Dairy cows should be given a six-week dry or non-lactating period before calving. Cows due to calve have enlarged udders and relaxed pelvic ligaments and vulvas. They should be placed in a clean, well-bedded boxstall or in a clean pasture where they can be closely observed every few hours.

Once labor or birth begins, as noted by abdominal contractions, the heifer or cow should deliver the calf within half an hour to 3 hours. Heifers require a longer time for delivery than do cows. After a normal delivery (one in which the calf's head and forefeet come first as in 95 percent of births), the fetal membranes, placenta, or afterbirth is dropped in about 1 to 8 hours.

Once labor occurs, the calf should be progressively expelled. If this does not occur and the process is stalled, prompt assistance usually is indicated and a knowledgeable veterinarian or possibly a skilled, experienced layman is generally required. In small, poorly grown beef heifers, a cesarean operation or other operations may be required.

Hasty, ill-considered and improper traction on a calf not in the proper position should be avoided.

Following calving, it is essential the calf receives some colostrum or first milk within a few hours to give it the necessary immune antibodies to survive.

At or after calving, other serious problems requiring veterinary or skilled attention may occur. These include milk fever (hypocalcemia), retained placenta, and uterine infection, prolapse of the uterus, ketosis, mastitis, and displaced abomasum. These conditions are much more common and serious in dairy cattle than in beef cattle.

In a successful reproduction health program, cattle owners and breeders should strive for a 12 to 13 month calving interval, a 60 percent or higher first service conception rate, 1.6 to 1.8 services per conception, a range of 85 to 115 days open period post-calving, a less than 5 percent abortion rate, and less than 10 percent reproductive problem cattle.

To attain these goals requires careful, competent herd management by the owner or herdsman, the veterinarian and the inseminator (if the herd is bred by artificial insemination). The herd must also be free of contagious or infectious diseases, most commonly acquired by purchase of cattle from unknown or questionable sources.

Stephen Roberts, Professor Emeritus of Obstetrics, New York State College of Veterinary Medicine, Ithaca, is currently a private practitioner in Woodstock, Vt.