Seasonal differences in lamb birthweight do not arise from inherent differences in the oocyte and/or early embryo

2002 ◽  
Vol 14 (4) ◽  
pp. 207 ◽  
Author(s):  
L. M. Mitchell ◽  
M. Silveira ◽  
M. J. A. Mylne ◽  
K. Matthews ◽  
W. S. Dingwall
Keyword(s):  
Embryo Transfer ◽  
Breeding Season ◽  
Artificial Insemination ◽  
Close Relationships ◽  
Blastocyst Stage ◽  
Early Embryo ◽  
Seasonal Effects ◽  
Corpora Lutea ◽  
Seasonal Differences ◽  
Conceptus Development

The aim of this study was to determine whether previously observed seasonal differences in conceptus development in ewes are attributable to inherent differences in the oocyte and/or early embryo. Day 6 embryos were recovered from 50 ewes subjected to a standard oestrus synchronization, superovulation and laparoscopic artificial insemination protocol during October (peak breeding season) and April (transition to anoestrus). During the following October, 40 grade 1 and 2 embryos from each month, which had been cryopreserved at the late morula or unexpanded blastocyst stage, were thawed and transferred in singleton to synchronous recipients. Resulting pregnancies were monitored to term. For ewes receiving October- and April-produced embryos, overall mean SEM liveweight at the time of embryo transfer was 72 number of corpora lutea on the ovaries was 2.7 pregnant and their gestation lengths were 147 production on peripheral ovine pregnancy-associated glycoprotein concentrations during pregnancy or on fetal and placental characteristics at term, but, for each month, male lambs were heavier than females and were associated with larger placentae. Lamb birthweight was positively correlated with placental weight (r2 = 0.474, P<0.001) and the total weight of cotyledonary tissue (r2 = 0.429, P<0.001), but not to the number of cotyledons. Results demonstrate close relationships between fetal and placental weights at term, and that seasonal effects on conceptus development in ewes do not arise from inherent differences in the oocyte and/or early embryo.

Seasonal effects on ovarian responsiveness to exogenous gonadotrophins and successful artificial insemination in the snow leopard (Uncia uncia)

1997 ◽  
Vol 9 (3) ◽  
pp. 285 ◽  
Author(s):  
Terri L. Roth ◽  
Doug L. Armstrong ◽  
Michael T. Barrie ◽  
David E. Wildt
Keyword(s):  
Breeding Season ◽  
Artificial Insemination ◽  
Oocyte Quality ◽  
Chorionic Gonadotrophin ◽  
Seasonal Effects ◽  
Corpora Lutea ◽  
Snow Leopard ◽  
Follicular Aspiration ◽  
Snow Leopards ◽  
Breeding Seasons

Ovaries of the seasonally-breeding snow leopard (Uncia uncia) were examined to determine whether they were responsive to exogenous gonadotrophins throughout the year. The potential of laparoscopic artificial insemination (AI) also was assessed for producing offspring. During the non-breeding, pre-breeding, breeding and post-breeding seasons, females (n = 20) were treated with a standardized, dual-hormone regimen given intramuscularly (600 I.U. of equine chorionic gonadotrophin followed 80–84 h later with 300 I.U. of human chorionic gonadotrophin (hCG)). Laparoscopy was performed 45–50 h after administration of hCG, and all ovarian structures were described. Females with fresh corpora lutea (CL) were inseminated, and anovulatory females were subjected to follicular aspiration to examine oocyte quality. Snow leopards responded to exogenous gonadotrophins throughout the year. Mean number of total ovarian structures (distinct follicles mature in appearance plus CL) did not differ (P ≥ 0 · 05) with season, but the proportion of CL : total ovarian structures was greater (P < 0 · 01) for the breeding season compared with all other seasons. The proportion of females ovulating was greater (P<0 · 05) during the breeding and post-breeding seasons than during the pre-breeding and non-breeding seasons respectively. No Grade-1 quality oocytes were recovered from follicles of anovulatory females. Serum concentrations of oestradiol-17b appeared elevated in all females, and neither oestradiol-17β concentrations nor progesterone concentrations differed (P ≥ 0 · 05) among seasons. Of 15 females artificially inseminated, the only one that was inseminated in the non-breeding season became pregnant and delivered a single cub. This is the first successful pregnancy resulting from AI in this endangered species.

