Excess dietary tryptophan mitigates aflatoxicosis in growing quails

Immunoregulatory and antioxidant properties of tryptophan in quail chick

A dose-response assay was carried out to investigate the effects of graded levels of dietary tryptophan (Trp) on blood variables, immunity, and meat quality in quail chicks during the last two weeks of the growing period. A total of 420 21-day-old quail chicks were randomly distributed across the seven experimental groups (i.e., 2.12, 2.25, 2.38, 2.51, 2.64, 2.77, and 2.90 g Trp/kg of diet) with four pen replicates of 15 birds each. Blood variables, including uric acid (UA), albumin (ALB), and triglycerides (TG), responded inversely to increasing dietary Trp (P < 0.001). The concentration of aspartate aminotransferase (AST) in serum, the relative weight of bursa of Fabricius (BF), immunoglobulin G (IgG), water holding capacity (WHC), and antigen production against the sheep red blood cells (SRBC) increased with increasing dietary Trp (P < 0.001). In contrast, the concentration of malondialdehyde (MDA) and drip loss in meat samples decreased with increasing dietary Trp (P < 0.001). The best models for optimal dietary Trp were identified based on a statistical merit basis known as the model accuracy index (δ). The estimated dietary Trp for optimizing ALP, UA, total protein (TP), TG, SRBC, IgG, BF, drip loss, WHC, and MDA were obtained at 2.347, 2.371, 2,372, 2.485, 2,691, 2.738, 2.306, 2.359, 2.247, and 2.500 g/kg of diet, respectively. Principal component analysis showed that UA, TG, IgG, and drip loss had a higher association with dietary Trp rather than other responses. Considering the high δ and eigenvalues of the models, the best estimation of dietary Trp level required for the optimization of the studied traits in quail chicks would be 2.738 g Trp/kg of diet, which was significantly higher than that recommended for the quail performance by NRC (1994).

Ochratoxin A induces abnormal tryptophan metabolism in the intestine and liver to activate AMPK signaling pathway

BACKGROUND

Ochratoxin A (OTA) is a mycotoxin widely present in raw food and feed materials and is mainly produced by Aspergillus ochraceus and Penicillium verrucosum. Our previous study showed that OTA principally induces liver inflammation by causing intestinal flora disorder, especially Bacteroides plebeius (B. plebeius) overgrowth. However, whether OTA or B. plebeius alteration leads to abnormal tryptophan-related metabolism in the intestine and liver is largely unknown. This study aimed to elucidate the metabolic changes in the intestine and liver induced by OTA and the tryptophan-related metabolic pathway in the liver.

MATERIALS AND METHODS

A total of 30 healthy 1-day-old male Cherry Valley ducks were randomly divided into 2 groups. The control group was given 0.1 mol/L NaHCO3 solution, and the OTA group was given 235 μg/kg body weight OTA for 14 consecutive days. Tryptophan metabolites were determined by intestinal chyme metabolomics and liver tryptophan-targeted metabolomics. AMPK-related signaling pathway factors were analyzed by Western blotting and mRNA expression.

RESULTS

Metabolomic analysis of the intestinal chyme showed that OTA treatment resulted in a decrease in intestinal nicotinuric acid levels, the downstream product of tryptophan metabolism, which were significantly negatively correlated with B. plebeius abundance. In contrast, OTA induced a significant increase in indole-3-acetamide levels, which were positively correlated with B. plebeius abundance. Simultaneously, OTA decreased the levels of ATP, NAD+ and dipeptidase in the liver. Liver tryptophan metabolomics analysis showed that OTA inhibited the kynurenine metabolic pathway and reduced the levels of kynurenine, anthranilic acid and nicotinic acid. Moreover, OTA increased the phosphorylation of AMPK protein and decreased the phosphorylation of mTOR protein.

CONCLUSION

OTA decreased the level of nicotinuric acid in the intestinal tract, which was negatively correlated with B. plebeius abundance. The abnormal metabolism of tryptophan led to a deficiency of NAD+ and ATP in the liver, which in turn activated the AMPK signaling pathway. Our results provide new insights into the toxic mechanism of OTA, and tryptophan metabolism might be a target for prevention and treatment.

