Temporary modulation of responses to common vaccines and serum cation status in broilers during exposure to low doses of aflatoxin B1.

The purpose of this study was to observe the effects of low doses of aflatoxin B1 (AFB1) on responses to common vaccines and levels of serum cations in broilers. Male broilers at 7 d of age were fed control (no AFB1), a 75 µg of AFB1/kg (75 ppb of AFB1) diet, or a 750 µg of AFB1/kg (750 ppb of AFB1) diet. The 750 ppb of AFB1 diet resulted in a temporary increase in ELISA titers against Newcastle disease virus (P = 0.014) and infectious bursal disease virus (P = 0.005) during wk 2 and 4 of exposure, respectively, compared with the control diet. Conversely, lower (P ≤ 0.01) serum protein concentrations were found in broilers under the 750 ppb AFB1 diet during wk 2 and 4. During wk 2 of exposure, lower serum levels of potassium were noted in birds under both the 75 (P = 0.037) and 750 ppb (P = 0.000) AFB1 diets compared with those under the control diet. During wk 5, higher serum magnesium (P = 0.004), and sodium (P = 0.000) under the 750 ppb AFB1 diet were found compared with the control diet. These data indicate that low dietary levels of AFB1 can temporarily increase or decrease the studied serological variables in broilers depending upon the stage of exposure.

Deoxynivalenol as a contaminant of broiler feed: effects on bird performance and response to common vaccines.

Recent data suggest that Fusarium trichothecenes may reduce broiler performance at levels previously thought not to affect this variable in chickens. In the present study, we investigated the effects of deoxynivalenol (DON), a type-B trichothecene, on broilers. Male broilers at 7 d of age were fed either a basal diet (0.265 ± 0.048 mg of DON; 0.013 ± 0.001 mg of zearalenone/kg), a low DON diet (1.68 mg of DON/kg; 0.145 ± 0.007 mg of zearalenone/kg), or a high DON diet (12.209 ± 1.149 mg of DON/kg; 1.094 ± 0.244 mg of zearalenone/kg). Increasing levels of DON decreased the weekly weight gain linearly (P ≤ 0.041) during the first 3 wk of exposure; there were no significant differences in the weight gain of the birds after wk 3. With increasing levels of DON, the titers against Newcastle disease virus increased linearly during wk 2 (P = 0.022) and wk 4 (P = 0.033) of exposure, whereas the titers against infectious bronchitis virus decreased linearly (P = 0.006) during wk 5 of exposure. The serum protein concentration increased linearly (P = 0.017) during wk 2 and quadratically (P = 0.002) during wk 4 of exposure. Under these experimental conditions, the performance and vaccine response of the broilers were modulated to varying degrees at concentrations of DON that are currently permitted (up to 5 mg/kg of diet) in many countries. Further studies are therefore required to clarify the implications of these results on the welfare of chickens.

Deoxynivalenol as a contaminant of broiler feed: intestinal development, absorptive functionality, and metabolism of the mycotoxin.

Deoxynivalenol (DON) has been recently documented to deteriorate intestinal morphology in chickens at dietary doses that are regarded as safe for this species. The present trial was conducted to explore the significance of these morphological changes in relation to intestinal absorptive functionality and DON metabolism. Ross broilers at 7 d of age were fed either a basal diet (0.265 ± 0.048 mg of DON/kg; 0.013 ± 0.001 mg of zearalenone/kg), a low DON diet (1.68 mg of DON/kg; 0.145 ± 0.007 mg of zearalenone/kg), or a high DON diet (12.209 ± 1.149 mg of DON/kg; 1.094 ± 0.244 mg of zearalenone/kg). The DON diets (to variable degrees) progressively decreased the relative density (weight:length) of the small intestine with increasing exposure length, which could be correlated with a decrease in villus height in the small intestine. Short circuit current of the jejunal epithelium, reflecting transport function of the epithelium per unit area, was reduced (P = 0.001) in the birds fed the high DON diet. The increasing dietary level of DON linearly (P = 0.035) increased the length of the jejunum in wk 4 of exposure, resulting in conservation of macronutrient retention. Upon challenging the birds with a fixed amount of DON after wk 5 of exposure, higher (P ≤ 0.033) amounts of DON and the detoxification metabolite (de-epoxy-DON) were found at 5 h postchallenge in the guts of birds raised on the DON diets. The increasing level of previous exposure to DON linearly (P = 0.040) decreased the plasma level of DON in the birds at 1 h postchallenge. The amounts of zearalenone and its analogs in the gut and plasma also followed a trend similar to that for DON. These data suggest that intestines in chickens may adapt to a chronic DON challenge by morphological and functional modifications. The birds having previous exposure to Fusarium mycotoxins showed moderate detoxification coupled with reduced transfer of the mycotoxins to systemic circulation. Some metabolites of zearalenone found in this study were previously unknown for chickens.

