Phenotypic Trends Research Articles

Genetic and phenotypic trends for growth traits in Mecheri sheep

Data on growth of Mecheri sheep at Mecheri Sheep Research Station, Pottaneri, Tamil Nadu over a period of sixteen years from 1991 to 2006 were collected and analysed. Body weights for birth, 3, 6, 9 and 12 months of age were used to estimate the breeding values of sires by derivative-free maximum likelihood (DFREML) method. The genetic trends for birth, 3, 6, 9, and 12 months body weights of Mecheri lambs ranged from -0.15 to 0.23, -0.61 to 0.85, -1.12 to 0.91, -2.24 to 2.92 and -1.50 to 4.31 kg, respectively and their corresponding phenotypic trends varied from 2.02 to 2.72, 6.49 to 10.54, 9.94 to 14.33, 11.40 to 19.73 and 10.07 to 25.40 indicating an overall positive genetic change in growth traits.

Floral pigmentation patterns provide an example of Gloger's rule in plants

Ecogeographic rules explain spatial trends in biodiversity, species interactions and phenotypes(1). Gloger's rule and its corollaries state that pigmentation of endothermic animals will increase from more polar to equatorial regions due to changing selective pressures including heat, humidity, predation and UV irradiance(2-4). In plants, floral pigmentation varies within and among taxa, yet causes of wide-scale geographic variation are lacking. We show that Gloger's rule explains patterns of variation in UV-absorbing floral pigmentation in a widespread plant, Argentina anserina (Rosaceae). Specifically, the floral pigmentation pattern unique to the UV spectrum (UV 'bullseye') increases with proximity to the Equator in both hemispheres, and larger bullseyes are associated with higher UVB incidence. Experiments confirm UV as an agent of selection and bullseye size as a target. Results extend the generality of an ecogeographic rule-formulated for animals-to plants, implicating UV as a selective agent on a floral trait generally assumed to enhance plant-pollinator interactions. Global change is expected to alter UV irradiance in terrestrial systems(5), potentially intensifying the importance of UV-mediated selection to floral evolution. Because floral UV reflectance and pattern enhance pollinator attraction(6,7), altered selective regimes could disrupt coevolved plant-pollinator interactions, weakening an important ecosystem service(8).

Genetic parameters and genetic gains for reproductive traits of Arabi sheep

The current study reports, for the first time, the genetic parameters and genetic, phenotypic and environmental correlations and trends of reproductive traits in Arabi sheep. Data were collected at Animal Science Research Station of Khuzestan Ramin Agricultural and Natural Resources University (ASRSKRANRU), south-west of Iran from 2001 to 2008. Litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB) and total litter weight at weaning (TLWW) averaged 1.11 lambs, 1.01 lambs, 3.83 kg, 19.43 kg, 4.16 kg and 20.12 kg, respectively. Genetic parameters and correlations were estimated with univariate and bivariate models using restricted maximum likelihood, breeding values of animals were estimated with best linear unbiased prediction (BLUP) and genetic- and phenotypic trends by regression of ewes? average breeding values and phenotypic least square means on year of birth respectively. Random effects were fitted by additive direct genetic effects and permanent environment related to the ewe as well as service sire effects, in addition to fixed effects of ewe age at lambing and lambing year. Heritability estimates of 0.05, 0.02, 0.13, 0.12, 0.04, and 0.06, and repeatability estimates of 0.08, 0.06, 0.17, 0.16, 0.14 and 0.21 for the six traits, respectively. Genetic correlations between traits varied from ?0.82 to 0.94. Phenotypic correlations were lower, ranging from ?0.33 to 0.52. Estimated annual genetic progress was very low; ?0.003 lambs for LSW and 15 g for TLWW. Annual phenotypic trend was only significant for LSW being 0.007 lambs. The study concluded that indirect selection based on total litter weight at weaning could be efficient for the traits studied.

