Studies on the Relationship between Thyroid Function, Cold Acclimation and Retention Time of Digesta in Sheep

Publisher Website
Google Scholar
Abstract
The effects of ambient temperature (22 to 55 C vs 2 to 5 C) and injection of triiodothyronine (T3; 0, .125 or .25 mg T3/day) on apparent digestibility, oxygen consumption, concentration of thyroid hormones in plasma, and mean retention times of digesta in the reticulo-rumen, hind gut and total tract of sheep given brome grass (Bromus inermis) pellets were studied in two experiments in order to determine whether T3 was a mediator causing the decreased retention time observed in cold-exposed sheep. In thyroid-intact sheep, both exposure to cold and injection of T3 resulted in decreased (P<.05) apparent dry matter digestibility, and increased (P<.05) plasma T3 concentration. Mean retention time in the rumen and in the whole tract, measured by reference to the fecal excretion of a dose of 103Ru-phenanthroline administered into the rumen and/or abomasum, was significantly reduced (P<.05) by exposure of sheep to 2 to 5 C and by injection of .25 mg T3/day. In thyroidectomized sheep maintained at 22 to 25 C, apparent dry matter digestibility and mean retention time in the whole tract were decreased (P<.05), and oxygen consumption and T3 plasma concentration were increased (P<.05) by injection of T3. When thyroidectomized sheep receiving T3 were also exposed to 2 to 5 C, there was a tendency for an additional reduction in the mean retention time of digesta in the rediculo-rumen. The data indicate that T3 is involved in the mechanism for control of retention time of digesta but is not the only mediator influencing the reduction in mean retention time and apparent digestibility in the whole tract of cold-exposed sheep. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.

This publication has 4 references indexed in Scilit: