Early prepubertal testis criteria, seminiferous epithelium and hormone concentrations as related to testicular development in beef bulls (original) (raw)
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Testicular development in Brahman bulls
Theriogenology, 2005
Brahman breed bulls (Bos indicus) are widely used to introduce environmental resistance traits into meat-producing herds. However, their reproductive development is slower than European breeds (Bos taurus). The objective of this study was to assess the development of the seminiferous epithelium in Brahman bulls. Twenty-three prepubertal bulls were castrated and testicular samples taken for histological processing. Light microscopic images were digitized and cells of the seminiferous epithelium were assessed. Immature Sertoli cells gradually decreased in numbers and were no longer detected after approximately 14 months of age; concurrently, the numbers of mature Sertoli cells increased from 10 to 14 months. Spermatogenesis started during the ninth month; prior to that, only gonocytes and immature Sertoli cells were observed. Type A spermatogonia, spermatocytes, round spermatids, elongated spermatids and spermatozoa were first detected at 9.5, 11, 11, 13 and 16 months of age, respectively. The delay in the onset of puberty in Brahman bulls with respect to B. taurus was attributed to a longer duration of the prepubertal period (interval from start of spermatogenesis to puberty) and a later start of spermatogenesis. #
Reproduction, 1997
In bull calves serum concentrations of LH, FSH, and to a lesser extent testosterone, are increased transiently, between 6 and 20 weeks of age. The function of gonadotrophin and testosterone secretion in this period of growth and development was tested by injecting five Hereford bull calves with a GnRH agonist (15 mg Leuprolide acetate) i.m. at 6, 10 and 14 weeks of age; five vehicle treated calves acted as controls. On the basis of blood samples taken every 15 min for 10 h, at 12 weeks of age, mean serum concentrations of LH, FSH and testosterone and LH and FSH pulse frequency and amplitude were decreased (P < 0.05) by Leuprolide acetate. At 24 weeks of age, mean serum concentrations of LH, and LH and FSH pulse frequency in Leuprolide acetate treated calves exceeded (P < 0.05) that seen in control calves. On the basis of blood samples taken every other week, treatment with Leuprolide acetate decreased mean serum concentrations of FSH and testosterone at 14, 16 and 18 weeks of age compared with control calves and delayed the peak of the early increase in LH secretion from 20 to 24 weeks of age (P < 0.05). Scrotal circumference between 22 and 50 weeks of age, pixel units from ultrasound images of the testes, testis mass at castration at 50 weeks of age, and numbers of spermatids and pachytene spermatocytes were all lower in Leuprolide treated calves than in controls. A transient increase in secretion of LH, FSH and testosterone in young bull calves before 20 weeks of age may, therefore, be a critical step in the initiation and timing of testicular development in bull calves.
The Open Anatomy Journal, 2010
Some morphometric parameters of the buffalo gonad and epididymis were compared in the mating (late autumn-winter) versus non-mating (late spring to the beginning of autumn) seasons. Organs from mature bulls of proven fertility were collected at slaughtering in February and September and used for this study. Testicular and epididymal diameters and weights were measured. The diameters of the testicular seminiferous tubules, as well as the diameters of the ductal lumen in sections taken from caput, corpus and cauda, were compared on haematoxylin and eosin-stained sections. The height of epididymal principal cells was also measured, from the basement to the apical membrane. The data obtained in the two seasons were analyzed by ANOVA, co-variating the histometric data for testicular and epididymal weight, respectively. Season-related differences were observed. Testicular and epididymal weights were higher during the mating period, as well as the organ lengths. Spermatogenesis was conserved in the resting period, but the testis showed smaller tubular diameters. In the epididymal caput and corpus the tubular diameters and epithelial cell height were significantly diminished in summer. On the contrary, tubular diameter and epithelial cell height of cauda epididymis increased during the summer, due to accumulation of non-ejaculated spermatozoa. Seasonal variations of genitalia recorded in buffalo bulls could represent an interesting aspect affecting fertility, which might influence the quality of semen and, in turn, the chance of cryopreservation. Morphometric studies of reproductive organs could contribute to better develop the reproductive potential in this species.
Testicular development and its relationship to semen production in Murrah buffalo bulls
Theriogenology, 2003
The objectives of this study were to determine the relationship of age and body weight to testicular development and to establish norms for breeding soundness evaluations of Murrah buffalo bulls. Testicular measurements of 133 Murrah buffalo bulls of various ages were recorded with a caliper and a tape. Semen was collected twice a week for 5 weeks from groups of bulls which were 25±36 (n 17), 37±48 (n 16), 49±60 (n 14), of >60 (n 10) months of age. After examining volume, sperm concentration, and progressive motility semen was diluted in Tris±citric acid±egg yolk± fructose extender and frozen in 0.5 ml French straws. Testicular measurements of buffalo bulls were lower than those recorded for European breeds of cattle bulls. Nevertheless, like cattle bulls, scrotal circumference was highly correlated with other testicular measurements. Also, it had a signi®cant positive relationship with semen volume and sperm concentration per ejaculate. Average sperm output per week in order of increasing age group was 15.3, 18.2, 19.8 and 23:6 Â 10 9. Corresponding values for sperm output per week per gram of testis were 59.1, 45.8, 41.1, 36:2 Â 10 6 indicating a reduction in spermatogenesis per unit of testis with advancing age. Compared to European breeds, daily sperm output in Murrah bulls was nearly 45% lower, presumably due to their nearly 40% lower scrotal circumference than Holstein bulls of the same age. These results indicate that in buffalo, as in cattle, scrotal circumference is a useful indicator of potential sperm output and may serve as an important criterion for selecting young bulls as AI sires.
