(Producer Questions prior to 2009)
What should I consider when selecting replacement heifers?
As you are well aware, the process of selecting replacement heifers in very important in a commercial cow/calf operation. These females represent the future factory. Because puberty is related weight, it is important that weaning weight be part of your selection criteria. To start, I would suggest culling the upper 1% of the heaviest and lightest 25%. The heaviest heifers at weaning may represent big, high growth heifers that may not fit your environment. Make the selection on actual weaning weight because that's the weight you will be using to develop a feeding program so that they reach puberty (about 2/3 of their mature weight) before the start of the breeding season. Then make selections on conformation (body type, feet and legs) and apparent disposition. Of the heifers that are remaining, I then look at their dam.
If their mother is old, meaning she has been part of my herd for many years, this is a heifer that I really consider keeping because her mother has been a productive part of my herd for many years and therefore must be adapted to the environment (forage resources, management, etc.). I would expect similar performance from her offspring.
I have read about free-martins when a heifer calf is born twin to a bull. Does that mean that if both twins are female, will their future reproduction be OK?
Future reproduction of twins that are both heifers should not be compromised. When a heifer calf is born twin to a bull, there is an exchange blood of the heifer and bull in the uterus, because the bull produces testosterone, the testosterone causes some problems in the early development of the female reproductive axis.
What are the benefits of feeding bred heifers in the evening rather than feeding in the morning during calving season?
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 Dr. Glenn Selk, Oklahoma State University. Rumen motility studies indicate the frequency of rumen contractions fall 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 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.