Progestins • Classified as steroid hormones • Progesterone o member of the progestin family o responsible for maintenance of pregnancy and mammary growth and development • MGA is a synthetic progestin that is 100X more potent than progesterone o Improves feed to gain ratios in heifers and suppresses estrus Synthetic hormones • Anabolic steroids – those that result in increased tissue accretion • Androgens – improve growth, FE, carcass protein esp. in heifers • Testosterone is anabolic • Combined with estrogens, testosterone is more effective for growth parameters Synthetic hormones • TBA – Trenbolone Acetate – a synthetic steroid is weak, yet when combined with estrogen is very effective in steers • It binds to testosterone and estrogen receptors in skeletal muscle. • This yields a slight decrease in protein synthesis and a significant result in (decrease) in protein degradation, thus an increase in protein accretion Growth Hormone GH or Somatotrophin (ST) Produced by the anterior pituitary Acts in an endocrine manner Liver can synthesize growth factors to help regulate growth, acts as a mediator • GH also increases lipolysis of fatty acids from adipocytes • • • • Growth Hormone • GH is a protein hormone • It is not a orally active hormone and admin. Via injection • GH has been shown to increase wt. gain, feed conversion while decreasing feed intake • When nutrients are limited, GH increases lipolysis, and decreases growth because IGF-I becomes uncoupled from GH, therefore IGF-I decreases. These changes causes a transfer of calories from adipose to vital functions Insulin and Glucagon • Insulin – increases the storage of glucose, fatty acids, and amino acids as glycogen, triglyceride and protein • Glucagon – opposite actions of insulin • Glucagon and Insulin act on a negative feedback system o When one goes up the other goes down o Functions to mobilize glucose, fatty acids, and increase amino acid catabolism o Insulin dominates the system in mammals Helpful Chart Glucocorticoids • Cortisol exert permissive effects by enhancing the action of other hormones on many tissues. They support and regulate a variety of important cardiovascular, metabolic, immunologic, and homeostatic function. Catecholamines • Epinephrine (adrenaline) o Stored in the adrenal medulla o Released when stimulated by nerve fibers o Induces significant metabolic effects on various tissues in response to stress • Stress o Causes adjustments in metabolism o Epinephrine maintains sufficient blood circulation by impacting the heart and blood vessels. Effects of Epinephrine • • • • • Mobilization of glycogen for energy Increased heart rate Increased blood flow Increased body temperature Increased respiration •:• SmartDraw Effect. о{ Epinephrine Adltenall Me,dluilla .' 'Menlt:al Alёrlt:ness Dilc:Ф:�·s CoflOп,a11ry Vess:ets ... __ _ 1М u scl е Gon,tr.a cti о, Ef�ici n 'V • Gly,og • Effects of Stress • Long term stress (several days) depletes glycogen stores prior to processing o Dark cutting beef o Dark, firm, dry pork • Acute stress (short term) prior to slaughter accelerates metabolism that occurs post mortem o Leads to earlier onset of rigor o Pale, soft, exudative pork Thyroid Hormones • Play an important part in metabolism, growth, and development • Increase protein synthesis • Stimulate lipid metabolism Objectives • Define hormone action • Explain the 5 types of hormone action • Know the function and effects of hormones in detail