Alexander Kahi - Academia.edu (original) (raw)
Papers by Alexander Kahi
Breeding Practices and Traits of Economic Importance for Indigenous Chicken in South Sudan
Journal of Animal Production, Nov 30, 2022
Indigenous Chicken Ecotypes in Kenya
Indigenous chicken (IC) comprises several ecotypes which exhibit a high between-and within-ecotyp... more Indigenous chicken (IC) comprises several ecotypes which exhibit a high between-and within-ecotype variations in performance. However, genetic and feeding interventions targeted at improving their low productivity have been applied uniformly disregarding the apparent ecotype differences and without a sound biological basis targeted at manipulating the biological process of growth. Consequently, breeding strategies and feed formulation have been unmatched with the biological process of growth of the different ecotypes. Quantitative description of the growth patterns of ecotypes upon which to design appropriate breeding and feeding interventions is limited. This book compared body weights of ecotypes and modeled the growth curves to estimate the associated parameters and their relationship using growth models (Von-Bertalanffy, Gompertz, Logistic, and Brody). The study also estimated heritabilities, genetic and phenotypic correlations. The book reveals the differences in growth curve p...
Asian-Australasian Journal of Animal Sciences, 2019
This paper presents a review of dairy goat production in sub-Saharan Africa (SSA) from 2010-2017,... more This paper presents a review of dairy goat production in sub-Saharan Africa (SSA) from 2010-2017, its current state, constraints and prospects for research and development. Since the introduction of dairy goats in SSA in pre-colonial times, their populations have continued to increase due to declining land size as a result of land fragmentation and increasing demand for goat milk. The current goat population in SSA is 372,716,040 head of which only 15.98% used for milk production. Populations in the Eastern and Western regions of SSA have shown an increasing trend from 2010 to 2017. The Southern Africa goat population is on the decline at an annual rate of about 1.77% whereas Central Africa has had a constant goat population within the same period. Eastern Africa reported the highest increase in the population of goats used for milk production. Milk production was highest in Eastern Africa and lowest in Southern Africa. However, dairy goat productivity remained constant in the Eastern region throughout the review period. Dairy goats are mainly raised under smallholder mixed crop-livestock systems. To enhance the development of the dairy goat, concerted efforts should be made to alleviate the constraints that stifle its growth. These constraints can be categorized into nutrition and feeding, breeding and reproduction, diseases, parasites, climate change, and underdeveloped dairy goat products market. Effective management of dairy goats requires a holistic approach and there is the need to expand the markets by further sensitization on the nutritional and medicinal advantages of dairy goat products. In order to achieve rapid development in the dairy goat sub sector, research and development initiatives should be directed towards alleviating the hurdles in nutrition and feeding, breeding, animal health and resilience as well as dairy goat markets.
African Journal of Biotechnology Genomic composition factors affect codon usage in porcine genome
AFRICAN JOURNAL OF BIOTECHNOLOGY
The objective of the study was to determine the codon usage bias in the porcine genome and deciph... more The objective of the study was to determine the codon usage bias in the porcine genome and decipher its determinants. To investigate the underlying mechanisms of codon bias, the coding sequence (CDS) from the swine reference sequence (ssc10.2) was extracted using Biomart. An in house built Perl script was used to derive various genomic traits and codon indices. Analysis was done using R statistical package, and correlations and multivariate regressions were performed. We report the existence of codon usage bias that might suggest existence of weak translational selection. The codon bias is feebly related to nucleotide composition (GC%, GC3, CDS length). This study can be explored for designing degenerate primers, necessitate selecting appropriate hosts expression systems to manipulate the expression of target genes in vivo or in vitro and improve the accuracy of gene prediction from genomic sequences thus maximizing the effectiveness of genetic manipulations in synthetic biology.
