Two scientific schools have been in coexistence from the beginning of genetics, one of them searc... more Two scientific schools have been in coexistence from the beginning of genetics, one of them searching for factors of inheritance and the other one applying biometrical models to study the relationships between relatives. With the development of molecular genetics, the possibilities of detecting genes having a noticeable effect in traits augmented. Some genes with large or medium effects were localized in animals, although the most common result was to detect markers linked to these genes, allowing the possibility of assisting selection programs with markers. When a large amount of simple and inexpensive markers were available, the SNPs, new possibilities were opened since they did not need the presence of genes of large or medium effect controlling a trait, because the whole genome was scanned. Using a large amount of SNPs permits having a prediction of the breeding value at birth accurate enough to be used in some cases, like dairy cattle, to halve its generation interval. In other animal breeding programs, the implementation of genomic selection is less clear and the way in which it can be useful should be carefully studied. The need for large populations for associating phenotypic data and markers, plus the need for repeating the process continuously, complicates its application in some cases. The implementation of the information provided by the SNPs in current genetic programs has led to the development of complex statistical tools, joining the efforts of the two schools, factorial and biometrical, that nowadays work closely related.
Se ha derivado una fórmula aproximada para predecir la respuesta de la selección por reducción de... more Se ha derivado una fórmula aproximada para predecir la respuesta de la selección por reducción de varianza del tamaño de camada en conejos con un modelo que postula que una parte de la varianza ambiental esta controlada genéticamente. Esta fórmula ha sido evaluada mediante simulaciones MCMC. La semejanza entre la respuesta predicha y la simulada en diez generaciones de selección es muy alta cuando la intensidad de selección es baja o moderada, pero menor cuando la intensidad de selección aumenta. También se presenta una evaluación de la potencia estadística para detectar la respuesta por reducción de varianza en tres diseños de selección utilizados para el tamaño de camada en conejo.
In this paper we discuss the use of genetic engineering in livestock production. We examine the m... more In this paper we discuss the use of genetic engineering in livestock production. We examine the main two different aspects of genetic engineering: cloning and transgenesis. After commenting what has been expected from both techniques in livestock production in the last 25 years, the practical difficulties for implementing cloning and transgenesis are examined. Apart from technical difficulties, problems derived from the detection of genetically superior animals and evaluation of the clones and the transgenic animals make these techniques less interesting than they appear to be. Most of the observed variability of the economically interesting traits is not genetic, genetic evaluation needs a large number of animals and cloning success will represent a serious loss of genetic variability and the loss of the flexibility needed for markets in constant evolution. There is a risk in transgenic animals of production of new intermediate biochemical products that may be toxic, allergenic or carcinogenic. The benefits produced by transgenic animals hitherto hardly justify this risk. The expectations that genetic engineering produced 25 years ago should be re-examined, considering the risks and the high investment required.
Abstract The correlated response to selection for growth rate was studied, using a statistical an... more Abstract The correlated response to selection for growth rate was studied, using a statistical analysis procedure described previously [see Gianola, D.; Piles, M.; Blasco, A., Proceedings of the VII International Symposium on Animal Breeding and Genetics (1999) 101-132]. This was applied to records on 3527 rabbits of a synthetic line, selected for daily gain between 4 and 9 weeks of age. Bayesian analysis, based on a non-linear hierarchical model, was used to estimate the correlated response to selection for growth rate. Although the above ...
A hierarchical model for inferring the parameters of the joint distribution of a trait measured l... more A hierarchical model for inferring the parameters of the joint distribution of a trait measured longitudinally and another assessed cross-sectionally, when selection has been applied to the cross-sectional trait, is presented. Distributions and methods for a Bayesian implementation via Markov Chain Monte Carlo procedures are discussed for the case where infor- mation about the selection criterion is available for all
The effect of selection for growth rate on carcass and meat quality was assessed by comparing sel... more The effect of selection for growth rate on carcass and meat quality was assessed by comparing selected and control populations of rabbits measured at the same stage of maturity and slaughtered at 9 and 13 wk of age. Embryos belonging to Generation 7 were frozen, thawed, and implanted in does to produce the control group. The control group was formed
A divergent selection experiment for residual variance of litter size (Ve) has been carried out i... more A divergent selection experiment for residual variance of litter size (Ve) has been carried out in rabbit. Increasing uniformity in litter size along all the reproductive life of females may be partially due to an improvement in immunological response to infectious diseases. After eight generations of selection, the H line exhibited higher percentage of lymphocytes, being the difference between lines D=4.11, with a probability P(D>0)=96%, and lower percentage of neutrophils (D=−4.19, P(D<0)=97%). The L line presented similar percentage of lymphocytes than the H line after being exposed to inactive RHD virus, and higher percentage of lymphocytes (D=9.22, P(D>0)= 98%) after being exposed to live attenuated myxoma virus. In conclusion, selection for reduced Ve seems to improve immune response to pathogens; i.e., the L line appears to be more robust to diseases and more able to withstand adverse environmental conditions.
