Table 1. Average Daily Gains of Weanling Beef Calves Receiving Three Anti-
 biotics by Sex and Year of Study (Ibs.).

 Sex of Calves Male Female Combined
 Treatment Year 1 Year 2 Year 1 Year 2 Year 1 Year 2

 Control 0.86 0.84 0.93 0.76 0.90 0.80
 Aureonycin 1.01 0.87 0.93 0.69 0.97 0.79
 Terramycin 0.92 0.85 0.82 0.72 0.87 0.79
 Oleandomycin 0.80 1.02 0.77 0.76 0.78 0.90

 Combined 0.90 0.90 0.86 0.73 0.88 0.82


 The data was combined from each of the two trials by antibiotic treat-
 ment groups. Sexes were exactly equal in number in each antibiotic group
 when years were combined as there were 12 steer and 13 heifer calves per
 treatment group in the first year and 13 steer and 12 heifer calves in the
 second year. This is 25 calves, of each sex, for each treatment group. On
 an overall basis, the average daily gains for calves in the control group
 was 0.85 pound compared to 0.88, 0.83 and 0.84 pounds for the calves re-
 .* giving aureomycin, terranycin and oleandomycin, respectively. Thus gains
 among the antibiotic treatments were similar.

 The analysis of variance showed that differences in gain between year
and rations were not statistically significant; However differences in gains
between steer and heifer calves were significant at the 1% level of signifi-
cance. Interactions between year, treatment and sex were all statistically
significant because the largest gains were not produced by the same antibiotic
treatment in each of the two years. Furthermore, differences between the
two sexes were not significant in the first year but were highly significant
for the second year, when analysed on an within year basis.

 The average initial market slaughter grade for all calves (both years)
was a medium standard and the average grades dropped to a low standard at
the end of the trial. In the first trial, the greatest decrease in grade
occurred in the control and oleandomycin supplemented groups while the calves
in the aureomycin group of the second trial showed the greatest decrease in
market grades (Table 2). None of the experimental groups showed average de-
creases of more than two thirds of a market grade. This decline in slaughter
grade appears to be a normal reaction during the life of a beef calf when it
is changing from veal to beef. The full-feeding of concentrates would tend
to diminish this decline in grade. The antibiotics apparently did not in-
fluence the slaughter grade changes occurring in this study. (Slaughter
grade was used as a measurement because it is dependent upon the condition
and degree of fleshing, hence it is an indicator of the health and thrifti-
ness of an animal). Therefore, the antibiotics did not improve the health
of the calves.