The Right Forages for Dairy HeifersWayne K. Coblentz, USDA-ARS

U.S. Dairy Forage Research Center, Marshfield, WI

Some Thoughts About Forage Quality

Forage quality is highly dependent on climate, forage

type, harvest management, and many other factors.

83.0

69.9

64.4

24-h Dig

84.077.8.15Veg

70.765.2.16Bud

65.858.9.13Mid Bloom

48-h Dig

12-h Dig

Kd, /h

81.1

74.4

65.2

24-h Dig

84.971.4.102nd

Node

80.363.2.08Boot

72.054.2.07Full Head

48-h Dig

12-h Dig

Kd, /h

Orchardgrass →

← Alfalfa

Sources: Hoffman et al., 1993

0

20

40

60

80

0 20 40 60 80 100Incubation T ime (h)

% D

M R

emai

ning

Alfalfa (late vegetative)Alfalfa (late bud)Alfalfa (midbloom)

0

20

40

60

80

0 20 40 60 80 100Incubation Time (h)

% D

M R

emai

ning

Orchardgrass (2nd node)

Orchardgrass (boot)

Orchardgrass (fully headed)

Maturity

68.4

81.1

24-h Dig

79.652.9.06VegRegrowth

(AR)

84.971.4.082nd node (WI)

48-h Dig12-h DigKd, /h

Sources: Hoffman et al., 1993; Ogden et al. (2005)

Temperature

0

20

40

60

80

0 20 40 60 80 100Incubation T ime (h)

% D

M R

emai

ning

Orchardgrass (2nd node)

Orchardgrass (Veg, AR)

0

20

40

60

80

0 20 40 60 80 100Incubation Time (h)

% D

M R

emai

ning

Alfalfa (late bud)Orchardgrass (boot)Bermudagrass (WS)

0

20

40

60

80

0 20 40 60 80 100Incubation Time (h)

% D

M R

emai

ning

Alfalfa (midbloom)Orchardgrass (fully headed)Bermudagrass (42 days)

69.0

74.4

69.9

24-h Dig

80.654.5.05BG

80.363.2.08OG

70.765.2.16Alfalfa

48-h Dig

12-h Dig

Kd, /h

56.0

65.2

64.4

24-h Dig

69.344.2.03BG

72.054.2.07OG

65.858.9.13Alfalfa

48-h Dig

12-h Dig

Kd, /h

Moderate Quality →

← High Quality

Sources: Hoffman et al., 1993; Galdamez-Cabrera et al., 2003; Ogden et al., 2003.

Forage Type

IVDMD vs. Maturity (Alfalfa)

30

40

50

60

70

80

0 20 40 60Days from May 28

IVD

MD

, % o

f DM

LeafStem

Adapted from Van Soest, 1982

IVDMD vs. Maturity (Van Soest, 1982)

30

40

50

60

70

80

0 20 40 60Days from May 28

IVD

MD

, % o

f DM

LeafStem

Adapted from Van Soest, 1982

0

20

40

60

80

100

0 20 40 60 80 100

Incubation Time (h)

% N

DF

Rem

aini

ng

Alfalfa, 10% BloomEastern Gamagrass, Mature

26.3.0378.0Eastern gamagrass

32.3.0840.9Alfalfa

NDFD*, %Kd, /hNDF, %

* Effective degradability of NDF calculated on the basis of a 6%/h passage rate.

47.7.0925.4Leaf

32.3.0840.9Whole-plant

20.2.0559.4Stem

NDFD*, %

Kd, /h

NDF, %

0

20

40

60

80

100

0 20 40 60 80 100Incubation Time (h)

% N

DF

Rem

aini

ng

Alfalfa (late vegetative)Alfalfa (late bud)Alfalfa (midbloom)

47.9.1131.0Veg

32.0.0942.6Bud

28.6.0747.3Midbloom

NDFD*, %

Kd, /h

NDF, %

Source: Coblentz et al. (1998)

Source: Hoffman et al. (1993)

0

20

40

60

80

100

0 20 40 60 80 100Incubation T ime (h)

% N

DF

Rem

aini

ng

LeafStemWholeplant

Alfalfa - Maturity (NDF)

Alfalfa - Plant Part (NDF)

*Passage rate = 6%/h

A discussion of appropriate forage quality (the right forage) is highly

dependent on what you intend to feed.

