The Effect of Plant Species Diversity on Intake, Productivity

and Grazing Behavior

Kathy J. SoderAnimal Scientist

USDA-ARS Pasture Systems & Watershed Mgmt. Research Unit

UVM Ext. Organic Dairy Conference, Randolph, VT Jan. 2011

• "It has been experimentally proved, that if a plot of ground be sown with one species of grass, and a similar plot sown with several distinct genera of grasses, a greater weight of dry herbage can be raised in the latter than in the former case."

Everything old is new again

• "It has been experimentally proved, that if a plot of ground be sown with one species of grass, and a similar plot sown with several distinct genera of grasses, a greater weight of dry herbage can be raised in the latter than in the former case." Charles Darwin, The Origin of Species, 1872

Everything old is new again

How diverse are pastures?Biomass yield of organisms in a temperate grassland

Source: Pimentel, 1992

kg fresh wt/haPlants 20,000Fungi 4,000Bacteria 3,000Arthropods 1,000Annelids 1,320Protozoa 280Algae 200Nematodes 120Mammals 1.2Birds 0.3

How diverse are pastures?

• Pasture Diversity Survey

• Completed 4th year of a long-term survey across the northeast U.S.

Northeast USA pasture biodiversity# Species Source

Herbaceous plants 268 Goslee and Sanderson, unpublished

Soil seed bank 54 Tracy and Sanderson 2000 J. Range Mgmt.Klement and Sanderson, unpublished

Beetles 275 Byers et al. 2000 Great Lakes Entomol.

Soil macroinv. 2-18 Byers and Barker 1999 Grass Forage Sci.

Species composition asproportion of pasture cover

White clover

Bluegrass

Weeds

Orchardgrass

Fescue

Composition of plant speciesin northeastern pastures(proportion of total species)

Perennial forbs

Perennialgrasses

Annual forbs

Legumes

Total of 160 plant species across the Northeast,average of 32 species per pasture

How diverse are pastures?• Seedbank-total of 54 species across Northeast

Seed

s pe

r ac

re (

mill

ion

s)

0.0

0.5

1.0

1.5

2.0

Yellowrocket

Lambsquarters

Bluegrass Whiteclover

Why may plant biodiversity be important?

Ecological research suggests:

• Productivity benefits• Better nutrient use• Increased stability,

resilience, resistance to invasion

Emphasis in certain govt. ag programs

Dry Normal Wet

Wat

er P

oten

tial

(MP

a)

-2

-1

0

1

2

3

4

5

6

7

Tra

nspi

ratio

n R

ate

(ug/

cm2 /s

)

Simple MixtureComplex Mixture

White clover

aaaabc

a

b

a

bc

a

c

Gra

vim

etric

Soi

l Moi

stur

e (%

)

20

25

30

35

Simple Mixture Complex Mixture

Dry Treatment, 30 cm Depth

2000 2001M J J A SM J J A S O

White Clover Red Clover Orchardgrass

Per

cent

Red

uctio

n in

Gro

wth

Rat

e by

Dro

ught

-50

-40

-30

-20

-10

0

Simple MixtureComplex Mixture

Diversity and Ecosystem Function: Water UseBetter forage growth in complex mixture under drought stress

April May June July Aug Sep Oct

Reg

row

th p

er m

onth

(lb/

acre

)

0

400

800

1200

1600

2000

Tall Fescue + trefoilTall fescue + 7 species

Data from Gerrish and Sanderson, Proc. Am. Forage and Grassl. Conf. 2000

Diversity and Ecosystem Function: Water UseComplex pasture mixtures had greater regrowth during a

hot dry summer in Missouri

6/25/00 7/2/00 7/9/00 7/16/00 7/23/00 7/30/00

Pota

to L

eafh

oppe

r Inj

ury

Rat

ing

1

2

3

4

5

Simple mixture

Complex mixture

** *

White clover

Legume has less insect damage in complex mixture

Data from Howard Skinner and Bob Byers, USDA-ARS, University Park

Diversity and Grazing Behavior

25-40 lb. DM

125-200 lb. As Fed

Factors Affecting Pasture DMI

Grazing time (GT)x

Bites/min (BR)x

Intake/bite (I/B)=

Pasture intake

Factors Affecting Grazing Behavior

Pasture DMI = GT x BR x I/B

Animal Factors- Size- Milk Production- Genetic Merit

Pasture Factors- Height- Density- Diversity??

Why do ruminants eat clover in the morning and grass in the afternoon?

Measuring preference

• Manual observation• Scan sampling…• … 2 minute interval• Record E I or R…• …on grass or clover

Adjacent monocultures

Grass Clover

Why change in preference from morning to afternoon?

• Clover is preferred over grass– Palatability– Intake rate of clover is higher

• Satiate/bloat on clover- switch to – ↑ fiber, ↓ CP

• “Fiber fill” of grass for overnight rumination.

Mixed grass/clover sward

Need to searchfor preferredherbage i.e.a constraint

≡ SelectionMixed grass/cloversward

Adjacent monocultures

Remove needto search i.e.no constraint

≡ PreferencePure grasssward

Pure cloversward

How do they know?