Direct and maternal (co)variance components and genetic parameters for growth and reproductive traits in the Boran cattle in Kenya
Tropical Animal Health and Production, 2008
Direct and maternal (co)variance components and genetic parameters were estimated for growth and ... more Direct and maternal (co)variance components and genetic parameters were estimated for growth and reproductive traits in the Kenya Boran cattle fitting univariate animal models. Data consisted of records on 4502 animals from 81 sires and 1010 dams collected between 1989 and 2004. The average number of progeny per sire was 56. Direct heritability estimates for growth traits were 0.34, 0.12, 0.19, 0.08 and 0.14 for birth weight (BW), weaning weight (WW), 12-month weight (12W), 18-month weight (18W) and 24-month weight (24W), respectively. Maternal heritability increased from 0.14 at weaning to 0.34 at 12 months of age but reduced to 0.11 at 24 months of age. The maternal permanent environmental effect contributed 16%, 4% and 10% of the total phenotypic variance for WW, 12W and 18W, respectively. Direct-maternal genetic correlations were negative ranging from -0.14 to -0.58. The heritability estimates for reproductive traits were 0.04, 0.00, 0.15, 0.00 and 0.00 for age at first calving (AFC), calving interval in the first, second, and third parity, and pooled calving interval. Selection for growth traits should be practiced with caution since this may lead to a reduction in reproduction efficiency, and direct selection for reproductive traits may be hampered by their low heritability.
This paper uses data from a survey of one hundred and eighty four dairy households in two divisio... more This paper uses data from a survey of one hundred and eighty four dairy households in two divisional administrative zones in the Kenya highlands to empirically analyze the factors that influence the choice of a milk marketing channel. Multinomial logit econometric estimation results show that distance to milk collection centre, education level, membership of the household head to farmers' group/organization, the number of cows ownedn by the household, and the coefficiency of variation in prices significantly influenced the choice of a marketing channel. Private channel players are yet to focus on tapping the production potential of farmers with small herd sizes and encouraging group formation to exploit the social capital. The study demonstrates the need for the private sector to enhance milk collection at the unexplored areas to exploit the milk supply potentials. The implications for policy are provide.
Data for: Meta-analysis of genetic parameters for traits of economic importance for beef cattle in the tropics
The data is a compilation of studies that have reported various parameters for different traits o... more The data is a compilation of studies that have reported various parameters for different traits of importance for beef breeds in the tropics
Economic evaluation of Hereford cattle breeding schemes incorporating direct and indirect measures of feed intake
Australian Journal of Agricultural Research
A deterministic approach was used to evaluate the effect of incorporating direct and indirect mea... more A deterministic approach was used to evaluate the effect of incorporating direct and indirect measures of feed intake as additional selection criteria in breeding schemes for Hereford cattle. A 2-tier nucleus breeding scheme consisting of a nucleus and a commercial sector was assumed. Four breeding objectives specific to Australian Hereford cattle were considered. These addressed production systems that targetted 4 markets (Domestic Supermarket, 'Hereford Prime', Short-fed Export, and Long-fed Export). The breeding objectives differed especially in the feed cost involved for differing amounts of grain finishing and in the extent to which marbling is valued by the market (from none to quite a lot). The breeding schemes evaluated differed in the measures available for use as selection criteria. The schemes ranged from one that utilised growth, scanned carcass and fertility criteria currently available to Australian cattle breeders (Scheme 1) to one which also incorporated resi...
Livestock Science
The aim of this study was to determine the interrelationships between milk yield, total digestibl... more The aim of this study was to determine the interrelationships between milk yield, total digestible nutrient (TDN) intake and body weight. A total of 14,900 records of weekly (from the 1st week to 20th week after calving) weights of milk yield and TDN intake and body weight from 745 multiparous Holstein cows in Japan were used. In addition, attempts were made to predict energy requirement in early lactation of dairy cows using metabolizable energy (ME) system. The Wood's function (y t = at b e À ct) was fitted to each animal record to derive secondary traits (parameters, weeks at peak or bottom, maximum-minimum values and predicted daily body weight gain). The average goodness of fit, as assessed by the R 2 value, was highest for TDN intake (0.82) and lowest for body weight (0.59). The weeks at peak milk yield and TDN intake and minimum weight were 6.0, 10.0 and 5.5, respectively. Phenotypic correlations within the same trait were negative between parameters a and b and positive between b and c. Relatively large correlations between traits were obtained for a values and maximum-minimum traits (maximum milk yield and TDN intake and minimum body weight). In addition, the phenotypic correlations between predicted daily gain and a value for milk yield were negative during the first 5 weeks after calving. A comparison of ME intakes estimated from Wood's function and ME intake predicted from energy systems showed that the mean-square prediction error (MSPE) was largest in the first week and smallest in the fourth week. The results suggest that the Wood's function is inadequate in predicting body weight changes in early lactation.
