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Using dietary crude protein to manipulate
energy balance in early lactation dairy cows
S.J. Whelan1,3, F.J. Mulligan2B. Flynn3, J.J. Callan3 and K.M. Pierce1 1School of Agriculture and Food Science and 2School of Veterinary Medicine
University College Dublin, Belfield, Dublin 4
3UCD Lyons Research farm, Newcastle, Dublin, Ireland
Introduction
Dairy production in Ireland
Nutritional issues of the early lactation dairy cow
Recent energy balance experiments conducted at UCD
Effect of supplementary concentrate type on energy balance in the
early lactation, pasture fed dairy cow
Effect of dietary CP and starch content on energy balance in early
lactation dairy cows
Conclusions
Overview of Presentation
Largely seasonal production system
1.1 million dairy cows
5,000 kg average milk production
Contributes €2.7 billion to Irish exports
However, still room for improvement…
Replacement rate is 25%
15% are replaced due to infertility
Calving interval is 394 days
Dairy Production in Ireland
Nutritional issues of the early lactation dairy cow
• Early lactation is a challenging period for the dairy cow
• Important to explore dietary strategies that reduce these challenges
• Optimising DMI is important in improving energy balance
• Moderating milk yield through dietary CP may also improve energy
balance
Manipulating CP intake in the pasture fed early
lactation dairy cow
Basis for Experiment
Pasture is the most abundant forage source available to Irish
dairy farmers
However…
– Chemical composition of grass can vary considerably
– This flux in nutrient supply may be detrimental to the animals health
Therefore…
– Concentrate supplementation is often required, but…
– Concentrate type will be important
Materials and Methods
Randomised block design
Day 1 until day 100 postpartum
11 animals per dietary treatment
Balanced for parity, milk yield, constituent yield and calving
date
Blood samples harvested on weeks 2 through to 5 postpartum
Milk samples taken weekly
Energy balance determined during week 6 post partum
Concentrate Treatments
Supplements were fed twice daily during milking (6kg total)
4 supplementary concentrate treatments
HP(180g CP kg-1, rolled barley)
LP(140g CP kg-1, rolled barley)
LP+ HMBi (140g CP kg-1, rolled barley + supplementary
methionine (HMBi))
LP Corn (140g CP kg-1, ground maize grain)
Chemical Composition of diets offered
HP LP LP+HMBi LP Maize Pasture
DM (g kg-1) 867 858 862 859 207
Energy (UFL) 1.12 1.10 1.10 1.14 0.98
Crude protein 192 150 150 150 170
PDIA 72 52 52 74 39
PDIN 145 108 108 122 107
PDIE 139 120 120 133 98
NDF 219 218 222 223 438
ADF 91 106 111 115 219
ADL 7 10 12 7 63
Ash 87 81 80 79 73
Starch 296 303 307 344 -
Results
Pasture Dry Matter Intake
0
2
4
6
8
10
12
14
16
Concentrate Type
Pa
stu
re D
MI
(kg d
-1)
HP LP LP+HMBi LP Maize
n.s.
Weekly Milk Yield
16
18
20
22
24
26
28
30
32
34
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Mil
k Y
ield
kg d
-1
Week Postpartum
HP LP LP+ HMBi LP Maize
HP vs. LP (P < 0.05) Week (P < 0.01) Week x Trt. (P < 0.05)
Energy Intake
0
2
4
6
8
10
12
14
16
18
20
Concentrate Type
Inta
ke(U
FL
d-1
)
HP LP LP+ HMBi LP Maize
ns
Energy Corrected Milk
0
5
10
15
20
25
30
35
40
Concentrate Type
EC
M (
kg d
-1)
HP LP LP+ HMBi LP Maize
ab b
a ab
a vs. b, P < 0.05
Energy Balance
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
En
ergy
Bala
nce
(U
FL
d-1
)
Concentrate Type
HP LP LP+HMBi LP Maize
ns
Blood Metabolites
Blood Urea Nitrogen
0
1
2
3
4
5
6
7
Concentrate Type
Blo
od
Urea N
(m
mol
L-1
)
HP LP LP+ HMBi LP Maize
a
b b b
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Concentrate Type
βH
BA
(mm
ol
L-1
)
HP LP LP+ HMBi LP Maize
a
b
b b
a vs. b (P < 0.05)
Beta Hydroxy Butyric Acid
Non Esterified Fatty Acids
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Concentrate Type
NE
FA
(mm
ol
L-1
)
HP LP LP+ HMBi LP Maize
a ab
b ab
a vs. b (P < 0.05)
Glucose
0
0.5
1
1.5
2
2.5
3
3.5
4
Concentrate Type
Glu
cose
(mm
ol
L-1
)
