Effects of retinoids on immune responses in birds

Pros and Cons of Dietary Vitamin A and Its Precursors in Poultry Health and Production: A Comprehensive Review

Vitamin A is a fat-soluble vitamin that cannot be synthesized in the body and must be obtained through diet. Despite being one of the earliest vitamins identified, a complete range of biological actions is still unknown. Carotenoids are a category of roughly 600 chemicals that are structurally related to vitamin A. Vitamin A can be present in the body in the form of retinol, retinal, and retinoic acid. Vitamins are required in minute amounts, yet they are critical for health, maintenance, and performing key biological functions in the body, such as growth, embryo development, epithelial cell differentiation, and immune function. Vitamin A deficiency induces a variety of problems, including lack of appetite, decreased development and immunity, and susceptibility to many diseases. Dietary preformed vitamin A, provitamin A, and several classes of carotenoids can be used to meet vitamin A requirements. The aim of this review is to compile the available scientific literature regarding the sources and important functions, such as growth, immunity, antioxidant, and other biological activities of vitamin A in poultry.

Nutritional significance of amino acids, vitamins and minerals as nutraceuticals in poultry production and health - a comprehensive review

Nutraceuticals have gained immense importance in poultry science recently considering the nutritional and beneficial health effects of their constituents. Besides providing nutritional requirements to birds, nutraceuticals have beneficial pharmacological effects, for example, they help in establishing normal physiological health status, prevent diseases and thereby improve production performance. Nutraceuticals include amino acids, vitamins, minerals, enzymes, etc. which are important for preventing oxidative stress, regulating the immune response and maintaining normal physiological, biochemical and homeostatic mechanisms. Nutraceuticals help in supplying nutrients in balanced amounts for supporting the optimal growth performance in modern poultry flocks, and as a dietary supplement can reduce the use of antibiotics. The application of antibiotic growth enhancers in poultry leads to the propagation of antibiotic-resistant microbes and drug residues; therefore, they have been restricted in many countries. Thus, there is a demand for natural feed additives that lead to the same growth enhancement without affecting the health. Nutraceuticals substances have an essential role in the development of the animals' normal physiological functions and in protecting them against infectious diseases. In this review, the uses of amino acids, vitamins and minerals as well as their mode of action in growth promotion and elevation of immune system are discussed.

Early Nutrition Programming (in ovo and Post-hatch Feeding) as a Strategy to Modulate Gut Health of Poultry

Healthy gastrointestinal tract (GIT) is crucial for optimum performance, better feed efficiency, and overall health of poultry. In the past, antibiotic growth promoters (AGP) were commonly used to modulate the gut health of animals. However, considering the public health concern, the use of AGP in animal feeding is banned or regulated in several jurisdictions around the world. This necessitates the need for alternative nutritional strategies to produce healthy poultry. For that, several alternatives to AGP have been attempted with some success. However, effective modulation of the gut health parameters depends on the methods and timing of the compound being available to host animals. Routinely, the alternatives to AGP and other nutrients are provided in feed or water to poultry. However, the GIT of the newly hatched poultry is functionally immature, despite going through significant morphological, cellular, and molecular changes toward the end of incubation. Thus, early growth and development of GIT are of critical importance to enhance nutrients utilization and optimize the growth of poultry. Early nutrition programming using both in ovo and post-hatch feeding has been used as a means to modulate the early growth and development of GIT and found to be an effective strategy but with inconsistent results. This review summarizes the information on in ovo and post-hatch-feeding of different nutrients and feeds additives and their effects on gut development, histomorphology, microbiology, and immunology. Furthermore, this review will provide insight on the future of early nutrition programming as a strategy to enhance gut health, thereby improving overall health and production so that the poultry industry can benefit from this technique.

Effects of inhalation exposure to a binary mixture of benzene and toluene on vitamin a status and humoral and cell-mediated immunity in wild and captive American kestrels

Benzene and toluene are representative volatile organic compounds (VOC) released during production, storage, and transportation associated with the oil and gas industry and are chemicals of concern, as they are released in greater and possibly more biologically significant concentrations than other compounds. Most studies of air pollution in high oil and gas activity areas have neglected to consider risks to birds, including top-level predators. Birds can be used as highly sensitive monitors of air quality and since the avian respiratory tract is physiologically different from a rodent respiratory tract, effects of gases cannot be safely extrapolated from rodent studies. Wild and captive male American kestrels were exposed for approximately 1 h daily for 28 d to high (rodent lowest-observed-adverse-effect level [LOAEL] of 10 ppm and 80 ppm, respectively) or environmentally relevant (0.1 ppm and 0.8 ppm, respectively) levels of benzene and toluene. Altered immune responses characteristic of those seen in mammalian exposures were evident in kestrels. A decreased cell-mediated immunity, measured by delayed-type hypersensitivity testing, was evident in all exposed birds. There was no effect on humoral immunity. Plasma retinol levels as measured by high-performance liquid chromatography (HPLC) analysis were decreased in wild and captive kestrels exposed to the rodent LOAEL for combined benzene and toluene. This study indicates that American kestrels are sensitive to combined benzene and toluene. The study also illustrates the need for reference concentrations for airborne pollutants to be calculated, including sensitive endpoints specific to birds. Based on these findings, future studies need to include immune endpoints to determine the possible increased susceptibility of birds to inhaled toxicants.

