Association between bovine-leukosis virus seroprevalence and herd-level productivity on US dairy farms

Bovine-leukosis virus (BLV; also termed ‘bovine-leukemia virus’) is a retrovirus that primarily affects lymphoid tissue of dairy and beef cattle. Our objective was to investigate the association between BLV infection and annual value of production (AVP) on dairy herds within the United States, as part of the USDA National Animal Health Monitoring System’s 1996 dairy study. 1006 herds (in 20 states) with at least 30 dairy cows were interviewed during 1996. The agar-gel immunodiffusion test was used to detect serum antibodies to BLV. 10–40 cows from each herd were tested and each tested cow was classified as negative or positive based on results of a single test.

A multivariable regression model was used with the 976 herds with complete data for analysis. When compared to herds with no test-positive cows, herds with test-positive cows produced 218 kg per cow (i.e. 3%) less milk. The average reduction in AVP was $ 59 per cow for test-positive herds relative to test-negative herds. For the dairy industry as a whole, BLV seropositivity was associated with loss to producers of $ 285 million and $ 240 million for consumers. Most of this $ 525 million industry loss was due to reduced milk production in test-positive herds.     

Feline intraocular tumors may arise from transformation of lens epithelium

Feline ocular sarcomas are malignant intraocular neoplasms that are frequently associated with a history of ocular trauma. They usually present as fibrosarcomas, but some have both epithelial and mesenchymal features. The purpose of this study was to determine the cell of origin of a subset of feline intraocular sarcomas that display a mixed epithelial-mesenchymal phenotype, with elaboration of basement membrane-type matrix. We examined the morphology and histochemical and immunohistochemical phenotypes of nine feline intraocular sarcomas. Immunohistochemistry and in situ hybridization were performed to detect expression of crystallin alpha A. In addition, tumors were examined for expression of vimentin, cytokeratin, smooth muscle actin, desmin, melan A, neural cell adhesion molecule, S-100, glial fibrillary acidic protein, nerve growth factor receptor, and collagen type IV. Animals ranged from 7 to 17 years of age--no breed or sex predilection for tumor occurrence was present. Tumors were characterized by mixed epithelial and mesenchymal phenotypes, both of which elaborated basement membrane-type material and expressed vimentin highly. On the basis of collagen type IV and crystallin alpha A immunopositivity, we established that three of nine tumors were of lens epithelial origin. Expression of desmin and smooth muscle actin identified one tumor as a leiomyosarcoma. The remainder were undifferentiated sarcomas of myofibroblastic origin. This is the first report of lens epithelial neoplasia in clinical material from any species. The history and morphologic features of feline ocular sarcomas are reminiscent of feline vaccine-induced sarcomas. These tumors may share pathophysiologic similarities unique to this species.     

3-methylindole induces transient olfactory mucosal injury in ponies

Response to 3-methylindole (3MI) varies among species. Mice recover from 3MI-induced bronchiolar epithelial injury but sustain persistent olfactory mucosal injury with scarring and epithelial metaplasia. In contrast, 3MI induces obliterative bronchiolitis in horses and ponies, but olfactory mucosal injury has not been reported. To evaluate the effect of 3MI on equine olfactory mucosa, ponies were dosed orally with 100 mg 3MI/kg (n = 9) or corn oil vehicle (n = 6). All ponies treated with 3MI developed obliterative bronchiolitis with mild olfactory injury. By 3 days after 3MI dosing, olfactory epithelium appeared disorganized with decreased and uneven surface height and scalloping of the basement membrane zone. Epithelial cells of Bowman's glands were hypertrophic. Proliferation of olfactory epithelium and Bowman's glands was supported by an increased mitotic index and positive immunohistochemical staining for proliferating cell nuclear antigen as compared with controls. The activity of 11beta-hydroxysteroid dehydrogenase, an olfactory mucosal cytosolic enzyme localized to sustentacular and Bowman's glandular epithelial cells, was concurrently decreased. By 9 days postdosing, olfactory mucosal lesions had lessened. Results indicate that 3MI transiently injures equine olfactory mucosa without the extensive necrosis, scarring, or metaplasia seen in murine olfactory mucosa or in equine bronchiolar epithelium.     

