Agriculture Reference
In-Depth Information
The first management change was to for-
mulate diets precisely to meet each animal
group's requirements for degradable and non-
degradable proteins and P (Rotz
et al
., 2011b).
The reduction in protein reduced the N
excreted in manure, which reduced ammonia
emissions from animal housing, manure stor-
age and following field application by about
8% (Table 10.1). Losses through nitrate leach-
ing and denitrification were also reduced by
about 10%. Overall, this provided an 8%
reduction in the total reactive N loss from the
production system. The reduction in P fed did
not have much effect on P runoff loss, but the
accumulation of excess P in the farm soil was
reduced by 45%. These feeding changes pro-
vided a small 3% reduction in greenhouse gas
emissions and carbon footprint. More precise
feeding was of benefit to the producer. The
reduction in purchased feed cost increased
annual farm profitability by US$35 per cow.
These simulation results illustrate that
more precise feeding to meet animal nutrient
requirements benefits both the environment and
the producer. This assumes that production is
not negatively affected by this change. Producers
often overfeed nutrients to reduce their risk of
loss of production. With accurate measurement
Table 10.1.
Simulated annual environmental and economic impacts of animal management on
a 3000-cow dairy farm in Idaho.
Reduced
replacement
rate
c
Precision
feeding
b
Improved
production
d
Base farm
a
Nutrient loss and balance (kg ha
−1
)
Nitrogen lost by volatilization
110.0
101.1
102.1
112.4
Nitrogen lost by leaching
10.5
9.4
9.5
11.1
Nitrogen lost by denitrification
132.6
119.2
120.1
140.1
Phosphorus loss by runoff
0.3
0.3
0.3
0.3
Soil phosphorus accumulation
13.9
7.7
12.4
16.7
Soil potassium accumulation
43.1
37.6
22.5
50.5
Sediment erosion loss
287
287
287
287
Ammonia emission (kg NH
3
per cow)
Animal housing
27.7
25.9
25.4
28.2
Manure storage
16.4
14.8
15.8
16.6
Field application
9.4
8.4
8.5
9.9
Total
53.5
49.2
49.7
54.7
Greenhouse gas emission (kg CO
2
e per cow)
Feed production
1011
974
958
1051
Animal
4335
4240
3887
4493
Manure storage and handling
2602
2519
2410
2715
Total
7948
7733
7255
8259
Reactive nitrogen footprint (g N kg
−1
milk)
4.74
4.35
4.45
4.46
Fossil energy footprint (MJ kg
−1
milk)
3.03
3.01
2.86
2.96
Carbon footprint (kg CO
2
e kg
−1
milk)
1.03
1.00
0.97
0.99
Production costs ($ per cow)
Net feed production and use
1877
1843
1744
2000
Manure handling
83
82
78
86
Animal management, milking, etc.
1087
1087
1085
1092
Total
3047
3012
2907
3178
Income from milk and animal sales (US$ per cow)
3711
3711
3646
4050
Net return to management (US$ per cow)
664
699
739
872
a
3000 cows plus 2600 replacement heifers on 1200 ha of cropland (800 ha of lucerne and 400 ha maize) annually
producing 10,000 kg of milk (3.5% fat) per cow.
b
Protein and phosphorus are fed more precisely, reducing requirements
by 10%.
c
Annual replacement rate of the lactating herd is reduced from 40% to 30%.
d
Through genetic improvement,
milk production is increased from 10,000 to 11,000 kg per cow.
