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See detailStrategies to incorporate genomic prediction into population-wide genetic evaluations
Gengler, Nicolas ULiege; VanRaden, P. M.

in Journal of Dairy Science (2008, July), 91

Most current research on genomic selection is focusing on the accurate prediction of genomic breeding values. However selection solely based on genomic breeding values, despite being theoretically ... [more ▼]

Most current research on genomic selection is focusing on the accurate prediction of genomic breeding values. However selection solely based on genomic breeding values, despite being theoretically promising, is in practice only suboptimal for several reasons. The two most important are that only few animals are genotyped therefore having genomic prediction directly available and that rankings will change. With genomic breeding values potentially available in the near future, strategies are required to avoid any confusion in the mind of users. The aim of this study is to present three different strategies that could be used to incorporate genomic prediction into population-wide genetic evaluation. The three strategies are: 1) using selection index theory to combine both sources of information into a single set of breeding values; 2) for ungenotyped animals, compute conditional expectation of gene contents for SNP given molecular and pedigree data and use these predicted gene contents; and 3) integrate genomic breeding values as external information into genetic evaluation using a Bayesian framework. If strategy 1) is straight forward, additional steps have to be done to adjust breeding values for changes in those of relatives. A practical implementation is to use reliabilities of the genomic prediction, the population-wide genetic evaluation PA, and PA from the genotyped subset to set up a 3 x 3 matrix for each animal, with off-diagonal elements being functions of the 3 reliabilities. The use of strategy 2) is computationally much more challenging but leads directly to the needed covariance structures combining genomic relationship if known with pedigree relationships. Strategy 3) is potentially a good compromise because the theory is well established and has already been used in beef cattle to incorporate external breeding values. Also current genetic evaluation software can be easily modified to incorporate genomic breeding values [less ▲]

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See detailGenetic parameters of stearoyl coenzyme-A desaturase 9 activity estimated by test-day model
Arnould, Valérie ULiege; Gengler, Nicolas ULiege; Soyeurt, Hélène ULiege

in Journal of Dairy Science (2008, July), 91(E-Suppl. 2), 542

Dairy and beef products account for a large part of fat intake in human nutrition and therefore can be linked to dietary diseases. The stearoyl Coenzyme-A desaturase 9 (delta-9) gene was identified as a ... [more ▼]

Dairy and beef products account for a large part of fat intake in human nutrition and therefore can be linked to dietary diseases. The stearoyl Coenzyme-A desaturase 9 (delta-9) gene was identified as a potential functional candidate gene affecting milk fat composition in dairy cattle. The objective of this research was to estimate the genetic parameters of delta-9 activity indicator traits and to study the relationship between delta-9 activity as described by these indicator traits and common milk production traits. A total of 126,331 test-day records were obtained from 14,259 Holstein (> 84% Holstein gene) heifers belonging to 105 herds. The studied traits were milk yield, percentages of fat and protein, content of monounsaturated fatty acids, and 3 ratios reflecting the delta-9 activity (C14:1/ C14:0; C16:1/C16:0 and C18:1/C18). The used model was a multiple-trait random regressions test-day model and included as fixed effects: herd x date of test, class of age, and month x year. Random effects were herd x year of calving, permanent environmental, additive genetic, and residual effects. The fatty acid contents were estimated by mid-infrared spectrometry. Delta-9 activity varied within year and lactation. The obtained heritability estimates of delta-9 as well as the genetic and phenotypic correlation varied also through lactation. This study suggests potential improvements of delta-9 activity and subsequently milk fat composition can be achieved by animal management but also by breeding and animal selection. [less ▲]

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See detailGenotype x environment interaction for milk yield in Holsteins using Luxembourg and Tunisian populations.
Hammami, Hedi ULiege; Rekik, Boulbaba; Soyeurt, Hélène ULiege et al

in Journal of Dairy Science (2008), 91(9), 3661-71

Test-day (TD) milk yield records of first-lactation Holstein cows in Luxembourg and Tunisia were analyzed using within-and between-country random regression TD models. Edited data used for within-country ... [more ▼]

