It makes a difference when you feed hay to a soon-to-be-calving beef herd, and each year Glenn Selk reminds us of this fact.

Selk, an emeritus animal science professor at Oklahoma State University, notes in a recent Cow/Calf Corner newsletter that supervision of the calving herd pays dividends in the form of live calves delivered and reduced calf mortality, especially for first-calf heifers.

Supervision during daylight hours is a whole lot easier than it is at 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,” says Selk.

Studies on rumen motility have shown a decline in rumen contractions within hours of parturition. Selk explains that intraruminal pressure falls the last two weeks of gestation, with a rapid drop during calving. By feeding at night, it’s thought that intraruminal pressures are more apt to rise at night and decline in the daytime.

Canadian rancher Gus Konefal made this observation back in the 1970s, and the relationship between hay-feeding time and calving time has spawned a number of research studies. Selk describes one such Canadian trial on 104 Hereford cows. In the study, 38.4 percent of a group fed at 8:00 a.m. and again at 3:00 p.m. delivered calves during the day, whereas 79.6 percent of a group fed at 11:00 a.m. and 9:00 p.m. actually calved during daylight hours.

A more substantial study was conducted on 1,331 cows across 15 Iowa farms. Fed once daily at dusk, 85 percent of the calves were born between 6 a.m. and 6 p.m.

Selk also points to research conducted by researchers at the Kansas State University Agricultural Research Center in Hays, Kan. In this study, scientists spent five consecutive years recording the time of calving (to the nearest half hour) of their herd of spring-calving, crossbred cows. Forage sorghum hay was fed daily between 4 p.m. and 6 p.m. The results were as follows:

“It is interesting to note that 85 percent of the calves were born between 6 a.m. and 6 p.m.," Selk says. “This is very similar to Iowa data when cows were fed at dusk.”

This data also revealed that most of the herd typically calved within three hours of their times from previous years. Selk concludes that feeding forage in the early evening undoubtedly influenced the number of cows calving in the daylight hours.

“Records 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.,” Selk adds.

For operations that offer this round-the-clock feeding, Selk suggests putting round bales and ring feeders inside a fenced enclosure. Producers can then provide access at dusk and throughout the evening before moving them to an adjacent pasture the following morning.

Although evening feeding may not eliminate checking heifers at night, Selk suggests it should translate to more live calves on the ground.