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See detailPotential estimation of major mineral contents in cow milk using mid-infrared spectrometry.
Soyeurt, Hélène ULg; Bruwier, Damien; Romnee, Jean-Michel et al

in Journal of Dairy Science (2009), 92(6), 2444-2454

Milk and dairy products are a major source of minerals, particularly calcium, involved in several metabolic functions in humans. Currently, several dairy products are enriched with calcium to prevent ... [more ▼]

Milk and dairy products are a major source of minerals, particularly calcium, involved in several metabolic functions in humans. Currently, several dairy products are enriched with calcium to prevent osteoporosis. The development of an inexpensive and fast quantitative analysis for minerals is required to offer dairy farmers an opportunity to improve the added value of the produced milk. The aim of this study was to develop 5 equations to measure Ca, K, Mg, Na, and P contents directly in bovine milk using mid-infrared (MIR) spectrometry. A total of 1,543 milk samples were collected between March 2005 and May 2006 from 478 cows during the Walloon milk recording and analyzed by MIR spectrometry. Using a principal component approach, 62 milk samples were selected by their spectral variability and separated in 2 calibration sets. Five outliers were detected and deleted. The mineral contents of the selected samples were measured by inductively coupled plasma atomic emission spectrometry. Using partial least squares combined with a repeatability file, 5 calibration equations were built to estimate the contents of Ca, K, Mg, Na, and P in milk. To assess the accuracy of the developed equations, a full cross-validation and an external validation were performed. The cross-validation coefficients of determination (R(2)cv) were 0.80, 0.70, and 0.79 for Ca, Na, and P, respectively (n = 57), and 0.23 and 0.50 for K and Mg, respectively (n = 31). Only Ca, Na, and P equations showed sufficient R(2)cv for a potential application. These equations were validated using 30 new milk samples. The validation coefficients of determination were 0.97, 0.14, and 0.88 for Ca, Na, and P, respectively, suggesting the potential to use the Ca and P calibration equations. The last 30 samples were added to the initial milk samples and the calibration equations were rebuilt. The R(2)cv for Ca, K, Mg, Na, and P were 0.87, 0.36, 0.65, 0.65, and 0.85, respectively, confirming the potential utilization of the Ca and P equations. Even if new samples should be added in the calibration set, the first results of this study showed the feasibility to quantify the calcium and phosphorus directly in bovine milk using MIR spectrometry. [less ▲]

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See detailModeling milk urea of Walloon dairy cows in management perspectives.
Bastin, Catherine ULg; Laloux, Laurent; Gillon, Alain ULg et al

in Journal of Dairy Science (2009), 92(7), 3529-40

The aim of this study was to develop an adapted random regression test-day model for milk urea (MU) and to study the possibility of using predictions and solutions given by the model for management ... [more ▼]

The aim of this study was to develop an adapted random regression test-day model for milk urea (MU) and to study the possibility of using predictions and solutions given by the model for management purposes. Data included 607,416 MU test-day records of first-lactation cows from 632 dairy herds in the Walloon Region of Belgium. Several advanced features were used. First, to detect the herd influence, the classical herd x test-day effect was split into 3 new effects: a fixed herd x year effect, a fixed herd x month-period effect, and a random herd test-day effect. A fixed time period regression was added in the model to take into account the yearly oscillations of MU on a population scale. Moreover, first autoregressive processes were introduced and allowed us to consider the link between successive test-day records. The variance component estimation indicated that large variance was associated with the random herd x test-day effect (48% of the total variance), suggesting the strong influence of herd management on the MU level. The heritability estimate was 0.13. By comparing observed and predicted MU levels at both the individual and herd levels, target ranges for MU concentrations were defined to take into account features of each cow and each herd. At the cow level, an MU record was considered as deviant if it was <200 or >400 mg/L (target range used in the field) and if the prediction error was >50 mg/L (indicating a significant deviation from the expected level). Approximately 7.5% of the MU records collected between June 2007 and May 2008 were beyond these thresholds. This combination allowed for the detection of potentially suspicious cows. At the herd level, the expected MU level was considered as the sum of the solutions for specific herd effects. A herd was considered as deviant from its target range when the prediction error was greater than the standard deviation of MU averaged by herd test day. Results showed that 6.7% of the herd test-day MU levels between June 2007 and May 2008 were considered deviant. These deviations seemed to occur more often during the grazing period. Although theoretical considerations developed in this study should be validated in the field, this research showed the potential use of a test-day model for analyzing functional traits to advise dairy farmers. [less ▲]

