Whether you are just kicking-off the spring calving season or are right in the middle of calving-out heifers, you will have to decide how much time to give heifers and cows in labor before assisting. Traditional information says that Stage II labor lasts from 2 to 4 hours. Recent studies from Oklahoma State University and the United States Department of Agriculture experimental station at Miles City, Mont., show that Stage II should be much shorter and producers should intervene much sooner.

"Stage II"is defined as that portion in the birthing process from the first appearance of the water bag until the calf is delivered. In these studies, reported Glenn Selk, extension animal reproduction specialist at Oklahoma State University, heifers that were in Stage II much more that one hour, and cows much more than 30 minutes, needed assistance.

The timing of assistance has a considerable effect on calf health. Calves surviving a prolonged birth often suffer from respiratory acidosis and often fail to receive adequate passive immunity because of decreased colostrum intake and absorption. In addition, cows or heifers with prolonged deliveries return to estrus later and are less likely to conceive the next season.