Regulation of postnatal development of testes and its association with puberty and fertility - A review (original) (raw)
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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.
Journal of Animal Science, 2005
The objective was to compare testis characteristics of Zebu bulls treated with the GnRH agonist, deslorelin, at different times and for different durations during their development. An additional objective was to determine the usefulness of a stain for the transcription factor GATA-binding protein 4 (GATA-4) as a specific marker for Sertoli cell nuclei in cattle. Bulls (54) were allocated to nine groups (n = 6) and received s.c. deslorelin implants as follows: G1 = from birth to 3 mo of age; G2 = from 3 to 6 mo; G3 = from 6 to 9 mo; G4 = from 9 to 12 mo; G5 = from birth to 15 mo; G6 = from 3 to 15 mo; G7 = from 6 to 15 mo; G8 = from 12 to 15 mo; and G9 (control) = no implant. Bulls were castrated at 19 mo of age. Paraffin sections (10 m) were subjected to quantitative morphometry and GATA-4 immunohistochemistry. At castration, all bulls in the control group (6/6) had attained puberty (scrotal circumference ≥ 28 cm), whereas a smaller proportion (P < 0.05) had reached puberty in G2 (2/5) and G6 (1/ 6). Bulls in G2 and G6 also had a lesser (P < 0.05) testis
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. #
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.
Domestic Animal Endocrinology, 2007
The objective of the present study was to evaluate the effects of improved nutrition during calfhood on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls. Bulls received high (n = 17) or control nutrition (n = 16) diets from 10 to 30 week of age and the same control nutrition diet from 31 to 74 week of age. Improved nutrition during calfhood resulted in a more sustained period of elevated LH secretion (pulse frequency and total secretion in 10 h) during the early gonadotropin rise. GnRH-stimulated LH secretion was not affected by diet, indicating that pituitary responsiveness was not altered; therefore, improved nutrition had direct effects on GnRH secretion by the hypothalamus. Insulin and insulin-like growth factor-I (IGF-I) concentrations were greater during calfhood in bulls receiving high nutrition, indicating that these metabolic hormones might be involved in regulating GnRH and LH secretion. Improved nutrition also resulted in increased testosterone secretion that was associated with greater circulating IGF-I concentrations, suggesting a role for this metabolic hormone in regulating Leydig cell number and function. Furthermore, improved nutrition during calfhood resulted in greater testicular weight and sperm production in mature bulls, indicating that increased LH secretion during calfhood, and increased IGF-I and testosterone concentrations during calfhood and peripubertal period were associated with greater testicular cell proliferation and enhanced function.
Scientific Reports, 2019
Well-fed prepuberal Holstein bulls had larger testes, earlier puberty, higher LH, testosterone and IGF-1, earlier and more proliferating and differentiating Sertoli cells, and greater sperm production potential. The objective was to determine effects of pre-pubertal nutrition on mRNA expression of testicular genes. Holstein bull calves were fed high or low diets (20 or 12% crude protein, respectively and 71.6 or 64.4% Total Digestible Nutrients) from 2 wk, castrated at 8, 16, 24 and 32 wk and testicular mRNA extracted and sequenced. Differential expression of genes mainly occurred at 16 and 24 wk. At 16 wk, functional analysis (DAVID) of DE mRNA revealed common biological processes including "cholesterol" and "fatty acid biosynthesis," with most genes (including HMGCR, HMGCS1, HSD17) upregulated in high-diet bulls (P < 0.05). Major pathways enriched at 16 wk were "cholesterol biosynthesis", "steroid metabolism" and "activation of gene expression by Sterol regulatory element binding protein (SREBP)" (P < 0.05). In high-diet bulls, mature Sertoli cell marker Connexin 43, was upregulated at 16 wk and immature Sertoli cell marker (AMH) downregulated at 24 wk. There was an indirect interaction between insulin family receptor and most upregulated cholesterol biosynthesis genes. Pre-pubertal nutrition enhanced testicular cholesterol/steroid biosynthesis and Sertoli cell maturation. It is well established that supplemental feeding of bulls early in life enhances reproductive development 1-3. Pre-pubertal bull calves fed high nutrition (2-32 wk) had earlier puberty, larger testes and increased sperm production potential, without significant differences in sperm quality, compared to those on a low diet 4. In addition, high-nutrition bulls had increased serum concentrations of LH, testosterone and IGF-I 5. Earlier puberty and enhanced sperm production increase reproductive potential. However, cellular and molecular mechanisms underlying testicular changes in response to pre-pubertal nutrition remain largely unknown. The