Influence of Hereditary and Environmental Factors on Twinning in Sheep

Vakil, D. V.; Botkin, M. P.; Roehrkasse, G. P.

doi:10.1093/oxfordjournals.jhered.a107711

Cited by 6 publications

(8 citation statements)

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“…A positive relationship between prolificacy of female relatives and litter size produced by the ram has been shown previously by Vakil et al (1968) who found an increase of 0-12 lambs born per ewe lambing to twin-born rams compared with single-born rams. Burfening, Friedrick & Van Horn (1977) have reported that rams selected for high prolificacy (on the basis of their dams' lambing records) produced more lambs born per randomly selected ewe mated than did rams selected for low prolificacy.…”

Section: Discussionsupporting

confidence: 67%

“…Vakil, Botkin & Roehrkasse (1968) showed that this ram effect was correlated with the prolificacy of the female relatives. It was suggested by Bradford (1972) that rams may contribute to variation in the litter size of their mates through differences in the fertilizing capacity of their semen or in the pre-natal survival of their offspring.…”

Section: Introductionmentioning

confidence: 96%

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Fertilizing ability of semen from rams of high- and low-prolificacy flocks

Moore¹,

Whyman²

1980

Reproduction

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The difference between fresh undiluted ram semen from high (H) and low (L) prolificacy Romney selection lines in success in fertilizing artificially inseminated Romney, half-Romney and Cheviot ewes (unrelated and randomly allocated) was examined in 3 experiments. For ewes producing natural multiple ovulations, the fertilization rate was 71% (40/56) and 40% (20/50) for semen from H rams and L rams respectively (P < 0.01). Fertilization rates for PMSG-induced multiple-ovulating ewes were 61% (11/18) for H semen and 22% (4/18) for L semen (P > 0.05). Values for single-ovulating ewes were 52% (35/67) for H semen and 50% (28/56) for L semen (P > 0.05).

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Section: Discussionsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 96%

Fertilizing ability of semen from rams of high- and low-prolificacy flocks

Moore¹,

Whyman²

1980

Reproduction

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“…Inskeep et al (1967) report peak production in number of lambs at 4 years of age. Vakil et al (1968) found the lambing percentage to increase up to an age of 5-7 years.…”

Section: Hrtrmber Of Lonibs Per Ewementioning

confidence: 95%

Studies on Sheep Production Records

Eikje

1971

Acta Agriculturae Scandinavica

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“…It has been found that rams which are themselves twins are more likely to sire twins than are single-born rams (Vakil, Botkin & Roehrkasse, 1968). It was suggested by Bradford (1972) that this may be due either to an increased fertilizing power of their semen, or to a decreased rate of embryonic mortality among their offspring.…”

Section: Probability Of Fertilizationmentioning

confidence: 99%

Second survey Of secular trends in twinning rates

James

1982

J. Biosoc. Sci.

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SummaryA study has been made of twinning rates throughout the world over the last two decades. There has been a decline in age-specific dizygotic twinning rates in almost all of the developed countries during this period. Exceptions to this trend are provided by the United States, where the only decline in twinning rates in the last two decades was in births to older women in the 1960s, and by Czechoslovakia, Hungary and Bulgaria, where an initial decline in twinning during the 1960s was followed by stable twinning rates.It is suggested that the cause may be some form of environmental pollutant, perhaps a pesticide, which has been the subject of restrictive legislation first in the United States and later in the three Communist countries. Possibly the cause of this decline may be identified by a study of such legislation.This seems to be the first study of twinning rates in Central and South America. The low twinning rates in some of the countries there may indicate the genetic affiliations of their inhabitants with those (of Mongoloid origin) of countries in the Far East.

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Influence of Hereditary and Environmental Factors on Twinning in Sheep

Cited by 6 publications

References 0 publications

Fertilizing ability of semen from rams of high- and low-prolificacy flocks

Fertilizing ability of semen from rams of high- and low-prolificacy flocks

Studies on Sheep Production Records

Second survey Of secular trends in twinning rates

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