Effect of age on spermiogram of Holstein Friesian × Sahiwal crossbred bulls

This study was conducted on 94 Frieswal (5/8 Holstein Friesian 3/8 Sahiwal) crossbred bulls of three different grades, categorized based on their semen freezability visualising Group 1 (consistently freezable semen producer bulls, N = 11), Group 2 (inconsistent freezable, N = 16) and Group 3 (Non freezable, N = 67). Each group was further divided into two classes that is young (up to 30 months) and adult (31 to 70 months) bulls depending upon their age. Sperm morphology was studied by using the eosin-nigrosin staining technique. Bulls age significantly (P < 0.01) affected semen quality and sperm morphology. In adult bulls, semen volume, mass activity and sperm concentration were 36%, 17.56% and 19.6%, respectively, higher than young. Initial progressive motility (%) and livability showed significant (P < 0.01) improvement with the advancement of age (43.37 ± 1.21 and 67.71 ± 1.11, respectively, in young; 53.02 ± 1.11 and 74.17 ± 1.03, respectively, in adult). In young bulls, sperm head, mid piece, tail abnormality and total abnormal sperm percent (12.38 ± 0.92, 4.87 ± 0.24, 11.01 ± 0.60 and 28.26 ± 1.34, respectively) were 1.85, 1.27, 1.20 and 1.44 folds higher than that of their mature stage (6.69 ± 0.64, 3.82 ± 0.32, 9.14 ± 0.64 and 19.66 ± 1.31, respectively). Significant reduction (P < 0.01) in micro cephalic sperm, free heads, bent mid piece, looped mid piece and proximal protoplasmic droplets were observed at mature age as compared with their younger stage. In bulls of consistent freezing category, abnormal sperm heads significantly decreased from 4.40 ± 0.31% to 3.28 ± 0.02% on maturity. Similarly, in inconsistent freezing grade bulls sperm head abnormality (9.28 ± 0.75% to 5.13 ± 1.20%) and total abnormal sperm percent (24.89 ± 1.43 to 18.73 ± 3.40) was decreased over the age. On the contrary, in non-freezing category bulls' sperm morphology did not show significant (P > 0.05) improvement with age advancement, rather some abnormalities like long slender head, under developed/deformed head, abaxial implantation of mid piece, double mid piece, stump tail and distal protoplasmic droplets tend to increased significantly (P < 0.05) with age of bulls. Results indicated that in potential Frieswal bulls semen quality and sperm morphology were improved from young to mature stage, where as, in poor quality (non-freezing) semen producer bulls neither the morphology nor the semen quality showed any improvement with maturity. It was recommended that crossbred bulls producing more than 25% morphologically abnormal sperms in young age (below 30 months) along with poor progressive motility (<50%) and low sperm concentration (<1000 million/ml) need immediate culling with out any expectation of further improvement in semen quality with age advancement.     

Internal artificial vagina (IAV) to assess breeding behavior of young Bos taurus and Bos indicus bulls

Bull breeding soundness evaluation (BBSE) usually neglects the libido and mating ability evaluation. The internal artificial vagina (IAV) permits semen sampling, as well as mating ability evaluation. Few studies have been performed using IAV with young bulls and there are none with Bos indicus bulls. The present study evaluated sexual behavior, mating ability and semen quality in young Bos taurus (Devon) and B. indicus (Nellore) bulls using the IAV device. In the first experiment, 52 Devon bulls, 18-25 months old were observed, and the behavior and mating ability recorded over a 10-min period within a restrained mount-cow with an IAV inserted. In the second experiment, 20 Nellore bulls, 20-30 months old were evaluated over a 20 min period. Of the 52 Devon bulls, 45 (86.5%) had semen recovered with the IAV, 31 (69.0%) were considered satisfactory. Nellore bulls exhibited a different sexual behavior, with 10 bulls not showing any interest in the females. Four bulls demonstrated sexual interest only once, e.g., sniffing, two showed interest on more than one occasion, and four had more than two mounts or mounting attempts. None out of the Nellore bulls was collected with IAV. The IAV was an effective and welfare-promoting animal technology for the evaluation of semen quality and mating ability of B. taurus bulls. However, the IAV was not adequate for young Nellore bulls, probably due to their quiescent sexual behavior and delayed sexual maturity. Further studies are needed to evaluate the performance of the IAV for older Nellore bulls.     

