Embryo Mortality

Edey, T. N.

doi:10.1016/b978-0-408-10633-7.50041-1

Cited by 16 publications

(18 citation statements)

References 42 publications

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“…Moreover, unlike the usual situation in mature ewes (Edey, 1969) there were further significant losses of foetuses after day 40, reducing the 53 ewes apparently pregnant at day 40 (Table 7) to 38 pregnant at autopsy. Thirteen (25 %) of these ewes returned to service after intervals of 47-82 days, an exceptionally high proportion by mature ewe standards (Edey, 1976). Nevertheless, 23 of 61 ewe lambs mated at their puberal oestrus were in late gestation at autopsy, seven of them with twin foetuses, which confirms that there is no fundamental physiological barrier to pregnancy at this time.…”

Section: Discussionsupporting

confidence: 67%

Sexual behaviour and reproductive performance of ewe lambs at and after puberty

Edey¹,

Kilgour²,

Bremner³

1978

J. Agric. Sci.

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Observations were made on mating behaviour and reproductive performance during the puberal period in 61 well-grown Perendale (Cheviot x Romney) ewe lambs. In four animals, the first oestrus (as indicated by raddle marks) was not accompanied by ovulation, and three other lambs, though marked by the rams, were not inseminated.The behavioural responses to a ram, of ewe lambs experiencing oestrus for the first and second times, showed many signs of inadequacy by comparison with those of mature ewes. Individual ewe lambs and mature ewes in oestrus were exposed to a ram in a pen for 3 h, and their responses were ranked on a scale of 1 (full adult response) to 5 (weak response). Of mature ewes 95% scored 1, compared with only 27 % of ewe lambs. Across the lambs 59 % scored 3 or more, indicating failure of some aspects of the courtship sequences which are required to sustain and reinforce the ram's interest. In a paddock-mating system many lambs showed a strong tendency to disassociate themselves from the rams after each courtship and mating sequence. Consequently there was little evidence of harem formation. Fifty-six per cent of services came in the first 2 h of oestrus, only 14 % after the 6th hour and none after the 11th hour.Duration of the first oestrus in lambs was 18-4 h compared with 29-3 h in mature ewes. Mating the 61 ewe lambs over the first three cycles after puberty resulted in 38 of them being pregnant with 46 foetuses at autopsy in mid to late pregnancy. The success rate did not differ between cycles. c a t e d t h a t m a h i S h P r°P°rtio n °f studies only 6-2

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Section: Discussionsupporting

confidence: 67%

Sexual behaviour and reproductive performance of ewe lambs at and after puberty

Edey¹,

Kilgour²,

Bremner³

1978

J. Agric. Sci.

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“…more than 7 days after implantation; these deaths are similar in timing to those observed by Edey, Kilgour & Bremner (1978) in ewe lambs, most of which were carrying single fetuses. The lateness of the deaths suggests that they were not attributable to abnormalities of the fetus, a common cause of early loss (Edey, 1976), but rather to physical factors such as an inadequate blood supply.…”

Section: Discussionmentioning

confidence: 93%

“…Lamb production following matings within the breeding season is further limited by low ovulation rates (Hulet & Foote, 1967) and failures of fertilization and embryonic death (Edey, 1969(Edey, , 1976. Robinson, Fraser & McHattie (1975), using a combination of treat¬ ments, including controlled photoperiod, early weaning and pregnant mares' serum gonadotrophin (PMSG) injections, successfully eliminated seasonality and maintained a high level of lamb production from Finnish Landrace Dorset Horn ewes bred at 7-month intervals.…”

