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Non-Randomness of Variations in Daily Weights of Cattle

University of California

Abstract

Statistical analyses are presented for 69 consecutive daily weighings of 8 head of yearling cattle. During the first half of the period the animals had free access to feed and water and were weighed at 11:20 a.m.; during the last half, water was shut off at 7:00 p.m. and the cattle weighed before feeding at 6:45 a.m. The analyses confirm the report of Maymone and Sircana (1930) that cyclic variations may occur in the day-to-day deviations of cattle weights. On the basis of the data presented three daily weights of 14 animals would be required to obtain the accuracy assumed for 3 daily weights, independent in a probability sense, for 10 animals.

Some correlation was shown to exist between deviations of the various animals due to environmental conditions. When the animals were allowed free access to water and the weighings were made near mid-day, the deviations in daily weights were positively correlated with daily temperature range. When the animals were without feed and water at night and the weights taken early in the morning, no significant correlation between deviations in daily weights and daily temperature range was found.

These findings indicate that in feeding trials an adequate fore period for adjustment is necessary and that environmental effects can be lessened by weighing at the same time of day and by using shrunk weights. The shrunk weights of the second period did not interfere with feeding or rate of gain, and gave weights that were less variable and more consistent with selling weights. The findings also indicate that a relatively greater increase in accuracy results from using more animals in each group in an experiment than from increasing the number of weights obtained per animal.

¹ Junior Statistician in the Experiment Station, Davis, Calif.

² Associate Professor of Animal Husbandry and Associate Animal Husbandman in the Experiment Station, Davis, Calif.