Variability Among Morning And Evening Milk
Compositions During The Lactation
V. M.-R. Arnould 1,2,*, N. Gengler 2,3, and H. Soyeurt 2,3
1 CONVIS
s.c., Ettelbruck, Luxembourg; 2 University of Liège, Gembloux Agro Bio-Tech, Animal Science Unit, Animal Breeding and Genetics Group, Gembloux,
Belgique; 3 Fond National pour la Recherche Scientifique (F.N.R.S.), Bruxelles, Belgique.
* Financed by National Research Fund, Luxembourg (AFR PHD-09-119RE)
Abstract
Differences in milk composition between morning and evening milk are documented for major milk components. This study extended research
to milk fat composition. Milk samples were collected between October 2007 and November 2011 in 491 Luxembourg farms and analyzed by
MIR spectrometry. The milk contents of saturated (SFA) and unsaturated fatty acids (UFA) were predicted from the recorded MIR spectral
data. As expected, the milk composition and, especially, the milk fat composition, were affected by AM / PM milking during the lactation.
Therefore adjustments for morning / evening milking are required before using it jointly. Differences in composition could allow different uses of
milk.
Objective
Material and method
Data.
To Analyse the milking-to-milking variability in milk and
milk fat quality.
Holstein cows (n=32,339 cows from 491 herds) in first
lactation (5 < DIM < 366).
Data set:
Milk fat
130,997 records in morning milking data (AM)
125,384 records in evening milking data (PM)
4.60
 Fatty acids predicted from FOSS milk spectrum (Mid-Infared
spectrometry): saturated (SAT) and unsaturated fatty acids
(UFA)
4.50
4.40
 Model:
 Fixed effects: Herd * date of test
Classes of 15 days in milk
Classes of age at calving
 Random effects:
Additive genetic effect
Permanent environment
Residual effects
Variances components estimated by REML (Restricted
Maximum Likelihood )
The significance of differences was evaluated by Student ttest
6
Summer_SAT_AM
Winter_SAT_AM
Summer_SAT_PM
Winter_SAT_PM
Winter
***
Summer
4.30
4.20
NS
NS
4.10
4.00
AM
NS
NS
3.90
PM
AM
PM
3.80
Figure 1. Difference in milk fat percentage according the
milking time and the season during the first lactation.
Milk fat composition
5
 There were no significant difference between AM and PM milk fat
percentage
4
3
 BUT: SAT was higher in the evening milking (fig. 2 and 3).
2
 SFA/UFA was lower during the evening milking (fig. 3).
 There were also some variations in milk fat composition according to the
milking time and the season.
1
Classes of days in milk
PM
 Heritability is defined as proportion
of observable differences between
individuals that is due to genetic
differences
0.50
0.40
Figure 2. SAT (g/dl milk) and UFA (g/dl milk) contents during the first
lactation and according to the milking time and the season.
0.30
 Daily heritability values for SAT
were: AM: 0.33 ± 0.01
0.20
3.50
SAT
3.00
AM
25
0
33
4-
32
0
30
6-
29
0
27
5-
26
0
24
6-
23
0
21
6-
20
0
18
6-
17
0
15
1-
12
1-
13
5
05
91
-1
5
61
-7
5
0.60
31
-4
0-
15
0
NS
UFA
**
0.10
PM: 0.38 ± 0.01
36
5
33
5
30
5
27
5
24
5
21
5
18
5
15
5
12
5
95
65
2.50
35
5
0.00
Classes of 15 days in milk
***
***
2.00
Figure 4. Evolution of SAT daily heritability values accros lactation
and according to the milking time
1.50
Conclusion
1.00
 Milk fat composition varies with the season (summer vs. winter) but also with
the milking time (AM vs. PM).
0.50
0.00
AM_Summer
PM_Summer
AM_Winter
PM_Winter
Figure 3. Evolution of SAT (g/dl milk) during the first lactation and
according to the milking time and the season.
 These observations could allow the diversification of dairy products by
season and milking time
The first author acknowledges the financial support of AFR/FNR (Aide à la Formation Recherche/Fonds National de la Recherche Luxembourg) PhD grant (AFR PHD-09-119-RE).
CONVIS s.c. and Luxembourg farms are acknowledged for providing data.
Contact: varnould@ulg.ac.be
valerie.arnould@convis.lu