Dietary vitamin D toxicity in a household of pot-bellied pigs (Sus scrofa)

Interpretation of Serum Analytes for Nutritional Evaluation

Serum micronutrient analysis can provide insight into diet and clinical assessment, despite the complicated interplay between micronutrients and species idiosyncrasies. Approach serum nutrient analytes with skepticism, before jumping to alter diets or offering supplementation. Utilize across species but know that some exotics have exceptions to typical ranges, such as calcium in rabbits or iron in reptiles. Make sure you trust that referenced ranges reflect normal and healthy for that species. Micronutrients are integral to every bodily process, so measurement of serum analytes can tell a story that aids in the clinical picture, when one can recognize what stands out.

Improving vitamin D content in pork meat by UVB biofortification

Vitamin D deficiency is prevalent worldwide and identification of alternative food-based strategies are urgently warranted. In two studies, 12-week old crossbred pigs (Duroc x (Large White x Landrace)) were exposed daily to narrowband UVB radiation for ∼10 weeks or control (no UVB exposure) until slaughter. In Study 1 (n = 48), pigs were exposed to UVB for 2 min and in Study 2 (n = 20), this duration was tripled to 6 min. All pigs were fed the maximum permitted 2000 IU vitamin D₃/kg feed. Loin meat was cooked prior to vitamin D LC-MS/MS analysis. In Study 1, pork loin vitamin D₃ did not differ between groups. Study 2 provided longer UVB exposure time and resulted in significantly higher loin vitamin D₃ (11.97 vs. 6.03 μg/kg), 25(OH)D₃ (2.09 vs. 1.65 μg/kg) and total vitamin D activity (22.88 vs. 14.50 μg/kg) concentrations, compared to control (P < 0.05). Pigs remained healthy during both studies and developed no signs of erythema. Biofortification by UVB radiation provides an effective strategy to further safely increase the naturally occurring vitamin D content of pork loin, alongside feed supplementation.

Vitamin D Levels in Sows from Five Danish Outdoor Herds

Simple Summary

A cross-sectional study on vitamin D₃ status was conducted in five Danish outdoor sow herds throughout August 2020. The aim was to determine the vitamin D status of outdoor sows during the peak sunshine season. The average 25-hydroxyvitamin D₃ concentration in serum was 67 ± 16 ng 25(OH)D₃/mL in outdoor sows, which is considerably higher than levels found in sows housed indoors and fed a standard diet supplemented with vitamin D.

Abstract

Vitamin D is essential for sow health and productivity. Standard sow feed is therefore supplemented with vitamin D₃ or 25-hydroxyvitamin D₃ (25(OH)D₃). However, it is uncertain whether the levels achieved are adequate for optimal performance. Currently, information on serum levels of vitamin D in pigs reared under both indoor and outdoor conditions is lacking. In August 2020, we obtained blood samples from 97 organic newly weaned sows housed outdoors during pregnancy and farrowing and used these to test for vitamin D in serum. The average concentration was 67 ± 16 ng 25(OH)D₃/mL with a range of 32 to 134 ng 25(OH)D₃/mL. The vitamin D₃ content was 21 ± 7 ng/mL, ranging from 9 to 48 ng/mL. The average number of hours of sun from June to August was 7.0 ± 0.5 h/day. Parity, farm and body condition score did not significantly affect serum levels of 25(OH)D₃.

Modulation of Intestinal Phosphate Transport in Young Goats Fed a Low Phosphorus Diet

The intestinal absorption of phosphate (P_i) takes place transcellularly through the active NaPi-cotransporters type IIb (NaPiIIb) and III (PiT1 and PiT2) and paracellularly by diffusion through tight junction (TJ) proteins. The localisation along the intestines and the regulation of P_i absorption differ between species and are not fully understood. It is known that 1,25-dihydroxy-vitamin D₃ (1,25-(OH)₂D₃) and phosphorus (P) depletion modulate intestinal P_i absorption in vertebrates in different ways. In addition to the apical uptake into the enterocytes, there are uncertainties regarding the basolateral excretion of P_i. Functional ex vivo experiments in Ussing chambers and molecular studies of small intestinal epithelia were carried out on P-deficient goats in order to elucidate the transepithelial P_i route in the intestine as well as the underlying mechanisms of its regulation and the proteins, which may be involved. The dietary P reduction had no effect on the duodenal and ileal P_i transport rate in growing goats. The ileal PiT1 and PiT2 mRNA expressions increased significantly, while the ileal PiT1 protein expression, the mid jejunal claudin-2 mRNA expression and the serum 1,25-(OH)₂D₃ levels were significantly reduced. These results advance the state of knowledge concerning the complex mechanisms of the P_i homeostasis in vertebrates.

