Post on 30-Sep-2020
transcript
Effect of stocking rate on performance,
diet selection and apparent total-tract
digestibility among heifers grazing cover
crops
B. R. Brunsvig*, D. W. Brake, A. J. Smart
and E. E. Grings
Land Usage Change
• U.S. Northern Great Plains
– 1,096,000 ha loss 2008 to 2012
• Iowa – 9,029 ha
• Minnesota – 5,042
• North Dakota – 4,012
• South Dakota – 10,983
– Total – 33,686 ha of new cropland (2011 to 2012)
Why The Change?
• Prices
– 2012 • Cattle- February Feeder USD $86.59 / kg
• Corn- August USD $7.63 / bu
– 2014 • Cattle- October Feeder USD $128.91 / kg
• Corn- April USD $4.71 / bu
– Current • Cattle- November Feeder Cattle USD $57.26 / kg
• Corn- July USD $3.53 / bu
Pasture Rent
0
50
100
150
200
250
2011 2012 2014 2015 2016
Do
lla
rs / h
a
USDA, NASS 2016
Impact on the cow-calf industry
• Segmented production of cattle and row crops.
• Could limit national cattle carrying capacity
• Increase Cow-calf production costs
Grazed vs Harvested Resources
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
Grass
Pasture
Corn Corn
Silage
Grass Hay Alfalfa
Hay
Alfalfa
Silage
Do
lla
rs / M
ca
l N
Em
U.S. Cow Feed Costs By Region
Short, USDA, 2001
0
20
40
60
80
100
North West South
Fe
ed
C
ost, U
SD
How To Extend The Grazing Season?
• Graze crop residue
• Graze cover crops
– U. S. Department of Ag says…
• A cover crop is a crop generally recognized by agricultural
experts as agronomically sound for the area for erosion
control or other purposes related to conservation or soil
improvement.
Increase in U.S. Cover Crops
Adapted from Watts, SARE, 2015
0
50
100
150
200
250
2008 2009 2010 2011 2012 2013 2014 2015 2016
ha
, 1
x1
03
Where
Adapted from Watts, SARE, 2015
North American Wheat Production
Australian Center for International Ag Research
Stocking Rate and Performance
Adapted from Ackerman et al.,2001
0.55
0.60
0.65
0.70
0.75
300 500 700 900
AD
G, k
g/d
Stocking Rate, kg/ ha
Stocking Rate and Performance
Adapted from Ackerman et al., 2001
45
50
55
60
65
70
75
80
85
300 500 700 900
Ga
in
/h
a, k
g
Kg steer / ha
Stocking Rate and Performance
45
55
65
75
85
0.58
0.63
0.68
0.73
300 400 500 600 700 800 900
AD
G (k
g)
Kg steer / ha
Adapted from Ackerman et al., 2001
Stocking Rate
Adapted from Mott, 1973
Gain per Animal (g)
Gain per Unit Area (G) max
G
0 G
max g
0 g
Optimum
Range
u
Undergrazing Overgrazing
n
Grazing Pressure
0 n
m n
Objective
• Determine effect of stocking rate among heifers grazing a
cover crop mix
– Diet selection
– Diet digestibility
– Performance
Experimental Design
• 48 weaned heifers
• 67% Annual Ryegrass, 20% Radish, 13% Turnip
– 48d
• 3, 4 or 5 heifers
– 1.7, 2.3, 2.9 AUM/ha
Forage composition
Forage Consumption
0
20
40
60
80
100
Beginning Middle End
% B
ra
ssic
a S
ele
cted
Low
Medium
High
Forage Consumption
0
10
20
30
40
50
60
70
80
Beginning Middle End
% G
ra
ss S
ele
cted
Low
Medium
High
Nutrient Selection
Time Contrasts
% DM Initial Intermediate Final Linear Quadratic
OM 82.0 84.6 81.2 0.45 <0.01
NDF 48.2 35.5 42.8 0.11 <0.01
ADF 33.6 32.8 34.1 0.82 0.61
Nutrient Selection
Time Contrasts
% DM Initial Intermediate Final Linear Quadratic
OM 82.0 84.6 81.2 0.45 <0.01
NDF 48.2 35.5 42.8 0.11 <0.01
ADF 33.6 32.8 34.1 0.82 0.61
Nutrient Selection
Time Contrasts
% DM Initial Intermediate Final Linear Quadratic
OM 82.0 84.6 81.2 0.45 <0.01
NDF 48.2 35.5 42.8 0.11 <0.01
ADF 33.6 32.8 34.1 0.82 0.61
Nutrient Selection
Time Contrasts
% DM Initial Intermediate Final Linear Quadratic
OM 82.0 84.6 81.2 0.45 <0.01
NDF 48.2 35.5 42.8 0.11 <0.01
ADF 33.6 32.8 34.1 0.82 0.61
Stocking Rate, AUM × ha-1 Contrasts
% DM 1.7 2.3 2.9 Linear Quadratic
OM 82.7 82.1 83.0 0.90 0.71
NDF 41.2 41.2 44.1 0.25 0.52
ADF 33.4 33.2 34.0 0.48 0.49
Nutrient Selection
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Digestibility
Stocking Rate, AUM × ha-1 Contrasts
Item 1.7 2.3 2.9 Linear Quadratic
DMI, kg 6.0 9.1 8.2 0.07 0.05
Digest., %
DM 67.8 83.3 79.7 0.01 0.02
OM 76.7 87.7 84.8 <0.01 <0.01
NDF 69.0 80.0 80.0 <0.01 0.03
ADF 74.1 83.7 80.5 0.12 0.08
Period ADG
Stocking Rate, AUM × ha-1 Contrasts
kg 1.7 2.3 2.9 Linear Quadratic
0-22d 0.3 0.1 0.1 0.05 0.24
22-48d 1.1 1.2 1.0 0.69 0.16
Period ADG
Stocking Rate, AUM × ha-1 Contrasts
kg 1.7 2.3 2.9 Linear Quadratic
0-22d 0.3 0.1 0.1 0.05 0.24
22-48d 1.1 1.2 1.0 0.69 0.16
Period ADG
Stocking Rate, AUM × ha-1 Contrasts
kg 1.7 2.3 2.9 Linear Quadratic
0-22d 0.3 0.1 0.1 0.05 0.24
22-48d 1.1 1.2 1.0 0.69 0.16
Cumulative ADG
Stocking Rate, AUM × ha-1 Contrasts
kg 1.7 2.3 2.9 Linear Quadratic
0-22d 0.3 0.1 0.1 0.05 0.24
Overall 0.7 0.6 0.6 0.15 0.78
Cumulative ADG
Stocking Rate, AUM × ha-1 Contrasts
kg 1.7 2.3 2.9 Linear Quadratic
0-22d 0.3 0.1 0.1 0.05 0.24
Overall 0.7 0.6 0.6 0.15 0.78