Testicular ultrasonogram pixel intensity during sexual development and its relationship with semen quality, sperm production, and quantitative testicular histology in beef bulls

This study was conducted to evaluate testicular ultrasonogram pixel intensity during sexual development in bulls and to determine its relationship with semen quality, sperm production, and quantitative testicular histology. Beef bulls (N = 152) were examined from 14 - 26 to 70 - 74 wk of age in four different years. Testicular echogenicity increased during sexual development, but the pattern of change differed among years. Echogenicity increased between 26 and 42 to 46 wk of age in 2 yr, but increased considerably earlier in the other 2 yr, reaching maximum values at 34 wk of age. Because increased echogenicity was likely associated with testicular changes leading to initiation of spermatogenesis, these differences were difficult to explain considering that age at puberty did not differ significantly among years. When data were evaluated according to age normalized to puberty, echogenicity started to increase 16 to 12 wk before puberty and reached maximum values 4 wk before or at puberty. These results indicate that a certain developmental stage of the testicular parenchyma must be reached before puberty and that the composition of the parenchyma remained consistent after puberty. Testicular echogenicity was associated with sperm production, seminiferous tubule and epithelium area, and sperm morphology, but the associations were not consistent. Testicular echogenicity was a good indicator of pubertal and mature status, but was not superior to scrotal circumference. In conclusion, although testicular ultrasonogram pixel intensity analysis might be useful for research purposes, clinical application of this technology in the present form for bull breeding soundness evaluation is not justifiable.     

Effect of feeding a docosahexaenoic acid-enriched nutriceutical on the quality of fresh and frozen-thawed semen in Holstein bulls

The aim of the current study was to investigate the effect of feeding a DHA-enriched nutriceutical on the in vitro quality and sperm motility parameters of fresh and frozen-thawed bull semen assessed by CASA. Samples were obtained from nineteen Holstein bulls used for semen collection at Semen Production Center, Karaj, Iran. Control group (n = 10) were fed a standard concentrate feed while treatment group bulls (n = 9) had this standard feed top dressed with 100 g of a commercially available DHA-enriched nutriceutical. Semen quality was assessed on ejaculates collected at the baseline and after 5, 9, and 12 weeks of supplementation. Classical semen evaluation, assessment of sperm motility (subjective and computer-assisted), viability (eosin-nigrosin), and hypo-osmotic swelling test (HOST) were conducted. Semen volume, sperm concentration, and consequently total sperm output were not affected by dietary treatment (P > 0.05). Feeding the nutriceutical was indeed found to affect sperm motility parameters assessed by CASA after 9 weeks of trial. The treatment has improved total motility (P < 0.01), progressive motility (P < 0.05), average path velocity (P < 0.05), HOST-positive (P < 0.01), and proportion of rapid spermatozoa (P < 0.01) in the fresh semen of bulls. Moreover, the proportion of viable spermatozoa increased (P < 0.05) in the ejaculates collected from nutriceutical-fed bulls compared to the control after 12 weeks of feeding trial. The post-thawed HOST and sperm motility data obtained by CASA did not differ between two groups (P > 0.05). On the other hand, dietary supplementation did not affect body weight, BCS and scrotal circumference. Consequently, it can be concluded that dietary DHA supplementation or its precursors, improve in vitro quality and motility parameters of fresh semen assessed by CASA in Holstein bulls. However, this effect was not pronounced in frozen-thawed semen.     

Detection of bovine herpesvirus 1 and 5 in semen from Brazilian bulls

Bovine herpesvirus 1 (BoHV-1) and 5 (BoHV-5) are important pathogens of the respiratory and genital tract of cattle and may also affect the central nervous system and cause meningoencephalitis. Both virus types are estimated to be widely distributed in Southern Brazil. In the present study, BoHV-1 and/or BoHV-5 DNA were detected in bovine semen samples from two states of Brazil by two species-specific nested polymerase chain reactions (nPCRs). These nPCRs were used to assay 53 samples of fresh semen and 23 samples of frozen semen from breeding bulls. Viral DNA was detected in all 76 semen samples: all were positive for BoHV-5, whereas 34 of these were positive for BoHV-1 as well. Moreover, in five fresh and in 13 frozen semen samples—of a total number of 40 samples suitable for virus isolation—infectious BoHV-1 and/or BoHV-5 virus were detected. In conclusion, that both BoHV-1 and BoHV-5 were detected in bovine semen in Brazil highlighted the importance of examining bull semen in search for both agents to reduce the risk of transmitting these viruses.     

Effects of cryopreservation on the motile sperm subpopulations in semen from Asturiana de los Valles bulls

The aim of this study was to identify different motile sperm subpopulations in ejaculates from an autochthonous bull breed (Bos taurus) and to determine possible modifications in these subpopulations resulting from cryopreservation. Ejaculates were collected and cryopreserved following a conventional protocol. The overall sperm motility and the kinematic parameters of individual spermatozoa were evaluated in fresh ejaculates, after 4 h at 5 °C, and at 0 and 2 h postthaw. A multivariate clustering procedure separated 23,585 motile spermatozoa into four subpopulations: Subpopulation 1 showed medium velocity (VCL: 99.4 ± 17.8 μm/sec) and high progressiveness (LIN: 65.1 ± 14.0%); Subpopulation 2 included spermatozoa with high velocity (VCL: 148.7 ± 25.6 μm/sec) but a nonprogressive trajectory (LIN: 33.1 ± 10.5%); Subpopulation 3 represented slowly motile (VCL: 58.3 ± 24.3 μm/sec) and nonprogressive sperm (LIN: 39.6 ± 18.3%); and Subpopulation 4 included very rapid (VCL: 152.8 ± 25.7 μm/sec) and highly progressive sperm (LIN: 70.9 ± 13.7%). Subpopulation 4 was present in the greatest quantity in fresh ejaculates (36%), but after cooling, it significantly decreased (21%) concomitantly with an increase (P < 0.001) in Subpopulation 2 (from 21% in fresh to 34% in postcooled semen). After freezing and thawing, the overall sperm motility was reduced, mainly due to Subpopulation 2 decreasing from 34% after cooling to 14% after thawing. Differences among bulls in the frequency distribution of spermatozoa within subpopulations were evidenced after thawing by different proportions of spermatozoa in Subpopulations 2 and 4. The current results indicate that a structure of four sperm subpopulations may be a common characteristic of bovine ejaculates and that the cooling phase of cryopreservation seems to be the determinant of postthaw semen quality.     

Use of oxytocin and cloprostenol to facilitate semen collection by electroejaculation or transrectal massage in bulls

Two experiments were conducted with 24 bulls in which semen collection was attempted by transrectal massage (RM) and electroejaculation (EE). In experiment 1, bulls received the following treatments on successive semen collection days: saline 10 min prior to electroejaculation (control); saline 10 min prior to 2 min of transrectal massage followed by electroejaculation; cloprostenol (CLO) 10 min prior to 2 min of transrectal massage followed by electroejaculation; oxytocin (OXY) 10 min prior to 2 min of transrectal massage followed by electroejaculation. Transrectal massage consisted of general, back and forth motion over the ampullae, prostate and urethra with a flattened hand.

In experiment 2, bulls received saline (control), oxytocin, or cloprostenol 10 min before attempting semen collection by transrectal massage. Massage was applied specifically to the ampullae for a maximum of 5 min or until a semen sample was obtained. Electroejaculation was attempted in all bulls following transrectal massage.

In experiment 1, semen was obtained in <1% of bulls by transrectal massage. However, by using an improved massage technique in experiment 2, semen was obtained in 97.2% of attempts. Semen was obtained in 96.9 and 98.9% of attempts by electroejaculation in experiments 1 and 2, respectively.

Oxytocin treatment increased the time to penile protrusion during electroejaculation in experiment 1 and during massage in experiment 2. In experiment 1, oxytocin decreased the time to semen emission and tended to decrease the number of electroejaculation stimuli to semen emission. Cloprostenol treatment, in experiment 1, resulted in an increased number of electroejaculation stimuli to penile protrusion, but did not affect the number of stimuli required for semen emission.

Massage of the ampullae prior to electroejaculation reduced both the time to semen emission and the number of electroejaculation stimuli required for semen emission. Transrectal massage of the ampullae was very effective in this experiment for producing semen emission, but quantity of semen samples was less than for electroejaculation. The usefulness of transrectal massage for semen collection in breeding soundness evaluations needs to be investigated further under field conditions.     

Effects of environmental factors, age and genotype on sperm production and semen quality in Bos indicus and Bos taurus AI bulls in Brazil

The effects of ambient temperature and humidity, month, age and genotype on sperm production and semen quality in AI bulls in Brazil were evaluated. Data from two consecutive years were analyzed separately. Seven Bos indicus and 11 Bos taurus bulls from one artificial insemination (AI) center were evaluated in Year 1 and 24 B. indicus and 16 B. taurus bulls from three AI centers were evaluated in Year 2. Ambient temperature and humidity did not significantly affect sperm production and semen quality, probably because there was little variation in these variables. Month accounted for less than 2% of the variation in sperm production and semen quality. Increased bull age was associated with decreased sperm motility (P<0.10) and increased minor sperm defects (P<0.001) in Year 1. B. indicus bulls had greater (P<0.005) sperm concentration than B. taurus bulls in both years (1.7×10⁹/ml versus 1.2×10⁹/ml in Year 1 and 1.6×10⁹/ml versus 1.2×10⁹/ml in Year 2, respectively). Ejaculate volume was not significantly affected by genotype in Year 1 (6.6 ml versus 6.9 ml in B. indicus and B. taurus bulls, respectively), but B. indicus bulls had greater (P<0.05) total (11.4×10⁹ versus 8.2×10⁹) and viable (6.7×10⁹ versus 4.9×10⁹) numbers of spermatozoa in the ejaculate than B. taurus bulls. In Year 2, B. taurus bulls had greater (P<0.05) ejaculate volume than B. indicus bulls (8.2 ml versus 6.7 ml, respectively) and total and viable number of spermatozoa in the ejaculate were not significantly different between genotypes (10.3×10⁹ versus 9.1×10⁹ and 6.1×10⁹ versus 5.4×10⁹ in B. indicus and B. taurus bulls, respectively). Sperm motility was not significantly affected by genotype (mean, 59%). In Year 1, B. indicus bulls tended (P<0.10) to have more major sperm defects and had more (P<0.05) total sperm defects than B. taurus bulls (11.8% versus 8.7% and 13.6% versus 10.0%, respectively). In Year 2, B. indicus bulls tended (P<0.10) to have more total sperm defects than B. taurus bulls (16.2% versus 13.3%, respectively). In conclusion, neither ambient temperature and humidity nor month (season) significantly affected sperm production and semen quality. B. indicus bulls had significantly greater sperm concentration and B. taurus bulls had significantly fewer morphologically defective spermatozoa.     

Predicting end-of-test semen quality in bulls prior to performance testing

The first objective of this study was to determine if serum concentrations of specific hormones (testosterone, progesterone and androstenedione) in bulls at the start of performance testing could predict semen quality at the end-of-test when used in a multivariate model. The second objective was to evaluate other clinical measurements (breed, age, body weight, hip height and scrotal circumference) for predicting end-of-test semen quality. End-of-test semen quality was related to steroid concentrations and several pre-testing measurements, including age, body weight, hip height and scrotal circumference (SC). Combining the 3 steroid concentrations into a predictive test had a sensitivity of 0.6 and specificity of 0.5 at its most accurate point. The repeatability of the test result was extremely low (r(2) = 0.16; P < 0.05). In multivariate analyses, breed and start-of-test SC remained significant predictors of end-of-test semen quality (P < 0.05) while the other variables were nonsignificant (P > 0.1), suggesting that start-of-test SC was the most accurate predictor of end-of-test semen quality. Removing bulls at the start-of-test that had scrotal measurements of less than 20 cm, 24 cm, 28 cm or 32 cm resulted in sensitivities and specificities of 0.19, 0.94; 0.41, 0.81; 0.64, 0.56; and 0.94, 0.12, respectively. No cut-point had both adequate sensitivity and specificity. Because clinical tests were correlated, combining the tests to improve accuracy was not justified.     

Postnatal development of the tubular lamina propria and the intertubular tissue in the bovine testis

Summary The postnatal development of intertubular cells and vessels and of the tubular lamina propria was studied in three locations of perfusion-fixed bovine testes from 31 animals ranging from 4 to 78 weeks. The postnatal morphological differentiation of the testis is not uniform, regional differences have to be considered. The intertubular cell population is composed of mesenchyme-like cells, fibrocytes, Leydig cells, peritubular cells and mononuclear cells. In 4 and 8-week-old testes mesenchyme-like cells are the dominating element. These pluripotent cells proliferate by frequent mitoses and are the precursors of Leydig cells, contractile peritubular cells and fibrocytes. Morphologically differentiated Leydig cells are encountered throughout the entire period of postnatal development. In 4-week-old testes degenerating fetal and newly formed postnatal Leydig cells are seen in juxtaposition to each other. From the 8th week on, only postnatal Leydig cells are present. Between 16 and 30 weeks large-scale degeneration of prepuberal Leydig cells is observed. The Leydig cells that survive this degenerative phase constitute the long-lasting adult population. 20–30% (numerically) of all intertubular cells at all ages are free mononuclear cells. These are found as lymphocytes, plasma cells, monocytes, macrophages and light intercalated cells (LIC). The latter are monocyte-derived, Leydig cell-associated typical cells of the bovine testis. The differentiation of the two main components of the tubular lamina propria, (i) basal lamina and (ii) peritubular cell sheath, seems to be effected rather independent from each other and also from hormonal signals important for the development of the germinal cells. The laminated basal lamina reaches nearly 3 m at 16 weeks and is later on continuously reduced. At 25 weeks the peritubular cells have transformed into contractile myofibroblasts. At this period the germinal epithelium is still in a prepuberal state.To Dr. E. Schilling, Mariensee, on the occasion of his 65^th birthday     

Testicular development and its relationship to semen production in Murrah buffalo bulls

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 significant 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 x 10(9). Corresponding values for sperm output per week per gram of testis were 59.1, 45.8, 41.1, 36.2 x 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.     

Butylated hydroxytoluene inclusion in semen extender improves the post-thawed semen quality of Nili-Ravi buffalo (Bubalus bubalis)

The study was carried out to evaluate the potential impact of butylated hydroxytoluene (BHT) on the frozen-thawed semen quality of Nili-Ravi buffalo bulls. Ejaculated bull semen was extended in a Tris-citrate egg yolk extender containing various concentrations of BHT (0.5, 1.0, 2.0 and 3.0 mM). Semen was frozen at −196 °C using 50 × 10⁶ spermatozoa per 0.5 mL straws. Five straws from each treatment were thawed to assess the semen quality in terms of sperm motility, viability, plasma membrane integrity and acrosomal integrity. Post-thawed sperm motility was determined using a phase-contrast microscope. Viability, plasma membrane integrity and acrosomal integrity were evaluated by the supravital staining, hypo-osmotic swelling test and normal acrosomal reaction, respectively. The highest (P < 0.05) motility, acrosomal integrity and hypo-osmotic swelling response of spermatozoa was achieved by addition of 1.0 and 2.0 mM BHT to semen extender. However, highest (P < 0.05) viability of spermatozoa was achieved by inclusion of 2.0 mM BHT. The higher concentration of BHT (3.0 mM) reduced the motility, acrosomal integrity, viability and hypo-osmotic swelling response of the spermatozoa compared to other concentration used. In conclusion, BHT when added in the semen extender can improve the semen quality of buffalo bulls.     

The effect of nocturnal sampling on semen quality and the efficiency of collection in bovine species

This study evaluated night and day semen collection regimes in Holstein and Brahman bulls (four bulls of each breed) that were collected weekly, each during a morning and a night collection. Ejaculates (n=64) were obtained via artificial vagina over 4 weeks. The first collection of each week alternated between night and day. Two collection teams were employed. Bull behavior parameters included reaction time to first mount, time to ejaculation, a refractory period test, and a thrust intensity test. The numbers of interruptions were counted as a managerial parameter. Pre-freeze semen parameters included total volume, initial motility and concentration. Post-freeze semen parameters measured were: 0- and 3-h post-thaw motility; percent intact acrosomes; and percent sperm abnormalities. Data were analyzed by least squares methods. The bull within breed effect differed (P<0.05) for behavior parameters. The bull within breed effect for total motile sperm harvested was not significant. The bull within breed response was mixed for post-freeze semen viability parameters. Bull within breed was not significant for sperm abnormalities. The night versus day treatment was significant for the managerial parameter (P=0.002). Although a different collection schedule for Bos indicus cattle was not warranted, the efficiency of the collection process was affected by extraneous environmental conditions.     

Genome-wide detection of non-additive quantitative trait loci for semen production traits in beef and dairy bulls

Semen production traits are important aspects of bull fertility, because semen quantity leads to direct profits for artificial insemination centres, and semen quality is associated with the probability of achieving a pregnancy. Most genome-wide association studies (GWASs) for semen production traits have assumed that each quantitative trait locus (QTL) has an additive effect. However, GWASs that account for non-additive effects are also important in fitness traits, such as bull fertility. Here, we performed a GWAS using models that accounted for additive and non-additive effects to evaluate the importance of non-additive effects on five semen production traits in beef and dairy bulls. A total of 65 463 records for 615 Japanese Black bulls (JB) and 50 734 records for 873 Holstein bulls (HOL), which were previously genotyped using the Illumina BovineSNP50 BeadChip, were used to estimate genetic parameters and perform GWAS. The heritability estimates were low (ranged from 0.11 to 0.23), and the repeatability estimates were low to moderate (ranged from 0.28 to 0.45) in both breeds. The estimated repeatability was approximately twice as high as the estimated heritability for all traits. In this study, only one significant region with an additive effect was detected in each breed, but multiple significant regions with non-additive effects were detected for each breed. In particular, the region at approximately 64 Mbp on Bos taurus autosome 17 had the highest significant non-additive effect on four semen production traits in HOL. The rs41843851 single nucleotide polymorphism (SNP) in the region had a much lower P-value for the non-additive effect (P-value = 1.1 × 10^?31) than for the additive effect (P-value = 1.1 × 10^?8) in sperm motility. The AA and AB genotypes on the SNP had a higher phenotype than the BB genotype in HOL, and there was no bull with the BB genotype in JB. Our results showed that non-additive QTLs affect semen production traits, and a novel QTL accounting for non-additive effects could be detected by GWAS. This study provides new insights into non-additive QTLs that affect fitness traits, such as semen production traits in beef and dairy bulls.     

Hematologic and semen quality changes in bulls with experimental eperythrozoon infection

Eperythrozoon organisms were isolated from the blood of a young beef bull with scrotal and hindlimb edema. Young beef bulls, managed under conditions closely mimicking those used in organized bull testing programs, were experimentally administered eperythrozoon organisms. Scant to few organisms were identified on blood smears from bulls (5 of 6) for 2 to 4 days starting 12 days after administration. After a second challenge with intravenously administered viable eperythrozoon organisms, the bulls demonstrated immunity by either failing to become parasitemic (4 of 6) or rapidly clearing the organisms from the blood (2 of 6). No bull became anemic, icteric, or hypoglycemic. Increased serum lactate and decreased blood bicarbonate concentrations probably reflected increased glycolytic activity of infected erythrocytes. A cause for azotemia observed late in the study was not determined. The bulls did not develop scrotal or hindlimb edema. Scrotal circumference and texture remained constant throughout the study. Semen quality was minimally altered while the bulls had organisms identified on blood smears. Harsh lung sounds were asculted in bulls during and immediately after organisms were present in the blood. Although the bulls reliably had organisms in the blood, none showed anemia, scrotal or hindlimb edema, or decreased semen quality; therefore, an additional factor or factors, or greater parasite load may be required for the expression of disease.     

Effects of ultrasonography on the bovine testis and semen quality

Ten yearling beef bulls were assigned to control (n = 5) or ultrasound treatment (n = 5) groups. Treatment consisted of a single 3-min exposure per testis to ultrasonic radiation at a frequency of 5 MHz and at low acoustical intensity (spatial peak temporal averages at 10 and 18 mm, focal points of 0.14 and 0.59 mW/cm(2) and spatial peak pulse averages of 1.1 and 3.4 W/cm(2) at corresponding focal points). Ultrasonic treatment had no effect (P > 0.05) on the percentage of progressively motile spermatozoa, primary sperm defects, secondary sperm defects or normal acrosomes over a 10-wk posttreatment evaluation period. Similarly, scrotal circumference, testicular consistency, paired testes weight, paired epididymal weight, daily sperm production per gram of testicular parenchuma, and epididymal sperm reserves were not affected (P > 0.05) at 69 d following ultrasound treatment. Ultrasonography of bovine scrotal contents did not affect reproductive capacity over the interval studied.     

Effects of age and environmental factors on semen production and semen quality of Austrian Simmental bulls

More than 90% of the breeding stock of Austrian dual purpose Simmental cows is artificially inseminated. Knowledge of factors affecting sperm production and semen quality is of importance with regard to reproductive efficiency and thus genetic improvement as well as for the productivity and profitability of AI centers. Hence, semen data from two Austrian AI centres collected in the years 2000 and 2001 were evaluated. In total, 3625 and 3654 ejaculates from 147 and 127 AI bulls, respectively, were analysed regarding ejaculate volume, sperm concentration, percentage of viable spermatozoa in the ejaculate, total spermatozoa per ejaculate and motility. Effects accounted for were the bull (random), age of bull, collection interval, number of collection on collection day, bull handler, semen collector, temperature on day of semen collection, in the course of epididymal maturation (average temperature of days 1-11 before collection) and during spermatogenesis (average temperature of days 12-65 before collection). Age of bull significantly affected all traits (P<0.01 to P<0.001) except motility score in center 2. Ejaculate volume and total number of spermatozoa increased with age of bull while sperm concentration was lower in higher age classes (center 1). The collection team was also found to significantly influence semen quality traits. With increasing collection interval ejaculate volume and total number of spermatozoa increased significantly (P<0.05 to P<0.001) while collection intervals between 4-9 days and 1-6 days were superior with regard to sperm concentration and percentage of viable spermatozoa, respectively (P<0.10 to P<0.001). First ejaculates were superior with respect to ejaculate volumes, sperm concentrations and total number of spermatozoa per ejaculate (P<0.001). Temperature, either on day of semen collection or during epididymal maturation or spermatogenesis, had important but inconsistent effects on semen production and sperm quality. Overall, however, ambient temperatures in the range of 5-15 degrees C were found to be optimal for semen production.     

B-Mode ultrasonographic evaluation of the testis in relation to serum testosterone concentration in male Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) during the breeding season

The use of ultrasonography as a noninvasive tool for assessing the reproductive status of the male Yangtze finless porpoise (YFP; Neophocaena phocaenoides asiaeorientalis) was validated by correlating ultrasonographically determined testicular volume (TV) and testicular parenchyma pixel intensity (PI) with serum testosterone (T) concentration. The testes of 13 free-ranging male YFPs from the Tian-e-Zhou Reserve and three captive animals from the Baiji Dolphinarium (Wuhan, China) were examined ultrasonographically during April 2008. Testis volume was determined using Lambert's formula for an ellipsoid. Testicular parenchyma PI was evaluated by analyzing testicular ultrasonograms using pixel analysis software (Image J). Serum T concentrations were determined using a single-antibody radioimmunoassay. The TV, PI, and serum T concentration were low and similar in animals with body length <133 cm, highest in those with body length ≥142 cm, and highly variable in those with body length from 133 to 141 cm. Both TV and PI were closely correlated with serum T concentration (r = 0.91 and r = 0.85, respectively; P < 0.01), indicating a consistent association between structural and functional development of the testis. In conclusion, we inferred that puberty onset in male YFPs occurred when TV was >150 cm³ and PI was >60 during the breeding season and that testicular ultrasonography and pixel analysis was an efficient, noninvasive, real-time tool to evaluate testicular function of live male YFPs.     

Effect of precocious collection on semen output and quality in young Holstein bulls

Semen production units compete heavily with each other, so they tend to select and collect bulls at the earliest possible age, even before puberty, in order to reduce the interval between generations. This study is a retrospective analysis of the effect of precocious collection on semen quality in Holstein bulls. The semen parameters of early- and late-maturing bulls collected before and after 410 days of age, respectively, were compared over two periods, 1991-1995 and 1997-1999. These periods were defined in relation to the collection rhythms (three collections of two ejaculates at 15 days interval before 1996 and adaptation of the collection rhythms to individual physiological capacity after 1996) and the collection conditions. The effects of age, precocious collection and the interaction between age and precocious collection on mean semen parameters (volume of the ejaculate, sperm motility, percent of motile spermatozoa per ejaculate, total sperm concentration and mobile sperm concentration) measured on collections 1-6 (n = 358 for 1991-1995 and n = 121 for 1997-1999), 7-12 (n = 255 for 1991-1995 and n = 80 for 1997-1999) and 13-18 (n = 92 for 1991-1995 and n = 36 for 1997-1999) were studied by covariance analysis. The semen quality of bulls collected at the early age differed from that of bulls collected after 410 days of age for the first period when the collection rhythm was intense. No effect of precocious collection was evidenced for the second period, suggesting the importance of individual adaptation of the collection rhythm to sexual maturation in young bulls. Early collections at a semen production unit reduced the time needed to obtain the number of insemination straws required for the progeny-testing program by 40 days. Early sperm collection is, thus, of economic and technical interest in well managed semen production units.