10 Pregnancy rates following artificial insemination or embryo transfer in lactating Holstein cows

2020 ◽  
Vol 32 (2) ◽  
pp. 130
Author(s):  
M. Oliveira ◽  
R. Santos ◽  
R. Chebel ◽  
D. Demetrio
Keyword(s):  
Embryo Transfer ◽  
Embryo Development ◽  
Artificial Insemination ◽  
Early Embryo ◽  
Pregnancy Rates ◽  
Holstein Cows ◽  
Genetic Merit ◽  
Excessive Heat ◽  
The Difference ◽  
June July

Excessive heat affects the fertility of high production lactating cows, and reduced pregnancy rates (PR) are observed during summer and early fall. Embryo production programs are used to produce more calves from high genetic merit animals, but could it also increase fertility by bypassing all the negative variables affecting the embryo development before Day 7 (oocyte development, ovulation, fertilization, early embryo development)? The data from AIs and embryo transfers (ET) between June 2017 and May 2019 were analysed. June, July, August, September, and October were called critical months (first-service AI conception rate dropped below 44%). The cows were located at Maddox Dairy in Riverdale, CA, USA, a Holstein herd that milks 3500 cows with a 305-day mature-equivalent milk production of 12 800 kg. First- and second-lactation cows were enrolled in a Presynch-Ovsynch oestrus-synchronization program and scheduled for the first AI at 86 days after calving or to receive an embryo 7 or 8 days after the expected heat. The embryos were produced invivo or invitro from Holstein donors and were transferred fresh or frozen. Blood was sampled on Day 30 after expected heat day (23 days after embryo transfer), and pregnancy was detected by the IDEXX PAG Bovine Pregnancy Test. Table 1 summarises the results, where ET PR% is the number of pregnant cows divided by the number of cows that received and embryo. All the cows synchronized for AI were bred, but only cows with the presence of a corpus luteum (CL) on ET day received an embryo. The presence of a CL was not detected in 28.7% (471/1642) of the cows (32.2% in the critical months and 25.7% in the others). Unfortunately, we could not detect the presence of a CL by ultrasonography every time we transferred embryos, so the nonovulation rate might be overestimated. The cows without a CL were considered open and used to calculate the adjusted PR (AdjPR%). Embryo transfer PR is superior to that of AI, especially during the critical months. Fresh invivo embryos have the most impact. When the cows without CLs are considered open, the difference between AI and ET is still evident for fresh invivo embryos. Besides producing animals with higher genetic merit, depending on the type of embryo used, ET can increase fertility in lactating Holstein cows, especially during the critical months. The other benefit of using ET is that cows that do not ovulate are synchronized right away, which is not the case for AI cows. Table 1.AI×embryo transfer in lactating Holstein cows1 from June 2017 to May 20192 Item Critical months (June to October) Other months (November to May) All year %PR n Adj PR% n %PR n Adj PR% n %PR n Adj PR% n Artificial insemination 41.2% 896 41.2% 896 47.7% 1767 47.7% 1767 45.5% 2663 2663 Fresh invivo embryo 62.7% 373 47.5% 493 69.5% 262 55.3% 329 65.5% 635 50.6% 822 Frozen invivo embryo 59.3% 221 44.8% 292 59.4% 256 47.3% 322 59.3% 477 46.1% 614 IVF fresh embryo 47.9% 167 36.2% 221 54.0% 363 43.0% 456 52.1% 530 40.8% 677 Total embryos 58.5% 761 44.2% 1006 60.2% 881 47.9% 1107 59.4% 1642 46.1% 2113 1Lactating Holstein cows, first and second lactation, first service, Presynch-Ovsynch, 85 DIM. 2PR%=the number of pregnant cows divided by the number of cows that received and embryo; AdjPR%=adjusted pregnancy rate.