Test-day (TD) milk yield records of first-lactation Holstein cows in Luxembourg and Tunisia were analyzed using within-and between-country random regression TD models. Edited data used for within-country analysis included 661,453 and 281,913 TD records in Luxembourg and Tunisia, respectively. The joint data included 730,810 TD records of 87,734 cows and 231 common sires. Both data sets covered calving years 1995 to 2006. Fourth-order Legendre polynomials for random effects and a Gibbs sampling method were used to estimate variance components of lactation curve parameters in separate and joint analyses. Genetic variances of the first 3 coefficients from Luxembourg data were 46 to 69% larger than corresponding estimates from the Tunisian data. Inversely, the Tunisian permanent environment variances for the same coefficients were 52 to 65% larger than the Luxembourg ones. Posterior mean heritabilities of 305-d milk yield and persistency, defined as estimated breeding values (EBV) at 280 days in milk-EBV at 80 days in milk, from between-country analysis were 0.42 and 0.12 and 0.19 and 0.08 in Luxembourg and Tunisia, respectively. Heritability estimates for the same traits from within-country analyses, mainly from the Tunisian data, were lower than those from the joint analysis. Genetic correlations for 305-d milk yield and persistency between countries were 0.60 and 0.36. Product moment and rank correlations between EBV of common sires for 305-d milk yield and persistency from within-country analyses were 0.38 and 0.41 and 0.27 and 0.26, respectively. Differences between genetic variances found in both countries reflect different milk production levels. Moreover, low genetic and rank correlations suggest different ranking of sires in the 2 environments, which implies the existence of a genotype x environment interaction for milk yield in Holsteins. [less ▲]

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See detailShort communication: correlations of marker-assisted breeding values with progeny-test breeding values for eight hundred ninety-nine French Holstein bulls.
Guillaume, François; Fritz, Sébastien; Boichard, Didier et al

in Journal of Dairy Science (2008), 91(6), 2520-2

French artificial insemination companies have been running a marker-assisted selection program since 2001 to determine which young bulls should be progeny tested. A first batch of 899 Holstein sires ... [more ▼]

French artificial insemination companies have been running a marker-assisted selection program since 2001 to determine which young bulls should be progeny tested. A first batch of 899 Holstein sires receiving their first proofs based on progeny daughters has been studied. Estimated breeding values with or without marker information were computed based on information available in April 2004, and correlated to daughter yield deviations available in 2007 for production traits. Marker-assisted estimated breeding values presented greater correlations with daughter yield deviations than those calculated using only pedigree index. The average improvement in correlation was 0.043 and ranged from +0.001 for protein yield to +0.103 for fat percentage. This gain was based on the initial and suboptimal conditions of the program and is expected to increase in the coming years because of several improvements implemented since the start of the marker-assisted selection program. [less ▲]

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See detailGenetic parameters for Tunisian Holsteins using a test-day random regression model.
Hammami, Hedi ULiege; Rekik, Boulbaba; Soyeurt, Hélène ULiege et al

in Journal of Dairy Science (2008), 91(5), 2118-26

Genetic parameters of milk, fat, and protein yields were estimated in the first 3 lactations for registered Tunisian Holsteins. Data included 140,187; 97,404; and 62,221 test-day production records ... [more ▼]

Genetic parameters of milk, fat, and protein yields were estimated in the first 3 lactations for registered Tunisian Holsteins. Data included 140,187; 97,404; and 62,221 test-day production records collected on 22,538; 15,257; and 9,722 first-, second-, and third-parity cows, respectively. Records were of cows calving from 1992 to 2004 in 96 herds. (Co)variance components were estimated by Bayesian methods and a 3-trait-3-lactation random regression model. Gibbs sampling was used to obtain posterior distributions. The model included herd x test date, age x season of calving x stage of lactation [classes of 25 days in milk (DIM)], production sector x stage of lactation (classes of 5 DIM) as fixed effects, and random regression coefficients for additive genetic, permanent environmental, and herd-year of calving effects, which were defined as modified constant, linear, and quadratic Legendre coefficients. Heritability estimates for 305-d milk, fat and protein yields were moderate (0.12 to 0.18) and in the same range of parameters estimated in management systems with low to medium production levels. Heritabilities of test-day milk and protein yields for selected DIM were higher in the middle than at the beginning or the end of lactation. Inversely, heritabilities of fat yield were high at the peripheries of lactation. Genetic correlations among 305-d yield traits ranged from 0.50 to 0.86. The largest genetic correlation was observed between the first and second lactation, potentially due to the limited expression of genetic potential of superior cows in later lactations. Results suggested a lack of adaptation under the local management and climatic conditions. Results should be useful to implement a BLUP evaluation for the Tunisian cow population; however, results also indicated that further research focused on data quality might be needed. [less ▲]

