Obtaining an accurate measure of birth weight using a high-quality digital scale is important for producing meaningful calving ease EPDs. However, it is not always feasible to obtain birth weights this way. Digital scales for measuring calf birth weights can cost thousands of dollars. Even with good mechanical scales, trying to catch a calf when the mother is being protective, and lifting that calf, are challenges for many producers and their ranch hands. There are reports of producers estimating the calf weights using visual inspection and this can be seen in many breed association birth weight datasets.
A widely used alternative to weighing or estimating birth weight is the calf hoof tape method. A google search reveals that there are many vendors of calf hoof tape devices. They are relatively low cost and simple to use. Many breeders producing large numbers of calves have indicated that they use hoof tapes. Large contemporary groups of calves are especially challenging, and obtaining an observation on all animals is not always feasible, especially in spring calving herds in the northern states and Canada. While it has been shown that the variance of hoof tape estimated birth weights is substantially smaller than actual birth weights, using a hoof tape may be a pragmatic alternative when obtaining actual birth weights is not feasible, and it should be superior to visual estimates. However, while some studies have shown a favorable relationship between birth weight and hoof tape measures, at least one study has shown a poor relationship.
The correlation of a hoof tape measurement to actual birth weight can be high. While it is possible to model hoof tape observations as a separate but correlated trait, as of this writing, no breed associations have required members to indicate if the weights were predicted by hoof tape measurement. However, given the noticeably reduced variance within contemporary group, it is possible to identify many of these groups when they are larger. It is recommended that a heterogeneous variance procedure be implemented in the EPD production where birth weight is modeled.
BIF recommends that organizations responsible for receiving performance data and conducting genetic evaluations require breeders to indicate if they have used a hoof tape measurement to predict birth weight.
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