Effects of dietary pyrrolizidine alkaloids on copper and vitamin A metabolism in the chicken and Japanese quail Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/bv73c3206

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  • Objectives of this study were to examine effects of dietary pyrrolizidine alkaloids (PA) on copper and vitamin A metabolism in the chicken which are very susceptible to the hepatoxic effects of PA and Japanese quail which are highly resistant to PA. Also, the possible interaction between copper and vitamin A in the two species and effect of PA on retention of previously stored vitamin A in the chicken were investigated. Three experiments were designed. Experiment 1 was to examine the effect of feeding the PA-containing plant tansy ragwort (TR)(Senecio jacobaea) on tissue levels of copper and vitamin A in the chicken. Experiment 2 was to investigate if dietary PA affected the retention of previously stored vitamin A in the chicken. Experiment 3 was to determine if hepatoxic effects of PA are necessary to influence copper and vitamin A metabolism in Japanese quail. In experiment 1, a 2x2x2 factorial design with dietary 0 and 5% TR, 0 and 250 ppm copper, and 0 and 25,000 IU/kg diet vitamin A was used. The results showed that body weight gain was reduced (P < 0.01) in birds fed TR. Both serum and liver copper concentrations were markedly increased (P <0.01) in the TR-fed group with 250 ppm copper supplement. Zinc concentrations in the serum and liver were significantly decreased (P <0.05) in the TR-fed groups compared to TR-free groups. Liver iron was increased (P <0.05) in the TR-fed birds. The serum vitamin A levels were significantly decreased (P < 0.01) in all TR-fed groups. The ranges of decrease were from 62 to 72 % in four TR -fed groups. The liver vitamin A concentrations were also significantly decreased (P <0.05) in TR-fed groups without vitamin A supplement. The effects of PA on liver and blood vitamin A concentration may reflect PA inhibition of synthesis of retinol-binding proteins, or impaired vitamin A absorption from reduced biliary excretion. There was no interaction between dietary copper and vitamin A levels and tissue concentrations of these nutrients. In experiment 2, a two period experiment was carried out. In the first period, two groups of chicks were fed a diet containing 25,000 IU vitamin A/kg diet for two weeks followed by a control or TR-containing diet for four weeks. Blood samples were taken at 4 day intervals for 24 days. It was found that by day 8, serum vitamin A levels were significantly depressed (P <0.05). After 24 days of PA exposure, serum vitamin A levels were reduced by 55 % and 8.5% in the TR-fed group and the control group, respectively. Liver concentration of vitamin A was increased (P < 0.05) at day 24 of TR feeding, while liver vitamin A concentration in birds fed the control diet was decreased by 13% over the same period. The results indicate that PA inhibit the mobilization of previously stored vitamin A from the liver, probably by inhibiting hepatic synthesis of retinol-binding proteins. Experiment 3 was a 2x2x2 factorial design with added 0 and 5% tansy ragwort, 0 and 250 ppm copper, and 0 and 25,000 IU/kg diet vitamin A. The results showed that consumption of TR did not affect the growth rate of Japanese quail. There were no significant differences in the serum copper concentrations among all treatment groups. Liver copper levels were decreased with TR feeding (P <0.05). The concentrations of zinc and iron in the serum and liver were normal in TR-fed groups compared to the controls. There was no significant effect (P >0.05) on the serum vitamin A concentration. The liver vitamin A concentrations were also not significantly different with the exception of the basal TR group. Copper supplementation of the diet increased serum vitamin A levels (P <0.05). The results suggest that hepatotoxicity is necessary to induce the changes in tissue levels of copper and vitamin A seen in PA-susceptible species.
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