By Don Stotts, Oklahoma State University
It is generally accepted that adequate supervision at calving has a significant positive effect on reducing calf mortality, which has been of increasing importance with the use of larger beef breeds and cattle with larger birth weights.
"On most ranching operations, supervision of first-calf heifers and more mature cows will be best accomplished in daylight hours while the poorest observation typically will take place in the middle of the night," said Glenn Selk, Oklahoma State University Cooperative Extension emeritus cattle specialist.
The easiest and most practical method of inhibiting nighttime calving at present is by feeding the expectant mothers at night; the physiological mechanism is unknown, but some hormonal effect may be involved.
Selk said 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 nighttime feeding causes intraruminal pressures to rise at night and decline in the daytime," he said.
Studies. In a Canadian study of 104 Hereford cows, 38.4 percent were fed at 8 a.m. and again at 3 p.m. and delivered calves during the day.
A British study utilizing 162 cattle on four farms compared the percentages of calves born from 5 a.m. and 10 p.m. to cows fed at different times. When the cows were fed at 9 a.m., 57 percent of the calves were born during the day, compared to 79 percent for cows fed at 10 p.m.
"There are field trials by cattle producers utilizing nighttime feeding when 35 cows and heifers were fed once daily between 5 p.m. and 7 p.m.; 74.5 percent of the calves were born between 5 a.m. and 5 p.m.," Selk said.
In perhaps the most convincing study to date, more than 1,330 cows on 15 farms in Iowa were fed once daily at dusk, with 85 percent of the calves being born between 6 a.m. and 6 p.m.
"Whether cows were started on nighttime feeding the week before calving, started in the herd or started two weeks to three weeks earlier made no apparent difference in calving time," Selk said.
Various means have been employed to effectively reduce animal loss at calving time, and skilled personnel should be available to render obstetric assistance and neonatal care.
"Currently, evening feeding of cattle seems to be the most effective method of scheduling parturition so assistance can be available during daylight hours," Selk said.
Good management practices. Though it is always a sound management practice to observe all the females in a herd, typically the percentage of adult mature cows that need assistance at calving is extremely low compared to the percentage of first-calf heifers.
"That’s good news on a number of fronts, particularly because – on ranches with larger herds – it is pretty much physically impossible to feed all of the expectant mothers after 5 p.m.," Selk said. "In those instances, the ranch manager should plan to feed the mature cows earlier in the day, and then feed the first-calf heifers at dusk."