This article could probably be titled "What to Do If All Else Fails." Certainly no one ever plans to find himself in a drought, short of forage, and with a group of cows too thin to breed.
It does happen, however, and early weaning of calves at 6-8 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 cowherd through to normal weaning time or when cows are already too thin to rebreed. Studies at Oklahoma State University show that early-weaned calves can be efficiently raised to a normal weaning weight with minimal labor and facilities.
Why early weaning works
Lactation roughly doubles the daily energy and protein requirement for a typical beef cow. Removing the calf at 6-8 weeks into lactation obviously reduces the quantity and quality of forage needed to maintain the cowherd.
Reasons for improved rebreeding after early weaning involve more than nutrition, however. Research shows removal of the nursing calf, and therefore the removal of stimuli of the nerves in the udder, causes hormonal changes in the cows that allow estrus cycles to begin. Estrus activity can then be induced in cows too thin to cycle.
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 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. It’s 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 or destined to “all-natural” programs could 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.
Example rations for early-weaned calves can be found in the Oklahoma State University Fact Sheet ANSI-3031, “Nutrition and Management Considerations for Preconditioning Home Raised Beef Calves.” Look specifically at Table 3 in this fact sheet.
Expect improvements in cow performance
Research shows early weaning increased conception rates of very thin first-calf heifers from 50% to 97% 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% 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 should require less supplemental feed during the following winter. This factor will need to be considered in the budgeting of an early-weaning program.