Modeling the effect of feeding strategy and feed prices on a population of pigs

Within a population of pigs, variation in performance and nutritional requirements can be important. Nutritionists elaborate feeding strategies that maximize economic return at the batch scale while (in some countries) accounting for N and P excretion. To evaluate the effect of feeding strategy and feed price on performance, its variability, economic return and environmental impact, a simulation study was carried out using both a virtual population of 2,000 gilts and barrows and the InraPorc® growth model. The 2,000 virtual animal profiles were generated randomly from the average of five parameters that describe growth and feed intake, while using the covariance structure of parameters obtained in a preliminary study. The effects of factors such as feed restriction, number of diets used and amino acids level in each diet were simulated with diets formulated using the least-cost principle. Five different contexts of feedstuff prices, corresponding to average prices recorded for five harvesting campaigns (2005/06 to 2009/10) were used. Calculations were performed for the 2,000 individual animals to obtain performance at the average final BW of 115 kg for the group. With reference to the French payment grid, carcass value was calculated using the final individual carcass weights and lean meat contents. Economic return was calculated as the difference between carcass value and the costs of feed and labor. Results suggest that the variability of final BW was reduced with an increased supply of amino acids. Feed restriction had a greater impact on variability. The price of feed ingredients influenced the optimum level of amino acids for economic return and corresponding N output. These calculations should be performed monthly to adapt nutrient supplies to the economic context