Genetic variation in ovulation rate in sheep

Hanrahan, J. P.

doi:10.1016/b978-0-408-10134-9.50009-1

Cited by 18 publications

(14 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The high variation in ovulation rate (range [1][2][3][4][5][6][7][8] and litter size (range 1-7) combined with high repeatabilities are characteristic of flocks where a major gene is segregating. The repeatability of ovulation rate was 0.8 which is similar to that recorded in Javanese (0.6, [5]), Booroola (0.6-0.7, [7]), Cambridge (0.7, [17]), and Icelandic (0.6-0.8, [14]) sheep, which are all breeds with segregating major genes for prolificacy. These observations together with evidence of Mendelian inheritance of prolificacy in progeny, led Malher and Le Chere [25] to hypothesise that an autosomal major gene for prolificacy is segregating in this breed.…”

Section: Belle-ilesupporting

confidence: 58%

Major genes affecting ovulation rate in sheep

Davis

2005

Genet. Sel. Evol.

View full text Add to dashboard Cite

-Research conducted since 1980 in relation to inheritance patterns and DNA testing of major genes for prolificacy has shown that major genes have the potential to significantly increase the reproductive performance of sheep flocks throughout the world. Mutations that increase ovulation rate have been discovered in the BMPR-1B, BMP15 and GDF9 genes, and others are known to exist from the expressed inheritance patterns although the mutations have not yet been located. In the case of BMP15, four different mutations have been discovered but each produces the same phenotype. The modes of inheritance of the different prolificacy genes include autosomal dominant genes with additive effects on ovulation rate (BMPR-1B; Lacaune), autosomal over-dominant genes with infertility in homozygous females (GDF9), X-linked overdominant genes with infertility in homozygous females (BMP15), and X-linked maternally imprinted genes (FecX2). The size of the effect of one copy of a mutation on ovulation rate ranges from an extra 0.4 ovulations per oestrus for the FecX2 mutation to an extra 1.5 ovulations per oestrus for the BMPR-1B mutation. A commercial DNA testing service enables some of these mutations to be used in genetic improvement programmes based on marker assisted selection. major gene / ovulation rate / sheep / reproduction

show abstract

Section: Belle-ilesupporting

confidence: 58%

Major genes affecting ovulation rate in sheep

Davis

2005

Genet. Sel. Evol.

View full text Add to dashboard Cite

show abstract

“…Thus, on the one hand, melatonin is a highly repeatable and heritable characteristic and, on the other hand, the dates of (a) the onset of the annual breeding season [21][22][23] and of (b) the offset of the annual breeding season are very variable among ewes but very repeatable within individuals [23].…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

-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

show abstract

“…The present study clearly demonstrates that Sicilo‐Sarde ewes have a seasonal pattern of oestrous behaviour and ovarian activity, but this seasonality is reduced when compared with breeds of more temperate regions [Tasmanian Merino in Scotland (Wheeler and Land, ); Scottish Blackface (Hanrahan, )]. Some features of these findings are important to consider.…”

Section: Discussionmentioning

confidence: 48%

Seasonality of oestrus, ovulation and ovulation rate of Sicilo‐Sarde sheep

Lassoued

Rekik²,

Khenissi

et al. 2013

Animal Physiology Nutrition

View full text Add to dashboard Cite

This study aimed to investigate monthly changes in oestrus and ovulatory activity of Sicilo-Sarde sheep. Experimental animals comprised 25 adult and 10 maiden ewes at the start of the experiment. For 12 consecutive months (September-August), the females were exposed to natural photoperiod and permanently kept in presence of seven aproned rams. Oestrus was checked daily and ovarian activity was monitored by monthly endoscopies during the last week of each month. Ovulation rate for a particular month was assessed as the sum of corpora lutea or corpora albicans present on both ovaries at the time of endoscopy. Proportions of ewes observed in oestrus at least once a month were lowest in March (24.3%) and highest in June and October (100%). They tended (p < 0.06) to be different according to age, dropping during summer from a common value of 100% in June to 85.7% and 90% in July and then to 57.1% and 70% in August for, respectively, the Adults and Maiden females. Overall, the experimental period, 92.5% and 83.8% of Adult and Maiden ewes ovulated at least once per month (p < 0.01) respectively. Least proportions ovulating, attained 60% and 30% in April for, respectively, Adult and Maiden ewes before peaking up at 100% again in May (p < 0.05). Mean (±SD) ovulation rate of Sicilo-Sarde sheep is 1.40 ± 0.503. Adult females had a higher (p < 0.001) ovulation rate than Maiden sheep with respective average values of 1.51 ± 0.516 and 1.16 ± 0.373. It varied little between months and decreased in Adults from a maximum value of 1.95 in October to a minimum value of 1.16 in April. It is concluded that benchmarking seasonal variations of reproductive activity in Sicilo-Sarde breed would be valuable in designing improved management calendars for this breed.

show abstract

Genetic variation in ovulation rate in sheep

Cited by 18 publications

References 18 publications

Major genes affecting ovulation rate in sheep

Major genes affecting ovulation rate in sheep

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

Seasonality of oestrus, ovulation and ovulation rate of Sicilo‐Sarde sheep

Contact Info

Product

Resources

About