Pigs are among the most important farm animals for meat production worldwide. In order to meet the amino acid requirements of the animals, pigs rely on the regular intake of proteins and amino acids with their feed. Unfortunately, pigs excrete about two thirds of the used protein, and production of pork is currently associated with a high emission of nitrogen compounds resulting in negative impacts on the environment. Thus, improving protein efficiency in pigs is a central aim to decrease the usage of protein carriers in feed and to lower nitrogen emissions. This is necessary as the supply of plant protein sources is limited by the yield and the cultivable acreage for protein plants. Strategies to increase protein efficiency that go beyond the known feeding options have to be investigated considering the characteristics of the individual animals. This requires a deep understanding of the intestinal processes including enzymatic activities, capacities of amino acid transporters and the microbiome. This review provides an overview of these physiological factors and the respective analyses methods.
Keywords: amino acids; gastrointestinal tract; pigs; proteases; protein utilization; transporter.