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See detailAccuracy of prediction of gene content in large animal populations and its use for candidate gene detection and genetic evaluation
Gengler, Nicolas ULiege; Abras, S.; Verkenne, C. et al

in Journal of Dairy Science (2008), 91(4), 1652-1659

To estimate and to use the effects of single genes on quantitative traits, genotypes need to be known. However, in large animal populations, the majority of animals are not genotyped. These missing ... [more ▼]

To estimate and to use the effects of single genes on quantitative traits, genotypes need to be known. However, in large animal populations, the majority of animals are not genotyped. These missing genotypes have to be estimated. However, currently used methods are impractical for large pedigrees. An alternative method to estimate missing gene content, defined as the number of copies of a particular allele, was recently developed. In this study, the proposed method was tested by assessing its accuracy in estimation and use of gene content in large animal populations. This was done for the bovine transmembrane growth hormone receptor and its effects on first-lactation milk, fat, and protein test-day yields and somatic cell score in Holstein cows. Estimated gene substitution effects of replacing a copy of the phenylalanine-coding allele with a copy of the tyrosine-coding allele were 295 g/d for milk, -8.14 g/d for fat, -1.83 g/d for protein, and -0.022/d for somatic cell score. However, only the gene substitution effect for milk was found to be significant. The accuracy of the estimated effects was evaluated by simulations and permutations. To validate the use of predicted gene content in a mixed inheritance model, a cross-validation study was done. The model with an additional regression of milk, fat, and protein yields and SCS on predicted gene content showed a better capacity to predict breeding values for milk, fat, and protein. Given these results, the estimation and use of allelic effects using this method proved functional and accurate. [less ▲]

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See detailPregnancy incidence in Norwegian red cows using nonreturn to estrus, rectal palpation, pregnancy-associated glycoproteins, and progesterone.
Garmo, R. T.; Refsdal, A. O.; Karlberg, K. et al

in Journal of Dairy Science (2008), 91(8), 3025-3033

The objectives of the study were to estimate pregnancy incidence and calving rate after first artificial insemination (AI) in Norwegian Red cows undergoing spontaneous estrus, to assess the relationship ... [more ▼]

The objectives of the study were to estimate pregnancy incidence and calving rate after first artificial insemination (AI) in Norwegian Red cows undergoing spontaneous estrus, to assess the relationship between pregnancy and management factors at herd or cow level, to evaluate differences between 60-d nonreturn rate (NRR60d) and pregnancy incidence, and to compare the accuracy of pregnancy diagnosis by rectal palpation and plasma pregnancy-associated glycoproteins (PAG) analysis supported by progesterone measurements. In total, 829 animals (n = 229 heifers, 234 first-lactation, 173 second-lactation, and 193 >second-lactation cows) were included. Milk samples for progesterone analysis were collected both at AI and 3 wk later. Cows with progesterone concentrations <3 ng/mL at AI were considered in estrus or having nonactive ovaries, whereas cows with progesterone concentrations >7 ng/ mL 3 wk later were considered pregnant. Blood sampling for PAG analysis and pregnancy diagnosis by rectal palpation were conducted 57.6 +/- 0.92 d after AI. Pregnancy-associated glycoprotein concentrations equal to 2.5 ng/mL gave the greatest sensitivity (94.3%) and specificity (94.6%) in the assessment of pregnancy. The number of days from calving to first AI was 85.3 +/- 1.71. Overall NRR60d after first AI was 72.5%. The corresponding values for heifers, first-lactation, second-lactation, and >second-lactation cows were 76.9, 67.1, 69.9, and 76.2%. Overall pregnancy incidence after first AI was 63.7%. The corresponding values for heifers, first-lactation, second-lactation, and >second-lactation cows were 70.0, 58.2, 61.6, and 64.9%. Overall calving rate to first AI was 57.2%. The corresponding values for heifers, first-lactation, second-lactation, and >second-lactation cows were 64.9, 54.3, 54.7, and 53.9%. The overall difference between NRR60d and pregnancy incidence was 8.8%, whereas the parity-specific differences were 6.9, 8.9, 8.3, and 11.3% for heifers, first-lactation, second-lactation, and >second-lactation cows, respectively. Eight animals with PAG <2.5 ng/mL and classified as pregnant by rectal palpation calved, whereas 5 animals with PAG >or=2.5 ng/mL and classified as non-pregnant by rectal palpation also calved. The study showed that Norwegian Red cows have relatively high reproductive performance. Breeding for fertility traits over 35 yr is probably an important reason for such high fertility. [less ▲]