Genotype–phenotype correlation and mutation spectrum in a large cohort of patients with inherited retinal dystrophy revealed by next-generation sequencing

Inherited retinal dystrophy (IRD) is a leading cause of blindness worldwide. Because of extreme genetic heterogeneity, the etiology and genotypic spectrum of IRD have not been clearly defined, and there is limited information on genotype-phenotype correlations. The purpose of this study was to elucidate the mutational spectrum and genotype-phenotype correlations of IRD. We developed a targeted panel of 164 known retinal disease genes, 88 candidate genes, and 32 retina-abundant microRNAs, used for exome sequencing. A total of 179 Chinese families with IRD were recruited. In 99 unrelated patients, a total of 124 mutations in known retinal disease genes were identified, including 79 novel mutations (detection rate, 55.3%). Moreover, novel genotype-phenotype correlations were discovered, and phenotypic trends noted. Three cases are reported, including the identification of AHI1 as a novel candidate gene for nonsyndromic retinitis pigmentosa. This study revealed novel genotype-phenotype correlations, including a novel candidate gene, and identified 124 genetic defects within a cohort with IRD . The identification of novel genotype-phenotype correlations and the spectrum of mutations greatly enhance the current knowledge of IRD phenotypic and genotypic heterogeneity, which will assist both clinical diagnoses and personalized treatments of IRD patients.

Environmental and genetic factors affecting cow survival of Israeli Holsteins

The objectives were to investigate the effects of various environmental factors that may affect herd-life of Israeli Holsteins, including first-calving age and season, calving ease, number of progeny born, and service sire for first calving in complete and truncated records; and to estimate heritabilities and genetic correlations between herd-life and the other traits included in the Israeli breeding index. The basic data set consisted of 590,869 cows in milk recording herds with first freshening day between 1985 and at least 8 yr before the cut-off date of September 15, 2013. Herd-life was measured as days from first calving to culling. The phenotypic and genetic trends for herd-life were 5.7 and 16.8d/yr. The genetic trend was almost linear, whereas the phenotypic trend showed 4 peaks and 3 valleys. Cows born in February and March had the shortest herd-life, whereas cows born in September had the longest herd-life. Herd-life was maximal with calving age of 23mo, which is 1mo less than the mean calving age, and minimal at 19 and 31mo of calving age. Dystocia and twinning on first-parity calving reduced herd-life by approximately180 and 120d, but the interaction effect increased herd-life by 140d. Heritability for herd-life was 0.14. Despite the fact that the service sire effect was significant in the fixed model analysis, service sire effect accounted for <0.05% of the total variance. In the analysis of 1,431,938 truncated records, the effects of dystocia and twinning rate were very similar but less than 50% of the effects found in the analysis of complete records. Pregnancy at the truncation date increased expected herd-life by 432d. The correlation between actual herd-life and predicted herd-life based on truncated records was 0.44. Genetic correlations between the truncated records and actual herd-life were 0.75 for records truncated after 6mo but approached unity for records truncated after 3 yr. The genetic correlations of herd-life with first-parity milk, fat, and protein production, somatic cell score (SCS), and female fertility were all positive, except for SCS, in which negative values are economically favorable. The highest correlations with herd-life in absolute value were with female fertility and SCS.

Abstract 1882: The expression phenotype of SNPs linked to the risk for prostate cancer

Abstract Numerous Genome Wide Association (GWA) studies of large populations have provided limited biomarkers for cancer and few linkages to phenotype. We investigated whether SNPs that are known to be associated with prostate cancer (PCa) affect expression in prostate stroma. The stroma of prostate tumors provides genetically homogenous tissue type with hundreds of tumor-dependent expression changes [1] which favors linkage identification. We surveyed published GWA studies covering a total of ∼90,000 patients and selected the most significant 35 susceptibility loci for further linkage analysis. We also selected 4030 transcripts previously associated with PCa diagnosis and prognosis. We then investigated 47 PCa cases using genetic variations in nontumor DNA (Illumina Human1M-Duov3_B snp arrays) and correlating the genotypes with RNA gene expression data from the same patients (U133 plus 2.0 arrays). A novel eQTL (Expression Quantitative Trait Loci) analysis was carried out by a modified BAYES method to analyze the associations between the risk variants and expressed transcripts jointly in a single model. The model assumed that a risk variant can be associated with multiple RNA expression changes and vice versa. We observed 47 significant linkages between 8 risk variants and 46 significant expression changes. The false discovery rates of two resampling studies are 0.03 and 0.05, respectively, which indicated the 47 linkages are significant. All linkages are “trans' linkages indicating remote effects of key SNPs on expressing genes. This is the first study to identify trans-linkages between multiple SNPs and multiple significant expression changes identified in cancer stroma. The linkages also associated with trends in clinical phenotypes. The strongest trend is between linkage rs9623117(C)-FOXD1 and biochemical relapse (p=0.01). The study reveals links between SNPs associated with PCa risk and transcription, which may identify the subset of patients where these genotypes may affect relevant phenotypes. [1] Jia et al., Cancer Research 2011; 71:2476-2487. Citation Format: Xin Chen, Zhenyu Jia, Michael McClelland, Farah Rahmatpanah, Dan Mercola. The expression phenotype of SNPs linked to the risk for prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1882. doi:10.1158/1538-7445.AM2014-1882

