The proportion of beef bulls in western Canada with mature spermiograms at 11 to 15 months of age

A study was conducted to determine the proportion of yearling beef bulls that have mature spermiograms at 11 to 15 months of age, and to evaluate the relationship between semen quality traits, age, and scrotal circumference. Semen samples and data on sperm motility and scrotal circumference measurements were obtained from 1641 bulls of 14 breeds. Criteria for a satisfactory spermiogram included sperm concentration > or = 400 x 10(6)/mL, > or = 60% progressively motile sperm, and > or = 70% morphologically normal sperm. The mean scrotal circumference measurements for all bulls combined were 33.4, 34.4, 35.2, 35.8, and 35.3 cm at 11, 12, 13, 14, and 15 months of age, respectively. The percentage of bulls with matures spermiograms at 11, 12, 13, 14, and 15 months of age were 20%, 30%, 51%, 52%, and 61%, respectively. There was a high positive correlation (r = 0.9) between the number of bulls with > or = 70% normal sperm and scrotal circumference measurement. The main types of morphologic defects observed in immature bulls were proximal droplets and midpiece defects.     

Effect of Semen Collection Methods on the Quality of Pre‐ and Post‐thawed Bali Cattle (Bos javanicus) Spermatozoa

This study was conducted to evaluate the response of Bali bulls (Bos javanicus) to different semen collection methods and their effects on fresh and post‐thawed semen quality. The collection methods employed were electro‐ejaculation (EE), transrectal massage (RM) and RM followed by EE (RM + EE). A total of 25 untrained Bali bulls (age between 2 and 4 years old) were subjected to the different semen collection methods. Fresh semen samples from all the 25 bulls were evaluated for volume, pH, general motility, live/dead ratio and abnormality using the conventional method. For fresh and frozen samples collected by EE and RM from 10 bulls, computer‐assisted semen analysis system was used for precise quantitative measurement of motility, velocity and forward progression. Accucell photometer was used to measure sperm concentration in all samples, regardless fresh and frozen. Semen samples were obtained 100% of the attempts using EE, 84% using RM and 96% using RM + EE. There were no differences among the collection methods for fresh semen quality characteristics, including motility, morphology and viability, but pH and volume were higher for EE than RM and RM + EE. Higher sperm concentration was observed in semen collected by RM than the other two methods. Different age groups (2–3 and >3–4 years old) of the bulls did not show significant differences in volume, pH, sperm concentration, percentages in motility, live/dead ratio and normal sperm morphology. The quality of semen for general and progressive motility, VAP, VSL and VCL and acrosomal integrity after thawing was higher for RM than EE. In conclusion, Bali bulls appeared to respond best to EE and the combination of RM + EE than RM, as a method of semen collection, with a shorter time of stimulation required. Differences in age of the Bali bulls did not affect the semen quality.     

Reproductive criteria of beef bulls during and after exposure to increased ambient temperature

Sixteen yearling Angus bulls were randomly assigned to one of two temperature-controlled chambers to determine the effects of elevated ambient temperature on body functions and semen characteristics. After 8 wk adjustment at 23 C, eight heat-stressed bulls were exposed to 35 +/- 1 C for 8 h and 31 +/- 1 C for 16 h during each 24-h period, and eight control bulls were maintained at 23 +/- 1 C for 8 wk. Then all bulls were exposed to 23 C for 8 wk. Bulls were fed so that both control and stressed bulls gained at similar rates (.58 kg/d). Semen was collected with an artificial vagina twice weekly before, during and after heat stress. During treatment, the respiratory rate of stressed bulls was greater (P less than .001) than that of control bulls (54.2 +/- 1.5, 29.9 +/- 1.5 breaths/min, respectively). Rectal temperatures were increased (P less than .01) from 38.2 +/- .1 to 38.7 +/- .1 C and water consumption was increased by 35% in stressed bulls when compared with controls. Semen volume was not altered by treatment, but percentage of motile sperm decreased (P less than .01) in stressed bulls by 2 wk after the start of heat treatment. Sperm motility of stressed bulls returned to normal values 8 wk after the end of heat treatment. Similarly, the percentage of aged acrosomes on sperm from stressed bulls increased (P less than .01) by the second week of treatment and remained greater than that of controls throughout the stress period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Numbers of Sertoli cells, quantitative rates of sperm production, and the efficiency of spermatogenesis in relation to the daily sperm output and seminal quality of young beef bulls

