Thursday, July 11, 2019

An Update on Using a Heart Girth
Tape for Estimating Calf Weights

It is useful to have estimates of heifer calf weights. In the absence of animal scales it has been established that the heart girth measurement is a reasonably accurate way to estimate body weights. Various tape designs have been used over time - 1936, 1961 and 1992. Heinrichs comments on the need for verifying the tape designs, 
"Whereas the body weight and heart girth relationship has been reliable over time, the regression equation to estimate body weight and heart girth have changed, ... most likely due to alterations in breeding and selection programs that have affected animal conformation, in additional to other traits, over time."

Thus, it was judged to time to reassess the accuracy of the 1992 design. Based on 1,498 measurements from 586 animals the authors compared heart girth with scale weights. The correlation between the actual and predicted body weight was 0.98. 

"Upon comparing the previously developed hearth girth to body weight equation with 2 independent data sets, we concluded that the previous equation converting heart girth to body weight for Holstein dairy heifers (Heinrichs, 1992) remains valid for the current genetics and type of Holstein dairy heifers."

Keep using the tape you have for Holstein dairy calves. Remember to place the tape correctly around the calf right behind the front legs. Pull tightly enough to compress hair coat but not to stretch the tape. 

Reference: Heinrichs, A. J., B.S. Heinrichs, C. M. Jones, P.S. Erickson, K.F. Kalscheur, T.D. Nennich, B.J. Heins and F.C. Cardosoll "Short Communication: Verifying Holstein heifer heart girth to body weight prediction equations." Journal of Dairy Science 100:8451-8454 (2017)

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