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| 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 cattle with larger birth weights. 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 2 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. In a Canadian study of 104 Hereford cows 38.4% of a group fed at 8:00 am and again at 3:00 pm delivered calves during the day, vs 79.6% of a group fed at 11:00 am and 9:00 pm. A British study utilizing 162 cattle on 4 farms compared the percentages of calves born from 5:00 am to 10:00 pm to cows fed at different times. When cattle were fed at 9:00 am, 57% of the calves were born during the day, vs 79% with feeding at 10:00 pm. In field trials by cattlemen utilizing night feeding when 35 cows and heifers were fed once daily between 5:00 pm and 7:00 pm, 74.5% of the calves were born between 5:00 am and 5:00 pm. In the most convincing study to date, 1331 cows on 15 farms in Iowa were fed once daily at dusk, 85% of the calves were born between 6:00 am and 6:00 pm. Whether cows were started on the night feeding the week before calving started in the herd or 2 to 3 weeks earlier made no apparent difference in calving time. On many large ranches, it is physically impossible
to feed all of the cows after 5:00 pm. In those instances, the ranch
manager should plan to feed the mature
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cows earlier in the day, then feed the first
calf heifers at dusk. The heifers, of course, are the group of females
that are of greatest need of observation during the calving season.
Various means have been employed to effectively reduce animal loss at calving time. Skilled personnel should be available to render obstetric assistance and neonatal care to maximize profits in the cattle operation. Currently, evening feeding of cattle seems to be the most effective method of scheduling parturition so assistance can be available during daylight hours. The next issue facing the rancher at calving time, is the amount of time heifers or cows are allowed to be in labor before assistance is given. Traditional text books, fact sheets and magazine articles stated that “Stage 2” of labor lasted from 2 to 4 hours. “Stage 2” is defined as that portion of the birthing process from the first appearance of the water bag until the baby calf is delivered. Newer data from Oklahoma State University and the USDA experiment station at Miles City, Montana clearly show that Stage 2 is much shorter, lasting approximately 60 minutes in first calf heifers, and 30 minutes in mature cows. In these studies, heifers that were in stage 2 of labor much more than one hour or cows that were in stage 2 much more than 30 minutes definitely needed assistance. Research information also shows that calves from prolonged deliveries are weaker and more disease prone, even if born alive. In addition, cows or heifers with prolonged deliveries return to heat later and are less likely to be bred for the next calf crop. Most ranches develop heifers fully, and use calving ease bulls to prevent calving difficulties. However, a few difficult births are going to occur each calving season. Using the concept of evening feeding to get more heifers calving in daylight, and giving assistance early will save a few more calves, and result in healthier more productive two-year cows to rebreed next year. |