Age-Related Changes in the Serum Levels of Inhibin, FSH, LH and Testosterone in Holstein Bulls.

Abstract

Abstract.It has been well demonstrated that the quantity and quality of the semen obtained from bulls improve with age. To understand the relationship between the semen characteristics and hormonal conditions in Holstein bulls, age-related changes in serum levels of inhibin, FSH, LH and testosterone were investigated. One hundred three Holstein bulls were divided into 11 age-groups as 2.5 (n=10), 6.5 (n=10), 12 (n=12), 24 (n=9), 36 (n=10), 48 (n=12), 60 (n=13), 72 (n=8), 84 (n=5), 96 (n=8) and 108 (n=6) months old. Serum levels of inhibin, FSH, LH and testosterone were measured by specific radioimmunoassays. Serum levels of inhibin were highest in bull calves before 12 months of age, and significantly decreased at 12 months old and remained low thereafter. In contrast to inhibin, serum levels of gonadotropins and testosterone were low in young bulls, and then increased with age. In summary, the concentrations of inhibin, gonadotropins and testosterone in serum changed with age in Holstein bulls. Key words: Bulls, Gonadotropins, Inhibin, Testosterone.(J. Reprod. Dev. 46: [245][246][247][248] 2000) environment, management practices, physiological status and genetics. In general, semen from Holstein bulls for use in AI is collected from bulls that are 1 to 7 years old. The age of the bulls at the time of semen collection affects the volume of the ejaculate, the concentration of sperm and sperm motility. It has been well shown that all of these ejaculate characteristics increase as bulls age [1]. Spermatogenesis is regulated by several hormones of the hypothalamus-hypophyseal-gonadal axis. The hormones that are required to support spermatogenesis are FSH and testosterone [2]. Inhibin and LH are indirectly involved in -Originalrtificial insemination (AI) is the main tool used for genetic improvement of dairy cattle. The conception rate with AI depends on the characteristics of the semen that are cryopreserved in straws. To make a large number of straws, AI organizations try to collect the maximum amount of spermatozoa of the highest possible quality. The quantity and quality of semen (i.e. volume of ejaculate, concentration of spermatozoa in the ejaculate, and percentage of spermatozoa that are motile) produced by bulls are affected by the

Changes in Circulating and Testicular Levels of Inhibin A and B During Postnatal Development in Bulls

“…This is probably the cause of the decrease in circulating inhibin levels in bulls after 20 weeks of age, in spite of the increase in the testicular contents of inhibin. We found no correlation between the FSH profile and the inhibin A or total inhibin profile; this finding is not consistent with previous reports of a negative [8,9] or positive correlation [10]. The discrepancy between these previous studies and ours is not readily explained, but our determination of the inhibin and FSH profiles was more precise because we used more frequent blood sampling (1-week intervals) than was used in these other studies (2-to 12-week intervals).…”

“…The circulating levels of total inhibin and inhibin A reached a plateau by 14 weeks of age and then decreased as the bulls aged, and the changes in total inhibin were similar to previous findings [9,10]. We can expect that a combination of testicular inhibin content and the testis weight to body weight ratio contributes to changes in the circulating concentrations of inhibin.…”

“…Previous studies that examined the relationship between circulating FSH and inhibin in developing bulls reached contradictory conclusions; two studies found a negative correlation between the plasma levels of inhibin and FSH from 10 to 36 weeks of age [8] or from 2.5 to 108 months [9], whereas Miyamoto et al [10] found a positive correlation between 1 and 8 months. However, the radioimmunoassays (RIAs) used in the above studies were based on antisera directed against the α subunits of inhibin.…”

Circulating Testosterone and Inhibin Levels at Different Ages in the Male Beluga (<i>Delphinapterus leucas</i>)

“…This type of relationship between inhibin and testosterone is also seen in land mammals and it has been reported that the circulating inhibin levels in male cattle were high prior to sexual maturity compared with levels after sexual maturity [8,13]. Although the exact mechanism of inhibin decrease and testosterone increase after sexual maturity is not known, it could be due to suppression of gonadotropin-releasing hormone secretion in the hypothalamus by the high testosterone concentration.…”

Peri-conception and first trimester diet modifies reproductive development in bulls

“…A suite of molecular pathways is regulated by an interdependent complement of hormones including testosterone, FSH, inhibin and activin, which rise and fall in a specified sequence during prepuberty and peri-puberty to result in functional spermatozoa in the adult bull (Evans et al 1996;Matsuzaki et al 2000;Kaneko et al 2001). This sequence is known to be disrupted by nutritional intervention during the preweaning period (Brito et al 2007b(Brito et al , 2007c possibly mediated by metabolic hormones (i.e.…”