An Analysis of Body Condition Scores, Ultrasonographic Fat Thickness, and the Interaction Between the Two on Conception Rates in Yearling Cross-Bred Heifers

Cary Crow

Date of Graduation

Fall 1999

Degree

Master of Natural and Applied Science in Agriculture

Department

College of Agriculture

Committee Chair

Thomas Perkins

Abstract

One hundred Branvieh cross heifers ranging from 13-17 months of age were used in an analysis of conception rates through three estrous cycles. Cattle were estrus synchronized and artificially inseminated through two estrous cycles then pasture exposed to reproductively sound Branvieh bulls. Body condition scores (BCS), ultrasonographic fat thickness (UFT), ultrasonographic percent intramuscular fat (UPF), weight per day of age (WDA), weight (WT), and artificial insemination technician (AI) were all used in assessing conception rates. No variable was correlated to pregnancy diagnosis (PD). Stepwise linear regression analysis with maximum R² using all six traits produced a very low R² value (.07). A correlation was found between BCS and UFT (.36). Also, UFT and UPF were correlated to one another (.30). Low first service conception rates (28%-50%) could possibly be contributed to the inexperience of technicians used in heat detection and artificial insemination. Other variability associated with the BCS technician could describe the apparent inaccuracy and unusually high values of BCS in this group of heifers. Heavier conditioned cattle, as assessed by ultrasonographic fat thickness, had higher overall conception rates. Significant difference was realized between UFT1 (<32cm) and UFT3 (<.55cm) with overall conception rates of 68% and 95% respectively. Cattle with BCS 7 tended to have higher overall conception rates, numerically but not statistically, than their thinner conditioned and heavier conditioned counterparts. No determination could be made as to which method of body composition analysis, BCS or UFT, better assessed conception rates.

Subject Categories

Agriculture

Copyright

© Cary Crow

Citation-only

Dissertation/Thesis

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