Modelling of manure production by pigs and NH3, N2O and CH4 emissions. Part I: animal excretion and enteric CH4, effect of feeding and performance

Abstract

A mathematical model was developed from literature data to predict the volume and composition of pig's excreta (dry and organic matter, C, N, P, K, Cu and Zn contents), and the emission of greenhouse gases (CH 4 and CO 2 ) though respiration and from the intestinal tract, for each physiological stage (post-weaning and fattening pigs and lactating and gestating sows). The main sources of variation considered in the model are related to animal performances (feed efficiency, prolificacy, body weight gain, etc.), to water and nutrient intakes and to housing conditions (ambient temperature). Model predictions were validated by using 19 experimental studies, most of them performed in conditions close to those of commercial farms. Validation results showed that the model is precise and robust when predicting slurry volume ( R 2 5 0.96), slurry N ( R 2 5 0.91), P ( R 2 5 0.95) and to a lesser extent dry matter ( R 2 5 0.75) contents. Faeces and urine composition (minerals and macronutrients) can also be precisely assessed, provided the composition and the digestibility of the feed are well known. Sensitivity analysis showed strong differences in CH 4 emission and excretion amounts and composition according to physiological status, animal performance, temperature and diet composition. The model is an efficient tool to calculate nutrient balances at the animal level in commercial conditions, and to simulate the effect of production alternatives, such as feeding strategy or animal performance, on excreta production and composition. This is illustrated by simulations of three feeding strategies, which demonstrates important opportunities to limit environmental risks through diet manipulations.

Modelling of manure production by pigs and NH3, N2O and CH4 emissions. Part II: effect of animal housing, manure storage and treatment practices

“…This model would further support the development at the pig unit level, including a first model predicting animal excretion (Rigolot et al, 2010). The objective of this paper is to present the building of the model, with an original approach based on a mix of expert judgement, reference methods, mechanistic models and literature surveys, which could be used in other contexts.…”

“…Animal housing and outside storage includes two main options: slurry or solid manure management, which are presented separately in this paper. Inputs of the animal housing step are animal excretion (described in Rigolot et al, 2010) and litter. Inputs of the outside storage step are rain and manure transferred from the animal housing.…”

“…It was estimated as the difference of measured N in slurry of pigs in 52 experiments and a simulation of raw N excretion (Dourmad et al, 1999;Rigolot et al, 2010). Factor (17/14) aims at converting the results into kg NH 3 .…”

“…VS is an input of the model calculated from excreted OM (given by part I, Rigolot et al, 2010) and B 0 is taken from IPCC (2006). To integrate farmer practices, specific MCF are calculated for slurry management by modulating IPCC default value by temperature and storage time inside and outside the building.…”

“…The same animal excretion is used as input for the six scenarios. It has been obtained for a growing period from 30 to 110 kg body weight with 'standard' feeding strategy and performance parameters, as defined in the companion paper (raw excretion per pig: volume 5 384 l, N 5 3.82 kg, P 5 5.8 kg, K 5 16.2 kg, Cu 5 5.6 g and Zn 5 32.6 g Rigolot et al, 2010).…”