Absence of bovine leukosis virus in semen of seropositive bulls.

A polymerase chain reaction (PCR)-based detection system was established to identify the presence of bovine leukosis virus (BLV) DNA in bovine semen. Seventy-nine bulls were included in the study. Serum, peripheral blood leukocytes, and semen were collected from each of the 79 bulls. The BLV-specific antibody was detected in serum by agar gel immunodiffusion and viral DNA in blood and semen by PCR. Serologically, 29 of the 79 bulls were BLV positive. Twenty-seven of the 29 seropositive bulls and 1 of the seronegative bulls had BLV DNA in peripheral blood leukocytes. All 79 bulls tested PCR negative for the presence of BLV in semen. This data is strong evidence that properly collected semen from BLV seropositive bulls will not contribute to dissemination of this viral infection.     

Transmission of bovine viral diarrhoea virus through the semen of acutely infected bulls under field conditions

Epidemiological investigations implicated the semen of artificial insemination (ai) bulls as the only plausible source of infection with bovine viral diarrhoea virus (bvdv) in 10 Finnish dairy herds. The infection was traced back to two northern Finncattle bulls that had been transiently infected when their semen had been collected while they were in a gene bank herd containing persistently infected (pi) animals. The isolates of bvdv from the animals in the gene bank herd, from the semen of the two bulls and from a pi calf born in one of the herds using the semen belonged to a rare genetic type in Finland and, on the basis of the nucleotide sequences in the 5' untranslated region, were identical. Cross-contamination of batches of semen at the ai station and an external source of bvdv were ruled out for the recipient herds. It was concluded that bvdv infection can be transmitted through the semen of transiently infected bulls under field conditions.     

Seroprevalence of bovine immunodeficiency-like virus and bovine leukemia virus in a dairy cattle herd.

To determine the prevalence of single vs. dual infection with bovine immunodeficiency virus (BIV) and bovine leukemia virus (BLV), sera (n = 95) from a dairy cattle herd were analyzed for anti-BIV and anti-BLV antibodies by an enzyme linked immunosorbent assay. Twenty-one percent (20/95) of samples were BIV-seropositive, while 52% (49/95) of the same samples were BLV-seropositive. A significantly greater percentage of BIV-seronegative samples were BLV-seropositive, 57% (43/75), than were BIV-seropositive samples, 30% (6/20). There was no significant correlation between data ranked from least to greatest amount of anti-viral antibody. Five cattle had persistent lymphocytosis (PL); all five were BLV-seropositive and two were BIV-positive. The mean anti-BLV titer was significantly greater in PL cattle, as compared at non-PL cattle, whereas there was no significant difference between the mean anti-BIV titer in PL cattle, as compared with non-PL cattle. These results provide additional information on the seroprevalence of naturally occurring BIV infection, and indicate that BIV can exist independent of other common infectious agents, such as BLV. Further, the results suggest that infection with BIV is not associated with an increased rate of infection with other infectious agents such as BLV.     

In vitro viral expression as a criterion for development of control procedures for enzootic bovine leukosis

In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number.     

Development of a PCR to diagnose BLV genome in frozen semen samples

The sanitary and economic impact of BLV infection is associated with the interference in the international movement of cattle and their germ plasm. Although experimental data support the improbability that semen from BLV-positive bulls could infect recipient cows, restriction for commercialization of semen from infected animals is still present. The objective of this work was to standardize a PCR assay to diagnose the presence of BLV genome in frozen semen samples. The developed methodology involves the amplification of an internal fragment of gag gene. The limit of detection of this technique was six viral particles, using gag-PCR followed by hybridization analysis. Frozen semen samples from seropositive bulls were analyzed. It was possible to detect proviral DNA in 9 out of 173 samples. Additionally, a biological test in susceptible sheep was performed in order to evaluate the transmission of BLV genome by semen from seropositive animals. This data strongly suggest that semen from seropositive bulls that resulted negative by PCR can be used for artificial insemination (AI), accompanied by proper collection protocols. The development of this PCR assay constitutes a valuable diagnostic tool to determine the BLV-free status of frozen semen samples used for AI.     

Seroprevalence of bovine immunodeficiency virus and bovine leukemia virus in dairy and beef cattle in hokkaido

Serological survey of bovine immunodeficiency virus (BIV) and bovine leukemia virus (BLV) infection was conducted in dairy cattle from 10 different regions of Hokkaido, Japan. Among 390 cattle, 11.0% of cattle were BIV-seropositive and 3.3% were BLV-seropositive. Moreover, in two dairy farms, where bovine leukosis has been reported, prevalence of BIV infections were 6.4 and 9.1%, respectively. In contrast, among 150 beef cattle, 16.6% were BIV-seropositive while none was BLV-seropositive. Dual infections with BLV and BIV in dairy cattle were tested by using 107 BLV-seropositive sera, and 20 sera were found BIV-positive (18.7%). These results indicate that BIV infection was widespread in Hokkaido.     

Effects of the Sire and District of A1 on Cow Fertility

Insemination results per bull and district of AI (or technician) were analysed in a 5 year study. Return Rates (RR) were registered between Oct. 1976 and Sept. 1981. Data included 856 850 first AI made by 56 technicians. Depending on years, AI were made with the semen of 81 to 103 bulls of 5 breeds. Only bulls which performed at least 500 AI's per year were taken into account. A first analysis made with the data of 14 bulls represented during the 5 years show that: 1) the breed, the bull within breed and district of AI (or technician) were the most important factors influencing RR. RR were less affected by other factors such as the size of the herd or the year. 2) results given for successive RR were nearly identical from RR₂₄ to RR₉₀. 3) the effect of breed, bull and district of AI were less important on the variable illustrating more specificially late return in oestrus (RR_25–300). Yearly analysis involving larger number of bulls gave very similar results to the 5 year study. Variability due to the district of AI (or technician) and to the bull were of the same magnitude. Maximum differences between bulls or districts varied from 10% (RR₂₄) to 20% (RR₉₀). As strong relationships between bull and district of AI or technician were found, complementary analyses from the 1978 set of data were made to investigate how the variability due to the district of AI could introduce bias when estimating bull's RR. Comparisons between models were made on the basis of correlations between a reference model including a district effect and reduced models. For RR₂₄ and RR₉₀ correlations between solutions were always higher than 0.97. This show that if sufficient number of AI's per bull are performed no major bias is introduced and the district of AI or technician is neglectable when evaluating bull's RR .     

Failure to demonstrate transmission of enzootic bovine leukemia virus infection from cows to sheep by use of common injection needles

Four bovine leukemia virus (BLV)-seropositive and 2 BLV-seronegative cows were used as donors in a study to provide evidence whether IM injection with common needles is a means of spreading bovine leukemia. Sheep were used as recipients. Of the 4 BLV-seropositive cows, 2 had high virus expression (VE; 43% and 28% of their lymphocyte thin sections had associated BLV-particles), whereas the other 2 cows did not have observed VE. After each of the 4 cows was given an injection of a 5-antigen Leptospira bacterin, a BLV-seronegative sheep was immediately given an injection of the same bacterin with the same needle. None of these sheep seroconverted, nor did either of 2 sheep given only the bacterin (with a previously unused needle). Sheep inoculated IM with 0.2 ml of whole blood from both of the cows with high VE and from 1 of the 2 BLV-seropositive cows that did not have observed VE did seroconvert. In contrast, the sheep inoculated with 0.2 ml of blood from the remaining BLV-seropositive (0% VE) cow and from the 2 BLV-seronegative cows remained seronegative. These results were interpreted to indicate that the quantity of infective lymphocytes passed during injection with common needles is too small to induce infection.     

