Talk:Hoof Tape
WMS
This page, and references LaShell et al [2], Parish et al[3], and Pruit et al [5] are focused on relationships between hoof circumference (or birth wt projected from hoof circumference) and scale-measured birth weight. Shouldn't we be looking at relationships between hoof circumference and calving ease? What are phenotypic and genetic correlations between hoof circumference and calving ease - is hoof circumference a decent indicator of calving ease?
Toser et al. developed a model to predict calving difficulty, first predicting birth weight from hoof circumference, then predicting dystocia from birth weight and pelvic width. They show hoof circumference increased with calving difficulty score, but standard deviations around the mean circumference for each score overlap. Presumably Ko & Ruble [1] show something similar but I cannot find a copy of that paper.
Pruit et al. reported a "poor" correlation between hoof circumference and birth wt (R^2 = 0.46) that is near the ballpark of other estimates (R^2 ~ 0.57 to 0.78). Their mean circumference is larger (18.9 cm) than means reported in other work (around 17.5 cm), and the tape they used is apparently different than the widely used Calfscale tape. They used a tape calibrated at 10 lb per cm, the CalfScale tape uses 11 lb/cm for heifers and 12.2 lb/cm for bull calves. They also allude to research showing birth wt is a better predictor of calving difficulty than other body measurements, but do not cite that research.
Colburn et al. (1997) found a 0.52 phenotypic correlation between hoof circumference and calving difficulty, slightly weaker than their 0.57 correlation between birth wt and calving difficulty. The correlations are a bit curious - mean birth wt increased with calving difficulty and means were significantly different for each category. Mean hoof size bounced around - hard pulls had the numerically smallest feet, not statistically different from easier pulls or unassisted calves. C-sections and easy pulls had the largest feet, different than unassisted. Sires ranked the same by birth wt EPD and calf foot size (lightest EPD/smallest feet ... heaviest EPD/largest feet). The high birth wt EPD/big foot bull also had the most calving difficulty - incidence, mean score, c-section rate. These results suggest hoof circumference might be a useful indicator, but genetic correlation estimates among calving ease, hoof circumference and birth wt are needed to incorporate hoof circumference into calving ease EPD. For this, hoof circumference should be reported as hoof circumference (in cm), not a projected birth weight corresponding to the circumference measurement. Reporting hoof circumference will avoid issues related to different tapes implementing different regression equations to project birth wt, or inadvertently reading birth wt from the wrong side of the Calfscale tape, which has different scales for heifer and bull calves.
Birth weights projected from hoof circumference may be useful to adjust weaning wt to 205 d. While the tape "weights" might be off (light calves overestimated, heavy calves underestimated), those weights may be closer to actual birth weight than an assumed standard birth weight used in 205 d adjustment when birth weight is missing.
BLG
Good comments from WMS. The papers I was able to dig up are pretty weak.
I think understanding the relationship between hoof tape and CE is potentially useful. However, from my cleanest data, I got a genetic correlation (with very large numbers of observations) between hoof-tape and actual birthweight at >.92. If this is correct then I feel that, after accounting for the heterogeneous variance, hoof tape data should be included as birth weight observations. A big if there right now.
In the near term, we need to try to make a recommendation about identifying future records submitted using hoof tape. That should be pretty easy. Also, in the near term, we should try to make a recommendation about identifying existing hoof tape observations and accounting for them. My approach of using the DNN to identify them and then use a heterogeneous variance procedure my not be ideal, but it is better than what has been happening?
In the longer term I think we need to provide guidelines on how new technologies are evaluated. Perhaps we could get BIF to provide funding to someone to collect data with the clear objectives of identifying hoof tape's relationship to not only BW but also CE.
