Summary and Implications
Estrus activity in virgin heifers tends to affect the outcome in measurements observed during performance and feed utilization tests. Prior to any testing it is prudent to identify those females that have shown estrus activity consistently and those which have not, then evaluate animals for feed efficiency grouped by stage of sexual maturity.
Iowa State University
Dahlke, Garland R. and Gunn, Patrick J.
"Effect of Estrus Activity when Evaluating Feed Efficiency in Heifers,"
Animal Industry Report:
AS 661, ASL R2944.
Available at: http://lib.dr.iastate.edu/ans_air/vol661/iss1/7