Methemoglobinemia and eccentrocytosis in equine erythrocyte flavin adenine dinucleotide deficiency

This report describes erythrocyte biochemical findings in an adult Spanish mustang mare that exhibited persistent methemoglobinemia, eccentrocytosis, and pyknocytosis that were not related to the consumption or administration of an exogenous oxidant. The methemoglobinemia was attributed to a deficiency in cytochrome-b5 reductase (Cb5R) activity, and the eccentrocytes and pyknocytes were attributed to a marked deficiency in reduced nicotinamide adenine dinucleotide phosphate-dependent glutathione reductase (GR) activity that resulted in decreased reduced glutathione concentration within erythrocytes. The GR activity increased to a near-normal value after addition of flavin adenine dinucleotide (FAD) to the enzyme assay, indicating a deficiency of FAD in erythrocytes. The methemoglobinemia, eccentrocytosis, and pyknocytosis were attributed to deficiency of FAD in erythrocytes because the GR and Cb5R enzymes use FAD as a cofactor. This deficiency in FAD results from a defect in erythrocyte riboflavin metabolism, which has not been documented previously in animals.     

Recombinant equine growth hormone administration: effects on synovial fluid biomarkers and cartilage metabolism in horses

REASONS FOR PERFORMING STUDY: Recombinant equine growth hormone (reGH) has recently been evaluated for effects on body condition and wound healing. It has the potential to influence articular cartilage via stimulation of IGF-1. OBJECTIVES: To investigate effects of administration on synovial joint metabolism. METHODS: Six mature horses were given 20 microg/kg bwt reGH daily for 8 weeks by i.m. injection. Three control horses were injected with sterile water. Serum and synovial fluid samples were collected at 6, 8, 11 and 16 weeks for GH and IGF-1 assays. Articular cartilage harvested at week 16 was evaluated by Western analysis using monoclonal antibodies BC-13, BC-4, 8-A-4 and CH-3. RESULTS: Concentrations of IGF-1 in serum and synovial fluid were significantly elevated (P < 0.05) at 6 and 8 weeks in the reGH group. Glycosaminoglycan concentrations in synovial fluid were significantly less than controls at these time points, suggesting that reGH may modulate proteoglycan metabolism in articular cartilage. In the reGH group, there were not any alterations in synovial fluid content of 3B3(-) epitope or aggrecan metabolite, or in aggrecan or link protein catabolites retained within cartilage, that might be expected with development of osteoarthritis. CONCLUSIONS: Intramuscular administration of reGH may be a more efficient means of delivery of IGF-1 to joints for cartilage resurfacing initiatives. POTENTIAL RELEVANCE: We found no alterations in cartilage metabolism indicative of development of osteoarthritis.     

Comparison of serologic tests for detection of Brucella infections in cattle and water buffalo (Bubalus bubalis)

OBJECTIVE: To estimate sensitivity and specificity of 4 commonly used brucellosis screening tests in cattle and domestic water buffalo of Trinidad, and to compare test parameter estimates between cattle and water buffalo. ANIMALS: 391 cattle and 381 water buffalo. PROCEDURE: 4 Brucella-infected herds (2 cattle and 2 water buffalo) and 4 herds (2 of each species) considered to be brucellosis-free were selected. A minimum of 100 animals, or all animals > 1 year of age, were tested from each herd. Serum samples were evaluated for Brucella-specific antibodies by use of standard plate agglutination test (SPAT), card test (CT), buffered plate agglutination test (BPAT), and standard tube agglutination test (STAT). A Bayesian approach was used to estimate sensitivity and specificity of diagnostic tests without the use of a gold standard, assuming conditional independence of tests. RESULTS: Sensitivity and specificity estimates in cattle, respectively, were SPAT, 66.7 and 98.9; CT, 72.7 and 99.6; BPAT, 88.1 and 98.1; and STAT, 80.2 and 99.3. Corresponding test estimates in water buffalo, respectively, were SPAT, 51.4 and 99.3; CT, 90.4 and 99.4; BPAT, 96.3 and 90.7; and STAT, 75.0 and 98.8. Sensitivity of the CT and specificity of the BPAT were different between cattle and water buffalo with at least 95% probability. CONCLUSIONS AND CLINICAL RELEVANCE: Brucellosis serologic test performance varied by species tested, but BPAT had the highest sensitivity for screening cattle and water buffalo. Sensitivity and specificity of more than 2 screening tests can be estimated simultaneously without a gold standard by use of Bayesian techniques.     