Response surface model to illustrate the benefits of tryptophan, melatonin, and N,N-dimethylglycine in quail chicks exposed to aflatoxin B1

A dose-response assay in a central composite design platform was conducted to investigate the responses (performance, immunity, and meat quality) of quail chicks to dietary tryptophan (Trp), melatonin (MEL), and N,N-dimethylglycine (DMG) exposed to aflatoxin B1 (AFB1). A total of 1,275 quail chicks were randomly allotted to 85-floor pens consisting of 17 treatments with 5 replicates and 15 birds per each pen. Dietary MEL and DMG had a different effect on growth rate and interacted with dietary Trp and AFB1 during the first 4 wk of age, while their effect disappeared at the last week of the experiment. Dietary Trp and AFB1 were only significant on the gain of quail chick after d 28 of the assay. During the second and third weeks of age, the reduction in feed intake caused by AFB1 attenuated by dietary MEL and DMG and dietary Trp profoundly affects feed intake in the last 2 wk of the experiment. Dietary MEL and DMG were effective on feed conversion ratio (FCR) during the second and third weeks of age. AFB1 decreased breast meat yield (BMY) and thigh meat yield (TMY), but the inclusion of either MEL or DMG removed the adverse effects of AFB1. Dietary Trp increased BMY, but it did not affect TMY. Increasing dietary Trp linearly increased the Lactobacillus bacteria (LAB) population, and AFB1 negatively impacts the LAB population. The inclusion of dietary DMG removed that negative effect on LAB. Although AFB1 decreased the antibody production against SRBC-antigen, increasing dietary Trp in intoxicated quails increased the plasma antibody in SRBC-challenged birds. At low levels of dietary Trp (0.15-0.19%), the addition of DMG increased malondialdehyde (MDA) production while increasing Trp reversed this adverse situation. In conclusion, these supplements may interact with AFB1 in younger chicks, and dietary Trp and AFB1 have a significant impact on the growth performance of quail chicks during the fifth and sixth week of age.

Aflatoxin B1: metabolism, toxicology, and its involvement in oxidative stress and cancer development

Aflatoxins are a class of carcinogenic mycotoxins produced by Aspergillus fungi, which are widely distributed in nature. Aflatoxin B1 (AFB1) is the most toxic of these compounds and its metabolites have a variety of biological activities, including acute toxicity, teratogenicity, mutagenicity and carcinogenicity, which has been well-characterized to lead to the development of hepatocellular carcinoma (HCC) in humans and animals. This review focuses on the metabolism of AFB1, including epoxidation and DNA adduction, as it concerns the initiation of cancer and the underlying mechanisms. In addition to DNA adduction, inflammation and oxidative stress caused by AFB1 can also participate in the occurrence of cancer. Therefore, the main carcinogenic mechanism of AFB1 related ROS is summarized. This review also describes recent reports of AFB1 exposures in occupational settings. It is hoped that people will pay more attention to occupational health, in order to reduce the incidence of cancer caused by occupational exposure.

Tryptophan in poultry nutrition: Impacts and mechanisms of action

Many studies have shown that productivity, immune system, antioxidant status, and meat and egg quality can be optimized by dietary supplementation with amino acids that are not usually added to poultry diets. Understanding the effects of these amino acids may encourage feed manufacturers and poultry producers to include them as additives. One of these amino acids is tryptophan (Trp). The importance of Trp is directly related to its role in protein anabolism and indirectly related to its metabolites such as serotonin and melatonin. Thus, Trp could affect the secretion of hormones, development of immune organs, meat and egg production, and meat and egg quality in poultry raised under controlled or stressed conditions. Therefore, this review discusses the main roles of Trp in poultry production and its mode (s) of action in order to help poultry producers decide whether they need to add Trp to poultry diets. Further areas of research are also identified to address information gaps.