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See detailGenetic diversity and joint-pedigree analysis of two importing Holstein populations.
Hammami, Hedi ULiege; Croquet, Coraline; Stoll, Jean et al

in Journal of Dairy Science (2007), 90(7), 3530-3541

Genetic diversity and relatedness between 2 geographically distant Holstein populations (in Luxembourg and Tunisia) were studied by pedigree analysis. These 2 populations have similar sizes and structures ... [more ▼]

Genetic diversity and relatedness between 2 geographically distant Holstein populations (in Luxembourg and Tunisia) were studied by pedigree analysis. These 2 populations have similar sizes and structures and are essentially importing populations. Edited pedigrees included 140,392 and 151,381 animals for Tunisia and Luxembourg, respectively. To partially account for pedigree completeness levels, a modified algorithm was used to compute inbreeding. The effective numbers of ancestors were derived from probabilities of gene origin for the 2 populations of cows born between 1990 and 2000. The 10 ancestors with the highest contributions to genetic diversity in the cow populations accounted for more than 32% of the genes. Eight of these 10 ancestors were the same in both populations. The rates of inbreeding were different in the 2 populations but were generally comparable to those found in the literature for the Holstein breed. Average inbreeding coefficients per year, estimated from the data, ranged from 0.91 and 0.50 in 1990 to 3.10 and 2.12 in 2000 for the Tunisian and Luxembourg populations, respectively. Genetic links have also strengthened with time. Average additive relationships between the 2 populations were as high as 2.2% in 2000. Results suggest that it would be possible to investigate genotype by environment interactions for milk traits using the Tunisian and Luxembourg dairy populations. [less ▲]

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See detailDetection and use of single gene effects in large animal populations
Gengler, Nicolas ULiege; Abras, S.; Szydlowski, M. et al

in Journal of Dairy Science (2007, July), 85/90/86(Suppl. 1/ Suppl. 1/ Suppl. 1), 376

Unbiased estimation of single gene effects can only be achieved by estimating them simultaneously with other environmental and polygenic effects in mixed inheritance models. As in large animal populations ... [more ▼]

Unbiased estimation of single gene effects can only be achieved by estimating them simultaneously with other environmental and polygenic effects in mixed inheritance models. As in large animal populations the vast majority of animals are however not genotyped, missing genotypes have to be estimated. Currently used methods as iterative peeling or MCMC are unpractical for large datasets. Recently an alternative method to estimate missing gene content, dened as the number of copies of a particular allele was developed. Unknown gene content is approximated from known genotypes based on the additive relationships between animals. In this study the proposed method was tested for the detection of candidate gene effects for bovine transmembrane GHR on rst lactation milk, fat and protein test-day yields in Holsteins. The GHR gene was estimated to show moderate to small gene substitution effects of 295 g/day for milk, -8.14 g/day for fat yield and -1.83 g/day for protein yield for a phenylalanine replacement by a tyrosine (frequency 23.3%). Only 961 mostly recent sires out of 2,755,041 animals were genotyped. The accuracy of the procedure was then estimated by doing 15 simulations using gene dropping and adjustment of the observed 12,858,741 records using the estimated parameters. The new method to estimate missing gene content resulted to be functional and accurate as relative bias in the estimation of allele frequency was very low (0.2%) as were the biases for moderate allele substitution effects (milk: 3.7%; fat yield: 3.3%). Biases were larger for traits with smaller substitution effects (protein yield: 55.3%). The new method has the potential to allow even in very large animal population with few genotyped animals reliable estimation and use of moderate to large single gene effects. [less ▲]

