1. Growth promotants and feed enhancers AnS 426

2. Growth Modifiers Two broad groups Two broad groups –Agents that alter the digestive process –Agents that modify the way the animal uses or partitions nutrients for growth

3. Growth modifiers General types General types 1.Antibiotic growth promoters 2.Ionophores 3.Implants 4. -adrenergic agonist 5.melengestrol acetate (MGA)

4. Antibiotic growth promoters Any medicine that destroys or inhibits bacteria and is administered at a low, subtherapeutic dose Main antibiotics added to cattle feed – –Chlortetracycline – –Oxytetracycline – –Tylosin 3 to 5 % improvement in gain and FE No withdraw if fed at subtherapeutic dose

5. Antibiotics fed to finishing cattle for the control of liver abscesses When fed high concentration rations, cattle that are borderline on subacute acidosis and have a few small liver abscesses gain faster and more efficiently than cattle that are not stressed and have no liver abscesses. However, managing to allow a slight amount of acidosis is difficult.

6. Feed enhancers Ionophores Ionophores –monensin (Rumensin) –lasaloacid (Bovatec) Improve feed conversion Improve feed conversion –Increase efficiency of bacterial protein and energy metabolism –Can also reduce incidence of digestive upsets

7. Growth modifiers Feed enhancers Feed enhancers Study by Dr. Gill, OSU Reason high silage diet showed greater improvement in feed efficiency attributed to lower propionic acid level initially SilageRumensin Percent VFAs ADGFeedFeedPercent Level(g/T)AceticPropionicButyricConsum.Conver.Improve. 30 % 048.5539.5511.953.3118.775.69 5.66 3046.5045.707.853.2717.885.46 75 % 061.6024.7013.702.5218.517.40 7.74 3054.7533.7511.552.4917.086.82

8. VFA Why dose changing the VFA profile affect performance: –63% of energy from acetic acid is used for maintenance and production –100% of energy from propionic acid is used for maintenance and production –75% of energy from butyric acid is used for maintenance and production

9. Growth modifiers Effective dose Effective doseRumensin: 150 to 330 mg/hd/day Bovatec: 100 to 360 mg/hd/day NO withdraw period NO withdraw period The effects of ionophores and growth promoting implants are additive The effects of ionophores and growth promoting implants are additive

10. Protein sparing Ionospheres decrease the breakdown of feed protein and thus increase bypass protein that reaches the small intestine Ionospheres decrease the breakdown of feed protein and thus increase bypass protein that reaches the small intestine This has little effect on performance of feedlot cattle on high-grain diets, but it is important in growing cattle on high- roughage diets This has little effect on performance of feedlot cattle on high-grain diets, but it is important in growing cattle on high- roughage diets The protein sparing effect on performance is maximized when natural protein is fed below the animals requirement The protein sparing effect on performance is maximized when natural protein is fed below the animals requirement

11. Rumensin Can be fed with tylosin or MGA Can be fed with tylosin or MGA Finishing Cattle – –1 to 3 % improvement in daily gain – –6 to 8 % improvement in feed efficiency Growing Cattle – –5 to 15 % improvement in daily gain – –8 to 12 % improvement in feed efficiency Growing cattle on pasture – –Provide in supplement or free choice mineral – –Can supplement 300-400 mg/hd every other day

12. Bovatec Not cleared to be fed with antibiotics or MGA Not cleared to be fed with antibiotics or MGA Finishing cattle –4 to 6 % improvement in daily gain –6 to 8 % improvement in feed efficiency Growing cattle –5 to 15 % improvement in daily gain –8 to 12 % improvement in feed efficiency

13. Use of Ionophores in transition to finishing diet Cattle started on feed without ionophores Cattle started on feed without ionophores –more erratic feed intake patterns –more digestive problems