Quantitative genetic variance and multivariate clines in the Ivyleaf morning glory, Ipomoea hederacea.

Clinal variation is commonly interpreted as evidence of adaptive differentiation, although clines can also be produced by stochastic forces. Understanding whether clines are adaptive therefore requires comparing clinal variation to background patterns of genetic differentiation at presumably neutral markers. Although this approach has frequently been applied to single traits at a time, we have comparatively fewer examples of how multiple correlated traits vary clinally. Here, we characterize multivariate clines in the Ivyleaf morning glory, examining how suites of traits vary with latitude, with the goal of testing for divergence in trait means that would indicate past evolutionary responses. We couple this with analysis of genetic variance in clinally varying traits in 20 populations to test whether past evolutionary responses have depleted genetic variance, or whether genetic variance declines approaching the range margin. We find evidence of clinal differentiation in five quantitative traits, with little evidence of isolation by distance at neutral loci that would suggest non-adaptive or stochastic mechanisms. Within and across populations, the traits that contribute most to population differentiation and clinal trends in the multivariate phenotype are genetically variable as well, suggesting that a lack of genetic variance will not cause absolute evolutionary constraints. Our data are broadly consistent theoretical predictions of polygenic clines in response to shallow environmental gradients. Ecologically, our results are consistent with past findings of natural selection on flowering phenology, presumably due to season-length variation across the range.

Temporal trends in non-stricturing and non-penetrating behaviour at diagnosis of Crohn's disease in Örebro, Sweden: A population-based retrospective study

Background and aimThe incidence of Crohn's disease (CD) is continuing to rise in several countries and in others it appears to have already levelled off after a period of increase. We updated our previous population-based study, by re-extraction of all information on patients diagnosed with CD between 1963 and 2010. Our aim was to assess temporal trends in incidence, prevalence and disease phenotype at diagnosis. MethodsPatients of all ages with a potential diagnosis of CD were identified retrospectively by evaluation of medical notes of all current and previous patients at the colitis clinic, Örebro University Hospital amended by computerised search in the inpatient, outpatient, primary care and histopathological records. Diagnosis was confirmed by subsequent evaluation of medical notes. Disease phenotype was defined according to the Montreal classification. ResultsThe incidence increased over time, especially among Crohn's disease, A1 and A3. SaTScan model revealed a statistically significant high incidence during 1991–2010 (p=0.0001). The median age at diagnosis increased from 28 (3–79) years to 37 (5–87) years (p=0.0002). The point prevalence increased from 21/105 (14–32) in 1965 to 267/105 (244–291) in 2010. Non-stricturing and non-penetrating disease at diagnosis increased from 12.5% in 1963–1965 to 82.3% in 2006–2010 (p<0.0001). ConclusionThe incidence of CD increased over time, although it seemed to be plateauing during the most recent decades. A striking increase in non-stricturing, non-penetrating disease at diagnosis was observed, suggesting earlier diagnosis or phenotypic change. The observed point prevalence in 2010 is among the highest reported.

Tendências, parâmetros fenotípicos e genéticos de características de crescimento em bovinos Nelore mocho do Nordeste brasileiro

Objetivou-se estimar parâmetros e avaliar a tendência fenotípica e genética de pesos ajustados para 205 (P205); 365 (P365) e 550 (P550) dias de idade, em bovinos da variedade Nelore Mocho, nascidos a partir de 1980, pertencentes a rebanhos localizados na região Nordeste do Brasil. Foram utilizados registros genealógicos de 45.785 animais nascidos entre 1960 e 2009. Os parâmetros e os valores genéticos foram estimados com o método de máxima verossimilhança restrita livre de derivadas (REML) sob o modelo animal, usando aplicativo computacional MTDFREML. A tendência fenotípica e genética das características de crescimento foram estimadas pela regressão do valor genético sobre o ano de nascimento do animal. O coeficiente de herdabilidade direta dos pesos ajustados nas três idades foram 0,19 ± 0,02 (P205); 0,24 ± 0,03 (P365) e 0,18 ± 0,03 (P550), indicando que há potencial de ganhos pela seleção nesses pesos. A herdabilidade materna do P205 foi igual a 0,12 ± 0,02. A tendência genética direta foi igual a 0,016; 0,043 e 0,041kg/ano, para P205, P365 e P550, respectivamente, enquanto a fenotípica foi 1,34; 2,10 e 2,84kg/ano para essas características na mesma sequência, mostrando assim o quanto os ganhos fenotípicos foram superiores aos genotípicos, possivelmente favorecidos por melhorias no manejo dos rebanhos. O monitoramento dos parâmetros e das tendências fenotípica e genética do desenvolvimento ponderal na variedade Nelore Mocho do Nordeste, se apresenta como procedimento importante para nortear a definição de estratégias de manejo com potencial para aumentar os ganhos genéticos de forma consistente.

Molecular factors in dendritic cell responses to adsorbed glycoconjugates

Carbohydrates and glycoconjugates have been shown to exert pro-inflammatory effects on the dendritic cells (DCs), supporting pathogen-induced innate immunity and antigen processing, as well as immunosuppressive effects in the tolerance to self-proteins. Additionally, the innate inflammatory response to implanted biomaterials has been hypothesized to be mediated by inflammatory cells interacting with adsorbed proteins, many of which are glycosylated. However, the molecular factors relevant for surface displayed glycoconjugate modulation of dendritic cell (DC) phenotype are unknown. Thus, in this study, a model system was developed to establish the role of glycan composition, density, and carrier cationization state on DC response. Thiol modified glycans were covalently bound to a model protein carrier, maleimide functionalized bovine serum albumin (BSA), and the number of glycans per BSA modulated. Additionally, the carrier isoelectric point was scaled from a pI of ∼4.0 to ∼10.0 using ethylenediamine (EDA). The DC response to the neoglycoconjugates adsorbed to wells of a 384-well plate was determined via a high throughput assay. The underlying trends in DC phenotype in relation to conjugate properties were elucidated via multivariate general linear models. It was found that glycoconjugates with more than 20 glycans per carrier had the greatest impact on the pro-inflammatory response from DCs, followed by conjugates having an isoelectric point above 9.5. Surfaces displaying terminal α1-2 linked mannose structures were able to increase the inflammatory DC response to a greater extent than did any other terminal glycan structure. The results herein can be applied to inform the design of the next generation of combination products and biomaterials for use in future vaccines and implanted materials.

Selection for morphology, gaits and functional traits in Lusitano horses: II. Fixed effects, genetic trends and selection in retrospect

Mixed model procedures were used to analyze morphology and gaits records collected in about 18,000 Lusitano horses from 900 studs, over a period of 43 years, and functional records collected since 1998, to carry-out a critical assessment of the fixed effects and selection practices followed in this breed. Fixed effects considered in the analysis of morphology (head/neck, shoulder/withers, chest/thorax, back/loin, croup, legs and overall impression), gaits and final score (computed by summing partial morphological and gaits scores) were stud, year, sex, inbreeding and age. Functional traits analyzed were the scores obtained in working equitation dressage (WEDT) and maneability (WEMT) trials and in classical dressage (CD), where fixed effects were event, level of competition, sex, inbreeding and age. Phenotypic trends were moderate over the period analyzed, with a slight increase in height at withers, and a decline in final score. Nevertheless, differences among years were mostly environmental. Males received lower scores for almost all morphological and gaits traits except croup, with a difference of about −1.7 points for final score relative to females. Sex differences were small for functional traits, with general advantage of males in WEMT and CD, and a disadvantage in WEDT. Considerable differences were detected among studs, especially in their environmental effects but also in mean estimated breeding value (EBV), for morphology, gaits and functionality. The environmental effect of competition level in CD resulted in a progressively lower scoring as the competition became more difficult, while for WEMT the pattern was opposite and differences were minor for WEDT. Inbreeding depression was observed for all morphological and gait traits, but the magnitude of its impact was very small for all traits analyzed, never exceeding −0.1% of the mean per 1% inbreeding. Still, for functional traits the effect of inbreeding was negligible. The EBV for morphology, gaits, WEMT and WEDT show considerable variability, indicating that selection can be effective. For CD, however, the distribution of EBV was narrower. The genetic trend was positive but moderate for all traits, and it was slightly higher for head and neck, overall impression, gaits and final score. As a percentage of the mean, these traits and working equitation trials showed the highest responses, which in the best cases did not exceed 0.2% of the mean per year. Genetic selection differentials and the corresponding selection intensities were very modest for all traits analyzed, with a slightly higher intensity in sires when compared to dams.

