By Glenn Selk, Oklahoma State University Emeritus Extension
An issue facing the rancher at calving time, is the amount of time heifers or cows are allowed to be in labor before assistance is given. Traditional text books, fact sheets and magazine articles stated that “Stage II” of labor lasted from 2 to 4 hours. “Stage II” is defined as that portion of the birthing process from the first appearance of the water bag until the baby calf is delivered. Research data from Oklahoma State University and the USDA experiment station at Miles City, Montana clearly show that Stage II is much shorter, lasting approximately 60 minutes in first calf heifers, and 30 minutes in mature cows.
Table 1. Research Results of Length of Stage II of Parturition
|Source||No. of Animals||Length of Stage II|
|USDA (Doornbos, et al.1984. JAS:59:1)||24 mature cows||22.5 minutes|
|USDA (Doornbos, et al.1984. JAS:59:1)||32 first calf heifers||54.1 minutes|
|Oklahoma State Univ. (Putnam, et al. 1985. Therio:24:385)||32 first calf heifers||55.0 minutes|
In these studies, heifers that were in stage II of labor much more than one hour or cows that were in stage II much more than 30 minutes definitely needed assistance. Research information also shows that calves from prolonged deliveries are weaker and more disease prone, even if born alive. In addition, cows or heifers with prolonged deliveries return to heat later and are less likely to be bred for the next calf crop. Consequently a good rule of thumb: “If the heifer is not making significant progress 1 hour after the water bag or feet appear, examine the heifer to see if you can provide assistance. Mature cows should be watched for only 30 minutes before a rectal examine is conducted.” Make certain the cervix is completely dilated before pulling on the chains. If you cannot safely deliver the calf yourself at this time, call your local large animal veterinarian immediately.
Most ranches develop heifers fully, and use calving ease bulls to prevent calving difficulties. However, a few difficult births are going to occur each calving season. Using the concept of evening feeding to get more heifers calving in daylight, and giving assistance early will save a few more calves, and result in healthier more productive two-year cows to rebreed next year.