232 research outputs found

    Genetic Correlations Among Sex-Limited Traits

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    Monte Carlo simulation techniques were used to assess the merits of three methods for calculation of the genetic correlation when traits have been measured on half-sibs of each sex. The restricted maximum likelihood, path coefficient and covariance component estimators did not differ significantly in their accuracy. Path coefficient and covariance component methodologies gave nearly unbiased estimators for traits of high heritability. Across both levels of heritability, the restricted maximum likelihood methodology resulted in genetic correlations being estimated with significantly smaller sampling variance than the other methods. Genetic correlations were estimated for age of puberty, weight at puberty, conceptions per service, gestation length, calving difficulty, progeny birth weight, progeny preweaning daily gain and mature weight measured on females, with postweaning daily gain, carcass weight, fat trim weight, and retail product weight measured on male half-sibs. Correlations of the female traits with postweaning daily gain, carcass weight, and retail product weight generally were similar to each other. Correlations of fat trim weigh with the female traits were similar in magnitude and opposite in sign to the correlations of postweaning daily gain, carcass weight, and retail product weight with the female traits. Predicted correlated responses to one phenotypic standard deviation of selection for increased postweaning daily gain were increased age at puberty 3.39 days, weight at puberty 1.02 kg, dam’s progeny birth weight .50 kg and mature weight 1.45 kg and reduced g station length .20 days and the frequency of calving difficulty .07 percent. The estimated genetic correlations of postweaning daily gain of the dam’s steer half-sibs with conceptions per service and dam’s progeny preweaning daily gain had absolute values greater than one and were positive and negative, respectively. Predicted correlated responses to one phenotypic standard deviation of selection for reduced fat trim weight at a constant age were increased age at puberty 7.22 days, weight at puberty 5.29 kg, gestation length .17 days, the frequency of calving difficulty .05 percent, birth weight, .12 kg and mature weight .22 kg and decreased conceptions per service .01 units. The estimated genetic correlation of age constant fat trim weigh with dam’s progeny preweaning daily gain was less than negative one

    Putative Loci Causing Early Embryonic Mortality in Duroc Swine

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    Lethal recessive alleles that act prenatally may be detected from the absence of homozygous individuals in a population. However, these alleles may be maintained at relatively low frequencies in populations as heterozygotes. In pigs, they may reduce litter size. This study aimed to detect putative lethal variants in the Duroc breed. Phenotypes for the numbers of piglets born (TNB), born live (BA), alive at 24 h (L24), stillborn (SB), and born as mummified fetuses (MM) were available from 5340 recorded litters which resulted from mating of 192 genotyped boars with sows of unknown genotype (dataset 1). An additional 50 litters were produced from parents that were both genotyped (dataset 2). Imputed genotypes of 650K SNPs for 1359 Duroc boars were used in this study. One significant SNP (Bonferroni corrected P = 5.5E-06) was located on SSC14 with 45.3 homozygous individuals expected but none observed. This SNP was significant for mummified fetuses. One hundred fifty two haplotypes were also found to potentially harbor recessive lethal mutations. Twenty-one haplotypes had a significant harmful effect on at least one trait. Two regions, located on SSC8 (144.9–145.5 Mb) and SSC9 (19–19.4 Mb) had significant effects on fertility traits in both datasets. Additionally, regions on SSC1 (82.0–82.8 Mb), SSC3 (73.3–73.7 and 87.1–87.5 Mb) and SSC12 (35.8–36.2 and 50.0–50.5 Mb) had significant deleterious effects on TNB or BA or L24 in dataset 1. Finally, a region on SSC17 (28.7–29.3 Mb) had significant effects on TNB, BA and L24 in dataset 2. A few candidate genes identified within these regions were described as being involved in spermatogenesis and male fertility (TEX14, SEP4, and HSF5), or displayed recessive lethality (CYP26B1, SCD5, and PCF11) in other species. The putative loci detected in this study provide valuable information to potentially increase Duroc litter size by avoiding carrier-by-carrier matings in breeding programs. Further study of the identified candidate genes responsible for such lethal effects may lead to new insights into functions regulating pig fertility

    Variance component estimates, phenotypic characterization, and genetic evaluation of bovine congestive heart failure in commercial feeder cattle

