Growth-promoting implants, and implant protocols, have evolved considerably since their introduction in 1958. Initially a feedlot tool, implant technology eventually extended the benefits to pre- and post-weaned steers and heifers on pastures. Early concerns that calf implants would reduce feedlot gains, inhibit response to subsequent implants or significantly reduce beef quality have dissipated with refinements in the products and protocols.
Most implant research though, has focused on beef breeds. But over the past 20 years, the number of Holstein steers in the fed-beef supply chain has increased dramatically. In 2000, Holstein steers accounted for around 5.7% of feedlot cattle. By 2016, that percentage increased to over 20%, largely due to a decline in the veal market.
In a recent webinar hosted by the Dairy Calf and Heifer Association (DCHA), Merck Animal Health Technical Services Manager Grant Crawford, PhD, outlined some history of growth-promoting implants and their application in Holstein steer calves managed for beef production.
Crawford notes their currently are four FDA-approved implant products available for use in suckling calves – Ralgro, Synovex-C, Compudose and Encore – each with different hormone levels and duration.
Most research on calf implants has focused on beef-breed cattle, but Crawford highlighted two studies on implanting Holstein calves raised in hutches. In an older study published in the Journal of Dairy Science in the late 1980s, University of Florida researchers compared Holstein steers receiving a low-dose Ralgro implant at birth and again at 90 days with non-implanted control steers and with intact bull calves. In this trial, the implanted calves showed a 9.6% improvement in gains, with an 11-pound advantage over control steers at 90 days and a 34.5% advantage at 180 days. The implanted steers also outperformed the intact bull calves in average daily gains and total gain.
In a more recent Idaho trial using 1,248 91-pound Holstein calves, researchers followed the calves through finishing at around 500 days of age. In this trial, some calves received Ralgro implants at birth and at 92 days, some just one implant at either day 0 or day 92 and control calves received no calf implants. All the calves were castrated at 35 days and all received the same series of implants after entering the feedlot at 169 days. In this trial, implanted calves showed a significant improvement in gains at 92 days of age and they held that advantage up to around 365 days. Between 365 and 500 days, the control calves caught up in this study, suggesting compensatory gains once implanted in the feedlot. Most studies in beef steers have shown advantages for cattle implanted as calves through growing and finishing stages.
Crawford concludes that low-dose implants provide a weight-gain advantage in dairy steer calves, particularly in the pre-weaning and growing stages.
For more on implants and implanting, see these articles from BovineVetOnline: