Enhancing Cows' Feeding System for Optimal Performance

1. Feeding Transition Cows STEPANIE MILBURGLECTURE 12 2/23/2001

2. Goals of a Successful Feeding System • Understand the factors that will determine nutrient requirements • Deliver the needed nutrients to each cow to meet her requirements as economically as possible

3. Factors That Impact Nutrient Requirements • 1. Milk Production Curve • 2. Milk Fat and Milk Protein • 3. Dry Matter Intake • 4. Body Weight Loss and Gain

4. Phase Feeding Approach • Considers the various phases of lactation and gestation • Program is divided into periods based on milk production, milk fat percentage, feed intake, and body weight • Goal for the dry cow is to minimize metabolic disorders, increase longevity, increase profits of next lactation

5. Far off dry cows • Begins at drying off time to 21 days before calving • Adapt the rumen microbes for higher energy diets fed postpartum • Prevent metabolic disorders • -force feed trace minerals/vitamins • -limit salt intake • -closely monitor calcium and phosphorus • Provide nutrients for rapidly growing calf

6. Close Up Dry Cows • Starts 21 days prepartum • Nutritional management of macrominerals is important to enhance lactational and reproductive performance postpartum • One potential strategy for late gestation feeding is the dietary cation-anion difference (DCAD)

7. Dietary Cation-Anion Difference • Systemic acid/base balance of the cow • Feeding anionic diet increases H+ ions (creates acidosis). If cations are fed HCO3 is released (creates alkalosis) • Mild acidosis allows for greater absorption of Ca and P –very helpful to preparturient cows Sources of anionic salts: CaSO4, NH3SO4, MgSO4, MgCl, NH3Cl, CaCl

8. DCAD Cont. • DCAD = meq (Na +K) – (Cl+S)/ 100g DM • To calculate DACD the expression is: [%Na divided by .023) + (%K divided by .039)] – [(%Cl divided by .0355) + (%S divided by .016)]

9. Example • Item Dietary Conc. (%) meq DCAD • Na .10 .023 4.35 • K .65 .039 16.67 • Cl .20 .0355 5.63 • S .16 .016 10.00 • DCAD = meq(Na +K) – (Cl+S) = 5.39

10. Common Metabolic Disorders

11. Rumen Acidosis • Excessively acid pH caused by greater fermentation and acid production by microbes than can be neutralized by the animal • Cause: Too much rapidly fermentable CHO (starch) and too little effective fiber • Feedlot cattle and early postpartum cows

12. Acidosis cont.. • Acute : can cause death • Chronic or subclinical : decrease feed intake, fermentation efficiency • Prevention: • Avoid “slug” feeding • Balance starch/fiber fractions of diet • Allow for gradual adaptation to change

13. Ketosis • The excessive mobilization of body fat caused by an imbalance between glucose need and glucose supply that leads to a build up of ketones in the body • High demand for glucose (milk production or fetal growth) relative to supply (feed intake) leads to decreased glucose in blood and low insulin • Promote mobilization of long-chain fatty acids from adipose tissue

14. Ketosis cont. • The increase in ketone body concentration comes from beta-oxidation of long chain fatty acids in the liver • Ketone bodies = BHBA (beta-hydroxybutyrate), acetone, AcAc (acetoacetate) • Liver can oxidize 5 times as much fatty acid to obtain the same amount of ATP for energy

15. Ketosis cont. • As [AcAc] increases it spills into blood, urine, and milk – odor can be used as a diagnostic tool • Rarely fatal – production drops to decrease glucose demand • Administer glucose

16. Ketosis cont.. • Prevention: • Avoid over fattening (Fat cows have poor appetites!) • Provide ample amounts of well-balanced diet (high energy) • Administer Niacin (reduces lipolysis)

17. Calcium Metabolism and Milk Fever • Calcium in the blood is critical to life and is strictly regulated! • Functions of Calcium: • 1. Component of milk • 2. Bone structure • 3. Muscle Contraction • 4. Nerve transmission

18. Hormonal Regulation of Calcium • Parathyroid hormone (PTH) – secreted by parathyroid glands in response to low blood Calcium • PTH increases blood calcium by: • - increase reabsorption of Ca in kidney • - increase reabsorption from bone • - increase activation of vitamin D

19. Hormonal regulation cont. • Calcitonin – Secreted by thyroid gland in response to elevated blood Ca • Decreases blood calcium by: • Increasing urinary Ca excretion • Decrease bone reabsorption

20. Milk Fever (Parturient paresis) • A decreased blood Ca in response to Ca drain of lactation • Feed intake drops at calving and the calcium-mobilizing system is inactive at calving • Blood Ca drops, PTH and vitamin D try to increase blood Ca • Target tissues are unable to respond to hormonal signals

21. Milk Fever cont. • Symptoms: • decrease appetite and inactive digestive tract, “cold ears”, staggering, loss of balance, listlessness, coma, death • Treatment: Immediate I.V. infusion of Ca

22. Milk Fever cont. • Prevention: • 1. Feed diet low in Ca and P during dry period • 2.Give Vitamin D at 2500 X requirement for 3-5 d before calving • 3.Adjust anion-cation difference -if anionic, get acidosis (acidosis favors Ca mobilization and PTH response

23. Summary • The transition cow’s nutrient needs can easily be neglected since she is no longer with the milking group • Careful consideration to her metabolic needs helps to ensure productivity and longevity in her next lactation