Robert F. Wideman

Aflatoxicosis alters avian renal function, calcium, and vitamin d metabolism

Experiments were designed to determine the effects of aflatoxicosis on avian renal function, calcium (CA), inorganic phosphorous (Pi), and vitamin D metabolism, and to determine if the effects of aflatoxin are reversible upon discontinuation of toxin administration. Three-week-old male broiler chickens (n = 12 per treatment) received aflatoxin (AF; 2 mg/kg po) or an equal volume of corn oil, the AF carrier vehicle, for 10 consecutive days. After 10 d of treatment, half of the birds from each treatment group were anesthetized and prepared for renal function analysis, which included a 2-h phosphate loading period. Ten days after discontinuation of AF treatment, the remaining birds in each treatment group were anesthetized and prepared for renal function analysis. AF decreased plasma 25-hydroxy vitamin D [25(OH)D] and 1,25-dihydroxy vitamin D [1,25(OH)2D] levels after 5 d of treatment. After 10 d of treatment, urine flow rate (V), fractional sodium excretion (FENa), and fractional potassium excretion (FEK) were lower in AF-treated birds. In addition, total plasma Ca tended to be lower (p = .10) and fractional Ca excretion (FECa) tended to be higher (p = .10) in the AF-treated birds. Intravenous phosphate loading produced a sharp increase in urine hydrogen ion concentration ([H+]) in the AF-treated birds. Glomerular filtration rate (GFR) was reduced and plasma osmolality was increased in AF-treated birds 10 d after discontinuation of toxin administration. The results indicate that AF directly or indirectly affects Ca and Pi metabolism in avians. At the present time, the effects may be related to altered vitamin D and parathyroid hormone (PTH) metabolism. Aflatoxicosis may decrease endogenous PTH synthesis and the renal sensitivity to PTH. The AF-related increase in urine [H+] during phosphate loading is probably due to increased Na+/H+ counterport, suggesting that AF stimulates sodium reabsorption. Also, the decrease in GFR exhibited 10 d after toxin removal indicates that AF may cause prolonged alteration in renal function.

Excess sodium bicarbonate in the diet and its effect on leghorn chickens

1. A commercial 62-week-old layer flock experienced an acute drop in egg production and an increase in shell-less egg production within 2 days of consuming feed erroneously formulated to contain over 30 g/kg instead of 3 g/kg sodium bicarbonate (NaHCO3). Other symptoms included increased water consumption, diarrhoea and increased mortality associated with visceral gout. 2. An experiment was conducted to assess the responses of hens under controlled conditions. Twenty Dekalb XL Single Comb White Leghorn hens (50 weeks old) were placed in individual cages, having ad libitum access to water from trough waterers. Ten hens were fed the TEST (High NaHCO3) feed for one week (Test group), and ten hens remained on normal commercial layer ration (Control group). 3. Hens in the Test group had high water consumption and watery droppings, but egg production and mortality were not affected. Physiological evaluations indicated the Test feed caused metabolic alkalosis. Plasma sodium, urine pH and urinary sodium excretion were increased, and glomerular filtration rates were decreased in the Test group. 4. These physiological effects are consistent with known responses to excess sodium intake in domestic fowl. The reduced egg production and increased mortality caused by the Test feed under commercial conditions may be related to more severe dehydration experienced by hens in multi-bird cages supplied by cup-type watering systems.

Hypothyroidism and antibody production in immature male chickens.

This study was conducted to determine if hypothyroidism has an effect on humoral immunity in immature male chickens. Two week old Single Comb White Leghorn male chicks were used as experimental animals. Two experiments were conducted using different methods to induce hypothyroidism. In Experiment 1, birds were surgically thyroidectomized (Tx group) and in Experiment 2, hypothyroidism was induced by supplementing the feed throughout the experiment with 0.1% propylthiouracil (PTU group). Antibody production against sheep red blood cells (SRBC) (thymus-dependent antigen) and Brucella abortus (BA) (thymus-independent antigen) was tested at 4 weeks of age. Serum concentrations of T4 and T3 were measured in birds from each treatment group at 5 and 9 weeks of age. Body weights were recorded and birds were then autopsied and thyroid gland weights were measured. Hypothyroidism was successfully induced in both Tx and PTU birds, as reflected by significant reduction in body weights in both groups, enlargement of thyroid glands in PTU birds and absence of thyroid glands in Tx birds. Though T4 and T3 were reduced in sera of treated birds, considerable amounts of these hormones were detected. Hypothyroidism did not seem to have profound or consistent effects on antibody production against SRBC or BA. The possibility that thyroid hormones play a role in antibody production was not ruled out. However, it was suggested that within the physiological range of thyroid gland activity, thyroid hormones may not significantly regulate antibody production.

Kidney structure and responses of two commercial single comb white leghorn strains to saline in the drinking water

1. Growing pullets from two commercial strains were provided with saline (10 g sodium chloride) drinking water for three days to assess in vivo the urinary concentrating capacity of their kidneys. 2. Most of the pullets from strain A continued to gain body mass while drinking saline, indicating their kidneys conserved free water by forming a concentrated urine. Most pullets from strain B lost body mass while drinking saline, indicating their kidneys were unable to concentrate the urine sufficiently to obtain free water from the saline. 3. High proportions of large (0.23 to 0.42 mm circumference) glomeruli were found in the kidneys of pullets that gained body mass while drinking saline, whereas high proportions of small (0.07 to 0.18 mm circumference) glomeruli were found in the kidneys of pullets that lost body mass while drinking saline. 4. Glomerular sizes did not differ significantly when male birds of the two strains were compared. Urine from males of strain A had significantly (P less than 0.05) lower concentrations of hydrogen ions than urine from males of strain B, but no further differences were detected in comparisons of urine flow rates, glomerular filtration rates, renal plasma flow rates, urine osmolality, free water clearance, or sodium or potassium excretion rates.

Evaluation of commercial mammalian parathyroid hormone (PTH) radioimmunoassay systems for measuring avian PTH

Abstract 1. 1. Five commercial mammalian parathyroid hormone (PTH) radioimmunoassay (RIA) systems were evaluated for their capacity to detect avian PTH. 2. 2. Plasma samples were collected from normal White Leghorn cockerels ( Gallus domesticus ), parathyroidectomized (PTX) cockerels, and cockerels infused intravenously with a calcium chelating agent. 3. 3. None of the commercial PTH-RIA systems revealed significant differences among plasma samples from control, PTX or calcium-chelated cockerels. 4. 4. Some dose-response activity was detected with serial dilutions of chicken and turkey parathyroid gland extracts were tested with the commercial PTH-RIA systems. 5. 5. It is concluded that PTH levels in plasma are too low or avian PTH is too poorly recognized by the RIA antibodies for the commercial mammalian systems to be useful in measuring PTH in avian plasma.

Physiological evaluation of diuresis in commercial broiler breeders

A physiological investigation on an outbreak of diuresis syndrome in commercial broiler breeder hens was carried out. Daily water consumption increased 4-fold and daily manure wet weight increased two-fold in affected hens. 2. The syndrome did not have a genetic basis. It was associated with kidney dysfunction which, once acquired, was not alleviated by changing the diet, the drinking water, or the environment. Diuresis ceased when water intake was restricted and returned when water was again made freely available. 3. The syndrome was not caused by nephrogenic diabetes insipidus or diabetes mellitus. Key changes in kidney function associated with diuresis included: increased urine flow, decreased urine osmolality, reduced glomerular filtration rates, increased fraction of the glomerular filtration rate excreted as urine and decreased urinary hydrogen ion concentrations. 4. Preliminary histopathological findings and the physiological patterns of kidney dysfunction indicated that the diuresis syndrome was associated with permanent kidney damage, probably caused by the Arkansas strain of infectious bronchitis virus.

Susceptibility of two commercial single comb white leghorn strains to calcium‐induced urolithiasis: Efficacy of dietary supplementation with dl‐methionine and ammonium sulphate

1. Susceptibility to calcium-induced urolithiasis was assessed in pullets of two commercial SCWL strains (A and B) reared together from 5 to 18 weeks of age on diets containing 10 g/kg calcium (normal calcium: NC) or 35 g/kg calcium (high calcium: HC). 2. Kidney damage was not observed in pullets reared on NC diets. For pullets fed on HC diets, strain A developed significantly greater kidney asymmetry, a higher incidence of gross kidney damage and a higher incidence of uroliths than strain B. 3. Supplementing the HC diet with 6 g/kg DL-methionine significantly reduced the incidence of calcium-induced gross kidney damage and urolith formation in both strains. Ammonium sulphate (5.3 g/kg) was significantly more effective than DL-methionine in reducing calcium-induced kidney damage. 4. Neither DL-methionine nor ammonium sulphate caused a measurable metabolic acidosis. Neither supplement consistently affected water consumption or manure moisture.

Organic phosphate probes of the avian renal phosphate secretory mechanism

Parathyroid hormone (PTH) stimulates net renal inorganic phosphate (Pi) secretion in domestic fowl (Gallus domesticus). Recent evidence indicates that secreted Pi is derived from a highly sequestered, presumably organic, phosphate pool. A modified Sperber technique was used to survey the response of domestic fowl to unilateral renal portal infusions of organic phosphate compounds that had been implicated in previous studies of Pi secretion. None of the organic phosphate compounds produced a significant unilateral Pi secretory effect. It is concluded that these compounds neither directly stimulate Pi secretion in normal or parathyroidectomized birds, nor are they rate-limiting for the Pi secretory mechanism in birds infused with PTH.

A Potent Hypotensive Factor in Chicken Left Ventricle

Abstract Chicken artria and ventricles both have membrane-bound granules which resemble those containing atriopeptin.(ANP) in mammals. However, nothing is known about the contents of the avian granules. A previous study in chickens showed that although extracts of whole chicken heart or synthetic rat ANP both caused profound hypotension, ANP caused both natriuresis and diuresis, while chicken heart extract did not. The present study sought to locate the region(s) of chicken heart containing the hypotensive activity, and to observe the effect on sodium and water excretion and blood pressure in rats. Acid extracts of either atrium, either ventricle, ventricular septum, skeletal muscle, and liver were identically prepared from chickens and rats. Extracts were adjusted to the same protein concentration and injected (0.15 ml/kg) into anesthetized Single Comb White Leghorn roosters. Mean arterial pressure (MAP) and the time for recovery were measured. The most potent extract from chicken hearts was from the left ventricle (-38 ± 1 mm Hg, 149 ± 9 sec to recover). All other extracts (including right ventricle) produced only small (10-20 mm Hg), short-lived (20-30 sec) decreases in MAP. In contrast, only rat atrial extracts evoked long-lasting hypotension (>40 mm Hg, recovery time >200 sec). A 30-min infusion of the most potent chicken extract (left ventricle, CLV) into rats produced a small but significant natriuresis and diuresis compared to the vehicle time control (P < 0.05) and the hypotensive response to bolus injection was about one-third that seen in the chicken. The location of potent spasmolytic activity primarily in chicken left ventricle, the different avian renal responses to chicken heart extract and synthetic rat ANP (5), and the weak diuretic, natriuretic, and hypotensive effects of CLV extract in rats all suggest that the chicken heart substance may be different from mammalian ANP.