Effects of licorice extract, probiotic, toxin binder and poultry litter biochar on performance, immune function, blood indices and liver histopathology of broilers exposed to aflatoxin-B1

Probiotics, toxin binders, and plant extracts improve health and immunity of broiler chickens exposed to aflatoxin. The effects of licorice extract (LE), Protexin probiotic, toxin binder (Agrabound), and poultry litter biochar (PLB) in experimental aflatoxicosis were evaluated. In a completely randomized design, 504 broiler chickens were allotted to 7 treatments and 6 replicates with 12 broiler chickens in each. The experimental groups were as follows: T1) basal diet (B) without any feed additive or aflatoxin B₁ (AFB₁); T2) B + 0.5 mg AFB₁/kg; T3) T2 + 3 g LE/kg; T4) T2 + 6 g LE/kg; T5) T2 + 0.5 g Protexin/kg; T6) T2 + 1 g toxin binder/kg, and T7) T2 + 5 g/kg PLB. Broiler chickens fed AFB diet (T2) had lower body weight gain at the end of grower period and higher feed conversion ratio at the end of the finisher period, whereas inclusion of LE, probiotic, toxin binder, or PLB restores body weight of broiler chickens to that of the control group. Aflatoxicosis decreased total protein, TG, albumin, Ca, and P concentrations and greater uric acid concentration in broiler chickens as compared with the control group (P < 0.05). As compared with the T2 group, inclusion of 3 mg LE/kg increased serum total protein; inclusion of 3 mg LE/kg, probiotic, and toxin binder increased TG; inclusion of 3 and 6 mg LE/kg, probiotic, and PLB increased serum albumin; and the whole additive decreased serum uric acid of broiler chickens comparing with the control group. Lymphocyte percentage, avian influenza antibody titer, thymus relative weight, and immune response to phytohemagglutinin were decreased in the T2 group, whereas heterophil percentage and heterophil-to-lymphocyte ratio were increased (P < 0.05). Aflatoxicosis increased breast meat malondialdehyde concentration, liver enzymes activities, and number of fat vacuoles (P < 0.05). As compared with the T2 group, all of the additives lowered alkaline phosphatase, aspartate aminotransferase, and alanine transaminase activities, breast meat malondialdehyde concentration, and liver pathological damages (P < 0.05). It can be concluded that all of the additives are capable to decrease the negative impact of AFB₁ on broiler chickens' performance, blood indices, and immunity.

Fifty years of sheep red blood cells to monitor humoral immunity in poultry: a scientometric evaluation

Sheep red blood cells (SRBC) are commonly employed by scientists to address humoral immune responses in poultry. While SRBC are closely related to the study of humoral immunity in poultry, the initial purpose of much research did not focus on the mechanisms involved. Here, we provide a qualitative approach and utilize scientometric techniques, including trend analyses, scientific collaborations and mapping, and word co-occurrence evaluations, to summarize the role of SRBC in the poultry studies. First, a search strategy on Web of Science (WoS) was conducted to find publications that included SRBC in the poultry studies. Publications were partitioned into 4 categories: nutrition, genetics, microbiology, and physiology. For scientometric evaluation, scientific maps and networks were produced to clarify the occurrence of SRBC in the poultry studies. Data used included 702 publications over a period of 50 y (1968-2018) that were retrieved from the WoS database. About 95% of the publications were published in English language. Indigenous, experimental, and commercial chickens, quail, and medicinal plants field/topics were the main subjects of publications. In recent years, authors have used SRBC to study humoral immune response as a secondary aim of their research, especially when poultry production/performance was studied. This was especially the case in recent decades for studies in poultry nutrition. Analysis of keywords co-occurrence showed that the phrase SRBC mostly occurred with chickens, immune response, and especially with broilers. Moreover, the “medicinal plants” are becoming important especially for research on broilers and the reduced use of antibiotics in feed. Consequently, in addition to studying the medicinal plants, finding antibiotic replacements, and/or growth performance in the birds, humoral immunity is suggested to be investigated using SRBC. Moreover, interdisciplinary studies with the cooperation of scientists from agriculture, veterinary, immunology, biochemistry and molecular biology, and toxicology will develop in the future.