Seasonal variation in the reproductive hormones of male goats.
The aim of this work was to study the circannual plasma profiles of LH, PRL, testosterone (T) and estrone sulfate (E1S) in different periods of the year and to characterize the possible variations in LH and PRL release patterns. We also tried to verify a possible relationship between plasma PRL fluctuations and ambient temperature, as well as the influence of an acute stress condition on levels of plasma PRL. Six adult male goats of the Ionica and Alpine breed reared in Southern Italy (40 degrees N lat.) were subjected to frequent samplings (every 15 min for 6 h) once a month for a whole year. The blood samples were assayed for plasma concentrations of E1S, LH and PRL by radioimmunoassay, and for T by enzymeimmunoassay. The ambient temperature was recorded on each day of bleeding. Sex steroids and PRL showed marked circannual variations, with the highest levels during the summer (July) and the lowest during the winter-early spring (March). The concentrations of plasma LH did not indicate significant seasonal variations. A positive relationship was observed between plasma levels of PRL and E1S and ambient temperature. The patterns of LH release seemed to change depending on season, but this was not an obvious and common feature in all bucks. The hormone concentrations for plasma PRL profiles seemed to be influenced by an acute stress condition (associated with cannula insertion and handling procedures), with the variations more marked when the plasma levels of PRL were low.
Grasselli
F
F
Instituto di Fisiologia Veterinaria, Università di Parma, Italy.
Gaiani
R
R
Tamanini
C
C
D000818:Animals; D006041:Goats / Q000097:blood*; D006728:Hormones / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D011388:Prolactin / Q000097:blood; D012098:Reproduction / Q000502:physiology*; D012621:Seasons
D006728:Hormones; D011388:Prolactin; D007986:Luteinizing Hormone