A Novel Estimation of Unobserved Pig Growth Traits for the Purposes of Precision Feeding Methods

Abstract

Recent technological advances make it possible to deliver feeding strategies that can be tailored to the needs of individual pigs in order to optimise the allocation of nutrient resources and contribute toward reducing excess nutrient excretion. However, these efforts are currently hampered by the challenges associated with: (1) estimation of unobserved traits from the available data on bodyweight and feed consumption; and (2) characterisation of the distributions and correlations of these unobserved traits to generate accurate estimates of individual level variation among pigs. Here, alternative quantitative approaches to these challenges, based on the principles of inverse modelling and separately inferring individual level distributions within a Bayesian context were developed and incorporated in a proposed precision feeding modelling framework. The objectives were to: (i) determine the average and distribution of individual traits characterising growth potential and body composition in an empirical population of growing-finishing barrows and gilts; (ii) simulate the growth and excretion of nitrogen and phosphorus of the average pig offered either a commercial two-phase feeding plan, or a precision feeding plan with daily adjustments; and (iii) simulate the growth and excretion of nitrogen and phosphorus across the pig population under two scenarios: a two-phase feeding plan formulated to meet the nutrient requirements of the average pig or a precision feeding plan with daily adjustments for each and every animal in the population. The distributions of mature bodyweight and ratio of lipid to protein weights at maturity had median (IQR) values of 203 (47.8) kg and 2.23 (0.814) kg/kg, respectively; these estimates were obtained without any prior assumptions concerning correlations between the traits. Overall, it was found that a proposed precision feeding strategy could result in considerable reductions in excretion of nitrogen and phosphorus (average pig: 8.07 and 9.17% reduction, respectively; heterogenous pig population: 22.5 and 22.9% reduction, respectively) during the growing-finishing period from 35 to 120 kg bodyweight. This precision feeding modelling framework is anticipated to be a starting point toward more accurate estimation of individual level nutrient requirements, with the general aim of improving the economic and environmental sustainability of future pig production systems.

Keywords: Bayesian inference; body composifion; individual traits; nitrogen excretion; phosphorus excretion; pigs; precision feeding.

Figure 1

Scatterplots of the estimated traits for each individual pig in the population: (A) mature bodyweight (BW_m) vs. inverse of daily growth rate BB; (B) ratio of lipid to protein weights at maturity $(L_m/N_m^{*})$ vs. B; (C) mature protein weight ($N_m^{*}$) vs. B; (D) mature lipid weight (L_m) vs. B; (E) initial protein weight ($N_{in}^{*}$) vs. B; (F) initial lipid weight (L_in) vs. B.

Figure 2

Estimated nutritional composition of the feeds in either two-phase feeding strategy (dashed black line, Scenario 1) or precision feeding strategy (solid red line; Scenario 2) offered to the average pig in terms of: (A) digestible protein (g/kg); (B) digestible phosphorus (g/kg); (C) effective energy (MJ/kg); estimated daily nutrient requirement for maintenance and growth of the average pig in terms of: (D) digestible protein (g/d); (E) digestible phosphorus (g/d); (F) effective energy (MJ/d). For a detailed description of the simulated scenarios, see section Simulated Feeding Scenarios.

Figure 3

Estimated nutritional composition of the feeds in either two-phase feeding strategy (dashed black line, Scenario 3) or precision feeding strategy (solid lines; Scenario 4) given to a pig population in terms of: (A) digestible protein (g/kg); (B) digestible phosphorus (g/kg); (C) effective energy (MJ/kg); estimated daily nutrient requirement for maintenance and growth of each of the thirty-two pigs in the population in terms of: (D) digestible protein (g/d); (E) digestible phosphorus (g/d); (F) effective energy (MJ/d). For a detailed description of the simulated scenarios, see section Simulated Feeding Scenarios.

Figure 4

Boxplots of: (A) the individual daily nitrogen excretion (g/d); and (B) the individual daily total phosphorus excretion from two-phase feeding strategy or precision feeding strategy offered either to the average pig (Avrg) or each of the thirty-two pigs in the population (1–32). For a detailed description of the simulated scenarios, see section Simulated Feeding Scenarios.