Vertical position of the patella in the stifle joint of clinically normal large-breed dogs

OBJECTIVE: To define the vertical position of the patella in clinically normal large-breed dogs. SAMPLE POPULATION: Cadavers of 13 clinically normal large-breed dog. PROCEDURE: Both hind limbs were harvested with intact stifle joints and mounted on a positioning device that allowed full range of motion of the stifle joint. Lateral radiographic views were obtained with the stifle joints positioned at each of 5 angles (148 degrees, 130 degrees, 113 degrees, 96 degrees, and 75 degrees). Vertical position of the patella through a range of motion was depicted on a graph of mean stifle angle versus corresponding mean proximal patellar position (PPP) and distal patellar position (DPP) relative to the femoral trochlea for each dog. Ratio of length of the patellar ligament to length of the patella (L:P) was determined for each dog. Overall mean, SD, and 95% confidence intervals for L:P were calculated for all dogs. RESULTS: Evaluation of vertical position of the patella through a range of motion revealed a nearly linear relationship between joint angle and PPP and joint angle and DPPF Evaluation of L:P results did not reveal significant differences between limbs (left or right) or among joint angles. Overall mean +/- SD L:P for all dogs was 1.68 +/- 0.18 (95% confidence interval, 1.33 to 2.03). CONCLUSIONS AND CLINICAL RELEVANCE: The L:P proved to be a repeatable measurement of vertical patellar position, which is independent of stifle angles from 75 degrees to 148 degrees.This measurement could be used as a quantitative method for diagnosing patella alta and patella baja in large-breed dogs.     

Genetic parameter estimates of yearling live animal ultrasonic measurements in Brangus cattle

The objective of this study was to estimate genetic parameters for real-time ultrasound measurements of longissimus muscle area (LMA), 12th rib backfat thickness (FT), percent intramuscular fat (IMF), and yearling weight (YW) for 1,299 yearling Brangus bulls and heifers. A single ultrasound technician performed all measurements. The number of observations was 1,298, 1,298, 1,215, and 1,170 for LMA, FT, IMF, and YW, respectively. Genetic parameters were estimated for each trait using single- and multiple-trait derivative-free restricted maximal likelihood. Fixed effects were contemporary group (defined as same sex, same age within six months, and same environment), and days of age as a covariate. Correlations were estimated from two-trait models. Heritabilities for LMA, FT, IMF, and YW were 0.31, 0.26, 0.16, and 0.53, respectively. Genetic correlations between LMA and FT, LMA and IMF, LMA and YW, FT and IMF, FT and YW, and IMF and YW were 0.09, 0.25, 0.44, 0.36, 0.42, and 0.31, respectively. Yearling live animal ultrasonic measurements can be used as a selection tool in breeding cattle for the improvement of carcass traits.     

