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This paper is a validation of the Species Composition Index (SCI). The SCI is a data-handling technique which expresses the botanical composition of a sward as a vector. Inclusion of these vectors allows the incorporation, in response models, of the dynamic changes in species composition of sods which occur over time. The SCI was developed originally with a data set which was obtained in a beef (Bos taurus L.) steer 3-year experiment where several dependent variables (forage growth, consumption and animal performance) were measured concurrently with several environmental, plant and animal characteristics. The SCI was then validated with a different data set, obtained over another 3-year period, with the same species combined in different ways and more complex treatments. The SCI was related to the effects, if significant, of year, season, grazing pressure, forage quality, precipitation and air temperature on the dependent variables in the two data sets independently. The SCI was superior to the traditional classification variable ‘treatments’ in accounting for variation in the dependent variables in both data sets. When ‘treatments’ was entered into the model, coefficients of determination of 0·26, 0·43, 0·58 and 0·44 were obtained for forage growth and consumption, average daily gain and beef production with the first data set, and of 0·13, 0·40, 0·36 and 0·37 in the second data set, respectively; when SCI was used, coefficients increased to 0·40, 0·52, 0·68, 0·55, 0·42, 0·61, 0·58 and 0·58, respectively. Thus, the effectiveness of the SCI was similar in the two data sets and the SCI appears to be a useful tool for quantitatively describing dynamically changing sward compositions.

Summary The growth-promoting effect of aureomycin added to a calf ration which provided 15 to 20% of body weight daily of milk and a milk replacement mixture for the first 30 days was determined with 28 Jersey and 35 Holstein calves. The average gains of the aureomycin-fed calves exceeded those of the control calves during the milk feeding period as well as after weaning, but the differences were not statistically significant because of the wide variations in gains within each group. These results indicate that on a liberal milk feeding regime for calves growth stimulation due to aureomycin will not be attained consistently.

Summary Sixty-two pairs (33 Jersey and 29 Holstein pairs) of milking cows were used to compare aureomycin supplementation with a control ration for a 12-wk. period. Treated cows were fed at the rate of 10mg. per 100lb. body weight. Seventeen pairs were continued on the experiment for 17 wk. and another eight pairs for 6 mo. The differences between the two groups of cows in milk production and body weight changes were not significant at the 5% level. The cows receiving aureomycin showed no obvious advantage in resistance to mastitis, foot rot, or other bacterial disturbances throughout the study.