A divergent selection experiment for residual variance of litter size (Ve) has been carried out i... more A divergent selection experiment for residual variance of litter size (Ve) has been carried out in rabbit. Increasing uniformity in litter size along all the reproductive life of females may be partially due to an improvement in immunological response to infectious diseases. After eight generations of selection, the H line exhibited higher percentage of lymphocytes, being the difference between lines D=4.11, with a probability P(D>0)=96%, and lower percentage of neutrophils (D=−4.19, P(D<0)=97%). The L line presented similar percentage of lymphocytes than the H line after being exposed to inactive RHD virus, and higher percentage of lymphocytes (D=9.22, P(D>0)= 98%) after being exposed to live attenuated myxoma virus. In conclusion, selection for reduced Ve seems to improve immune response to pathogens; i.e., the L line appears to be more robust to diseases and more able to withstand adverse environmental conditions.
The objective of this work was to evalu- ate the Nelore beef cattle, growth curve parameters usin... more The objective of this work was to evalu- ate the Nelore beef cattle, growth curve parameters using the Von Bertalanffy function in a nested Bayesian procedure that allowed estimation of the joint posterior distribution of growth curve parameters, their (co)vari- ance components, and the environmental and additive genetic components affecting them. A hierarchical model was applied; each individual had a
A 10-generation divergent selection ex- periment for uterine capacity (UC) measured as litter siz... more A 10-generation divergent selection ex- periment for uterine capacity (UC) measured as litter size in unilaterally ovariectomized females was carried out in rabbits. A total of 2,996 observations on uterine capacity of does (up to four parities) was recorded. La- paroscopy was performed at d 12 of their second gesta- tion, and ovulation rate (OR) and number of implanted embryos
Atotal of 598 F2 does,from a cross between,the High and Low lines selected divergently for uterin... more Atotal of 598 F2 does,from a cross between,the High and Low lines selected divergently for uterine capacity during 10 generations was ,used in a ,candidate gene analysis. The presence of major genes affecting number,of implanted embryos,and uterine capacity has been suggested ,in lines ,divergently selected for uterine capacity. Uterine capacity is a main,component ,of litter size. The progesterone ,receptor
Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C ... more Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C and R) in order to optimize the experimental design for estimating the genetic parameters of the growth rate (GR) and feed conversion ratio (FCR). Twelve males and 19 females from line C, and 13 males and 23 females from line R, were selected from an ellipse defined by a quadratic index based on these traits. Data from 160 rabbits of each of the parental generations of lines C and R and their offspring (275 and 266 animals, respectively) were used for the analysis. A Bayesian framework was adopted for inference. Marginal posterior distributions of the genetic parameters were obtained by Gibbs sampling. An animal model including batch, parity order, litter size, and common environmental litter effects was assumed. Posterior means (posterior standard deviations) for heritabilities of GR and FCR were estimated to be 0.31 (0.10) and 0.31 (0.10), respectively, in line C and 0.21 (0.08) and 0....
The presence of a major gene for uterine capacity (UC), ovulation rate (OR), number of implanted ... more The presence of a major gene for uterine capacity (UC), ovulation rate (OR), number of implanted embryos (IE), embryo survival (ES), fetal survival (FS), and prenatal survival (PS) was investigated in a population of rabbits divergently selected for UC for 10 generations. Selection was performed on estimated breeding values for UC up to four parities. UC was estimated as litter size in the remaining overcrowded horn of unilaterally ovariectomized does. OR and IE were counted by means of laparoscopy. Bartlett's test, Fain's test, and a complex segregation analysis using Bayesian methods were used to test for the presence of a major gene. All three tests showed that the data appeared consistent with the presence of a major gene affecting UC and IE. The results of the complex segregation analysis suggested the presence of a major gene with large effect on IE and ES (a > 1sigma(p)), at high frequency (p = 0.70 and 0.68, respectively), and with a large contribution to the tota...
