Selection for high and low prolificacy in Cambridge sheep

1997 ◽  
Vol 65 (2) ◽  
pp. 209-215
Author(s):  
I. Ap Dewi ◽  
J. B. Owen ◽  
R. F. E. Axford ◽  
M. T. Beigi-Nassiri
Keyword(s):  
Litter Size ◽  
Small Groups ◽  
Selection Pressure ◽  
Major Gene ◽  
Selection Criterion ◽  
Selection Method ◽  
Sheep Flock ◽  
High Group ◽  
Selection For ◽  
The Difference

AbstractPrevious reports have suggested the presence of a major gene influencing prolificacy in the Cambridge sheep breed. To estimate the effect of such a gene, high and low prolificacy groups were established in a Cambridge sheep flock between lambing years 1990 and 1993. In 1990-1991 ovulation rate (OR) was used as the basis for allocating ewes into groups but for 1992-1993 litter size was used also as a secondary selection criterion. In 1990 and 1991 small groups (each with one ram) of extreme phenotype were formed. In 1992 and 1993, six high and six low groups were formed using all available ewes, increasing the number of observations but with less selection pressure for high and low prolificacy. Results from the groups were interpreted on the basis of a major gene with additive effect resulting in three distinct genotypes (CC, Cc and cc). It was assumed, because of the selection method adopted, that CC ewes were exclusively in the high groups, heterozygotes (Cc) were distributed between the high and low groups and that cc ewes were exclusively in the low groups. In 1990-1991 there was a difference in OR of 4·0 between ewes allocated to the high and low groups. In 1992-1993 the difference was 1·9. Litter size differences between groups averaged 0·73. Whilst the high group progeny had higher OR, the differences between groups were less than differences observed between groups based on selected dam records, possibly a reflexion of the young age at which progeny records were collected. Differences between the high and low groups suggest a gene effect for adult ewes of approximately 2·0, with expected OR, above a basal level of 2·0, of 4·0 and 6·0 for heterozygous and homozygous carriers respectively. The effect of the gene in young ewes (predominantly 1 to 2 years) was approximately 0·8.

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 Presence of causative mutations affecting prolificacy in the Noire du Velay and Mouton Vendéen sheep breeds

2018 ◽  
Author(s):  
L. Chantepie ◽  
L. Bodin ◽  
J. Sarry ◽  
F. Woloszyn ◽  
J. Ruesche ◽  
...  
Keyword(s):  
Litter Size ◽  
High Frequency ◽  
Major Gene ◽  
High Variability ◽  
Sheep Breeds ◽  
Allele Effect ◽  
Selection For ◽  
Meat Sheep ◽  
Very High ◽  
Specific Management

AbstractFor many decades, prolificacy has been selected in meat sheep breeds as a polygenic trait but with limited genetic gain. However, the discovery of major genes affecting prolificacy has changed the way of selection for some ovine breeds implementing gene-assisted selection as in the French Lacaune and Grivette meat breeds, or in the Spanish Rasa Aragonesa breed. Based on statistical analysis of litter size parameters from 34 French meat sheep populations, we suspected the segregation of a mutation in a major gene affecting prolificacy in the Noire du Velay and in the Mouton Vendéen breeds exhibiting a very high variability of the litter size. After the genotyping of mutations known to be present in French sheep breeds, we discovered the segregation of the FecLL mutation at the B4GALNT2 locus and the FecXGr mutation at the BMP15 locus in Noire du Velay and Mouton Vendéen, respectively. The frequency of ewes carrying FecLL in the Noire du Velay population was estimated at 21.2% and the Mouton Vendéen ewes carrying FecXGr at 10.3%. The estimated mutated allele effect of FecLL and FecXGron litter size at +0.4 and +0.3 lamb per lambing in Noire du Velay and Mouton Vendéen, respectively. Due to the fairly high frequency and the rather strong effect of the FecLL and FecXGr prolific alleles, specific management programmes including genotyping should be implemented for a breeding objective of prolificacy adapted to each of these breeds.

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.

Selection for carcass lean content in a terminal sire breed of sheep

1992 ◽  
Vol 54 (3) ◽  
pp. 367-377 ◽  
Author(s):  
N. D. Cameron ◽  
J. Bracken
Keyword(s):  
Selection Index ◽  
Selection Criterion ◽  
Live Weight ◽  
Residual Maximum Likelihood ◽  
Cumulative Response ◽  
Cumulative Selection ◽  
Selection For ◽  
The Difference ◽  
Terminal Sire ◽  
Sire Breed

AbstractA divergent selection experiment for carcass leanness in Texel-Oxford sheep was established to examine the differences between genetically lean and fat animals derived from the same base population. The selection criterion was designed to change body composition without a corresponding change in live weight, using an index of ultrasonic backfat depth and live weight at 20 weeks of age. The index was constructed using estimates of genetic and phenotypic parameters, which were available at the start of the experiment in 1985. The difference between the high and low lines, after 3 years of selection, for the selection index, live weight at 20 weeks of age, ultrasonic backfat and muscle depths was 0·59,1·30 kg, -0·76 mm and 0·88 mm respectively. The estimated difference for carcass lean and fat weight was 0·72 kg and -0·04 kg respectively with 13·5 g/kg and -13·8 g/kg for carcass lean and fat proportion. The realized heritability for the selection index, estimated from the regression of cumulative response on cumulative selection differential was 0·42, with a standard error of 0·25, after taking account of genetic drift. The selection index heritability, estimated with residual maximum likelihood (REML) methodology, was 0·46 (s.e. 0·14). REML heritability estimates for live weight at 20 weeks of age, ultrasonic backfat and muscle depths were 0·20 (s.e. 0·13), 0·35 (s.e. 0·14) and 0·43 (s.e. 0·14) respectively.

