Determination of serum insulin concentration during intravenous glucose tolerance testing of healthy bulls.

OBJECTIVE: To determine the insulin response curve during IV glucose tolerance testing of mature Holstein bulls. ANIMALS: 8 Holstein bulls between 5 and 8 years old and weighing between 911.5 and 1035.5 kg. PROCEDURE: A 50% glucose solution was rapidly administered IV so that each bull received a mean dose of 258 mg of glucose/kg of body weight. Serum glucose and insulin concentrations were determined before and 30, 60, 120, and 240 minutes after glucose infusion. RESULTS: Serum glucose concentrations 30 and 60 minutes after infusion were significantly greater than baseline concentration. Concentrations returned to baseline values 120 minutes after infusion. Serum insulin concentration was significantly greater 30 minutes after glucose administration, compared with baseline and 240-minute concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous glucose tolerance testing of mature Holstein bulls resulted in a characteristic insulin response curve. Baseline and peak insulin concentrations were higher in these bulls, compared with values reported for mature Norwegian Red cows.

Reference values for selected hematologic and biochemical variables in Holstein bulls of various ages.

OBJECTIVE: To determine reference ranges for hematologic and serum biochemical variables of bulls residing at an artificial insemination center. ANIMALS: 225 healthy Holstein bulls categorized by age into yearling, intermediate age, and adult groups. PROCEDURE: Hematologic and serum biochemical analyses were performed on 1 blood and 1 serum sample from each bull. RESULTS: Significant differences associated with age were identified for 25 of 33 variables. Serum creatinine concentration for clinically normal adult bulls (2.44+/-0.33 mg/dl) was higher than previously reported reference values for adult cattle. There was a reversal of the segmented neutrophil-to-lymphocyte ratio between yearling (0.85:1) and adult (2.6:1) bulls. This was associated with a significant and marked decrease in absolute numbers of lymphocytes per microliter between yearling (5,801+/-1,683) and adult (1,307+/-509) bulls. CLINICAL RELEVANCE: Reference values for selected clinicopathologic variables were generated from the data.

Testicular shape and its relationship to sperm production in mature Holstein bulls.

This study was conducted to determine the relationship between testicular shape, scrotal circumference (SC) and sperm production. Twenty-seven mature Holstein bulls were evaluated subjectively and objectively for testicular shape as indicated by testicular length and width, then placed in 1 of 3 groups. Group 1 contained 17 bulls with a normal ovoid testicular shape and a length to width ratio of 1.61:1 +/- 0.01 (SEM). Group 2 was composed of 4 bulls with a long, slender testicular shape and a length to width ratio of 1.95:1 +/- 0.06 (SEM). Group 3 was comprised of 6 bulls with spheroid-shaped testicles and a length to width ratio of 1.3:1 +/- 0.03 (SEM). All the groups were statistically different for length to width ratios (P < 0.05). Length measurements from cranial to caudal pole of the testis proper were also different between groups (P < 0.05). Width or testicular diameter was different between Group 2 and Group 3 at P < 0.05; however, there was no difference between Group 1 and Group 2 or between Group 1 and Group 3. Predicted volumes and weights of testicles were not significantly different between groups. Scrotal circumference measurements were significantly different between groups (P < 0.05). Group 1 had an average SC of 43.07 +/- 0.36 cm (SEM), Group 2 of 39.33 +/- 1.18 cm (SEM) and Group 3 of 46.22 +/- 0.69 cm (SEM). Sperm production for a twice daily, 2-day-per-week collection schedule revealed a statistically significant difference for sperm output. A total of 2742 ejaculates was evaluated. A total of 1818 ejaculates was evaluated in Group 1, 440 ejaculates in Group 2 and 484 ejaculates in Group 3. The mean spermatozoal harvest per day for Group 1 bulls was 13.62 +/- 0.09 x 10(9) (SEM). Group 2 bulls with the longer-shaped testicles produced 14.82 +/- 0.18 x 10(9) (SEM) spermatozoa per day, and Group 3 bulls, with the more rounded testicle shape and the significantly larger SC produced 11.72 +/- 0.64 x 10(9)(SEM) sperm cells per day. All 3 groups were statistically different at the P = 0.05 level. The results suggest that prediction of sperm production may be dependent on factors other than SC, testicular volume, or weight. Testicular shape may influence sperm output in mature Holstein bulls.

Effect of intramuscular polysulfated glycosaminoglycans on bovine semen production and quality of the cryopreserved semen.

Polysulfated glycosaminoglycans (PSGAG) are widely used to treat cartilage disease in horses. The drug's safety in breeding animals has not been documented. This study determined whether im PSGAG is detrimental to the bull's health and, in particular, the quantity of semen produced or the quality of the cryopreserved product. No clinically significant effect of treatment on hematologic or serum biochemistry parameters was detected, but a significant treatment x time interaction for mean corpuscular volume warrants further investigation. There was an unexplained treatment effect on total daily sperm numbers collected, even though the pre-treatment values were included as co-variates in the statistical analysis to control for any day 0 variability. There was no effect on the percent forward motile sperm in the fresh ejaculate. Although there was no significant effect of treatment on the post-thaw semen data, the power of each statistical analysis was low, ranging from 10% to 19%. Further studies using larger sample sizes are warranted. These preliminary studies suggest that im PSGAG is safe to use in bulls on an experimental basis.

Association between the bovine major histocompatibility complex and chronic posterior spinal paresis--a form of ankylosing spondylitis--in Holstein bulls.

