[Seasonal evolution of blood levels of thyroxine and triiodothyronine in the post-pubertal bull in France and Iraq. Concomitant variations of LH and testosterone].
An inquiry was conducted in 2 performance testing stations, A and B located in France and Iraq, respectively. In both stations, at solstice and equinox, thirty 15 month-old Holstein bulls were blood sampled for plasma LH, testosterone, thyroxine and triiodothyronine determination. For LH, no coherent seasonal effect was found. As regards testosterone, maximal mean values were obtained in December in both stations (3.4 ng/ml). In A as well as in B, thyroxine peaked in December reaching 64.6 ng/ml and 77.8 ng/ml, respectively, and falling down to 49.4 ng/ml and 65.6 ng/ml, respectively in June. The difference was significant for A (P less than 0.001). For T3, the fall from December (1.42 ng/ml in A and 1.68 ng/ml in B) to June (1.09 ng/ml in A and 1.26 ng/ml in B) resulted in about the same relative value and was significant (P less than 0.005) in both stations. The detrimental effect of high temperatures on semen quality does not seem to be mediated by an alternation of thyroid function.
Shubbur
A
A
Laboratoire pour le contrôle des reproducteurs-UNCEIA, Maisons-Alfort, France.
Goffaux
M
M
Thibier
M
M
D000367:Age Factors; D000818:Animals; D002417:Cattle; D005602:France; D007493:Iraq; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D012621:Seasons; D013739:Testosterone / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
D014284:Triiodothyronine; D013739:Testosterone; D007986:Luteinizing Hormone; D013974:Thyroxine
Evolution saisonnière des niveaux plasmatiques de thyroxine et de triiodothyronine chez le taureau post-pubère en France et en Irak. Variations concomitantes des taux de LH et de testostérone.