Factors influencing enlargement rate of small abdominal aortic aneurysms.

The purpose of this study was to determine the factors influencing enlargement rate of small abdominal aortic aneurysms. Fifty-seven high-risk patients with asymptomatic abdominal aortic aneurysms initially measuring 3.5 to 5.9 cm in the largest transverse diameter were followed with serial echographic measurements for 6 to 78 months (mean 24). The mean enlargement rate (MER) and the occurrence of sudden change in size (SCS) for each aneurysm were correlated to 23 variables. MER ranged from 0 to 1.8 cm/year (mean 0.48). During the study period 17 aneurysms showed SCS. The results of univariate analysis indicated that 8 variables were statistically correlated to the degree of MER and 5 to the occurrence of SCS. A multiple regression model was generated by stepwise regression analysis and demonstrated that 2 variables were independent predictors of the degree of MER: (1) the absence of distal arterial occlusive disease and (2) the ratio of the diameter of the aneurysm to that of the aorta (RD). The overall model P value was less than 0.001. A statistically valid multiple regression model to predict the occurrence of SCS was not feasible (P = 1.0). We conclude that the occurrence of SCS of small abdominal aortic aneurysms is often unpredictable and that the RD rather than the value of the aneurysmal diameter per se must be considered in selecting high-risk patients for echographic follow-up.

Response of broiler chickens to addition of zinc bacitracin to diets containing salinomycin and roxarsone.

Five trials were conducted at various locations to determine the response of broiler chickens to the addition of zinc bacitracin to diets containing both salinomycin and roxarsone. Results indicate that when a combination of salinomycin and roxarsone is used as an anticoccidial, the addition of zinc bacitracin at 33 or 55 mg/kg diet will improve growth rate and feed utilization by broiler chickens. Regression of body weight and feed utilization on dietary levels of zinc bacitracin indicated that each milligram of zinc bacitracin in the diet increased the 49-day weight of broiler chickens by .92 g and reduced the feed required per gram of gain by .0012 g.

The response of broiler chickens to the addition of bacitracin methylene disalicylate to diets containing salinomycin and roxarsone.

Two experiments were conducted to evaluate the response of broiler chickens to addition of bacitracin methylene disalicylate (BMD) to diets containing salinomycin. In each experiment, five tests were conducted at different locations. In Experiment 1, all diets contained 66 mg salinomycin/kg of diet for the first 42 days and either 0 or 33 mg BMD/kg of diet for the entire 49-day feeding period. In Experiment 2, all diets contained 66 mg salinomycin and 50 mg roxarsone/kg of diet for the first 42 days and either 0, 11, 33, or 55 mg BMD/kg of diet for the entire 49-day feeding period. In Experiment 1, addition of 33 mg BMD/kg of diet significantly (P less than .05) improved body weights and feed utilization. Results were similar in all five tests. In Experiment 2, addition of 11, 33, or 55 mg BMD/kg of diet significantly (P less than .05) increased body weights. In one location the addition of 55 mg BMD/kg of diet resulted in no significant difference in body weight compared with those fed the unsupplemented diet, but in all other locations the response was similar. Addition of 33 or 55 mg BMD/kg of diet resulted in improved (P less than .05) feed utilization when all tests were combined. Feed utilization was not improved in all locations by the addition of BMD.