Multiple-step melting in two-dimensional hexatic liquid-crystal films

An unexpected three-stage melting transition has been observed in two-dimensional (2D) free-standing liquid-crystal films by in situ electron-diffraction and optical-reflectivity measurements. These data suggest the existence of two phases between the 2D solid and liquid: a hexatic phase and, at a higher temperature, an intermediate liquid phase with hexatic-like positional correlations ( approximately 40 angstroms) but no long-range orientational order. Previous high-resolution heat-capacity measurements have revealed a divergent-like anomaly at the hexatic-liquid transition that sharply contradicts the predictions of 2D melting theories. The observation of an intermediate isotropic phase may alter our understanding of 2D melting and lead to reconciliation between current experiments and theories.     

Mesenteric strangulation by pedunculated lipomas without involvement of associated intestine in four horses

An unusual form of strangulation of mesentery only by pedunculated lipoma was identified as the cause of moderate to severe colic in four horses. The small intestinal mesentery was involved in three horses and the small colon mesentery in the fourth horse, but the associated intestine was not strangulated, haemorrhagic, nor obviously obstructed in any horse. In all horses, a patch of haemorrhagic mesentery of variable size was evident around the origin of a mesenteric lipoma and a major mesenteric vessel. One horse was subjected to euthanasia at the owner's request and the remaining three had surgery from which they made a complete recovery after the removal of the lipoma. Intestinal resection was not performed in any of the three horses undergoing surgery. An isolated mesenteric strangulation by lipoma is an uncommon cause of colic in older horses that have the typical presentation of a strangulating lipoma. The removal of the involved lipoma without mesenteric or intestinal resection can be associated with complete recovery.     

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group. In Study 1 and in the combined analysis, the initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) higher in the oxytetracycline group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, third UF relapse, overall chronicity, overall rail, overall mortality, bovine respiratory disease (BRD) mortality, hemophilosis mortality, arthritis mortality, or miscellaneous mortality rates between the experimental groups in either study or in the combined analysis. In addition, there were no significant (P > or = 0.05) differences in initial weight, final weight, weight gain, days on feed, daily dry matter intake, average daily gain, or the dry matter intake to gain ratio between the experimental groups in either study or in the combined analyses. In the economic analysis, there was a net economic advantage of $5.22 CDN per animal in the oxytetracycline group, due to a lower prophylactic cost, even though the UF therapeutic cost was higher.     

Incidence rate of musculoskeletal injuries and determinants of time to recovery in young Australian Thoroughbred racehorses

Objective To describe the incidence rate of musculoskeletal (MS) injuries and investigate the factors that influence recovery from MS injury in young Thoroughbred horses in Australia. Methods Training and injury data were collected at fortnightly intervals from 14 trainers in New South Wales. Incidence rates were calculated for initial injuries stratified by age‐class and sex. Survival analysis methods were used to investigate the time to recovery after the first MS injury (measured as a start in a race or barrier trial). Results For the 248 racehorses enrolled, there were 428 injuries recorded; 2‐year‐olds were 2.99‐fold more likely than 3‐year‐olds to sustain an MS injury. The cumulative percentage of horses that had recovered within 6 months was 55%. The time to recovery was longest in horses whose fast gallop speed prior to injury was < 890 m/min. Conclusion This study supports the finding that shin soreness is the most common MS injury in young Australian Thoroughbreds. There was an increased rate of MS injury in 2‐year‐olds compared with 3‐year‐olds. However, it was impossible to determine if the increased risk in 2‐year‐olds was related to age, the start of training or a combination of both. The study also found that horses performing at higher exercise speeds prior to injury were more likely to recover. There was a significant effect of trainer, suggesting that other factors related to trainer may influence the time to the recovery. Additional research is required to understand the determinants of time to recovery.