Divergent selection for ovulation rate in sheep : effect on embryo survival

1992 ◽  
Vol 1992 ◽  
pp. 44-44
Author(s):  
J.P. Hanrahan
Keyword(s):  
Genetic Variation ◽  
Litter Size ◽  
Mammalian Species ◽  
Divergent Selection ◽  
Ovulation Rate ◽  
Relative Importance ◽  
Embryo Survival ◽  
Breed Differences ◽  
Selection For ◽  
The Relationship

The relative importance of genetic variation in ovulation rate and in embryo survival together with the genetic relationship between these traits are important issues in terms of manipulating prolificacy in all multitocous mammalian species. Evidence in sheep, primarily from study of breed differences but also based on results of selection for litter size, shows that genetic variation in litter size is essentially attributable to differences in ovulation rate although genetic differences in embryo survival have been identified. Results from selection on litter size also suggest that genetic variation in ovulation rate is independent of any variation in embryo survival. The evaluation of the relationship between these traits in sheep is somewhat problematical in most populations due to the low level of ovulation and particularly the associated high proportion of ewes which shed a single ovum. The objective of the present study was to use lines of Finn Sheep, a breed with a high ovulation rate and in which single ovulations are rare, which have been developed by divergent selection on ovulation rate to evaluate the genetic association between ovulation rate and embryo survival.

A Model relating litter size to ovulation rate and embryo survival in pigs

1989 ◽  
Vol 1989 ◽  
pp. 93-93
Author(s):  
J.P. Hanrahan
Keyword(s):  
Genetic Variation ◽  
Genetic Association ◽  
Litter Size ◽  
Economic Importance ◽  
Ovulation Rate ◽  
The Other ◽  
Correlated Response ◽  
Embryo Survival ◽  
Population Selection ◽  
Selection For

The number of pigs weaned per sow per year has increased substantially in recent years due mainly to changes in husbandry with probably some contribution from breed substitution and crossbreeding (Haley et al 1986). Because of emerging difficulties in relation to responses to continued selection for leaness and reassessment of the economic importance of prolificacy in pigs there is considerable interest in selection for increased litter size. It is generally agreed that the heritability of litter size is about 0.1 and attempts to increase litter size by within population selection have not been particularly successful. On the other hand selection for increased ovulation rate in pigs has been effective but the correlated change in litter size has been small. This apparent failure to achieve significant correlated response in litter size has been attributed to a negative genetic association between ovulation rate and embryo survival. However, there is very little information on the magnitude of genetic variation in embryo survival or its relationship with ovulation rate.

Effect of selection for increased litter size on ovulation rate and embryo survival in sheep

1990 ◽  
Vol 1990 ◽  
pp. 32-32 ◽  
Author(s):  
J.P. Hanrahan
Keyword(s):  
Litter Size ◽  
Ovulation Rate ◽  
Control Line ◽  
Selection Experiment ◽  
Embryo Survival ◽  
Relative Contribution ◽  
Variation Data ◽  
Component Traits ◽  
Selection For ◽  
The Impact

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

scholarly journals The effect of reproductive loss on the performance of a research flock

2020 ◽  
Vol 98 (3) ◽  
Author(s):  
Paul R Shorten ◽  
Sara J Edwards ◽  
Jenny L Juengel
Keyword(s):  
Reproductive Performance ◽  
Ovulation Rate ◽  
Relative Importance ◽  
Sheep Flock ◽  
Embryo Survival ◽  
Reproductive Loss ◽  
Selection For ◽  
Lamb Survival ◽  
And Performance

