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Influence of Variations in Ruminal Contents upon Estimates of Body Weight Change of Dairy Cattle during Restricted Feeding¹

Department of Animal Husbandry, University of California, Davis

ABSTRACT

Three common methods of estimating live weight change in ruminants and relationships between ruminal contents and live weights of dairy cattle were studied, using 13 lactating Holstein heifers, two with rumen fistulas. Live weights were obtained immediately after each milking for 105 consecutive days in one trial and 61 days in another. Ruminal contents from fistulated heifers were removed, weighed, sampled, and replaced periodically. Body weight changes estimated from single weighings after 14 hr without feed or water at the beginning and end of a period were shown to be more accurate than changes estimated either from means of three live weights taken at the beginning and end of a period, or from a regression of daily live weights on time. It was shown that estimation of body weight change from shrunk live weights could greatly reduce variations in ruminal fill, one of the largest sources of error in dairy cattle feeding experiments.

¹ These data are part of a thesis presented by the senior author to the University of California in partial fulfillment of the requirements for the Ph.D. degree.

² Present position: Extension Dairyman, University of California, Davis.