HP LP LP+ HMBi LP Maize
b b ab a
a vs. b (P < 0.05)
Conclusions
• Milk yield was reduced where LP was offered. However…
– ECM was not different
• Lower BHBA and blood urea N indicated a more favourable
metabolic status where low CP concentrates were offered
• The use of maize grain or supplementary methionine in low CP
concentrates improved milk production without impacting on
metabolic status
Dietary manipulation of crude protein and starch content
affects energy balance in early lactation dairy cows
Basis for Experiment
• Early lactation is a challenging period for the dairy cow
• Reducing dietary CP intake can improve EB
• Similarly providing glucogenic diets can improve the
metabolic status of the diary cow
• However, the simultaneous application of these strategies has
not been tested to date
Materials and Methods
• Randomised block design
• Day 1 until day 63 postpartum
• 10 animals per dietary treatment
• Balanced for milk yield, constituent yield and calving date
• Blood samples harvested on days 0, 7, 14, 21, 28, 35 and 63
• Milk samples taken weekly
• Post experiment
• All animals offered a pasture based diet
Dietary Treatments
• Diets were offered once daily as a TMR
1. High CP low starch TMR (HP-LS)
– 15% CP
– 6% Starch
2. Low CP high starch TMR (LP-HS)
– 12% CP
– 28% Starch
• Diets were iso-energetic (1.05 UFL/ kg DM)
Chemical Composition of diets
offered HP-LS LP-HS
Composition (% unless stated)
DM 29.3 37.3
UFL/ kg DM 1.05 1.05
CP 14.6 11.9
NDF 54.5 39.3
PDIA 4.0 3.8
PDIN 8.9 7.8
PDIE 9.4 9.3
ADF 35.1 25.3
ADL 4.1 2.9
NDF for. 32.2 27.4
Ash 7.5 5.7
Starch 5.7 27.5
Results
Dry Matter Intake over the Duration
of the Experiment
10
12
14
16
18
20
22
1 2 3 4 5 6 7 8 9
Inta
ke
(kg D
M d
-1)
Week of Lactation
HP-LS LP-HS
Diet P = 0.25
Week P < 0.01
Diet x Week P = 0.17
20
22
24
26
28
30
32
34
Diet
Mil
k Y
ield
(k
g/
d)
HP-LS LP-HS
P < 0.01
Daily Milk Yield for the Experiment
Milk Constituent Yield
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Fat Protein Casein
Mil
k C
on
stit
uen
t Y
ield
(k
g/
d)
HP-LS LP-HS
P < 0.01 P < 0.01
P < 0.01
P = 0.99
305d Lactation Yield
0
1000
2000
3000
4000
5000
6000
7000
8000
Diet
Mil
k Y
ield
(k
g d
-1)
HP-LS LP-HS
HP-LS LP-HS
Fat (Kg) 349 334
Protein (Kg) 255 261
Energy Balance over the Duration of
the Experiment
Diet P = 0.02
Week P < 0.01
Diet x Week P = 0.75
-4
-3
-2
-1
0
1
2
3
4
1 2 3 4 5 6 7 8 9
Ener
gy
Bal
ance
(U
FL
/ d)
Week of Lactation
HP-LS LP-HS
0
0.4
0.8
1.2
1.6
2
2.4
2.8
3.2
3.6
BCS at Calving BCS at d63
BC
S U
nit
s
HP-LS LP-HS
P = 0.47
BCS at Calving and Day 63
P = 0.36
Loss = 0.2 BCS
Blood Metabolites
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Diet
BH
BA
(mm
ol/
L)
HP-LS LP-HS
Beta Hydroxy Butyric Acid
P = 0.03
Non Esterified Fatty Acids
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Diet
NE
FA
(mm
ol/
L)
HP-LS LP-HS
P = 0.54
Glucose
0
0.5
1
1.5
2
2.5
3
3.5
Diet
Glu
cose
(mm
ol/
L)
HP-LS LP-HS
P = 0.36
Conclusions
• Offering early lactation dairy cow a low CP, high starch diet
improves energy balance
• Reductions in milk yield observed during early lactation did
not affect 305 d lactation yields
• Blood metabolites did not indicate a severe metabolic
challenge in this experiment
Overall Conclusions
• Regardless of production system, the maintenance of DMI is
key in maintaining a more positive energy balance
• Reducing CP intake moderates milk production and reduces
the urea burden on the animal, thus reducing energy demands
• Further work is required in pasture based production systems
to determine the extent to which CP can be reduced
• Work is also required to determine the lifetime effects of these
strategies on the survival of the dairy cow
Acknowledgements
This research was funded under the National Development Plan
through the Research Stimulus Fund administered by the Irish
Department of Agriculture, food and Marine
Additionally I would like to acknowledge the assistance of the
farm and laboratory staff at UCD Lyons Research Farm
Thank You for your time
