Scrotal width as an index of testicular size in dogs and its relationship to body size

Measurements of scrotal width were strongly correlated with testicular weight in 71 dogs (r = 0–919) and thus provided a convenient index of testicular size and potential sperm production. However, to be useful in trying to predict male fertility this measurement had to be adjusted for bodyweight. A graph is presented which allows estimation of ‘average’ scrotal width and its 95 per cent confidence limits for potentially fertile dogs of bodyweight between 5 and 50 kg. With one exception, dogs with scrotal widths below the 95 per cent confidence limits had very few or no spermatozoa in smears from the cauda epididymidis.     

Evaluation of American Wagyu sires for scrotal circumference by age and body weight

Thirty-six percent of American Wagyu bulls do not meet the current minimum standards set by the Society of Theriogenology for the breeding soundness exam. In contrast, only 15% of bulls of domestic breeds do not meet the minimum standards. Scrotal circumference measurements of Wagyu are smaller than those of other breeds. The objective of this research was to describe scrotal circumference of Wagyu bulls as it relates to age and BW. The data set consisted of 190 Wagyu bulls housed at two locations. One hundred forty-one bulls constituted the first set of data (location 1); scrotal circumference was measured one to six times per bull aged between 13 and 70 mo. Ninety-four of the bulls underwent semen evaluation for motility and morphology. Forty-nine bulls constituted the data set for which scrotal circumference and BW was measured one to nine times per bull between 5 and 21 mo of age (location 2). Mean scrotal circumference of bulls within each age group was as follows: 12 to 14 mo, 29.8 0.2 cm (mean +/- SE); 15 to 17 mo, 31.8 +/- 0.2 cm; 18 to 20 mo, 32.9 +/- 0.3 cm; 21 to 24 mo, 31.8 +/- 0.5 cm; and > 24 mo, 35.5 +/- 0.2 cm. Both age and BW were highly correlated to scrotal circumference (r = 0.81 and 0.82, respectively). Within each age group, there were a percentage of bulls that did not meet the minimum standard for scrotal circumference set by the Society of Theriogenology. The percentages were as follows: 12 to 14 mo, 46%; 15 to 17 mo, 25%; 18 to 20 mo, 33%; 21 to 24 mo, 42%; and > 24 mo, 32%. Morphology and motility were > 50% each in 91% of the bulls between ages 12 and 20 mo at location 1. Based on these data, it is recommended that Wagyu bulls be evaluated with the breed-specific minimum standards for scrotal circumference of 26 cm from 12 to 14 mo, 29 cm from 15 to 17 mo, and 30 cm from 18 to 20 mo of age.     

Survey with follow-up of 67 dogs with testicular sertoli cell tumours

Sixty-seven cases of canine sertoli cell tumour are reviewed. The mean age at diagnosis was 9.5 years (sd +/- 2.1, range 3 to 17). The most commonly affected breeds were boxer, cairn terrier, labrador retriever, border collie, German shepherd and rough collie. The left side was affected in 28 dogs (42 per cent), the right in 35 (52.5 per cent) and both sides in four (6 per cent). Twenty testicles were abdominal (left, seven; right, 13), seven were inguinal (left, four; right, three) and 44 were scrotal (left, 21; right, 23). Hormonal signs were evident in 38 (57 per cent) animals (feminisation with alopecia in 21, symmetrical alopecia alone in 17). Other types of testicular tumours were found in 12 dogs (18 per cent) of this series. Of 42 dogs which were castrated and discharged, 38 were available for follow-up study and survived for between one week and five years. Two of the 15 dogs which were subject to post mortem examination had metastases. Two others which died after failure of remission, or a recurrence of the hormonal changes probably also had metastases. Two of the 25 dogs which were presented initially for other reasons, but had sertoli cell tumours, were found to have metastases post mortem. The boxer, cairn terrier, border collie, Shetland collie and pekingese had a higher risk of sertoli cell tumour than other breeds.     

Relationships among scrotal and testicular characteristics, sperm production, and seminal quality in 129 beef bulls.