Artificial insemination outcomes in beef females using bovine sperm with a detectable fertility-associated antigen

In this study, semen samples from 25 bulls that had passed a breeding soundness evaluation were analyzed for the presence or absence of a 31-kDa protein, known as fertility-associated antigen (FAA), on spermatozoal membranes. Eighteen bulls had FAA on sperm (FAA-positive) and seven were devoid of FAA on sperm (FAA-negative). A single ejaculate from each bull was extended and frozen with 25 to 30 x 10(6) sperm in .5-mL straws. Crossbred replacement heifers (n = 865) were estrus-synchronized and artificially inseminated either at timed AI or 12 h after they were detected in estrus. Mature cows (n = 285) were inseminated 12 h after they were detected in estrus during a 45-d AI period. Pregnancy rates (pooled) to first AI service for females (n = 764) inseminated with FAA-positive sperm were 65.6% and were 49.7% for females (n = 386) inseminated with FAA-negative sperm (P < .005). Among the estrus-synchronized replacement heifers, pregnancy rates to synchronized AI service for heifers (n = 550) inseminated with FAA-positive sperm were 62% and were 45.7% for heifers (n = 315) inseminated with FAA-negative sperm (P < .005). These data indicate that pregnancy rates to first AI service at spontaneous and synchronized estrus are higher when using semen from bulls with detectable FAA on spermatozoal membranes compared to semen from bulls devoid of FAA on membranes. Fertility-associated antigen is an important determinant for fertility potential of sperm from bulls to be used in AI breeding programs.     

An Outbreak of Enzootic Bovine Leukosis in Upper Egypt: Clinical,Laboratory and Molecular–Epidemiological Studies

In 1989, 220 Holstein Friesian cattle (212 heifers and eight bulls) were imported from Minnesota, USA, to form a closed dairy herd in Arab El‐Aoumar, Assiut, Upper Egypt. In November 1996, some abnormal signs such as loss of weight, decreased milk yield, external lymphadenopathy and decreased appetite were observed on this farm. Serological screening by enzyme‐linked immunosorbent assay revealed a seroprevalence of antibodies directed against bovine leukaemia virus (BLV) of 37.7% in cattle under 2 years old and of 72.8% in animals more than 2 years old. Diagnosis was confirmed by the detection of BLV proviral DNA using polymerase chain reaction with primers amplifying a fragment of the env gene. Out of 21 tested leucocyte fractions from individual animals, 15 were positive showing a BLV‐specific amplicon of 444 base pairs. Analysis of the amplicons for restriction fragment length polymorphisms and DNA sequencing results allowed the isolates to be typed. Since this was the first recorded case of enzootic bovine leukosis in Upper Egypt, strict quarantine measures were adopted and all serologically positive animals in the herd were culled.     

Urogenital infection and seminal excretion after inoculation of bulls and rams with chlamydiae.

Five mature rams and 4 bulls were inoculated parenterally with bovine or ovine chlamydial strains of type 1 and 2. One to 3 days later, all animals developed a chlamydemia lasting 4 to 8 days. Chlamydial agents were isolated from the semen near the end of the chlamydemic phase. All rams and 3 of 4 inoculated bulls excreted chlamydiae in the semen for 22 to 29 days. From 8 to 39 days after inoculation, selected rams or bulls were killed to test for chlamydial infection in the urogenital tract and other organs. Chlamydiae were isolated in developing chicken embryos from testis, epididymis, and accessory sex glands. Bulls examined 29 and 39 days after inoculation did not harbor chlamydiae. Chlamydiae were also not isolated from 3 control bulls which were from the same herd as the principal bulls. All inoculated bulls and rams had a group-specific chlamydial antibody response within 7 days. The titers reached maximal levels of 128 to 512 at 14 days after inoculation. Subsequently, the antibody titers decreased gradually. Seminal plasma collected at different times after animals were inoculated did not fix complement in the presence of chlamydial group antigen. The number of polymorphonuclear leukocytes in the semen increased during the experiment. The semen was grossly purulent in 2 rams inoculated with the type 2 chlamydial strain of polyarthritis.     

Bovine leukaemia virus infection in New Zealand cattle

Bovine Leukaemia Virus (BLV) infection in New Zealand cattle was investigated. In a national survey of 5000 sera from 500 herds, BLV antibody was not detected. An additional 1062 sera from 140 herds were tested and 3 sera were positive. In the herd of origin of one of these 3 sera, 22.6% of cattle were serologically positive for BLV. Where cases of bovine lymphosarcoma had been diagnosed, 38 of 39 herds tested were negative for BLV antibody. Within the remaining herd, 36% of cows tested were serologically-positive. BLV was isolated from 2 serologically positive cows in this herd.     