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See detailSampling genotype configurations in large complex pedigree
Szydlowski, M.; Gengler, Nicolas ULiege

in Journal of Dairy Science (2007, July), 85/90/86(Suppl. 1/ Suppl. 1/ Suppl. 1), 668

Efcient genotype samplers are needed for Bayesian and maximumlikelihood analysis of complex genetic problems implemented via Markov Chain Monte Carlo (MCMC) algorithms. The examples of such analysis ... [more ▼]

Efcient genotype samplers are needed for Bayesian and maximumlikelihood analysis of complex genetic problems implemented via Markov Chain Monte Carlo (MCMC) algorithms. The examples of such analysis include polygene mapping in complex pedigrees and prediction of total genetic value using genome-wise dense marker maps. For large complex pedigree sampling from desired probability is impossible. We present a simple method to sample genotype congurations for large pedigree from approximate probability. The sampler uses combination of exact (simple peeling) and iterative methods (iterative peeling) to approximate target probability. Two techniques were applied to reduce computational burden: genotype elimination and set-recoding of alleles. The new sampler was evaluated on a large complex pedigree using simulated data sets for various experimental designs and degree of marker polymorphism. The pedigree used in simulation was real bovine pedigree of 907 903 animals born between 1960 and 2005 derived from Belgian dairy and dual-purpose cattle database. Four types of experimental designs were considered: (i) genotyping sires only, (ii) genotyping dams only, (iii) genotyping half of the dams but no sires, and (iv) genotyping half of the sires and half of the dams. For hypothetical single nucleotide polymorphism the new sampler reached 100%, 100%, 44% and 89% of maximum efciency for the four experimental designs respectively. For microsatellite polymorphism the efciency of the sampler reached 100%, 100%, 32% and 76%, respectively. To exemplify the use of the new sampler it was applied to estimate genes shared identical by descent (IBD). The calculation of genes shared IBD among relatives is an important component of gene mapping in complex diseases and quantitative traits. The convergence diagnostic methods gave indirect evidence of irreducibility of the new sampler and showed its good mixing performance. [less ▲]

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See detailPrincipal components approach for estimating heritability of mid-infrared spectrum in bovine milk
Soyeurt, Hélène ULiege; Tsuruta, Shogo; Misztal, Ignacy et al

in Journal of Dairy Science (2007, July), 85/90/86(Suppl. 1/ Suppl. 1/ Suppl. 1), 596-597

Mid-Infrared spectrometry predicts the milk components (e.g., %fat, %protein) from spectral data reecting the milk composition. The data included 9,663 test days on 1,937 cows in 1 to 12 parity recorded ... [more ▼]

Mid-Infrared spectrometry predicts the milk components (e.g., %fat, %protein) from spectral data reecting the milk composition. The data included 9,663 test days on 1,937 cows in 1 to 12 parity recorded from April 2005 to May 2006. Each sample was scanned by MilkoScan FT6000 into 1,060 points. Due to the high dimension, principal components approach (PCA) was done to reduce the traits and indicated that 48 principal components (PC) described 99.02% of information. These PC were analyzed by multi-trait REML using the canonical transformation. This analysis considered 2,850 rst lactation records for 738 cows in 7 breeds from 26 herds. Effects included in the multi-trait model were herd*test date, lactation stage, permanent environmental and animal random effects. The estimates of the variances were back transformed to the initial scales. Heritabilities varied from 0.005% to 57.20% for the different pin numbers. Spectral regions with heritability greater than 5% were located between 1 to 181; 194 to 558 and 709 to 1,060 pin numbers. PCA involving points in those regions demonstrated that only 9 PC explained 99.23% of information. MidInfrared spectrum contains specic regions with substantial genetic information potentially useful for selecting improved milk quality directly on spectral data. [less ▲]

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See detailPrediction of fatty acid contents by mid-infrared spectrometry
Dardenne, P.; Dehareng, F.; Soyeurt, HELENE ULiege et al

in Journal of Dairy Science (2007, July), 85/90/86(Suppl. 1), 274-274

The interest for the dairy products with higher nutritional quality increases. The aim of this research was to elaborate different calibration equations to predict by Mid-Infrared Spectrometry the fatty ... [more ▼]

