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Protein Source and Level for Incoming Feedlot Cattle^1,2,

Texas Tech University, Lubbock 79409

Abstract

Three experiments, each lasting 28 d, were conducted to evaluate the effects of protein source and level on performance of incoming feeder cattle (avg wt 236 kg; n = 960). In Exp. 1 and 2, supplemental CP sources were urea, cottonseed meal (CSM) and a 50:50 mixture (CP basis) of blood meal:corn gluten meal (BM-CGM). Protein sources were added to achieve diet CP levels of 10.5 and 12.5% (DM basis). In Exp. 3, CP treatments (12.5%) were urea, urea .67/BM-CGM .33, urea .33/BM-CGM .67 and BM-CGM (CP basis). No interactions existed between protein source and level for any variable measured. In Exp. 1, the BM-CGM combination produced superior (P < .03) rate and efficiency of gain to either urea or CSM alone. In Exp. 2, BM-CGM supplemented cattle had more rapid ADG and were more efficient (P < .02) than urea-fed cattle, but values were not different (P = .18) from those supplemented with CSM. In Exp. 1 and 2, both gain and feed intake were greater (P < .05) for cattle fed 12.5 than for those fed 10.5% CP diets. In Exp. 3, ADG and gain efficiency increased linearly (P < .001) with increasing BM-CGM proportion. Feed intake also tended to increase (P = .17) with the addition of BM-CGM. Our results indicate that incoming feed-lot cattle for the first 28 d should receive a diet containing at least 12.5% CP and that at least 60% of the total dietary protein should be high-quality rumen escape protein. This advantage for the rumen escape protein was lost during the subsequent month.

¹ Approved for publication by the Dean of Agric. Sci., Texas Tech Univ., as publication no. T-5-242. Funds were provided in part by the Thornton Endowment, Texas Tech Univ. The authors acknowledge the staff of the Burnett Center for Beef Cattle Research for the care and feeding of the cattle.

² Reference to a company or trade name does not imply approval or endorsement by Texas Tech Univ.

³ Current address: Dept. of Anim. Sci., Univ. of Arizona, Tucson 85721.

⁴ Dept. of Anim. Sci.

⁵ For reprints.

⁶ Current address: Garden City Exp. Sta., Kansas State Univ. Garden City 67846.

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