14. Use of Ionophores in transition to finishing diet Rumensin Rumensin –Feeding 100 mg/hd/d during the step-up period and then switching to 200-300 improves daily gain, feed intake, and feed efficiency compared to starting cattle on 200 -300 mg/hd/d improves daily gain, feed intake, and feed efficiency compared to starting cattle on 200 -300 mg/hd/d Bovatec Bovatec –The response to stepping-up Bovatec?? Less?…Bovatec does not reduce intake as much as Rumensin early in the feeding period Less?…Bovatec does not reduce intake as much as Rumensin early in the feeding period

15. Implants General types General types 1.Estrogen based (estradiol, zeranol, and progestrone) 2.Androgens (testosterone and trenbolone acetate or TBA) 3.Combination of estrogen and androgens

16. Implants No withdraw time No withdraw time Cost usually between $1-3 Cost usually between $1-3 Increase ADG 5 to 30% Increase ADG 5 to 30% Increase feed conversion 6 to 16% Increase feed conversion 6 to 16%

17. How to Implant 1) Load Implant Gun with implant cartridge 2) Insert needle between skin and cartilage in middle third of the ear 3) Pull trigger and retract needle 4) Check implant site with thumb 5) Disinfect needle 1) Load Implant Gun with implant cartridge 2) Insert needle between skin and cartilage in middle third of the ear 3) Pull trigger and retract needle 4) Check implant site with thumb 5) Disinfect needle

18. Implants Mode of action: 1.Exogenous estrogenic promotants are thought to enhance protein gain through increased production of growth hormone, insulin and insulin-like growth factors. 2.Androgenic substances are thought to increase muscle growth by inhibiting the release of hormones (e.g. glucocorticoids) which cause degradation of muscle; this results in net shift in the partition of nutrients which is manifested by faster relative rates of muscle growth.

19. How Implants Work MUSCLE Pituitary Protein synthesis Protein breakdown Growth hormone ESTROGENS ANDROGENS X Beta agonists

20. Implants and -adrenergic agonists Mode of action: partition nutrients into the more desirable, higher valued components (i.e. muscle) and away from the less desirable components of the carcass (i.e. fat) causing an apparent shift in the lean tissue growth.

21. -adrenergic agonist -adrenergic agonist ractopamine hydrochloride (optaflexx) Feed during the last 28 to 42 days of the finishing period 150-300 mg/hd/d and no withdraw zilpaterol hydrochloride (zilmax) Feed during the last 20 to 40 days of the finishing period Feed during the last 20 to 40 days of the finishing period 60-90 mg/hd/d and has a 3 d withdraw

23. -adrenergic agonist -adrenergic agonist Structurally similar to catecholamines and other compounds that bind to the beta-adrenergic receptor Structurally similar to catecholamines and other compounds that bind to the beta-adrenergic receptor Agonist: Able to bind to receptor and elicit response Agonist: Able to bind to receptor and elicit response beta-agonists works via the β- Adrenergic Receptor beta-agonists works via the β- Adrenergic Receptor

24. Repartitioning effects are due to stimulation of lipolysis and changes in muscle protein metabolism

25. Why do we only feed - agonists at the end of finishing? Market cattle become less efficient during the last month of the finishing period, because the animal is depositing less muscle and more fat. Market cattle become less efficient during the last month of the finishing period, because the animal is depositing less muscle and more fat. Chronic exposure to a ligand can cause desensitization of the receptor due to uncoupling or down-regulation of receptor Chronic exposure to a ligand can cause desensitization of the receptor due to uncoupling or down-regulation of receptor

26. -adrenergic agonist -adrenergic agonist Optaflexx: Rumensin may reduce feed intake during adaptation period

27. Melengestrol acetate (MGA) Similar to progesterone Similar to progesterone Suppresses estrus of intact heifers Suppresses estrus of intact heifers Reduces injuries and energy loss from riding and chasing Reduces injuries and energy loss from riding and chasing –3 to 7 % improves gain and feed efficiency Effective dose 0.25-0.5 mg/hd/d Effective dose 0.25-0.5 mg/hd/d Cost about 1 ¢ /da Cost about 1 ¢ /da