POULTRY AND LIVESTOCK HOUSING WITH SOLID WASTE MANAGEMENT
Richard S. Gates
Professor and Chair, Biosystems and Agricultural Engineering Department
University of Kentucky, Lexington KY 40546-0276 USA
Scope of the problem: Protein in animal feed is 6.25% Nitrogen (N). About 45% of N consumed by a
broiler is converted to animal protein, with the remainder as waste. Gross feed conversion ratios (FCR) for
broiler chickens are 1.8 to 2 kg feed/kg animal; thus a 4 lb broiler consumes 8 lbs of feed at roughly 20%
protein content, i.e. about 0.1 lb N and excretes about 0.055 lb N. A typical broiler house contains 25,000
birds, with 6 flocks raised per year; thus excreted N is on the order of 8,250 lb N per house. U.S. broiler
production (1999) was 8.1 billion birds (40.8 billion lb), or roughly 4.50 million tons of excreted N to be
managed.
Excreted N is lost to the environment via gaseous volatilization in the form of ammonia (NH3) and nitrous
oxide (N2O). NH3 volatilization from solid waste decreases its fertilizer value; the rate increases with higher
crude protein (CP) in the diet and with increased litter pH, moisture content and temperature. However, these
relations are complicated because the process is affected by the microbial populations that cause the
biochemical conversion.
The graphs below illustrate how litter N (maximum NH3, and total ammoniacal nitrogen, TAN) and litter
moisture content varied over 5 flocks of broilers fed 4 different CP levels on re-used wood shavings litter.
These data demonstrate that both NH3 and TAN are affected by dietary CP; the importance of ventilation
system management is also seen to be critical for controlling litter moisture content, and thus indirectly NH3
volatilization.
New of future technologies for reducing N loss: The following items are suggested for discussion:
• Improving our knowledge base - Applied research on management techniques and building systems are
needed to develop descriptive and predictive system models
• Develop standards for measurements.
• Dietary manipulation - Hypothesis: a well-balanced diet matching animal (bird) requirements retains
maximum N for conversion and thus minimizes excreted N. Three of the four diets in the graphs below
resulted in nearly identical bird performance.
• Advanced environment controls and systems –
Hypothesis 1: real-time monitoring of solid waste properties can be used in model-based feedback control
systems to improve N retention.
3500
a
Hi CP
2:1 Hi:Low
1:2 Hi:Low
Low CP+AA
150
a
125
100
b
75
bc
50
a
cd
ab
ab
c
25
c
d
ns
b
ns
0
0.30
a
Hi CP
2:1 Hi:Low
1:2 Hi:Low
Low CP+AA
3000
2500
a
2000
1500
a
bb
p<0.1
a
b
b
b
ns
ns
bb
1000
500
0
1
2
3
4
5
Flock Number on Litter
Moisture Content
175
TAN (ppm)
Equilibrium NH3 (ppm)
Hypothesis 2: retention and management of N in stored manure/waste systems can be optimized with modelbased (feedforward) controllers, such as fuzzy inference systems and adaptive controls technology.
Hi CP
2:1 Hi:Low
1:2 Hi:Low
Low CP+AA
a
0.25
0.20
a
b
bc
a
ab
bc
c
ns
b
bc
c
c
ns
0.15
0.10
1
2
3
4
5
Flock Number on Litter
1
2
3
4
5
Flock Number on Litter