HYPERVITAMINOSIS D IN A GIANT ANTEATER (MYRMECOPHAGA TRIDACTYLA) AND A LARGE HAIRY ARMADILLO (CHAETOPHRACTUS VILLOSUS) RECEIVING A COMMERCIAL INSECTIVORE DIET

Hypervitaminosis D was diagnosed in a giant anteater (Myromecophaga tridactyla) and a large hairy armadillo (Chaetophractus villosus) being fed a commercial insectivore diet. Clinical findings included weight loss, reduced appetite, vomiting, and suspected abdominal discomfort. Hypercalcemia (3.68 and 2.04 mmol/L total and ionized calcium, respectively) was detected in the anteater, and plasma 25(OH)D levels were measured and found to be 808.7 and 379.4 nmol/L for the anteater and armadillo, respectively. Dietary change resulted in a reduction of 25(OH)D levels in both animals and resolution of hypercalcemia in the giant anteater. Dietary analysis of the commercial insectivore food revealed levels of vitamin D₃ higher than the data-sheet values. This case report demonstrates that hypervitaminosis D in Xenarthra can be associated with significant clinical signs.

Effect of UVB light on vitamin D status in piglets and sows

Piglets are born with very low levels of vitamin D. Feed is the only source of vitamin D for pigs kept indoors, and the levels in feed are restricted by European legislation. We aimed to study the effect of lamps releasing ultraviolet type B (UVB) light on the vitamin D status (serum 25-hydroxyvitamin D) in sows and piglets in a Danish indoor herd. A randomized trial with a parallel group design was initiated with two groups receiving a daily UVB-dose of maximum 0.7 standard erythema dose (SED) or 1 SED, in addition to a control group. The three groups included in the study consisted of 15 sows and their 195 offspring. Blood samples were taken from the piglets and sows on day 1, 12, and 24. Results showed no difference between the groups in serum levels of 25(OH)D₃ or vitamin D₃ on day 1, with the mean (±SD) for piglets being 0.96 ± 0.26 ng/mL and 0.06 ± 0.04 ng/mL, respectively. For sows, the values were 16 ± 3 ng/mL 25(OH)D₃ and 3 ± 0.8 ng/mL vitamin D₃ on day 1. A significant difference (p < 0.001) in serum 25(OH)D₃ between the groups receiving UVB light and the control group was observed on both day 12 and day 24. On day 24, the piglet control group had 5.5 ± 2 ng/mL 25(OH)D₃ and 0.4 ± 0.2 ng/mL vitamin D₃. For the UVB groups, the values were 21.6 ± 10. ng/mL 25(OH)D₃ and 8.3 ± 2.5 ng/mL vitamin D₃ for the 0.7 SED group and 19.5 ± 6.0 ng/mL 25(OH)D₃ and 7.6 ± 3.4 ng/mL vitamin D₃ for the 1 SED group. For the sows, the values were 25.6 ± 5.5 ng/mL 25(OH)D₃ and 6.6 ± 1.2 ng/mL vitamin D₃ for the control group, 66.7 ± 13.5 ng/mL 25(OH)D₃ and 21.3 ± 2.9 ng/mL vitamin D₃ for 0.7 SED group and 67 ± 15 ng/mL 25(OH)D₃ and 25 ± 5 ng/mL vitamin D₃ for the 1 SED. No significant difference was found between the two UVB groups for either piglets or sows. The use of lamps releasing UVB light is therefore suggested to be an efficient way to improve the vitamin D status of both sows and piglets.