scholarly journals The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

2020 ◽  
Vol 98 (11) ◽  
Author(s):  
Peter J Hansen
Keyword(s):  
Embryo Transfer ◽  
Artificial Insemination ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Bovine Embryos ◽  
Uterine Receptivity ◽  
Stage Of Development ◽  
Stage Embryo ◽  
Repeat Breeder ◽  
In Pregnancy

Abstract Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

122. PRODUCTION OF EMBRYOS IN SUPEROVULATED EWES USING FROZEN - THAWED, SEX-SORTED AND REFROZEN - THAWED SPERM

2010 ◽  
Vol 22 (9) ◽  
pp. 40
Author(s):  
K. H. Beilby ◽  
Y. B. Kaurivi ◽  
W. M. C. Maxwell ◽  
G. Evans ◽  
S. P. De Graaf ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Artificial Insemination ◽  
Blastocyst Stage ◽  
Corpora Lutea ◽  
Treatment Control ◽  
Embryo Production ◽  
Recovery Rates ◽  
Embryo Recovery ◽  
Flow Cytometric

Flow cytometric sex-sorting of sperm that has previously been cryopreserved allows sex-sorting technology to be applied more widely. While offspring have been produced following artificial insemination of synchronised ewes with frozen-thawed, sex-sorted and refrozen-thawed (FSF) sperm (1), the fertility of FSF-sperm in superovulated ewes has not been reported. The aim of this study was to determine the effect of cryopreservation prior to sperm sex-sorting and freezing on embryo production in superovulated ewes. Several ejaculates from 2 rams were either frozen-thawed, then sex-sorted and re-frozen (FSF X- and Y-chromosome enriched sperm), or immediately sex-sorted before freezing (SF X- and Y-chromosome enriched sperm). A portion of each ejaculate was also cryopreserved without sex-sorting (control). Thirty-one ewes were superovulated and inseminated (15 ×106 sperm per insemination dose) with either SF X, SF Y, FSF X, FSF Y or control sperm as previously described (2). Embryos were recovered 6 d after insemination and assessed. The superovulatory response (mean number of corpora lutea per ewe: 11.8 ± 1.3) and the embryo recovery rates (72.0 ± 5.9%) did not differ significantly among the groups. The fertilisation rates tended to differ (P=0.068) as a result of sperm treatment (control: 33%; SF: 54%; FSF: 18%) and were unaffected by sperm sex (X: 33%; Y: 37%). Of the embryos that were recovered, those derived from FSF-sperm were predominantly at the blastocyst stage (65%), whereas those derived from SF-sperm were evenly distributed among the blastocyst (30%), morula (38%) and arrested (32%) stages, suggesting that fertilisation lifespan of SF-sperm was greater than that of FSF-sperm. A greater proportion of embryos derived from Y-sperm were at the blastocyst stage compared with embryos derived from X-sperm (53% vs. 26%; P < 0.05). This study is the first to demonstrate that FSF-sperm is capable of fertilising oocytes of superovulated ewes. (1) de Graaf et al (2007) Theriogenology 67: 391–8.(2) de Graaf et al (2007) Theriogenology 67: 550–5.

scholarly journals Oocyte developmental competence in a bovine model of reproductive aging

Reproduction ◽  
2007 ◽  
Vol 134 (2) ◽  
pp. 233-239 ◽  
Author(s):  
Pritpal S Malhi ◽  
Gregg P Adams ◽  
Reuben J Mapletoft ◽  
Jaswant Singh
Keyword(s):  
Embryo Transfer ◽  
Age Groups ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Developmental Competence ◽  
Corpora Lutea ◽  
Reproductive Aging ◽  
Embryo Production ◽  
Embryo Survival ◽  
Oocyte Developmental Competence

