Evaluating relationships among performance traits and body measurements in bulls from different preweaning management systems

"Use of performance testing programs in developing sound breeding and selection programs is well established. However, the shift of the 70's to larger framed, later maturing cattle has raised questions as to proper testing procedures. Still, emphasis on visual appraisal to define these maturity patterns has been less than objective and far from concrete in its persuasiveness. Economic belt tightening has necessitated identification and use of only those animals which can optimize growth and efficiency. Animal breeding and selection programs have never before had the opportunity to be so effective. The need for reliable bull evaluation is clear. Past genetic studies confining appraisal to only a few select measurements over constant chronological time periods have neglected many aspects of growth and development. Research indicates a more justifiable evaluation would occur at the same physiological age or the same maturity point. With efficiency of production as an utmost concern to the commercial producer performance evaluation procedures should be given careful consideration. Also of concern to the commercial producer and feeder is marketing animals that have been fed to a choice grade. This also indicates testing programs should be evaluating bulls at a maturity endpoint rather than a constant age. Researchers have used linear body measurements to study interrela­ tionships among weights and other measures of growth. Their results indicate body measurements can be useful in indentifying larger bulls with the potential for high gains. High testing costs as well as problems arising from a too-high concentrate ration are concerns of producers entering bulls on 140- or 160-day feed tests. Recent work (Brown et al., 1979; Johnson et al., 1980) advocates a partial or 84-day testing program. Opponents argue partial test figures would be biased by preweaning management. Further investigations are needed to determine if body measurements would be useful in defining maturity patterns that would remove the bias of pre-weaning management effects. This research was undertaken with the following objectives in mind: (1) to study how preweaning management affects growth during performance test, (2) to investigate relationships among performance traits and actual body measurements, (3) to determine if performance testing bulls for 84 days can be used to evaluate bulls as they would be ranked after 140 days on test."--Introduction.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Animal husbandry (MU)

Grantor dc:publisher

University of Missouri--Columbia

Year dc:date.issued

1982

Author dc:creator

• Sloan, Jeri Lynn

Advisor dc:contributor.advisor

• Morrow, Ron E.

Statement dc:rights

• OpenAccess.

Language dc:language.iso

eng, English

DOI

https://doi.org/10.32469/10355/103546

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/103546