Asian-Australasian Journal of Animal Sciences
A model Indigenous Thai beef cattle breeding structure consisting of nucleus, multiplier and comm... more A model Indigenous Thai beef cattle breeding structure consisting of nucleus, multiplier and commercial units was used to evaluate the effect of changes in heritabilities of and genetic correlations between adaptation traits on genetic gain and profitability. A breeding objective that incorporated adaptation was considered. Two scenarios for improving both the production and the adaptation of animals where also compared in terms of their genetic and economic efficiency. A base scenario was modelled where selection is for production traits and adaptation is assumed to be under the forces of natural selection. The second scenario (+Adaptation) included all the information available for base scenario with the addition of indirect measures of adaptation. These measures included tick count (TICK), faecal egg count (FEC) and rectal temperature (RECT). Therefore, the main difference between these scenarios was seen in the records available for use as selection criteria and hence the level of investments. Additional genetic gain and profitability was generated through incorporating indirect measures of adaptation as criteria measured in the breeding program. Unsurprisingly, the results were sensitive to the changes in heritabilities and genetic correlations between adaptation traits. However, there were more changes in the genetic gain and profitability of the breeding program when the genetic correlations of adaptation and its indirect measures were varied than when the correlations between these measures were. The changes in the magnitudes of the genetic gain and profit per cow stresses the importance of using reliable estimates of these traits in any breeding program.
Journal of Animal Science, 2005
The importance of genotype × environment (region or management system) interactions for carcass t... more The importance of genotype × environment (region or management system) interactions for carcass traits in Japanese Black cattle was investigated using both univariate and multivariate animal models. The univariate approach was used mainly to test the significance of interaction effects. The multivariate approach was used to estimate genetic correlations, which indicated the magnitude of genotype × environment (GE) interactions. The more a genetic correlation deviates from 1, the larger the interaction. From the univariate approach, the addition of genotype × environment (region or management system) interaction (co)variance components resulted in an improved fit of the
Non-genetic sources of variation and temporal variability in growth and feed efficiency traits among phylogenetically distinct clusters of indigenous chicken in Kenya
Tropical Animal Health and Production, 2016
This study aims to investigate the influence of non-genetic factors on feed efficiency in indigen... more This study aims to investigate the influence of non-genetic factors on feed efficiency in indigenous chicken. Residual feed intake (RFI), residual gain (RG) and residual intake and gain (RIG) were used as measures of feed efficiency. Feed intake and body weight data were collected on 107 experimental birds on a daily and weekly basis, respectively, from ages 11 to 20 weeks. A general linear model was fitted to determine the effect of sex, cluster, genotype and hatch group on mean performance and to assess temporal variation across clusters. The overall mean performance for daily gain (ADG), daily feed intake (ADFI), weekly metabolic body weight (MBW), RFI, RG and RIG was 10.38 g/day, 133.01 g/day, 164.12 g/day, 0.00 (±14.23), 0.00 (±1.83) and 0.00 (±14.64), respectively. Sex significantly influenced variation in ADG and RG while hatch group influenced all traits except ADFI. Cluster and genotype had no effect on the traits. Interaction between sex and cluster significantly influenced ADFI, RFI and RIG. There was a significant temporal variation within and among clusters resulting in re-ranking of the phylogenetic groups in efficiency across the test period. Results indicate that growth and feed efficiency traits are influenced by non-genetic factors which should be accounted for, to reduce bias and improve accuracy of performance evaluations in the indigenous chicken.
