Non-infectivity of semen from bulls infected with bovine leukosis virus

Semen and serum were obtained from four bovine leukosis virus (BLV) infected bulls from each of eight bull studs. The samples from the 32 bulls were frozen and stored in liquid nitrogen for subsequent testing. The sera were tested for antibodies to BLV by the agar gel immunodiffusion (AGID) method. Thirty of the bulls were found to be infected with BLV. Pairs of sheep were intraperitoneally inoculated with semen pools of the four bulls from each bull stud. None of the sheep developed antibodies to BLV. A later challenge with BLV infected lymphocytes resulted in the infection of all challenged sheep indicating that they were susceptible to BLV infection. The results provide evidence that transmission of BLV via leukocyte free semen from BLV infected bulls does not occur.     

Differences in bull spermiograms using eosin-nigrosin stain, feulgen stain, and phase contrast microscopy methods

The Society for Theriogenology recently adopted a minimum standard of 70% normal spermatozoa for the bull breeding soundness examination (BSE). We conducted this study to determine if spermiograms derived by brightfield microscopy of eosin-nigrosin stained semen smears (Society method) overestimated the proportion of normal spermatozoa. Comparison of the above method was made with that of phase contrast microscopy (Phase method). We then evaluated our ability to discern head abnormalities by comparing brightfield microscopy of Feulgen-stained sperm DNA (Feulgen method) with those of the Society and Phase methods. Spermiograms were determined for each of the 181 beef bulls using all 3 methods. Only bulls that were being routinely tested prior to the 1993 breeding season were included. The mean percentage of normal spermatozoa surpassed the minimum standard with the Society (72.8%) but not the Phase (52.5%) method, which identified more distal cytoplasmic droplets that adhered to cells without distal midpiece reflexes. The Phase method also identified more total primary and fewer primary head abnormalities. We conclude that the Phase method is not a suitable substitute for the Society method when applying the minimum standard during a routine BSE. The Feulgen method identified more head abnormalities, especially in the pattern of DNA, than the other methods, however, when compared to the minimum standard that improvement was not clinically important. Both the Phase and Feulgen methods are better than the Society method for monitoring changes in abnormal spermiograms over time.     

Infectious Bovine Rhinotracheitis Virus Infection in Bulls, with Special Reference to Preputial Infection

In an experiment with infectious bovine rhinotracheitis (IBR) virus in two bulls, observed over a period of 122 weeks, the pattern of virus release was studied. Recurrent, unprovoked release of virus was demonstrated after one year in a nasal washing from one of the bulls and in preputial washings of both on 13 and 4 occasions, respectively, and finally in weeks 113 and 110, although clinical disease was not observed. During periods of recurrent virus release, concentrations of virus in the prepuce were generally much lower than during the period of primary infection; usually, however, they were not of negligible titer. The frequency of such periods and the virus titers observed strongly suggest that an IBR antibody carrier should always be considered as a potential source of infection to other animals. When virus was demonstrated in semen an almost equal amount was found in the preputial washing (50 ml). In week 120, virus replication in the respiratory tract and prepuce was induced in both bulls by prednisolone injections. It is concluded that antibody carriers will rarely attain a state of absolute immunity.     

Distribution of Corynebacterium renale among healthy bulls with special reference to inhabitation of type III in the prepuce.

Distribution of Corynebacterium renale among apparently healthy bulls reared in Hokkaido was investigated. The organism was detected from 46 (39.3%) of 117 specimens of preputial cavity washing and from 60 (51.7%) of 116 specimens of semen. The isolates studied in this survey belonged to type III, except a few which belonged to type II. No type I strain was isolated from any bull. C. renale type III was isolated from the prepuce in six of seven bulls slaughtered and from urethra in three, but not at all from any other organ. In the seven bulls, no macroscopic changes were seen, but a slight infiltration of lymphocytes and formation of lymph nodules were noticed in the prepuce. No other microscopical changes could be demonstrated in any other organ. No serum antibody response was detected. To ascertain the virulence of C. renale isolated from the bulls, a strain of type II was inoculated into the urinary bladder of a healthy cow. The cow exhibited fever and hematuria on and after the 10th day. Typical cystitis was proved when the cow was necropsied on the 14th day after inoculation. From these result it is conceived that C. renale type II organisms inhabit the prepuce of apparently healthy bulls at a high rate, without inducing any disturbance.     