A highly significant association was found between the bovine MHC class I antigen BoLA-A8 and a form of vertebral osteophytosis/ankylosing spondylitis known as chronic posterior spinal paresis (PSP) in Holstein bulls (P < 0.001). In a population study, restricted to unrelated bulls, BoLA-A8 was significantly associated with PSP (P = 0.0015) with a relative risk of 34.6. In a family study, one PSP bull, BoLA A8/A20, sired 13 offspring. BoLA-A8 was significantly associated with PSP (P = 0.0008). All five PSP sons inherited the A8 allele and the eight healthy sons each inherited the A20 allele. In three other families a complete association of BoLA-A8 and PSP was observed. Lod score analysis, using all available families, indicated a significant linkage between BoLA and PSP (lod score = 6.9). Based on clinical observation, pathology, age/sex predilection, and a strong association with a class I MHC molecule, this inflammatory disease appears analogous to the human condition known as ankylosing spondylitis.

Estimation of the sensitivity and specificity of the agar gel immunodiffusion test for bovine leukemia virus: 1,296 cases (1982-1989).

A retrospective study of the results of 12,549 agar gel immunodiffusion tests for bovine leukemia virus, conducted on 1,296 dairy bulls over an 8-year period, was performed to estimate the sensitivity and specificity of the test. The number of tests performed on each bull ranged from 5 to 35, with a mean of 9.7 tests per bull. Bulls were categorized by their agar gel immunodiffusion test responses; 1,069 (82.5%) were noninfected and 227 (17.5%) were infected. Eighteen false-positive results were reported from the noninfected bulls. Test specificity was estimated to be 99.8%. Thirty-one false-negative results were reported from the infected bulls. Test sensitivity was estimated to be 98.5%. Fifty-six bulls had 1 or more positive responses when less than 6 months old. In 26 (46%), these results were thought to be attributable to colostral immunity.

Treatment of slipped capital femoral epiphysis in cattle: 11 cases (1974-1988).

A mixed population of 11 cattle (7 dairy, 4 beef; 9 male, 2 female) were examined because of acute onset of non-weightbearing hind limb lameness. Radiography revealed slipped capital femoral epiphyseal fracture in all cattle, with the exception of one large bull. Ten of the 11 cattle were treated with open reduction and internal fixation, using intramedullary pins. Cattle affected with slipped capital femoral epiphyseal fracture in previous reports typically have been calves that required forced extraction during dystocia. Cattle in this report were in the following 2 age groups in which trauma was the likely cause: 3 to 5 months and 1.5 to 2.3 years. Follow-up information was provided for 7 of the 10 cattle. Four of the 7 were functional and had no clinical signs of arthritis, abnormal gait, atrophy, scarring, contralateral compensation, breakdown, or other difficulty 6 months after surgical correction. If early diagnosis is achieved, it appears that reduction with intramedullary pinning can provide a good long-term prognosis in cattle when function as breeding animals is important to their future value.

Surveillance for persistent bovine viral diarrhea virus infection in four artificial insemination centers.

Four large bovine artificial insemination centers implemented a program of surveillance of resident and newly acquired bulls for persistent bovine viral diarrhea virus infection. Infection was identified in 12 of 1,538 bulls. Several clinical abnormalities, including acute and chronic mucosal disease, were evident among the persistently infected bulls. Semen produced by such bulls consistently contained bovine viral diarrhea virus, and such contamination was not always accompanied by diminished seminal quality. Infected bulls were detected by means of virus isolation tests performed on blood specimens, but not by use of serologic testing. Ten of the 12 persistently infected bulls were results of embryo transfer. Virologic surveillance of breeding herds, artificial insemination and embryo transfer centers, and the cattle trade is necessary to prevent spread of this virus by modern cattle breeding practices. Attention is also necessary to prevent contamination by this virus of the fluids used for recovery, in vitro manipulation, and transfer of bovine embryos.

Scrotal circumference measurements on young Holstein bulls.

Scrotal circumference was measured on all young Holstein bulls entering an artificial insemination center over a 57-month period. A total of 3,008 measurements were taken on 723 bulls between the ages of 5 and 18 months. Mean scrotal circumference, standard deviation, and 10th and 25th percentile statistics were calculated for each one-month interval between 5 and 18 months of age. Scrotal circumference increased as a logarithmic function of age and was best described by a quadratic regression equation. This information provides the veterinary practitioner with indices for normal scrotal circumference measurements for young Holstein bulls, and an estimate of the scrotal circumference growth curve.

Noninfectivity of semen from bulls infected with bovine leukosis virus.

An opportunity for study of the potential role of semen in the transmission of bovine leukosis virus (BLV) was provided when a Jersey herd was found to be BLV-seronegative. This was a closed herd; new genetic material had been introduced by artificial insemination (AI), using semen collected and processed at 7 AI centers in the United States. Of 66 donor bulls from which semen had been collected for AI use in the herd during the 5 years the herd remained seronegative, 24 were consistently BLV-seropositive and 2 became seropositive for BLV during the study. Semen collected from the BLV-seropositive bulls accounted for 1,019 semen units, representing 48.3% of the semen purchased. The maintenance of BLV seronegativity in this herd for 5 years, when semen from BLV-seropositive bulls was used for AI, provided evidence for the lack of infectivity of BLV in bovine semen.

Osteochondrosis, degenerative joint disease, and vertebral osteophytosis in middle-aged bulls.

Twenty-five middle-age (65 +/- 18 months) dairy bulls sent to slaughter for nonmedical reasons were evaluated for joint disease in the stifle and the lumbar vertebrae. Fourteen bulls had degenerative joint disease and 3 had osteochondrosis (osteochondritis dissecans) of the distal end of the femur. These lesions predominantly involved the lateral trochlear ridge. Twenty-one bulls had vertebral osteophytosis. Degenerative joint disease and vertebral osteophytosis were common in these middle-aged bulls and, even when severe, were rarely associated with lameness.