Data from 34 yearling Hereford or Angus bulls were used to investigate relationships of testicular size, quantitative rates of sperm production, Sertoli cell numbers, numbers of germ cells supported per Sertoli cell, and the efficiency of spermatogenesis to daily sperm output and seminal quality. Two ejaculates were collected by electroejaculation from each bull on each of 2 days/week throughout the study. The percentage of progressively motile sperm and the percentage of morphologically normal sperm were determined from aliquots of fresh semen. Additional aliquots of semen were frozen in glass ampules or plastic straws and subsequently evaluated for postthaw motility and percentage of sperm with intact acrosomes. Sertoli cell numbers, the numbers of germ-cells per Sertoli cell, and the efficiency of spermatogenesis were unrelated to the quality of fresh or frozen semen (P greater than 0.05). In first ejaculates, the numbers of sperm and motile sperm were related (P less than 0.05) to testicular parenchymal weight (r = 0.38 and 0.50), daily sperm production (r = 0.45 and 0.53), and spermatids per gram of testicular parenchyma (r = 0.35 and 0.34). Testicular parenchymal weight and daily sperm production also were related to daily sperm output and to the average daily motile sperm output of these bulls (P less than 0.05), but could account for less than 25% of the variability in these end points among bulls.     

Methods of collection,extender type,and freezability of semen collected from creole bulls raised in the tropical highlands of Ecuador

This study was conducted to determine the best combination between two collection method and two extenders in the cryopreservation of semen from creole bulls adapted to highlands of the Ecuadorian Andes. Sixty ejaculates from three adult Creole bulls were evaluated after collection by artificial vagina (AV) and electroejaculation (EE). Semen samples were split into two aliquots and diluted with a soy lecithin extender (Andromed®; A) or an egg yolk-containing extender (Triladyl®; T) and packed in straws of 0.25 ml with 20 × 10⁶ sperms. Optical microscopy and computer-assisted semen analysis system (CASA) were used to evaluate semen quality characteristics. The effects of collection methods and extender type as well as its interaction were evaluated by a factorial ANOVA and Bonferroni’s test. Semen samples collected with EE and frozen with T (EE-T) and A (EE-A) had greater proportion of spermatozoa with optical assessed individual progressive motility (IPM), plasmatic membrane intact (HosT), and lower tail abnormalities than those obtained with AV and frozen with the same extenders (AV-T and AV-A); however, differences were significant only between EE-A and AV-T. CASA assessment indicated that the total mobility (TM) was greater (P < 0.05) in semen samples diluted with T, although these samples had a greater proportion (P < 0.05) of sperms with local motility (LM) and fewer immobile sperms (IS), than those extended with A. Generally, semen samples obtained with EE or AV and diluted with T seems to be the best option to ciopreserve gametes of Creole bulls raised in highlands of Ecuadorian Andes.

     

The Proportion of Beef Bulls in Sweden with Mature Spermiograms at 11–13 months of Age

Semen samples collected postmortem from 142 yearling beef bulls (11-13 months old) of three different breeds (Charolais, Hereford and Simmental) were examined to evaluate the proportion of bulls with mature spermiograms. Before slaughter, testes and epididymides were clinically examined and scrotal circumferences were measured. Aliquots of the cauda epididymal contents taken postmortem were used for sperm morphology examination. Sperm head morphology was studied in dry smears stained with carbol-fuchsine. For each preparation, 500 spermatozoa were counted in each smear under light microscope (x 1000). The presence of proximal cytoplasmic droplets, abnormal acrosomes, detached heads and abnormalities of the midpiece and tail were recorded in wet preparations of formol-saline-fixed spermatozoa. For each preparation, 200 spermatozoa were counted in each preparation under a phase-contrast microscope (x 1000). The abnormalities were classified according to a classification system developed by Bane (1961). Morphological abnormalities were recorded as a percentage of the total number of counted spermatozoa. Criteria for a spermiogram to be considered mature included <15% abnormal heads and <15% proximal droplets. According to this definition approximately 48% (68 of 142) of the examined bulls were considered mature. The bulls in this study represent approximately one-fifth of the total amount of performance-tested beef bulls in Sweden during 5 years. Our results indicate that only less than half of the Swedish yearling beef bulls at the testing station appear to have a mature spermiogram at the time they are offered for breeding purposes.     