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.     

Fertility of yearling beef bulls during mating

Crossbred (Bos taurus) yearling beef bulls were assessed for breeding soundness and physical traits prior to multi-sire natural mating at pasture. Bulls (n = 60) were assigned to six groups of nine or 10 bulls and two bull-groups were rotated on 14-day intervals during a 63-day mating season in each breeding herd (n = 3) of 191-196 cows. The remaining bulls (n = 14) were maintained under similar environmental conditions without mating exposure. Bulls were observed during mating and assessed for breeding soundness and changes following mating. Bulls used for breeding (UFB) lost 77 kg of body weight and declined from body condition scores of 6 to 4.5, whereas bulls not used for breeding (NUB) maintained body condition scores of 6 and gained 27 kg. The UFB bulls incurred a 75% total injury rate with 63% incidence of lameness and 12% incidence of reproductive injuries, resulting in a 22% attrition rate. Only 45% were physically sound at the end of mating. Scrotal circumference declined in UFB bulls (-4.58%) and increased in NUB bulls (2.49%). From the 98% BSE-satisfactory rate (UFB) prior to breeding, only 61% were BSE-satisfactory post-breeding. The NUB bulls declined from 57 to 36% satisfactory. The BSE classification was influenced by significant increases in abnormal spermatozoa (primary and secondary), which was significantly associated with injuries incurred during mating. Group and breed differences in injury rates and BSE-status following mating were evident. Environmental conditions and mating activity influenced bull seminal quality and physical condition. Pregnancy rates in all three breeding herds (91-96%) were similar, with insignificant differences between bull-groups; the effects of physical and reproductive changes on individual bull fertility were immeasurable.     

Seminal quality and sperm production in beef bulls with chronic dietary vitamin A deficiency and subsequent re-alimentation

Sixteen Hereford bulls (16 mo of age, 462 kg average body weight) were used in each of 2 yr to evaluate the effects of hypovitaminosis A on seminal quality and sperm production. Bulls were fed a high-concentrate diet with (+VIT) or without (-VIT) supplemental Vitamin A until the apparent onset of hypovitaminosis A (28 and 32 wk in Year 1 and 2, respectively). Half of the bulls on each treatment were then slaughtered and those remaining were re-alimented with Vitamin A. Plasma retinol concentration in -VIT bulls reached a nadir at approximately 25 wk. In Year 1, the proportion of progressively motile spermatozoa was lower in -VIT bulls after 17 wk but returned to that of the +VIT group after re-alimentation. The proportion of spermatozoa with primary morphological defects appeared to be greater in -VIT bulls compared to +VIT bulls by 26 and 24 wk in Year 1 and 2, respectively. The incidence of these defects declined in -VIT bulls upon re-alimentation, and approached the incidence observed in +VIT bulls by 8 to 12 wk of re-alimentation. Hypovitaminosis A decreased paired testes weight, daily sperm production, and epididymal sperm reserves but did not affect daily gain. Prolonged dietary Vitamin A deficiency impaired semen quality and sperm production in the absence of other clinical symptoms. However, under practical feeding conditions, diets that result in long-term, marginal Vitamin A deficiency or a relatively short-term absence of Vitamin A intake probably would have minimal effects on spermatogenesis.     

Sperm Quantity Explains Age-Related Variation in Fertilization Success in the Hide Beetle