The study was designed to test the hypothesis that aging in cattle is associated with reduced developmental competence of oocytes. The hypothesis was tested by comparing embryo production and pregnancy rates between 13- to 16-year-old cows (n = 6 in Year 1 and n = 9 in Year 2) and their 3- to 6-year-old young daughters (n = 8 in Year 1 and n = 9 in Year 2) after superovulation and transfer of embryos into an unrelated group of young recipients. Embryos were transferred into 2- to 5-year-old recipient cows (n = 99) as singletons (n = 45) or in pairs (n = 54 pairs). Embryo survival in recipients was determined by ultrasonography and by the number of calves born. Between old versus young cows, the number of ovulations (31 ± 4 vs 38 ± 3; P = 0.2) and the number of corpora lutea (25 ± 3 vs 29 ± 2; P = 0.3) did not differ, but fewer (P = 0.04) embryos were recovered from old cows (6 ± 2) than their daughters (12 ± 2). A higher proportion (P < 0.0001) of unfertilized oocytes/uncleaved zygotes were recovered from old cows (222/312, 71%) than their daughters (119/316, 38%). Among the embryos recovered, the proportion of International Embryo Transfer Society Grades 1–2 embryos was similar (P = 0.9) between old (59/90, 66%) and young cows (130/194, 67%). The survival of embryos after transfer into recipients, and the proportion of calves born were also similar between old and young cows. In conclusion, recovery of fewer embryos and a greater proportion of unfertilized oocytes/uncleaved zygotes suggest reduced developmental competence of oocytes from old cows, but there was no difference between age groups in embryo survival after the morula/blastocyst stage.

161 SUCCESSFUL INTERSPECIFIC PREGNANCY AFTER TRANSFER OF IN VITRO-PRODUCED SIKA DEER (CERVUS NIPPON NIPPON) EMBRYO IN RED DEER (CERVUS ELAPHUS HIPPELAPHUS) SURROGATE HIND

2008 ◽  
Vol 20 (1) ◽  
pp. 160 ◽  
Author(s):  
Y. Locatelli ◽  
J.-C. Vallet ◽  
G. Baril ◽  
J.-L. Touzé ◽  
A. Hendricks ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Breeding Season ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Sika Deer ◽  
Cervus Nippon ◽  
Blastocyst Stage ◽  
Deer Species ◽  
Interspecific Pregnancy

The aim of the present study was to assess the in vivo competence of in vitro-produced sika deer (Cervus nippon nippon) embryos after freezing–thawing and transfer into red deer (Cervus elaphus hippelaphus) recipients. During the breeding season, 11 adult sika deer hinds were synchronized as oocyte donors with an intravaginal sponge (45 mg of fluorogestone acetate, FGA) inserted for 12 days and removed immediately after laparoscopic ovum pick-up (LOPU), and renewed after 3 days. Ovarian stimulation was induced with an i.m. injection of 75 µg of cloprostenol (Estrumate) given on Day 8, followed by 3 i.m. injections of 0.1, 0.1, and 0.05 IU of ovine FSH (Ovagen) on Days 10 and 11 at 12-h intervals. On Day 12, hinds were anesthetized and oocytes were collected by LOPU from follicles >2 mm using an 18 G needle under moderate vacuum. COC were recovered and morphologically evaluated for quality (graded from 1 to 5). COC were then submitted to in vitro maturation, fertilization, and culture (IVM, IVF, and IVC) as described previously (Locatelli Y et al. 2005 Theriogenology 64, 1729–1739). For IVC, embryos were co-cultured with a monolayer of ovine oviduct epithelial cells in synthetic oviduct fluid medium supplemented with 10% FCS. On Day 8 post-insemination, all sika deer embryos at the blastocyst stage were cryopreserved via a standard bovine slow-freezing protocol. Of 44 LOPU sessions performed during the 1-month study, an average of 7.5 � 0.38 follicles were aspirated (mean � SEM), allowing the recovery of 3.65 � 0.38 COC per hind and per session, of which 80.0% were suitable for IVM (grades 1 and 2). Of 142 oocytes recovered, 57 cleaved after IVF (40.1%), and 14 embryos (24.6% of cleaved) reached the blastocyst stage after 8 days. At the end of the breeding season, 7 adult red deer hinds were synchronized as embryo recipients by inserting 2 intravaginal sponges per female (90 mg of FGA), for 13 days. Injections (i.m.) of 400 IU of eCG and 125 µg of cloprostenol (Estrumate) were administered 72 h before sponge removal. At Day 8 after sponge removal, straws containing frozen embryos were thawed and cryoprotectant was removed as described previously (see Locatelli Y et al. 2005 Theriogenology 64, 1729–1739). Two sika deer embryos were surgically transferred into uterine horn (unilaterally) of each red deer recipient. One of 7 red deer recipients was diagnosed pregnant by ultrasonography on Day 56. A healthy male sika deer fawn was born unassisted after 224 days of gestation. No complications were observed in initial recognition of the sika deer fawn by the red deer surrogate mother, nor in subsequent interactions. To our knowledge, this is the first report of an interspecific pregnancy obtained after in vitro embryo production and embryo transfer in deer species. In conclusion, interspecific embryo transfer after IVP may represent a useful tool for the preservation and amplification of captive residual populations of endangered deer species. Further studies are required to increase the rate of cleavage after LOPU-IVF as well as viability of frozen–thawed IVP embryos.

