Low protein or reduced protein diets have been widely used in pig industry to save protein sources and reduce nitrogen excretion. In reduced protein diets, amino acids (AA) balance is crucial for pig’ s performance not to be compromised.
Currently amino acids balance is achieved by the supplementation of crystalline L-Lysine, L-methionine, L-threonine, -L-tryptophan, L-Valine and L-Isoleucine based on the ideal protein profile. In practice, if only adding first 4 limiting amino acids to reduced protein diets, it may result in lower plasma valine, isoleucine, histidine, and arginine. Other amino acids such as lysine, methionine, threonine, tryptophan might become surplus and cannot be used by pigs (Figure 1). Histidine is the seventh limiting AA in typical diets fed to swine and may require supplementation in reduced protein diets (Figure 2). Among cereals, barley has the lowest histidine contends and therefore, barley-based diets may result in histidine deficiency.
Histidine is an integral component of a broad set of tissues including skin, bone, ligaments, and muscle. It is a component of haemoglobin and important constitute of dipeptides anserine and carnosine. High concentrations of carnosine and anserine have been found in the brain and muscles because of its high antioxidant activity. It also stimulates the digestive secretion of gastrin, a hormone that is essential for digestion of dietary protein. Histidine deficiency could induce a decrease in amino acids oxidation and a decrease protein turnover.
Recommended standardized ileal digestible (SID) histidine to lysine ratio for pigs at 7 to 11 kg body weight from NRC (2012) is 0.34, which was based on growth performance and plasma histidine concentration. Recently, Cheng et al (2023) indicated that SID histidine to lysine between 0.35 and 0.41 in diets fed to nursery pigs at 7 to 11 kg body weight enhanced intestinal health and maximized concentrations of histidine-containing proteins.
Figure 1 Plasma amino acids concentration in standard and reduced protein diets.
Figure 2. The effect of further adding Valine, isoleucine and histidine on daily weight gain
A study compiled by our Redox Animal Nutritionists.