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See detailDetection and Correction of Outliers for Fatty Acids Contents Measured by Mid-Infrared Spectrometry Using Random Regression Test-Day Models
Soyeurt, Hélène ULg; Dardenne, Pierre; Gengler, Nicolas ULg

in Book of Abstracts of the 60th Annual Meeting of the European Association for Animal Production (2009)

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See detailGenetic variability of test-day stearoyl coenzyme-A desaturase 9 activity
Arnould, Valérie ULg; Gengler, Nicolas ULg; Soyeurt, Hélène ULg

in Journal of Dairy Science (2009), 92(E-suppl.1), 353-354

Milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. Different natural sources of variation such as feeding or genetics could be used to modify the contents of ... [more ▼]

Milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. Different natural sources of variation such as feeding or genetics could be used to modify the contents of unsaturated fatty acids. The impact of feeding is well described; however, genetics effects on the milk FA composition are not well studied. Increasing the unsaturated fatty acids contents of bovine milk could have the potential to raise the nutritive and therapeutic values of dairy products. 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 study the genetic variability on this enzyme activity across lactations. A total of 199,977 test-day records were obtained from 29,603 Holstein cows in first lactation, 154,267 records from 23,453 Holstein cows in second lactation, and 173,244 records from 75,887 Holstein cows in third and later lactations. The used model was a multiple-trait random regressions test-day model. Fixed effects were: herd × date of test, and class of age. Random effects were: herd × year of calving, permanent environmental, additive genetic, and residual effects. The studied traits were milk yield, protein content, percentage of fat, monounsaturated fatty acids estimated by mid-infrared spectrometry, and the ratios reflecting the delta-9 activity. Obtained heritability estimates of delta-9 as well as the genetic and phenotypic correlations varied across lactations. These results suggest potential improvements of milk fat composition based on delta-9 activity using animal selection and appropriate management practices. [less ▲]

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See detailGenetic analysis of lactoferrin content in bovine milk
Arnould, Valérie ULg; Soyeurt, Hélène ULg; Gengler, Nicolas ULg et al

in Journal of Dairy Science (2009), 92(5), 2151-2158

Bovine lactoferrin (LF) is mainly present in milk and shows important physiological and biological functions. The aim of this study was to estimate the heritability and correlation values of LF content in ... [more ▼]

Bovine lactoferrin (LF) is mainly present in milk and shows important physiological and biological functions. The aim of this study was to estimate the heritability and correlation values of LF content in bovine milk with different economic traits as milk yield (MY), fat and protein percentages, and somatic cell score (SCS). Variance components of the studied traits were estimated by REML using a multiple-trait mixed model. The obtained heritability (0.22) for LF content predicted using mid-infrared spectrometry (pLF) suggested the possibility of animal selection based on the increase of LF content in milk. The phenotypic and genetic correlation values calculated between pLF and SCS were moderate (0.31 and 0.24, respectively). Furthermore, a preliminary study of bovine LF gene polymorphism effects was performed on the same production traits. By PCR, all exons of the LF gene were amplified and then sequenced. Three new polymorphisms were detected in exon 2, exon 11, and intron 8. We examined the effects of LF gene polymorphisms of exons 2, 4, 9, 11, and 15, and intron 8 on pLF, MY, fat and protein percentages, and SCS. The different observed effects did not reach a significant level probably because of the characteristics of the studied population. However, the results were promising, and LF may be a potential indicator of mastitis. Further studies are necessary to evaluate the effect of genetic selection based on LF content on the improvement of mastitis resistance. [less ▲]

