Nutrient Requirements of Beef Cattle

1. Nutrient Requirements of Beef Cattle

2. Outline • Nutrients • Stages of production • Factors affecting intake • Rumen microorganisms • Protein • Energy • Using the tables

3. Nutrient Categories • Water • Carbohydrates • Protein • Lipids (fats & oils) • Minerals • Vitamins

4. Chemical Composition of Yearling Steers Carstens et al., 1991

5. Four Stages of Production • Post-calving • Early lactation • 1st trimester • Late lactation • 2nd trimester • Mid gestation • Dry period • 3rd trimester • Late gestation • Dry period

6. Dry Matter Intake is Influenced By • Weight • Condition • Stage of Production • Forage Quality • Amount and Type of Supplement Provided • Environmental Conditions

7. Dry Matter Intake Factors (cont.) Examples include • Larger-framed cattle eat more forage than smaller-framed cattle. Capacity of the digestive tract is the single greatest factor. • Nursing cows eat more forage than “dry” cows. • “Fleshy” cattle eat 3-10% less forage than average to thin-fleshed cattle. • Cold stress increases intake, while heat stress decreases intake.

8. Forage Capacity of Beef Cows% of Body Weight

9. Protein: The First Limiting Nutrient • Composed of hundreds of amino acids Provides for: Tissue growth and maintenance Immune system antibodies Blood proteins Enzyme system function Milk production Microbial synthesis • Protein supply has dramatic impact on microbial activity

10. Feed the Rumen-Feed the Cow • Rumen microorganisms breakdown dietary protein for their own growth and development • The microbes are digested in the small intestine of the ruminant • Microorganisms need 7% crude protein for their maintenance and reproduction • Limited CP for microbial synthesis, limits fiber digestion for the ruminant

11. Protein – Rumen MCO Increased Intake = More Energy 0 .3 .6 .9 1.2 1.5

12. Forage Protein vs. Requirements 400 lb 500 lb 700 lb Forage Protein

13. Metabolizable Protein • Characterizes protein degradability in the rumen, and utility in assuring optimal rumen function. • Degradable intake protein (DIP) is broken down in the rumen. • Undegradable intake protein (UIP) is not broken down in the rumen, but in the small intestine. • Metabolizable protein (MP) is the sum of microbial-derived protein plus UIP.

14. Rumen Feed MP CP Indigestible Protein UIP DIP Small Intestine NH3 Microbial Protein NH3 Metabolizable Protein System

15. Energy Requirements • Grazing • Movement • Fetal Development • Milk Production • Temperature Maintenance • Reproduction • Digestion • Voiding Body Wastes

16. Energy Requirements • Key requirement factors • Weight • Rate of gain • Lactation/fetal development • Grazing cattle – energy is produced from rumen digestion of forage • Inadequate protein in the diet for microbial synthesis means insufficient energy produced from decreased fiber digestion

17. Energy Requirements • Heifers require additional energy for growth up to 4-5 years of age • Thin cows require additional energy to restore body condition

18. Energy Terms in the Requirement Tables • Requirements expressed as: Total digestible nutrients (TDN) Net energy for maintenance (NEm) Net energy for gain (NEg) • TDN is the sum of the digestible starch and other non-structural carbohydrates, fiber, protein and fat in a feed with a correction factor of (2.25) for the high energy content of fat

19. Energy Observations • TDN is expressed as percent of diet dry matter, as well as pounds/day required • Net Energy requirements are expressed as mega calories/lb. of feed, and mega calories required/day • Lactation represents the greatest need for energy beyond maintenance by as much as 30 to 70% more than when dry

20. Energy Observations • Inadequate energy for heifers during last 1/3 of gestation, and from calving to rebreeding can result in poor rebreeding performance • Every 100 lb increase in mature weight of cows will increase the requirement for additional feed resources by 6-8%

21. Vitamins and Minerals • Covered in detail in OK Beef Cattle Manual Chapter 14 • Table 11.7 (page 103) shows requirements and maximum tolerable amounts

22. Nutrient Requirement Tables

23. Water Requirements • Important Nutrient • Factors Affecting Intake • Age • Weight • Temperature

24. Summary • Beef cattle have specific requirements for protein, energy, vitamins, minerals, and water • The nutrient requirements vary depending on such factors as: breed, gender, age, weight, stage of production, rate of growth, environmental conditions, etc • The National Research Council has published information to enable beef cattle producers to determine the nutrient needs of their cattle, and design feeding regimes to meet those needs