Age-related variation in sperm quality and quantity may have a dramatic impact on female fecundity and fertilization success. Despite this, the relationships between these parameters are rarely investigated. Moreover, studies exploring age-related variation in male mating success generally fail to consider the entire lifespan of an individual male; instead they restrict analyses to a small number of defined age classes. As a consequence they are unable to assess the impact of early and late life history components on male reproductive success. In this study, we explore these questions using the hide beetle, Dermestes maculatus , a model species for investigating age-related male mating success. We first employed a longitudinal design to explore whether patterns of sperm transfer and subsequent reproductive success varied over the reproductive lives of a cohort of males. Secondly, we investigated age-related variation in sperm viability, a surrogate measure of sperm quality. Finally, we combined these data and assessed whether the observed patterns of sperm transfer were correlated with fertilization success. We found that the quantity of sperm varied with male age: the amount of sperm transferred to a female increased with male age until 9 wk and then started to decline. Similarly, female fecundity and fertilization success were related to male age: females mating with males when they were relatively young (1 wk) or relatively old (13 wk) suffered reductions in fecundity and fertilization. Our data suggest that fertilization success is driven at least in part by the quantity of sperm transferred during mating.     

Semen quantity and quality correlate with bank vole males’ social status

Laboratory studies reveal that in several rodent species the females prefer dominant males as mating partners. Here we investigate the correlation between bank vole males’ social rank and their sperm quality and quantity. We used agonistic encounters to determine males’ social status. Sperm quality was assessed by its motility, viability, maturity, morphology and sperm tail membrane integrity. Relatively more dominant males were heavier than males of lower social status. The males’ social position affected the testes, seminal vesicles and coagulation gland development. The weights of these reproductive organs were significantly higher in more dominant males than in more subordinate males. Sperm counts and the values of the other parameters describing sperm quality were higher in high-ranking males than in subordinates. Our results suggest that bank vole females benefit from choosing and mating with high-ranking males by obtaining more and better-quality sperm.     

Effects of label-dose permethrin administration in yearling beef cattle: I. Bull reproductive function and testicular histopathology

Pyrethroid administration to a wide variety of laboratory animals has been shown to cause detrimental effects on male fertility, including sperm quality, by means of endocrine disruption. The objective of this experiment was to study the effects of a commercial, permethrin-containing pour-on product on reproductive variables and testicular histopathology of yearling beef bulls. Black Angus bulls (n = 60; aged 369 ± 17 days; 511 ± 33 kg; 6.2 ± 0.5 body condition scores) were assigned to either (1) saline control (CON) or (2) permethrin pour-on administered at label dose (PYR). Blood samples were collected, and industry standard breeding soundness examinations (BSE), via electroejaculation, were performed on all bulls at 5 days before and 14 days after treatment. Progressive sperm motility and eosin-nigrosin–stained sperm were analyzed using high-power phase-contrast microscopy. Plasma testosterone concentrations were analyzed via radioimmunoassay. Bulls were slaughtered at 34 days, and one testicle per bull was randomly collected for histologic examination. Change in sperm motility between BSEs was not different because of treatment; sperm morphology however improved across treatments, but PYR bulls had less improvement in percent of head (P < 0.001) sperm abnormalities compared to CON, resulting in less improvement of primary abnormalities (P = 0.04). Nonetheless, morphological differences did not change the overall outcome for satisfactory breeder status. Change in testosterone concentration did not differ because of treatment. Histopathologic examination identified that testicular degeneration and tubule diameter did not differ as a result of treatment. It should be noted, however, that degeneration score (higher score having more degeneration) was positively correlated with primary abnormalities (P < 0.01; r = 0.35) and negatively correlated with normal sperm cells (P < 0.001; r = −0.43). In summary, these data indicate that a single use of permethrin at label dose in yearling Angus bulls results in minimal detrimental effects on sperm morphology but not to a degree that impacts the ability of bulls to pass a standard BSE.     

Effects of dietary gossypol on aspects of semen quality, sperm morphology and sperm production in young Brahman bulls