Relationships among seminal culture, seminal white blood cells, and the percentage of primary sperm abnormalities in bulls evaluated prior to the breeding season

Semen samples from 100 beef breed bulls were evaluated for sperm morphology (phased contrast microscopy), seminal white blood cells, and the presence of potential reproductive pathogens. Eligibility required visualization of the glans penis throughout semen collection. Based on clinical spermiograms, bulls were grouped into normal, marginal, or unsatisfactory morphology classifications. The 3 experimental groups were similar in age and scrotal circumference and differed significantly in the percentage of primary sperm abnormalities. Most semen samples (94%) contained one or more potential reproductive pathogens (Hemophilus somnus. Mycoplasma bovigenitalium, Arcanobacterium pyogenes and Ureaplasma diversum). No significant relationship could be demonstrated between primary abnormalities and the assigned culture score. Our experimental results suggest that clinicians should interpret clinical semen culture results with great care. No significant relationship could be demonstrated between primary abnormalities and assigned white blood cell (WBC) score, although, only 1% of the samples was scored >5 WBC per high power field. The use of seminal WBC score may be valid adjunct to routine semen evaluation when that threshold is the basis for clinical decisions.     

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.     

Fertilizing potential in vitro of semen from young beef bulls containing a high or low percentage of sperm with a proximal droplet

Fertilizing potential of semen containing a high percentage of sperm with a proximal droplet was evaluated using IVF. Design criteria: (a) specified semen with >100 x 10(6) sperm/mL with >40% progressively motile spermatozoa, after collection via electro-stimulation; (b) designated a droplet group, bulls whose semen contained >30% spermatozoa with a proximal droplet and <25% with other morphological abnormalities, and a control group, with <25% abnormalities of any type; and (c) stipulated evaluations at 11 to 13 mo of age and again -4 wk later. At the initial evaluation, when a bull was assigned to the droplet group, the next bull meeting control criteria was designated his pair; 15 pairs in four herds were studied. Semen was extended in egg-yolk citrate, cooled to 5 degrees C over approximately 2.5 h, and held at 5 degrees C. After 20 to 44 h, spermatozoa were processed by swimup, incubated with heparin, and co-cultured with oocytes (35 to 56 oocytes/sample; 18 h). Ova were observed for cleavage approximately 42 h after co-culture, and further development was evaluated on day 8. At first evaluation, cleavage rates were 18 and 46% for droplet and control groups (P < 0.01); semen had 34 to 70% and 0 to 12% droplet spermatozoa. For 10 of 15 droplet bulls, <10% of ova were cleaved whereas cleavage rate was >15% for all control bulls. At second evaluation, only three droplet bulls still had >30% of spermatozoa with a proximal droplet. Cleavage rates increased accordingly; only four droplet bulls had <10% cleaved ova and 10 had >34% cleaved ova. Three control bulls had <10% cleaved ova and nine had > or = 34% cleaved ova. Considering all 60 ejaculates, correlation between percentage of spermatozoa with a proximal droplet and percentage of cleaved ova was -0.49 (P < 0.0 1). Correlations between percentages of motile or normal spermatozoa in field evaluations and outcome in IVF were 0.28 and 0.52. Laboratory evaluations of spermatozoa concomitant with preparation for IVF revealed that only incidence of proximal droplets appeared related to outcome in IVF. We concluded: (a) semen from most yearling beef bulls with a high incidence of proximal droplet spermatozoa had severely compromised IVF fertility; (b) as these bulls matured, the incidence of proximal droplets decreased, and IVF fertilizing potential increased; and (c) semen containing >30% spermatozoa with a proximal droplet is strong evidence that fertilizing potential of the bull will be low until the incidence decreases.     

