Assessment of statistical models describing individual and group response of pigs to threonine intake

Abstract

A nitrogen balance experiment was conducted to study the individual and group response of growing pigs to threonine (Thr) intake. A series of fifteen purified diets with increasing concentration of Thr was fed sequentially to nine pigs during a 15-d experimental period. The concentration of Thr ranged from 50 to 140% of its assumed requirement while other essential amino acids were given in a 25 % excess. N retention was related to Thr intake using rectilinear and curvilinear models. The quadratic-plateau model fitted the individual data significantly better (P=0.02) than the linear-plateau model. The R 2 statistic indicated that the group response of pigs to Thr intake was better described by the linear-plateau and quadratic-plateau models than by exponential, saturation kinetics or four-parameter logistic models. Significant differences (P=0.004) were found between individual plateau values in the linear-plateau model while the slopes of the regression lines did not differ. No significant correlation was found between the slope and plateau or breakpoint values of the linear-plateau model. Marginal efficiency of Thr utilization derived from the linear-plateau model was 0.67. In the quadratic-plateau model, marginal efficiency of Thr utilization was dependent on Thr intake and ranged from 0.77 (50% of requirement) to 0.42 (100% of requirement). Based on linear-plateau and quadratic-plateau models, daily requirement of Thr for a 45 kg pig was calculated to be 11.5 and 12.1 g, respectively.

Individual responses of growing pigs to threonine intake

“…The 5.2% coefficient of variation is consistent with the findings of published studies about the response of growing pigs to amino acid intake (Heger et al, 2007;Heger et al, 2008;Heger et al, 2009). This indicates that the maximum protein deposition rate also varies considerably among individuals, even when animals present homogenous characteristics (genetic strain, age, and sex) and are evaluated under the same environmental and health-challenged conditions.…”

Individual response of growing pigs to lysine intake

“…In our previous studies (Heger et al., 2007, 2008), the individual and group responses of growing pigs to sulphur amino acid or threonine intake were examined using N retention (NR) as the criterion of response. The studies were based on feeding a series of purified diets in quick succession in which the concentration of a limiting amino acid gradually increased by small steps from deficiency to excess.…”

“…Knowledge of population variability of these parameters can be used as a tool in optimizing cost‐revenue ratio under varying conditions (Bertolo et al., 2005) and may be useful in developing stochastic models simulating pig growth (Ferguson et al., 1997). Thus, the objective of the present experiment was to study individual and group responses of growing pigs to Lys intake using the sequential short‐term N balance method developed previously (Heger et al., 2007).…”

Prise en compte de la variabilité individuelle dans la modélisation de la réponse des porcs en croissance aux apports alimentaires

“…Pour l'obtention de valeurs individuelles de besoin, Heger et al (2007Heger et al ( , 2008Heger et al ( , 2009 ont utilisé une méthode de bilans azotés consécutifs de 24 heures chacun, en réponse à de petites augmentations de l'acide aminé limitant dans le régime. Après 4 jours d'adaptation au régime le plus carencé, chaque animal étudié reçoit consécutivement sur 15 jours, 15 niveaux d'apport de l'acide aminé étudié augmentant graduellement de 50 à 140% du besoin estimé.…”

“…L'ajustement d'un modèle quadratique plateau ou linéaire-plateau à la réponse de chaque individu permet d'obtenir le besoin en l'acide aminé étudié pour chaque porc et sa variabilité entre les animaux étudiés. Ces auteurs évaluent ainsi expérimentalement sur neuf femelles croisées Large White x (Large White x Landrace) le Coefficient de Variation (CV) du besoin en acide aminé (en valeur digestible standardisée) à 3% à 45 kg de Poids Vif (PV) pour la thréonine (Heger et al 2007), à 11% à 50 kg de PV pour la méthionine (Heger et al 2008) et à 10% à 47 kg de PV pour la lysine (Heger et al 2009).…”