Variation and Repeatability of Natural Antibodies Against Keyhole Limpet Hemocyanin of Indigenous Chicken of Kenya
Genomics and Applied Biology, 2016
Population structure and demographic trends of the registered Sahiwal cattle in Kenya
Tropical Animal Health and Production, 2016
Sahiwal cattle breed is an important genetic resource that supports livelihoods of pastoralists i... more Sahiwal cattle breed is an important genetic resource that supports livelihoods of pastoralists in Kenya. However, information about its population structure, demographic trends, and genetic diversity is scarce. The objective of this study was to characterize the population structure, explore demographic trends, and evaluate genetic diversity parameters of the breed through pedigree analysis. Pedigree data from National Sahiwal Stud and Kenya Stud Book were combined and analyzed using POPREP software package. The number of registered breeding animals indicated a downward trend over time. Generation interval was longer by 3 years in males than in females. Average inbreeding coefficient was 0.58 % for all animals and 2.23 % for inbred animals. Average inbreeding between 1960 and 2008 for inbred animals decreased at -0.0012 % per year while for the entire breed increased at 0.025 % per year. Additive genetic relationship in the whole population was 0.87 %. The effective population size declined over time and was lower than that recommended to maintain genetic diversity in the long term. The breed was found to be losing genetic diversity over time, and therefore a strategy to reduce inbreeding rate and increase effective population size is recommended.
Journal of Agricultural Science, 2013
Predictive functions for milk yield, dry matter intake, and phosphorous-manure derived from the N... more Predictive functions for milk yield, dry matter intake, and phosphorous-manure derived from the National Research Council 2001 and the present study were incorporated in the development of a multiple objective dairy feed formulation software program (MoF-Dairy Edition-2010); that attempted to optimise feed cost, milk yield and profits while minimising Phosphorous-excretion in manure. Important objects in the feed milling industry considered in the program development were feed millers, dairy farmers, and government feed policy regulatory guidelines. The multi-objective formulation approach comprises hierarchical design levels which include data, model, tools, and output layers. Program database objects are manipulated using VB.NET programming language within a Microsoft .NET Framework Environment. Users interact with the program by providing individual details after which a customer system instance is created. Program formulation inputs are entered through VB forms linked to the core simulation model layer (Microsoft SQL Server Database) to automatically calculate and generate nutrient requirements in accordance with NRC, 2001 for the particular cow or cow production groups under specified production performance parameters. The final solution is obtained by allowing the program to solve for the most feasible combination of available ingredients under the imposed formulation, ingredient as well as nutrient constraints. Program outputs include tailor-made reports on feed formulae; and the accompanying physical nutrient compositions and nutrient deviation analysis; potential unit and gross P-manure environmental pollution, and business economic analysis; detailing concentrate supplementation rates per cow per milking as well as the corresponding projected daily milk profit margins.
Genetic and economic aspects of breeding for dairy production in Kenya
A new Mathematical Method of Predict Protein and Fat Retention in Domesticated Mammals
Integrated goat projects in Kenya: impact on genetic improvement
ABSTRACT
The influence of economic criteria on ranking of genotypes under different circumstances
Economic Values for Resistance to Helminthosis and Newcastle Disease in Indigenous Chicken in the Tropics
The economic values for resistance to helminthosis and Newcastle Disease (ND) in indigenous chick... more The economic values for resistance to helminthosis and Newcastle Disease (ND) in indigenous chicken were estimated relative to egg number (EN), average daily gain (ADG, g) and live weight at 21 weeks (LW, g) using selection index methodology. Both traditional and risk-rated economic values for EN, ADG and LW were used. Faecal worm egg count (FEC, epg) and antibody response (Ab, HI to log2) were used as indicator traits for helminthosis and ND respectively. The economic values were estimated assuming four breeding objective options i.e., 1) where response in single-trait selection was equivalent to index response for that trait; 2) response from the desired trait(s) is maximized; 3) response achieved when the response in FEC and Ab were zero and 4) response achieved when the response in FEC and Ab were minimum. The economic values for FEC under single-trait selection were negative in options 1, 3 and 4 while those for Ab were negative in option 1 only. Since large negative economic v...