The objectives of this research were to evaluate gender differences and selection on body weight ... more The objectives of this research were to evaluate gender differences and selection on body weight as they affect growth curves of chickens. Marginal posterior densities of growth curve parameters were studied by Gibbs sampling on 10,671 male and female chickens originating from five lines. Line X-+ was selected on low body weight at 8 wk (BW8) and high body weight at 36 wk (BW36), line X+- on high BW8 and low BW36, X++ on high BW8 and BW36, X-- on low BW8, and BW36, and X00 was an unselected control line. Growth was modeled by a Gompertz function. Heritabilities and genetic correlations among parameters of the Gompertz curve were estimated. Marginal posterior densities were drawn for parameters of the growth curve and for sexual dimorphism at ages ranging from hatching to 1 yr. Lines selected for a higher BW8 had higher initial specific growth rates (L), higher maturation rates (K), and lower ages at inflection (T(I)). Lines selected for a higher BW36 had higher asymptotic body weigh...
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 29, 2005
The relationships between quantitative and reproductive fitness traits in animals are of general ... more The relationships between quantitative and reproductive fitness traits in animals are of general biological importance for the development of population genetic models and our understanding of evolution, and of great direct economical importance in the breeding of farm animals. Two well investigated quantitative traits--body weight (BW) and litter size (LS)--were chosen as the focus of our review. The genetic relationships between them are reviewed in fishes and several mammalian species. We have focused especially on mice where data are most abundant. In mice, many individual genes influencing these traits have been identified, and numerous quantitative trait loci (QTL) located. The extensive data on both unselected and selected mouse populations, with some characterized for more than 100 generations, allow a thorough investigation of the dynamics of this relationship during the process of selection. Although there is a substantial positive genetic correlation between both traits i...
Three contemporary lines were formed from the progeny of 50 French Large White sows. In the first... more Three contemporary lines were formed from the progeny of 50 French Large White sows. In the first line, gilts were selected for ovulation rate at puberty. In the second line, they were selected for prenatal survival of the first two parities, corrected for ovulation rate. The control constituted the third line. Ovulation rate at puberty was analyzed using an animal model with a batch effect. Prenatal survival was analyzed with a repeatability animal model that included batch and parity effects. Flat priors were used to represent vague previous knowledge about parity and batch effects. Additive and residual effects were represented assuming that they were a priori normally distributed. Variance components were assumed to follow either uniform or inverted chi-square distributions, a priori. The use of different priors did not affect the results substantially. Heritabilities for ovulation rate ranged from 0.32 to 0.39, and from 0.11 to 0.16 for prenatal survival, depending on the prior...
Two scientific schools have been in coexistence from the beginning of genetics, one of them searc... more Two scientific schools have been in coexistence from the beginning of genetics, one of them searching for factors of inheritance and the other one applying biometrical models to study the relationships between relatives. With the development of molecular genetics, the possibilities of detecting genes having a noticeable effect in traits augmented. Some genes with large or medium effects were localized in animals, although the most common result was to detect markers linked to these genes, allowing the possibility of assisting selection programs with markers. When a large amount of simple and inexpensive markers were available, the SNPs, new possibilities were opened since they did not need the presence of genes of large or medium effect controlling a trait, because the whole genome was scanned. Using a large amount of SNPs permits having a prediction of the breeding value at birth accurate enough to be used in some cases, like dairy cattle, to halve its generation interval. In other animal breeding programs, the implementation of genomic selection is less clear and the way in which it can be useful should be carefully studied. The need for large populations for associating phenotypic data and markers, plus the need for repeating the process continuously, complicates its application in some cases. The implementation of the information provided by the SNPs in current genetic programs has led to the development of complex statistical tools, joining the efforts of the two schools, factorial and biometrical, that nowadays work closely related.
Se ha derivado una fórmula aproximada para predecir la respuesta de la selección por reducción de... more Se ha derivado una fórmula aproximada para predecir la respuesta de la selección por reducción de varianza del tamaño de camada en conejos con un modelo que postula que una parte de la varianza ambiental esta controlada genéticamente. Esta fórmula ha sido evaluada mediante simulaciones MCMC. La semejanza entre la respuesta predicha y la simulada en diez generaciones de selección es muy alta cuando la intensidad de selección es baja o moderada, pero menor cuando la intensidad de selección aumenta. También se presenta una evaluación de la potencia estadística para detectar la respuesta por reducción de varianza en tres diseños de selección utilizados para el tamaño de camada en conejo.