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    The increasing incidence of bovine congestive heart failure (BCHF) in feedlot cattle poses a significant challenge to the beef industry from economic loss, reduced performance, and reduced animal welfare attributed to cardiac insufficiency. Changes to cardiac morphology as well as abnormal pulmonary arterial pressure (PAP) in cattle of mostly Angus ancestry have been recently characterized. However, congestive heart failure affecting cattle late in the feeding period has been an increasing problem and tools are needed for the industry to address the rate of mortality in the feedlot for multiple breeds. At harvest, a population of 32,763 commercial fed cattle were phenotyped for cardiac morphology with associated production data collected from feedlot processing to harvest at a single feedlot and packing plant in the Pacific Northwest. A sub-population of 5,001 individuals were selected for low-pass genotyping to estimate variance components and genetic correlations between heart score and the production traits observed during the feeding period. At harvest, the incidence of a heart score of 4 or 5 in this population was approximately 4.14%, indicating a significant proportion of feeder cattle are at risk of cardiac mortality before harvest. Heart scores were also significantly and positively correlated with the percentage Angus ancestry observed by genomic breed percentage analysis. The heritability of heart score measured as a binary (scores 1 and 2 = 0, scores 4 and 5 = 1) trait was 0.356 in this population, which indicates development of a selection tool to reduce the risk of congestive heart failure as an EPD (expected progeny difference) is feasible. Genetic correlations of heart score with growth traits and feed intake were moderate and positive (0.289–0.460). Genetic correlations between heart score and backfat and marbling score were −0.120 and −0.108, respectively. Significant genetic correlation to traits of high economic importance in existing selection indexes explain the increased rate of congestive heart failure observed over time. These results indicate potential to implement heart score observed at harvest as a phenotype under selection in genetic evaluation in order to reduce feedlot mortality due to cardiac insufficiency and improve overall cardiopulmonary health in feeder cattle

    Genetic Correlations of Reproductive and Maternal Traits with Growth and Carcass Traits in Beef Cattle

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    Some genes may affect more than one trait. Therefore, the traits can be genetically correlated. Knowledge of genetic correlations among traits is useful for efficient selection of replacement bulls and heifers if the breeder considers more than one trait. In designed selection programs, emphasis to be placed on the various traits can depend, in part, on the genetic correlations among them. In addition, genetic correlations can be used to predict what is expected to happen to traits other than those used in selection as a result of that selection. This effect on traits other than those used in selection is referred to as correlated response. The objective of this study was to estimate from experimental data the genetic correlations between reproductive and maternal traits of beef females and growth and carcass traits of paternal half-sib steers. A more detailed account of the methodology and results can be found in the Journal of Animal Science, volume 58, pages 1171 to 1180

    Using Crossbreeding Systems to Produce Beef

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    Crossbreeding provides an opportunity to improve performance by beef cattle. Breed differences are heritable and can be used to produce superior crossbred cattle. Heterosis results from bringing together unlike genes from different breeds to produce an animal with a level of performance that exceeds the average of the parent breeds. We develop crossbreeding systems to make the greatest improvement in performance possible consistent with a sustainable breeding program. Heterosis and differences among breeds are tools of the trade. In this paper, we combine the results from earlier studies to investigate their practical applications

    Development of Terminal and Maternal Economic Selection Indices in Beefmaster Cattle

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    Two economic selection indices were developed for Beefmaster cattle, one for a terminal objective and one for a maternal objective. The terminal index was developed assuming bulls would be mated to mature cows with all resulting progeny harvested. The maternal index was developed assuming bulls would be mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning. Relative economic values for the terminal objective traits hot carcass weight, marbling score, ribeye area, 12th- rib fat and feed intake were 91.29, 17.01, 8.38,- 7.07 and- 29.66, respectively. Relative economic values for the maternal objective traits calving difficultly direct, calving difficulty maternal, weaning weight direct, weaning weight maternal, mature weight and heifer pregnancy were- 2.11,- 1.53, 18.49, 11.28,- 33.46 and 1.19, respectively. The application of economic selection indices facilitates genetic improvement of beef cattle by aiding producers with their sire selection decisions

    Genetic Correlations of Reproductive and Maternal Traits with Growth and Carcass Traits in Beef Cattle

