EVALUATION OF HOOF CIRCUMFERENCE TO PREDICT BIRTH WEIGHT
R. J. Pruitt(1),
K. VanderWal(2), and M. Britt(3)
Department of Animal and Range Sciences
CATTLE 95-16
Summary
Records from 81 calves showed that hoof circumference is an unreliable predictor of birth weight. A hoof tape predicted only 25.9% of birth weights within 2 lb of actual birth weight. For 29.6% of the calves the error in predicting birth weight was over 10 lb.
Key Words: Hoof Circumference, Birth Weight, Calves
Introduction
Birth weights and Expected Progeny Differences (EPDs) calculated from birth weights are important bull selection tools to reduce the risk of excessive calving difficulty. For convenience, hoof tapes are sometimes used as a method to estimate birth weights in place of weighing calves with a scale. Due to questions about the accuracy of hoof tapes, we evaluated the accuracy of hoof circumference compared to birth weights measured with a scale.
Materials and Methods
Records from 81 Angus, Simmental, and Angus-Simmental crossbred bull and heifer calves born in 1995 at the SDSU Cow-Calf Teaching and Research Unit were analyzed (Table 1). Within 24 hours of birth, calves were weighed with a hanging spring scale and hoof circumference was measured with a commercially available flexible hoof tape. Hoof circumference was measured on a front foot at the hairline. The tape was marked in centimeters on one side and calibrated on the other side to estimate birth weight based on the second equation in Table 2.
A linear prediction equation was calculated with hoof circumference used as the independent variable and actual birth weight measured with a scale used as the dependent variable.
Results and Discussion
The calculated prediction equation is similar to the calibration on the hoof tape (Table 3). The low R2 (.46) indicates hoof circumference does a poor job of predicting birth weight. The hoof tape predicted only 25.9% of the birth weights within 2 lb. The error in predicting birth weight was over 10 lb for 29.6% of the calves. Using the prediction equation that we calculated did not improve the accuracy of using hoof circumference to estimate birth weight.
This information shows that hoof circumference is not a reliable method to estimate birth weight. It is sometimes reasoned that hoof circumference could be a better indicator of potential calving difficulty than birth weight. However, several research projects have failed to show any body measurements of newborn calves that can predict calving difficulty as accurately as birth weight.
| Table 1. Data used to calculate prediction equation | ||
| Hoof circumference, cm | Actual birth weight, lb | |
| No. calves | 81 | 81 |
| Mean | 18.9 | 88.3 |
| Standard deviation | .9 | 12.6 |
| Minimum | 16.0 | 58.0 |
| Maximum | 20.8 | 118.0 |
| Table 2. Equations to predict birth weight (lb) from hoof circumference (cm) | |||||
| Intercept | Standard error | Slope | Standard error | R2 | |
| Calculated prediction equation | -90.9 | 9.27 | 9.48 | 1.15 | .46 |
| Calibration on hoof tape | -100.0 | -- | 10.0 | -- | -- |
| Table 3. Error in estimating birth weight from hoof circumference | ||
| Based on tape reading | Based on calculated prediction equation | |
| Range in error, lb | -19.0 to 21.0 | -19.8 to 19.4 |
| Distribution of error, % | ||
| Less than 2 lb | 25.9 | 21.0 |
| 2.1-5.0 lb | 17.3 | 19.8 |
| 5.1-10 lb | 27.2 | 28.4 |
| Greater than 10 lb | 29.6 | 30.9 |
1. Associate Professor.
2. Cow/Calf Unit Manager.
3. Former Senior Ag Research Technician.
Back to 1995 Beef Report Index
Modified: December 03, 1997