Standard breeding soundness examinations plus measurement of scrotal surface temperature (SST), internal/scrotal testicular temperatures, testicular ultrasonographic echotexture, daily sperm production, and epididymal sperm reserves were conducted on 129, 16-month-old crossbred beef bulls. There were significant positive linear correlations between SST and internal scrotal/testicular temperatures, a positive linear regression (P < 0.06) of bottom SST with the incidence of secondary sperm defects, but a negative linear regression (P < 0.01) with the incidence of primary sperm defects. Testicular echotexture had a positive linear regression with daily sperm production (P < 0.002) and testicular tone had a negative linear regression (P < 0.008) with epididymal sperm reserves. Scrotal circumference had a positive linear regression (P < 0.04) with the percentage of progressively motile sperm, a negative linear regression (P < 0.1) with the incidence of primary sperm defects, and a positive linear regression (P < 0.0001) with epididymal sperm reserves. In addition to seminal quality and scrotal circumference, testicular ultrasonographic echotexture has considerable promise for augmenting breeding soundness examinations of bulls.     

Effect of repeated implantation with anabolic agents on growth rate, carcase weight, testicular size and behaviour of bulls

The effects of implantation with different anabolic agents on growth rate, behaviour, carcase parameters and testicular size of bulls were evaluated in an experiment with 361 Friesian bulls about three months old on three farms. Animals were allocated to one of the following treatments: (a) Control; (b) repeated implantation with 36 mg zeranol at intervals of 95 to 124 days; (c) repeated implantation with 20 mg oestradiol benzoate plus 140 mg trenbolone acetate as in (b); (d) repeated implantation with 20 mg oestradiol benzoate plus 200 mg progesterone as in (b); (e) implanted once with 45 mg oestradiol-17 beta. Daily liveweight gain, carcase weight, testicular size and behaviour of the animals were the parameters measured. Repeated implantation of young bulls with hormones, beginning at eight to 10 weeks old, increases liveweight gain and carcase weight from 0 to 15 per cent, reduces aggressive behaviour and testicular size and, in some instances, improves conformation and increases fat cover of the carcase.     

The effects of active immunization against gnRH on testicular development, feedlot performance, and carcass characteristics of beef bulls

The objective was to determine the effects of a recombinant fusion protein anti-GnRH vaccine on testicular development, feedlot performance, and carcass quality of beef bulls. Crossbred beef bulls (n = 58, average weight 306 kg, 9 mo of age), were randomly allocated to two groups and received either an anti-GnRH vaccine (GnRH) or placebo (Control) by intramuscular injection on d 0, 56, and 112. There were group effects (P < 0.01; as a percentage of Control) on testicular weight (53%), daily sperm production (40%), and epididymal sperm reserves (16%). There were group x time interactions (P < 0.0001) for scrotal circumference and serum testosterone concentrations; at slaughter, bulls in the GnRH group had a smaller (P < 0.05) scrotal circumference (28.3 vs 33.9 cm) and lower (P < 0.05) serum testosterone concentrations (2.2 vs 8.6 ng/mL) than those in the Control group. Average daily gain, feed intake, and feed efficiency were not different between treatments during the backgrounding phase (d 0 to 84). During the finishing phase (d 98 to 182), ADG was greater (P < 0.05) for bulls in the Control group (1.69 vs 1.42 kg/d), as was carcass weight (6.9%; P < 0.01). However, GnRH bulls had numerically better feed efficiency (6.12 vs 7.08 kg DMI/kg gain; P < 0.23) and shear force values for ribeye that were 16% lower (P < 0.14) than Control bulls, warranting further investigation. Vaccinating bulls against GnRH suppressed testicular function, with growth and carcass characteristics similar to that expected with steers.     