Assuming this is a 1200-lb (pregnant, nonlactating) beef cow wandering aimlessly in

the Ozarks, the required energy density of her diet

should be about 47.1% TDN.

XX X

Relationship between TDN and NDF (NRC, 2001)

LegumeY = 0.016x2 - 1.93x + 112.5

R2 = 0.978

Cool-Season GrassY = 0.012x2 - 1.86x + 125.5

R2 = 0.991

50

54

58

62

66

70

30 40 50 60 70

NDF, %

TDN

, %

Corn Silage

300 lbs

600 lbs

900 lbs1200 lbs

Within this context ……,

maturing forages are not necessarily a problem, and in many cases actually may be desirable.

The “right forage” may not be the one with the best or highest quality.

35

40

45

50

55

60

65

ND

F or

TD

N, %

of D

M

0 5 10 15 20Days from Stage 2

NDF TDN

● linear increase of NDF (0.4 percentage units/day), plus an associated reduction of TDN (0.25 percentage units/d) following Stage 2

2000

2500

3000

3500

4000

4500

5000D

M Y

ield

, lbs

/acr

e

0 5 10 15 20Days from Stage 2

adapted from Brink (unpublished)

● mean of eight harvests of ‘Affinity’ alfalfa over two years (2004-2005)

● increase of 92 lbs DM/acre/d following Stage 2

● results in improved harvest efficiency and (possibly) fewer harvests.

Effects of Maturity on Alfalfa Yield and NDF

Relationship between CP and NDF (NRC, 2001)

LegumeY = 0.017x2 - 1.86x + 69.2

R2 = 0.962

Cool-Season GrassY = 0.043x2 - 5.53x + 189.1

R2 = 0.959

0

5

10

15

20

25

30

30 40 50 60 70NDF, %

Cru

de P

rote

in, %

Corn Silage

300 lbs

600, 1200 lbs900 lbs

Effects of Alfalfa Harvest Timing on Estimates of RDP by SGPMethod (Coblentz et al., 2008)

18

20

22

24C

P, %

of D

M

0 5 10 15 20Days from Stage 2

2004, Quadratic (P < 0.001)

60

65

70

75

RD

P, %

of C

P

0 5 10 15 20Days from Stage 2

2004, Linear (P < 0.001)

Increased maturity also results in lower CP and rumen degradable protein (RDP), both of which are desirable generally for dairy heifers.

A Practical Application

Many commercial dairy heifer growers would like to maximize the use of corn silage and by-

products of the ethanol industry in the diets of replacement

heifers.

● This has created the need for ‘cutter’ forages that (ideally) exhibit:

- high DM yield

- high fiber (~ 70% NDF)

- low energy (45 – 50% TDN)

- high protein (~ 15% CP)

- low K (~ 1.5%)

22393962.31200

15434363.3900

0505066.0600

Grain505068.0300

Cutter Forage

(48% TDN)

Alfalfa Silage

(60% TDN)Corn Silage (72% TDN)

Energy Requirement,

TDNBodyweight,

lbs

------------- % of Dietary DM -------------

Source: P. C. Hoffman, University of Wisconsin

eastern gamagrasstropical corn

20

25

30

35

40

45

50

55

TDN

, %

B1 B2 B3 O1 O2 O3 O4 O5 O6 O7 O8 O9

Sample Number

Energy Density of Oat and Barley Straws

1) delayed harvest schedules

2) comparisons of straws

3) tropical corn

4) perennial warm-season grasses

Source: P.C. Hoffman, University of Wisconsin

Synchrony of Forage and Livestock Needs

All of these forages might be the “right forage”, it just depends.

Final Thoughts• Alfalfa and corn silage tend to

complement each other in heifer diets, and often do not allow for incorporation of other low-cost nutrients, especially those with relatively high energy densities.

• Use of significant proportions of corn silage may necessitate limit feeding or the use of an ‘energy diluting’ forage.

Final Thoughts

• Producers might consider being proactive in their harvest management of legumes and grasses – “dairy quality” is not necessarily helpful.

• Avoid being “boxed in”, where you have only “dairy quality” or low-energy forages available.

• Routinely test forages and have ration balanced (energy, protein) based on appropriate heifer size/weight.