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See detailVariability of major fatty acid contents in Luxembourg dairy cattle
Soyeurt, Hélène ULg; Arnould, Valérie ULg; Dardenne, Pierre et al

in Book of Abstracts of the 60th Annual Meeting of the European Association for Animal Production (2009)

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See detailEnvironmental sensitivity for milk yield in Luxembourg and Tunisian Holsteins by herd management level.
Hammami, Hedi ULg; Rekik, Boulbaba; Bastin, Catherine ULg et al

in Journal of Dairy Science (2009), 92(9), 4604-12

Milk production data of Luxembourg and Tunisian Holstein cows were analyzed using herd management (HM) level. Herds in each country were clustered into high, medium, and low HM levels based on solutions ... [more ▼]

Milk production data of Luxembourg and Tunisian Holstein cows were analyzed using herd management (HM) level. Herds in each country were clustered into high, medium, and low HM levels based on solutions of herd-test-date and herd-year of calving effects from national evaluations. Data from both populations included 730,810 test-day (TD) milk yield records from 87,734 first-lactation cows. A multi-trait, random regression TD model was used to estimate (co)variance components for milk yield within and across country HM levels. Additive genetic and permanent environmental variances of TD milk yields varied with management level in Tunisia and Luxembourg. Additive variances were smaller across HM levels in Tunisia than in Luxembourg, whereas permanent environmental variances were larger in Tunisian HM levels. Highest heritability estimates of 305-d milk yield (0.41 and 0.21) were found in high HM levels, whereas lowest estimates (0.31 and 0.12, respectively) were associated with low HM levels in both countries. Genetic correlations among Luxembourg HM levels were >0.96, whereas those among Tunisian HM levels were below 0.80. Respective rank orders of sires ranged from 0.73 to 0.83 across Luxembourg environments and from 0.33 to 0.42 across Tunisian HM levels indicating high re-ranking of sires in Tunisia and only a scaling effect in Luxembourg. Across-country environment analysis showed that estimates of genetic variance in the high, medium, and low classes of Tunisian environments were 45, 69, and 81% lower, respectively, than the estimate found in the high Luxembourg HM level. Genetic correlations among 305-d milk yields in Tunisian and Luxembourg HM environments ranged from 0.39 to 0.79. The largest estimated genetic correlation was found between the medium Luxembourg and high Tunisian HM levels. Rank correlations for common sires' estimated breeding values among HM environments were low and ranged from 0.19 to 0.39, implying the existence of genotype by environment interaction. These results indicate that daughters of superior sires in Luxembourg have their genetic expression for milk production limited under Tunisian environments. Milk production of cows in the medium and low Luxembourg environments were good predictors of that of their paternal half-sisters in the high Tunisian HM level. Breeding decisions in low-input Tunisian environment should utilize semen from sires with daughters in similar production environments rather than semen of bulls proven in higher management levels. [less ▲]

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See detailRobustmilk - Du lait plus sain à partir de vaches plus saines
Soyeurt, Hélène ULg

Article for general public (2009)

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See detailAccessing genotype by environment interaction using within- and across-country test-day random regression sire models
Hammami, Hedi ULg; Rekik, Boulbaba; Soyeurt, Hélène ULg et al

in Journal of Animal Breeding & Genetics (2009), 126(5), 366-377

First-lactation test-day (TD) milk records of Luxembourg and Tunisian Holsteins were analysed for evidence of genotype by environment interaction (G · E). The joint data included 730 810 TD records of 87 ... [more ▼]