Breeding Practices and Traits of Economic Importance for Indigenous Chicken in South Sudan
Journal of Animal Production, Nov 30, 2022
Indigenous Chicken Ecotypes in Kenya
Indigenous chicken (IC) comprises several ecotypes which exhibit a high between-and within-ecotyp... more Indigenous chicken (IC) comprises several ecotypes which exhibit a high between-and within-ecotype variations in performance. However, genetic and feeding interventions targeted at improving their low productivity have been applied uniformly disregarding the apparent ecotype differences and without a sound biological basis targeted at manipulating the biological process of growth. Consequently, breeding strategies and feed formulation have been unmatched with the biological process of growth of the different ecotypes. Quantitative description of the growth patterns of ecotypes upon which to design appropriate breeding and feeding interventions is limited. This book compared body weights of ecotypes and modeled the growth curves to estimate the associated parameters and their relationship using growth models (Von-Bertalanffy, Gompertz, Logistic, and Brody). The study also estimated heritabilities, genetic and phenotypic correlations. The book reveals the differences in growth curve p...
Asian-Australasian Journal of Animal Sciences, 2019
This paper presents a review of dairy goat production in sub-Saharan Africa (SSA) from 2010-2017,... more This paper presents a review of dairy goat production in sub-Saharan Africa (SSA) from 2010-2017, its current state, constraints and prospects for research and development. Since the introduction of dairy goats in SSA in pre-colonial times, their populations have continued to increase due to declining land size as a result of land fragmentation and increasing demand for goat milk. The current goat population in SSA is 372,716,040 head of which only 15.98% used for milk production. Populations in the Eastern and Western regions of SSA have shown an increasing trend from 2010 to 2017. The Southern Africa goat population is on the decline at an annual rate of about 1.77% whereas Central Africa has had a constant goat population within the same period. Eastern Africa reported the highest increase in the population of goats used for milk production. Milk production was highest in Eastern Africa and lowest in Southern Africa. However, dairy goat productivity remained constant in the Eastern region throughout the review period. Dairy goats are mainly raised under smallholder mixed crop-livestock systems. To enhance the development of the dairy goat, concerted efforts should be made to alleviate the constraints that stifle its growth. These constraints can be categorized into nutrition and feeding, breeding and reproduction, diseases, parasites, climate change, and underdeveloped dairy goat products market. Effective management of dairy goats requires a holistic approach and there is the need to expand the markets by further sensitization on the nutritional and medicinal advantages of dairy goat products. In order to achieve rapid development in the dairy goat sub sector, research and development initiatives should be directed towards alleviating the hurdles in nutrition and feeding, breeding, animal health and resilience as well as dairy goat markets.
African Journal of Biotechnology Genomic composition factors affect codon usage in porcine genome
AFRICAN JOURNAL OF BIOTECHNOLOGY
The objective of the study was to determine the codon usage bias in the porcine genome and deciph... more The objective of the study was to determine the codon usage bias in the porcine genome and decipher its determinants. To investigate the underlying mechanisms of codon bias, the coding sequence (CDS) from the swine reference sequence (ssc10.2) was extracted using Biomart. An in house built Perl script was used to derive various genomic traits and codon indices. Analysis was done using R statistical package, and correlations and multivariate regressions were performed. We report the existence of codon usage bias that might suggest existence of weak translational selection. The codon bias is feebly related to nucleotide composition (GC%, GC3, CDS length). This study can be explored for designing degenerate primers, necessitate selecting appropriate hosts expression systems to manipulate the expression of target genes in vivo or in vitro and improve the accuracy of gene prediction from genomic sequences thus maximizing the effectiveness of genetic manipulations in synthetic biology.