scholarly journals Overfeeding Extends the Period of Annual Cyclicity but Increases the Risk of Early Embryonic Death in Shetland Pony Mares

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 361
Author(s):  
Nicky M. M. D’Fonseca ◽  
Charlotte M. E. Gibson ◽  
Iris Hummel ◽  
David A. van Doorn ◽  
Ellen Roelfsema ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Reproductive Activity ◽  
High Energy ◽  
Morphometric Parameters ◽  
Net Energy ◽  
Conceptus Development ◽  
And Control ◽  
Annual Duration ◽  
Embryonic Death

Obesity has been associated with altered reproductive activity in mares, and may negatively affect fertility. To examine the influence of long-term high-energy (HE) feeding on fertility, Shetland pony mares were fed a diet containing 200% of net energy (NE) requirements during a three-year study. The incidence of hemorrhagic anovulatory follicles (HAF) and annual duration of cyclicity were compared to those in control mares receiving a maintenance diet. Day-7 embryos were flushed and transferred between donor and recipient mares from both groups; the resulting conceptuses were collected 21 days after transfer to assess conceptus development. HE mares became obese, and embryos recovered from HE mares were more likely to succumb to early embryonic death. The period of annual cyclicity was extended in HE compared to control mares in all years. The incidence of HAFs did not consistently differ between HE and control mares. No differences in embryo morphometric parameters were apparent. In conclusion, consuming a HE diet extended the duration of cyclicity, and appeared to increase the likelihood of embryos undergoing early embryonic death following embryo transfer.

A note on attainment of puberty of september-born early-maturing ewe lambs in relation to level of nutrition

1991 ◽  
Vol 53 (3) ◽  
pp. 407-409 ◽  
Author(s):  
F. Forcada ◽  
J. A. Abecia ◽  
L. Zarazaga
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Plasma Progesterone ◽  
Ewe Lambs ◽  
Early Maturing ◽  
Age At Puberty

The attainment of puberty in September-born early-maturing ewe lambs was studied at Zaragoza (latitude 41° 40' N). Thirty twin Salz females were allocated to two groups receiving two nutrition levels after 3 months of age: high (500 g/day lucerne hay and 500 g/day concentrate) (H) and low (500 g/ day lucerne hay) (L). Oestrus was detected daily by aproned rams. Corpora lutea were counted after oestrus and plasma progesterone levels monitored each week.In the first breeding season (January to February) the percentage of females showing sexual activity (silent emulation or oestrus and ovulation) was higher in the H compared with the L group (67 and 20%; P < 0/05). Nonpubertal oestrus before the main breeding season was detected in 67% of animals. In the main breeding season and for H and L groups respectively, percentage of females showing silent ovulation before puberty was 67 and 33% and mean age at puberty extended to 319 (s.e. 4-8) and 314 (s.e. 3·7) days. Ovulation rate at puberty was 1·73 (s.e. 0·13) and 1·33 (s.e. 0·15) respectively (P < 0·05).

