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 2
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 m 3 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 3
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 5
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 6
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 7
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 8
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 9
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. 10