Dietary protein reduction improves the energetic and amino acid efficiency in lactating sows

Abstract

Strategies to mitigate the environmental impact of swine production are essential to contribute to the sustainability of the swine industry. Our work has focussed on the area of dietary crude-protein (CP) reduction with crystalline amino acid (CAA) supplementation to create diets containing a near ‘ideal’ amino acid (AA) balance, and to assess the environmental impact of feeding these diets to lactating sows. Additionally, with an increasing availability of CAA at competitive costs relative to feed-ingredient proteins, precise prediction of requirements of the less traditionally limiting AA such as histidine, isoleucine, leucine, phenylalanine and valine are ever more relevant. Prediction of AA requirements using modelling approaches is dependent on accurate estimates of AA efficiency of utilisation for milk-protein production. Aggressive reduction in dietary CP and CAA supplementation to improve dietary AA balance minimises urea-nitrogen (N) synthesis, N excretion and ammonia emission, without compromising lactation performance. Improving dietary AA balance increases energy, global N and AA efficiency of utilisation for milk production, and, in some cases, increases true milk protein and casein yield in peak lactation. The mechanisms by which enhanced AA balance improves nutrient efficiency include potentially increased extraction rate of AA by the mammary gland and reduced heat production. Individual AA efficiencies are dynamic, and, thus, estimating their maximum biological efficiency value (MBEV) is of critical importance for accurate prediction of AA requirements. We have estimated MBEV for each individual AA. Future dietary formulations using reduced CP diets to minimise N excretion and ammonia emission will require AA requirements based on MBEV estimates.