The interest for the dairy products with higher nutritional quality increases. The aim of this research was to elaborate different calibration equations to predict by Mid-Infrared Spectrometry the fatty acid contents in bovine milk. 1,609 milk samples were collected between March 2005 and May 2006 for 475 cows from 6 dairy breeds (Dual Purpose Belgian Blue, Holstein, Jersey, Montbeliarde, Normande and Red and White) in 8 herds. 78 samples were chosen using Principal Components approach based on spectral variability. All samples were scanned by MilkoScan FT6000. The reference fatty acid concentrations were measured by gas chromatography with a capillary column of 100 m length. The calibration with Partial Least Squares (PLS) on 78 samples showed a ratio of standard error of cross-validation to standard deviation (RPD) ranged between 1.5 and 6.76. The FA present in high concentration in milk were better predicted as in previous studies. In conclusion, the development of this fast method to predict the FA contents and directly integrating in the milk recording structure gives new perspectives for the dairy industry to detect easily and nally improve nutritional quality of their dairy products. [less ▲]

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See detailInvited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions
Negussie, Enyew; de Haas, Yvette; Dehareng, Frédéric et al

in Journal of Dairy Science (2007), 100(4), 2433-2453

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See detailProlactin-induced activation of nuclear factor kappa B in bovine mammary epithelial cells: Role in chronic mastitis
Boutet, Philippe ULiege; Sulon, Joseph ULiege; Closset, R. et al

in Journal of Dairy Science (2007), 90(1), 155-164

We sought to determine whether prolactin (PRL) could influence the neutrophilic inflammation that characterizes chronic mastitis. Most of the genes encoding inflammatory proteins depend on the nuclear ... [more ▼]

We sought to determine whether prolactin (PRL) could influence the neutrophilic inflammation that characterizes chronic mastitis. Most of the genes encoding inflammatory proteins depend on the nuclear factor kappa B (NF-kappa B) for their expression. We addressed the hypothesis that immunomodulatory activities of PRL might arise from an increase in NF-kappa B activity. MAC-T cells, a bovine mammary epithelial cell line, were stimulated with increasing concentrations of bovine PRL ( 1, 5, 25, 125, and 1,000 ng/mL). Level of NF-kappa B binding activity was measured and mRNA was evaluated for IL-1 beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GMCSF), IFN-gamma, and tumor necrosis factor (TNF)-alpha, cytokines known to require NF-kappa B for their maximal transcription. Prolactin activated NF-kappa B; maximal NF-kappa B activation was weaker with PRL than with TNF-alpha at 30 or 180 min poststimulation. In addition, PRL significantly amplified, in a dose-dependent manner, mRNA expression of IL-1 beta, IL-6, IL-8, GMCSF, and TNF-a. We measured PRL concentrations in blood and milk from healthy and chronic mastitis-infected cows, and studied the relationship between the PRL concentration and the degree of inflammation in the mammary gland as indirectly assessed by somatic cell counts (SCC). Plasma PRL did not differ significantly between healthy and chronic mastitis-affected cows (63.7 and 67.5 ng/mL, respectively). Milk PRL concentration was significantly increased in chronic mastitis-affected quarters with the highest SCC, and had a positive significant correlation between SCC, as well as between the number of neutrophils present in milk samples. The present findings show that PRL promotes an inflammatory response in bovine mammary epithelial cells via NF-kappa B activation, and suggest a role for PRL in the pathogenesis of chronic mastitis. [less ▲]

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See detailShort communication: Genetic evaluation of milking speed for brown Swiss dairy cattle in the United States
Wiggans, G. R.; Thornton, L. L. M.; Neitzel, R. R. et al

in Journal of Dairy Science (2007), 90(2), 1021-1023

Genetic parameters and relative breeding values were estimated for milking speed of US Brown Swiss dairy cattle. Owner-recorded milking-speed scores on a scale of 1 (slow) to 8 (fast) were collected by ... [more ▼]