Cryopreservation of the semen collected by electroejaculation from the Hokkaido brown bear (Ursus arctos yesoensis)

Four adult Hokkaido brown bears were used as semen donors, and semen characteristics were examined before freezing and after thawing. A total of 10 electroejaculates were diluted with Tris-egg yolk extender and cooled to 4 degrees C over 90 min. Spermatozoa were equilibrated with 4.7% glycerol for 80 min. Semen packed in 0.25 ml plastic straws were frozen with liquid nitrogen vapor. Percentages (mean +/- SD) of motile and live sperm were 96+/-2 and 86.5+/-7.2% before freezing, and 43+/-5 and 67.4+/-3.9% after thawing, respectively. Although the number of progressively motile sperm after thawing varied among samples (1.8+/-1.2 x 10(8) cells/ejaculate), frozen semen in the present study might serve for artificial insemination.     

Libido, hormone concentrations in blood plasma and semen characteristics in Holstein bulls

Relationships among bull libido, serum hormone concentrations and semen characteristics were studied using 18 Holstein bulls that were 4 to 5 yr old. The hormones studied included testosterone, estradiol (E2), prolactin (PRL), LH and cortisol. Two ejaculates were collected three times per week from each bull during a 5-wk trial. During the last week of the trial, on a day semen was not collected, blood was collected from indwelling catheters every 15 min for 6 h to determine the hormonal profiles of each bull. On the following day, blood was sampled every 10 min before and after the time of semen collection. Libido factors were quantified, and semen volumes and sperm concentrations were recorded. The libido factors included reaction time to first service, latency time between the first and second semen collections, and duration of time the bull mounted the teaser prior to the first (TM1) and second (TM2) semen collection. Average reaction and latency times were correlated (r = .524; P = .026), as were TM1 and TM2 (r = .597; P = .015). Latency times were correlated with average TM2 (r = .669; P = .003). Average PRL concentrations were correlated with average latency times (r = .467; P = .05). Low libido bulls tended to have higher E2:testosterone ratios than did high libido bulls. Both PRL and cortisol concentrations increased at semen collection.     

Technical note: Artificial vagina vs a vaginal collection vial for collecting semen from rams.

The time required to train rams to an artificial vagina (AV) makes collecting semen from large numbers of rams difficult. To manage this problem, we developed a glass, round-bottomed, 1.9-cm i.d. x 9.8-cm long vaginal collection vial (VCV). Three experiments were conducted to determine whether the VCV affected 1) semen volume per collection, 2) percentage of motile spermatozoa, 3) forward progressive motility score before and after extension and after freezing and thawing, and 4) our ability to collect semen from untrained rams. A soft rubber cap with a hole in the center was used to cover the VCV. A VCV was inserted into the vagina of an estrual ewe, and a monofilament line attached to the VCV was clipped to the wool near the vulva. Rams were joined with unrestrained ewes in a pen until they ejaculated into the VCV. In Exp. 1, five rams trained to an AV were used in a switchback design with four collection periods. During each period (1 d), semen was collected with an AV and a VCV. Immediately after collection, semen volume and sperm motility were quantified. Semen was extended with an aloe vera gel-based diluent at a 1:4 dilution rate, motility was quantified again, and semen was frozen. At 1 h after freezing, semen was thawed and sperm motility was quantified. Ejaculate volume (mean = 0.7 mL) and all measures of motility after collection were similar (P > 0.05) for the two collection methods. In Exp. 2, 10 rams trained to an AV were used in a switchback design with five collection periods (period = 3 d). On d 1 and 3 of each period, an AV and a VCV were used to collect semen. Collection method did not affect (P > 0.05) ejaculate volume (mean = 1.0 mL), percentage of motile cells, or forward progressive motility score. In Exp. 3, 51 untrained rams were used in a switchback design with a single collection period (2 d). Semen was collected with an AV and a VCV. Ability to collect an ejaculate and time required for collection were recorded. The likelihood of collecting semen from untrained rams was greater (P < 0.01) using a VCV (mean = 31.4%) than using an AV (mean = 9.8%). Collection method did not affect (P > 0.05) ejaculate volume (mean = 0.8 mL), percentage of motile cells, or forward progressive motility score. We concluded that a VCV could be used to collect semen from rams that are not trained for semen collection without decreasing ejaculate volume or sperm motility.     