Testicular function and fertility in bulls
Bioscientifica Proceedings, 2019
Since one bull may be responsible for impregnating numerous cows, testicular function and fertility are of critical importance. Within this broad context, this review will focus on: the effects of nutrition on reproductive development; scrotal/testicular thermoregulation; breeding soundness; and sperm function/fertility. Bulls fed above-maintenance levels of energy and protein before 30 wk of age had increased luteinizing hormone pulse frequency, hastened puberty, and increased testicular size at maturity (compared to those that were underfed during this interval). However, after 30 wk of age, supplemental nutrition generally did not improve reproductive potential (but sometimes decreased it). There are several mechanisms (including blood vessels) that maintain a bull's testes 2 to 6 0 C cooler than core body temperature for production of fertile sperm (increased testicular temperature reduces semen quality). Although fertility varies substantially among bulls, it is generally easier to identify bulls with low fertility than to accurately distinguish among bulls with good to excellent fertility. Compensable sperm abnormalities can be overcome by increasing the number of sperm used for artificial insemination; these abnormalities are attributed to sperm failing to reach and penetrate the zona pellucida. In contrast, increasing the insemination dose will not improve fertility for uncompensable defects, implying that these sperm are able to cause fertilization and initiate development, but they do not sustain embryogenesis. Al Naib A, Hanrahan JP, Lonergan P & Fair S 2011. In vitro assessment of sperm from bulls of high and low field fertility. Theriogenology 76 161-167. Amann RP & DeJarnette JM 2012. Impact of genomic selection of AI dairy sires on their likely utilization and methods to estimate fertility: a paradigm shift. Theriogenology 77 795-817. Arangasamy A, Kasimanickam VR, DeJarnette JM & Kasimanickam RK 2011. Association of CRISP2, CCT8, PEBP1 mRNA abundance in sperm and sire conception rate in Holstein bulls. Theriogenology 76 570-577. Barros CMQ, Oba E, Brito LFC, Cook RB, Coulter GH, Groves G, Olson M & Kastelic JP 1999. Avaliação do fluxo sanguineo e do oxigenio testicular em touros Aberdeen Angus [Testicular blood flow and oxygen evaluation in Aberdeen Angus bulls]. Revista Brasileira de Reprodução Animal 23 218-220. Barth AD, Brito LFC & Kastelic JP 2008. The effect of nutrition on sexual development of bulls. Theriogenology 70 485-495. Bratton RW, Musgrave SD, Dunn HO & Foote RH 1959. Causes and prevention of reproductive failure in dairy cattle: II. Influence of underfeeding and overfeeding from birth to 80 weeks of age on growth, sexual development, and semen production in Holstein bulls. Bulletin 940.
2005
In the present study, the testes of 32 bovine embryos with different crown-rump length (2.5- 90 cm CRL) and of 15 sexually mature bulls (Deutsches Fleckvieh) were investigated using light- and electron microscope as well as glycohistochemical and immunohistochemical methods. The gestation period was divided into 3 stages; early, mid, and late gestation. Developmental changes in the testicular morphogenesis were therefore analyzed in details during these phases. Generally, embryonic development of bovine testis involves the same mechanism described in other mammals. At the first stage of this study (2.5 cm CRL/43 dpc), the anlage of the testes protruded to the coelomic cavity as paired bean-shaped structures on either side of the dorsal mesentery medial to the mesonephros. It consists of primitive testicular cords, interstitium, and rete testis blastema. Proceeding with fetal age, these basic testicular structures are further differentiated. The tunica albuginea is separated into two...
Animal Reproduction Science, 1998
. Twenty Holstein-Friesian breeding bulls 62-79 months of age were examined 3 times, at Ž . 30-day intervals. Scrotal thermograms for assessment of scrotal surface temperature SST and blood samples for plasma testosterone concentrations were taken just before and then 45 and 90 Ž . min, respectively, after treatment with GnRH 50 mg, Gonavet, i.m. per bull . Following GnRH Ž treatment, there generally were significant increases in mean values of both top SST range, y0.1 . Ž . to 1.48C and bottom SST range, 0.3 to 1.88C . Scrotal circumference was highly repeatable but SST and video-measurements of scrotal dimensions were less repeatable, because apparently they were affected by ambient temperature. Plasma testosterone concentrations before GnRH treatment were more repeatable than those after GnRH treatment. Correlations between examinations of 0.67 to 0.81 and y0.14 to 0.47, respectively, but the converse was true for SST measurements. Semen was collected with an artificial vagina 3 times per week for 12 weeks starting 2 weeks before the first examination. The total number of spermatozoa per ejaculate was highly repeatable and the percentage of motile and live spermatozoa were relatively consistent. Separate regressions for each variable and for each examination were conducted for these 3 semen characteristics as dependent ) Corresponding author. 0378-4320r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.