    Get PDF
    Some genes may affect more than one trait. Therefore, the traits can be genetically correlated. Knowledge of genetic correlations among traits is useful for efficient selection of replacement bulls and heifers if the breeder considers more than one trait. In designed selection programs, emphasis to be placed on the various traits can depend, in part, on the genetic correlations among them. In addition, genetic correlations can be used to predict what is expected to happen to traits other than those used in selection as a result of that selection. This effect on traits other than those used in selection is referred to as correlated response. The objective of this study was to estimate from experimental data the genetic correlations between reproductive and maternal traits of beef females and growth and carcass traits of paternal half-sib steers. A more detailed account of the methodology and results can be found in the Journal of Animal Science, volume 58, pages 1171 to 1180

    Management of lethal recessive alleles in beef cattle through the use of mate selection software

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    International audienceAbstractBackgroundRecessive loss-of-function (LOF) alleles at genes which are essential for life, can result in early embryonic mortality. Cattle producers can use the LOF carrier status of individual animals to make selection and mate allocation decisions.MethodsTwo beef cattle breeding strategies i.e. (1) selection against LOF carriers as parents and (2) simultaneous selection and mate allocation to avoid the occurrence of homozygous offspring in three scenarios, which differed in number and frequency of LOF alleles were evaluated using the mate selection program, MateSel. Scenarios included (a) seven loci with high-frequency LOF alleles, (b) 76 loci with low-frequency LOF alleles, and (c) 50 loci with random high- and low-frequency LOF alleles. In addition, any savings resulting from the information obtained by varying the percentage (0–100%) of the herd genotyped, together with segregation analysis to cover ungenotyped animals, were calculated to determine (1) which percentage optimized net profit for a fixed cost of genotyping ($30/test), and (2) the breakeven cost for genotyping.ResultsWith full knowledge of the LOF alleles carried by selection candidates, the most profitable breeding strategy was always simultaneous selection and mate allocation to avoid homozygous affected offspring (aa) as compared to indiscriminate selection against carrier parents (Aa). The breakeven value of genotyping depended on the number of loci modeled, the LOF allele frequencies, and the mating/selection strategies used. Genotyping was most valuable when it was used to avoid otherwise high levels of embryonic mortalities. As the number of essential loci with LOF alleles increased, especially when some were present at relatively high minor allele frequencies, embryonic losses increased, and profit was maximized by genotyping 10 to 20% of a herd and using that information to reduce these losses.ConclusionsGenotyping 100% of the herd was never the most profitable outcome in any scenario; however, genotyping some proportion of the herd, together with segregation analysis to cover ungenotyped animals, maximized overall profit in scenarios with large numbers of loci with LOF alleles. As more LOF alleles are identified, such a mate selection software will likely be required to optimally select and allocate matings to balance the rate of genetic gain, embryonic losses, and inbreeding

    Genetic diversity and population structure among six cattle breeds in South Africa using a whole genome SNP panel

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    Information about genetic diversity and population structure among cattle breeds is essential for genetic improvement, understanding of environmental adaptation as well as utilization and conservation of cattle breeds. This study investigated genetic diversity and the population structure among six cattle breeds in South African (SA) including Afrikaner (n=44), Nguni (n=54), Drakensberger (n=47), Bonsmara (n=44), Angus (n=31) and Holstein (n=29). Genetic diversity within cattle breeds was analyzed using three measures of genetic diversity namely allelic richness (AR), expected heterozygosity (He) and inbreeding coefficient (f). Genetic distances between breed pairs were evaluated using Nei’s genetic distance. Population structure was assessed using model-based clustering (ADMIXTURE). Results of this study revealed that the allelic richness ranged from 1.88 (Afrikaner) to 1.73 (Nguni). Afrikaner cattle had the lowest level of genetic diversity (He=0.24) and the Drakensberger cattle (He=0.30) had the highest level of genetic variation among indigenous and locally-developed cattle breeds. The level of inbreeding was lower across the studied cattle breeds. As expected the average genetic distance was the greatest between indigenous cattle breeds and Bos taurus cattle breeds but the lowest among indigenous and locally-developed breeds. Model-based clustering revealed some level of admixture among indigenous and locally-developed breeds and supported the clustering of the breeds according to their history of origin. The results of this study provided useful insight regarding genetic structure of South African cattle breeds
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