Determination of N, P, K, Cu and Zn in pig manure at spreading in French pig farms
Résumé
The objective of this work was to contribute to a proposal for updated French references for N, P, K, Cu and
Zn contents in pig manure at spreading. They are calculated according to a balance approach in agreement with international recommendations. Nutrient excretion is calculated as the difference between nutrient intake and retention. Body retention is determined according to prediction equations derived from the scientific literature. For nutrients without gaseous emissions (P, K, Cu and Zn) nutrient amount in manure at spreading is calculated as the amount excreted plus, in case of litter bedding, the amount in litter substrate. For N, the amount in manure is calculated considering gaseous losses from housing and during storage, with specific emission factors for each chain of manure collection and storage. A first set of average reference values is determined according to a Tier2 approach. Two feeding strategies, either conventional or improved (ie reduced in crude protein and total phosphorus) and three types of manure management: either slatted floor with slurry, slatted floor with V-shaped scrapper under the floor and solid-liquid phase separation, or accumulated straw or sawdust bedding, with or without composting of the solids, are considered. Animal performance is calculated according the French pig farm performance database (1,750 farms). The reference values are expressed per animal and per year for sows, including piglets until weaning, and per animal produced for weaners and fattening pigs. Total farm output is then calculated according to the average number of sows in the farm and the number of piglets and fattening pigs produced each year. The second reference is determined according to a simplified modeling approach (BrsPorc), in agreement with the Tier3 approach. This allows a more precise determination of the nutrient flow according to the actual performance, feeding strategy and manure management in the farm. This approach requires the collection of additional information especially on feed
intake and feed composition, the number of sows and the number of piglets and fattening pigs produced each year. Calculation tools using this approach are available (http://www.rmtelevagesenvironnement.org).