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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