Association of a genetic marker with blood serum insulin-like growth factor-I concentration and growth traits in Angus cattle

The objective of this research was to evaluate a biallelic genetic marker identified in the first promoter region of the bovine IGF-I gene. The point mutation was identified as a T-to-C transition by sequencing the polymorphic fragments. A PCR-RFLP procedure was developed for determining the marker genotypes. Marker genotypes were determined for 760 Angus calves from divergent lines that were created by selection for high or low serum IGF-I concentration (allele A: 63.9%, B: 36.1%). Data were analyzed using the multiple-trait derivative-free restricted maximum likelihood computer programs with animal models. The full animal model included fixed effects of marker genotype, birth year, season of birth, sex, age of dam, and selection line; random effects of animal, maternal genetic, and maternal permanent environmental effects; and a covariate for age of calf. Traits analyzed included blood serum IGF-I concentrations on d 28, 42, and 56 of the postweaning test, mean IGF-I concentration, birth weight, weaning weight, on-test weight, off-test weight, off-test hip height, postweaning gain, and weight gain during the 20-d period immediately after weaning. Results from the analysis across selection lines showed a significant association of the BB genotype with higher weight gain during the first 20 d after weaning and a slight dominance effect of the marker on postweaning gain. Analysis within the low IGF-I line also showed a significant association of the BB genotype with higher weight gain during the first 20 d after weaning and with on-test weight, although analysis within the high IGF-I line did not show any significant association. The associated effects of the marker need to be verified in other cattle populations.     

Effects of inhalation of albuterol sulphate, ipratroprium bromide and frusemide on breathing mechanics and gas exchange in healthy exercising horses

The possibility that pre-exercise inhalation of a bronchodilator by healthy horses could improve their mechanics of breathing and enhance performance was investigated. Ipratropium bromide (0.35 microg/kg bwt; n = 7) was administered by nebulisation 30 min before exercise and frusemide (1 mg/kg bwt; n = 6) was given in the same manner 2 h before exercise. Albuterol sulphate (360 and 720 microg; n = 7) were administered with a metered dose inhaler 2 h before exercise. Each drug was investigated independently of the others using cross-over protocols. Horses completed incremental exercise tests and oxygen consumption, carbon dioxide production, arterial blood gases, heart rate and measures of breathing mechanics including total pulmonary resistance (RL) and nasopharyngeal resistance (RU) were determined for each exercise intensity. The resistance of the lower airways was calculated subsequently from the difference between RL and RU. None of the drugs tested had an effect on any of the variables measured, possibly because maximal bronchodilation is stimulated in healthy horses by the normal sympathoadrenergic response to exercise. Therefore, the pre-exercise inhalation of a bronchodilator by a healthy horse is unlikely to improve performance capacity.     

Effect of season and temperature on mortality in amphibians due to chytridiomycosis

OBJECTIVE: To investigate the distribution and incidence of chytridiomycosis in eastern Australian frogs and to examine the effects of temperature on this disease. DESIGN: A pathological survey and a transmission experiment were conducted. PROCEDURE: Diagnostic pathology examinations were performed on free-living and captive, ill and dead amphibians collected opportunistically from eastern Australia between October 1993 and December 2000. We conducted a transmission experiment in the laboratory to investigate the effects of temperature: eight great barred frogs (Mixophyes fasciolatus) exposed to zoospores of Batrachochytrium dendrobatidis and six unexposed frogs were housed individually in each of three rooms held at 17 degrees C, 23 degrees C and 27 degrees C. RESULTS: Chytridiomycosis was the cause of death or morbidity for 133 (55.2%) of 241 free-living amphibians and for 66 (58.4%) of 113 captive amphibians. This disease occurred in 34 amphibian species, was widespread around the eastern seaboard of Australia and affected amphibians in a variety of habitats at high and low altitudes on or between the Great Dividing Range and the coast. The incidence of chytridiomycosis was higher in winter, with 53% of wild frogs from Queensland and New South Wales dying in July and August. Other diseases were much less common and were detected mostly in spring and summer. In experimental infections, lower temperatures enhanced the pathogenicity of B. dendrobatidis in M. fasciolatus. All 16 frogs exposed to B. dendrobatidis at 17 degrees C and 23 degrees C died, whereas 4 of 8 frogs exposed at 27 degrees C survived. However, the time until death for the frogs that died at 27 degrees C was shorter than at the lower temperatures. Infections in survivors were eliminated by 98 days. CONCLUSION: Chytridiomycosis is a major cause of mortality in free-living and captive amphibians in Australia and mortality rate increases at lower temperatures.     

Our professional responsibilities relative to human-animal interactions

An interesting area with great potential for benefiting and enriching the lives and conditions of people and animals is opening to us in research, service and teaching. By working with colleagues in other disciplines, we can develop new and creative ways to realize the great promise inherent in people-animal interactions properly studied and utilized.

Veterinarians who understand that a strong human-companion animal bond can augment people's mental and physical states will help develop sound and effective companion animal programs for individuals who are lonely or handicapped and for persons in the school systems of the community, as well as its hospices, nursing and convalescent homes, prisons and other institutions. Children experiencing the deep satisfaction of interacting with animals while young will more likely become responsible pet owners and advocates as adults. The image of the profession is enhanced when children and adults see veterinarians as concerned teachers and compassionate health professionals.