• Ruminants learn to eat from:* their dams* other animals* trial and error

Lambs learn quickly,and remember for years

0

100

200

300

400

None Alone Mother

3 Months 34 Months

Inta

ke o

f whe

at, g

/d

Exposure to Wheat (1 h/d for 5 d at 6 wk age)

Experiences aren’t all equal

0

50

100

150

Mother Ewe Alone

Observe Participate

Serv

iceb

erry

, bite

s/la

mb

Lambs eat what mom eats...

0

5

10

15

20

25

1 2 3 4 5Day of Exposure

Mom avoids mountain mahogany

Mom eats serviceberry

Num

ber o

f bite

s/la

mb

....even after weaning

0

25

50

75

100

1 2 3 4 5 6 7Day

mountain mahogany

serviceberry

0

25

50

75

100

62 63 64 65 66 67 68

Day

serviceberry

mountain mahogany

Serv

iceb

erry

, % o

f bite

s

What about calves raised in hutches or without role models?

What about calves raised in hutches or without role models?

Experience Influences Performance

Body weight * * *Body condition * * *Milk production * * -Post-partum interval * * -

Year 1 Year 2 Year 3

Prior Experience

Prior Illness

0

100

200

300

LiCl 2 3 4 5Day

rice wheat

Inta

ke, g

Ewes were averted to caragena

Does “hunger” impact behavior?

Ruminal Fill and Grazing Behavior

0%

100%66%

33%

Ruminal Fill and Grazing Behavior

0% 100%

Bite Mass ↓ 375%Bite Depth ↑ 40%Bite Area ↓ 280%

Ruminal Fill and Grazing Behavior

0% 100%

Ghrelin ↓Insulin ↓Glucose ↑

Ruminal Fill Study Conclusions

• The lower the ruminal fill the greater the appetite.

• Cattle with greater appetite – Consume more pasture per unit of time. – Take bites of greater mass at the same rate.– Take shallower bites of greater area.

• Differences in levels of circulating ghrelin, insulin and glucose demonstrate the effect of ruminal fill on appetite regulating hormones (“hunger”).

Cows prefer a mixed diet……

How do we Know?

25%

75%

75%

25%

50%

50%

Grazing at random

25%

75%

25%G

75%C

75%

25%

75%G

25%C

50%

50%

Grazing at random

50%G

50%C

Pro

port

ion

in

diet

25%

75%

50%G

50%C

75%

25%

50%G

50%C

Active preference for 50:50

50%

50%

50%G

50%C

Pro

port

ion

in

diet

Cost of selection? - sheep

• Ewes & lambs

• 4 treatments: Clover only Grass only

Adj. Mono’sMixed sward

• Grazing time

• Daily intake

Cost of selection - sheep

Cost of selection? - cattle

• Expt. in 1999• Lactating cows• Two treatments:

Adj. Mono’sMixed sward

Milk yield and composition Preference and intake

Cost of selection - cattle

-6

-4

-2

0

2

4

6

-1 1 2 3 4 5 6 7 8 9

Week of treatment

Cha

nge

in m

ilk y

ield Mixed

Mono's

Can Forage Mixtures Improve Productivity of

Dairy Cows?

Kathy J. Soder, Matt A. SandersonUSDA-ARS, Pasture Systems & Watershed Mgmt.

Research Unit, University Park, PA

Julia L. Stack, Larry D. MullerThe Pennsylvania State University

Pasture Treatments

• Two-species (2SP)– Orchardgrass, White Clover

• Three-species (3SP)– 2SP + Chicory

• Six-species (6SP)– OG, Red Clover, Chicory, Tall Fescue,

Perennial Ryegrass, Birdsfoot Trefoil• Nine-species (9SP)

– 6SP + White Clover, Alfalfa, KY Bluegrass

Pasture Intake

lb/dPasture Intake, lb/d Total intake, % BW

%

Forage Diversity

Grazing BehaviorTrt- Time

0100200300400500600700800900

1000

Grazing Ruminating Idling

2SP3SP6 SP9 SP

min

abc

ac a

a

b

b

ab

Milk Yield2002 & 2003

lb/d

Forage Diversity

Conjugated Linoleic Acid

0

0.2

0.4

0.6

0.8

1

1.2

Pre-trial

2SP 3SP 6SP 9SP Post-trial

g CLA/100 g FA

Forage Diversity

a

b b b

**

Seasonal Forage Yieldlb/ac

Forage Diversity

Weed Contamination%

Forage Diversity

*Averaged over both years

Summary• Complexity of pasture species had no

effect on intake or productivity of cows• Cows maintained high level of production• Complex mixtures were more productive

in drought year• Complex mixtures had

less weed pressure• Pastures reverted back to

OG/WC over time

Conclusions• Complex mixtures of forages in pasture

may benefit forage production without compromising animal performance

• Managing for a moderately complex (3 to 5 species) mixture of pasture forages may result in greater carrying capacity of pastures and reduce weed competition

• May take work (overseeding, fertilization) to maintain high levels of biodiversity

Thank you.

Are there any questions?