Section: Introductionmentioning

confidence: 98%

Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG

Rhind¹,

Robinson²,

Fraser³

et al. 1980

Reproduction

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Finnish Landrace x Dorset Horn ewes of two flocks comprising 47 and 51 animals were mated to Suffolk rams at a synchronized oestrus on 9 December (Flock D) and 8 April (Flock A) after treatment with 500 i.u. PMSG. The ewes were slaughtered between 50 and 145 days of pregnancy. The mean +/- s.e.m. ovulation rates were 4.5 +/- 0.24 (Flock D) and 5.0 +/- 0.32 (Flock A) for ewes which conceived to the induced oestrus and the corresponding litter sizes were 2.8 +/- 0.15 and 2.8 +/- 0.18. Mean concentrations of progesterone in the peripheral plasma during pregnancy were higher for Flock D than for Flock A ewes both in early (P less than 0.001) and late (P less than 0.05) pregnancy. An increase in ovulation rate, up to 4 or 5, was associated with an increase in mean litter size. There was evidence that higher ovulation rates were counterproductive.

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“…It appears that the embryos which do not survive affect the growth of those which do survive by restricting the availability of attachment points on the uterine wall. Thus management and nutrition factors which increase embryo mortality (Edey, 1976) are likely to increase variability in foetal weight and will result in foetuses of less than average weight for their litter size.…”

Section: Discussionmentioning

confidence: 98%

Studies on reproduction in prolific ewes:7. Variability in the growth of individual foetuses in relation to intra-uterine factors

McDonald¹,

Robinson²,

Fraser³

1981

J. Agric. Sci.

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The weights of 44 twin foetuses, 99 triplets and 44 quadruplets, varying in gestational age from 55 to 145 days, were studied in relation to age, sex, litter size, uterine position, placental structure and weight, and ovulation rate. Triplet and quadruplet foetuses were more variable in weight, within litters, than were twins. The difference increased with foetal age and was attributed to increased competition between foetuses which were located within the same horn of the uterus. The effect was largely associated with differences in placental development, i.e. numbers of cotyledons and weight, but those differences did not entirely account for the reduction in foetal weight with increasing litter size. Differences in placental development, arising from embryo mortality, also accounted for the reduction in foetal weight when ovulation rate exceeded litter size. In contrast, differences in foetal weight associated with the sex of the foetuses were only partly mediated by differences in cotyledon weight. Foetuses in the larger litters are thus not only lighter in weight but are more variable in weight, the increased variability being controlled by events in early pregnancy. ovulation rate, sex and maternal weight. The interactions between factors are shown by the The survival of new-born lambs and their growth change in the quantitative effect of one factor after rates up to weaning are partly dependent on their account is taken of others, individual weights at birth and also on the variation in weight between lambs from the same litter.MATERIALS AND METHODS Quantitative information on the influence of intrauterine factors on the growth in weight of sheep Foetuses foetuses is therefore of importance, especially inThe study was based on data for 187 foetuses, relation to large litters.consisting of 44 twins, 99 triplets and 44 quadThe effect of litter size on litter-mean foetal ruplets taken from 66 Finnish Landrace x Dorset weight was described by Robinson et al. (1977) on Horn ewes killed at between 55 and 145 days. Each the basis of a comparative slaughter experiment ewe had been mated to two out of a group of nine using prolific cross-bred ewes. The corresponding Suffolk rams. Details of management, diets and placental structures were described by Rhind, slaughter procedure were given by Robinson et al. Robinson & McDonald (1980) and were shown to (1977) and measurements made on the foetal be affected by litter size, by the distribution of the cotyledons were described by Rhind et al. (1980). foetuses between the two horns of the uterus and by the number of ovulations. It was indicated that Lamb birth w^t he variations in the number of foetal cotyledons, Subsidiary data on variability in weight between and in their total weight, were relevant to the litter-mate lambs at birth was obtained for 459 sets weights of the foetuses. A further detailed study of of twins, 222 of triplets and 26 of quadruplets from the individual foetal weights has now provided records kept in the Rowett Institute ewe house for quantitat...

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Embryo Mortality

Cited by 16 publications

References 42 publications

Sexual behaviour and reproductive performance of ewe lambs at and after puberty

Sexual behaviour and reproductive performance of ewe lambs at and after puberty

Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG

Studies on reproduction in prolific ewes:7. Variability in the growth of individual foetuses in relation to intra-uterine factors

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