We as professionals will be required not only to update our knowledge and skills, but to acquire new knowledge in fields of animal and human behavior, psychology and sociology. We are needed on interdisciplinary research teams to study human-animal interactions. We will also be asked to commit time and personal energies in community programs, sometimes with no remuneration. But if skilled health professionals like veterinarians do not take the lead in establishing sound, long-term companion animal programs in their own communities, everyone will suffer including the animals. How we, as individual professionals, respond will be an important reflection of our compassion and our humanity.

     

Comparison of the recovery of Mycobacterium bovis isolates using the BACTEC MGIT 960 system, BACTEC 460 system, and Middlebrook 7H10 and 7H11 solid media.

The BACTEC Microbacteria Growth Indicator Tube (MGIT) 960 system was evaluated to determine how it compares with the BACTEC 460 radiometric system and solid media for recovery of Mycobacterium bovis from tissue samples. A total of 506 bovine lymph node samples were collected from abattoirs in the United States and Mexico between November 2003 and September 2004. Processed samples were inoculated into an MGIT 960 tube, BACTEC 460 vial, and Middlebrook 7H10 and Middlebrook 7H11 solid media. Ziehl-Neelsen slides were prepared to check for contaminants and confirm the presence of acid-fast positive bacilli. Samples containing acid-fast bacilli were confirmed as members of the Mycobacterium tuberculosis complex by a nucleic acid assay. Niacin and nitrate biochemical tests were used to distinguish M. bovis from M. tuberculosis isolates. Statistical analyses were performed to compare recovery rate, mean time to detection, contamination rates, as well as pair-wise comparisons in each category. The results showed that the MGIT 960 system had a higher recovery rate of M. bovis (122/129) than did the BACTEC 460 (102/129) and solid media system (96/129). The average time to detection was 15.8 days for the MGIT 960 system, 28.2 days for the BACTEC 460 system, and 43.4 days for solid media. Contamination rates were 6.9% for the MGIT 960 system, 3.4% for the BACTEC 460 system, and 21.7% for solid media. These results indicate the MGIT 960 system can be used as an alternative to the BACTEC 460 system for recovering M. bovis from tissue samples.     

Efficacy of spheroplastic and cell-wall competent vaccines for Mycobacterium avium subsp. paratuberculosis in experimentally-challenged baby goats

A Mycobacterium avium subspecies paratuberculosis (MAP) vaccine that reduced the incidence of clinical disease or reduced fecal shedding of MAP would aid control of Johne's disease (JD). The objective of the present study was to evaluate the efficacy of four MAP vaccine combinations, including cell-wall competent (CWC) alum adjuvant, CWC-QS21 adjuvant, cell-wall deficient (CWD) alum adjuvant and CWD-QS21 adjuvant vaccines. Eighty baby goats were vaccinated at 1 and 4 weeks of age with one of these vaccines or a sham control vaccine consisting of alum adjuvant. Kids were challenged orally with approximately 6.0 × 10⁹ organisms in four divided doses of 1.5 × 10⁹ organisms using a goat isolate of MAP. Vaccinated challenged and challenged control groups had 10 and 6 kids per group, respectively. Half of the kids within each group were necropsied at either 6 or 9 months post-challenge. Gross and microscopic lesions and relative number of acid-fast bacilli were evaluated and scored at necropsy. Results indicated all challenged kids had some lesions compatible with JD suggesting none of the vaccines prevented infection. Three vaccines (CWC-alum, CWC-QS21 and CWD-QS21) reduced lesion scores by 46–51% at 9 months. CWD-alum vaccine resulted in a more severe (+33.5%) lesion score than sham-vaccinated challenged control. Lesion scores were greater at 9 months than at 6 months post-challenge in the sham-vaccinated challenged group and CWD-alum vaccinated group, while lesion scores were generally stable with remaining vaccines. Mean fecal CFU/g were significantly different across time from challenge to 9-month necropsy (p = 0.043) and the CWC-QS21 vaccine group had a marked reduction in fecal CFU/g at all time points post-challenge. A reduction in MAP CFU/g was also detected in necropsy tissues from kids given the CWC-alum, CWC-QS21 and CWD-QS21 vaccines, and increased CFU/g were detected in tissues from kids given the CWD-alum vaccine. Immunological tests evaluated included, humoral response evaluation by AGID, ELISA and Western blot, and cell mediated response by comparative PPD skin testing (M. avium, Old Johnin, M. bovis and Lot 2 Johnin PPD's), and production of MAP induced γ-interferon. Vaccination also resulted in false-positive PPD skin test reactions for M. avium PPD, Old Johnin PPD and γ-interferon tests. When a 2-mm cutoff above normal skin thickness was used to define positive skin test reactions, false-positive reactions for M. bovis were detected in only 2 of 32 kids given a vaccine with QS21 adjuvant.     

Effects of trimethoprim-sulfadiazine on tear production and the fluctuations of Schirmer tear test values in horses

The objectives of this study were to observe the effects of trimethoprim-sulfadiazine on equine tear production and to determine normal fluctuations in Schirmer tear test (STT) values in horses. A randomized, placebo-controlled, blinded clinical trial measuring STT values in 15 horses over an 8-week period was performed. The treatment group (eight horses) received 30 mg/kg trimethoprim-sulfadiazine orally once a day and the control group (seven horses) received placebo (flour) at the same time. All horses were housed outdoors throughout the study. Schirmer tear test values were measured at 0, 2, 4, 6 and 8 weeks, and 4 weeks after discontinuation of treatment. There were no significant differences in tear production between the treated and control groups. Fluctuations in STT were observed and may result from individual and environmental variations. Trimethoprim-sulfadiazine did not decrease tear production in the horses in this study. Horses normally experience periodic fluctuations in STT values.