Systematic comparison of the empirical and factorial methods used to estimate the nutrient requirements of growing pigs

Abstract

Empirical and factorial methods are currently used to estimate nutrient requirements for domestic animals. The purpose of this study was to estimate the nutrient requirements of a given pig population using the empirical and factorial methods; to establish the relationship between the requirements estimated with these two methods; and to study the limitations of the methods when used to determine the level of a nutrient needed to optimize individual and population responses of growing pigs. A systematic analysis was carried out on optimal lysine-to-net-energy (Lys : NE) ratios estimated by the empirical and factorial methods using a modified InraPorc R growth model. Sixty-eight pigs were individually simulated based on detailed experimental data. In the empirical method, population responses were estimated by feeding pigs with 11 diets of different Lys : NE ratios. Average daily gain and feed conversion ratio were the chosen performance criteria. These variables were combined with economic information to estimate the economic responses. In the factorial method, the Lys : NE ratio for each animal was estimated by model inversion. Optimal Lys : NE ratios estimated for growing pigs (25 to 105 kg) differed between the empirical and the factorial method. When the average pig is taken to represent a population, the factorial method does not permit estimation of the Lys : NE ratio that maximizes the response of heterogeneous populations in a given time or weight interval. Although optimal population responses are obtained by the empirical method, the estimated requirements are fixed and cannot be used for other growth periods or populations. This study demonstrates that the two methods commonly used to estimate nutrient requirements provide different nutrient recommendations and have important limitations that should be considered when the goal is to optimize the response of individuals or pig populations.

Precision feeding can significantly reduce lysine intake and nitrogen excretion without compromising the performance of growing pigs

“…In conventional phase feeding systems minimal feeding cost or for maximal revenue is often obtained with nutrient levels lower than those required for maximal population growth ). In the context of feeding populations of pigs, nutrient requirements should be seen as the balance between the proportion of pigs that are going to be overfed and underfed (Brossard et al, 2009;Hauschild et al, 2010;Pomar et al, 2014b).…”

Animal production for efficient phosphate utilization: from optimized feed to high efficiency livestock

“…Nutritional requirements can vary greatly between animals in a given population and each animal follows individual patterns during the course of growth. To maximize the desired population response, such as body weight gain or milk production, requirements are formulated to meet the demands of the lower third of the population, resulting in excess nutrient received by the majority of the animals and thus reducing their efficiency of nutrient utilization [15]. Daily feeding programs tailored to individual animals based on their individualized requirements may yield significant reductions in nutrient and P excretion.…”

Determination of protein and amino acid requirements of lactating sows using a population-based factorial approach

“…Recommendations for populations are often determined as a requirement of an average sow without considering the between-animal variation. When these recommendations are applied to populations exhibiting large between-animal variation, the requirement of a certain percentage of the population is not met (Brossard et al, 2009;Hauschild et al, 2010;Pomar et al, 2011), and the mean performance of the group will be lower than expected. Nutrient requirements vary greatly between animals of a given population and each animal follows individual patterns over time (Pomar et al, 2011).…”