Eight young reproductively normal Brahman bulls (average age and bodyweight 20 months and 500 kg, respectively) received either cottonseed meal delivering 8.2 g free gossypol/bull/d (treatment group, n=4) or soybean meal (control group, n=4) for 12 wk. After adjustment (1 wk), weekly procedures (11 wk) included blood collection, scrotal circumference measurement and electroejaculation. Semen assessments included sperm motility, percentage of live spermatozoa, general sperm morphology (using brightfield microscopy), and midpiece morphology (using DIC microscopy). After sacrifice (Week 12), sperm production rates (daily and per gram testicular parenchyma) were determined. Treated bulls did not differ from controls in scrotal circumference or the percentage of live spermatozoa. Sperm motility differed at Weeks 9 (P<0.05), 10 and 11 (both P=0.06). Treated bulls had fewer normal spermatozoa at Weeks 5 (P<0.05), 6 (P<0.01) and 7 thru 11 (P<0.001). Beginning from Week 3, treated bulls showed an increased proportion of sperm midpiece abnormalities (P<0.05) which stabilized at 52 to 62.5% between Weeks 5 and 11 (P<0.01 or P<0.001). Treated bulls also had lower sperm production than untreated bulls, both on a daily (P<0.01) and per gram testicular parenchyma (P<0.001) basis. A cottonseed supplement providing 8.2 g of free gossypol per bull per day had adverse effects upon both sperm morphology and spermatogenesis in young Brahman bulls, with the former being first evident within 3 to 4 weeks of feeding of cottonseed meal.     

Generation of reactive oxygen species in sperms of rats as an earlier marker for evaluating the toxicity of endocrine-disrupting chemicals

Abstract

Bisphenol A (BPA) and diethylstilbestrol (DES) have been reported to cause sperm toxicity. To identify an earlier marker of toxicity of environmental substances or food additives, this study determined whether the levels of reactive oxygen species (ROS) in sperms could serve as indices for the prediction of sperm toxicity and quality. Male Wistar rats were given drinking water containing various doses of BPA or DES for 8 weeks. Some rats were treated with 0.45% N-acetyl cysteine (NAC) for 2 days prior to the administration of DES or BPA. Administration of BPA or DES to rats for 1 week dose-dependently increased the production of ROS, even at doses and time points which had no effect on sperm motility. 4-Hydroxy-2-nonenal modified proteins increased in sperms 8 weeks after BPA or DES treatment. NAC reversed oxidative stress and prevented the loss of sperm function in the DES or BPA-treated group. During observation, changes in the sperm motility, sperm count and morphology were not correlated to the increase in ROS levels. These results suggest that ROS levels may be used as an early indicator of sperm count and quality decreases which result from chronic toxicity.     

Sperm accumulation in the ampullae and cauda epididymides of bulls

Bulls that appear to have an abnormality of sperm transport accumulate large numbers of senescent sperm in the excurrent ducts of the reproductive tract. Six bulls that accumulated sperm were used to determine the number of physiological ejaculations required to deplete accumulated senescent sperm, semen traits during depletion, the period of time to re-accumulate senescent sperm after depletion, the sites of sperm accumulation, and the effect of sperm accumulation on fertility during natural service. Semen was collected from three bulls (HH, PH1, and CH1) three times daily using internal artificial vaginas placed in cows in estrus. These bulls started to produce semen with >or=70% morphologically normal sperm on the third, fifth, and seventh day, respectively. The percentage of live sperm increased from 5% to 68%, 5% to 63%, and 18% to 68% in HH, PH1, and CH1, respectively. Two weeks later the same bulls were electroejaculated every second day for five electroejaculations to deplete stores of senescent sperm. Each time, electroejaculation was continued until the semen produced had a dilute appearance. The three bulls re-accumulated senescent sperm after 1 month of sexual rest. After re-accumulation of senescent sperm, the total volumes of semen in both ampullae recovered at slaughter from HH, PH1, and CH1 were 5.0, 5.0, and 9.5 ml, respectively. The volumes of semen in ampullae recovered at slaughter from two control bulls (RA and CHC) were 1.7 and 1.9 ml, respectively. The number of sperm recovered from both cauda epididymides of HH, PH1, CH1, RA and CHC was 37.3x10(9), 23.3x10(9), 15.0x10(9), 6.9x10(9), and 7.4x10(9), respectively. Bull CH1 and a fourth bull (LM) that also accumulated sperm, started to produce semen with >or=70% morphologically normal sperm, and >or=60% progressively motile sperm on the third electroejaculation after depletion of senescent sperm by repeated electroejaculations. Pregnancy rates achieved by two bulls that accumulated senescent sperm (CH2 and PH2) were less (P<0.05) during the first week of a 21-day breeding period and there was a tendency for lesser pregnancy rates at the end of the breeding period when compared with two normal control bulls. The present study indicates that bulls that accumulate senescent sperm may achieve greater pregnancy rates approximately 1 week after beginning a period of frequent ejaculation. Re-accumulation of an increased percentage of senescent sperm would likely occur after 1 month of sexual rest.     