Vitamin D metabolism in growing pigs: influence of UVB irradiation and dietary vitamin D supply on calcium homeostasis, its regulation and bone metabolism

The aim of this study was to prove whether pigs are able to synthesize vitamin D (vitD) in the skin and to investigate the influence of ultraviolet irradiation (UVB) on vitD status and calcium (Ca) homeostasis of growing pigs. Thirty-two 11-week-old pigs were kept without access to sunlight and divided into four groups receiving the following treatment in a 2 × 2 factorial design: (i) UVB irradiation or not and (ii) vitD in feed or not. Blood, urine and faeces were sampled every third week. In serum, vitD metabolites, Ca, phosphorus (P), magnesium (Mg) and bone markers were analysed. Digestibility of Ca, P and Mg as well as urinary excretion of these minerals was analysed. After 14 weeks, the animals were slaughtered, and samples of skin, intestines, kidneys and bones (metatarsus) were taken for further analyses: sterols of vitD synthesis in the skin, Ca flux rates in the intestines, expression of genes involved in Ca transport in the intestines and kidneys, bone mineral density (BMD) with the aid of peripheral quantitative computer tomography and bone mineral content by ashing the metatarsus. Irradiated animals showed higher levels of 7-dehydrocholesterol and tachysterol in the skin, higher levels of 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol in the serum and higher Ca net flux rates were determined in Ussing chambers. In contrast, the expression of genes involved in Ca transport in the intestines and kidneys was not altered. Similarly, the digestibility of Ca and P as well as the urinary excretion was not affected. With respect to the metatarsus, no differences in mineral contents and BMD were found between groups. At the end of the study, some subclinical signs of beginning vitD 'insufficiency' were observed in the group without access to vitD (represented by higher expression of 1α-hydroxylase in the kidney and increased parathyroid hormone in serum).

Chronic Vitamin D Intoxication in Captive Iberian Lynx (Lynx pardinus)

To document the biochemical and pathologic features of vitamin D intoxication in lynx and to characterize mineral metabolism in healthy lynx, blood samples were obtained from 40 captive lynx that had been receiving excessive (approximately 30 times the recommended dose) vitamin D3 in the diet, and from 29 healthy free ranging lynx. Tissue samples (kidney, stomach, lung, heart and aorta) were collected from 13 captive lynx that died as a result of renal disease and from 3 controls. Vitamin D intoxication resulted in renal failure in most lynx (n = 28), and widespread extraskeletal calcification was most severe in the kidneys and less prominent in cardiovascular tissues. Blood minerals and calciotropic hormones in healthy lynx were similar to values reported in domestic cats except for calcitriol which was higher in healthy lynx. Changes in mineral metabolism after vitamin D intoxication included hypercalcemia (12.0 ± 0.3 mg/dL), hyperphosphatemia (6.3 ± 0.4 mg/dL), increased plasma calcidiol (381.5 ± 28.2 ng/mL) and decreased plasma parathyroid hormone (1.2 ± 0.7 pg/mL). Hypercalcemia and, particularly, hyperphosphatemia were of lower magnitude that what has been previously reported in the course of vitamin D intoxication in other species. However, extraskeletal calcifications were severe. The data suggest that lynx are sensitive to excessive vitamin D and extreme care should be taken when supplementing this vitamin in captive lynx diets.

Hypercalcaemia in two dogs caused by excessive dietary supplementation of vitamin D

A three-year-old Border collie was presented with a two-week history of lethargy, stiff gait, polydipsia and polyuria. Biochemical analysis revealed hypercalcaemia. Serum concentrations of 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH]2D) were markedly elevated and parathyroid hormone was undetectable. Subsequent analysis of the dog's diet revealed that the food contained excessive amounts of vitamin D. The hypercalcaemia resolved following treatment with bisphosphonates and dietary change. Hypervitaminosis D was diagnosed in a second unrelated dog, which had been fed the same brand of dog food as case 1. The dog was also hypercalcaemic and had markedly elevated serum concentrations of 25(OH)D and 1,25(OH)2D. Hypervitaminosis D in dogs has been reported to occur secondarily to ingestion of either rodenticides containing cholecalciferol or antipsoriatic ointments that contain vitamin D analogues. Hypervitaminosis D has also been reported following the treatment of hypoparathyroidism. To the authors' knowledge, this is the first report of hypervitaminosis D in dogs following the accidental over supplementation of a commercial diet with vitamin D. While the benefits of adequate dietary vitamin D are well established in dogs, the potential deleterious effects of over supplementation of vitamin D should also be acknowledged.