Testicular traits as selection criteria for young Nellore bulls

The objective of this study was to evaluate the possible use of biometric testicular traits as selection criteria for young Nellore bulls using Bayesian inference to estimate heritability coefficients and genetic correlations. Multitrait analysis was performed including 17,211 records of scrotal circumference obtained during andrological assessment (SCAND) and 15,313 records of testicular volume and shape. In addition, 50,809 records of scrotal circumference at 18 mo (SC18), used as an anchor trait, were analyzed. The (co)variance components and breeding values were estimated by Gibbs sampling using the Gibbs2F90 program under an animal model that included contemporary groups as fixed effects, age of the animal as a linear covariate, and direct additive genetic effects as random effects. Heritabilities of 0.42, 0.43, 0.31, 0.20, 0.04, 0.16, 0.15, and 0.10 were obtained for SC18, SCAND, testicular volume, testicular shape, minor defects, major defects, total defects, and satisfactory andrological evaluation, respectively. The genetic correlations between SC18 and the other traits were 0.84 (SCAND), 0.75 (testicular shape), 0.44 (testicular volume), -0.23 (minor defects), -0.16 (major defects), -0.24 (total defects), and 0.56 (satisfactory andrological evaluation). Genetic correlations of 0.94 and 0.52 were obtained between SCAND and testicular volume and shape, respectively, and of 0.52 between testicular volume and testicular shape. In addition to favorable genetic parameter estimates, SC18 was found to be the most advantageous testicular trait due to its easy measurement before andrological assessment of the animals, even though the utilization of biometric testicular traits as selection criteria was also found to be possible. In conclusion, SC18 and biometric testicular traits can be adopted as a selection criterion to improve the fertility of young Nellore bulls.     

Effects of testicular biopsy in clinically normal bulls

OBJECTIVE: To determine whether testicular needle biopsy is detrimental to testicular function in clinically normal bulls. DESIGN: Prospective study. ANIMALS: 6 mixed-breed mature bulls. PROCEDURE: A randomly selected testicle from each bull was biopsied with a 14-gauge needle biopsy instrument. Bulls were then evaluated over a 90-day period for changes in scrotal temperature and thermal patterns, ultrasonographic appearance, and quality of spermatozoa. At the end of the 90-day study, bulls were castrated, and testicles were examined grossly and histologically. RESULTS: Changes were detected in scrotal temperatures and thermal patterns and in the breeding soundness examination results during the first 2 weeks of the study. However, there were no long-term changes in semen quality over the course of the experiment. Hyperechoic areas were detected on ultrasonographic examination and corresponded to the areas of penetration by the biopsy instrument. Microscopic lesions that were indicative of testicular dysfunction were not found. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that testicular biopsy is a safe procedure in bulls. Testicular biopsy could possibly be used to further examine bulls that have less than satisfactory results for breeding soundness examinations.     

The relationship between scrotal circumference at weaning and at one year of age in beef bulls

Scrotal circumference data obtained from performance test station bulls were corrected to 240 and 365 days of age. Data were analyzed, retrospectively, to determine the outcome for scrotal circumference at 365 days of age, if bulls were culled at selected cut-off values for scrotal circumference at 240 days of age. The data indicate that scrotal circumference measurements in weaned bulls may not be useful as a culling tool, since a large proportion of bulls, irrespective of breed, fell below the selected cut-off measurement for scrotal circumference at weaning, but met the minimum scrotal circumference at one year of age. Scrotal circumference measurements at 240 days of age may, however, be useful as a tool for selecting bulls with a greater than 80% probability of achieving the minimum scrotal circumference measurement at one year of age.     

Growth and pubertal development of F1 bulls from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu sires