Effect of energy intake after weaning on the sexual development of beef bulls. I. Semen characteristics and serving capacity

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effects of energy intake after weaning, degree of fatness, and short-term weight change on reproductive characteristics of yearling beef bulls. For 200 d (ending in May), 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Bulls then were adjusted to a roughage diet for 10 d before grazing brome pasture for 38 d (ending in June). Energy level did not affect motility or sperm morphology of semen collected with an artificial vagina in May and June. High energy levels were not detrimental to bull performance during a 30-min serving-capacity test in May or June. Backfat thickness was not related to semen characteristics or serving capacity. Amount of weight lost from May to June did not affect the semen quality or serving capacity of Herefords. Those Simmental bulls that had a more positive weight change from May to June had a more favorable change in semen quality from May to June (P less than .05) due to lower semen quality in May (P less than .05). The high level of energy was not detrimental to semen characteristics or serving capacity. Some of the Simmental bulls may have been underfed for maximum semen quality at the beginning of the pasture period. Within the normal range of energy fed to beef bulls from weaning to the beginning of the breeding season as yearlings, it may be more likely to underfeed breeds of large mature size than to overfeed British breeds.     

Morphological features of spermatozoa of swamp buffalo AI bulls in Thailand

The appearance and incidence of sperm abnormalities was studied in 115 ejaculates, collected periodically over 1 year covering all seasons from five mature, healthy swamp buffalo (Bubalus bubalis) bulls reared under tropical conditions and serving as the current source of semen for artificial insemination (AI) in Thailand. Light microscopy of stained smears was used to investigate sperm head shape morphology, while unstained wet smears were used to examine other sperm abnormalities. The most commonly found morphological aberrations were pear-shaped spermatozoa, knobbed acrosomes, proximal cytoplasmic droplets, simple bent tails and coiled tails under the head, whose ultrastructure (scanning electron microscopy) corresponded to what has been found in other species of bovidae, including varieties of buffalo. The mean prevalence (as least squares mean +/- SEM) of sperm abnormalities was low (below 15%), corresponding to healthy spermiograms. The younger bulls (<10 years old, n = 3) had less abnormalities than the older ones (10.1 +/- 0.6% versus 14.1 +/- 0.8%, P < 0.001, n = 2), including abnormalities of sperm head shape (1.1 +/- 0.3% versus 3.6 +/- 0.3, P < 0.001), acrosome defects with knobbed acrosomes (1.1 +/- 0.2% versus 1.2 +/- 0.3%, P < 0.001), spermatozoa with proximal cytoplasmic droplets (2.7 +/- 0.1% versus 1.4 +/- 0.2%, P < 0.001), defective mid-pieces (0.2 +/- 0.1% versus 0.3 +/- 0.1%) and abnormal sperm tails (3.1 +/- 0.3% versus 5.7 +/- 0.4%, P < 0.001). The within-bull effect of the year solely affected the incidence of pear-shaped spermatozoa while the incidences of abnormal contour, variable size of sperm head shapes, abnormal mid-piece and simple bent tail among bulls were affected by ejaculate (week of collection). Interaction between age and ejaculate affected only the prevalence of spermatozoa with proximal cytoplasmic droplets. In conclusion, the types of defects encountered were similar to those found in other bovidae, with a very low prevalence over the year the AI sires were followed through.     

Effect of method of seminal collection on the retrograde flow of spermatozoa into the urinary bladder of rams

The effects of method of seminal collection and a diuretic on retrograde flow of spermatozoa into the urinary bladder of rams were examined. In experiment 1, semen and urine were collected from 8 rams during the non-breeding season. Prior to seminal collection, all rams were given furosemide and a sample of urine was obtained during micturition. Semen was then collected from each ram with an artificial vagina or by electroejaculation in alternate weeks for 4 weeks, and the urine released during the first postseminal collection micturition was collected in 4 consecutive samples. The volume of electroejaculates was larger (P less than 0.0001) than the volume of ejaculates, but the total number of spermatozoa in the electroejaculate or in the ejaculate were not different (P greater than 0.1). Urine obtained before seminal collection was azoospermic or contained few, nonmotile spermatozoa (mean +/- SD = 0.053 +/- 0.114 x 10(6)/ml). The adjusted spermatozoal concentration (mean +/- SD = 1.630 +/- 2.258 x 10(6)/ml) in the urine collected after seminal collection was 31 times higher (P less than 0.0001) and there were motile spermatozoa in most (97%) of the samples. The spermatozoal concentration in sequential samples of urine was not different (P greater than 0.1) between samples and was not affected (P greater than 0.1) by the method of seminal collection. There was a trend, approaching significance (P = 0.052), for an effect of method of seminal collection on the percentage of retrograde flow.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Relationship between Semen Quality and the Nonreturn Rate of Bulls