Pituitary responsiveness to GnRH in mares following deslorelin acetate implantation to hasten ovulation

The present experiment characterized the pituitary responsiveness to exogenous GnRH in the first 10 d after ovulation following commercially available deslorelin acetate implantation at the normal dosage for hastening ovulation in mares. Twelve mature, cyclic mares were assessed daily for estrus and three times weekly for ovarian activity starting May 1. Mares achieving a follicle at least 25 mm in diameter or showing signs of estrus were checked daily thereafter for ovarian characteristics. When a follicle >30 mm was detected, mares were administered either a single deslorelin acetate implant or a sham injection and then assessed daily for ovulation. On d 1, 4, 7, and 10 following ovulation, each mare was challenged i.v. with 50 microg GnRH, and blood samples were collected to characterize the LH and FSH responses. The size of the largest follicle on the day of treatment did not differ (P = 0.89) between groups. The number of days from treatment to ovulation was shorter (P < 0.001) by 2.0 d for the treated mares indicating a hastening of ovulation. The size of the largest follicle present on the days of GnRH challenge was larger in the treated mares on d 1 (P = 0.007) but smaller on d 10 (P = 0.02). In addition, the interovulatory interval was longer (P = 0.036) in the treated mares relative to controls by 4.4 d. Concentrations of FSH in plasma of the treated mares were lower (P < 0.05) than control concentrations from d 3 to 12; LH concentrations in the treated mares were lower (P < 0.05) relative to controls on d 0 to 5, d 7, and again on d 20 to 23. Progesterone values were the same (P = 0.99) for both groups from 2 d before ovulation though d 23. There was an interaction of treatment, day, and time of sampling (P < 0.001) for LH and FSH concentrations after injection of GnRH. Both the LH and FSH responses were suppressed (P < 0.009) in the treated mares relative to controls on d 1, 4, and 7; by d 10, the responses of the two groups were equivalent. In conclusion, deslorelin administration in this manner increased the interovulatory interval, consistently suppressed plasma LH and FSH concentrations, and resulted in a complete lack of responsiveness of LH and FSH to GnRH stimulation at the dose used during the first 7 d after the induced ovulation. Together, these results are consistent with a temporary down-regulation of the pituitary gland in response to deslorelin administered in this manner.     

Genotype x environmental interaction for mature size and rate of maturing for Angus,Brahman, and reciprocal-cross cows grazing bermudagrass or endophyte infected fescue

Mature weight and rate of maturing were estimated in 177 Angus, Brahman, and reciprocal-cross cows grazing bermudagrass or endophyte-infected tall fescue over a 4-yr period to evaluate genotype x environment interactions. Data were collected every 28 d until cows were approximately 18 mo of age and then at prebreeding, postcalving, and weaning of calf. All cows with weight data to at least 42 mo of age were included in the analysis. Mature weight and rate of maturing were estimated using the three-parameter growth curve model described by Brody (1945). Data were pooled over year and analyzed by the general linear model procedure of SAS. Included in the models for mature weight and rate of maturing were the independent variables of genotype, environment, and genotype x environment interaction. There was a genotype x environment interaction (P < 0.01) for mature body weight (BW) but not for rate of maturing. Angus cows grazing fescue pastures had greater (P < 0.01) mean mature BW than Angus x Brahman cows grazing bermudagrass (611 +/- 17 vs 546 +/- 16 kg). Angus x Brahman cows grazing bermudagrass had lower (P < 0.05) mean mature BW than Brahman x Angus cows grazing bermudagrass or endophyte-infected fescue and Brahman cows grazing bermudagrass (546 +/- 16 vs 624 +/- 19, 614 +/- 22 and 598 +/- 20 kg, respectively). Brahman cows grazing endophyte-infected fescue had smaller (P < 0.05) mean mature BW than all genotype x forage combinations except for Angus x Brahman cows grazing bermudagrass. Angus cows had a smaller (P < 0.05) mean rate of maturing than Angus x Brahman and Brahman x Angus cows (0.039 +/- 0.002 vs 0.054 +/- 0.002 and 0.049 +/- 0.002%/mo, respectively), respectively, and Angus x Brahman cows had a larger (P < 0.05) mean rate of maturing than Brahman x Angus and Brahman cows (0.054 +/- 0.002 vs 0.049 +/- 0.002 and 0.041 +/- 0.002 %/mo, respectively). There was a direct breed x forage interaction (P < 0.05) for mature BW. These data suggest that the choice of breed type is important in maintaining a crossbreeding program, in that mature BW and rate of maturing are critical to the matching of animal requirements to available production resources.