References of "Gengler, Nicolas"
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See detailIs there value in maintaining small populations ? Example of the Dual-Purpose Belgian Blue breed.
Gengler, Nicolas ULg; Soyeurt, Hélène ULg; Bastin, Catherine ULg et al

Conference (2011, July 13)

Current status of thinking on genomic selection in dairy cattle is mostly major breed centric (e.g., Holstein) and only for traditional traits (e.g., milk yields). Once you depart from this, it becomes ... [more ▼]

Current status of thinking on genomic selection in dairy cattle is mostly major breed centric (e.g., Holstein) and only for traditional traits (e.g., milk yields). Once you depart from this, it becomes obvious that different, often related, issues appear (e.g., lack of large training populations, need for expensive recording of new phenotypes). Also, there is an urgent need to rethink issues that are important for sustainability of dairy production (e.g., added value foods, animal robustness). In this context, small populations (breeds/lines) could represent a potential source of extra information to justify their maintenance. As marker densities increase, efficient dissection of different selection histories of divergent breeds or lines, potentially identifying pockets of unexploited variability will increase. A current example from the Belgian (Walloon) perspective is the Dual Purpose (DP) line of the Belgian Blue Breed (BBB), with presently around 4500 breeding females, for historical reason of which only 1500 have good pedigrees, and which is present in Belgium and northern France. Recent research, done on this line, showed its tendency to produce less saturated milk fat and to have better fertility. Results indicated that it could stay competitive in specific markets, especially because of largely increased meat value. Currently, the myostatin mutation is largely used for breeding purposes. To assess the genetic diversity of the breed, recently, over 200 genotypes (SNP50K) for nearly all breeding bulls of the last 20 years became available. HD genotypes should be available in the near future, also allowing to access selection history of this breed as being in between the 2 extreme breeds: Beef BBB (with which it shares a recent history) and Holstein-Friesian (which is related through its geographic proximity over centuries). Finally, genomic selection for DP-BBB will need to consider a single step type approach without the need of reference population and potentially relying heavily on SNP3K of cows, also with the objective to recreate relationships between animals of interest. [less ▲]

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See detailA recursive method of approximation of the inverse of genomic relationships matrix
Faux, Pierre ULg; Gengler, Nicolas ULg; Misztal, Ignacy

Conference (2011, July 11)

Genomic evaluations by some procedures such as genomic BLUP (GBLUP) or single-step GBLUP (ssGBLUP) use the inverse of the genomic relationship matrix (G). The cost to create such an inverse is cubic and ... [more ▼]

Genomic evaluations by some procedures such as genomic BLUP (GBLUP) or single-step GBLUP (ssGBLUP) use the inverse of the genomic relationship matrix (G). The cost to create such an inverse is cubic and becomes prohibitively expensive after 30–100k genotypes. The purpose of this study was to develop methodologies, which eventually could compute a good approximation of G−1 at reduced cost. A recursive approximation of the inverse is based on a decomposition similar to that for the pedigree-based relationship: G−1 = (T−1)’D−1T−1, where T is a triangular and D a diagonal matrix. In the first step, animals are processed from the oldest to the youngest. For each animal, a subset of ancestors is selected with coefficients of genomic relationship to that animal greater than a threshold. A system of equations is created where the coefficients of G for the selected ancestors are in the left hand side and the coefficients of G for the given animal corresponding to the ancestors are the right hand side. The solution to that system of equation is stored in one line of T. Then, D is computed as diagonal elements of T−1G(T−1)’. If off-diagonals of D are too large, the approximation to G can be improved by repeated applications of G−1 = (T−1)’D−1T−1 and D = T−1G(T−1)’. After n rounds, the approximation of G inverse is a product of 2n triangular matrices and one diagonal matrix. This recursive method has been assessed on a sample of 1,718 genotyped dairy bulls. The correlation between GEBV using the complete or approximated G were 0.54 in the first round, 0.96 in the second, and 0.99 in the third. The cost of the proposed method depends on the population structure. It is likely to be high for closely related animals but lower for populations where few animals are strongly related. Additional research is needed to identify near-sparsity in T and D to eliminate unimportant operations. [less ▲]