First-lactation test-day (TD) milk records of Luxembourg and Tunisian Holsteins were analysed for evidence of genotype by environment interaction (G · E). The joint data included 730 810 TD records of 87 734 cows and 231 common sires. Random regression TD sire models with fourth-order Legendre polynomials were used to estimate genetic parameters via within- and across-country analyses. Daily heritability estimates of milk yield from within-country analysis were between 0.11 and 0.32, and 0.03 and 0.13 in Luxembourg and Tunisia, respectively. Heritability estimates for 305-day milk yield and persistency (defined as the breeding value for milk yield on DIM 280 minus the breeding value on DIM 80) were lower for Tunisian Holsteins compared with the Luxembourg population. Specifically, heritability for 305-day milk yield was 0.16 for within- and 0.11 for across-country analyses for Tunisian Holsteins and 0.38 for within- and 0.40 for across-country analyses for Luxembourg Holsteins. Heritability for apparent persistency was 0.02 for both within and across-country analyses for Tunisian Holsteins and 0.08 for within and 0.09 for across-country analyses for Luxembourg Holsteins. Genetic correlations between the two countries were 0.50 for 305-day milk yield and 0.43 for apparent persistency. Moreover, rank correlations between the estimated breeding values of common sires for 305-day milk yield and persistency, estimated separately in each country, were low. Low genetic correlations are evidence for G · E for milk yield production while low rank correlations suggest different rankings of sires in both environments. Results from this study indicate that milk production of daughters of the same sires depends greatly on the production environment and that importing high merit semen for limited input systems might not be an effective strategy to improve milk production. [less ▲]

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See detailGenetic variability of milk fatty acids.
Arnould, Valérie ULg; Soyeurt, Hélène ULg

in Journal of Applied Genetics (2009), 50(1), 29-39

The milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. The natural sources of variation, such as feeding or genetics, could be used to increase the ... [more ▼]

The milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. The natural sources of variation, such as feeding or genetics, could be used to increase the concentrations of unsaturated fatty acids. The impact of feeding is well described. However, genetic effects on the milk FA composition begin to be extensively studied. This paper summarizes the available information about the genetic variability of FAs. The greatest breed differences in FA composition are observed between Holstein and Jersey milk. Milk fat of the latter breed contains higher concentrations of saturated FAs, especially short-chain FAs. The variation of the delta-9 desaturase activity estimated from specific FA ratios could explain partly these breed differences. The choice of a specific breed seems to be a possibility to improve the nutritional quality of milk fat. Generally, the proportions of FAs in milk are more heritable than the proportions of these same FAs in fat. Heritability estimates range from 0.00 to 0.54. The presence of some single nucleotide polymorphisms could explain partly the observed individual genetic variability. The polymorphisms detected on SCD1 and DGAT1 genes influence the milk FA composition. The SCD1 V allele increases the unsaturation of C16 and C18. The DGAT1 A allele is related to the unsaturation of C18. So, a combination of the molecular and quantitative approaches should be used to develop tools helping farmers in the selection of their animals to improve the nutritional quality of the produced milk fat. [less ▲]

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See detailGenetic parameters of saturated and monounsaturated fatty acid content and the ratio of saturated to unsaturated fatty acids in bovine milk.
Soyeurt, Hélène ULg; Dardenne, Pierre; Dehareng, Frédéric et al

in Journal of Dairy Science (2008), 91(9), 3611-26

Fatty acid composition influences the nutritional quality of milk and the technological properties of butter. Using a prediction of fatty acid (FA) contents by mid-infrared (MIR) spectrometry, a large ... [more ▼]

