Restriction endonuclease analysis of infectious laryngotracheitis viruses: comparison of modified-live vaccine viruses and North Carolina field isolates

Six modified-live (ML) infectious laryngotracheitis (ILT) vaccine viruses, three reference strains, and 18 field isolates were compared by restriction endonuclease analysis of their DNA. Viral DNA digestion patterns were established for vaccine viruses using restriction endonucleases PstI, BamHI, KpnI, and HindIII. Using these enzymes, five of six ML vaccine viruses had identical restriction endonuclease cleavage patterns. Vaccine viruses had distinct patterns compared with ILT virus reference strains Illinois-N71851, Cover, and NVSL. Restriction endonuclease cleavage patterns of 18 field isolates of ILT virus, obtained from ILT outbreaks in North Carolina, were indistinguishable from vaccine viruses. These results suggest a possible role of vaccine or vaccine-like viruses in recent ILT outbreaks.     

Experimental cryptosporidiosis and infectious bursal disease virus infection of specific-pathogen-free chickens

Specific-pathogen-free chickens orally inoculated at 4 days of age with a moderately pathogenic vaccine strain of infectious bursal disease virus (IBDV) and/or at 5 days of age with Cryptosporidium baileyi oocysts remained free of overt clinical signs throughout a 16-day period postinoculation (PI). The prepatency period for C. baileyi oocyst shedding was shorter in chickens receiving higher numbers of oocysts, but once shedding was detected, there were no obvious differences in shedding patterns among groups receiving 10(3) through 10(6) oocysts. On days 8 and 16 PI, cryptosporidia were located primarily in the bursae of Fabricius. IBDV exposure was associated with bursal follicle atrophy, whereas C. baileyi infection resulted in bursal epithelial hypertrophy and hyperplasia, mild follicle atrophy, and heterophil infiltration of the bursal mucosa. Examination of experimental groups of 30 birds each indicated that concurrent infection with both agents resulted in more severe bursal lesions, more infected birds, and greater numbers of cryptosporidia in infected tissues. At the termination of the trial, 16 days PI, Cryptosporidium infection was associated with a 6% decrease in mean body weight compared with controls.     

Respiratory mechanics of horses during stepwise treadmill exercise tests, and the effect of clenbuterol pretreatment on them

Normal Standardbred horses were given an incremental exercise test on a horizontal treadmill to evaluate the influence of exercise on gas exchange, resistance, dynamic compliance and inertance of the respiratory system. The exercise test consisted of 2 min exercise steps at each of the following speeds: 2.4 m/sec (walk), 4.5 m/sec (slow trot), 7.0 m/sec (fast trot) and 10 m/sec (gallop). At rest and after 1 min of exercise at each step, airflow, tidal volume, respiratory frequency, pharyngeal, mid-oesophageal and transdiaphragmatic pressures and arterial blood gas tensions were measured. The same horses were subsequently treated intravenously with clenbuterol (0.8 microgram/kg) and an identical exercise test and measurement performed 10 min after clenbuterol injection. In response to exercise, there were large increases in tidal volume, respiratory frequency, airflow and pressures. Exercise was associated with a decrease in upper airway resistance but total pulmonary resistance was unchanged. Exercise did not alter inertance or dynamic compliance, horses became hypoxaemic, and at 10 m/sec (galloping) also developed hypercarbia. Treatment with clenbuterol did not alter any of these measurements in response to exercise. These data suggest that dilation of upper airways occurs during exercise, and that inertial forces are important in strenuously exercising horses and may influence the accuracy of dynamic compliance determinations at high exercise intensities.     

Germplasm Variability and Environmental Effects on Stem Cellulose and Lignin Concentrations in Alfalfa*

Stem cellulose and lignin concentrations are major determining factors of alfalfa (Medicago sativa ssp. sativa L.) forage quality. Only limited information is available on the genetic variability and the influence of environmental effects on these two stem-quality traits. Our objectives were to: evaluate the variability for stem cellulose and lignin concentrations in modern alfalfa germplasms across several harvests; observe the environmental stability of these two quality traits in 32 alfalfa clones selected high or low for either stem cellulose or lignin concentration; and examine the relationships between these two stem-quality traits and leaf and stem crude protein (CP). Fifty alfalfa entries (cultivars and experimental populations) were established May 1993, and sampled for stem acid-detergent lignin (ADL), stem acid-detergent cellulose (ADC), and stem CP on Sep 1993, June and Aug 1994. Clones were vegetatively propagated from individual plants selected for extremes in stem ADL and ADC and transplanted into blocks at two locations in May 1994 and sampled for quality analysis in September 1994. For all samples, leaves were hand-separated from stems and stem ADL, ADC, CP and leaf CP concentration were determined using near infrared reflectance spectroscopy. Entry differences for stem ADL and ADC were detected only at the June 1994 harvest date in the cultivar study. Spearman's ranked correlations over years in the clonal study demonstrated greater environmental stability for stem ADC (r = 0.70, P ≥ 0.01) than for stem ADL (r = 0.54, P # 0.05). Environmental effects had an impact on both traits, but stem ADC showed greater potential for improving forage quality. Simple correlations showed that decreasing stem ADL or ADC would have minimal effect on leaf CP and may increase stem CP.     