Bull sperm surface "craters" and other aspects of semen quality

Semen from 200 Holstein bulls in an artificial insemination center was examined for the frequency of craters on the surface of sperm heads, as visualized with the aid of differential interference contrast microscopy. Semen from 100 of these bulls was examined in more detail in 2 experiments by staining with eosin-aniline blue to determine the relationship of unstained spermatozoa, and spermatozoa with normal acrosomes with apical ridges to the incidence of craters and fertility. Only 3 of 100 bulls had a substantial incidence of craters (15 to 23%), whereas the average of the other 97 bulls in 2 experiments was 1 to 3%. The percentage of sperm cells with craters was correlated (P < 0.05) with the percentage of unstained spermatozoa (r = -0.29 and sperm cells with normal acrosomes (r = -0.52) but was not significantly correlated (r = -0.24) with the nonreturn rate. One bull with many sperm cells with craters was slaughtered, and the epididymal spermatozoa were examined. The high incidence of sperm cells with craters was limited to one side, with the testis on that side having 2 Sertoli cell tumors. The remaining 2 bulls as well as one other that produced 16% of sperm cells with craters did so only temporarily. Within a few months crater sperm production had decreased and semen quality increased. The condition usually appears to be transitory, presumably due to temporary stress.     

Serologic survey for bovine pathogens in free-ranging European bison from Poland

From 1980 to 1983, blood was taken from 60 selected European bison (Bison bonasus) in Poland. Serum samples were tested for the presence of antibodies against Brucella abortus, 14 serovars of Leptospira interrogans, Chlamydia spp., Coxiella burnetti; foot and and mouth disease virus, bovine leukemia virus and bovine herpes virus-1. In addition, an attempt was made to isolate bovine herpes virus-1 from the prepuce of selected bulls. Serological tests suggested chlamydial infection in 28 bison, subclinical Q-fever of a 2-yr-old heifer, subclinical bovine leukemia virus infection in a 12-yr-old bull and bovine herpes virus-1 infection in five bulls and three cows. Attempts to isolate bovine herpes virus-1 were not successful. These results suggest the possibility of cross transmission of several of these bovine pathogens between free-ranging bison and domestic cattle in Poland.     

Phenotypic relationships between hair whorl characteristics and spermatozoal attributes in Holstein bulls

The objective of this study was to characterize facial whorl characteristics in Holstein stud bulls (n = 485) and to investigate their association with measures of semen quantity and quality. Bulls had 1 (n = 454), 2 (n = 21) or no facial hair whorls (n = 5). Some 39% of bulls had whorls in the middle of their forehead, whereas 43% had whorls very low down on their forehead. Spiral whorls were present on 77% of bulls while 22% had elongated whorls. Abnormally shaped whorls were found more often on bulls with low whorls (27% versus 17%, P = 0.01) than on bulls with high or middle whorls. Semen production data were obtained from the AI center database to provide a representative sample of each sires most recent semen production characteristics. The number of semen collections per bull averaged 38 with a range of 1 (n = 9) to 272 (n = 1). The average number of days between collections was 5 but varied from 1 to 425 days. Average age of bulls at first recorded collection was 679 days and ranged from 307 to 4555 days. There were no significant differences between black and white bulls in semen quality or quantity. Semen quality over the summer months was reduced in comparison to the winter months. Age of the bull at time of collection had no effect on any of the semen quality traits. Older bulls had larger scrotal circumference and produced more semen (P > 0.01). Bulls with whorls located in the center of the forehead were not significantly different in semen quality or quantity for the 10 traits considered when compared to bulls with whorls located outside the center. In contrast to previous research findings with Angus cattle, semen attributes were not significantly different between bulls characterized with round (or spiral) epicenters and those with abnormally shaped whorls. The difference between the two studies may be due to the fact that Angus bulls have a higher percentage of abnormal elongated whorls compared to Holsteins.     

Pathogenicity of molecularly cloned bovine leukemia virus.

To delineate the mechanisms of bovine leukemia virus (BLV) pathogenesis, four full-length BLV clones, 1, 8, 9, and 13, derived from the transformed cell line FLK-BLV and a clone construct, pBLV913, were introduced into bovine spleen cells by microinjection. Microinjected cells exhibited cytopathic effects and produced BLV p24 and gp51 antigens and infectious virus. The construct, pBLV913, was selected for infection of two sheep by inoculation of microinjected cells. After 15 months, peripheral blood mononuclear cells from these sheep served as inocula for the transfer of infection to four additional sheep. All six infected sheep seroconverted to BLV and had detectable BLV DNA in peripheral blood mononuclear cells after amplification by polymerase chain reaction. Four of the six sheep developed altered B/T-lymphocyte ratios between 33 and 53 months postinfection. One sheep died of unrelated causes, and one remained hematologically normal. Two of the affected sheep developed B lymphocytosis comparable to that observed in animals inoculated with peripheral blood mononuclear cells from BLV-infected cattle. This expanded B-lymphocyte population was characterized by elevated expression of B-cell surface markers, spontaneous blastogenesis, virus expression in vitro, and increased, polyclonally integrated provirus. One of these two sheep developed lymphocytic leukemia-lymphoma at 57 months postinfection. Leukemic cells had the same phenotype and harbored a single, monoclonally integrated provirus but produced no virus after in vitro cultivation. The range in clinical response to in vivo infection with cloned BLV suggests an important role for host immune response in the progression of virus replication and pathogenesis.     