Direct and maternal (co)variance components and genetic parameters for growth and reproductive traits in the Boran cattle in Kenya
Tropical Animal Health and Production, 2008
Direct and maternal (co)variance components and genetic parameters were estimated for growth and ... more Direct and maternal (co)variance components and genetic parameters were estimated for growth and reproductive traits in the Kenya Boran cattle fitting univariate animal models. Data consisted of records on 4502 animals from 81 sires and 1010 dams collected between 1989 and 2004. The average number of progeny per sire was 56. Direct heritability estimates for growth traits were 0.34, 0.12, 0.19, 0.08 and 0.14 for birth weight (BW), weaning weight (WW), 12-month weight (12W), 18-month weight (18W) and 24-month weight (24W), respectively. Maternal heritability increased from 0.14 at weaning to 0.34 at 12 months of age but reduced to 0.11 at 24 months of age. The maternal permanent environmental effect contributed 16%, 4% and 10% of the total phenotypic variance for WW, 12W and 18W, respectively. Direct-maternal genetic correlations were negative ranging from -0.14 to -0.58. The heritability estimates for reproductive traits were 0.04, 0.00, 0.15, 0.00 and 0.00 for age at first calving (AFC), calving interval in the first, second, and third parity, and pooled calving interval. Selection for growth traits should be practiced with caution since this may lead to a reduction in reproduction efficiency, and direct selection for reproductive traits may be hampered by their low heritability.
This paper uses data from a survey of one hundred and eighty four dairy households in two divisio... more This paper uses data from a survey of one hundred and eighty four dairy households in two divisional administrative zones in the Kenya highlands to empirically analyze the factors that influence the choice of a milk marketing channel. Multinomial logit econometric estimation results show that distance to milk collection centre, education level, membership of the household head to farmers' group/organization, the number of cows ownedn by the household, and the coefficiency of variation in prices significantly influenced the choice of a marketing channel. Private channel players are yet to focus on tapping the production potential of farmers with small herd sizes and encouraging group formation to exploit the social capital. The study demonstrates the need for the private sector to enhance milk collection at the unexplored areas to exploit the milk supply potentials. The implications for policy are provide.
Data for: Meta-analysis of genetic parameters for traits of economic importance for beef cattle in the tropics
The data is a compilation of studies that have reported various parameters for different traits o... more The data is a compilation of studies that have reported various parameters for different traits of importance for beef breeds in the tropics
Economic evaluation of Hereford cattle breeding schemes incorporating direct and indirect measures of feed intake
Australian Journal of Agricultural Research
A deterministic approach was used to evaluate the effect of incorporating direct and indirect mea... more A deterministic approach was used to evaluate the effect of incorporating direct and indirect measures of feed intake as additional selection criteria in breeding schemes for Hereford cattle. A 2-tier nucleus breeding scheme consisting of a nucleus and a commercial sector was assumed. Four breeding objectives specific to Australian Hereford cattle were considered. These addressed production systems that targetted 4 markets (Domestic Supermarket, 'Hereford Prime', Short-fed Export, and Long-fed Export). The breeding objectives differed especially in the feed cost involved for differing amounts of grain finishing and in the extent to which marbling is valued by the market (from none to quite a lot). The breeding schemes evaluated differed in the measures available for use as selection criteria. The schemes ranged from one that utilised growth, scanned carcass and fertility criteria currently available to Australian cattle breeders (Scheme 1) to one which also incorporated resi...
Livestock Science
The aim of this study was to determine the interrelationships between milk yield, total digestibl... more The aim of this study was to determine the interrelationships between milk yield, total digestible nutrient (TDN) intake and body weight. A total of 14,900 records of weekly (from the 1st week to 20th week after calving) weights of milk yield and TDN intake and body weight from 745 multiparous Holstein cows in Japan were used. In addition, attempts were made to predict energy requirement in early lactation of dairy cows using metabolizable energy (ME) system. The Wood's function (y t = at b e À ct) was fitted to each animal record to derive secondary traits (parameters, weeks at peak or bottom, maximum-minimum values and predicted daily body weight gain). The average goodness of fit, as assessed by the R 2 value, was highest for TDN intake (0.82) and lowest for body weight (0.59). The weeks at peak milk yield and TDN intake and minimum weight were 6.0, 10.0 and 5.5, respectively. Phenotypic correlations within the same trait were negative between parameters a and b and positive between b and c. Relatively large correlations between traits were obtained for a values and maximum-minimum traits (maximum milk yield and TDN intake and minimum body weight). In addition, the phenotypic correlations between predicted daily gain and a value for milk yield were negative during the first 5 weeks after calving. A comparison of ME intakes estimated from Wood's function and ME intake predicted from energy systems showed that the mean-square prediction error (MSPE) was largest in the first week and smallest in the fourth week. The results suggest that the Wood's function is inadequate in predicting body weight changes in early lactation.