“Effect of the addition of different catalase concentrations to a TRIS-egg yolk extender on quality and in vitro fertilization rate of frozen-thawed bull sperm’’

The aim of this study was to investigate the effects of different concentrations of catalase in a TRIS-egg yolk extender on sperm quality and embryonic development after in vitro fertilization of frozen-thawed bull sperm. For this purpose, from each of 7 bulls 2 ejaculates were collected and diluted with a TRIS-egg yolk extender containing 0, 5, 10, 15 or 20 IU catalase/mL. Sperm quality was evaluated 0, 3, 6, 12 and 24 h after thawing by using computer assisted analysis of motility and by flow cytometric assays. Embryonic development was determined after in vitro fertilization of bovine oocytes. Semen diluted with TRIS-egg yolk extender containing different concentrations of catalase showed more motile sperm, more sperm with intact plasma membranes, acrosomes and DNA, a high mitochondrial membrane potential, a high esterase activity, a low calcium level, a lower amount of synthesis of reactive oxygen species and lower degree of lipid peroxidation of sperm compared to semen frozen without catalase (P < 0.05), but not before 3 h after thawing. There was a dose-response relationship with the most prominent effect of 20 IU catalase/mL. However, the improvement of sperm quality had no effect (P ≥ 0.05) on embryonic development after in vitro fertilization with 20 IU catalase/mL. In conclusion, the addition of catalase to the sperm extender improved sperm quality with no obvious effect on in vitro fertility.     

Variation in lipid profiles within semen compartments—the bovine model of aging

Semen lipid composition was examined in young and mature bulls. Given the specific roles of various semen compartments (i.e., seminal fluid, sperm head, and sperm tail) during fertilization, we hypothesized that altered fatty acid and cholesterol composition of a specific compartment might impair semen quality and sperm function. Semen samples were collected from five mature and five young Holstein Friesian bulls during the winter (December–January). Semen was evaluated by computerized sperm-quality analyzer for bulls and was centrifuged to separate the sperm from the seminal fluid. The sperm fraction was sonicated to separate its head and tail compartments. Cold extraction of lipids was performed, and fatty acids and cholesterol were identified and quantified by gas chromatography. Semen physiological features (concentration, motility, and progressive motility) did not differ between mature and young bulls. However, lipid composition within fractions varied between groups, with prominent impairments in the head compartment. In particular, the proportions of polyunsaturated fatty acids, omega-3 fatty acids, and docosahexaenoic acid in the intact sperm; seminal fluid; and sperm head were lower in semen collected from mature bulls than in that from young bulls. The finding suggests an age-differential absorption and/or metabolism through spermatogenesis. Reduced proportions of major fatty acids in mature bulls might reduce membrane fluidity, which in turn might affect the ability to undergo cryopreservation and/or oocyte-sperm fusion through fertilization.     

