The role of vitamin A in non-ruminant immunology

Abstract

Vitamin A (retinol) is an essential micronutrient with a crucial role in the immune system of non-ruminant animals, such as swine and poultry. It includes three chemical compounds with distinct properties and functions in the body: retinol, retinal, and retinoic acid. In monogastric feed, vitamin A is primarily present in the form of retinyl esters. The metabolism of dietary vitamin A esters involves their conversion to retinol, which is then transported to different tissues and cells for further metabolism into active forms such as retinoic acid. These active forms of vitamin A have been found to play a crucial role in regulating both innate and adaptive immune responses. Specifically, they are involved in the differentiation, proliferation, and function of immune cells such as T and B lymphocytes, as well as dendritic cells. Vitamin A deficiency can lead to impaired cellular immunity, reduced antibody production, and consequently an increased susceptibility to infections. In swine and poultry, hypovitaminosis A can also affect gut-associated lymphoid tissues, leading to gut-related health problems and compromised growth performance. On the other hand, vitamin A supplementation has been shown to have immunomodulatory effects on non-ruminant immune responses. By administering or supplementing retinol, immune cell proliferation, antibody production, and cytokine secretion can be enhanced, which can ultimately result in improved immune function and disease resistance. Therefore, vitamin A has potential applications as an immuno-micronutrient for improving health and preventing diseases in swine and poultry. However, the optimal dosage and timing of vitamin A supplementation need to be carefully determined based on the specific requirements of different non-ruminant species and their production stages. Overall, a better understanding of the role of vitamin A in non-ruminant nutritional immunology could have significant implications for animal health and productivity and could inform the development of effective dietary strategies to optimize immune function and prevent diseases in swine and domestic fowl. This review paper aims to offer valuable insights into the role of vitamin A in the nutritional immunology of non-ruminants while also emphasizing the current gaps in knowledge and potential areas for further research.

Pet Wellness and Vitamin A: A Narrative Overview

“…The metabolic process of vitamin A in carnivores entails a sophisticated and multiphase mechanism involving various enzymes and pathways. Initially present as retinyl esters, such as retinyl acetate, vitamin A undergoes hydrolysis facilitated by pancreatic lipases in the small intestine [5,42]. This enzymatic activity liberates retinol, which then forms mixed micelles upon combining with other lipids and bile salts, thus promoting efficient absorption by enterocytes ([43]; Figure 2).…”

“…Within this section, the preformed vitamin A is integrated into chylomicrons, lipid-containing particles, and transported via the lymphatic system to the liver [46]. esters, such as retinyl acetate, vitamin A undergoes hydrolysis facilitated by pancreati lipases in the small intestine [5,42]. This enzymatic activity liberates retinol, which then forms mixed micelles upon combining with other lipids and bile salts, thus promoting efficient absorption by enterocytes ([43]; Figure 2).…”

“…Veterinarians, pet owners, and researchers are progressively acknowledging the significance of these organic compounds in animal well-being and longevity, given their indispensable role in physiological functions [1][2][3][4]. Vitamins, functioning as crucial components in the complex machinery of life, serve diverse roles, with vitamin A being notably versatile, involved in vision, immune system modulation, cellular differentiation, and reproduction [5]. Noteworthily, vitamin A is considered by many veterinary nutritionists to be the most important vitamin [6].…”

Stability of vitamin A at critical points in pet-feed manufacturing and during premix storage

“…Vitamin A is an important micronutrient required by mammals for maintaining good immune responses, epithelial integrity, body growth and development, good vision, and healthy reproductive function ( 1 ). Hypovitaminosis A leads to distortion of early offspring development, vision impairment, compromised cellular immune responses, and diminished antibody synthesis ( 2 ). This condition also induces heightened oxidative stress levels, further impacting the growth and overall well-being of animals ( 3 ).…”

“…These factors encompass elements such as the composition of their diet, their age, and their state of health ( 4 ). Commonly, when formulating diets, the inherent levels of vitamin A and carotenoids present in feed ingredients are often overlooked due to practical considerations ( 2 , 5 ). Instead, retinyl acetate is supplemented in the diet to fulfill the overall retinol requirement for animal nutrition.…”