Genetic parameters and relative breeding values were estimated for milking speed of US Brown Swiss dairy cattle. Owner-recorded milking-speed scores on a scale of 1 (slow) to 8 (fast) were collected by the Brown Swiss Association as part of its linear type appraisal program starting in 2004. Data were 7,366 records for 6,666 cows in 393 herds. The pedigree file included information for 21,458 animals born in 1985 or later. Six unknown-parent groups that each included 4 birth years were defined. The model included fixed effects for herd appraisal date and parity-lactation stage and random effects for permanent environment, animal, and error. Within parity (1, 2, and >= 3), 6 groups were defined: unknown calving date, four 90-d lactation stages, and lactations with > 400 d in milk. Heritability of 0.22 and repeatability of 0.42 were estimated by average-information REML; residual variance was 1.13. Little trend in estimated breeding value was found for cows born from 1999 through 2002. Although solutions increased with lactation stage for first-parity cows by 0.37, no clear trend was found for later parities. Genetic evaluations for milking speed were expressed as relative breeding values with a mean of 100 and a standard deviation of 5. The 121 bulls with >= 10 daughters had milking speed evaluations that ranged from 83 to 112 and had correlations of 0.56 with productive life evaluations and -0.40 with somatic cell score evaluations. The association of faster milking speed with lower somatic cell score was not expected. The moderate heritability found for milking speed indicates that the evaluations (first released in May 2006) should be useful in detecting bulls with slow-milking daughters. [less ▲]

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See detailGenetic variability of lactoferrin content estimated by mid-infrared spectrometry in bovine milk
Soyeurt, Hélène ULiege; Colinet, Frédéric ULiege; Arnould, Valérie ULiege et al

in Journal of Dairy Science (2007), 90(9), 4443-4450

The effects of lactoferrin (LF) on the immune system have already been shown by many studies. Unfortunately, the current methods used to measure LF levels in milk do not permit the study of the genetic ... [more ▼]

The effects of lactoferrin (LF) on the immune system have already been shown by many studies. Unfortunately, the current methods used to measure LF levels in milk do not permit the study of the genetic variability of lactoferrin or the performance of routine genetic evaluations. The first aim of this research was to derive a calibration equation permitting the prediction of LF in milk by mid-infrared spectrometry (MIR). The calibration with partial least squares on 69 samples showed a ratio of standard error of cross-validation to standard deviation equal to 1.98. Based on this value, the calibration equation was used to establish an LF indicator trait (predicted LF; pLF) on a large number of milk samples (n = 7,690). A subsequent study of its variability was conducted, which confirmed that stage of lactation and lactation number influence the overall pLF level. Small differences in mean pLF among 7 dairy breeds were also observed. The pLF content of Jersey milk was significantly higher than that in Holstein milk. Therefore, the choice of breed could change the expected LF level. Heritability estimated for pLF was 19.7%. The genetic and phenotypic correlations between somatic cell score and pLF were 0.04 and 0.26, respectively. As somatic cell score increases in presence of mastitis, this observation seems to indicate that pLF, or a function of observed pLF, compared with expected LF might have potential as an indicator of mastitis. The negative genetic correlation (−0.36) between milk yield and pLF could indicate an undesirable effect of selection for high milk production on the overall LF level. [less ▲]

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See detailCharacterization of the DGAT1 K232A and variable number of tandem repeat polymorphisms in French dairy cattle.
Gautier, M.; Capitan, A.; Fritz, S. et al

in Journal of Dairy Science (2007), 90(6), 2980-8

A quantitative trait locus (QTL) underlying different milk production traits has been identified with a high significance threshold value in the genomic region containing the acylCoA:diacylglycerol ... [more ▼]

