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.

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.

Estimation of Genetic Parameters and Selection Response for Reproductive and Growth Traits in Rideau-Arcott sheep

2020 ◽  
Author(s):  
Mohammed Naser Boareki ◽  
Luiz Brito ◽  
Angela Cánovas ◽  
V.R. Osborne ◽  
Flavio S Schenkel
Keyword(s):  
Litter Size ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Reproductive Traits ◽  
Selection Response ◽  
Direct Selection ◽  
Correlated Response ◽  
Response To Selection ◽  
Weaning Weight ◽  
Selection For

The goal of this study was to estimate genetic parameters and predict direct and correlated response to selection for lamb growth traits and ewe reproductive traits, based on single trait selection or combining multiple traits in an optimum index that targets total litter post-weaning weight in the first lambing as the main selection goal. Heritability estimates ranged from 0.04 to 0.19. Genetic correlations between growth and reproductive traits ranged from -0.24 to 0.15. The indirect response to selection for reproductive traits in later lambings, by selecting on first lambing performance, was 11 to 25% greater than direct selection. The response to indirect selection for composite reproductive traits, i.e. total weaning weight or total post-weaning weight, by selecting on individual lamb weaning weight or post-weaning weight was 1 to 69% greater than direct selection, but it was accompanied by a negative response on litter size. However, combining alternate growth and reproductive traits in optimum selection index resulted in correlated response of up to 96% greater than direct selection response for reproductive traits without a negative response on litter size. Therefore, multiple trait selection using an index of component traits was more effective than direct selection for a composite trait.

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.

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

1990 ◽  
Vol 68 (4) ◽  
pp. 969-979 ◽  
Author(s):  
G. L. Bennett ◽  
K. A. Leymaster
Keyword(s):  
Simulation Model ◽  
Litter Size ◽  
Random Environment ◽  
Genetic Model ◽  
Genetic Interaction ◽  
Selection Response ◽  
Ovulation Rate ◽  
Embryo Viability ◽  
Genetic Characteristics ◽  
Independent Culling

Abstract A simulation model of litter size in swine based on ovulation rate, uterine capacity and potential embryo viability was compared to three genetic models to clarify its genetic characteristics. The simulation model is equivalent to independent culling based on fixed levels of potentially viable embryos and uterine capacity. Litter size also can be described by a combination of additive, additive × additive, mean environment × additive, random environment and additive × random environment effects. A third genetic model that can describe the simulation model is the associative effects model, in which litter size is the result of grouping two genotypes. The fixed independent culling levels model predicts that genetic parameters will change as the component means change. This genetic model also predicts that selection on an index of ovulation rate and uterine capacity would improve selection response for litter size. This genetic model predicts asymmetry of correlated responses in ovulation rate and uterine capacity when selecting for high and low litter size. The nonadditive genetic model predicts covariances among relatives that are different from their additive relationships; however, simulated results did not detect any differences. The nonadditive genetic model also predicts that heterosis for litter size will differ among crosses based on the mean environment and on additive × additive genetic interaction. The associative effects model predicts that selection for litter size will always lead to a positive response in litter size.

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.

Selection and response within the nucleus of a sheep group-breeding scheme

1990 ◽  
Vol 51 (3) ◽  
pp. 593-599 ◽  
Author(s):  
S. Anderson ◽  
M. K. Curran
Keyword(s):  
Litter Size ◽  
Age Groups ◽  
Selection Response ◽  
Sheep Flock ◽  
Breeding Scheme ◽  
Average Value ◽  
Group Breeding ◽  
Selection For ◽  
Progeny Group ◽  
Selection Differentials

ABSTRACTAn evaluation of the response to selection for prolificacy within a nucleus sheep flock of a commercial group-breeding scheme is presented. In 1979, the Romney Group Breeders formed a nucleus flock of 120 prolific ewes chosen from 12 contributing flocks. A control flock was established in 1982 from the same source. The analysis was conducted on the trait of litter size. Selection differentials are presented for each year of birth progeny group in both flocks. Expected selection response was calculated from selection differentials and was found to have an average value of 1·5% of parent mean litter size per year. Using least squares procedures the litter size performance of control and nucleus ewes of 2, 3 and 4 years of age was corrected for environmental effects. Realized response was estimated from the differences between corrected litter size means of control and nucleus flocks. Response in litter size was found to be significant within years and within ewe age groups (P < 0·05).

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.

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