On most ranching operations, supervision of the first-calf heifers will be best accomplished in daylight hours, and the poorest observation takes place in the middle of the night.
The easiest and most practical method of inhibiting nighttime calving at present is by feeding cows at night. The physiological mechanism is unknown, but some hormonal effect may be involved. 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.
The concept is called the Konefal method. A Canadian rancher, Gus Konefal, reported his observations in the 1970s.
In a follow-up Canadian study of 104 Hereford cows, 38.4 percent of a group fed at 8 a.m. and again at 3 p.m. delivered calves during the day, whereas 79.6 percent of a group fed at 11 a.m. and 9 p.m. In a more convincing study, 1,331 cows on 15 farms in Iowa were fed once daily at dusk; 85 percent of the calves were born between 6 a.m. and 6 p.m.
Kansas State University scientists recorded data on five consecutive years in a herd of spring-calving crossbred cows at the Kansas State University Agricultural Research Center at Hays, Kansas. They recorded the time of calving (to within the nearest one-half hour).
Births that could not be estimated within an hour of occurrence were excluded. Cows were fed forage sorghum hay daily between 4 and 6 p.m. For statistical purposes, the day was divided into four-hour periods:
Between 6 and 10 a.m., 34.23 percent of the calves were born;
Between 10 a.m. and 2 p.m., 21.23 percent of the calves were born;
Between 2 and 6 p.m. 29.83 percent of the calves were born;
Between 6 and 10 p.m., 8.41 percent of the calves were born;
Between 10 p.m. and 2 a.m., 4.4 percent of the calves were born; and
Between 2 and 6 a.m., 1.91 percent of the calves were born.
It is interesting to note that 85.28 percent of the calves were born between 6 a.m. and 6 p.m. This is very similar to Iowa data when cows were fed at dusk.
These data also revealed that for a majority of animals in the herd, the time of calving was within three hours of the average time of day that cow had previously given birth. Feeding forage in the early evening hours undoubtedly influenced the percentage of cows calving in daylight hours.
Many cow-calf producers put large round bales in ring feeders and leave them out for round-the-clock feeding for cows. Records here at Oklahoma State University indicated that when cows had constant access to large round bales but were fed supplements at about 5 p.m., 70 percent of the calves were delivered between 6 a.m. and 6 p.m.
Some producers choose to put the big round bales and the ring feeders inside a fenced enclosure. The gates to the hay-feeding enclosure are opened at dusk and the cows are allowed access to the hay in the evening and overnight hours, then they are moved to another adjacent pasture the following morning. Anecdotal reports have indicated that this method has the desired results with a higher percentage of calves born in the daylight. 
PHOTO: Staff photo.
Glenn Selk is an emeritus extension animal scientist with Oklahoma State University. Email Glenn Selk.
—Excerpts from Cow/Calf Corner newsletter, Oklahoma Cooperative Extension Service, Jan. 1, 2018