Parâmetros e tendências genéticas para características de crescimento em bovinos da raça Nelore no Estado da Bahia utilizando inferência bayesiana

O objetivo com esta pesquisa foi estimar parâmetros genéticos e predizer tendências genéticas e fenotípicas para pesos aos 205 (P205), 365 (P365) e 550 (P550) dias de idade, em animais da raça Nelore nascidos no período de 1975 a 2011 no Estado da Bahia. Os dados foram analisados através de modelos bayesianos uni e bicaracterísticos com o programa GIBBS3F90. Os modelos utilizados para as três características incluíram os efeitos aleatórios genéticos (direto e materno), de ambiente permanente maternal, a covariável idade da vaca ao parto (efeito linear e quadrático), além do efeito fixo de grupo de contemporâneos. As herdabilidades (direta) para P205, P365 e P550 apresentaram valores inferiores aos relatados na literatura, contudo, existe possibilidade de ganho genético por meio da seleção. As predições de tendências genéticas e fenotípicas para as características foram obtidas pela regressão linear ponderada da média da variável dependente (valores genéticos e pesos observados) sobre o ano de nascimento. As tendências para P365 e P550 preditas demonstram que houve algum progresso genético para estas duas características, porém, inferiores ao peso aos 205 de idade. Os valores observados indicam pequeno, porém, favorável progresso genético para o efeito direto nas três pesagens. O progresso fenotípico foi alto nas três características, mostrando melhoria ambiental, no estado da Bahia, no decorrer do período estudado.

Prevalence and co-occurrence of hip dysplasia and elbow dysplasia in Dutch pure-bred dogs

Hip as well as elbow dysplasia (HD, ED) are developmental disorders leading to malformation of their respective joints. For a long time both disorders have been scored and targeted for improvement using selective breeding in several Dutch dog populations. In this paper all scores for both HD and ED, given to pure bred dogs in the Netherlands from 2002 to 2010, were analyzed. Heritabilities and correlations between HD and ED were calculated for the 4 most frequently scored breeds. Heritabilities ranged from 0.0 to 0.37 for HD related traits (FCI-score, osteoarthritis, congruity, shape and laxity (Norberg angle); FCI: Fédération Cynologique Internationale) and from 0.0 to 0.39 for ED related traits (IEWG score, osteoarthritis, sclerosis and indentation; IEWG: International Elbow Working Group). HD related traits showed high genetic and residual correlations among each other but were only to a minor extent correlated with ED related traits, which also showed high correlations among each other. Genetic correlations were higher than residual correlations. Phenotypic and genetic trends since 2001 for the four most scored breeds were slightly positive but decreasing over time, indicating that selection over the past decade has not been effective.

Short communication: Genetic evaluation of stillbirth in US Brown Swiss and Jersey cattle