Effect of cyclophosphamide on selected hematologic parameters of the turkey

The effect of three daily cyclophosphamide (CY) injections (doses of 0-100 mg/kg.day) on selected hematologic parameters in 7-to-8-week-old female Nicholas turkeys was examined. CY induced significant leukopenia, lymphopenia, thrombocytopenia, and heteropenia 24 to 72 hours after the initial injection; time depended on cell type and dose of CY. Significant linear correlation between increasing CY dose and increasing severity of circulating cell depression occurred. CY had no significant effect on circulating numbers of monocytes, packed cell volume, or plasma protein. Changes in basophils and eosinophils could not be identified because of their low numbers.     

Evaluation of an enzyme-linked immunosorbent assay for the detection of Mycoplasma hyopneumoniae antibody in porcine serum

An enzyme-linked immunosorbent assay (ELISA) for detecting antibody to Mycoplasma hyopneumoniae in porcine serum is described. The results are presented as an ELISA ratio, calculated by dividing the absorbance of the test sample by the mean absorbance of control negative sera. In known infected pigs, the ELISA ratio was highest when the serum concentration applied to the ELISA plate was diluted 1 in 20 in PBS - Tween. Mean ELISA ratios ranged from 1.2 +/- 0.3 for pigs without porcine enzootic pneumonia (PEP) lesions to 5.5 +/- 1.5 for pigs observed with a PEP lesion reacting positively with immunofluorescent histopathology. Pigs observed with typical PEP lesions at slaughter, but not confirmed by immunofluorescent histopathology had a mean ELISA ratio of 4.9 +/- 1.7. The ELISA was highly sensitive (95.6%) and specific (98.8%) when pig sera from commercial piggeries of known M hyopneumoniae infection status were assessed. No cross-reactivity with serum from a pig hyperimmunised with killed M flocculare was detected, and reactivity with serum from another pig hyperimmunised with killed M hyorhinis showed only weak cross-reactivity, which failed to reach the ELISA positive threshold (ELISA ratio 3) for M hyopneumoniae.     

The use of a shotgun for the emergency slaughter or euthanasia of large mature pigs

The isolated heads of a Friesian bull and three large, Large White pigs were shot from various aspects with a 12-gauge shotgun using both a single 28 g solid lead projectile and buckshot, the latter consisting of nine individual lead pellets with a combined mass of 28 g. The sites of impact to the skull included the conventional frontal region, an occipital site and immediately behind the ear. A live mature Large White sow was shot with buckshot in the depression just caudal to the right ear, resulting in immediate insensibility and death. The damage caused to the isolated heads indicated that similar effects could be expected if the heads had been part of intact living animals. It is suggested that buckshot (nine lead pellets with a combined mass of 28 g) fired from a 12-gauge shotgun may be suitable for the emergency slaughter or euthanasia of a wide variety of domestic livestock and other species of animal.     

The shelf‐life of uneviscerated and eviscerated chicken carcasses stored at 10°C and 4°C

1. Uneviscerated and eviscerated chicken carcasses were processed together and stored in groups of 10 at 10°C and 4°C; a further 10 eviscerated carcasses were wrapped in “polythene” bags and stored at 4°C.

2. The bacteriological condition of the uneviscerated and eviscerated carcasses prior to storage was very similar.

3. At 10 °C the eviscerated carcasses developed a slight “off” odour in 3 to 4 d (average 3.5 d) whilst the first signs of greening in the uneviscerated carcasses occurred in 4 to 6 d (average 5 d).

4. At 4 °C wrapped eviscerated carcasses developed slight “off” odour in 5 to 6 d (average 5.6 d) whilst the unwrapped eviscerated carcasses varied considerably in their shelf‐life from 5 to 11 d (average 7.9 d). After 18 d the uneviscerated carcasses were still quite acceptable and no bacteria were found in the breast muscle (i.e. < 150/g).

5. Bacteriological examinations made of the skin of the three groups of chickens stored at 4 °C confirmed the differences obtained in shelf‐life; Pseudomonas spp. were found to be the predominant spoilage organisms in each case.