Incidence and ultrastructure of “crater” defect of bovine spermatozoa

The “crater” defect of bovine spermatozoa is a narrow-mouthed invagination of the nuclear membrane that appears as a surface-oriented crater under differential interference contrast microscopy. Craters are most often located directly posterior to the apical ridge or at the acro-some-postnuclear cap junction. Elevated incidence of craters (>20%) is indicative of impaired spermiogenesis and poor seminal quality and, probably, subfertility. In a survey of 316 ejaculates from 46 Alberta beef bulls representing a wide range of breeds and ages and with poorly documented fertility data, 13% of the ejaculates and 28% of the bulls had crater incidence above 20%. Significant differences were not found between crater levels in first and second ejaculates within a day nor among ejaculates collected over three successive collection days. Crater incidence did not differ between ejaculates collected over two collection periods 1 month apart. Differences among bulls were highly significant in all comparisons. It is recommended that more attention be given to the presence of the crater defect during the evaluation of bovine semen and of the reproductive capacity of beef bulls.     

Early Syncytium Formation by Bovine Leukemia Virus

Bovine leukemia virus (BLV) from either persistently infected bat cells or fetal lamb kidney cells induced rapid syncytium formation in F81 indicator cells. Distinct syncytia were seen within 2 h after inoculation of cells with highly concentrated (500-fold) cell-free BLV preparations and within 4 to 8 h when unconcentrated cell-free BLV preparations were used. Indicator cell densities of 1 x 10(5) to 2 x 10(5) were optimal for rapid and maximal syncytium formation. Pretreatment of BLV with reference BLV leukemic serum and antiserum prepared against purified BLV significantly inhibited (95%) syncytium formation. Reference bovine viral diarrhea virus serum, foamy-like bovine syncytial virus serum, and control serum had little effect (17% inhibition). Antiserum to BLV gp51 inhibited syncytium formation by greater than 96%, whereas antiserum to BLV p24 reduced syncytium activity to a much lesser extent (38% inhibition). Treatment of BLV with beta-propiolactone (0.005 to 0.05%) had little or no effect upon syncytium-forming activity, whereas UV irradiation (15 ergs/mm(2) per s for 30 min) reduced, but did not completely destroy, the fusion activity. However, both beta-propiolactone and UV irradiation drastically reduced the replication potential of BLV, as demonstrated by the lack of p24 expression in the inoculated cells. Concentrations of cycloheximide, cytosine arabinoside, tunicamycin, and 2-deoxy-D-glucose which effectively blocked cellular macromolecular synthesis did not significantly inhibit syncytium formation. These latter results suggested that de novo protein and DNA synthesis as well as protein glycosylation were not required for early syncytium formation. Thus, these experiments demonstrated that replication of BLV by the indicator cells was not essential for cell fusion.     

Embryonic loss in superovulated cattle caused by the 1;29 Robertsonian translocation

The effect of the 1;29 Robertsonian translocation on fertility was studied using embryos resulting from matings of nine carrier cows and two carrier bulls. Embryos were collected from the following three mating groups utilizing superovulation: normal bull cross normal cow, normal bull cross translocation carrier cow, and translocation carrier bull cross normal cow. The proportion of ova which were fertilized did not vary among the groups, indicating that fertilization rates were not affected by the translocation. The translocation cows did yield fewer embryos on average than did cows with normal karyotypes, which may suggest ovulation rates are reduced (at least after superovulation attempts) in cattle carrying the 1;29 translocation. Twenty of 39 embryos successfully karyotyped had abnormal chromosome complements. All four of the theoretically predicted karyotypes and two additional abnormal combinations were found. Eight of 39 (20.5%) embryos karyotyped had unbalanced karyotypes which would have resulted in embryonic loss. The proportion of embryos with unbalanced karyotypes, was slightly higher when the cow (36%) carried the translocation than when the bull (19%) did. Results of this study indicate that fertility is impaired due to the presence of this translocation. The major loss in reproductive potential appears to be due to embryonic loss rather than fertilization failure.     