Fatty acid composition influences the nutritional quality of milk and the technological properties of butter. Using a prediction of fatty acid (FA) contents by mid-infrared (MIR) spectrometry, a large amount of data concerning the FA profile in bovine milk was collected. The large number of records permitted consideration of more complex models than those used in previous studies. The aim of the current study was to estimate the effects of season and stage of lactation as well as genetic parameters of saturated (SAT) and monounsaturated (MONO) fatty acid contents in bovine milk and milk fat, and the ratio of SAT to unsaturated fatty acids (UNSAT) that reflect the hardness of butter (SAT:UNSAT), using 7 multiple-trait, random-regression test-day models. The relationship between these FA traits with common production traits was also studied. The data set contained 100,841 test-day records of 11,626 Holstein primiparous cows. The seasonal effect was studied based on unadjusted means. These results confirmed that milk fat produced during spring and summer had greater UNSAT content compared with winter (63.13 vs. 68.94% of SAT in fat, on average). The effect of stage of lactation on FA profile was studied using the same methodology. Holstein cows in early first lactation produced a lower content of SAT in their milk fat. Variance components were estimated using a Bayesian method via Gibbs sampling. Heritability of SAT in milk (0.42) was greater than heritability of SAT in milk fat (0.24). Estimates of heritability for MONO were also different in milk and fat (0.14 vs. 0.27). Heritability of SAT:UNSAT was moderate (0.27). For all of these traits, the heritability estimates and the genetic and phenotypic correlations varied through the lactation. [less ▲]

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See detailVariation of delta(9)-desaturase activity in dairy cattle
Soyeurt, Hélène ULg; Dehareng, Frédéric; Mayeres, Patrick et al

in Journal of Dairy Science (2008), 91(8), 3211-3224

The endogenous production of unsaturated fatty acids (FA), particularly some monounsaturated FA (%MONO) and nearly all conjugated linoleic acids, is regulated by the 9-desaturase activity. The aims of ... [more ▼]

The endogenous production of unsaturated fatty acids (FA), particularly some monounsaturated FA (%MONO) and nearly all conjugated linoleic acids, is regulated by the 9-desaturase activity. The aims of this study were to assess the variation of this enzymatic activity within lactation, across dairy breeds, and to estimate its genetic parameters. The ratios of C14:1 cis-9 to C14:0, C16:1 cis-9 to C16:0, and C18:1 cis to C18:0 were calculated from FA contents predicted by mid-infrared spectrometry. Variance components and standard errors were estimated using average information REML. The multitrait mixed model included as fixed effects herd × test date × class of lactation number, class of days in milk × class of lactation number, class of age × class of lactation number, and regressions on breed composition. Four random effects were also included: animal genetic effect, 2 permanent environments (within and across lactations), and residual effect. Under the assumption that the calculated ratios are an approximate measurement of 9-desaturase activity, this study showed different sources of variation for this enzymatic activity. A slight difference was observed within lactation. The ratios of C14:1 cis-9 to C14:0 and C16:1 cis-9 to C16:0 increased as a function of days in milk. Differences across 7 dairy breeds were observed. The values of 9-desaturase indices observed for Jersey and Brown-Swiss cows were lower compared with Holstein. The opposite was observed for dual-purpose Belgian Blue cows. Values of heritability for the ratios of C14:1 cis-9 to C14:0, C16:1 cis-9 to C16:0, and C18:1 cis to C18:0 were 20, 20, and 3%, respectively. Negative genetic correlations observed between fat or protein contents and the 3 indices suggested that an increased activity of 9-desaturase could inhibit the synthesis of fat and protein in bovine milk. Negative correlations were also observed between fat or protein contents and the contents of 3 studied unsaturated FA in milk fat (C14:1 cis-9, C16:1 cis-9, and C18:1 cis). The positive genetic correlations observed between %MONO and the ratios of C14:1 cis-9 to C14:0 (0.72), C16:1 cis-9 to C16:0 (0.62), and C18:1 cis to C18:0 (0.97) showed that %MONO is linked to the 9-desaturase activity. [less ▲]

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See detailGenetic parameters of saturated and monounsaturated fatty acids estimated by test-day model in Walloon dairy cattle
Soyeurt, Hélène ULg; Bastin, Catherine ULg; Dardenne, Pierre et al

in Journal of Dairy Science (2008, July 07)

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

Conference (2008, July)