Correlated response to selection for litter size in pigs: II. Carcass, meat, and fat quality traits

2002 ◽  
Vol 80 (10) ◽  
pp. 2566 ◽  
Author(s):  
J. Estany ◽  
D. Villalba ◽  
M. Tor ◽  
D. Cubiló ◽  
J. L. Noguera
Keyword(s):  
Litter Size ◽  
Correlated Response ◽  
Quality Traits ◽  
Response To Selection ◽  
Fat Quality ◽  
Selection For

scholarly journals Polymorphism Detection of GDF9 Gene and Its Association with Litter Size in Luzhong Mutton Sheep (Ovis aries)

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 571
Author(s):  
Fengyan Wang ◽  
Mingxing Chu ◽  
Linxiang Pan ◽  
Xiangyu Wang ◽  
Xiaoyun He ◽  
...  
Keyword(s):  
Litter Size ◽  
Tertiary Structure ◽  
Novel Mutation ◽  
Major Gene ◽  
Ovis Aries ◽  
Nucleotide Polymorphisms ◽  
Economic Traits ◽  
Coding Region ◽  
Association Analyses ◽  
Gdf9 Gene

Litter size is one of the most important economic traits in sheep. GDF9 and BMPR1B are major genes affecting the litter size of sheep. In this study, the whole coding region of GDF9 was sequenced and all the SNPs (single nucleotide polymorphisms) were determined in Luzhong mutton ewes. The FecB mutation was genotyped using the Sequenom MassARRAY®SNP assay technology. Then, the association analyses between polymorphic loci of GDF9 gene, FecB, and litter size were performed using a general linear model procedure. The results showed that eight SNPs were detected in GDF9 of Luzhong mutton sheep, including one novel mutation (g.41769606 T > G). The g.41768501A > G, g.41768485 G > A in GDF9 and FecB were significantly associated with litter size in Luzhong mutton ewes. The g.41768485 G > A is a missense mutation in the mature GDF9 protein region and is predicted to affect the tertiary structure of the protein. The results preliminarily demonstrated that GDF9 was a major gene affecting the fecundity of Luzhong mutton sheep and the two loci g.41768501A > G and g.41768485 G > A may be potential genetic markers for improving litter size.

The effect of exposure to conspecifics on restlessness in the parasitoid wasp Nasonia vitripennis (Hymenoptera: Pteromalidae)

2007 ◽  
Vol 139 (5) ◽  
pp. 678-684 ◽  
Author(s):  
B.H. King
Keyword(s):  
Habitat Quality ◽  
Parasitoid Wasp ◽  
Poor Quality ◽  
The Other ◽  
Dispersal Ability ◽  
Nasonia Vitripennis ◽  
Adult Females ◽  
Selection For ◽  
The Difference ◽  
Abundance And Distribution

AbstractWhen habitat quality is variable, there should be strong selection for the ability to detect and respond to the variation. Adult females of the parasitoid wasp Nasonia vitripennis (Walker) are known to increase their restlessness (the proportion of time in locomotion) both during and after exposure to a poor quality host. Doing so provides a mechanism for leaving a poor host and potentially finding a better host. This study examined whether restlessness also changes in response to competition as indicated by the presence of adult conspecifics. Both restlessness and the probability of dispersing across an inhospitable environment were greater when a female was with another female than when she was alone. However, restlessness did not remain elevated after the other female was removed. In contrast with females, restlessness of males did not increase either during or after exposure to other males, and the probability of dispersing across an inhospitable environment was unaffected by the presence of another male. The difference between females and males may be related to differences in dispersal ability and in the abundance and distribution of hosts versus mates.

scholarly journals Selection for Reinforcement-Free Learning Ability as an Organizing Factor in the Evolution of Cognition

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Solvi Arnold ◽  
Reiji Suzuki ◽  
Takaya Arita
Keyword(s):  
Selection Pressure ◽  
Learning Ability ◽  
Environmental Complexity ◽  
Baldwin Effect ◽  
Neural Structure ◽  
Neural Organization ◽  
Environmental Structure ◽  
Selection For ◽  
Efficient Learning ◽  
Complexity Thesis

This research explores the relation between environmental structure and neurocognitive structure. We hypothesize that selection pressure on abilities for efficient learning (especially in settings with limited or no reward information) translates into selection pressure on correspondence relations between neurocognitive and environmental structure, since such correspondence allows for simple changes in the environment to be handled with simple learning updates in neurocognitive structure. We present a model in which a simple form of reinforcement-free learning is evolved in neural networks using neuromodulation and analyze the effect this selection for learning ability has on the virtual species' neural organization. We find a higher degree of organization than in a control population evolved without learning ability and discuss the relation between the observed neural structure and the environmental structure. We discuss our findings in the context of the environmental complexity thesis, the Baldwin effect, and other interactions between adaptation processes.

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