| Thyroid hormone profile in dairy cattle acclimated to cold or hot environmental temperatures. | |
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MedLine Citation:
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PMID: 3644585 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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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. |
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Authors:
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C Aceves; C Romero; L Sahagun; C Valverde |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Acta endocrinologica Volume: 114 ISSN: 0001-5598 ISO Abbreviation: Acta Endocrinol. Publication Date: 1987 Feb |
Date Detail:
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Created Date: 1987-03-30 Completed Date: 1987-03-30 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0370312 Medline TA: Acta Endocrinol (Copenh) Country: DENMARK |
Other Details:
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Languages: eng Pagination: 201-7 Citation Subset: IM |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Acclimatization* Animals Cattle / metabolism* Cold Temperature Female Lactation Pregnancy Temperature Thyroid Hormones / metabolism* Thyroxine / blood Triiodothyronine / blood Triiodothyronine, Reverse / blood |
| Chemical | |
Reg. No./Substance:
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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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