Contents
The value of routine evaluation of bull semen was analysed for 117 AI bulls placed in two studs. Data from semen analysis of a total of 1635 ejaculates was compared statistically with the nonreturn rates of the bulls. The semen parameters which were significantly correlated to nonreturn rates were the motility of the freshly collected ejaculates (p = 0.0140) and post-thaw motility (p = 0.0075). The total number of motile sperm in the inseminate ranged from 10.9 to 19.3 × 10⁶ and according to previous reports the effects of low motility should be fully 'compensated' when doses above 10 × 10⁶ sperm/dose are used for insemination. In conclusion, the motility of freshly collected semen does not appear to be 'compensation' and a low percentage of motile sperm in an ejaculate may indicate other dysfunctions of the population of motile cells. Furthermore, post-thaw motility appears to correlate significantly with nonreturn rates. The largest proportion of the variation was explained by the breed of the bull and stud (42.2% of the variation), whereas the two motility parameters explained 10% of the total variation in nonreturn rates. Objective and precise evaluation of sperm motility in combination with other semen traits are needed to improve breeding efficiency. Although microscopic evaluation of sperm motility correlates with nonreturn rates of bulls, the methods are subjectively assessed and inaccurate and therefore do not allow a satisfactory prediction of fertility.     

Crossbred bull selection for bigger scrotum and shorter age at puberty with potentials for better quality semen.

Shortening age at puberty of crossbred breeding bull is an important issue in the tropics. This study aimed at selecting crossbred bulls at earliest possible age with bigger scrotum and potential for donating quality semen. One hundred and 31 pre-joining crossbred bulls of Central Artificial Insemination Laboratory, Saver, Dhaka were examined. The bulls being trained by seeing semen collection from mature bulls were allowed ejaculation into the artificial vagina at homosexual mount during a 20 min time at three occasions, every three months. Eighty one of 131 bulls produced at least one ejaculate during the study and their mean +/- SD age and scrotal circumference (SC) were 20.3 +/- 4.7 months and 28.2 +/-2.7 cm, respectively. Bulls' body weight, body condition score (BCS) and SC influenced the attainment of their puberty (p < 0.05). Bull's body weight had positive effects on scrotal circumference and ejaculate volume (p < 0.05). Scrotal circumference positively influenced the percentages of normal spermatozoa (p < 0.05). Scrotal skin-fold thickness negatively influenced the proportion of spermatozoa with normal head (p < 0.05). Based on age at first ejaculate and SC, 29.6% bulls (n = 24) were selected by cluster analysis. Selected bulls had mean +/- SD age 17.9 +/- 2.2 months, body weight 287.3 +/-48.6 kg, SC 30.5 +/- 1.5 cm, ejaculate volume 3.4 +/- 1.3 ml, sperm motility 50.8 +/- 17.2%, total spermatozoa per ejaculate 2541.9 +/- 1699.2 million and normal spermatozoa 81.5 +/-14.5%. The selected pubertal bull group was different from the unselected pubertal bulls at MANOVA (p < 0.0001). About 30% of pubertal crossbred bulls can be selected with shorter age and larger scrotum at puberty under conditions prevailed in Bangladesh.     

