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. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37970 |
| Date | 28 March 1991 |
| Creators | Huan, Jianya |
| Contributors | Cheeke, Peter R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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