Basal Levels and GnRH-induced Responses of Peripheral Testosterone and Estrogen in Holstein Bulls with Poor Semen Quality

Abstract

Abstract. The present study investigated the basal levels and GnRH-induced responses of peripheral testosterone and estrogen in Holstein bulls with poor semen quality. On the basis of semen parameters, bulls (n=5) having poor semen quality were selected as experimental bulls, and good semen quality bulls (n=4) were used as control bulls. Both groups were treated intramuscularly once with GnRH (250 μg of fertirelin acetate). Blood samples were collected at -1 day (d),-30 min and 0 h (treatment) followed by every 30 min for 5 h and 1, 3 and 5 d post-GnRH treatment (PGT), and LH, testosterone and estradiol-17β (E2) concentrations were measured. The pretreatment concentrations were used as basal levels. The percentage increments based on the 0-h levels were calculated per bull for each sampling time until 5 h PGT, and differences were compared between the experimental and control groups. The PGT concentrations of testosterone and basal and PGT concentrations of E2 were significantly lower in the experimental group. The testosterone increment in the experimental group was delayed and significantly lower from 1 to 5 h PGT than those in the control group. It can be suggested that bulls with poor semen quality have delayed and lower GnRH-induced testosterone response and may also have lower estrogen levels. Key words: Bull, Estrogen, GnRH-induced response, Poor semen quality, Testosterone (J. Reprod. Dev. 57: [373][374][375][376][377][378] 2011) ull fertility is very important because one bull may serve around twenty females under natural service conditions or hundreds of thousands under an artificial insemination program. Some bulls produce less or substandard quality spermatozoa, which results in a smaller number of inseminates and may also impair fertility postinsemination or postservice. The testes of such bulls are primarily characterized by mixed atrophied lesions, with abundant Sertoli cell-only tubules, in which the reversion of Sertoli cell maturity is possible [1]. However, it is difficult to understand their testicular physiology precisely and determine their future utilization.Different types of spermatogenic arrests leading to impaired fertility and their relationships with gonadotropic and gonadal steroid hormones have been described in men [2-4], rats [5] and bulls [6,7]. Although moderately predictable for the absolute fertility level, semen quality parameters of motility, sperm number and sperm morphology are valuable in identifying bulls of very low fertility [8]. The peripheral level of gonadotropins and testicular steroids may not be related to the testicular pathology in bulls, which points towards other abnormalities, including impaired gonadal responses to those hormones or secretion of intratesticular factors [7]. Some early studies have shown that the pituitary and testicular response with exogenous GnRH has no relation with semen production [9], sperm parameters [10] and libido [11] of bulls, while one study considered the testosterone response to GnRH to be a more reliable predictor of bull...

Luteinizing hormone, testosterone and total estrogens response to exogenous GnRH in crossbred bulls with differing semen quality

“…Each bull, irrespective of their semen quality, showed different levels, pattern of LH release and time taken to attain peak values, which was in accordance with a similar study carried out on HF bulls (Devkota et al, 2011).…”

“…By contrast, Post et al (1987b) and Devkota et al (2011) observed a positive relationship between the fertility or semen parameters and the hormonal response to GnRH. Therefore, the present study was designed with the objective of investigating whether a difference existed in gonadal and pituitary hormonal response to exogenous GnRH challenge in crossbred bulls with differing semen quality.…”

“…Devkota et al (2011) treated the Holstein Friesian (HF) bulls with 250 µg of GnRH (fertirelin acetate). However, Chenault et al (1990) observed that buserelin was approximately 10 to 20 times more potent than fertirelin acetate in the bovine for both LH and follicle stimulating hormone (FSH) release.…”

Gestational form of Selenium in Free-Choice Mineral Mixes Affects Transcriptome Profiles of the Neonatal Calf Testis, Including those of Steroidogenic and Spermatogenic Pathways

“…Importantly, although steroid production by the testis is basal at birth, serum concentrations of estradiol in the bull calf begin to increase soon thereafter, and serum concentrations of testosterone increase from around 10 weeks of age [41,42]. In the mature bull, GnRHinduced increases in circulating testosterone and both basal and GnRH-induced increases in circulating estradiol are reported to be lower in bulls with poor semen quality [43].…”

Age-related changes in testicular parameters and their relationship to thyroid hormones and testosterone in male Murrah buffaloes

“…Bull fertility is an important aspect because one bull may serve around 20 females under natural conditions or hundreds of thousands under an artificial insemination program (Devkota et al, 2011). Reliable fertility information can be obtained on several bulls by using them to impregnate a large number of cows or by evaluating their semen quality.…”