Utilization of protein-bound or crystalline amino acids for protein deposition, growth and carcass composition of growing pigs in relation to sustainable production
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One of the current challenges for pork producers is finding solutions to reduce nitrogen (N) excretion and ammonia emission to the environment. Excessive levels of dietary crude protein (CP) is the main contributing factor for high level of N excretion in pigs. Advances in understanding protein and amino acids (AA) digestibility and utilization of feedstuffs have been made in the last few decades. It is now accepted that formulating diets by reducing dietary CP level and adding crystalline amino acids (CAA) is an effective way to reduce N excretion. Increased availability of CAA such as Lys, Met, Thr, Trp, Val and Ile allows swine nutritionists to further reduce dietary CP level. In the last decades, several studies have been conducted evaluating the effects of lowering CP level in pig diets. In general, optimal performance, carcass quality and retained N of pigs are achieved when adequate amount of all AA on the standardized ileal digestible (SID) basis and net energy (NE) are balanced in the low CP diets. The use of CAA in low CP diets sometimes resulted in reduced pig performance compared with intact protein diets. The main reasons for such inconsistent results are due to the deficiency of the next limiting AA (Val and Ile) and insufficient amount of non-essential AA in the low CP diets with high level of CAA supplementation. On average, 1%-unit reduction in dietary CP results a reduction in total N excretion of about 9% in growing pigs, which significantly contributes towards sustainable pork production.