Nutritional requirements of animal histidine

Histidine is an amino acid containing an imidazole heterocyclic ring. Like other amino acids, it is a component of protein structure and participates in animal protein synthesis. At the same time, it also participates in various physiological and biochemical processes in the body in various forms, including the composition of various physiological and biochemical active ingredients, the removal of intracellular oxides and participation in immune regulation. Therefore, histidine plays an important role in animal nutrition.

Histidine is an essential amino acid in animals. Since the animal body can synthesize histidine from common intermediate metabolites, histidine has always been considered as a non-essential amino acid. However, with the deepening of the research, it was found that the synthesis of histidine in young animals and infants could not meet the normal growth of the body (Kopple and Swendseid, 1975), even in adult animals, if not supplemented with histidine from food, The histidine synthesized in the body also does not meet the needs.

Histidine-deficient animals exhibit corresponding lack of symptoms, and many scholars have studied histidine deficiency. The symptoms of histidine deficiency are: 1 negative nitrogen balance; 2 serum albumin decline; 3 plasma and muscle free histidine decreased; 4 hemoglobin decreased; 5 hematocrit decreased; 6 muscle myofin content decreased; 7 The content of copper and zinc in whole blood decreased; 8 serum iron increased. After the histidine is added, the above symptoms are alleviated or eliminated. Therefore, in order to ensure the normal function of the body, it is necessary to take quantitative histidine from the diet. Therefore, although the body can synthesize histidine by itself, histidine is still an essential amino acid. Histidine has been listed as an essential amino acid for pigs and chickens.

The content of histidine in the histidine nutrient requirement is 0.2%-0.4%, while the protein feed is generally 0.6%-1.5%. The highest content is blood meal, and the lowest content is feather powder. Fuller et al. (1979) found that histidine in barley is probably the third limiting amino acid after lysine and threonine.

Brudevold and Southern (1994) reported that histidine was as good as isoleucine, tryptophan and valine in the low protein (12%) "sorghum-soybean" diet of 10 kg-20 kg piglets. The third limiting amino acid. Therefore, attention should be paid to the lack of histidine in low protein level diets. The contents of histidine in common feed ingredients and the relevant digestibility values ​​are shown in Table 1.

Easter and Baker (1977) used the nitrogen balance test to determine the histidine requirement of the first trimester sow. When histidine is less than 0.12%, nitrogen retention is inhibited, but the difference is not significant, so the requirement for histidine in pregnant sows is 0.12%; Burns et al. (1982) found that young dogs achieved optimal growth performance. The histidine required for nitrogen deposition was 0.21%; Quam et al. (1987) explored the histidine requirement for growth and hematopoiesis in young cats. When the histidine was 0.21%, the average daily gain, N The sedimentation and feed intake reached the highest value. When histidine was 0.3%, the hemoglobin and blood cell volume were the highest, and the 0.15%-0.30% histidine level in the diet was linearly related to the logarithm of plasma free histidine (r2). =0.99), so they suggested that the cat's histidine requirement is 0.30%; Wilson et al. (1980) suggested that the requirement for histidine in young cats was 0.37%, accounting for 1.54% of the dietary protein; There are few studies on the nutritional requirements of lysine. Several studies were conducted in the 1950s. However, because the number of animals used in the experiment is small and the growth level is low, the test results cannot correctly estimate the ammonia. Acid nutrient requirements. In 1968, Mitchell et al. used a homozygous diet with N retention as an indicator to estimate the histidine requirement of 10 kg piglets was 0.25%. However, there are only 2 pigs per treatment, and the restriction feeding method is adopted. Kim et al. (1983) indirectly estimated the requirement for histidine in piglets by using the effect of histidine levels in the diet on the oxidation rate of 14C-labeled phenylalanine. When histidine is more than 0.4%, the oxidation rate of phenylalanine is the lowest. When it is less than 0.4%, the oxidation rate of phenylalanine increases with the decrease of histidine level, indicating that the histidine is greater than 0.4%. The rate at which the acid is used for protein synthesis is not limited. Therefore, the recommended amount of histidine nutrition is 0.4%. With the introduction and practical application of the ideal protein concept, it has been recognized that the content of other amino acids must be considered when studying the nutritional requirements of each amino acid, especially the essential amino acids. Table 2 is the recommended ratio of histidine content in pigs and suitable ratios of histidine to lysine in several typical pig ideal protein models. The histidine content in the growing pig body is higher than the recommended value in the ideal protein model. The data of Chung and Baker (1992c) are derived from the results of Izquierdo et al. (1988). From the results of Izquierdo et al. (1988), the requirement for lysine and histidine is not higher than 100:30. Therefore, the appropriate ratio of histidine in the ideal protein model is worth further exploration. In addition, most of the studies used to establish the ideal protein model used a homozygous diet, and the required amount was the available value. In the actual use of the diet, the digestible or available histidine value should be used as much as possible.

Conclusion Although histidine is an essential amino acid, it is generally less prone to deficiency than other essential amino acids. Only the addition of synthetic histidine is required in special diets with lower protein. At present, people's research on the nutritional requirements of histidine is not very important (NRC, 1998), so there is very little data on this. Considering the various physiological functions of histidine, the restrictive order of histidine in animal actual diets, especially low-protein diets, is for further study in future studies.