The effect of collection method and housing system on semen production and fertility of Alabio drakes

Three methods of semen collection from Alabio drakes were compared: the use of an artificial vagina (AV), electro ejaculation (EE) and manual massage (MM). For the latter two methods, drakes were housed in individual cages or in groups in floor pens, while for the AV method all drakes were kept in individual cages. Training success rates of drakes for the three collection methods were similar. Drakes housed in cages produced significantly more semen with a higher sperm concentration, which maintained fertility longer than semen from floor-penned drakes. The average semen volume per ejaculate, sperm concentration and total number of sperm per ejaculate were highest for the AV method while the other two methods did not differ. The average duration of fertility was significantly longer for the AV method (8.8 d) than the EE (6.5 d) or MM methods (5.1 d). The proportion of fertile eggs for 7 d following the insemination of 2 X 10(8) spermatozoa was also highest for the AV method. Although greater skill was required from the operator, the AV method is recommended for general use because of its significantly higher semen yield and longer duration of fertility.     

不同季节和气候条件对种公牛精液品质的影响的研究

[目的]研究不同季节气候条件对种公牛精液品质的影响。[方法]从采精种公牛中随机抽出5头,选取气温最高（7月份）最低（1月份）和适中温度（4,9月份）进行试验,分别对不同时期所采得的精液进行检测。[结果]在最高温度月份7月份（25℃）时5头种公牛的平均精液量为5.88mL,原精活率67.2%,精液密度16.64亿/mL,冻后活率33.8%,生产冻精数143.4剂,精子畸形率23%。1月份环境温度平均在-11.2℃时,5头种公牛的精液量平均为5.7mL,原精活率66.8%,精液密度13.3亿/mL,冻后活率37.4%,生产冻精数为275.8剂,精子畸形率17.8%。在4,9月份环境温度12℃时精液量为6.6mL,原精活率73.2%,精液密度16.92亿/mL,冻后活率41.8%,生产冻精数404.4剂,精子畸形率12.6%。精液量之间差异显著（P〈0.05）,原精活率之间差异显著（P〈0.05）,精子畸形率之间差异显著（P〈0.05）。冻后活率和冻精生产数差异不显著。[结论]环境温度过高或者过低都会影响精液品质,种公牛在适宜的温度下生产的精液品质也会更加优良,种公牛在温度较高的条件下生产精液品质比在低温条件下还要差,种公牛最适宜的生产温度为12℃～16℃。     

Semen collection in rhinoceroses (Rhinoceros unicornis, Diceros bicornis, Ceratotherium simum) by electroejaculation with a uniquely designed probe.

Electroejaculation in rhinoceroses has historically yielded inconsistent results, with the collection of high-quality, sperm-rich samples rare. The goal of this study was to develop a reliable method of electroejaculation in the rhinoceros by designing a rectal probe that appropriately fits the anatomy of this taxon and refining the procedure. A curved probe handle ending in an oblate, ellipsoid head was built using readily available supplies. A combination of rectal massage, penile massage, and electrical stimulation with a specially designed probe was employed in attempts to collect semen on 14 occasions from greater one-horned rhinoceroses (Rhinoceros unicornis; n = 4), black rhinoceroses (Diceros bicornis; n = 2) and a southern white rhinoceros (Ceratotherium simum; n = 1). During 13 of the 14 attempts, ejaculates were collected in multiple fractions. All but one of the ejaculates contained spermatozoa, and seven ejaculates contained good-quality fractions of semen (-60% sperm motility; > or =20 x 106 spermatozoa/ml) suitable for sperm banking and assisted reproduction procedures. Mean (+/-SEM) values for volume, pH, osmolality, and total sperm number for ejaculates containing good-quality fractions (98.2 +/-21.8 ml, 8.5+/-0.1, 290.4+/-6.7 mOsm, and 37.1+/-12.0 x 10(9), respectively) did not differ (P > 0.05) from those containing only poor-quality samples. Urine and/or erythrocyte contamination was not uncommon in fractions of both ejaculate types. Males producing good-quality samples ranged in age from 7 to 34 yr. None of the samples contained > or =75% morphologically normal spermatozoa. Electroejaculation with a uniquely designed probe consistently produced ejaculates in the rhinoceros. However, the production of high-quality samples continued to be challenging, occurring in only 50% of collection attempts. Regardless, the technology has progressed to a stage at which good-quality semen samples can be produced for sperm banking and assisted reproduction, and thereby can be integrated into intensive rhinoceros management strategies for the ultimate survival of this taxon.     

Case Study: Relationships of Scrotal Circumference and Scrotal Volume to Growth and Semen Traits in Beef Bulls

Breeding soundness examinations (BSE) were performed on 327 bulls at three locations in Wyoming and Montana. Scrotal circumference (SC), scrotal volume (SV), and body condition score (BCS) data were also collected. The animals were classified as yearlings, 2-yr-olds, or mature bulls. Age class and BCS had significant (P<0.01) effects on SC. Age class also accounted for significant (P<0.01) variation in SV. The correlation between SC and SV was 0.88. Scrotal circumference, SV, and pelvic area (PA) were measured and adjusted for age on the 139 yearling bulls at Location 1 (MT) to allow comparison with other age-adjusted traits. The linear regression of SC on age was 0.023 cm/d (P<0.05). Scrotal circumference and age were significant (P<0.01) sources of variation for the percentage of motile sperm (MOT). Composite yearling bulls had larger (P<0.05) adjusted SV, adjusted SC, pelvic height (PH), and percentage of MOT than Red Angus yearling bulls. The simple correlation between adjusted SC and adjusted yearling BW was 0.33 (P<0.05). Actual SC and SV were positively correlated with actual BW, actual hip height (HH), and percentage of MOT. Scrotal volume and percentage of MOT were positively correlated (0.22) (P<0.05). Our results indicate that SV could be used interchangeably with SC as a measure of sperm- producing capacity in beef bulls. Results of this study indicate that selecting bulls with larger SC or SV should result in increased yearling BW, greater PA, and bulls with improved fertility.     

Electroejaculation and semen cryopreservation of free-ranging Japanese black bears (Ursus thibetanus japonicus)

The Japanese black bear (Ursus thibetanus japonicus) is endangered for extinction in some areas of Japan, and semen collection and cryopreservation are an important means to preserve genetic resources. The aim of this study was to characterize and cryopreserve semen of free-ranging Japanese black bears. Semen was collected by electroejaculation procedure from 4 free-ranging Japanese black bears at the capture point in the field. Ejaculates containing motile sperm were recovered from all of the animals and ejaculate volume, total sperm count, % motility (percentage of motile spermatozoa), % viability (percentage of spermatozoa that excluded eosin) and % abnormal morphology (range (mean)) were 0.65-2.20 (1.51) ml, 99-1082 (490) x 10(6), 5-100 (31), 42-97 (66) and 20-87 (53), respectively. Three of the 4 ejaculates were diluted with an egg yolk-TRIS-citrate-glucose extender and cryopreserved in liquid nitrogen. Motile spermatozoa were observed after freezing and thawing in all cases. This study showed that electroejaculation would be a useful method for collecting semen from free-ranging Japanese black bears and that at least motile spermatozoa would be obtained by freezing the thus collected electroejaculates.     

Associations among age, scrotal circumference, and proportion of morphologically normal spermatozoa in young beef bulls during an initial breeding soundness examination.

OBJECTIVE: To evaluate age and scrotal circumference as predictors of semen quality in young beef bulls. DESIGN: Cohort study. ANIMALS: 1,173 beef bulls < 15 months old. PROCEDURE: During initial breeding soundness examination, variables for bulls producing > or = 70% morphologically normal spermatozoa were compared with those for bulls producing < 70% morphologically normal spermatozoa. Mean and 95% confidence interval for age and scrotal circumference were constructed to detect differences between groups of bulls over all observations and within the 5 most common breeds. For these 5 breeds, chi 2 analysis was used to evaluate differences in the proportion of bulls that had values less than the population mean for scrotal circumference, age, and percentage of morphologically normal spermatozoa. Multivariate regression was used to quantify variation in the proportion of morphologically normal spermatozoa that could be explained by age and scrotal circumference. RESULTS: Mean (+/- SD) age and scrotal circumference differed significantly for bulls that produced > or = 70% morphologically normal spermatozoa (12.7 +/- 1.1 months and 35.6 +/- 2.7 cm) and bulls that produced < 70% morphologically normal spermatozoa (12.1 +/- 1.2 months and 34.8 +/- 3.3 cm). The proportion of bulls younger than mean age at first examination and the proportion producing > or = 70% morphologically normal spermatozoa differed among breeds. Age and scrotal circumference explained only 11% of the variation in semen quality. CLINICAL IMPLICATIONS: Among young beef bulls, those that were older and had larger testes were more likely to produce > or = 70% morphologically normal spermatozoa. Age and scrotal circumference were not sufficient predictors of semen quality.