Journal of Veterinary Diagnostic Investigation Vol. 18 Issue 5, 489-494
Copyright © 2006 by the American Association of Veterinary Laboratory Diagnosticians
Vitamin A deficiency in turkey poults
P.L. Cortes,
A.K. Tiwary,
B. Puschner,
R. M. Crespo1,
R.P. Chin,
M. Bland and
H.L. Shivaprasad
Correspondence: 1Corresponding Author: R.M Crespo, California Animal Health and Food Safety Laboratory System, Fresno Branch, University of California Davis, 2789 South Orange Avenue, Fresno, CA 93725
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Abstract
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Vitamin A deficiency was diagnosed in a commercial flock of 13,000 4–6-week-old turkey poults in the summer of 2004. The birds were initially submitted for examination because of a 3% increase in the reported daily mortality of the flock. Clinically, affected birds had stunted growth and ruffled feathers, showed signs of incoordination, and were depressed. At necropsy, pale white pseudomembranous to mucoid material was observed on the mucosal surface of the tongue, oral cavity, portions of the esophagus, and the crop of some birds. Histologically, there was squamous metaplasia of the mucosal epithelium of the oral mucosa, esophagus, sinuses, nasal glands, bronchi, proventriculus, and the bursa of Fabricius. Vitamin A was not detected in the feed sample at a detection limit of 0.5 mg/kg. Serum vitamin A concentrations in 7 birds were very low and ranged from 0.05 to 0.1 mg/L. Vitamin A concentrations in livers were extremely low (0.1 mg/kg wet weight, 1/7 poults) or undetectable (<0.1 mg/kg wet weight, 6/7 poults). A diagnosis of vitamin A deficiency was made based on gross and microscopic lesions and vitamin A concentrations in serum, liver, and feed. To the authors' knowledge, this is the first documented case of vitamin A deficiency in poults submitted from a commercial meat turkey producer comparatively depicting the gross and microscopic lesions with those found in other species of birds and mammals.
Key Words: Hyperkeratinization • hypovitaminosis A • squamous metaplasia • vitamin A deficiency
Vitamin A is an essential fat-soluble vitamin important for the maintenance and integrity of epithelial cells of the digestive, respiratory, urinary, and reproductive tracts.3,5,11 It is also involved in embryogenesis and growth, vision, immunity, and reproduction.3,11 Chickens and turkeys fed vitamin A–deficient diets may show clinical signs that include emaciation, stunted growth in young birds, a sharp drop in egg production in laying hens, decreased hatchability, listlessness and an unsteady gait, increased lacrimation, swelling of nictitating membrane, and nasal discharge.2,7 Gross lesions are initially confined to the mucous glands and ducts of the pharynx and esophagus and appear as white to yellowish caseous, coalescing nodules.11,18,19 Microscopically, squamous metaplasia is the hallmark of vitamin A deficiency (VAD), affecting the cuboidal and columnar epithelia of the mucosal glands of the digestive, respiratory, and urinary tracts and the eye.3,8,10,18,19 Natural and experimental VAD are well documented in chickens but a natural occurrence and histopathological description of this condition has not been reported in commercial turkeys. This report is an account of the gross and histopathological changes caused by VAD in commercial turkeys.
In August and September 2004, 4–6-week-old poults from 3 different houses in one commercial turkey ranch were submitted to the California Animal Health and Food Safety (CAHFS) laboratory, Fresno branch, because of increased mortality, depression, inappetence, unthriftiness, unsteady gait, and postural imbalance. A total of 37 birds from 3 poult houses (A, B, C) were submitted to the laboratory and examined on 3 different occasions in August and September 2004. The total number of poults placed at the start of production were 13,500, 15,000, and 13,000 from Houses A, B, and C, respectively. The birds had stunted growth and ruffled feathers, were dehydrated and depressed, and showed signs of incoordination. All birds examined had thickened oral and crop mucosa covered with white pseudomembranous necrotic patches, and 6 of 37 had pasty vents. The last group of birds submitted had closed eyelids, foamy to mucoid lacrimal discharge, nasal discharge, and caseous exudate lodged in the bursa of Fabricius and the medial canthus of the eyes (Fig. 1).
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Figure 1 a. Medial canthus of the eye with caseous exudate (arrow). b. The bursa of Fabricius with luminal caseous exudate (arrow).