Breeding soundness evaluations of Senepol bulls in the US Virgin Islands

The breeding soundness evaluation (BSE) was used to evaluate Senepol (Bos taurus) bulls (n = 495) on St. Croix over a 7-year period. Young, unproven bulls (10-26 months of age) and breeding bulls (16 months to 8.5 years) were tested prior to sale or use in breeding. Inbreeding coefficients were determined for a subset of bulls (n = 290). The percentage of bulls passing the BSE increased (P < 0.0001) with age. Bulls that passed had a higher percentage (P < 0.0001) of normal and motile sperm as well as a larger (P < 0.0001) scrotal circumference than bulls that failed. No bulls failed the BSE for physical soundness traits or other health reasons. The incidence of testicular hypoplasia was 2.5 and 3.3% and the incidence of cryptorchidism was 1.4 and 0.9% in 12- and 16-month-old bulls, respectively, with no occurrence in bulls >20 months. The proportion of all bulls that failed the BSE and received an Unsatisfactory rating for scrotal circumference or sperm motility decreased (P < 0.0001) from >90 to <25% with age. The proportion of all bulls that failed the BSE and received an Unsatisfactory rating for sperm morphology decreased (P < 0.0001) from 99 to 83.3% with age. The inbreeding coefficient was higher (P < 0.03) in bulls that failed the BSE than in those that passed (2.24 +/- 0.19% versus 1.40 +/- 0.32%, respectively). There was a tendency for bulls with testicular hypoplasia or cryptorchidism to have a higher (P = 0.09) inbreeding coefficient than bulls with normal testes (2.90 +/- 0.46% versus 2.13 +/- 0.11%, respectively). In conclusion, Senepol bulls raised under tropical conditions had a low probability of passing the BSE at young ages, but the passing rate increased with age. Older Senepol bulls were more likely to fail the BSE due to abnormal sperm morphology than due to inadequate testicular size or sperm motility. To prevent unnecessary culling, a BSE should not be performed on Senepol bulls <16 months old.     

Understanding and evaluating bovine testes

The objective is to briefly review bovine testes and how they are assessed, with an emphasis on articles from Theriogenology. Scrotal circumference (SC) is the most common method to assess testicular size; it varies among individual bulls and breeds and is highly heritable. In general, a large SC is associated with early puberty, more sperm, a higher percentage of morphologically normal sperm, and better reproductive performance in closely related females. Consequently, there are minimum requirements for SC for breeding soundness. In prepubertal bull calves, there is an early rise (10–20 weeks of age) in LH, which is critically related to onset of puberty and testicular development. Feeding bulls approximately 130% of maintenance requirements of energy and protein from approximately 8 to 30 weeks of age increased LH release during the early rise, hastened puberty (approximately 1 month), and increased mature testis size and sperm production (approximately 20%–30%). However, high-energy diets after weaning (>200 days) often reduced sperm production and semen quality. A bull's testes and scrotum have opposing (complementary) temperature gradients, which keep the testicular temperature 2 °C to 6 °C cooler than core body temperature for production of fertile sperm (increased testicular temperature reduces semen quality). Infrared thermography, a quick and noninvasive method of assessing scrotal surface temperature, may be beneficial for evaluations of breeding soundness. 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. In conclusion, testis size and function are critical for bull fertility, affected by nutrition, and readily assessed clinically.     

Effect of age and genetic group on characteristics of the scrotum,testes and testicular vascular cones,and on sperm production and semen quality in AI bulls in Brazil

The objectives were to determine the effects of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones (TVC), and on sperm production and semen quality in 107 Bos indicus, B. taurus and cross-bred bulls at three artificial insemination (AI) centers in Brazil. In addition, predictors of sperm production and semen quality were identified. In general, scrotal circumference (SC), scrotal shape score, scrotal neck perimeter, and testicular size (length, width and volume) increased (P < 0.05) with age. Although there were no significant differences among genetic groups for SC or testicular size, B. indicus bulls had the least pendulous scrotal shape, the shortest scrotal neck length, and the greatest scrotal neck perimeter (P < 0.05). Fat covering the TVC was thinner (P < 0.05) in bulls < or = 36 months of age and in B. taurus bulls than in older bulls and B. indicus bulls, respectively. Age and genetic group did not affect testicular ultrasonic echotexture. B. indicus bulls tended (P < 0.1) to have the lowest average scrotal surface temperature (SST). In general, ejaculate volume, total number of spermatozoa and number of viable spermatozoa increased (P < 0.05) with age. However, there was no significant effect of age on sperm concentration, motility, major and total defects. The proportion of spermatozoa with minor defects was highest (P < 0.05) in bulls 37-60 months of age. B. indicus bulls had higher (P < 0.01) sperm concentration, total number of spermatozoa and number of viable spermatozoa than B. taurus bulls, with intermediate values for cross-bred bulls. Increased sperm production was associated with increased testicular volume, SC, TVC fat cover, and SST top-to-bottom gradient. Decreased semen quality was associated with increased SC and bottom SST, and decreased scrotal shape, scrotal neck perimeter and vascular cone diameter. In summary, age and genetic group affected the characteristics of the scrotum, testes, and TVC, sperm production and semen quality. In addition, characteristics of the scrotum, testes and TVC were associated with sperm production and semen quality in bulls and could be assessed for breeding soundness evaluation.     