Abstract The reproductive performance of a sheep flock is dependent on a multitude of complex interacting factors. Achieving optimal flock performance requires knowledge of the reproductive steps and how these are linked and related to available measurements of the state and performance of the flock. The goal was to use previously collected data from a research flock that had undergone selection for fecundity (11,369 lambing records), to model the key reproductive steps affecting flock reproductive performance. The model was used to investigate how changes in liveweight, age, ovulation rate, number of fetuses at midpregnancy, number of lambs born, and birthweight affect the number of lambs weaned and the weaning weight of each lamb in this flock. The data available from the research flock were used to parameterize models of each reproductive step and assess the role of ewe age and premating liveweight on each reproductive step. These models were then linked together as a simulation tool to assess the role of different parameters on flock reproductive performance, which was defined as the total weight of lambs weaned per ewe exposed to the ram. Flock elasticities were calculated that characterize the relative importance of the effect of average premating ewe liveweight (0.81), average ovulation rate (0.33), variance in ovulation rate (−0.095), embryo survival (0.72), lamb survival (1.03), conception failure (0.35), and average ewe age (0.056) on the total kilograms of lamb liveweight at weaning per ewe exposed to the ram. The largest elasticity for lamb survival indicated that a 1% increase in lamb survival is expected to have a 1.03% increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram in this flock. Assuming similar costs, interventions to increase lamb survival for this flock will provide the largest increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram, which is a key metric of flock performance.

Genetic implications of a simulation model of litter size in swine based on ovulation rate, potential embryonic viability and uterine capacity: II. Simulated selection.

1990 ◽  
Vol 68 (4) ◽  
pp. 980-986 ◽  
Author(s):  
G. L. Bennett ◽  
K. A. Leymaster
Keyword(s):  
Simulation Model ◽  
Litter Size ◽  
Selection Pressure ◽  
Selection Response ◽  
Ovulation Rate ◽  
Direct Selection ◽  
Weak Selection ◽  
Embryo Survival ◽  
Swine Population ◽  
Selection For

Abstract Direct selection for ovulation rate, uterine capacity, litter size and embryo survival and selection for indexes of ovulation rate with each of the remaining traits were simulated for a swine population. The relationships among these traits were determined from a simulation model that assumed that litter size was always less than or equal to both ovulation rate and uterine capacity. Heritabilities of ovulation rate and uterine capacity were assumed to be .25 and .20, respectively, and uncorrelated genetically and phenotypically. No additional genetic variation was assumed. Responses to weak selection pressure were simulated by recurrent updating of phenotypic variances and covariances combined with the heritabilities of ovulation rate and uterine capacity. Two indexes of ovulation rate and uterine capacity each resulted in 37% greater increase in litter size than direct selection for litter size. Indexes of ovulation rate and either litter size or embryo survival increased litter size by 21% more than direct selection for litter size. Selection for ovulation rate, uterine capacity or embryo survival was 6, 35 and 79%, respectively, less effective than direct selection for litter size. Responses to intense selection pressure were determined by direct simulation of genotypes and phenotypes of individuals. The two indexes of ovulation rate and uterine capacity exceeded direct selection for litter size by 39 and 27%. The indexes of ovulation rate and either litter size or embryo survival exceeded direct selection for litter size by 19 and 13%, respectively. Intense selection for ovulation rate or uterine capacity decreased selection response by 26 and 67%, respectively, relative to direct selection for litter size. Intense selection for embryo survival decreased litter size slightly.

An egg transfer study of litter size, birth weight and lamb survival

1974 ◽  
Vol 18 (3) ◽  
pp. 249-263 ◽  
Author(s):  
G. E. Bradford ◽  
C. S. Taylor ◽  
J. F. Quirke ◽  
R. Hart
Keyword(s):  
Body Weight ◽  
Birth Weight ◽  
Litter Size ◽  
Ovulation Rate ◽  
Gestation Length ◽  
Transfer Experiment ◽  
Embryo Survival ◽  
Average Litter Size ◽  
Breed Differences ◽  
Transfer Study

