding ability, and a genetic correlation with milk production in dairy goats; (2) age at first kidding (AFK): a reduced AFK offers the opportunity for more rapid genetic improvement, as well as reducing the amount of time and resources required to raise the animals to producing age; (3) pseudopregnancy (PPG): as it is difficult to diagnose pregnancy within 30 days of mating, high herd levels of PPG could add a significant delay in breeding replacement animals, or commencing a new lactation. Using records from 9546 goats, the objective of this study was to investigate the genetic relationships between the reproductive traits described above, and the production traits 520-day milk yield (MY520), lifetime milk yield (MYLife) and lifetime number of days in milk (DIMLife). The 'out of season' phenotype was defined as week of kidding relative to the 4 weeks of the year where the highest average number of births occur. Incidences of PPG that occurred during the first lactation were used as cases, while goats with none were assigned as controls. Relevant fixed and random effects were fitted in the models. In line with other reproduction traits, heritability estimates were low ranging from 0.08 to 0.11. A negative genetic correlation was found between AFK and MY520 (−0.22 ± 0.10), whereas a positive genetic correlation was found between PPG and DIMLife (0.58 ± 0.11). Pseudopregnancy and OOS were positively genetically correlated (0.36 ± 0.15). All other genetic correlations were very low. The results of this study indicate that selection for the reproductive traits analysed is feasible, without adversely affecting MYLife.

show abstract

Duration of the seasonal anestrus in sheep selected for fertility in a fall-lambing system.

Cited by 19 publications

References 16 publications

Strategies for rapid rebreeding of lactating ewes in the spring

Strategies for rapid rebreeding of lactating ewes in the spring

Opportunities for detection and use of QTL influencing seasonal reproduction in sheep: a review

Pseudopregnancy and aseasonal breeding in dairy goats: genetic basis of fertility and impact on lifetime productivity

Contact Info

Product

Resources

About