Bovine leukaemia virus infection in New Zealand cattle

Bovine Leukaemia Virus (BLV) infection in New Zealand cattle was investigated. In a national survey of 5000 sera from 500 herds, BLV antibody was not detected. An additional 1062 sera from 140 herds were tested and 3 sera were positive. In the herd of origin of one of these 3 sera, 22.6% of cattle were serologically positive for BLV. Where cases of bovine lymphosarcoma had been diagnosed, 38 of 39 herds tested were negative for BLV antibody. Within the remaining herd, 36% of cows tested were serologically-positive. BLV was isolated from 2 serologically positive cows in this herd.     

Detection of bovine immunodeficiency virus DNA in the blood and semen of experimentally infected bulls

Five 18- to 24-month-old bulls were inoculated with either a cell suspension containing bovine immunodeficiency virus (BIV-FL112; 3 bulls) or a BIV-free cell suspension (2 bulls). Blood and semen specimens were collected once a week for 14 weeks, and seroconversion was confirmed by indirect immunofluorescent antibody (IFA) testing. The presence of BIV in blood and semen was determined by virus isolation and/or polymerase chain reaction (PCR) assays. Antibodies to BIV were detected in the 3 experimentally infected bulls as early as day post inoculation (DPI) 17, and levels peaked at DPI 37-58. BIV was isolated from the peripheral blood mononuclear cells (MNCs) of the infected bulls at DPI 9 (2 bulls) and DPI 23 (1 bull), and could be isolated from one animal up to DPI 65. PCR analysis of MNC DNA, using BIV pol gene primers, detected virus in all three of the experimentally infected bulls from DPI 9 until the termination of the experiment at DPI 98. Efforts to isolate a significant number of non-spermatozoal cells (NSC) by gradient separation from the semen of the experimentally infected bulls were unsuccessful. Two methods for the extraction of total NSC DNA from up to 2 ml of non-extended semen were employed; however, no BIV pol fragment was amplified from these DNA preparations. Additionally, 30 bulls from artificial insemination (AI) centers were evaluated for BIV infection by PCR. No amplification products were obtained from MNC DNA from the AI submissions using primer sets for both the BIV pol and env genes.     

Effects of crossbreed pregnancies on the abortion risk of Neospora caninum-infected dairy cows

Previous studies have shown that the use of beef bull semen significantly reduces the rate of abortions due to Neospora caninum in artificially inseminated (AI) seropositive dairy cows. In addition, certain beef breeds could be more resistant to N. caninum infection and abortion than others. The aim of the present study was to determine whether different crossbreed pregnancies, those derived from Limousin, Charolais, Piedmontese or Belgian Blue semen, carry different risks of abortion in Neospora-infected dairy cows. The effects of possible interactions between maternal levels of N. caninum antibodies and the different breed crosses were also evaluated. The study was performed on five commercial Holstein–Friesian dairy herds in Northeast Spain with previously confirmed diagnoses of N. caninum infection in aborted foetuses. The study population was comprised of 1115 pregnancies: 633 pregnancies recorded after AI using Holstein–Friesian semen from 18 bulls and 482 after AI using beef semen from 27 bulls (304 inseminations using semen from Limousin bulls, 191 from Belgian Blue bulls, 89 from Piedmontese bulls and 49 from Charolais bulls). Abortion rates were 32.2% (155/482) and 15.2% (96/633) for seropositive cows inseminated with Holstein–Friesian and beef breed semen, respectively. Logistic regression analysis revealed the herd and the interaction between maternal N. caninum antibody titre and the different crossbreeds as significant factors affecting the abortion rate. Lowest abortion rates, similar to that shown by seronegative animals in the analysed herds (3.2%, 239/7432), were observed in dams AI using Limousin semen that had low (<30 relative index (RI) units) N. caninum antibody titres (2.1% abortion, 3/145) and these cows were used as reference. Compared to the cows used as reference, cows with low N. caninum antibody titres (<30 RI units) showed a similar risk of abortion when inseminated with Piedmontese or Charolais bull semen, but higher risk of abortion when inseminated with Holstein (17.9 times) or Belgian Blue (7.2 times) bull semen. All cows with high N. caninum antibody titres (≥30 RI units) had a higher risk of abortion, ranging from 8.9 times (cows inseminated with Limousine semen) to 37.8 times (cows inseminated with Piedmontese semen), compared to the cows used as reference. In conclusion, different crossbreed pregnancies carried different abortion risks in Neospora-infected dairy cows. The use of beef bull semen dramatically reduced the risk of abortion in dairy cows, especially if Limousin breed semen was used. Moreover, this reduction was found to be dependent on the N. caninum antibody titre such that the lowest incidence of abortions was recorded in Limousin semen inseminated cows with low antibody titres. Insemination of Neospora-seropositive cows with beef bull semen could both reduce the risk of abortion and avoid breeding replacements for infected cattle.     

