Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N.

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Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1,2 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Context  Interest for human health  Many factors affecting milk fat composition have been reviewed (e.g., Palmquist et al., 1993; Soyeurt et al. 2006) : – Feeding, season – Breed – Lactation stage – Number of lactation, age –...

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Δ 9 desaturase  Also named stearoyl Coenzyme-A desaturase or SCD  Able to introduce a cis-bond between carbons 9 and 10 of SFA  Involved in the production of the majority of MONO and CLA in milk

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium General objective Study the genetic variation of Δ 9 - desaturase activity in bovine milk within and between lactations using multitrait random regression test-day models

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Lactation stage effect  Milk fat composition significantly change with lactation stage (Stoop et al., 2008)  Principally due to changes in energy status

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Lactation number effect  Few information are available on lactation number effect on Δ9 activity  Lactation number effect = age effect ?  Contradictions / fat content: Milk fat not affected by lactation number Fat content decreases with increasing number of lactation (or age of cow)

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Lactation number effects  Contradictions / fat composition No difference The amount of UNSAT increases with increasing age While palmitic acid decreases

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Materials & Methods  Data set  Spectra collected between January 2007 and October 2008  Holstein cows (> 84%)  Milk history 4 < DIM < 365 Milk yield, %Fat, %Protein  Multi-trait random regression test-day models

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Materials & Methods  Lactations were grouped as following: First lactation (39%) Second lactation (29%) Third and fourth lactations (32%)  Random herd-based data sub set

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Materials & Methods  Models:  Fixed effects: Herd x date of test Class of 15 days in milk (20) Class of age (16)  Random effects: Herd x year of calving Permanent environment Additive genetic effect Residuals Second order Legendre Polynomials

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Studied traits  Milk yield  Fat content  Protein content  3 Δ 9 indices (product / substrate):  C14:1 cis-9/C14:0  C16:1 cis-9/C16:0  C18:1 cis-9/C18:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set Milk (kg/day) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Fat (g/100 g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Protein (g/100g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set Milk (kg/day) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Fat (g/100 g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Protein (g/100g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Similar statistical characteristics between population and sample data set Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set Milk (kg/day) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Fat (g/100 g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Protein (g/100g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Slight increasing of milk yield with increasing number of lactation Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set Milk (kg/day) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Fat (g/100 g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, Protein (g/100g of milk) Lact 181,57630, Lact 246,98423, Lact 3 and 4 70,65524, No modification of fat content with increasing number of lactation Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set C14:1 cis-9 / C14:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, C16:1 cis-9 / C16:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, C18:1 cis-9 / C18:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium NMeanSD Total population Sample data set Total population Sample data set Total population Sample data set C14:1 cis-9 / C14:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, C16:1 cis-9 / C16:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, C18:1 cis-9 / C18:0 Lact 181,57630, Lact246,98423, Lact 3 and 4 70,65524, Similar observations Studied traits

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Results Lactation stage effect

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability Lactation 1

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability Lactation 1 Variability of heritability C14:1 cis-9/C14: C16:1 cis-9/C16: C18:1 cis-9/C18:0 0.15

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability Lactation 1 Increasing of heritability values throughout the lactation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Variance component Lactation 1 - C14:1 cis-9/C14:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Variance component Lactation 1 - C14:1 cis-9/C14:0 Increasing of genetic variance component throughout the lactation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Results Lactation number effect

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability C14:1 cis-9/C14:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability C14:1 cis-9/C14:0 C14:1 cis-9/C14:0 Lactation 1: 0.23 Lactation 2: 0.22 Lactations 3 et 4: 0.20

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability C14:1 cis-9/C14:0 Similar trends of heritability estimates for lactations 1, 2, and 3 and 4

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability C16:1 cis-9/C16:0 C18:1 cis-9/C18:0 Similar observations for C16:1 cis-9 /C16:0 and C18:1 cis-9/C18:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Heritability Lactation 1Lactation 2Lactations 3 and 4 C14:1 cis-9/ C14: C16:1 cis-9/ C16: C18:1 cis-9/ C18: Few or none difference between lactations

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Genetic variance component C14:1 cis-9/C14:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Genetic variance component C14:1 cis-9/C14:0 Similar trends of genetic variance estimates for lactations 1, 2, and 3 and 4

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Genetic variance C16:1 cis-9/C16:0 C18:1 cis-9/C18:0 Similar observations for C16:1 cis-9 /C16:0 and C18:1 cis-9/C18:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Results Correlations

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C14:1 cis-9/C14:0 Milk (kg/day) Fat content (g/100 g of milk) Protein content (g/100 g of milk) Lactation Lactation Lactations 3 and Genetic correlation Phenotypic correlation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C14:1 cis-9/C14:0 Milk (kg/day) Fat content (g/100 g of milk) Protein content (g/100 g of milk) Lactation Lactation Lactations 3 and Genetic correlation Phenotypic correlation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C16:1 cis-9/C16:0 Milk (kg/day) Fat content (g/100 g of milk) Protein content (g/100 g of milk) Lactation Lactation Lactations 3 and Genetic correlation Phenotypic correlation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C18:1 cis-9/C18:0 Milk (kg/day) Fat content (g/100 g of milk) Protein content (g/100 g of milk) Lactation Lactation Lactations 3 and Genetic correlation Phenotypic correlation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C14:1 cis-9/C14:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Relationships C16:1 cis-9/C16:0 C18:1 cis-9/C18:0 Similar observations for C16:1 cis-9 /C16:0 and C18:1 cis-9/C18:0

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium  Application: Sort sires according to their breeding values for C14:1 cis-9/C14:0  Comparison among the lists of sires obtained for the 3 lactation groups Spearman correlation

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Spearman correlation Lactation 1Lactation 2Lactations 3 and 4 Lactation Lactation Lactations 3 and 4 1

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Spearman correlation Conclusions:  The top 20 is similar for the 3 lactation groups  So, dairy cow in first lactation is as good in second or third lactation.

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Conclusions  Lactation stage effects – Genetic variability of Δ9 activity throughout lactation  Lactation number effects – None or few useful effects of lactation number on Δ9 activity

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Conclusions  The desaturation of milk fatty acids presents a substantial genetic component → possibility to modulate milk fat profile by selective breeding  Negative correlations between Δ9 activity (ratios) and fat and protein content: increasing activity of Δ9 → could inhibit the synthesis of fat and protein in bovine milk

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium In the future  Study the difference between Δ9 activity estimator  Enlarge the studied number of lactation: per example: 1-3 vs 4-6

Lactation Number Effects on the Genetic Variability of the Stearoyl Coenzyme-A Desaturase 9 Activity Estimated by Test-Day Model V. M.-R. Arnould 1, N. Gengler 1,2, and H. Soyeurt 1 1 Gembloux Agricultural University, Animal Science Unit, Belgium 2 National Fund for Scientific Research, Belgium Thank you for your attention Acknowledgments SPW – DGA-RNE project: D (section 1) AWE Milk committee (Battice) FNRS: F (2) F FRFC