Asian-Australasian Journal of Animal Sciences
A model Indigenous Thai beef cattle breeding structure consisting of nucleus, multiplier and comm... more A model Indigenous Thai beef cattle breeding structure consisting of nucleus, multiplier and commercial units was used to evaluate the effect of changes in heritabilities of and genetic correlations between adaptation traits on genetic gain and profitability. A breeding objective that incorporated adaptation was considered. Two scenarios for improving both the production and the adaptation of animals where also compared in terms of their genetic and economic efficiency. A base scenario was modelled where selection is for production traits and adaptation is assumed to be under the forces of natural selection. The second scenario (+Adaptation) included all the information available for base scenario with the addition of indirect measures of adaptation. These measures included tick count (TICK), faecal egg count (FEC) and rectal temperature (RECT). Therefore, the main difference between these scenarios was seen in the records available for use as selection criteria and hence the level of investments. Additional genetic gain and profitability was generated through incorporating indirect measures of adaptation as criteria measured in the breeding program. Unsurprisingly, the results were sensitive to the changes in heritabilities and genetic correlations between adaptation traits. However, there were more changes in the genetic gain and profitability of the breeding program when the genetic correlations of adaptation and its indirect measures were varied than when the correlations between these measures were. The changes in the magnitudes of the genetic gain and profit per cow stresses the importance of using reliable estimates of these traits in any breeding program.
Journal of Animal Science, 2005
The importance of genotype × environment (region or management system) interactions for carcass t... more The importance of genotype × environment (region or management system) interactions for carcass traits in Japanese Black cattle was investigated using both univariate and multivariate animal models. The univariate approach was used mainly to test the significance of interaction effects. The multivariate approach was used to estimate genetic correlations, which indicated the magnitude of genotype × environment (GE) interactions. The more a genetic correlation deviates from 1, the larger the interaction. From the univariate approach, the addition of genotype × environment (region or management system) interaction (co)variance components resulted in an improved fit of the
Non-genetic sources of variation and temporal variability in growth and feed efficiency traits among phylogenetically distinct clusters of indigenous chicken in Kenya
Tropical Animal Health and Production, 2016
This study aims to investigate the influence of non-genetic factors on feed efficiency in indigen... more This study aims to investigate the influence of non-genetic factors on feed efficiency in indigenous chicken. Residual feed intake (RFI), residual gain (RG) and residual intake and gain (RIG) were used as measures of feed efficiency. Feed intake and body weight data were collected on 107 experimental birds on a daily and weekly basis, respectively, from ages 11 to 20 weeks. A general linear model was fitted to determine the effect of sex, cluster, genotype and hatch group on mean performance and to assess temporal variation across clusters. The overall mean performance for daily gain (ADG), daily feed intake (ADFI), weekly metabolic body weight (MBW), RFI, RG and RIG was 10.38 g/day, 133.01 g/day, 164.12 g/day, 0.00 (±14.23), 0.00 (±1.83) and 0.00 (±14.64), respectively. Sex significantly influenced variation in ADG and RG while hatch group influenced all traits except ADFI. Cluster and genotype had no effect on the traits. Interaction between sex and cluster significantly influenced ADFI, RFI and RIG. There was a significant temporal variation within and among clusters resulting in re-ranking of the phylogenetic groups in efficiency across the test period. Results indicate that growth and feed efficiency traits are influenced by non-genetic factors which should be accounted for, to reduce bias and improve accuracy of performance evaluations in the indigenous chicken.
