Nutritive value of forage legumes used for grazing and silage – R.J. ...

Nutritive value of forage legumes
used for grazing and silage
RJ Dewhurst 1 , L Delaby 2 ,
A Moloney 1 , T Boland 3 and E Lewis 1
1 Teagasc Animal Production and Grassland
Research Centre, 2 INRA Production du Lait,
3 University College Dublin

Outline of talk
• Production responses
• Digestion and feed intake
• Product quality – fatty acids
• Environment – nitrogen, methane
• Health – bloat
• Fertility
• Concluding remarks

Milk yield (kg/d)
Legume silages: milk yield
35
30
25
20
15
10
SED=1.81; P

Legume silages: lamb growth
la m b g r o w th r a te ( g /d )
400
300
200
100
0
Grass Red clover
Fraser et al. 2004

Milk yield (kg/d)
Grazed white clover: milk yield
30
25
20
15
10
5
0
Ribeiro
Filho et al.
2003
Ribeiro
Filho et al.
2003
Phillips &
James
1998
PRG
PRG/WC
Phillips et
al. 2000

Digestibility of legume silage diets
Diet digestibility (%)
80
75
70
65
60
55
50
Grass 50%
Red
clover
SED=0.96; P

DMI of legume silages: cows
Silage DM intake (kg/d)
15
14
13
12
11
10
9
8
SED=0.80; P

DMI of legume silages: lambs
D ry m a tte r in ta k e
(k g /d )
3
2
1
0
Grass Red clover
Fraser et al. 2004

DMI: grazed ryegrass/white clover
DM intake (kg/day)
15
13
11
9
7
5
0 50 100
% white clover
Expt. 1
Expt. 2
Harris et al. 1998

DM degraded (%)
100
80
60
40
20
0
rate ‘c’
0 10 20 30 40 50
Time (hours)
‘b’ fraction
‘a’ fraction

DM degradation (a and b fractions; %)
%
60
50
40
30
20
10
0
a b
G FI
RC FI
G SE
RC SE
WC SE
G UK
RC UK
WC UK

DM degradation rate (c; per hour)
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
G FI
RC FI
G SE
RC SE
WC SE
G UK
RC UK
WC UK

Rumen passage rate (%/hour)
6
5
4
3
2
1
0
SED=0.61 P

proportion of rumen DM (g/kg)
500
450
400
350
300
250
200
150
100
50
0
SED=0.024; P

White clover
• High fermentation rate
• High rumen passage rate
• High intake
• High milk/DM intake
Lucerne
• Rapid particle breakdown
• High rumen passage rate
• High intake
• Low milk/ DM intake

• May:
Changes in digestibility
– Perennial ryegrass: -20 g/kg DM
– White clover: -10 g/kg DM
• Later rotations (28 to 42 d regrowth):
– Perennial ryegrass: -20 g/kg DM
– White clover: no decline
Giovanni, 1990

Outline of talk
• Production responses
• Digestion and feed intake
• Product quality – fatty acids
• Environment – nitrogen, methane
• Health – bloat
• Fertility
• Concluding remarks

Red clover effect on milk PUFA
% of milk fatty acids
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
SED=0.05
P

Alpha-linolenic acid in organic milk
linolenic acid (% of milk fat)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
SED=0.084; P

Polyphenol oxidase in red clover
Normal Red Clover Low PPO Red Clover

PPO and lipolysis in red clover
Free fatty acids (g/g)
0.12
0.08
0.04
0.00
low PPO
normal PPO
0 2 4 6 8 10 12 14
Time (Hours)
Lee et al., 2004

Herbage composition (for ensiling)
g/kg DM
600
500
400
300
200
100
0
Perennial ryegrass
White clover
Red clover
Crude protein Water-soluble
carbohydrates
NDF

Legume silages: N-use efficiency
Milk-N / feed-N (%)
30
28
26
24
22
20
18
16
14
12
10
Grass 50%
Red
clover
SED=0.15; P

Milk and Urine N output (g/day)
180
160
140
120
100
80
60
40
20
0
Grass silage 40% red clover
60% maize
Milk N
Urine N
25% red clover
75% maize

Methane
• Usually lower for animals fed forage
legumes
• Variety of mechanisms:
– Lower fibre content
– Higher DM intakes
– Higher passage rates (reduced residence)
– Secondary plant metabolites such as
condensed tannins in some legumes

Bloat
• Problem with RC, WC and LUC
• Formation of slime traps gas leading to
rumen distension
• Complex aetiology linked to soluble protein
and small particles in these legumes
• Animals vary in susceptibility – related to
saliva production and rumen kinetics
• Condensed tannins make legumes bloat
safe, but Lotus has agronomy issues

Effect of red clover on fertility?
• Contains phyto-oestrogens, particularly
formononetin, that can interfere with
reproductive cycles
• Sheep are sensitive to these compounds
• Only two studies with dairy cows – both
increased first service conception rate

Effects of red clover silage on
conception rate of heifers
pregnancy rate to
first service (%)
Grass
silage
Red clover
silage
43 76
Austin et al., 1982

Possible mechanism for effect
of red clover on fertility?
• Modern red clover varieties are lower in
phyto-oestrogens
• Cows less sensitive to phyto-oestrogens
• High intake forage promotes better cow
condition
• Better supply of n-3 fatty acids (affects
prostaglandin metabolism)

Concluding remarks
• Legumes usually increase milk or meat
production, whether grazed or fed as silage
• Main effect through increased intake, linked to
high rumen digestion and passage rates
• Other benefits: increased milk PUFA; reduced
methane; cow fertility?
• Hazards: bloat; high urine Nitrogen
• Beneficial traits in other legumes (e.g. Lotus) –
but not well adapted here