Document Detail


Thyroid hormone profile in dairy cattle acclimated to cold or hot environmental temperatures.
MedLine Citation:
PMID:  3644585     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Milk yields and the circulating profile of T4, T3 and rT3 were assessed during three different seasons of the year, in first trimester lactating (L) and in dry (D) multiparous holstein cows acclimated to distinct weather conditions. Within the thermoneutral zone (18-28 degrees C; 40-60% RH) and regardless of their geographical location, the thyroid hormone profile in all L-cows (n = 50) resembled the so-called euthyroid sick syndrome (T4, 43.7 +/- 7.7 nmol/l; T3, 1.31 +/- 0.10 nmol/l and rT3, 0.52 +/- 0.08 nmol/l). In both groups of animals the T3/T4 molar ratio was similar within the entire range of climates encompassed in the study. However, both groups exhibited a significant shift in the T3/rT3 molar ratio during cold (10 degrees C; 50%) or hot-dry (34 degrees C; 40%) weather conditions. This shift reaches maximum values (L, 6.5 +/- 1.2; D, 7.9 +/- 1.0 nmoles/l) under hot-humid conditions (28-42 degrees C; 60-90%). The relative increase of T3 levels from comfortable to cold or hot environmental temperatures, was significantly higher in L and D animals (30 vs 12%, respectively). Furthermore, only L-cows exhibited a significant decrease in the rT3/T4 molar ratio during either type of thermoregulatory demands, as well as a significant increase of T4 values under heat-acclimation. These results suggest that heat-acclimation in dairy cattle does not depress thyroid gland activity, and lend further support to the notion that adaptive thermoregulatory mechanisms in homeothermic vertebrates, involve adjustments in the peripheral monodeiodinative pathways of thyroid hormones.
Authors:
C Aceves; C Romero; L Sahagun; C Valverde
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Acta endocrinologica     Volume:  114     ISSN:  0001-5598     ISO Abbreviation:  Acta Endocrinol.     Publication Date:  1987 Feb 
Date Detail:
Created Date:  1987-03-30     Completed Date:  1987-03-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370312     Medline TA:  Acta Endocrinol (Copenh)     Country:  DENMARK    
Other Details:
Languages:  eng     Pagination:  201-7     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Acclimatization*
Animals
Cattle / metabolism*
Cold Temperature
Female
Lactation
Pregnancy
Temperature
Thyroid Hormones / metabolism*
Thyroxine / blood
Triiodothyronine / blood
Triiodothyronine, Reverse / blood
Chemical
Reg. No./Substance:
0/Thyroid Hormones; 5817-39-0/Triiodothyronine, Reverse; 6893-02-3/Triiodothyronine; 7488-70-2/Thyroxine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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