In this paper we discuss the use of genetic engineering in livestock production. We examine the m... more In this paper we discuss the use of genetic engineering in livestock production. We examine the main two different aspects of genetic engineering: cloning and transgenesis. After commenting what has been expected from both techniques in livestock production in the last 25 years, the practical difficulties for implementing cloning and transgenesis are examined. Apart from technical difficulties, problems derived from the detection of genetically superior animals and evaluation of the clones and the transgenic animals make these techniques less interesting than they appear to be. Most of the observed variability of the economically interesting traits is not genetic, genetic evaluation needs a large number of animals and cloning success will represent a serious loss of genetic variability and the loss of the flexibility needed for markets in constant evolution. There is a risk in transgenic animals of production of new intermediate biochemical products that may be toxic, allergenic or carcinogenic. The benefits produced by transgenic animals hitherto hardly justify this risk. The expectations that genetic engineering produced 25 years ago should be re-examined, considering the risks and the high investment required.
Abstract The correlated response to selection for growth rate was studied, using a statistical an... more Abstract The correlated response to selection for growth rate was studied, using a statistical analysis procedure described previously [see Gianola, D.; Piles, M.; Blasco, A., Proceedings of the VII International Symposium on Animal Breeding and Genetics (1999) 101-132]. This was applied to records on 3527 rabbits of a synthetic line, selected for daily gain between 4 and 9 weeks of age. Bayesian analysis, based on a non-linear hierarchical model, was used to estimate the correlated response to selection for growth rate. Although the above ...
A hierarchical model for inferring the parameters of the joint distribution of a trait measured l... more A hierarchical model for inferring the parameters of the joint distribution of a trait measured longitudinally and another assessed cross-sectionally, when selection has been applied to the cross-sectional trait, is presented. Distributions and methods for a Bayesian implementation via Markov Chain Monte Carlo procedures are discussed for the case where infor- mation about the selection criterion is available for all
The effect of selection for growth rate on carcass and meat quality was assessed by comparing sel... more The effect of selection for growth rate on carcass and meat quality was assessed by comparing selected and control populations of rabbits measured at the same stage of maturity and slaughtered at 9 and 13 wk of age. Embryos belonging to Generation 7 were frozen, thawed, and implanted in does to produce the control group. The control group was formed
A divergent selection experiment for residual variance of litter size (Ve) has been carried out i... more A divergent selection experiment for residual variance of litter size (Ve) has been carried out in rabbit. Increasing uniformity in litter size along all the reproductive life of females may be partially due to an improvement in immunological response to infectious diseases. After eight generations of selection, the H line exhibited higher percentage of lymphocytes, being the difference between lines D=4.11, with a probability P(D>0)=96%, and lower percentage of neutrophils (D=−4.19, P(D<0)=97%). The L line presented similar percentage of lymphocytes than the H line after being exposed to inactive RHD virus, and higher percentage of lymphocytes (D=9.22, P(D>0)= 98%) after being exposed to live attenuated myxoma virus. In conclusion, selection for reduced Ve seems to improve immune response to pathogens; i.e., the L line appears to be more robust to diseases and more able to withstand adverse environmental conditions.
A divergent selection experiment for residual variance of litter size (Ve) has been carried out i... more A divergent selection experiment for residual variance of litter size (Ve) has been carried out in rabbit. Increasing uniformity in litter size along all the reproductive life of females may be partially due to an improvement in immunological response to infectious diseases. After eight generations of selection, the H line exhibited higher percentage of lymphocytes, being the difference between lines D=4.11, with a probability P(D>0)=96%, and lower percentage of neutrophils (D=−4.19, P(D<0)=97%). The L line presented similar percentage of lymphocytes than the H line after being exposed to inactive RHD virus, and higher percentage of lymphocytes (D=9.22, P(D>0)= 98%) after being exposed to live attenuated myxoma virus. In conclusion, selection for reduced Ve seems to improve immune response to pathogens; i.e., the L line appears to be more robust to diseases and more able to withstand adverse environmental conditions.
The objective of this work was to evalu- ate the Nelore beef cattle, growth curve parameters usin... more The objective of this work was to evalu- ate the Nelore beef cattle, growth curve parameters using the Von Bertalanffy function in a nested Bayesian procedure that allowed estimation of the joint posterior distribution of growth curve parameters, their (co)vari- ance components, and the environmental and additive genetic components affecting them. A hierarchical model was applied; each individual had a
A 10-generation divergent selection ex- periment for uterine capacity (UC) measured as litter siz... more A 10-generation divergent selection ex- periment for uterine capacity (UC) measured as litter size in unilaterally ovariectomized females was carried out in rabbits. A total of 2,996 observations on uterine capacity of does (up to four parities) was recorded. La- paroscopy was performed at d 12 of their second gesta- tion, and ovulation rate (OR) and number of implanted embryos
Atotal of 598 F2 does,from a cross between,the High and Low lines selected divergently for uterin... more Atotal of 598 F2 does,from a cross between,the High and Low lines selected divergently for uterine capacity during 10 generations was ,used in a ,candidate gene analysis. The presence of major genes affecting number,of implanted embryos,and uterine capacity has been suggested ,in lines ,divergently selected for uterine capacity. Uterine capacity is a main,component ,of litter size. The progesterone ,receptor
Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C ... more Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C and R) in order to optimize the experimental design for estimating the genetic parameters of the growth rate (GR) and feed conversion ratio (FCR). Twelve males and 19 females from line C, and 13 males and 23 females from line R, were selected from an ellipse defined by a quadratic index based on these traits. Data from 160 rabbits of each of the parental generations of lines C and R and their offspring (275 and 266 animals, respectively) were used for the analysis. A Bayesian framework was adopted for inference. Marginal posterior distributions of the genetic parameters were obtained by Gibbs sampling. An animal model including batch, parity order, litter size, and common environmental litter effects was assumed. Posterior means (posterior standard deviations) for heritabilities of GR and FCR were estimated to be 0.31 (0.10) and 0.31 (0.10), respectively, in line C and 0.21 (0.08) and 0....
The presence of a major gene for uterine capacity (UC), ovulation rate (OR), number of implanted ... more The presence of a major gene for uterine capacity (UC), ovulation rate (OR), number of implanted embryos (IE), embryo survival (ES), fetal survival (FS), and prenatal survival (PS) was investigated in a population of rabbits divergently selected for UC for 10 generations. Selection was performed on estimated breeding values for UC up to four parities. UC was estimated as litter size in the remaining overcrowded horn of unilaterally ovariectomized does. OR and IE were counted by means of laparoscopy. Bartlett's test, Fain's test, and a complex segregation analysis using Bayesian methods were used to test for the presence of a major gene. All three tests showed that the data appeared consistent with the presence of a major gene affecting UC and IE. The results of the complex segregation analysis suggested the presence of a major gene with large effect on IE and ES (a > 1sigma(p)), at high frequency (p = 0.70 and 0.68, respectively), and with a large contribution to the tota...
The objectives of this research were to evaluate gender differences and selection on body weight ... more The objectives of this research were to evaluate gender differences and selection on body weight as they affect growth curves of chickens. Marginal posterior densities of growth curve parameters were studied by Gibbs sampling on 10,671 male and female chickens originating from five lines. Line X-+ was selected on low body weight at 8 wk (BW8) and high body weight at 36 wk (BW36), line X+- on high BW8 and low BW36, X++ on high BW8 and BW36, X-- on low BW8, and BW36, and X00 was an unselected control line. Growth was modeled by a Gompertz function. Heritabilities and genetic correlations among parameters of the Gompertz curve were estimated. Marginal posterior densities were drawn for parameters of the growth curve and for sexual dimorphism at ages ranging from hatching to 1 yr. Lines selected for a higher BW8 had higher initial specific growth rates (L), higher maturation rates (K), and lower ages at inflection (T(I)). Lines selected for a higher BW36 had higher asymptotic body weigh...
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 29, 2005
The relationships between quantitative and reproductive fitness traits in animals are of general ... more The relationships between quantitative and reproductive fitness traits in animals are of general biological importance for the development of population genetic models and our understanding of evolution, and of great direct economical importance in the breeding of farm animals. Two well investigated quantitative traits--body weight (BW) and litter size (LS)--were chosen as the focus of our review. The genetic relationships between them are reviewed in fishes and several mammalian species. We have focused especially on mice where data are most abundant. In mice, many individual genes influencing these traits have been identified, and numerous quantitative trait loci (QTL) located. The extensive data on both unselected and selected mouse populations, with some characterized for more than 100 generations, allow a thorough investigation of the dynamics of this relationship during the process of selection. Although there is a substantial positive genetic correlation between both traits i...
Three contemporary lines were formed from the progeny of 50 French Large White sows. In the first... more Three contemporary lines were formed from the progeny of 50 French Large White sows. In the first line, gilts were selected for ovulation rate at puberty. In the second line, they were selected for prenatal survival of the first two parities, corrected for ovulation rate. The control constituted the third line. Ovulation rate at puberty was analyzed using an animal model with a batch effect. Prenatal survival was analyzed with a repeatability animal model that included batch and parity effects. Flat priors were used to represent vague previous knowledge about parity and batch effects. Additive and residual effects were represented assuming that they were a priori normally distributed. Variance components were assumed to follow either uniform or inverted chi-square distributions, a priori. The use of different priors did not affect the results substantially. Heritabilities for ovulation rate ranged from 0.32 to 0.39, and from 0.11 to 0.16 for prenatal survival, depending on the prior...
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Papers by AGUSTIN BLASCO