The objective of the study was to characterize body growth, testicular development, and puberty from 8 to 14 mo of age in bulls (n = 120) produced by mating sires from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu breeds to MARC III ((1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) cows. Traits evaluated were birth weight, weaning weight (at 215 d), yearling weight, ADG from 8 to 14 mo of age, paired testicular volume growth from 8 to 14 mo of age, age at puberty (determined by production of 50 x 10(6) sperm with 10% motility), age at freezable semen (determined by production of 500 x 10(6) sperm with 50% motility), and, at 15 mo of age, paired testicular weight and daily sperm production per testis pair. There was an effect of sire breed (P = 0.03) for age at puberty; animals with Wagyu and Swedish Red and White inheritance reached puberty at a later date (302 and 302 d of age, respectively) compared with Angus-sired bulls (268 d). Age at puberty for Hereford-, Norwegian Red-, and Friesian-sired bulls was 270, 271, and 278 d, respectively. Differences in BW were observed (P = 0.03) at birth; bulls with Hereford and Friesian were heavier at birth (43 and 41 kg, respectively) compared with those with Norwegian Red, Swedish Red and White, and Wagyu inheritance (39, 38, and 38 kg, respectively). Differences in BW were also observed at 1 yr of age (P = 0.001), where the heaviest animals were those sired by Angus (450 kg), whereas the lightest animals were those sired by Wagyu (403 kg). Bulls with Wagyu inheritance had the lowest (P = 0.04) ADG (1.12 kg/d) compared with bulls with inheritance from Hereford (1.22 kg/d), Angus (1.28 kg/d), Norwegian Red (1.24 kg/d), Swedish Red and White (1.25 kg/d), and Friesian (1.27 kg/d). Differences in scrotal growth rate were not significant (P = 0.99). They ranged from 1.95 in Angus-sired to 1.66 cm3/d in Wagyu-sired bulls. There were no differences (P = 0.80) for age at freezable semen (335 +/- 10 d). At slaughter (15 mo of age), there were no differences (P = 0.62) for paired testicular weight (603 +/- 28 g) and daily sperm production (10.6 x 10(9) +/- 0.9 x 10(9) per testis pair). Growth of bulls with Wagyu inheritance was slower, and bulls with Wagyu or Scandinavian inheritance reach puberty at an older age than bulls with Angus inheritance.     

Some nutritional and genetic considerations in the performance testing of beef bulls

Performance testing started after it was recognized that growth traits were heritable. In the early years of performance testing there was a tendency to feed higher levels of energy for longer periods of time. More recently, the trend has been to feed lower levels of energy for shorter periods. There are still differences in opinion as to the appropriate level of energy to use. Although it is important that the level of energy fed is adequate to correctly establish a bull's ability to gain, it is essential to know that it will pose no risk of impaired spermatogenesis or cause any degree of laminitis. Clinical observations and research on overfeeding clearly show that both libido and spermatogenesis can be impaired by excess energy intake. The damage in 2-year-old bulls can be very extensive and in some animals it may not be reversible. The scant amount of research in yearling bulls indicates that there is considerable potential danger from overfeeding energy as well. Test stations are under used in regard to performing research that would help identify heritable defects that would interfere with the productive and reproductive efficiency of beef cattle. The first performance testing programs emphasized average daily gain from weaning to 1 year of age, so "performance" has traditionally meant rate of gain to most cattle raisers. The term "performance" is now starting to acquire a broader and more inclusive definition. For many breeders, it now includes weight per day of age, which is in part a maternal trait, and some kind of male evaluation for reproductive potential that can also be extrapolated to the female side. One of the first breakthroughs in this regard was to recognize the heritability of testicular size, and that testicular size could be fairly accurately determined by scrotal circumference measurement. It was also found that there was a favorable relationship between larger testicle size and the ability to produce high quality semen. As a result, it became a common practice to include scrotal circumference measurements in the published bull test results. However, many test station patrons were, and still are, content to consider the scrotal circumference measurement alone as an evaluation of a bull's breeding potential. Unfortunately, less than half of the bulls finishing a performance test at ages ranging from 11 to 14 months will be able to produce semen of completely acceptable quality.(ABSTRACT TRUNCATED AT 400 WORDS)     

Intratesticular morphometric, cellular and endocrine changes in dromedary bulls exhibiting azoospermia