A quantitative trait locus (QTL) underlying different milk production traits has been identified with a high significance threshold value in the genomic region containing the acylCoA:diacylglycerol acyltransferase (DGAT1) gene, in the 3 main French dairy cattle breeds: French Holstein, Normande, and Montbeliarde. Previous studies have confirmed that the K232A polymorphism in DGAT1 is responsible for a major QTL underlying several milk production traits in Holstein dairy cattle and several other bovine breeds. In this study, we estimate the frequency of the 2 alternative alleles, K and A, of the K232A polymorphism in French Holstein, Normande, and Montbeliarde breeds. Although the K allele segregates in French Holstein and Normande breeds with a similar effect on production traits, the existence of additional mutations contributing to the observed QTL effect is strongly suggested in both breeds by the existence of sires heterozygous at the QTL but homozygous at the K232A polymorphism. One allele at a variable number of tandem repeats (VNTR) locus in the 5' noncoding region of DGAT1 has been recently proposed as a putative causative variant. In our study, this marker was found to present a high mutation rate of 0.8% per gamete and per generation, making the allele diversity observed compatible with that expected under neutrality. Moreover, among the sires homozygous at the K232A polymorphism, no allele at the VNTR can fully explain their QTL status. Finally, no allele at the VNTR was found to be significantly associated with the fat percentage variation in the 3 breeds simultaneously after correction for the effect of the K232A polymorphism. Therefore, our results suggest the existence of at least one other causative polymorphism not yet described. Because the A allele is nearly fixed in the Montbeliarde breed, this breed represents an interesting model to identify and confirm other mutations that have a strong effect on milk production traits. [less ▲]

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See detailEstimation of heritability and genetic correlations for the major fatty acids in bovine milk
Soyeurt, Hélène ULiege; Gillon, Alain ULiege; Vanderick, Sylvie ULiege et al

in Journal of Dairy Science (2007), 90(9), 4435-4442

The current cattle selection program for dairy cattle in the Walloon region of Belgium does not consider the relative content of the different fatty acids (FA) in milk. However, interest by the local ... [more ▼]

The current cattle selection program for dairy cattle in the Walloon region of Belgium does not consider the relative content of the different fatty acids (FA) in milk. However, interest by the local dairy industry in differentiated milk products is increasing. Therefore, farmers may be interested in selecting their animals based on the fat composition. The aim of this study was to evaluate the feasibility of genetic selection to improve the nutritional quality of bovine milk fat. The heritabilities and correlations among milk yield, fat, protein, and major FA contents in milk were estimated. Heritabilities for FA in milk and fat ranged from 5 to 38%. The genetic correlations estimated among FA reflected the common origin of several groups of FA. Given these results, an index including FA contents with the similar metabolic process of production in the mammary gland could be used, for example, to increase the monounsaturated and conjugated fatty acids in milk. Moreover, the genetic correlations between the percentage of fat and the content of C14:0, C12:0, C16:0, and C18:0 in fat were −0.06, 0.55, 0.60, and 0.84, respectively. This result demonstrates that an increase in fat content is not directly correlated with undesirable changes in FA profile in milk for human health. Based on the obtained genetic parameters, a future selection program to improve the FA composition of milk fat could be initiated. [less ▲]

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See detailFirst steps to model milk urea in a management perspective
Bastin, Catherine ULiege; Gillon, Alain ULiege; Gengler, Nicolas ULiege

in Journal of Dairy Science (2007), 90 - Suppl 1

Detailed reference viewed: 51 (10 ULiège)
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See detailLinear and curvilinear effects of inbreeding on production traits for walloon Holstein cows
Croquet, Coraline; Mayeres, Patrick; Gillon, Alain ULiege et al

in Journal of Dairy Science (2007), 90(1), 465-471

The nonlinear effects of inbreeding were studied by comparing linear and curvilinear regression models of phenotypic performances on inbreeding coefficients for production traits (milk, fat, and protein ... [more ▼]

The nonlinear effects of inbreeding were studied by comparing linear and curvilinear regression models of phenotypic performances on inbreeding coefficients for production traits (milk, fat, and protein yields) of Holstein cows in their first lactation. Three different regression models (linear, quadratic, and cubic) were introduced separately into a single-trait, single-lactation, random regression test-day model. The significance of the different regression coefficients was studied based on a t-test after estimation of error variances and covariances associated with the different regression coefficients. All of the tested regression coefficients were significantly different from 0. The traditional regression coefficients of milk, fat, and protein yields on inbreeding were, respectively, -22.10, -1.10, and -0.72 kg for Holstein cows in their first lactation. However, the estimates of 305-d production losses for various classes of animals based on inbreeding coefficients showed that the effect of inbreeding was not a linear function of the percentage of inbreeding. The 305-d milk yield loss profiles attributable to inbreeding, obtained by the various regression models, were different. However, for inbreeding coefficients between 0 and 10%, these differences were small. [less ▲]

Detailed reference viewed: 88 (19 ULiège)