Stillbirth (SB) often results in reduced milk yield, compromised reproductive performance, and decreased dam longevity. Corrective mating can be used as a short-term solution to the problem, but long-term improvement of the population requires the routine calculation of genetic evaluations. Breeding values for SB have been available for Holstein (HO) bulls since 2006, but not for Brown Swiss (BS) or Jersey (JE) bulls. In this study, a multi-breed sire-maternal grandsire threshold model was used to perform genetic evaluations for SB of BS, JE, and HO bulls using more than 14 million purebred and crossbred calving records. Phenotypically, the percentage of SB (%SB) across all lactations were 3.7% in JE, 5.1% in BS, and 6.3% in HO. Direct heritabilities for BS, JE, and HO were 0.008, 0.007, and 0.008, and maternal heritabilities were 0.002, 0.016, and 0.021, respectively. Compared with HO, crossbred calvings from BS and JE bulls bred to HO cows lowered %SB by 1.5 and 1.2%, respectively. In general, %SB increased considerably as calving difficulty increased in all 3 breeds; however, in JE, %SB was constant for dystocia scores of 3 (needed assistance), 4 (considerable force), and 5 (extreme difficulty). Compared with purebred HO calvings, purebred BS and JE calvings had lower phenotypic %SB by up to 5.5 and 7.8%, respectively, and BS × HO and JE × HO crossbred calvings decreased %SB by up to 3.8 and 4.1%, respectively. As expected, SB rates in primiparous cows were higher than those in multiparous cows. Female calves had greater %SB than male calves in all parities for JE and in second-and-later parities for BS. Favorable (decreasing) phenotypic and genetic trends from 1999 to 2009 were observed in all 3 breeds. Heterosis of SB for BS and JE was −0.026 and −0.149, respectively, on the underlying scale, which corresponds to effects on service-sire SB (SSB) and daughter SB (DSB) predicted transmitting ability (PTA) of −0.3 and −0.5% in BS, and −1.5 and −2.7% in JE. Overall, in the current population, BS bulls had the most desirable average SSB PTA of 4.8%, compared with 5.6% for JE and 5.5% for HO. Brown Swiss and JE bulls both had average DSB PTA of 6.5%, lower than that of 7.7% in HO. Average reliabilities of SSB and DSB in 3 breeds ranged from 45 to 50%. The use of a BS-JE-HO multibreed genetic evaluation for SB in the United States is feasible, and the addition of SSB and DSB to the lifetime net merit selection index will help improve the profitability of BS and JE cattle in the United States.

Investigating maternal effects on production traits in Duroc pigs using animal and sire models

Variance components for production traits were estimated using different models to evaluate maternal effects. Data analysed were records from the South African pig performance testing scheme on 22224 pigs from 18 herds, tested between 1990 and 2008. The traits analysed were backfat thickness (BFAT), test period weight gain (TPG), lifetime weight gain (LTG), test period feed conversion ratio (FCR) and age at slaughter (AGES). Data analyses were performed by REML procedures in ASREML, where random effects were successively fitted into animal and sire models to produce different models. The first animal model had one random effect, the direct genetic effects, while the additional random effects were maternal genetic and maternal permanent environmental effects. In the sire model, the random effects fitted were sire and maternal grand sire effects. The best model considered the covariance between direct and maternal genetic effects or between sire and maternal grand sire effects. Fitting maternal genetic effects into the animal model reduced total additive variance, while the total additive variance increased when maternal grand sire effects were fitted into the sire model. The correlations between direct and maternal genetic effects were all negative, indicating antagonism between these effects, hence the need to consider both effects in selection programmes. Direct genetic correlations were higher than other correlations, except for maternal genetic correlations of FCR with TPG, LTG and AGES. There has been direct genetic improvement and almost constant maternal ability in production traits as shown by trends for estimated (EBVs) and maternal breeding values (MBVs), while phenotypic trends were similar to those for EBVs. These results suggest that maternal genetic effects should be included in selection programmes for these production traits. Therefore, the animal-maternal model may be the most appropriate model to use when estimating genetic parameters for production traits in this population.

Estimation of genetic trends for economic traits in crossbred cattle by using regression methods

The present study was conducted on 782 crossbred cows sired by 35 bulls, maintained over the period from 1985 to 2009. The data were analyzed to estimate genetic, phenotypic and environmental changes in characters of economic importance which might have taken place during the several years of selective breeding practiced in the herd. The economic traits studied were first lactation milk yield, first lactation milk yield per day of lactation length and first lactation milk yield per day of calving interval in kg and age at first calving, first lactation length, first calving interval, first service period and first dry period in days. The average genetic changes in a given trait were estimated by four methods. Phenotypic trends were negligible for all the traits except age at first calving while, genetic trends were in desirable direction. Comparison of methods of estimation of genetic trend showed that adjustments for biases due to non-random allotment of dams with respect to their age and merit suggested by Powell and Freeman were useful for increasing the precision of the estimates. This method showed lower magnitude of standard error in comparison to other methods. Method-III showed lower standard error than method-IV. Hence, method –III was the best method of estimation of genetic trends.