pre-pubertal period (8-20 wk) in bulls is characterized by transient increases in peripheral gonadotropin concentrations and parallel increases in testosterone 1,6. Serum LH concentrations start increasing during the late infantile period (4-5 wk), peak at ~12-16 wk and decline at ~25 wk 1,6. In addition, serum FSH concentrations also increase during the pre-pubertal period in a non-pulsatile fashion, albeit not to the same extent as LH 6. The magnitude of this early gonadotropin rise is crucial to initiate and support reproductive development in bulls 1. Although testis growth is slow during the pre-pubertal period, it accelerates as puberty approaches, despite relatively low gonadotropin concentrations. Perhaps mechanisms triggered by early gonadotropin release or gonadotropin-independent mechanisms regulate testicular development in bulls. There are major cytological and histological changes in bull testes during the pre-pubertal period. At ~8 wk, fetal Leydig cells degenerate and adult Leydig cells populate the intertubular component. Mesenchymal cells, comprising the rest of the compartment, cease proliferation at ~16 wk and transform to Leydig cells that proliferate until 30 wk, followed by decreased mitosis 7. Steroidogenic enzymes and testosterone production are distinguishing features of mature Leydig cells 7. Sertoli cells, the predominant tubular cell type during this period, proliferate
2020
This study aimed to determine semen quality and seminal biochemicals at 1 ejaculate, puberty, and maturity of Holstein bulls administrated with GnRH, hCG and testosterone. Holstein male calves (n=16, 8 mo old) were divided into four groups, 4 in each. During 10-weeks interval, each animal was bi-weekly i.m injected with saline (2 ml), 2 ml GnRH, 1500 IU hCG, and 2 ml testosterone. Results indicated the earliest ages to 1 ejaculation, puberty, and maturity by hCG. Ejaculate volume was higher (P<0.05) by GnRH. Sperm motility and livability increased (P<0.05) by GnRH. Seminal total proteins (TP) and albumin (AL) decreased (P<0.05) by GnRH and hCG. Globulin (GL) and fructose decreased (P<0.05) by treatments in the 1 ejaculate. At puberty and maturity, TP, AL, and fructose increased (P<0.05) by treatments. GL increased (P<0.05) by GnRH and hCG. AL:GL increased by GnRH and testosterone at puberty, and by testosterone at maturity. Triglycerides in 1 ejaculation increased ...
Domestic Animal Endocrinology, 2007
The objective of the present study was to characterize the effects of nutrition on circulating concentrations of metabolic hormones, gonadotropins, and testosterone during sexual development in bulls. Nutrition regulated the hypothalamus-pituitary-testes axis through effects on the GnRH pulse generator in the hypothalamus and through direct effects on the testes. Pituitary function (gonadotropin secretion after GnRH challenge) was not affected by nutrition. However, nutrition affected LH pulse frequency and basal LH concentration during the early gonadotropin rise (10-26 weeks of age). There were close temporal associations between changes in insulin-like growth factor-I (IGF-I) concentrations and changes in LH pulse frequency, suggesting a role for IGF-I in regulating the early gonadotropin rise in bulls. The peripubertal increase in testosterone concentration was delayed in bulls with lesser serum IGF-I concentrations (low nutrition), suggesting a role for IGF-I in regulating Leydig cell function. Serum IGF-I concentrations accounted for 72 and 67% of the variation in scrotal circumference and paired-testes volume, respectively (at any given age), indicating that IGF-I may regulate testicular growth. Bulls with a more sustained elevated LH pulse frequency during the
Effects of nutrition on sexual development of bulls
In the last decades a series of attempts have been made to improve reproductive performance of bulls via optimizing nutrition. Although an increase in energy uptake during the post-weaning period of calves led to a faster growing rate, it had no positive effects on sexual development. In contrast, a high-nutrition diet during the prepubertal period reduced the age at puberty of the bulls and increased the size/weight of the testis and the epididymal sperm reserves. This faster sexual development was associated with an increased transient LH peak, which seemed to be mediated by an increase in serum IGF-I concentrations. However, the exact mechanisms responsible for the interaction between nutrition and the subsequent development of calves are still not clear. Sexual development of bull calves depends not only on nutrition of the calves after birth but also on the feed intake of their mothers during pregnancy. A high-nutrition diet fed to the mother during the first trimester has negative effects on the reproductive performance of their offspring. In summary, growth, health and reproductive performance can be improved by nutrition, but further studies are necessary to obtain a better understanding about the mechanisms responsible for this phenomenon.