In last month’s column, I covered the various classes of implants currently on the market and traced the development of the technology over the last 50 years or so. With this column, I want to look at some of the factors to consider when choosing an implant for feedlot cattle, with emphasis on the class of implants containing a combination of estrogen (E) and trenblone acetate (TBA).
One of the first steps to consider when choosing an implant is deciding on how aggressive you want to be with your program. Aggressive implant programs focus on maximizing rate of gain and feed efficiency and carcass lean yield. However, a potential drawback is that these programs can have a negative impact on carcass quality grade (i.e. marbling). Conservative programs also target enhanced growth and feed efficiency but the improvement in performance is not as great as that seen with a more aggressive approach. Conversely, the negative impact on marbling is also not as great when a conservative approach is taken.
There are two factors that determine the relative “aggressiveness” of an implant program. The first is the strength of the implant and the second is the length of time the implant has to release its hormonal load. In today’s implant market, it is possible to purchase an implant that has between 40 and 200 milligrams (mg) of TBA. Implants at the lower end of this range (i.e. 40 mg) are considered less potent and are typically used as initial feedlot implants in 180-day or longer feeding programs. Implants in the mid-TBA concentration range (i.e. 80 to 120 mg) are considered more moderate in terms of their potency and are often used as initial feedlot implants in 180-day or longer feeding programs or as the last implant (i.e. terminal) prior to slaughter.
Implants with 200 mg of TBA are considered high potency implants and are typically used as the last implant prior to slaughter, although in very aggressive re-implant programs, some producers will use these high potency implants as both the initial and terminal implant. The exception to this last statement is the relatively new class of implants that incorporate delayed-release or slow-release (i.e. coated) technology. These implants contain 200 mg of TBA but because the TBA is released in phases or is slowly released over time, they are not considered as “aggressive” as the traditional 200-mg TBA implants. As discussed in my September column, these coated implants are effective over a 200-day period and eliminate the need for re-implanting.
The second factor to consider when determining the relative aggressiveness of an implant program is the length of time the implant has to pay out. With typical, non-coated implants, the payout period starts when the implant is inserted into the animal’s ear and continues until the hormonal payload is spent. This payout period might range from 100 to 120 days with medium-potency implants and up to 140 days with non-coated higher-potency implants. Implants with coated technology may take up to 200 days to payout.
It is important to note that with traditional non-coated implants most of the hormonal payload is released relatively early in the payout period, thus the greatest impact of the implant on growth and behaviour occurs early in the payout period. At the end of this period, when the implant is spent, it is said to have “paid out.” However, if cattle are slaughtered prior to the end of the payout period, particularly with high-potency implants, there is greater potential to have a negative impact on carcass quality. Similarly, if cattle are re-implanted prior to the initial implant having “paid out,” then the remaining hormone from that initial implant will continue to be released and add to that released from the terminal implant. In such situations, performance (i.e. gain and feed efficiency) is enhanced, although such “stacking” can have detrimental effects on animal behaviour (i.e. increased riding activity). In contrast, if implants are allowed to pay out before re-implanting or prior to slaughter, the program is considered more conservative as the growth-promoting effects of the initial implant have run their course.
As a cattle feeder deciding on an implant program, you need to choose where on the continuum of conservative to aggressive you want your program to fall. If superior gains and feed efficiency are of prime importance and you are not overly concerned with carcass quality grades, then as long as you are prepared to accept potential behavioural issues, higher-potency implants may be the direction you want to go. If you are interested in enhanced performance but perhaps are selling cattle on a grid or under contract where marbling is important, then a more conservative approach is likely the most appropriate choice. If issues with facilities, time and labour impede re-implanting, then the longer-acting delayed/slow-release implants may be an attractive option.
If you are still undecided about which direction to go, it would be well worth your time to seek professional advice from your nutritionist and/or veterinarian. In next month’s column, I will examine the management considerations involved with implementing a successful implant program.