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.     

Prevalence of Theileria sergenti infection in Korean native cattle by polymerase chain reaction

This study was performed to investigate the prevalence of theileriosis and to compare the prevalence of this disease in Korean native cattle reared under different environmental conditions, namely, in a grazing area and a non-grazing area by polymerase chain reaction. Three hundred and one Korean native cattle (276 cows and 25 bulls) that had not received prior treatment or been vaccinated to prevent theileriosis were examined by PCR for Theileria sergenti infection from 2001 to 2002. In our study, the parasitemia range in T. sergenti-positive cattle by microscopy were from 0.1 to 3% (mean 0.8%). In terms of mean prevalence, 204 of the 301 Korean native cattle (67.8%) were positive reaction by PCR. Our results also revealed that the infection rate among cows (70.3%) was significantly higher than that among bulls (40.0%) (p < 0.01). T. sergenti infection among the over 3 year-old-group (75%) had a significant higher prevalence than that among the less than 3 year-old-group (61.8%) (p < 0.05). Our data also showed that grazing areas (76.1%) had the significant higher prevalence than non-grazing areas (51%) (p < 0.001). In conclusion, this study demonstrates that the prevalence of T. sergenti infection is high and that its prevalence in grazing cattle is higher than that in non-grazing cattle. Therefore, life-long treatment and the development of an optimal vaccine are needed to reduce the numbers of bovine theileriosis in both grazing and non-grazing areas.     

Bull selection and use in northern Australia. 5. Social behaviour and management

Calf output of bulls was derived using DNA typing for paternity following multiple-sire mating at two sites in northern Australia. At Swan's Lagoon Beef Cattle Research Station, 12, mixed-age, Brahman cross bulls were continuously mated with an average of 325 females in a 22km2 open-savannah paddock. Water was available in two troughs. Behaviour of the bulls and location of cows were monitored. At Kamilaroi Station, 2- to 2.5-year-old Brahman bulls were introduced to the study. Twenty-four bulls (HIGH%) were mated in an 84km2 paddock for 3.5 months to 411 heifers in 1995/1995 and for 4.5 months to 350 heifers and 320 first-lactation cows in 1995/1996. A second group of 10 bulls (LOW%) selected on reproductive soundness was mated concurrently in a neighbouring 60km2 paddock to 411 heifers in 1995/1995 and to 350 heifers and 298 first-lactation cows in 1995/1996. In each paddock in both years, 300-350 females were expected to cycle during mating. Both paddocks were flat and semi-forested and water was available only at troughs. At both sites, detailed physical and reproductive examinations of all bulls were conducted prior to and post-mating.Calf output of individual bulls was highly variable but repeatable (r=0.6-0.7) between years. Up to 90% of the 270-380 calves resulting from each mating were sired by between 6 and 8 bulls. Reducing from 3.7 to 2.8% bulls:females at Swan's Lagoon did not delay conceptions. At Kamilaroi, reproductively sound bulls achieved an estimated 5-6 conceptions per week over the peak mating period when sufficient cycling females were available. Differences in pregnancy rates between paddocks appeared due to differences in nutrition and it appeared that conceptions were not delayed with LOW% vs. HIGH% bulls. Variance between bulls in calf output was substantially lower when fewer bulls were used. Bull attrition occurred each year in the HIGH% paddock but not in the LOW% paddock. Calf output was unrelated to body condition of bulls.Seven of the 12 bulls in one 2-year period at Swan's Lagoon appeared to restrict their movement range to 250-750ha for 90-100% of the time. These ranges expanded when the bull:female ratio was reduced. Only one of the nine bulls remained within a 500ha home range for at least 85% of the time during peak mating in 1998 at 2.8% bulls:females. In previous years with 3.7% bulls:females, up to eight of the 12 bulls had remained within a 500ha home range for 85% of the time. Bull behaviour related to high calf output included restricted movement range, grazing with females at a majority of observations, stable social behaviour, and social dominance.These observations demonstrate that multiple-sire mating of reproductively sound Brahman and Brahman-derived bulls at 2.5% of cycling females will not jeopardise herd fertility under extensive management in northern Australia.     