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See detailEstimating daily yield and content of major fatty acids from single milking: First approach
Arnould, Valérie ULg; Froidmont, Eric; Nguyen, Nam et al

Poster (2011, July 11)

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See detailA recursive method of approximation of the inverse of genomic relationship matrix
Faux, Pierre ULg; Misztal, Ignacy; Gengler, Nicolas ULg

Conference (2011, July 11)

Approximation of the inverse of the genomic relationship matrix is obtained by a similar algorithm to that of the pedigree-based relationship matrix. A recursive use of this algorithm returns a better ... [more ▼]

Approximation of the inverse of the genomic relationship matrix is obtained by a similar algorithm to that of the pedigree-based relationship matrix. A recursive use of this algorithm returns a better approximation of the inverse after each round of recursion, until it reaches the real inverse. [less ▲]

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See detailEstimating daily yield of major fatty acids from single milking: first approach.
Arnould, Valérie ULg; NGuyen, N. H.; Froidmont et al

in Journal of Dairy Science (2011, July), 94(E-Suppl. 1), 29

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of milk recording. However, this solution leads to decrease also the ... [more ▼]

Reducing the frequency of milk recording and the number of recorded samples per test-day could be a solution in order to reduce costs of milk recording. However, this solution leads to decrease also the accuracy of predicting daily yield. According to the literature, several authors have already worked on this problematic. Unfortunately, some effects used in previous studies are not often available or reliable in used databases. This study was aimed to enlarge these investigations to milk fatty acids (FA) production: saturated FA, mono-unsaturated FA, unsaturated FA, medium-chain FA, and long chain FA and to propose a simple, robust and practical method for estimating accurate daily major FA yield from single milking. To do this, five dairy cows were followed between January 2007 and December 2010. FA contents were predicted by mid-infrared spectrometry. The final database contained 1,440 records. The first step was to ensure that used effects were available in most used databases. According to the availability of data, height models were tested to estimate daily yields from both morning and evening milking. These models were compared on the basis of the coefficient of determination values between estimated and observed daily yields and the mean square error. The proposed models included progressively several effects such as the milk yield, the fat and protein content, some classes of stage in lactation, of month of test or of month of calving. As expected, R² values were higher when these effects are introduced in the model and were comprised between 0.87 and 0.88 when daily yield were estimated from morning milking, and from 0.75 and 0.86 when daily yield were estimated from evening milking. It was concluded that the introduction of these effects did highly improve the daily predictability of all trait yield and can partially replace the milking interval effect. It was also observed that daily yields estimated from evening milkings are less accurate than those estimated from morning milkings. Finally, the applied model will depend on the availability of the data and to the convenience of the applied model to the studied population. Keywords: Milk recording, Fatty acids, prediction [less ▲]

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See detailEuropean TMI estimation
Vanderick, Sylvie ULg; Faux, Pierre ULg; Gengler, Nicolas ULg

Conference given outside the academic context (2011)

Total Merit Indexes (TMI) of 6 national evaluations (France, Germany, Walloon Region of Belgium, Italy, Netherlands and Nordic countries) were available. A principal component analysis was performed on ... [more ▼]

Total Merit Indexes (TMI) of 6 national evaluations (France, Germany, Walloon Region of Belgium, Italy, Netherlands and Nordic countries) were available. A principal component analysis was performed on this data in order to assess the common direction of selection between those 6 countries. Results showed that this methodology was a good basis to define a common european TMI. [less ▲]

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See detailMid-infrared prediction of bovine milk fatty acids across multiple breeds, production systems, and countries
Soyeurt, Hélène ULg; Dehareng, ; Gengler, Nicolas ULg et al

in Journal of Dairy Science (2011), 94

Increasing consumer concern exists over the relationship between food composition and human health. Because of the known effects of fatty acids on human health, the development of a quick, inexpensive ... [more ▼]

