The effect of L-T4 and TRH treatment on the T3 and T4blood serum concentrations, elements in plumage and excrements, and head epidermis height of the budgerigar (Melopsittacus undulatus)
2001
Golob, Z. (Golob d.o.o., Muta (Slovenia))
The main experiment included 64 six to eight-month-old budgerigars (Melopsittacus undulatus); 26 of them were treated, for 25 successive days, with high doses (1000 micro g kg*[-1)b.w.) of L-T4 (Vobenol; LEKLjubljana, Slovenia) and 38 were controls. After the 25th day, seven of the treated and twelve of the control animals then received TRH (VEB Berlin-Chemie, Germany) in a dose of 10 micro g kg*[-1)b.w., three times a week for ten successive weeks. The blood serum T3 and T4 values, as well as the head epidermis height were recorded during the period from September to December. The L-T4 treatment accelerated the elimination of feathers during moult (in September). The high T3 and T4 blood serum values in the animals treated with L-T4 decreased, when the treatment was completed, from October 5 to November 24, before returning to the levels of the untreated animals in December. The highest average epidermis height in the L-T4 treated animals was in October (8.69 +/- 0.41 micro m). It was almost level with the average value of the control animals in November. In the control animals the thyroid hormones in the serum had higher values twice, in September and December. The first increase was linked to the moult and the second one presumably to a drop in the room temperature to 13 degC. The head epidermis in the control animals was significantly higher during the moult (6.79 +/- 0.17 micro m) than in December (4.28 +/- 0.35 micro m). The TRH treatment activated the thyroid glands in the control animals, as well as in the animals with highly suppressed thyroid gland activity due to the L-T4 treatment. An additional 16 animals were included in the experiment; 8 of them were controls and the other 8 treated for 16 successive days with L-T4 500 micro g kg*[-1)b.w. This dose was efficient in the promotion of feather loss and was not toxic in comparison with the 1000 micro g kg*[-1)b.w. dose of L-T4.
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