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Tissues collected at necropsy for microscopic examination included the conjunctiva, oral mucosa, sinus, trachea, crop, esophagus, air sacs, lung, heart, liver, spleen, proventriculus, ventriculus, small and large intestines, kidney, bursa of Fabricius, and brain. Lesions consisted of varying degrees of hyperkeratinization and squamous metaplasia of the mucosal epithelial cells that were most severe in the oral cavity and esophagus (Fig. 2a), followed by the crop, conjunctiva, bursa of Fabricius (Fig. 2b), and less frequently, in the proventriculus (Fig. 2c), nasal gland (Fig. 2d), and lungs. Surprisingly, microscopic changes were not observed in the trachea and kidney. A fairly consistent lesion occurring among these birds was crop mycosis with spores and pseudomycelial elements characteristic of Candida sp. infiltrating the hyperkeratinized epithelial cells lining the crop and esophagus (37/37).
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Figure 2 Microscopic lesions of tissues from vitamin A–deficient poults. Squamous metaplasia with hyperkeratinization of glandular epithelium (mucus glands predominantly) (arrow) and the mucosal surfaces (arrow). a. Esophagus with hyperplastic, thickened mucosa and submucosal metaplastic mucus glands. Bar = 10 µ. b. Bursa of Fabricius with squamous metaplasia of the mucosa and follicles. Bar = 20 µ. c. Proventriculus with changes similar to that in the esophagus; hyperplastic, thickened mucosa with submucosal metaplastic mucus glands. Bar = 20 µ. d. Nasal gland with secretory glands exhibiting squamous metaplasia and distension by cellular debris. Bar = 10 µ.
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Samples from the oral cavity and the eyes were cultured aerobically on 3% sheep blood agar and McConkey agara and incubated at 37°C in 7.5% CO2 for 24–48 hours. Escherichia coli was the primary organism isolated from these tissues. Fungal cultures were not performed.
Feed and liver samples from poults in one of the bird houses were analyzed for concentrations of vitamin A, vitamin E, and minerals, whereas serum samples were analyzed for concentrations of vitamin A and E only (Table 1). Vitamin E and vitamin A concentrations in livers, sera, and feeds were determined by high-performance liquid chromatography using fluorescence detection.13,14,17 Briefly, feed and liver samples were hydrolyzed with potassium hydroxide before extraction. Vitamins A and E were extracted from serum and liver samples with petroleum ether after precipitation of proteins with ethanol. Feed samples were extracted with petroleum ether. Results were accepted if the peak area corresponding to the vitamin A or vitamin E concentration in the sample fell within the range of peak areas determined in the calibration curves, the reagent blank was free of interferences in the vitamin A and vitamin E elution regions and the spike recoveries were between 70% and 120%. Vitamin A and E concentrations were estimated on a wet weight basis. Vitamin A was not detected in the feed at a detection limit of 0.5 mg/kg. The recommended concentration of vitamin A is 5,000 IU/kg, which is approximately 1.5 mg/kg of vitamin A as all-trans retinol. The feed also contained a low level of vitamin E at 2.8 mg/kg. The recommended vitamin E concentration in feed is 12 IU/kg or approximately 12 mg/kg of vitamin E as dl-
-tocopheryl acetate. The feed contained the listed minerals (calcium, magnesium, phosphorus, potassium, sodium, and sulfur) in recommended concentrations for poultry diets. The concentrations of these minerals were within recommended ranges for turkey feed. The livers contained arsenic, cadmium, copper, iron, lead, manganese, mercury, and zinc in acceptable concentrations for poultry.16 The serum vitamin A concentrations in 7 birds submitted from House C (Table 1) ranged from 0.05 to 0.1 mg/L. Normal serum vitamin A concentrations in the serum of chicks have been reported to range from 0.44 to 0.64 mg/L.6 The corresponding liver vitamin A concentrations, less than or equal to 0.1 mg/kg, were also severely low when compared to reported references of 60–300 mg/kg.3,16 The serum vitamin E concentrations were within normal range between 1.1 and 2 mg/L.12 On the other hand, the liver vitamin E concentrations were low and ranged from 1.3 to 3.3 mg/kg wet weight (reported normal for 4–8-week-old chicks is 6.6–14.7 mg/kg).12
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Table 1 Comparison of vitamin A and E levels in the feed, serum, and liver before and after supplementation with a water soluble multi-vitamin supplement.
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After the last submitted case, the progress of poults was followed for 2 weeks after management changes were implemented, which included the immediate addition of a water-soluble vitamin pack supplementb at a rate of 113.4 g (one package) to 484.5 L of stock solution. Each 113.4 g package of the water-soluble vitamin supplement contained 3,750 IU of vitamin E and 3.62M IU of vitamin A Poults that are 5-weeks old drink approximately 180 ml of water per day. At this rate, each poult would have received 1.43 IU of vitamin E and 1,392 IU of vitamin A per day at the time of supplementation. Severely unthrifty birds were culled. Some birds recovered, but by market time, the flocks had already experienced total mortalities of 71% and 85% for House A and House C, respectively. Figure 3 shows the weekly mortality for poults from Houses A and C. Mortality data were not submitted from House B.
