This section could probably be titled "What to Do If All Else Fails". Certainly no one ever plans to find himself with a group of cows too thin to breed. It does happen, however, and early weaning of calves at six to eight weeks of age is an effective way to get high rebreeding rates, even in very thin cows. Although early weaning is certainly not advocated for all producers all of the time, it can provide an attractive alternative in certain situations such as drought, when large amounts of purchased forage would be necessary to maintain a cow herd through to normal weaning time or when cows are already too thin to rebreed. Studies at OSU show that early-weaned calves can be efficiently raised to a normal weaning weight with minimal labor and facilities. The procedure used at OSU is outlined here.
Why Early Weaning Works
Lactation roughly doubles the daily energy and protein requirement for a typical beef cow. Removing the calf at six to eight weeks into lactation obviously reduces the quantity and quality of forage needed to maintain the cow herd. Reasons for improved rebreeding after early weaning involve more than nutrition, however. Research has shown that the removal of the nursing calf causes hormonal changes in the cows that stimulate estrus. Estrus activity can then be induced in cows too thin to cycle while still suckling a calf.
Age for Early Weaning
In order to maintain a 365 day calving interval, calves should be early weaned at less than 80 days of age. About 40 days of age may be a practical minimum for early weaning in beef herds. Calves at least 40 days old do not require milk replacers in the ration and are old enough to eat dry feed. Since smaller and younger calves may have difficulty competing for feed and water, the age range in any given group of early-weaned calves should be kept as narrow as possible.
Managing the Early Weaned Calf
The procedures described in this section were developed from three studies conducted at the Range Cow Research Center at Oklahoma State University. Two studies were conducted with spring-born calves early weaned in April and May while the third study involved fall-born calves early weaned in December. A total of 64 calves were early weaned in these studies.
The most critical time is the first two weeks after early
weaning. Calves must overcome the stress of weaning and learn to
eat feed very quickly. However, with good management to reduce
stress and to provide palatable feed, early weaning is not as risky as
might first be feared.
Table 1. Ration Fed to Early Weaned Calves.
The ration is high in both energy and protein. Cottonseed hulls
are used as the sole roughage source because they are extremely
palatable. If chopped hay is substituted for cottonseed hulls,
molasses should be added to minimize dust. Avoid alfalfa pellets
because calves tend to sort them from the concentrate portion of the
ration, a problem that can lead to acidosis if too much concentrate is
eaten. Soybean meal is preferred over cottonseed meal for young
Expected Calf Performance
Daily gains of commercial Hereford and Hereford X Angus calves have
averaged about 1.75 lbs/day from 6-8 weeks of age to 205 days of
age. These calves consumed about 9 lbs of feed during the early
weaning period, with a feed conversion of 4.5 lbs of dry matter per
pound of gain. Weaning weights (205 days steer equivalent) for
early-weaned calves were 435 lbs, compared to 347 lbs for calves raised
by their dams on summer bermuda pasture. The calves weighed an
average of 155 lbs at the time of early weaning. Performance of
early-weaned calves compared to pasture reared calves will depend on the
growth potential of the calves, the level of milk production of the dams
and the level of management.
Expected Improvements in Cow Performance
Table 2 shows weight gain and rebreeding improvements for first-calf
Hereford heifers and mature cows that had their calves early weaned at
6-8 weeks of age. Early weaning increased conception rates of very
thin first-calf heifers from 50 percent to 97 percent and shortened the
days to first estrus by 17 days. The mature cows were judged to be
in moderate condition. All the early weaned cows rebred; while
only 81 percent of the cows that raised calves rebred. Many of the
cows cycled within three days of early weaning, indicating that extra
bull power may be needed for a few days following early weaning.
Table 2. Effects of Early Weaning on Cow and Heifer
The most likely place for early weaning is in a situation where poor conception rates are expected. Depending on concentrate and hay prices, early weaning might be profitable when large amounts of hay must be purchased for a cow. Producers should substitute their own feed costs as appropriate in this budget.
Summary of Early Weaning Concepts
Calves can be successfully weaned at 6-8 weeks of age and efficiently
raised to a normal weaning weight in drylot. Early weaning will
permit high conception rates and rapid rebreeding. While early
weaning is certainly not recommended as standard practice, it should be
useful in times of drought when purchased feed may be more efficiently
fed directly to the calf than to the lactating cow. Early weaning
may also offer cattlemen a chance to achieve high conception rates in
cows too thin to rebreed otherwise. Ranchers that observe heats
closely, (i.e. those doing A.I.) will notice that a large percentage of
cows "early weaned" will have short (10 - 12 day) first estrous cycles
after the weaning process. Subsequent cycles are normal.
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