SUMMARYIn an egg-transfer experiment, seven breeds of sheep differing widely in mean mature ewe weight were used: Oxford Down, 96 kg; Borderm Leicester, 77; Finnish Landrace, 55; Southdown, 52; Tasmanian Merino, 42; Welsh Mountain, 34; and Soay, 22. Body weight and gestation length of recipient ewes are briefly examined. Of 60 recipient ewes, 95% became pregnant. Embryo survival averaged 69% and appeared to be independent of breed of embryo. Litter size of Welsh Mountain, Border Leicester and Finnish Landrace ewes each given four eggs averaged 2·6, 2·9 and 2·9 respectively so that most of the normally observed breed differences are mainly due to differences in ovulation rate. Observed birth weights were in general agreement with those predicted from litter size and donor and recipient ewe weights. The maternal capacity of Finnish ewes was close to average. Litter size affected survival mainly through its effect on birth weight. For Oxford lambs in litters of 3 to 5 from Finnish recipients, birth weight was 42% that of normal single-born Oxfords and only 42% survived. For Soays the corresponding values were 59% for birth weight and 85% for survival. Finnish lambs were exceptionally small at birth but had the highest viability of all breeds. Lamb mortality was higher for males (18%) than females (9%) especially in large litters (26 v. 11%) but about the same in both sexes for Finnish lambs.

scholarly journals Components of litter size in mice after 110 generations of selection

Reproduction ◽  
2004 ◽  
Vol 127 (5) ◽  
pp. 587-592 ◽  
Author(s):  
M Holt ◽  
O Vangen ◽  
W Farstad
Keyword(s):  
Litter Size ◽  
Late Pregnancy ◽  
Ovulation Rate ◽  
Control Line ◽  
Embryo Survival ◽  
High Line ◽  
Line Selection ◽  
Males And Females ◽  
The Mean ◽  
Standard Deviations

The aim of the present study was to evaluate how ovulation rate and survival rate through pregnancy had been affected by more than 110 generations of upwards selection on litter size in mice. The mean number of pups born alive was 22 in the high line (selected line) and 11 in the control line (an increase in 2.6 standard deviations). Selection on litter size increased ovulation rate by 4.6 standard deviations, and it is suggested that selection also increased embryonic mortality in late pregnancy. Embryo survival from ovulation until birth was 66% in the selected line and 69% in the control line, and the observed loss in litter size from day 16 of pregnancy until birth was possibly higher in the high line compared with the control line. Selection for higher litter size has significantly increased body weight in both males and females, as the mean weight at mating for the females was 46 g in the high line and 33 g in the control line respectively.

Genetics of reproduction in the rabbit.

2021 ◽  
pp. 212-233
Author(s):  
Miriam Piles ◽  
Maria Antonia Santacreu ◽  
Agustin Blasco ◽  
Jun Pablo Sanchez
Keyword(s):  
Litter Size ◽  
Reproductive Cycle ◽  
Genetic Determinism ◽  
Ovulation Rate ◽  
Biological Processes ◽  
Embryo Survival ◽  
Male And Female ◽  
Fetal Survival

Abstract This chapter describes the genetic determinism of all traits involved in male and female reproductive performances in rabbits. All traits related to the underlying biological processes leading to the mating outcome, as well as some of its general features, such as the homogeneity of the reproductive performances, are considered (semen and ejaculate characteristics, ovulation rate, fertility, embryo survival, fetal survival and litter size). Different parameters of fertility and litter size are discussed, including the contribution of both sexes to each phase of the reproductive cycle.

The effect of energy or protein supplementation on embryo survival rate in ewes

1995 ◽  
Vol 1995 ◽  
pp. 55-55
Author(s):  
M.G. Diskin ◽  
J.P. Hanrahan
Keyword(s):  
Survival Rate ◽  
Litter Size ◽  
Protein Supplementation ◽  
Ovulation Rate ◽  
Reproductive Efficiency ◽  
Protein Supplement ◽  
Embryo Survival ◽  
Rumen Undegradable Protein

Embryo survival rate is a major factor determining litter size and overall reproductive efficiency in sheep. In sheep, as ovulation rate increases the proportion of embryos surviving decreases. There is evidence, from cattle, that feeding a rumen-undegradable protein supplement enhances embryo survival rate. The objective of this experiment was to determine the effect on embryo survival rate in high prolific ewes of feeding an energy or protein supplement.