Twenty bulls, aged 7-12 years and selected from six dromedary farms were used in this study. Fifteen previously fertile animals were divided into fertile (controls) and infertile groups on the basis of abnormal scrotal contents following palpation and azoospermic ejaculates collected by electroejaculation. An examination of the clinical and histological findings as well as the testicular patterns of oestradiol-17beta, testosterone and histamine indicated that three bulls displayed normal ranges comparable to the controls but with bilateral spermatocoeles in the caput epididymides in conjunction with the soft texture of the testicles. Seven bulls showed moderate testicular firmness and springiness, a marked increase in testicular oestradiol-17beta and histamine concentrations, and increases in surface area, density of mast cells and percentages of seminiferous tubules containing premeiotic spermatogenic cells as well as decreases in testicular testosterone concentrations, surface area of Leydig cells and diameter of the seminiferous tubules. The remaining five infertile animals had small hard testicles, supranormal testicular testosterone concentrations, baseline values of testicular oestradiol-17beta and histamine, decreased numbers of Sertoli and mast cells, with a predominance (98.2%) of seminiferous tubules containing spermatogonia resting on a thickened tubular basement membrane. The results provide information on the relationship between gonadotrophin, testicular oestrogen, androgens and histamine as well as spermatogenesis in normal and azoospermic dromedary bulls.     

Growth and pubertal development in Brahman-, Boran-, Tuli-, Belgian Blue-, Hereford- and Angus-sired F1 bulls

Growth and testicular development between 7 and 15 mo of age were evaluated in bulls produced by mating sires of six breeds (Hereford, Angus, Belgian Blue, Brahman, Boran, and Tuli) to Angus, Hereford, and MARC III (four-breed composite) cows. At 12 mo of age, Angus- and Hereford-sired bulls had the heaviest body weight (P < 0.08 to 0.001), whereas Brahman- and Belgian Blue-sired bulls were intermediate, and Boran- and Tuli-sired bulls weighed the least. Bulls sired by European breeds grew more rapidly after weaning (P < 0.01) than did Brahman-, Boran-, and Tuli-sired bulls, and these differences in growth rate were maintained through 15 mo of age, indicating that offspring of heat-adapted sire breeds (Brahman, Boran, and Tuli) have lower postweaning rates of gain, particularly during winter months, than do offspring of nonheat adapted sire breeds. Testis size was smaller initially (P < 0.01) and remained smaller in offspring of heat-adapted sire breeds through yearling age. By 15 mo of age, testis size was largest (P < 0.06 to 0.001) in Angus-sired bulls and had become similar among Hereford-, Brahman-, Boran- and Belgian Blue-sired bulls but remained smaller (P < 0.02 to 0.001) in Tuli-sired bulls. Thus, offspring of heat-adapted sire breeds had delayed testicular development compared with that of nonheat adapted sire breeds, particularly through yearling age. At puberty, Angus-sired bulls were 23 to 82 d younger (P < 0.05 to 0.001) than all other sire breeds except Hereford, and Brahman-sired bulls were older at puberty (P < 0.05 to 0.001) than were bulls of all other sire breeds except Boran. Testis size at puberty was quite similar among breeds of bulls (scrotal circumference = 27.9 +/- 0.1 cm) despite large breed differences in age, body weight, and hip height. Thus, measurement of yearling testis size was a reliable indicator of age at puberty among widely divergent breeds of bulls. In addition, the lower postweaning rates of gain and the smaller and slower testicular development in offspring of heat-adapted sire breeds should be noted by cattle producers considering use of such breeds in crossbreeding and breed improvement programs.     

Ultrasonography for monitoring reproductive function in the bull

Diagnostic ultrasonography has been widely used for examination of the reproductive tract of female cattle, but more sparingly in bulls. Typical clinical ultrasonographic examinations of bull testes are unlikely to affect semen quality or sperm production. The ultrasonographic anatomy of bull testes and accessory sex glands has been reported. Although testicular echogenicity increased (i.e. the parenchyma appeared more white) as a bull approached puberty, echogenicity was not superior to scrotal circumference as a predictor of puberty. Ultrasonography can be used to detect and characterize testicular pathology. It is noteworthy that areas of increased echogenicity (testicular fibrosis) are common, especially in young bulls, but are not associated with decreased semen quality (e.g. percentage of morphologically abnormal sperm). Neither visual evaluation nor computerized pixel analysis of testicular ultrasonic echotexture was consistently predictive of semen quality in bulls. Therefore, we concluded that the primary clinical use of ultrasonography in assessment of reproductive function in the bull is characterization of grossly detectable lesions in the testes and scrotum.     

