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Management of Yearling Bulls in a Feedlot^1,2,

U.S. Department of Agriculture³ Clay Center, NE 68933

Abstract

Three experiments were conducted to identify points of managerial intervention into feeding protocols for yearling bulls. Effects of number of bulls/pen (group size), administration of tranquilizer at penning, length of feeding period and mixing at 13 mo of age were specific interest. Pens used for small groups (30 or 34 bulls) were 15.2 x 64.6 m with 15.2 m of bunk space; pens used for large groups (60 or 68 bulls) were 30.5 x 64.6 m with 30.5 m of bunk space. Thus, surface area and bunk space/bull were similar for both group sizes. In one experiment bulls fed in the smaller groups grew faster and were more efficient; in the other experiment the results were equivocal. The interaction of length of feeding period (56 or 112 d) with group size was not a significant contributor to the total variance. The tranquilizer, acepromozine, delayed the onset, but did not decrease the intensity, of agonistic behavior in bulls mixed at approximately 13 mo of age. Growth rate and feed efficiency did not differ between groups of bulls mixed first at approximately 13 mo and those in which a social order was established as a result of having been penned together for 7 mo prior to the initiation of the study. On a diet of moderate energy density (2.7 Meal ME/kg dry matter), growth rate and feed efficiency did not differ between 56-d and 112-d feeding periods.

¹ Cooperation of the Nebraska Agric. Exp. Sta.,Univ. of Nebraska-Lincoln is acknowledged. The assistance of Cattle Operations personnel in collection of the data is appreciated.

² Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable.

³ Roman L. Hruska U.S. Meat Anim. Res. Center, ARS, USDA, Clay Center, NE.