Cryptic female choice during spermatophore transfer in Tribolium castaneum (Coleoptera: Tenebrionidae)

Sexual selection in both males and females promotes traits and behaviors that allow control over paternity when female mates with multiple males. Nonetheless, mechanisms of cryptic female choice have been consistently overlooked, due to traditional focus on sperm competition as well as difficulty in distinguishing male vs. female influence over processes occurring during and after mating. The first part of this study describes morphology and transformation of Tribolium castaneum spermatophores inferred from dissecting females immediately after normal or interrupted copulations. T. castaneum males are found to transfer spermatophores as an invaginated tube that everts inside the female bursa and which is filled with sperm during copulation. This sequence of events makes it feasible for females to control the sperm quantity transferred in each spermatophore. Through manipulation of the male phenotypic quality (by starvation) and manipulation of female control over sperm transfer (by killing a subset of females), the second part of this study examines whether females use control over transferred sperm quantity as a cryptic choice mechanism. Fed males transferred significantly more sperm per spermatophore than starved males but only when mating with live females. These results suggest an active differentiation by live females against starved males and provide an evidence for the proposed cryptic female choice mechanism.     

Breeding soundness, libido and performance of beef bulls mated to estrus synchronized females

Ninety-three beef bulls and 2316 females were used to determine the relationships between breeding assessments of bulls and subsequent mating performance. Each bull was given a breeding soundness examination (BSE) and two 10-min libido/serving capacity (L/SC) tests. Breeding potential of each bull was classified as satisfactory (BSE score = 60 to 100) or questionable (BSE score = 30 to 59); libido was classified as either high (mean score = 9.0 to 10) or medium (mean score = 6.0 to 8.5). Bulls were then joined, single-sire, with groups of females which had received one of two treatments to synchronize estrus. Bull-to-female ratios ranged from 1:7 to 1:51. Continuous observations were conducted on the mating activity of each group. One bull was removed from the experiment due to a severe breeding problem. Bulls of satisfactory breeding potential (n = 80) did not differ (P > 0.10) from bulls of questionable breeding potential (n = 12) in measurements of mating activity. However, by the end of the synchronized breeding period, bulls classified as satisfactory breeders achieved approximately a 9% higher (P < 0.10) pregnancy rate than did bulls of questionable breeding status (45.6 +/- 2.1% vx 36.5 +/- 5.3%). Bulls with a high libido (n = 69) serviced more (P < 0.01) estrous females (81.3 +/- 3.1% vs 63.5 +/- 4.2%) than bulls with a medium libido (n = 23). However, pregnancy rates achieved by bulls of either libido classification did not differ significantly. Individual components of the BSE as well as mean libido score were poorly correlated with pregnancy rates (r = -0.22 to 0.18). It was concluded that classification of bulls by mean libido score can aid in identifying groups of bulls that service more estrus synchronized females, whereas classification by BSE score aids in identifying groups of bulls that impregnate more females.     

Males mate indiscriminately in the tropical jumping spider Hasarius adansoni (Audouin, 1826)

Traditionally, sexual selection has been seen as a process in which choosy females select non‐choosy males. Recent studies, however, have challenged this view by showing that males can also be choosy in many species. We assessed the sexual preferences in males of the tropical jumping spider Hasarius adansoni (Audouin, 1826). We measured mating effort in males and determined how female quality influences offspring quality, quantity, and survival. We also estimated total sperm load and how much sperm was invested in a mating with a particular female. We found no evidence of male mating effort in terms of mating frequency nor sperm investment. Similarly, there was no relationship between female quality (i.e., size and condition) and offspring quality (i.e., survival and feeding performance) or quantity. We found strong evidence that the sperm invested in a particular female is a function of the amount of sperm the male had available for usage at that particular mating. The fact that males probably find females sequentially, along with the lack of relationship between female quality and offspring quality/quantity, likely explains the lack of differences in mating effort by males.