Date of Award:

1984

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Advisor/Chair:

Norris J. Stenquist

Abstract

A feeding trial was conducted comparing four finishing diets, typically fed in this area, two hormone implants zeranol (Ralgro) and estradiol 17-beta (compudose), and a feed additive. thirty-two Hereford steers were fed in individual pens to maintain accurate intake records. The four diets compared were: 1) a whole corn diet with a small amount of corn silage as roughage; 2) a high energy ground barley diet using corn silage and chopped alfalfa as roughage; 3) a total diet consisting of rolled barley, beet pulp, and ground alfalfa hay; and 4) a high energy rolled barley diet using corn silage and chopped alfalfa hay as roughage. All finishing diets were supplemented with a protein, vitamin, and mineral supplement containing monensin.

The cattle were fed in two phases--a growing and finishing phase. The diet comparisons were conducted only during the finishing phase. The implant and additive comparisons were made over both phases.

Diet had little effect on feed lot performance. Rate of gain and feed efficiency were not significantly affected. Voluntary intake of net energy for gain was significantly affected (p<.01) by diet. Cattle fed diet #1 consumed significantly more net energy for gain than cattle on diets #2, 3, and 4.

The effect of diet was also significant for internal fat percent and marbling score (p<.05). Cattle fed diet #2 had the highest internal fat percent (3.06%) followed by those on diets #3 (2.6%), diet #1 (2.3%), and diet #4 (2.1%). Marbling scores were similar with cattle on diet #2 showing significantly higher (p%lt;.05) marbling scores than the other three groups. No other carcass characteristics were affected.

The difference between the implants used was very small. None of the feedlot performance traits were affected.

The feed additive Trigrr II produced significantly more (p<.05) efficient gains during the growing period. This efficiency was apparent during the finishing period. Average daily gains were significantly higher for Trigrr II fed cattle (p<.05).

During the combined period, average daily gain and feed efficiency were both superior for Trigrr II fed cattle (p<.05). Ribeye and hot carcass weights were significantly affected also (p.01). Cattle fed Trigrr II were superior in this case.

Cattle implanted with zeranol fed Trigrr II consumed significantly greater amounts of net energy for gain and had heavier hot carcass weights than estradiol 17-beta implanted cattle or zeranol x control cattle.

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