Respiratory diseases of gallinaceous birds

Respiratory conditions constitute many of the diseases affecting all avian species, including gallinaceous birds. Clinical signs and gross lesions of different respiratory diseases are often similar, and establishing a definitive diagnosis may require ancillary laboratory testing. Determination of a specific diagnosis allows practitioners to select the most effective therapies and to prescribe a management program that prevents recurrence.

Nutritional modulation of resistance to infectious diseases

Dietary characteristics can modulate a bird's susceptibility to infectious challenges and subtle influences due to the level of nutrients or the types of ingredients may at times be of critical importance. This review considers seven mechanisms for nutritional modulation of resistance to infectious disease in poultry. 1) Nutrition may impact the development of the immune system, both in ovo and in the first weeks posthatch. Micronutrient deficiencies that affect developmental events, such as the seeding of lymphoid organs and clonal expansion of lymphocyte clones, can negatively impact the immune system later in life. 2) A substrate role of nutrients is necessary for the immune response so that responding cells can divide and synthesize effector molecules. The quantitative need for nutrients for supporting a normal immune system, as well as the proliferation of leukocytes and the production of antibodies during an infectious challenge, is very small relative to uses for growth or egg production. It is likely that the systemic acute phase response that accompanies most infectious challenges is a more significant consumer of nutrients than the immune system itself. 3) The low concentration of some nutrients (e.g., iron) in body fluids makes them the limiting substrates for the proliferation of invading pathogens and the supply of these nutrients is further limited during the immune response. 4) Some nutrients (e.g., fatty acids and vitamins A, D, and E) have direct regulatory actions on leukocytes by binding to intracellular receptors or by modifying the release of second messengers. 5) The diet may also have indirect regulatory effects that are mediated by the classical endocrine system. 6) Physical and chemical aspects of the diet can modify the populations of microorganisms in the gastrointestinal tract, the capacity of pathogens to attach to enterocytes, and the integrity of the intestinal epithelium.

Effects and interactions of dietary levels of vitamins A and E and cholecalciferol in broiler chickens

Four experiments were conducted to determine the effects and interactions of feeding different levels of vitamins A, cholecalciferol (vitamin D3), and E on broiler chicks. In Experiment 1, chicks were fed marginal vitamin D3 (500 IU/kg) and increasing dietary levels of vitamin A (5,000, 10,000, 20,000, 40,000, 80,000, and 160,000 IU/kg). Bone ash was reduced by 10,000 IU/kg of vitamin A in the diet and at vitamin A levels above 20,000 IU/kg of diet body weight was reduced. In Experiment 2, two levels of vitamin A (1,500 and 15,000 IU/kg) and six levels of vitamin E (10, 500, 1,000, 2,500, 5,000, and 10,000 IU/kg) were added to the basal diet. High levels of vitamins A and E significantly (P < 0.001) reduced bone ash. The vitamin A x E interaction was significant (P < or = 0.05) for rickets. In Experiment 3, the same two levels of vitamin A as Experiment 2 and six levels of vitamin D3 (500, 1,000, 1,500, 2,000, 2,500, and 3,000 IU/kg) were added to the basal diet that contained 10,000 IU/kg of vitamin E. Body weight and bone ash were increased by increasing vitamin D3 with a corresponding reduction (P < or = 0.05) in rickets. In Experiment 4, three levels of vitamin A (1,500, 15,000, and 45,000 IU/kg), three levels of vitamin D3 (500, 1,500, and 2,500 IU/kg), and three levels of vitamin E (10, 5,000, and 10,000 IU/kg) were added to the basal diet. Significant negative responses (P < or = 0.05) to increasing dietary vitamin A were observed for bone ash, rickets, and plasma and liver vitamin E. A significant (P < 0.001) increase in bone ash and plasma calcium with a corresponding reduction in rickets was observed by increasing vitamin D3. Increasing dietary vitamin E adversely affected (P < or = 0.01) bone ash, plasma calcium, and plasma and liver vitamin A concentrations. These results indicate the need for making feed with the proper ratios of vitamins A, D3, and E.