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

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 detailPotential Estimation of Minerals Content in Cow Milk Using Mid-Infrared Spectrometry
Soyeurt, Hélène ULg; Bruwier, Damien; Gengler, Nicolas ULg et al

in ICAR Proceedings of the Biennial Sessions (2008, June 16)

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See detailStudy of Genetic Variability of Fatty Acid Profile in Bovine Milk and Fat Using Mid-Infrared Spectrometry
Soyeurt, Hélène ULg

Doctoral thesis (2008)

Changes in milk fat composition influence its nutritional quality as well as the technological properties of butter. The impact of feed on fat composition is well known; however, limited information is ... [more ▼]

Changes in milk fat composition influence its nutritional quality as well as the technological properties of butter. The impact of feed on fat composition is well known; however, limited information is available on the genetic variability of fatty acids in bovine milk. The overall aim of this PhD thesis was to study the genetic variability of fatty acid profile in bovine milk and fat. This type of research needs a large amount of data. Expensive reference analysis is used to measure the fatty acid contents in fat. The first objective of this thesis was to develop an alternative method that could be faster and cheaper than traditional methods. Calibration equations predicting the contents of fatty acid from mid-infrared spectrum were established. The contents of saturated and monounsaturated fatty acids, omega-9, fatty acids with short, medium and long chain were the best predicted. Thanks to the implementation of this method in the Walloon routine milk recording, more than 20,000 milk samples were analyzed. This database permitted to model the variation of fatty acid contents in milk and fat. From these models, the genetic variability of fatty acid profile was shown. The complexity of models increased throughout this project due to the increase of new available data. Differences across 7 dairy breeds were estimated using single and multi-trait mixed models. Milk fat and delta-9 desaturase activity of Jersey and dual purpose Belgian Blue differed significantly from Holsteins. Therefore, the choice of a given breed could modify the fat composition. Heritability values obtained for studied fatty acids with multi-trait mixed model ranged from 0.05 to 0.42. Higher values were observed for saturated compared to unsaturated fatty acids. Moderate heritability estimates were observed for the activity of delta-9 desaturase (0.20) and the hardness of butter (0.27). These two traits were estimated by specific fatty acid ratios. The heritability observed using a multi-trait random regressions test day model for the content of saturated fatty acids (0.42) was similar to the one observed for the percentage of fat (0.37). Considering the impact of selection on fat content, the selection could have a great impact on fat composition. High genetic correlations were observed between some fatty acids having similarities in their synthesis. Heritability and correlations varied through the duration of the lactation. Due to the large number of fatty acids, the estimation of an index, which includes the proper fatty acid profile, could be interesting for a future selection program. This PhD thesis provides the background required by future studies to estimate the impact of animal selection on milkfat composition. [less ▲]

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See detailGenetic variability of fatty acids in bovine milk
Soyeurt, Hélène ULg; Gengler, Nicolas ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(2), 203-210

Fatty acids composition of bovine milk influences the technological properties of butterfat and also presents some potential benefits for human health. Impact of feeding on fat composition is well ... [more ▼]

Fatty acids composition of bovine milk influences the technological properties of butterfat and also presents some potential benefits for human health. Impact of feeding on fat composition is well described in the literature; less information is available about the impact of genetics. Based on few studies, essentially conducted to isolate some feeding effect, the breed seemed to influence the fatty acids composition. The variation in the activity of δ-9 desaturase, key enzyme in the production of monounsaturated fatty acids and conjugated linoleic acids in milk, could explain these differences. Very few studies have been focussing on the estimation of genetic parameters of fatty acids composition. However, the moderate heritability estimates observed by these studies for the major fatty acids could suggest a potential genetic effect. [less ▲]

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See detailDosage des sels minéraux du lait par la spectrométrie du moyen-infrarouge. Outil pratique à destination des chercheurs, éleveurs et industriels laitiers
Soyeurt, Hélène ULg; Bruwier, Damien; Dardenne, Pierre et al

in 13ième Carrefour des Productions animales: L'élevage des ruminants en question: vérités et contre-vérités (2008, January 23)

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