Association of ovulation rate and twinning in Merino sheep

Packham, Analisa; Triffitt, L. K.

doi:10.1071/ar9660515

Cited by 9 publications

(2 citation statements)

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“…The response has been described by Turner et al (1962) and Turner (1966Turner ( , 1968Turner ( , 1969 in Peppin Merinos in which the difference in lambing rate appears to be due primarily to a correlated response in natural ovulation rate. Mean differences between groups selected for and against multiple births vary from 0·4 to 0·9 corpus luteum for ewes of various ages (Packham and Triffitt 1966;Bindon et al 1971;Trounson and Moore 1972).…”

Section: Introductionmentioning

confidence: 99%

Primordial Follicle Numbers in Ovaries and Levels of LH and FSH in Pituitaries and Plasma of Lambs Selected for and against Multiple Births

Trounson¹,

Wa²,

Kennedy³

et al. 1974

Aust. Jnl. Of Bio. Sci.

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The numbers of primordial follicles in ovaries of ewe lambs, from two groups of Peppin Merinos that had been selected for (T group) and against (0 group) mUltiple births, were estimated at birth, 7 days and 5 months of age. Peripheral plasma and anterior pituitary levels of LH and FSH were determined by radioimmunoassay in the lambs at 5 months of age. These lambs were either entire or unilaterally ovariectomized (hemispayed) at 7 days of age.There was no difference in primordial follicle numbers between lambs at birth and 7 days of age, but when paired ovaries of hemispayed lambs at 7 days and 5 months of age were compared there was a significant increase in follicle numbers with age (34903 v. 48047). O-group lambs had more primordial follicles than T-group lambs at birth and 7 days of age (65501 v. 37797) and there was a similar but not significant difference at 5 months of age (53934 v. 44057).Peripheral plasma LH was higher in T-group than in O-group lambs and plasma LH levels were correlated to pituitary LH content (r = o· 75). Vesicular follicles larger than 2 mm in diameter were present only in ovaries of lambs with plasma LH levels above 3· 0 ng/m!. Pituitary FSH levels were considerably higher in hemispayed lambs than in entire lambs and there was a trend to higher levels in T-group lambs when compared with O-group lambs.It is concluded that genetic selection for the incidence of multiple births has resulted in changes in the number of ovarian primordial follicles of the post-natal lamb and it is suggested that these changes may be related to the levels of pituitary gonadotrophins.

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Section: Introductionmentioning

confidence: 99%

Primordial Follicle Numbers in Ovaries and Levels of LH and FSH in Pituitaries and Plasma of Lambs Selected for and against Multiple Births

Trounson¹,

Wa²,

Kennedy³

et al. 1974

Aust. Jnl. Of Bio. Sci.

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“…There is evidence (Watson and Radford, 1966;Packham and Triffitt, 1966) to show that heredity influences several components of fertility such as length of breeding season, ovulation rate and foetal mortality though little is known about their heritability or behaviour in breed crosses. In the present trial, the Tasmanian Merino and the Finnish Landrace may have differed in ovulation rate only, or in other respects as well.…”

Section: Numbers Of Lambs Born and Rearedmentioning

confidence: 99%

A comparative trial of crossbred ewes by Finnish Landrace and other sires

Donald¹,

Read²,

Russell³

1968

Anim. Sci.

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1. A comparison lasting 3 years has been made of 5 types of crossbred ewes produced by mating Border Leicester, Clun Forest, Dorset Horn, Finnish Landrace and Tasmanian Merino rams to Scottish Blackface ewes. Data from a total of 576 ewe years became available.2. In body weight at mating time when they were 7, 19 or 31 months old, the Border Leicester and Dorset Horn crossbred ewes were heaviest, followed by Cluns. Finnish and Merino crossbreds were about 15–20% lighter than the Border Leicester crossbreds.3. In fleece weight, Finnish crossbreds were lower by about 1·0—1·5 lb relative to Border Leicester crossbreds.4. In fertility, Finnish crossbreds were highest with 1·5, 2·0 and 2·3 lambs born per ewe lambing at ages 1, 2 and 3 years respectively. The corresponding averages for the combined Border Leicester, Clun and Dorset Horn crossbreds were 1·1, 1·6 and 1·6 and for Merino crossbreds 1·0, 1·1 and 1·2. Numbers weaned were similarly ranked.5. Lambs out of crossbred ewes showed a sequence of group differences in weight at birth and at weaning corresponding to those shown by their mothers at mating time. The heaviest lambs were produced by Dorset Horn and Border Leicester crossbreds, and the lightest by Merino crossbreds. As a percentage of ewe weight at mating, lamb weight at weaning was highest for the Finnish group.6. In terms of litter weight at weaning, fitted values for the Merino group were the lowest while those for the Finnish group were the highest. The other three groups gave similar and intermediate values.

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Estimates of early embryonic loss in ewes mated to rams selected for high and low prolificacy

1977

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Association of ovulation rate and twinning in Merino sheep

Abstract: Merino sheep from two groups selected for single and multiple births were examined by laparotomy. Comparison of observed corpora lutea with previous lambing records suggests that differences in fecundity obtained by selection are due to genetic differences in number of eggs shed.

Cited by 9 publications

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Primordial Follicle Numbers in Ovaries and Levels of LH and FSH in Pituitaries and Plasma of Lambs Selected for and against Multiple Births

Primordial Follicle Numbers in Ovaries and Levels of LH and FSH in Pituitaries and Plasma of Lambs Selected for and against Multiple Births

A comparative trial of crossbred ewes by Finnish Landrace and other sires

Estimates of early embryonic loss in ewes mated to rams selected for high and low prolificacy

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