Relationship between litter size and perinatal and pre-weaning survival in pigs

2002 ◽  
Vol 74 (2) ◽  
pp. 217-222 ◽  
Author(s):  
M. S. Lund ◽  
M. Puonti ◽  
L. Rydhmer ◽  
J. Jensen
Keyword(s):  
Litter Size ◽  
Negative Correlation ◽  
Genetic Effects ◽  
Direct Effects ◽  
Selection For ◽  
Heritability Estimates ◽  
The Relationship ◽  
Piglet Survival

AbstractThe objective of this study was to analyse the relationship between direct and maternal genetic effects on litter size and piglet survival. The analyses were performed on records from 26 564 Landrace litters and 15 103 Yorkshire litters from first parity dams in Finnish herds. The trivariate model fitted total number of piglets born, proportion alive at birth and proportion survived from birth until 3 weeks as traits of the litter. The model included direct genetic and maternal genetic effects for all traits. In Landrace pigs, maternal heritabilities were estimated to be 0·11 for total number born, 0·06 for proportion alive at birth, and 0·08 for proportion survived from birth until 3 weeks. The corresponding estimates for the Yorkshire breed were 0·14, 0·06 and 0·01. All heritability estimates of direct effects were below 0·05. In the Landrace breed, there was a negative correlation of -0·39 between maternal genetic effects on total number born and maternal genetic effects on proportion survived from birth until 3 weeks and a negative correlation of -0·41 between direct and maternal genetic effects on proportion survived from birth until 3 weeks. These correlations were not significant in the Yorkshire breed. The results show that selection for number born in total alone will lead to a deterioration in the maternal ability of sows. Selection for pre-weaning survival could be achieved by selecting on direct and maternal components jointly.

Genetic studies of prolificacy in New Zealand sheep

1998 ◽  
Vol 67 (2) ◽  
pp. 289-297 ◽  
Author(s):  
G. H. Davis ◽  
C. A. Morris ◽  
K. G. Dodds
Keyword(s):  
Litter Size ◽  
Heritability Estimate ◽  
Ovulation Rate ◽  
The Other ◽  
Relationship Matrix ◽  
Research Station ◽  
Embryo Survival ◽  
Genetic Studies ◽  
Average Litter Size ◽  
Likelihood Model

AbstractData on ovulation rate, embryo survival and litter size have been analysed from the 1988-96 records collected at AgResearch's Woodlands Research Station on 2180 elite (highly prolific) ewes of three breeds: Romney, Coopworth and Perendale. The Romneys included a subgroup found to carry the sex-linked Inverdale high prolificacy gene. Foundation animals for all breeds were screened on high litter size (lambs born, alive or dead, per ewe lambing) from industry flocks. Prior to being transferred to Woodlands between 1979 and 1984, their average litter size was 2·66. Ovulation rates for descendants of the foundation ewes averaged 2·15 (Romney), 2·43 (Coopworth), 2·15 (Perendale) and 2·96 for the Romney subgroup carrying the Inverdale gene. Embryo survival averaged 0·84 except for a low value in Inverdales (0·76). Using a restricted maximum likelihood model, with full relationship matrix, the within-breed heritability of ovulation rate over all ages and breeds (excluding Inverdale) was 0·14 (s.e. 0·03), with repeatability 0·26 (s.e. 0·02). Litter size averaged 1-80 (Romney), 2·05 (Coopworth), 1·76 (Perendale) and 2·17 (Inverdale). The heritability estimate for litter size (excluding Inverdale) was 0·073 (s.e. 0·018), from data for all ages. The genetic correlation between ovulation rate and litter size was 0·91 (s.e. 0·08). The standard deviation for ovulation rate in the Inverdales was 1·75 times as great as the average of the other three breeds. Embryo survival to term for ewes conceiving to two, three or four ovulations averaged 0·89, 0·77 and 0·64, respectively, and was significantly different among breeds fP < 0·001). The greater ovulation rate in Inverdales than Romneys was sufficient to explain the Inverdale effect on reduced embryo survival. The highest embryo survival was observed in the Coopworth breed (P < 0·001).

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