广州地区娟姗种公牛精液品质随月份的变化研究

选择在广州地区亚热带气候条件下2岁～6岁的娟姗公牛5头,观察其精液品质(采精量、原精密度、原精活力以及细管精液产量)在全年不同月份的变化情况.结果表明:娟姗公牛的每次采精量和细管精液产量在气温较高的7～9月份会因为采精频率的减少而增加,10月份会因为周采精频率增加而使每次采精量和细管精液产量有明显减少;娟姗公牛的原精密度在气温适宜的2月份和采精频率较低的8月份会出现两个高峰值;娟姗公牛的原精活力在气温较高的月份会出现明显的下降趋势,2月份气温适宜时原精活力最好.     

饲喂维生素E对种公牛鲜精活力的影响

为了研究维生素E对种公牛精液品质影响,本试验对青海省家畜改良中心一头性欲差、一头精液品质低下的两头荷斯坦种公牛饲喂维生素E胶囊(100mg/粒)。牛20粒/d。一个月为一疗程,连续饲喂两个疗程。研究表明:维生素E与牛精液品质有着密切关系。日粮中添加适量维生素E有助于提高种公牛性欲、精液密度及鲜精活力来改善其精液品质。     

Epidemiologic and economic analyses of an unusually long epizootic of trichomoniasis in a large California dairy herd

An epizootic of trichomoniasis in a large California dairy herd caused an estimated economic loss of $66,538 ($665/infected cow). Greatest losses were caused by infertility (about 50% of losses caused by excess days open). The disease continued in the herd, despite culling older bulls and replacing them with young uninfected bulls and despite institution of an artificial insemination (AI) breeding program for 2 high-production strings. The AI breeder's practice of checking for estrus by vaginal examination was implicated in the spread of the disease. Of 5 cows that became infected before or at conception, 1 had the infection throughout the gestation period and into the next lactation. The prevalence of trichomoniasis in the herd (estimated on the basis of culture results) was 10.67%. The culture method had a calculated sensitivity of only 58.7%. Of 940 cows in the herd, 132 aborted during the epizootic (8 aborted twice); 45 abortions would have been expected in a dairy herd of this size in the absence of trichomoniasis. In high-density mass-bred herds, conditions and/or management practices may be conducive for trichomoniasis transmission, and generally recommended control programs should be adjusted on such dairies. In particular, dairy operators should not assume that culling older bulls and replacing them with young uninfected bulls and that institution of an AI program will be effective in limiting the spread of the disease. Moreover, a diagnostic test with improved sensitivity would greatly assist in the identification of infected cows.     

Survey for antibodies to leukemia (C-type) virus in cattle.

Serums from 4,394 dairy cattle in 100 herds and from 2,794 beef cattle in 50 herds were tested for antibody to the bovine (C-type) leukemia virus (BLV), using the agar gel immunodiffusion test. Reactors were found in 66% of the dairy herds (10.2% of the cattle) and in 14% of the beef herds (1.2% of the cattle). The prevalence of reactors was examined with respect to age, herd size, and sex. Few of the reactors were less than 2 years old. There was a high percentage of reactors in small dairy herds (less than 50 cattle). In 22 dairy herds (1,354 cows and 96 bulls), the rate of infection in cows was compared with that in bulls. In those herds, 13.5% of the cows and 10.4% of the bulls were reactors.