Although the performance benefits of pre-weaning implants are well documented, many ranchers choose not to use them for various reasons. Some believe implanted calves are less desirable to buyers and bring lower bids at sale time; others might believe the benefits do not justify the extra labor and expense. According to University of Nebraska specialists, the benefits of calf implants vary based on genetics and environmental factors. In high-growth calves with good nutrition, implants can improve weaning weights by 5 to 10 percent, while calves with less genetic growth potential and more limited nutrition will not benefit as much. When using implants, consider timing with 80 to 100 days of duration. Calves implanted twice about 100 days apart typically will gain more than those given a single implant. If using a single implant, specialists recommend implanting at about 4 months of age to promote gains during the 100 days prior to weaning. University of Nebraska research has shown pre-weaning implants do not decrease calf performance or response to implants during the growing stage.

However, ranchers should consider several factors in implant decisions: • Marketing goals — Several branded beef programs or natural-beef programs prohibit the use of implants.

• Reproduct ion — Although research data provides mixed results of the reproductive consequences of implanting heifer calves, specialists generally recommend against implanting heifer calves intended as potential replacements in the breeding herd.

• Age limitations — Follow label specifications for the age at which to implant calves. Limited evidence supports the use of growth-promoting implants in calves less than 30 to 45 days of age.

The opportunity to improve daily gain and feed efficiency, especially in times of high feed costs, makes implants a management tool worth consideration for cow-calf producers, with potential for a 10-to-one return on investment.