Variation and Repeatability of Natural Antibodies Against Keyhole Limpet Hemocyanin of Indigenous Chicken of Kenya
Genomics and Applied Biology, 2016
Population structure and demographic trends of the registered Sahiwal cattle in Kenya
Tropical Animal Health and Production, 2016
Sahiwal cattle breed is an important genetic resource that supports livelihoods of pastoralists i... more Sahiwal cattle breed is an important genetic resource that supports livelihoods of pastoralists in Kenya. However, information about its population structure, demographic trends, and genetic diversity is scarce. The objective of this study was to characterize the population structure, explore demographic trends, and evaluate genetic diversity parameters of the breed through pedigree analysis. Pedigree data from National Sahiwal Stud and Kenya Stud Book were combined and analyzed using POPREP software package. The number of registered breeding animals indicated a downward trend over time. Generation interval was longer by 3 years in males than in females. Average inbreeding coefficient was 0.58 % for all animals and 2.23 % for inbred animals. Average inbreeding between 1960 and 2008 for inbred animals decreased at -0.0012 % per year while for the entire breed increased at 0.025 % per year. Additive genetic relationship in the whole population was 0.87 %. The effective population size declined over time and was lower than that recommended to maintain genetic diversity in the long term. The breed was found to be losing genetic diversity over time, and therefore a strategy to reduce inbreeding rate and increase effective population size is recommended.
Journal of Agricultural Science, 2013
Predictive functions for milk yield, dry matter intake, and phosphorous-manure derived from the N... more Predictive functions for milk yield, dry matter intake, and phosphorous-manure derived from the National Research Council 2001 and the present study were incorporated in the development of a multiple objective dairy feed formulation software program (MoF-Dairy Edition-2010); that attempted to optimise feed cost, milk yield and profits while minimising Phosphorous-excretion in manure. Important objects in the feed milling industry considered in the program development were feed millers, dairy farmers, and government feed policy regulatory guidelines. The multi-objective formulation approach comprises hierarchical design levels which include data, model, tools, and output layers. Program database objects are manipulated using VB.NET programming language within a Microsoft .NET Framework Environment. Users interact with the program by providing individual details after which a customer system instance is created. Program formulation inputs are entered through VB forms linked to the core simulation model layer (Microsoft SQL Server Database) to automatically calculate and generate nutrient requirements in accordance with NRC, 2001 for the particular cow or cow production groups under specified production performance parameters. The final solution is obtained by allowing the program to solve for the most feasible combination of available ingredients under the imposed formulation, ingredient as well as nutrient constraints. Program outputs include tailor-made reports on feed formulae; and the accompanying physical nutrient compositions and nutrient deviation analysis; potential unit and gross P-manure environmental pollution, and business economic analysis; detailing concentrate supplementation rates per cow per milking as well as the corresponding projected daily milk profit margins.
Genetic and economic aspects of breeding for dairy production in Kenya
A new Mathematical Method of Predict Protein and Fat Retention in Domesticated Mammals
Integrated goat projects in Kenya: impact on genetic improvement
ABSTRACT
The influence of economic criteria on ranking of genotypes under different circumstances
Economic Values for Resistance to Helminthosis and Newcastle Disease in Indigenous Chicken in the Tropics
The economic values for resistance to helminthosis and Newcastle Disease (ND) in indigenous chick... more The economic values for resistance to helminthosis and Newcastle Disease (ND) in indigenous chicken were estimated relative to egg number (EN), average daily gain (ADG, g) and live weight at 21 weeks (LW, g) using selection index methodology. Both traditional and risk-rated economic values for EN, ADG and LW were used. Faecal worm egg count (FEC, epg) and antibody response (Ab, HI to log2) were used as indicator traits for helminthosis and ND respectively. The economic values were estimated assuming four breeding objective options i.e., 1) where response in single-trait selection was equivalent to index response for that trait; 2) response from the desired trait(s) is maximized; 3) response achieved when the response in FEC and Ab were zero and 4) response achieved when the response in FEC and Ab were minimum. The economic values for FEC under single-trait selection were negative in options 1, 3 and 4 while those for Ab were negative in option 1 only. Since large negative economic v...