Introduction 

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. 
At the time of early weaning, all calves should be vaccinated for blackleg and malignant edema.  Consult your veterinarian for other suggested vaccinations.  If it is possible to administer vaccinations a couple of weeks prior to weaning, Pasteurella vaccine may also be considered.  It is probably a good idea to vaccinate two weeks prior to early weaning anyway because immunity will be established by weaning time and calves will not be subjected to the added stress associated with vaccines, injections and handling at weaning time.  All calves not intended for breeding replacements should be implanted. 
Calves should be first placed in a small pen with some type of shelter available.  Small pens are preferred over larger lots because large lots or traps encourage fence walking and make it more difficult for calves to find feed and water.  The feed bunk and water source need to be easily accessible and recognizable. 
Previously, the OSU early weaning program utilized three weaning rations starting with a high concentrate ration for the first few days when feed intake is very low.  More research has shown that performance is better when a single ration is used throughout.  This also makes management of the program much easier.  The ration used is shown in Table 1. 

Table 1. Ration Fed to Early Weaned Calves. 
 
Ingredients Percent (as fed basis) 
 
Cottonseed hulls                30.0 
Corn, rolled or ground       46.3 
Cane molasses                     4.0 
Soybean meal                    18.0 
Calcium carbonate               1.9 
Dicalcium phosphate             .45 
Salt                                      .30 
Vitamin A (30,000 IU/gm)   1 lb/ton 
Coccidiostat recommended dosage 
 

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 calves. 
Consumption of the ration should reach 4-5 lb within a day or two.  Afterward, consumption should range from 3 to 3.5 percent of body weight on an "as fed" basis.  A coccidiostat has been included in the ration shown in Table 4.  Coccidiosis is always a threat when dealing with stressed, confined calves.  The choice of coccidiostat will depend on the situation and preference of the veterinarian.  The ionophores, Rumensin, and Bovatec, are also good coccidiostats and should be fed for coccidiosis as well as for growth promotion and improved feed efficiency.  Label restrictions for calf weight need to be observed for any feed additive. 

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. 
In order to reduce feed purchases, many producers may wish to move early-weaned calves to pasture after the calves have reached an average weight of 250-300 in drylot.  OSU research indicated that gains of early-weaned calves run on native pasture from late July (with grain supplementation) were lower than for calves raised completely in drylot.  High quality forage such as wheat pasture will likely be required to get good gains on light-weight, early-weaned calves. 
All roughage fed to early-weaned calves should be mixed in desired portions in a complete ration.  When free-choice hay is available, some calves may consume mostly hay which provides protein, minerals and energy.  By increasing the roughage level of the complete rations as the calves get bigger and thus increasing their daily ration intake, the correct levels of protein, energy and minerals can be "metered" into the calves. 

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. 
As expected, heifers and cows whose calves were weaned early were heavier at normal weighing time than were those cows and heifers that raised calves.  Since these cows are in better condition, they will require less supplemental feed during the following winter.  This factor will need to be considered in the budgeting of an early weaning program. 
 

Table 2.  Effects of Early Weaning on Cow and Heifer Performance. 
 
                              1st-Calf Heifers           Mature Cows 
 
                              Normal        Early          Normal         Early 
                              Weaned      Weaned      Weaned      Weaned 
 
Weight, lbs 
at early weaning            698              680           816            832 
at end of breeding         746              753           922            968 
at normal weaning time  788              875           920          1040 
Conception rate, %         59                97             83            100 
Days from calving to 
first estrus                       90.5             73              81             46 
 
 

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.