scholarly journals Comparing the cumulative live birth rate of cleavage-stage versus blastocyst-stage embryo transfers between IVF cycles: a study protocol for a multicentre randomised controlled superiority trial (the ToF trial)

BMJ Open ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. e042395
Author(s):  
Simone Cornelisse ◽  
Liliana Ramos ◽  
Brigitte Arends ◽  
Janneke J Brink-van der Vlugt ◽  
Jan Peter de Bruin ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Live Birth ◽  
Birth Rate ◽  
Live Birth Rate ◽  
Oocyte Retrieval ◽  
Blastocyst Stage ◽  
Cleavage Stage ◽  
Cumulative Live Birth Rate ◽  
Cumulative Live Birth ◽  
Superiority Trial

IntroductionIn vitro fertilisation (IVF) has evolved as an intervention of choice to help couples with infertility to conceive. In the last decade, a strategy change in the day of embryo transfer has been developed. Many IVF centres choose nowadays to transfer at later stages of embryo development, for example, transferring embryos at blastocyst stage instead of cleavage stage. However, it still is not known which embryo transfer policy in IVF is more efficient in terms of cumulative live birth rate (cLBR), following a fresh and the subsequent frozen–thawed transfers after one oocyte retrieval. Furthermore, studies reporting on obstetric and neonatal outcomes from both transfer policies are limited.Methods and analysisWe have set up a multicentre randomised superiority trial in the Netherlands, named the Three or Fivetrial. We plan to include 1200 women with an indication for IVF with at least four embryos available on day 2 after the oocyte retrieval. Women are randomly allocated to either (1) control group: embryo transfer on day 3 and cryopreservation of supernumerary good-quality embryos on day 3 or 4, or (2) intervention group: embryo transfer on day 5 and cryopreservation of supernumerary good-quality embryos on day 5 or 6. The primary outcome is the cLBR per oocyte retrieval. Secondary outcomes include LBR following fresh transfer, multiple pregnancy rate and time until pregnancy leading a live birth. We will also assess the obstetric and neonatal outcomes, costs and patients’ treatment burden.Ethics and disseminationThe study protocol has been approved by the Central Committee on Research involving Human Subjects in the Netherlands in June 2018 (CCMO NL 64060.000.18). The results of this trial will be submitted for publication in international peer-reviewed and in open access journals.Trial registration numberNetherlands Trial Register (NL 6857).

Fertility in Cheviot ewes. 2. The effect of level of pre-mating nutrition on ovulation rate and early embryo mortality in North and South Country Cheviot ewes in moderately-good condition at mating

1979 ◽  
Vol 29 (1) ◽  
pp. 17-23 ◽  
Author(s):  
R. G. Gunn ◽  
J. M. Doney ◽  
W. F. Smith
Keyword(s):  
Food Intake ◽  
Good Condition ◽  
Early Embryo ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Restricted Feeding ◽  
Embryo Mortality ◽  
The North ◽  
Breed Difference ◽  
High Level

ABSTRACTIn two experiments over 2 years, 57 North Country Cheviot and 82 South Country Cheviot hill ewes were differentially group-fed indoors over a 2-month period to achieve either good or moderate body con- dition. Over 5 weeks prior to mating, ewes in good condition were brought down in condition by restricted feeding and ewes in mod- erate condition were raised in condition by a high level of feeding. The ewes were thus in moderately-good condition at mating. After mating, ewes were maintained in this condition until killed either on return to service or at 29 ± 8 days for counts of corpora lutea and viable embryos.Ovulation rate in each breed was positively related to the level of pre-mating food intake at the condition level studied. Embryo mortality, as ova loss, was not influenced overall by the level of pre-mating food intake but loss of multiple-shed ova was greater than that of single-shed ova in ewes which had been on restricted feeding before mating. Although a greater proportion of ewes in the North Country Cheviot breed were not pregnant at slaughter, this could not be identified as a breed difference since the breeds were studied in different years.

Sign in / Sign up

Export Citation Format

Share Document