Endocrine,growth, and carcass characteristics of bulls immunized against luteinizing hormone-releasing hormone fusion proteins

This study evaluated the effectiveness of a LHRH fusion protein vaccine on endocrine changes, feedlot performance, and carcass quality of bulls compared with steers and hormone-implanted steers. Crossbred bulls (n = 30; mean weight, 179 +/- 4 kg; mean age, 130 +/- 2 d) were randomly assigned to three treatment groups: 1) castrated (castrated; n = 10); 2) castrated-implanted with trenbolone acetate (implanted; n = 10); and 3) immunized against a cocktail of recombinant fusion proteins, ovalbumin-LHRH-7 and thioredoxin-LHRH-7 (immunized bulls; n = 10). Blood was collected every 2 wk to evaluate antibody and hormone concentrations. Serum LHRH antibodies (P < 0.001) were detected in animals of the immunized group, which had reduced serum LH concentrations (P < 0.001) compared with the castrated groups and serum FSH concentrations, which did not decrease but were significantly different when compared with castrated and implanted animals. Serum testosterone concentrations in the immunized bulls were not different from the two castrated groups (P > 0.05) by d 60 after primary immunization. Initial mean scrotal circumference of the immunized bulls was 18.0 +/- 0.6 cm on d 0 and increased to 22.6 +/- 1.3 cm by d 310. No differences (P > 0.05) in ADG were observed among treatment groups. Immunized animals had an intermediate BW gain (P > 0.05) when compared with the castrates, whereas the castrated groups differed (P < 0.05) from each other. Carcass characteristics were similar (P < 0.05) among the three groups. Vaccinating bulls against a LHRH fusion protein cocktail suppressed LH and testosterone, which led to reduced testicular development and no bullock carcasses. Growth and carcass characteristics of the immunized animals were similar to the steers.     

Scrotal circumference, seminal characteristics, and testicular lesions of yearling Angus bulls

The effect of age and body weight on scrotal circumference (SC), the effect of SC on percentage of sperm abnormalities and seminal characteristics, and the relationship of SC with testicular weight, epididymidal weight, degree of germinal epithelial loss (DGEL), and percentage of tubules graded 4 or greater (G4+) were studied in 37 Angus bulls. All bulls were from one herd and were examined at monthly intervals, during a 140-day weight gain test starting when they were 11 months old. The study was terminated when the bulls were slaughtered at 14 months of age. As age and body weight increased, SC increased (P less than 0.001). The incidence of sperm abnormalities decreased (P less than 0.001) as SC increased; however, seminal characteristics remained poor in bulls with SC less than or equal to 32 cm. Pathologic changes in 600 cross sections of seminiferous tubules from each bull were classified into 9 grades. The DGEL per 100 tubules was calculated by assigning a value to each grade according to the severity of loss of germinal epithelium. Tubules classified as G4+ were devoid of germinal cells and provided an index of irreversible loss of germinal epithelium. The SC was correlated positively with testicular weight (r = 0.91, P less than 0.001) and epididymal weight (r = 0.59, P less than 0.001) and negatively with DGEL (r = -0.48, P less than 0.01) and G4+ (r = -0.44, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Testicular development, daily sperm production and epididymal sperm reserves in 15-mo-old Angus and Hereford bulls: effects of bull strain plus dietary energy

Bull calves (n = 143) were obtained from two strains of Angus and two strains of Hereford cattle for which replacements were selected on the basis of superior feedlot growth performance on either high- or medium-energy diets. From weaning to slaughter at 15 mo of age, bulls were fed either the high-energy (80% grain + 20% forage) or medium-energy diet (100% forage) corresponding to their strain. Bulls in high-energy diet groups had a greater (P less than .05) scrotal circumference at 12 mo, but not 15 mo of age, than bulls in medium-energy diet groups. Compared with Hereford bulls, Angus had greater (P less than .01) scrotal circumference (36.1 vs 33.9 cm) and greater (P less than .05) paired testes weight (570 vs 464 g) at 15 mo of age. Daily sperm production per gram testicular parenchyma (DSP/g) was affected by strain-diet (P less than .01) but not by breed. Bulls in medium-energy diet groups had 12% greater DSP/g than did high-energy diet bulls (17.4 X 10(6) vs 15.5 X 10(6)). Daily sperm production (DSP) was 9% and 30% greater (P less than .01) for medium-energy diet bulls in 1980 (8.2 X 10(9) vs 7.5 X 10(9)) and 1981 (8.0 X 10(9) vs 6.2 X 10(9)), respectively, compared with high-energy diet bulls. The effect (P less than .01) of breed on DSP was attributed to breed differences in paired testes weight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects on testosterone, LH and cortisol concentrations, and on testicular ultrasonographic appearance of induced testicular degeneration in bulls.

