| Popis: |
One of the underresearched scientific issues is endocrine regulation in bulls of high genetic merit and methods of increasing sexual potency, providing long-termuse of stud bulls of high genetic potential. The present study investigated the endocrine profile of Holstein bulls depending on their age. The objects of the study were 36 Holstein stud bulls with an average weight of 970 kg. The animals were divided into two age groups. The first group included young bulls aged 17.6 ± 0.6 m and the second group consisted of animals aged 30.5 ± 1.8 m. The testosterone level in bulls’ blood fluctuated from 7.03 to 17.56 nM. Average hormone content was 11.05 nM. Such hormonal profiles indicate high potency of bulls. Concentration of triiodothyronine was 5.79 ± 0.54 pM, of free thyroxine -22.29 ± 3.78 pM, and total value of thyroid hormones –29.52 ± 2.97 pM. Free triiodothyronine in bulls’ blood serum is 3.8 times less than free thyroxine. However, the level of free fraction of thyroxin and the total amount of hormones is high enough to confirmNan intensive metabolism in the animals’ body. Differences were observed in the proportion of thyroid hormones (CT3/CT4) and the level of testosterone. Importantly, the level of free triiodothyronine among all stud bulls was low (5.02–6.12 pM) and did not surpass the content of free thyroxine. Positive correlation between the free thyroxine content and total value of free fractions of thyroid hormones (k = 0.99), negative correlation between CT3/CT4 and free thyroxine (k = −0.64), between CT3/CT4 and total CT3+ CT4 (k = −0.58), CT3 and the age of stud bulls (k = −0.51) were observed. Thus, our research illuminated aspects of endocrine profiles of highly valued stud bulls and found differences depending on their age. |
