1. GROWTH IMPLANTS & RATION ADDITIVES FOR BEEF CATTLE By David R. Hawkins Michigan State University

2. OVERVIEW Growth implants are widely used in the beef cattle industry. (70% to 80% of all feedlots) In general they improve average daily gain by 5% to 15% and improve feed efficiency by 5% to 10%. (Implanting generates a $10 return for every $1 invested.) Cattle that are not implanted must sell for a premium price to generate the same net profit as implanted cattle.

3. HISTORICAL The first growth implant used in beef production was DES (diethylstilbestrol). DES was a synthetic estrogen that was also used in human medicine. It was adapted for use in the cattle industry in the 1950’s by animal scientists at Iowa State University. DES was approved for use as an implant or As an oral feed additive.

4. HISTORICAL DES improved ADG by 10% to 15% and improved feed efficiency by 10%. DES was banned from use by the FDA in 1979, because DES was carcinogenic when large doses were administered to laboratory animals. The Delaney Amendment specifies a “0” level of tolerance for known carcinogens.

5. RISK ASSESSMENT When DES residues were detected, they were found in liver tissue. If one consumed liver that contained high levels of DES, one would need to consume 5,500 lbs. of liver daily to get the daily human therapeutic dose of 5 mg. We need to be realistic in risk assessment.

6. NATURAL DIETARY SOURCES OF ESTROGEN 3 oz. of beef from non-implanted = 1.2 ng. 3 oz. of beef from implanted = 1.9 ng. 8 oz. of milk = 35.5 ng. 3 oz. of peas = 336 ng. 2 oz. of eggs = 1,750 ng. 3 oz. of cabbage = 2,016 ng.

7. ESTROGENIC vs ANDROGENIC Prior to 1987, most implants were estrogenic in action. In 1987, TBA (trenbolone acetate) was cleared for use. It is androgenic in action and has an additive effect when combined with the estrogenic implants. Current research is underway to evaluate the effects of implants on beef tenderness.

8. IMPLANT RESPONSE DIFFERENCES Sex: Steers>Heifers>Bulls –Implants are not cleared for use with bulls Maturity: Growing>Finishing>Suckling Gain: Greatest response occurs when ADG is greater than 1 lb. per day.

9. IMPLANT STRATEGY Some feedlots prefer to change implants during the feeding period. Implant is cleared for use in the middle 1/3 of the ear on the backside beneath the skin. Most implants are effective for 70 to 100 days except for Compudose (140 to 170 days) Choice of implant may depend on various factors including length of time on feed.

10. EUROPEAN UNION Beef from implanted cattle is safe but implanting has been used in the past as an excuse by the EU for not importing U.S. beef. World Trade Organization ruled in favor of U.S. Many EU countries used growth implants prior to the formation of the EU. Now they feed intact males (bulls) since with natural occurring testosterone and do not implant their cattle.

11. IMPLANT REFERENCES Implants – T.L. Mader, Veterinary Clinics of North America: Food Animal Practice Vol. 14 No. 2, July 1998 OSU Implant Symposium: Impact of Implants on Performance and Carcass Value of Beef Cattle, P-957, Oklahoma State University, May 1997

12. IONOPHORES They were antibiotic like compounds which were first developed as cocciodiostats in the poultry industry. They were first approved for use with cattle in 1975. Rumensin (sodium monensin) was first, Bovatech (lasalocid) was next and recently Cattalyst (laidlomycin) was approved.

13. IONOPHORES They function only on the rumen microflora and they do not enter the body tissue of the host animal. Thus there is no withdrawal period. They are toxic to horses (especially rumensin).

14. IONOPHORES They decrease acetic and butyric acid synthesis and increase propionic acid synthesis, but have little effect on total volatile Fatty Acids produced. Feed intake is reduced but ADG is enhanced and feed efficiency improves. They also reduce the incidence of bloat, acidosis and coccidiosis in cattle receiving an ionophore.

15. IONOPHORES Ionophores are cleared for use with implants and other feed additives (be sure to read the label) and the results tend to be additive. Over 80% of feedlots use an ionophore. Cattle that are not fed ionophores must receive a premium to compensate for the loss in performance.

16. MELENGESTROL ACETATE MGA is a synthetic progesterone like compound which improves ADG (9%0 and improves Feed Efficiency (6%). MGA will inhibit estrus in intact heifers, but has no effect on spayed heifers or steers. MGA is fed orally at 0.25 mg. to 0.50 mg. Per head per day.

17. ANTIBIOTICS Antibiotics are organic substances produced by an organism, which inhibits the growth of other living organisms. Narrow spectrum anyibiotics have not proven to be effective. –Penicillin

18. ANTIBIOTICS Broad spectrum antibiotics that are effective and have received FDA approval include: –Aureomycin (chlorotetracycline) –Terramycin (oxytetracycline) –Gallimycin (erythromycin) –Bacitracin –Tylosin

19. HIGH LEVEL ANTIBIOTICS High levels (300 to 500 mg./hd./day) have been used for the first two to fur weeks in the feedlot to reduce shipping fever. These require a 48 hour withdrawal period before harvest.

20. LOW LEVEL ANTIBIOTICS Low levels (70 to 90 mg./hd./day) have been used to improve feedlot performance. Expect a 4% to 8% improvement in ADG & FE. They are effective in reducing the incidence of liver abscesses in cattle fed high concentrate rations. Liver abscesses represent an annual industry loss of $20 million.

21. FUTURE USE of ANTIBIOTICS There is a growing concern in the health community around the world about the development of antibiotic resistant strains of organisms. Expect to see more restrictions and perhaps even a ban on indiscriminate feeding of antibiotics to livestock at some future date.

22. FEED ADDITIVE REFERENCE Medicated Feed Additives for Beef Cattle T. Herrman, S. Baker and G. Stokka, Kansas State University, Beef Cattle Handbook BCH – 5550, pg. 437-445