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Considering the variability of growing pigs

Most Models for growth in pigs are currently deterministic, i.e. they consider only an average pig and not the group of individual pigs in their diversity. However, inclusion of variability among individuals in these models is required to better understand the effects of feeding strategies on growth and economic performance, and environmental impact but also on their variability. The knowledge of the variability structure of model parameters used in models such as in InraPorc^®  is required for this inclusion. Feeding strategies can then be evaluated in simulations to determine quickly and more accurately those conciliating production goals with environmental protection and allowing control of variability.

A virtual pig population

Data for daily feed intake and live weight of 1288 gilts and barrows from 10 different terminal crossbreeds reared in France and 10 batches (Ifip facilities, Romillé, France), were collected and analyzed. Each animal was characterized by five parameters describing the individual pig in the InraPorc model. Our results show that the covariance structure of these parameters differs from one group to another, a group being defined by the batch and sex x crossbreed. We propose a covariance pattern to represent a group of pigs through the combination of a generic covariance matrix of parameters, calculated as the median between matrices of each original group, distributions of parameters and a specific vector of parameters averages. Using a generator of virtual pigs based on this covariance pattern, a virtual population of 2000 pigs was generated to simulate the effect of the feeding strategy and feedstuff prices on average performance and its variability, and on nitrogen excretion. Our results show that using a two-phase strategy combined with a controlled feed restriction improves weight homogeneity, economic margin per pig, and excretion. An in vivo experiment confirmed the relevance of some simulation results.

Towards precision feeding systems

This work allows considering the inclusion of a population dimension in deterministic models and decision support tools such as InraPorc^®. This will help users (research, sector professionals) to study and propose on-farm innovative feeding strategies , meeting performance and environmental goals and considering / using variability among individual pigs.

This work was conducted as part of the thesis of Bertrand Vautier between 2009 and 2012 (funded by the French Ministry of Agriculture, Food, Fisheries, Rural Affairs and Spatial Planning) and in collaboration with the Ifip on behalf of the mixed technological unit (UMT) ‘‘Engineering for pig production systems’’.

For futher information

• Vautier B., N. Quiniou, J. van Milgen, L. Brossard. 2013. Accounting for variability among individual pigs in deterministic growth models. Animal 7: 1265-1273. (DOI)
• Quiniou, N., Vautier, B., Salaün, Y., Van Milgen, J., Brossard, L. (2013). Modélisation de l’effet de la stratégie alimentaire et du contexte de prix de matières premières sur les performances moyennes, leur variabilité et les rejets azotés à l’échelle d’une population de porcs. In: 45èmes Journées de la Recherche Porcine (p. 155-160). [lien]
• Vautier, B., Brossard, L., Van Milgen, J., Quiniou, N. (2012). Du porc à la bande : étude des liens entre paramètres individuels pour modéliser la croissance à l'échelle de la population. In: 44èmes Journées de la Recherche Porcine (p. 147-152). [lien]
• Vautier, B., Quiniou, N., Van Milgen, J., Brossard, L. (2011). Modélisation de la cinétique de consommation en fonction du poids chez le porc en croissance selon le mode d’expression de l’ingéré. In: 43èmes Journées de la Recherche Porcine (p. 139-140). [lien]
• Vautier, B., Quiniou, N., Van Milgen, J., Brossard, L. (2011). Modelling the dynamics of feed intake in growing pigs : interest for modelling populations of pigs. In: Book of abstracts of the 62nd annual meeting of the European federation of animal science (p. 105). EAAP Book of Abstracts, 17. [lien]