The errors associated with estimations of the reproductive efficiency of bulls based on non-return data

Three statistical methods - multiple and linear regression, and analysis of variance - were used to interpret the data in this study. The results of a preliminary study indicated that there were several major sources of variation in the non-returns of bulls. These were seasonal differences, possible breed differences, and differences between bulls within a breed. In addition, there were differences in breeds in different seasons. Upon consideration of these data a regression study of 33 bulls was undertaken to ascertain the degree of relationship between the changes in the early and late non-returns to first services. Statistically, it was found that when both the 60-90 day and 30-60 day non-returns are available, the latter are of little practical value in predicting the changes in the 150-180 day non-returns. When only the 30-60 day figures are available they may be used with reasonable accuracy to “estimate” the final changes in the 150-180 day non-returns. An analysis of variance of the errors of estimate from the regression studies indicated that there are several assignable causes of variation in non-return estimates. These include differences between breeds as to the effect of season on reproductive efficiency, differences between bulls within a breed, and a significant difference in seasonal effect in different stations. The use of non-return data in estimating the reproductive efficiency of a bull is of value only when all factors that affect this reproductive efficiency are considered. This investigation shows the significance of some of the various factors to be considered.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Dairy Husbandry

Department dc:contributor.department

Dairy Husbandry

Grantor dc:publisher

Virginia Polytechnic Institute

Year dc:date.issued

1953

Author dc:creator

• Finkel, Peter William

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/53772

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/53772