Reproductive, Traits, Holstein, Heritability, Repeatability

Data consisting of 2757 records from tow Holstein herds made between 2000 and 2010 were used to examine environmental factors affecting age at first calving (AFC) and calving intervals (CI) and consequently estimate genetic and phenotypic parameters and trends. The overall means and standard errors for AFC and CI were 39.4 ± 7.2 months and 487.5 ± 151.6 days, respectively. The respective heritability estimates were 0.091 ± 0.05 and 0.044 ± 0.032, while the repeatability estimate for CI was 0.096 ± 0.001. The genetic trends for CI and AFC were -0.6d/yr and -0.01mo/yr respectively and were both significant (p0.05). The low heritability for CI and AFC indicated that temporary environmental influences were much greater than genetic influences or permanent environmental influences on these traits.

Genetics and genomics of reproductive performance in dairy and beef cattle

Excellent reproductive performance in both males and females is fundamental to profitable dairy and beef production systems. In this review we undertook a meta-analysis of genetic parameters for female reproductive performance across 55 dairy studies or populations and 12 beef studies or populations as well as across 28 different studies or populations for male reproductive performance. A plethora of reproductive phenotypes exist in dairy and beef cattle and a meta-analysis of the literature suggests that most of the female reproductive traits in dairy and beef cattle tend to be lowly heritable (0.02 to 0.04). Reproductive-related phenotypes in male animals (e.g. semen quality) tend to be more heritable than female reproductive phenotypes with mean heritability estimates of between 0.05 and 0.22 for semen-related traits with the exception of scrotal circumference (0.42) and field non-return rate (0.001). The low heritability of reproductive traits, in females in particular, does not however imply that genetic selection cannot alter phenotypic performance as evidenced by the decline until recently in dairy cow reproductive performance attributable in part to aggressive selection for increased milk production. Moreover, the antagonistic genetic correlations among reproductive traits and both milk (dairy cattle) and meat (beef cattle) yield is not unity thereby implying that simultaneous genetic selection for both increased (milk and meat) yield and reproductive performance is indeed possible. The required emphasis on reproductive traits within a breeding goal to halt deterioration will vary based on the underlying assumptions and is discussed using examples for Ireland, the United Kingdom and Australia as well as quantifying the impact on genetic gain for milk production. Advancements in genomic technologies can aid in increasing the accuracy of selection for especially reproductive traits and thus genetic gain. Elucidation of the underlying genomic mechanisms for reproduction could also aid in resolving genetic antagonisms. Past breeding programmes have contributed to the deterioration in reproductive performance of dairy and beef cattle. The tools now exist, however, to reverse the genetic trends in reproductive performance underlying the observed phenotypic trends.

Genetic , Phenotypic and Environmental Trends towards Improving Body Weight in Barki Sheep

Genetic , Phenotypic and Environmental Trends towards Improving Body Weight in Barki Sheep

Determination of the best model for estimating heritability of economic traits and their genetic and phenotypic trends in Iranian native fowl

Abstract. The objective of the present study was to estimate the heritability and to assess the existence of maternal effects for economic traits in Iranian native fowl. Variance components were estimated for body weight at hatch (BW0), 8 (BW8) and 12 (BW12) weeks of age, age at sexual maturity and weight at sexual maturity, egg number and average egg weight at 28th, 30th and 32nd weeks using restricted maximum likelihood method and six animal models. The best model was determined using the Akaike information criterion for each trait. For age at sexual maturity, the basic model consisting of direct genetic effects was superior. For weight at sexual maturity and egg number, a model consisting of maternal permanent environmental effects in addition to direct genetic effects was the best. For average egg weight at 28th, 30th and 32nd weeks, the model with direct and maternal genetic effects assuming no covariance between them was the best. For BW0, BW8 and BW12, the model including maternal genetic and permanent environmental effects in addition to direct genetic effects was the most appropriate. The estimates of direct heritability ranged from 0.05 (BW0) to 0.35 (weight at sexual maturity). Direct genetic variance and heritability were overestimated if maternal effects were ignored in the statistical model for all traits except ASM. The results indicated that the evaluation of direct and maternal genetic and phenotypic trends based on the best model for each trait was carried out. Maternal genetic trends for BW0, BW8, BW12 and average egg weight at 28th, 30th and 32nd weeks were significantly positive. Present results indicated favourable effects of the performed breeding program for all traits except BW0, during generations.