Increasing consumer concern exists over the relationship between food composition and human health. Because of the known effects of fatty acids on human health, the development of a quick, inexpensive, and accurate method to directly quantify the fatty acid (FA) composition in milk would be valuable for milk processors to develop a payment system for milk pertinent to their customer requirements and for farmers to adapt their feeding systems and breeding strategies accordingly. The aim of this study was (1) to confirm the ability of mid-infrared spectrometry (MIR) to quantify individual FA content in milk by using an innovative procedure of sampling (i.e., samples were collected from cows belonging to different breeds, different countries, and in different production systems); (2) to compare 6 mathematical methods to develop robust calibration equations for predicting the contents of individual FA in milk; and (3) to test interest in using the FA equations developed in milk as basis to predict FA content in fat without corrections for the slope and the bias of the developed equations. In total, 517 samples selected based on their spectral variability in 3 countries (Belgium, Ireland, and United Kingdom) from various breeds, cows, and production systems were analyzed by gas chromatography (GC). The samples presenting the largest spectral variability were used to calibrate the prediction of FA by MIR. The remaining samples were used to externally validate the 28 FA equations developed. The 6 methods were (1) partial least squares regression (PLS); (2) PLS + repeatability file (REP); (3) first derivative of spectral data + PLS; (4) first derivative + REP + PLS; (5) second derivative of spectral data + PLS; and (6) second derivative + REP + PLS. Methods were compared on the basis of the crossvalidation coefficient of determination (R2cv), the ratio of standard deviation of GC values to the standard error of cross-validation (RPD), and the validation coefficient of determination (R2v). The third and fourth methods had, on average, the highest R2cv, RPD, and R2v. The final equations were built using all GC and the best accuracy was observed for the infrared predictions of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, C18:1 trans, C18:1 cis-9, C18:1 cis, and for some groups of FA studied in milk (saturated, monounsaturated, unsaturated, short-chain, medium-chain, and long-chain FA). These equations showed R2cv greater than 0.95. With R2cv equal to 0.85, the MIR prediction of polyunsaturated FA could be used to screen the cow population. As previously published, infrared predictions of FA in fat are less accurate than those developed from FA content in milk (g/dL of milk) and no better results were obtained by using milk FA predictions if no corrections for bias and slope based on reference milk samples with known contents of FA were used. These results indicate the usefulness of equations with R2cv greater than 95% in milk payment systems and the usefulness of equations with R2cv greater than 75% for animal breeding purposes. [less ▲]

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See detailRobustMilk - Développer des outils de sélection pratiques et innovants pour la production de produits laitiers de qualité issus de vaches plus robustes : Sélectionner sur le profil en acides gras du lait
Bastin, Catherine ULg; Gengler, Nicolas ULg; Soyeurt, Hélène ULg

in 16ième Carrefour des productions animales: La Filière laitière bovine est-elle durable?, Gembloux, le 2 mars 2011 (2011, March 02)

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See detailEstimation de la quantité journalière grasse du lait à partir d'une seule traite (matin ou soir) des composés fins de la matière grasse du lait
Arnould, Valérie ULg; Froidmont, Eric; Nguyen, Nam et al

in 16ième Carrefour des Productions animales: la filière laitière bovine européenne est-elle durable? (2011, March 02)

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See detailManageMilk - Création d'outils de management innovatifs et pratiques en vue d'améliorer la durabilité de la production laitière et de la qualité des produits laitiers: présentation du projet.
Arnould, Valérie ULg; Soyeurt, Hélène ULg; Stoll, Jean et al

in 16ième Carrefour des Prodcutions animales: La filière laitière bovine européenne est-elle durable? (2011, March 02)

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See detailConservation et valorisation de la Bleue Mixte au travers du projet franco-belge BlueSel
Colinet, Frédéric ULg; Glorieux, Géry; Beguin, Emmanuel et al

Poster (2011, March)

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See detailConservation et valorisation de la Bleue Mixte au travers du projet franco-belge BlueSel
Colinet, Frédéric ULg; Glorieux, Géry; Beguin, Emmanuel et al

in 16ième Carrefour des Productions animales: La filière laitière bovine européenne est-elle durable? (2011, March)

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See detailVariabilité et amélioration des aptitudes à la transformation fermière du lait au travers du projet ProFARMilk
Colinet, Frédéric ULg; Sindic, Marianne ULg; Anceau, Christine ULg et al

in 16ième Carrefour des Productions animales: La filière laitière bovine européenne est-elle durable? (2011, March)

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