The Effects of Feeding Varying Concentrations of Vitamin a for One Year to Adult Dogs

136 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1999.Vitamin A is essential for many biological processes and has broad spectrum effects when homeostasis is altered. The purpose of these studies was to examine whether feeding varying concentrations of vitamin A to dogs would alter vitamin A homeostasis and if a biochemical indicator of status could be determined. Thirty-two random source dogs were assigned among four treatments in a randomized complete block design. The diets contained 15,000, 50,000, 116,000 or 225,000 IU vitamin A/1000 kcal dietary ME. Complete blood count, serum chemistry, prothrombin time, histological analysis of buccal mucosa, computed tomography of the tibia, and magnetic resonance imaging of the liver and tibia were performed. There were no effects of vitamin A on any parameters other than buccal mucosa (P ≥ .10). There were increases in stratum spinosum for female dogs regardless of diet at month 9(P ≤ .05); however, there were no effects in other strata (P ≥ .05). Retinyl ester concentration was monitored in serum and urine of the dogs. There were month x sex x diet interactions for serum retinyl linoleate and serum retinol (P ≤ .04) concentrations. The only effect for retinyl palmitate and retinyl stearate (P ≤ .02) was diet. Serum retinol was not different among diets or time periods (P ≥ .19). There was a month x sex x diet interaction for urinary retinol (P ≤ .0002). There were no effects for other urinary retinyl esters (P ≥ .41). In an additional study, dogs were fed either high or low vitamin A diets. Urine was collected and fractionated into four densities and analyzed for retinyl ester concentration. There were diet x fraction interactions for retinyl oleate, palmitate and stearate (P ≤ .001) in the 1.063 density flotate. When all fractions were combined, concentration of retinyl oleate in urine was higher in dogs fed the higher vitamin A diet than in dogs fed the lower vitamin A diet (P ≤ .043). However, there was no effect (P ≥ .091) of diet on urinary retinyl palmitate, stearate, linoleate or retinol between the two diets. In conclusion, dogs appear to have unique vitamin A metabolism, circulation and excretion.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD