It is generally accepted that adequate supervision at calving has a significant impact on reducing calf mortality. Adequate supervision has been of increasing importance with  the use of larger beef breeds and cattlewith larger birthweights. Oklahoma State University beef specialist Glenn Selk, PhD, points out that on most ranching operations, supervision of the first-calf heifers will be best accomplished in daylight hours. The easiest and most practical method of inhibiting nighttime calving is by feeding cows at night. Rumen motility studies indicate the frequency of rumen contractions falls a few hours before parturition. Intraruminal pressure begins to fall in the last two weeks of gestation, with a more rapid decline during calving. It has been suggested that night feeding causes intraruminal pressures to rise at night and decline in the daytime, Selk says. In field trials by cattlemen utilizing night feeding when 35 cows and heifers were fed once daily between 5:00 p.m. and 7:00 p.m., 74.5 percent of the calves were born between 5:00 a.m. and 5:00 p.m. In the most convincing study to date, in which 1,331 cows on 15 farms in Iowa were fed once daily at dusk, 85 percent of the calves were born between 6:00 a.m. and 6:00 p.m. Whether cows were started on the night feeding the week before calving started in the herd or two to three  weeks earlier made no apparent differencein calving time. On many large ranches, it is physically impossible to feed all of the cows after 5:00 p.m. In those instances, the ranch manager should plan to feed the first-calf heifers at dusk. Various means have been employed to effectively reduce animal loss at calving time. Currently, evening feeding of cattle seems to be the most effective method of scheduling parturition so assistance can be available during daylight hours.