Breed differences in ovulation rate and uterine efficiency and their contribution to fecundity

Meyer, H. H.

doi:10.1016/b978-0-407-00302-6.50023-4

Cited by 23 publications

(19 citation statements)

References 20 publications

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“…In the six flocks in which embryos or fetuses were counted in the E ewes, 19% (43 of 224 embryos) were not accounted for at lambing. This is in agreement with the mean of 19.6% loss of all embryos or fetuses from day 25 to parturition found by Dixon et al (2007) utilizing ultrasonography, and is similar to mean loss estimated by others looking at number of CL or embryos/fetuses not represented by lambs born (Meyer, 1985;Bolet, 1986;Kaulfuss et al, 1996).…”

Section: Resultssupporting

confidence: 91%

“…In agreement with other studies, higher loss was associated with multiple rather than single ovulators (Quinlivan et al, 1966;Meyer, 1985;Knights et al, 2003;Dixon et al, 2007). Thirty-eight percent of ewes with multiple ovulations in this study lost partial or total pregnancies compared to 8% of ewes ovulating singles.…”

Section: Analyses Of Ovulation Data Across Experimentssupporting

confidence: 92%

“…As ovulation rate increased, so did the number of ovulations not represented by live offspring at lambing (Rhind et al, 1980a, b;Meyer, 1985;Bradford et al, 1986;Dixon et al, 2007). Rhind et al (1980a) found that the proportion of ovulations represented by viable fetuses on day 60 or 145 of gestation was inversely related to ovulation rate.…”

Section: Introductionmentioning

confidence: 99%

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Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Wurst¹

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Ewes are polyestrous and litter-bearing seasonal breeders. Although average ovulation rates are sufficient, many ovulations do not result in live offspring and ewes normally breed only once per year. As ovulation rate increases, so does the number of ovulations not represented by live births. When ultrasonographic analysis is limited to ovarian follicles that grow from 3 to 5 mm, follicular waves can be identified in sheep. In most cases, ovulatory follicle(s) develop from the ultimate follicular wave; however, ovulatory follicles can be derived from penultimate or earlier follicular waves. The relationship between lifespan of large follicles and fertility is controversial in sheep. In experiment 1, three approaches to create a model to compare fertility when ovulatory follicles developed from only the ultimate follicular wave or both ultimate and penultimate waves were tested. Ewes were treated on d 10 or 11 with 50 μg of GnRH i.m., the largest follicle(s) (≥ 4 mm) on each ovary were electrocauterized, or ewes were treated with 50 µg estradiol benzoate and 50 mg progesterone or 100 µg estradiol benzoate and 50 mg progesterone in attempts to induce follicular regression or luteinization. Corpora lutea were counted by ultrasound 7 days following estrus in order to verify ovulation of follicles that disappeared post estrus. Pregnancy was determined and embryos were counted 20 to 30 days following estrus. Neither treatment with GnRH nor estradiol and progesterone consistently caused regression or luteinization of ovulatory-sized follicles. Follicular ablation was successful in increasing the proportion of ovulations originating from the ultimate follicular wave in Dorset/Suffolk cross ewes, but did not alter the proportions of ovulations fom different waves in Polypay ewes. Average age of the ovulatory follicle was affected only in Dorset/Suffolk cross ewes. Due to lack of treatment effects, ovulatory follicles were evaluated regardless of treatment for effects on embryonic or fetal losses. Although loss tended to differ among follicular age combinations and wave sources of ovulatory follicles within ewes, older follicles did not have worse outcomes than younger follicles. Lactating ewes have not responded to treatments for the induction of estrus that are effective in dry ewes during the anestrous season. In experiment 2, lactating anestrous ewes 26 to 71 days postpartum were treated with either 25 or 50 mg progesterone/day for five days before ram introduction (RI). Twelve hours after RI, lambs were removed from half of the ewes in each group for 72 hours. Estrous response was recorded and ewes were scanned by transrectal ultrasonography on days 8 and 35 to 45 to determine ovulation rate, and pregnancy rate and number of embryos/fetuses, respectively. Number of lambs born was recorded at lambing. No effect of lamb removal was found for any variable examined. However, the lower dosage of progesterone reduced the mean time to estrus, increased the proportion of ewes ovulating, and decreased an incredible work ethic ...

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Section: Resultssupporting

confidence: 91%

Section: Analyses Of Ovulation Data Across Experimentssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Wurst¹

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“…However, there may be other more subtle aspects to the relation¬ ship between embryo and uterus. Several studies of sheep suggest that survival is maximal if ovu¬ lation has occurred from both ovaries (Doney, Gunn & Smith, 1973;Meyer, 1985). There appears to be a small price to pay for being in a uterine horn contralateral to the corpora lutea, but a greater penalty if embryos are crowded into one horn (Doney et al, 1973).…”

Section: An Inappropriate Relationshipmentioning

confidence: 99%

Maternal and embryonic factors associated with prenatal loss in mammals

Wilmut¹,

Sales²,

Ashworth³

1986

Reproduction

204

104

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“…Wang (1981) reported that the long uterus of Chinese Fenjing pigs was one of the physiological reasons for their high prolificacy. Meyer (1987) thought that ovulation rate and uterine efficiency differences contributed to the breed difference observed in litter size.…”

Section: Discussionmentioning

confidence: 99%

Development of Reproductive System and Levels of Sexual Hormones in Blood Plasma in Chinese Hu Sheep Ewe Lambs

Yue

Cheng

1996

Reprod Domestic Animals

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Breed differences in ovulation rate and uterine efficiency and their contribution to fecundity

Cited by 23 publications

References 20 publications

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Maternal and embryonic factors associated with prenatal loss in mammals

Development of Reproductive System and Levels of Sexual Hormones in Blood Plasma in Chinese Hu Sheep Ewe Lambs

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