Gross intestinal adaptations in relation to broiler performance during chronic aflatoxin exposure.

The present trial was conducted to study some morphological, digestive, and electrophysiological variables of the small intestine during chronic exposure of broilers to aflatoxin B(1) (AFB(1)). Ross 308 male chicks (7 d old) were randomly allotted to control (no AFB(1)), low AFB(1) (0.07 mg of AFB(1)/kg), or high AFB(1) (0.75 mg of AFB(1)/kg) diet. The high AFB(1) diet resulted in reduced (P ≤ 0.002) bird performance during the first 4 wk of exposure, whereas the low AFB(1) diet temporarily reduced (P = 0.034) the bird performance during wk 3 of exposure. During wk 4 of exposure, a linear (P ≤ 0.013) decrease in the unit weight of both the duodenum and jejunum was observed with increasing levels of AFB(1). This reduction in unit weight appeared to progress from the proximal (duodenum) to the distal (jejunum) small intestine with increase in the length of exposure and was not accompanied by modulation of electrophysiological variables in jejunal epithelium. Response from amiloride, a specific blocker of epithelial sodium channel, was also similar among jejunal epithelia of birds under different treatments. Interestingly, a compensatory linear (P ≤ 0.002) increase in the length of the duodenum and jejunum under high AFB(1) diets was noted to occur during wk 4 of exposure. Thus, retention of DM and nitrogen was not negatively affected by the AFB(1) diets. These data indicate that the intestine in broilers may adapt to an ongoing dietary challenge to AFB(1).

In vitro aflatoxin B(1) exposure decreases response to carbamylcholine in the jejunal epithelium of broilers.

The study was conducted to evaluate if aflatoxin B(1) (AFB(1)) has the capacity to affect the electrophysiological variables and active glucose uptake in jejunal epithelium of chicken. For this purpose, intestinal segments from the middle jejunum of broilers (35 to 39 d old) were incubated in Ussing chambers in the presence of 0 (vehicle control), 1.25, 2.50, and 3.75 microg of AFB(1)/mL of buffer. After 40 and 60 min of incubation with AFB(1), d-glucose (20 mmol/L) and carbamylcholine (200 micromol/L; an analog of acetylcholine and inducer of apical Cl(-) secretion) were respectively added to the incubation medium. Addition of 3.75 microg of AFB(1) caused an increase (P < 0.04) in short-circuit current (I(sc)) and transmural potential difference (V(t)) between 12 to 27 min postexposure as compared with the control. Glucose-induced DeltaI(sc) and percentage of DeltaV(t) were reduced (P < 0.04) at 2.5 and 3.75 microg of AFB(1)/mL, respectively, as compared with the control. The carbamylcholine-induced DeltaI(sc) and DeltaV(t) were both lower (P < 0.05) at 3.75 microg of AFB(1)/mL as compared with the control (-0.05 microA/cm(2), 0.1 mV vs. 1.1 microA/cm(2), and 0.6 mV, respectively). These observations indicate that acute exposure to AFB(1) may increase apical anion secretion in the jejunal epithelium of chicken. The negative effect of this increased anion secretion on active glucose uptake was, however, not prominent and may be considered as moderate or progressive in nature.