Masters Theses

Date of Award

8-1966

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

C. S. Hobbs

Committee Members

H. J. Smith, James M. Anderson

Abstract

Performance testing is important in the beef cattle industry as an aid to selection for improvement. It is an excellent means for evaluating the genotypic and phenotypic worth of an animal. Since the sire transmits one-half of the genetic material of each calf, an estimate of the genetic potential of each sirs should be made prior to selection if optimum genetic progress is to be accomplished. Despite the need for choosing a herd sire with a reliable performance record, there is still little information in the literature relating to methods of developing beef breeding bulls. Most per-formance testing programs for beef bulls have been progeny tests. These are useful in predicting a bull's prepotency but are time con-suming and expensive. Most post-weaning performance tests for beef cattle have emphasized that the best way to evaluate the gaining and feed utilizing ability of an animal is to feed a maximum of concentrate for a period of 140 days or some similar period. This type of test has been used as one of the criteria for the selection of breeding stock. Ruminant animals have the unique ability of converting low cost roughages, with the assistance of rumen microorganisms, into a wholesome, nutritious human food. Since roughages are a natural food for beef cattle, it is more economical and practical to feed high levels of roughages to beef animals for development and maintenance. There may be times when high levels of concentrates are desirable, such as a finishing period for slaughter animals, yet this is only a short span in the lifetime of an animal. To obtain more data on methods of developing bulls and consider-ing the foregoing facts, a comparison of methods of developing bulls was initiated by the Animal Husbandry-Veterinary Science Department at the University of Tennessee. In an earlier report, Anderson (1962) concluded that the most desirable program of those tested for developing bulls was: 1. A 140-day wintering period in which the basic ration con-sisted of a full feed of corn silage, 2 lb. of alfalfa hay and 5.5 lb. of concentrate per head per day. 2. A pasture period of approximately 90 days during which time the bulls were allowed to consume an average of approximately 1 lb. of concentrate per 100 lb. of body weight daily in addition to pasture. 3. A 98-day full-feed period. This was designated as the BA system of developing bulls. In a later report, Knapka (1963) compared the BA system with one designated as the CA system. The CA system differed from the BA system only in that during the 140-day wintering period 2.5 lb. of concentrates were fed instead of 5.5 lb. Throughout the three periods the bulls on the BA system had an average daily gain of 1.92 lb. as compared to 1.82 lb. for the bulls on the CA system. The lifetime average daily gain, type grade and con-dition grade were slightly higher for the bulls on the BA system, but there was no significant difference between treatment groups for the entire test period. Because the bulls on the CA system obtained a greater percentage of their nutrients from less expensive roughages during the winter period, the feed cost per head was $11.40 less for the bulls on the CA system than for those on the BA system. The main disadvantage of these two systems compared to a 140-day full-feed test is the higher feed, labor and handling cost resulting from the extended length of time on test. Also, there is some delay in obtaining the complete data on a bull, which could result in consid-erable retardation of genetic progress. The objectives of this thesis are to compare bulls developed on the BA system with those developed on the CA system and to relate their performance from birth to weaning with their post-weaning per-formance .

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