It is well known that heat stress has a detrimental effect on testicular functions. In addition to the alteration of semen quality and testicular damage, reproductive hormone secretion can be altered. The objective of this study was to describe changes in plasma concentrations of testosterone, LH and cortisol, as well as in testicular ultrasonographic appearance after induced testicular degeneration. Four Swedish Red and White bulls, aged 3 years, were used. They were fed according to Swedish standards. The scrotum was covered with an insulation device during 96 h. Semen was collected weekly 3 times before and up to 4 months after insulation. Testicular ultrasonography and clinical genital examination were performed with the same intervals. Heparinized blood samples were taken from the jugular vein at 2 h interval during 24 h every 2 weeks during the study. Blood samples were tested for the content of testosterone, LH and cortisol. Data were analysed, using one way analysis of variance of seminal data, clinical examination data as well as 24 h hormonal output data as percentage of mean individual pretreatment values. The use of a 5 MHz B-mode ultrasound unit did not contribute with an objective estimation of the degree of testicular degeneration. In 3 of the bulls testosterone levels had a tendency to decrease and LH to increase during the time of severe degeneration, whereas an opposite trend was seen during the regenerative phase, changes becoming significant 15 weeks after scrotal insulation. Variation between animals was big. Cortisol levels had a decreasing trend, changes being significant only in individual bulls at 10 and 15 weeks after scrotal insulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of location and season on body and testicular growth in Brahman and Hereford bulls

To determine the effects of location and season on growth of bulls, Hereford bulls from Montana (MH; n = 15) and Nebraska (NH; n = 15) and Brahman bulls from Texas and Louisiana (BB; n = 18) were moved to three locations: Montana (MT), Nebraska (NE) or Texas (TX). Each location received 5 NH, 5 MH and 6 BB. Control bulls (not relocated) were maintained at each location. All bulls were pubertal at the time of relocation in May 1984. At 28-d intervals, body weight, hip height, testis length and scrotal circumference were recorded for each bull for 22 mo after relocation. Paired testes volume (PTV) was calculated. Among Hereford bulls, body weights were similar (P greater than .10) in all control and relocated bulls by the end of the study, except that MH bulls moved to TX had lower body weights (P less than .01). Brahman bulls moved to northern locations had dramatically reduced body weights, compared to control Brahmans kept in TX; body weight of Brahman bulls in MT remained lower (P less than .01) at the end of the study. Brahman bulls in NE and MT had smaller scrotal circumference and PTV (P less than .01) than did control Brahmans in TX during the 1st yr after relocation. Relocated BB exhibited marked seasonal fluctuations in testis size, with increases during the summer and decreases during the winter (P less than .01); seasonal changes were not apparent in control Brahmans in TX. These results indicate that moving Brahman bulls to northern environments reduced body weight gain and caused dramatic seasonal changes in testis size; these effects were more pronounced in Brahman bulls moved to the most northern location.     

Effect of nutrition during calfhood and peripubertal period on serum metabolic hormones, gonadotropins and testosterone concentrations, and on sexual development in bulls

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 early gonadotropin rise (high nutrition) had greater testicular mass at 70 weeks of age relative to the control group (medium nutrition), despite no differences in metabolic hormone concentrations after 26 weeks of age. Therefore, gonadotropin-independent mechanism regulating testicular growth might be dependent on previous gonadotropin milieu.