What can you conclude if calves suckle before leaving the calving pen?
1. Except under unusually clean conditions calves received a substantial dose of E. coli bacteria before and during their first few swallows of colostrum when they begin suckling. If you can tell which teats the calf nursed (they are very clean) you can be more certain this is true.
2. Since calves have to stand and begin walking in order to suckle, you can assume that suckling on teats is probably not all that happened. For example, sucking on the dam's brisket and flanks (remember all the little balls of manure on the hair in those places?). These sites are very productive sources of fecal coliform bacteria associated with persistent scours between 7 and 14 days of age.
3. Many calf care persons will be uncertain about how much additional colostrum to feed the newborn calf. The most common response is to not feed any more colostrum.
It is possible to estimate gut fill fairly accurately by feeling of the calf's belly. Using four quarts of warm colostrum and an esophageal tube feeder feed this amount to several calves that have not suckled. Before feeding, with the calf standing with her head against your belly slide your hands back over her rib cage until they reach her belly. Now, with your hands around her belly, estimate gut fill level.
Feed the calf. Repeat the gut fill palpation - note how much change has taken place. Repeat with another calf. After a few calves your hands will have quite a good sense of the difference between the "not-fed-calf" and the "full-calf."
If a calf has had an opportunity to suckle be sure to check her out - how full is she? Then make an educated guess how much more colostrum to feed.