University of Nebraska Cooperative Extension MP 71

Summary

Angus crossbred yearling steers were started on a finishing program with diets stepped-up in grain over 23 days or with limit-feeding of the final diet over three weeks. Limit-feeding during start-up improved overall feed efficiency, carcass dressing percentage and fat thickness, but did not affect daily gain or carcass quality and yield grades. In this small pen research trial, steers reached ad libitum intake of the final diet by limit-feeding of this diet during start-up without major problems from acidosis or related intake variation.

Introduction

Traditionally, starting cattle on a finishing program involved using diets with increasing grain levels to allow the rumen microorganisms to gradually adjust to higher grain levels, attempting to minimize acidosis and intake variation that can occur with overeating of grain. Limit-feeding of high-grain diets throughout the finishing period has been used to improve feed efficiency, but little research has been done on limit-feeding of the final diet during the start-up period. Use of limit-feeding in the start-up period could eliminate higher roughage diets and get cattle adjusted to the final diet quickly without causing acidosis which can lead to severe intake variation or death.

The objective of our study was to compare feedlot performance and carcass traits of steers limit-fed the final diet during the start-up period to ad libitum feeding of traditional step-up diets of finishing cattle.

Procedure

Angus crossbred yearling steers averaging 845 pounds were randomly allotted to 12 pens of eight steers for a 123-day finishing trial. There were six pens assigned to each of two start-up treatments, which were: 1) ad libitum feeding of four step-up diets over 23 days with dry-rolled corn levels increasing from 45 to about 83 percent of diet dry matter and 2) limit-feeding of the final diet with programmed increases for about three weeks until steers reach ad libitum intake. The increases in energy in the step-up diets were accomplished by increasing corn by 10 percent for each step-up. Diets are shown in Table 1, with the final diet consisting of dry-rolled corn, corn silage and supplement. Steers limit-fed the final diet were initially fed 15 pounds of dry matter per day which was increased by 0.5 to 1 pound per day until they reached ad libitum intake of this diet in about three weeks. Steers were fed once a day.

Table 1. Step-up diets fed ad libitum and final diet limit-fed to yearling steers during start-up.

Steers were implanted with Synovex S at the start of the trial and were fed Rumensin/Tylan throughout the trial. They were weighed twice on succeeding days at the beginning of the trial. Final weights were calculated by dividing hot carcass weights by a common dressing percentage (62). Performance and carcass data were analyzed by using the GLM model of SAS. The start-up period was in late May and early June when temperature swings are usually not large and feed intake, along with cattle performance, tends to be more uniform.

Results

Daily gains were not different among treatments, but dry matter intake was lower (P = .06) and feed conversion improved (P < .01) for the steers limit-fed the high-grain diet initially (Table 2). Limit-fed steers also exhibited slightly higher dressing percentage and fat thickness than those started traditionally, but quality and yield grade comparisons were similar for the two start-up treatments. Results of this study suggest limit-feeding of high-grain diets could avoid the traditional use of higher roughage levels in step-up diets to bring yearling steers up to full-feed. However, the authors recognize that research pens with eight steers per pen and 20 feet of bunk space may improve the chances for successful start-up with limit-feeding of the final diet. Programmed increases of the final diet during start-up may be a faster method for adapting rumen microorganisms to grain levels that can often cause acidosis and intake variation when cattle approach full feed with diets stepped-up in grain.

Table 2. Performance of yearling steers for 123 days when step-up diets were compared to limit-feeding of the final diet during the first 23 days on feed.

Feed dry matter intakes by day are shown in Figure 1. Limit-feeding of the final diet during start-up did cause a drop in intake after day five for a couple days, but then gradual increases of less than 1 pound of dry matter per day after day seven resulted in ad libitum intake after two to three weeks. Conversely, the feeding of diets stepped-up in grain caused two intake drops during the first two weeks and a severe drop during week three. Intakes for both groups were similar by day 28 and remained similar for the remainder of the trial when all groups were fed the final diet ad libitum.

Figure 1. Feed intake variation by start-up method followed by ad libitum feeding to all steers.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.

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