One of the best management strategies for reducing feedcosts and improving gain is the use of feed additives. However the size of this "Feedlot Primer" would have to be greatly increased in length to adequately discuss the various brands available and their unique dosage requirements and attributes.
Ionophores are antibiotic class that alters rumen fermentation characteristics. The result is improved feed efficiency at the same or higher level of gain compared to a diet without ionophores.
The ionophores RumensinTM and BovatecTM are probably the most familiar ionophores for producers because they have been on the market for a relatively long time. Some recently approved ionophores are CattlystTM and VmaxTM. Ionophores are also fed for other reasons, including coccidiosis control and control of acidosis and bloat problems. VmaxTM also appears to be effective for liver abscess control. Although not classified as an ionophore, GainProTM has some ionophore characteristics.
Ionophores are fed to approximately 90% of all feedlot cattle in the U.S. They are particularly beneficial for cattle fed high grain (less than 12% roughage) diets because of their role in reducing acidosis and bloat. See label recommendations for each. Ionophores may not improve feed efficiency in diets with greater than 4% tallow, but they would still be effective insurance against acidosis and bloat.
Antibiotics have been used to improve gain and feed efficiency of cattle. Antibiotics are added to feed to minimize secondary bacterial infections and to control liver abscesses. Antibiotics available are chlortetracycline, oxytetracycline, bacitracin, and tylosin. Withdraw of antibiotics for varying periods of time prior to slaughter will be required depending upon the compound and the level at which it is fed.
Melengestrol AcetateTM (MGA) can be added to feedlot heifer rations. It improves rate of gain and feed utilization. This is accomplished by suppressing estrus or heat. Withdraw time for MGA is 48 hours.
Buffers are sometimes used to moderate pH changes in the rumen (Stock and Mader, 1985). Buffers can be used when adapting cattle to high grain diets or when feeding concentrates such as wheat at high levels. Various buffering agents include sodium bicarbonate, limestone, sodium bentonite, and magnesium oxide. Sodium bicarbonate and limestone can be fed at about 1% of the diet dry matter.
Basic rumen studies suggest that live yeast cultures can stimulate growth of cellulolytic microorganisms in the rumen. Yeast cultures do not appear to affect digestibility, however, yeast cultures appear to alter the shape of the degradation curve causing a reduction in the lag phase before digestion commences. Therefore the digestibility is not changed but the rate of degradation is increased. Birkelo and Berg (1994) observed that a yeast culture product improved performance of yearling cattle fed corn-based finishing diets containing less than 10% roughage. Birkelo and Rops (1994) observed that a yeast culture product did not improve performance of growing calves limit-fed a high concentrate diet. More research is needed to evaluate the most appropriate situations for the use of yeast cultures.
Ear implants can increase rate of gain and improve feed efficiency of cattle. There are 11 implants currently available for this purpose (Pritchard, 1993b). There are numerous strategies based on the number of implants and combinations of implants that can be used from weaning to slaughter. Implant suitability depends on cattle age, sex, frame size, weight, days on feed, projected rate of gain, and implant history.
Duration of use and level of active ingredients (termed type in this article) are important criteria for developing a strategy of implant use. Type or potency refers to the combination of primary and secondary biological effects of the active ingredient(s) of the implant (Pritchard, 1993b). The duration values in the following table reflect manufacturer's recommendations and industry practices.
Classification of implants for weaned calves with regard to active ingredients and duration of use.
| Implant | Type (Level of Ingredients) |
Duration (Days) |
| Compudose Implus-C Implus-S or H Finaplix-S or H Ralgro Synovex-C Synovex-S or H Revalor Finaplix + Synovex or Implus or Ralgro |
BB AA BB AA AA AA BB CC CC |
150-200 60-70 100-130 80-100 60-70 60-70 70-100 80-100 80-100 |
Adapted from: Pritchard (1993b)
Total gain can be improved if cattle are re-implanted over time. However, the gain response is reduced as cattle are reimplanted (Pritchard, 1993b). While the first implant may increase gain 20%, re-implanting with the same product 70-100 days later may increase gain only 15%. A suitable strategy may be to start with a lower potency implants (Type AA and BB implants) and use higher potency implants (Type BB and CC implants) in cattle approaching finish weight.
Any implant strategy should take into account the expected finish date of the cattle. One can expect animal performance to be depressed if cattle are fed beyond the active duration of the final implant. Implants increase animal and carcass weight. Small-, medium-, and large-framed cattle respond similarly to implants (Pritchard et al., 1990). Use moderation in your implant program if your cattle are already borderline for maximum industry standards for animal and carcass weight.
Occasionally, there is over-use of implants. Estrogenic compounds can increase riding and prolapses. Androgenic compounds can increase the number of dark cutters. Both classes of implants can reduce body fatness (good!) and quality grade (bad!) at a constant body weight.
CC-Type implants should usually be used only once and the best time to use them is as the last implant before slaughter. However, with long fed Holsteins, begun at about 400 lbs, one might consider using CC-type implants twice. The first CC-type implant given 160-200 days prior to finishing and the second CC-type implant administered 80-100 days prior to finishing. Develop your implant strategy so that the last CC-type implant is not given at less than 80 days or more than 100 days prior to slaughter.
The implanting strategy will work but only if proper implanting techniques are used. Check the directions for proper implant site location in the ear. To avoid crushing the implant, insert the needle to it's full length and then withdraw a distance equal to the space to be occupied by the implant. Crushed implants can result in bullers and reduced duration of implant effect. Some implanting guns do this procedure for you. Good sanitation should be observed. Infection will reduce the effectiveness of the implants or cause them to be expelled from the ear. If the ears are wet you should probably wait until they are dry. Implanting needles should be checked for burrs because any obstruction can damage the implant. In addition, burrs tear tissue at penetration sites and greatly increase the likelihood of infection and abscessation. Proper implanting means doing it correctly not necessarily doing it rapidly.