Concepts in Beef Cow Nutrition

1. Concepts in Beef Cow Nutrition Aaron Stalker University of Nebraska-Lincoln

2. Introduction • Feed costs • Major factor in economic efficiency • Harvested forages • Majority of total feed costs

3. Annual operating costs per cow Northern Great Plains $419 USDA, Economic Research Service, 2002

4. Annual operating costs per cow Northern Great Plains $419 46% USDA, Economic Research Service, 2002

5. Biological Priority for Nutrients Priority Function 1 Maintenance 2 Growth 3 Milk Production 4 Reproduction

8. Plant Cell • PROTEIN • SUGARS • STARCH • PECTINS • FATS CELL CONTENTS PRIMARY WALL SECONDARY WALL CROSS SECTION

9. Inside NEUTRAL DETERGENT FIBER (NDF) SECONDARY WALL HEMICELLULOSE LIGNIN ACID DETERGENT FIBER (ADF) CELLULOSE PRIMARY WALL OUTSIDE

13. Ruminal Microorganisms • Ferment Structural Carbohydrates • Volatile Fatty Acids • Acetate, Propionate, Butyrate • Microbial Crude Protein

14. What is MP? • Metabolizable protein (MP) system (1996 NRC) • Acknowledges ruminal microorganisms • Protein (nitrogen) requirement • Separate from host • Degradable intake protein (DIP) • Fraction of total protein degraded in rumen • Primary source of nitrogen for microorganisms

15. What is MP? • Metabolizable protein (MP) system • Undegradable intake protein (UIP) • Fraction of total intake protein not degraded in rumen • Passes to small intestine • Metabolizable protein • Sum of digestible microbial protein and undegradable intake protein

16. Dietary Protein RUMEN SMALL INTESTINE

17. Dietary Protein SMALL INTESTINE

18. Degradable Intake Protein Dietary Protein SMALL INTESTINE

19. Degradable Intake Protein Dietary Protein SMALL INTESTINE

20. Degradable Intake Protein Dietary Protein SMALL INTESTINE

21. Degradable Intake Protein Dietary Protein SMALL INTESTINE

22. Degradable Intake Protein Dietary Protein SMALL INTESTINE Undegraded Intake Protein aka Bypass or Escape

23. Metabolizable Protein Degradable Intake Protein Dietary Protein SMALL INTESTINE Undegraded Intake Protein aka Bypass or Escape

24. Degradable Intake Protein Dietary Protein SMALL INTESTINE

25. Degradable Intake Protein Dietary Protein SMALL INTESTINE

26. Degradable Intake Protein Dietary Protein SMALL INTESTINE

27. Dietary Protein SMALL INTESTINE

28. Demonstration of NRC software

29. Feed Costs • Directly related to calving date • Survey of cow calf producers • Western and North Central Nebraska • 80% March-calving herd • Requires feeding hay • 2427 kg per cow (Clark et al., 2004)

30. Reduce Harvested Forage • Key Concepts • Cow nutrient requirements • Forage nutrient supply

31. Reduce Harvested Forage • Key Concepts • Cow nutrient requirements • Forage nutrient supply

32. Metabolizable Protein Requirement of a 1200lb March-Calving Cow, 20 lb milk Peak Lactation Fetal Growth Weaning National Research Council, Nutrient Requirements of Beef Cattle, 1996

33. Biological Priority for Nutrients Priority Function 1 Maintenance 2 Growth 3 Milk Production 4 Reproduction

34. Potential metabolizable protein from native upland forage in Nebraska Sandhills Cow weighing 1200 lbs with 20 lbs peak milk, Adapted from Lardy et al., 2004

35. Metabolizable Protein Requirement of a March-Calving Cow and Forage Supply March Calving Cow weighing 1200 lbs with 20 lb peak milk production

36. Metabolizable Protein Requirement of a June-Calving Cow and Forage Supply June Calving Cow weighing 1200 lbs with 20 lb peak milk production

37. Hypothesis • June-Calving • Annual operating costs decreased • Extend grazing • Limited Harvested Forage • Match requirements with supply

38. Objectives • Compare productivity • Traditional: March-calving • Extended Grazing: June-calving • Develop net returns budgets

39. Study Site

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42. Materials and Methods • 195 cows • 75 March-calving: Traditional • 120 June-calving: Extended Grazing • First two years not included • 4 Years of data • 4 production cycles

43. Materials and Methods • 195 cows • 75 March-calving: Traditional • 120 June-calving: Extended Grazing • 60 breeding season on meadow • 60 breeding season on upland range • 4 Years of data • 4 production cycles

44. Herd Management • Traditional system • Fed hay mid-January through April • Extended Grazing system • Fed supplement • Fed hay post-calving and winter storms

45. Weaning • Calves weaned at 210 days of age • Traditional: March-born • October • Extended Grazing: June-born • January • Pregnancy status determined • Weaning rates

46. Post-weaning management • Traditional: March-born • Grazed sub-irrigated meadow for 21 days • Extended Grazing: June-born • Fed hay and supplement for 21 days

47. Economic analysis • Budgets include actual costs of: • Harvesting hay • Purchased feed • Grazing • Fence and water maintenance • Monitoring livestock • Labor • Operating interest and overhead • Heifer replacement • Veterinary and medicine

48. Economic analysis (cont.) • Budgets do not include costs of: • Land • Property taxes • Insurance • Buildings • Management

49. Statistical Analysis • Experimental design • Completely randomized • Experimental unit • Calving system • Replication year

50. Statistical Analysis (cont.) • Proc GLM SAS • Single degree of freedom orthogonal contrasts: • Traditional vs. Extended Grazing • All measured responses • Range vs. Meadow within Extended system • Pregnancy rate • Weaning rate