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Figure 3 Mortality pattern for birds in House A and C from placement to market. Shown is the approximate time when the water-soluble vitamin pack supplement was incorporated in the water.
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A diagnosis of VAD was made based on histopathological lesions and analysis of sera, liver samples, and the feed for vitamin A contents. The clinical signs and the gross and microscopic lesions provide evidence of the similarities of signs and lesions in humans and birds affected either experimentally or naturally with VAD.3,5,8,18,19 Experimental VAD in turkeys is characterized by squamous metaplasia in the esophagus, oropharynx, paraocular glands, sinuses, proventriculus, and bursa of Fabricius.3,7
The length of time that these poults received the vitamin A–deficient diet is unknown, but based on previous experimental studies,3,4,8 it might have been about 3 weeks before the onset of signs. Furthermore, histological lesions in the glands around the eyes are described to appear later in the disease process.4 The paraocular lesions observed in poults examined from the last case submission are consistent with these previous reports.
Nervous signs such as ataxia and incoordination have been reported in both vitamin A and E deficiencies. Lack of histopathological destruction of nerve cells in characteristic regions of the brain may be used to differentiate between vitamin A and E deficiencies.1 Listlessness and unsteady gait are often the first signs observed in VAD in both chickens and poults.7 Results of laboratory analyses demonstrated low concentrations of vitamin E in feed and liver, but serum concentrations were within normal limits and cerebellar lesions compatible with vitamin E deficiency were absent in the birds examined. In chickens and rats, plasma concentrations of vitamin A tend to be maintained until hepatic storage is exhausted because of the absence of the vitamin in the feed.3 It is not determined whether vitamin E concentrations follow similar patterns. Based on the absence of microscopic and gross lesions coupled with normal serum concentrations of vitamin E, the incoordination and imbalance seen in some of the affected poults was most likely caused mainly by a deficiency in vitamin A. In cases of multiple vitamin deficiency, it is possible that the concentrations of vitamin A in the liver and serum are depleted first before concentrations of vitamin E are diminished. It is also possible that levels of vitamin A were marginal since the first week of age, especially if the nutritional condition of the hen was poor or there were feed formulation errors that may have led to a poor-quality feed given to the poults.
It did not come as a surprise that 94% of the birds submitted had candidiasis since VAD fosters the growth of Candida in the digestive tract.20 Of the essential nutrients studied, vitamin A has a profound effect on the immune responses in man and laboratory animals.5 In chickens, adequate vitamin A in the diet was found to be important in maintaining the resistance of chickens against Candida albicans.9 VAD leads to abnormalities in keratinization as shown in human patients with mucocutaneous candidiasis.15 It was proposed that abnormal keratinization of superficial epithelial cells as a result of VAD leads to increased susceptibility to C. albicans invasion.15 It seems plausible that crop mycosis is a direct consequence of VAD, but clearly experimental studies using turkeys or chickens are needed to prove this.
As demonstrated in the cases discussed, VAD in poults follows a similar clinical presentation and shows similar gross and microscopic lesions as observed in other species of birds and mammals. Although squamous metaplasia in the kidney and trachea has been described, these changes were not observed. A diagnosis of VAD should lead a veterinarian to also test for other fat-soluble vitamin deficiencies such as vitamin E and D. The above cases showed that levels of vitamin E in the feed and liver were also depleted but it is suspected that vitamin A levels were depleted first. Although there was no formal investigation, further dialogue with the commercial producer suggests that the most likely cause of the vitamin deficiency in these poults was an error in feed formulation. The case presented is the first report of a vitamin A deficiency in commercial poults.
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Acknowledgments
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The authors thank Mohammad Rezvani, Randy Kokka, and Elena Alsing for their technical assistance and Dr Michael McFarland for reviewing the manuscript.
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Sources and manufacturers
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From the California Animal Health and Food Safety Laboratory System (CAHFS), University of California, Fresno Branch, 2789 South Orange Avenue, Fresno, CA 93725 (Cortes, Crespo, Chin, Shivaprasad), Davis Branch, PO Box 1770, Davis, CA 95617 (Tiwary, Puschner), and 3562 Jomar Drive, Napa, CA 94558 (Bland). 
a. Remel, Lenexa, KS.
b. Poult Pak, Alpharma, Fort Lee, NJ.
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References
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