Exposure to Bovine Leukemia Virus Is Associated with Breast Cancer: A Case-Control Study

Background

Age, reproductive history, hormones, genetics, and lifestyle are known risk factors for breast cancer, but the agents that initiate cellular changes from normal to malignant are not understood. We previously detected bovine leukemia virus (BLV), a common oncogenic virus of cattle, in the breast epithelium of humans. The objective of this study was to determine whether the presence of BLV DNA in human mammary epithelium is associated with breast cancer.

Methods

This was a case-control study of archival formalin fixed paraffin embedded breast tissues from 239 donors, received 2002–2008 from the Cooperative Human Tissue Network. Case definition as breast cancer versus normal (women with no history of breast cancer) was established through medical records and examination of tissues by an anatomical pathologist. Breast exposure to BLV was determined by in situ-PCR detection of a biomarker, BLV DNA, localized within mammary epithelium.

Results

The frequency of BLV DNA in mammary epithelium from women with breast cancer (59%) was significantly higher than in normal controls (29%) (multiply- adjusted odds ratio = 3.07, confidence interval = 1.66–5.69, p = .0004, attributable risk = 37%). In women with premalignant breast changes the frequency of BLV DNA was intermediate (38%) between that of women with breast cancer and normal controls (p for trend < .001).

Conclusions

Among the specimens in this study, the presence of amplified BLV DNA was significantly associated with breast cancer. The odds ratio magnitude was comparable to those of well-established breast cancer risk factors related to reproductive history, hormones, and lifestyle and was exceeded only by risk factors related to genetics (familial breast cancer), high dose ionizing radiation, and age. These findings have the potential for primary and secondary prevention of breast cancer.     

Sexual development in early- and late-maturing Bos indicus and Bos indicus x Bos taurus crossbred bulls in Brazil

Two experiments were conducted to evaluate sexual development in early- and late-maturing Nelore (Bos indicus) and Canchim (3/8 Bos indicus x 5/8 Bos taurus crossbred) bulls and to determine predictors of sexual precocity, and pubertal and maturity status. In Experiment 1, 12 Nelore bulls where examined from 300 to 900 days of age. Puberty was characterized by an ejaculate containing > or =50 million sperm with > or =10% motile sperm, and maturity by an ejaculate containing > or =70% morphologically normal sperm. In Experiment 2, 28 Canchim bulls where examined from 295 to 488 days of age and puberty was characterized by an ejaculate containing > or =30% motile sperm. In both experiments, bulls were classified as early- or late-maturing based on age at puberty. Early-maturing bulls were younger (P < 0.05) than late-maturing bulls at puberty (527 days versus 673 days in Experiment 1 and 360 days versus 461 days in Experiment 2) and at maturity (660 days versus 768 days in Experiment 1). In general, early-maturing bulls were heavier and had greater scrotal circumference (SC), testes, and testicular vascular cone diameter than late-maturing bulls during the experimental period. Scrotal circumference adjusted for 365 days of age was a good predictor of sexual precocity; minimum yearling SC of 19 and 24 cm for Nelore and Canchim bulls, respectively, had the best predictive values. Early-maturing bulls were lighter and had smaller SC at puberty than late-maturing bulls; therefore, sexual precocity was not related to the attainment of a threshold body weight or testicular size earlier, but to lower thresholds in early-maturing bulls. When predictors of pubertal status were evaluated, SC had the best sensitivity/specificity relationship in Nelore bulls, and high sensitivity and specificity in Canchim bulls. When predictors of sexual maturity were evaluated in Nelore bulls, age, weight, and SC had similar sensitivity, specificity, and predictive values. At puberty, approximately 60% of the sperm present in the ejaculate were morphologically defective. Changes in semen quality after puberty in Nelore bulls were characterized by increased motility and proportion of morphologically normal sperm, with a decrease in the proportion of major sperm defects. In conclusion, early-maturing bulls were more developed in the pre-pubertal period and attained puberty at earlier stages of body and testicular development than late-maturing bulls. Yearling SC could be used to select bulls for sexual precocity and SC was the best predictor of pubertal status. Age, weight, and SC were equally good predictors of sexual maturity in B. indicus bulls.