Phosphorus and nitrogen excretion of Finnhorse mares with typical Finnish
diets
S. Särkijärvi and M. Saastamoinen
MTT Equine Research Finland
Background
• Environmental sustainability has been an important topic in agriculture for some years now
• Also equine sector has to start making responsible decisions and taking actions to protect environment
• But there is a lack of relevant information which impedes the development of appropriate practices and legislation
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Challenging manure management
• Manure disposal has become a problem in many areas and it is the biggest environmental factor
• Manure is not just cost but should be seen as a resource
• Estimated yearly horse manure production in Finland 800.000 m3
• Primary use in plant production • Manure from the stables can be
controlled, but nutrient losses from paddocks or outdoor areas are not very well managed
• Nutrients that are not utilized by plants are in the risk of leaking into water systems
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Enhancing nutrient cycle
• Efforts have been made to improve the accuracy and efficiency in poultry, pig and cattle feeding
• There is a potential for more precise feeding strategy and optimized feed efficiency also in horses
• However, the tools are partly different and must be created
• The project is aimed to gain information on the amount of nutrients produced, to evaluate the effect on environment and find ways to enhance nutrient recycling in equine sector 4
Material and methods
• Six Finnhorse mares were used in a digestibility trial
• Unbalanced 6 x 4 Latin square • 3-week periods with 5-day
collection of faeces and urine • Typical Finnish diets were selected
– Hay 100% – Haylage 100% – Hay 80% + Oats 20% – Hay 60% + Oats 40% – Hay 80% + Concentrate 20% – Hay 60% + Concentrate 40%
• Output of nutrients (N & P), nutrient availability for plants evaluated
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Results – production of faeces and manure
• Feed consumption in average 7.4 kg DM
• Faeces production 11.5 - 19.4 kg • Yearly production 5.7 tn (4.2 -
7.1 tn) • Partly lost in the ground – to
paddock and pastures • Up to 80% of manure is bedding
material • There can be considerably
amounts of nutrients – 8-9 g Nitrogen/kgDM in peat and
straw – 0.3 g Phosphorus/kgDM in peat and
1.4 grams in straw – In wood chips only traces of N and P
but 8.5 g K/kgDM
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Results – P and N outputs
• P concentration in faeces 5.3 – 7.9 g/kgDM
• The daily phosphorus excretion averaged in 21 grams meaning a 7.6 kg P load to environment yearly
• In grass production studies in MTT 16 kg P/ha has been producing 95% from the maximum sward mass – meaning the yearly manure production from two horses
• N concentration 12.2 – 16.5 g/kgDM • The average loss of nitrogen in
faeces was 46.3 g/d resulting a total loss of 16.9 kg nitrogen in a year
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Results – P and N outputs
• Only small amounts of P (3.3 mg/kg) was discovered in urine • N concentration in urine averaged in 6.8 g/kg (sd 1.69) • Urine excretion was estimated from creatinine concentration
(Meyer & Staderman, 1990) • P was mainly excreted in faeces and the P excretion in urine
is negligible (~0.05 g/d) • On the other hand, urine is the main excretion route to N
with a daily output of 100 grams • To sum up both excretion routes we conclude with the yearly
excretion of
– 7.6 kg Phosphorus – 53.4 kg Nitrogen
• Since urine is responsible for 68% of the nitrogen output it
makes it very important to choose a bedding material which is capable to retain nitrogen efficiently
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Results – P solubility
• From the phosphorus excretion (21 g faeces) on average 88% is in soluble form
• Solubility ranged from 68 to 100% • When the soluble P excretion was calculated in relation to
total P excreted or P intake the least amount of soluble P was produced by the diets with concentrate (P<0.05: Hay + Oats 20%)
• The effect of diets on the P solubility is also find in milking cows (Kebreab et al. 2002)
• P solubility affects the availability of P to plant production, since plants only use the soluble form
• When P is not taken up by plants there is a risk of leakage to the water systems, risk is growing when the solubility of P rises
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Conclusions: Faeces is the main excretion route for P and urine for N. Yearly outputs 53.4 kg Nitrogen and 7.6 kg Phosphorus. Most of the P in faeces is in soluble form. Diet can effect to the solubility of P in faeces.
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