Nutrient Requirements of Beef Cattle Oklahoma Master Cattleman

Nutrient Requirements of Beef Cattle Oklahoma Master Cattleman Program Oklahoma Cooperative Extension Service Oklahoma State University

Outline • • Estimating Intake Utilizing Rumen Microorganisms Key Nutrients Cattle Requirement Tables

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

Forage Intake Forage Quality High Average Low % Protein lb DM / day › 12% 25 6 – 12% 20 ‹ 6% 15

Stages of Production • • Post calving, early lactation 1 st trimester, mid to late lactation 2 nd trimester, dry period (post-weaning) 3 rd trimester, dry period (pre-calving)

Forage Capacity of Beef Cows % of Body Weight Forage Maturity Stage of Production Dry Lactating Low Quality 1. 8 % 2. 2 % Average Quality 2. 2 % 2. 5 % High Quality 2. 5 % 2. 7 %

Dry Matter Intake Other Factors: • Larger-framed cattle eat more forage than smaller-framed cattle. • “Fleshy” cattle eat 3 -10% less forage than average to thin-fleshed cattle. • Cold stress increases intake, while heat stress decreases intake.

Nutrition vs. “Fill” • Cattle have daily requirements for specific nutrients. – Protein, Energy, Minerals, Vitamins, Water • Intake on a forage-based diet is limited by capacity of the digestive tract. • Cattle can be “filled” to death on low quality roughages.

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.

Protein – Rumen MCO Increased Intake = More Energy 0 . 3 . 6 . 9 1. 2 1. 5

Protein: The First Limiting Nutrient • Protein – Key Nutrient • Composed of hundreds of amino acids. • Protein Utilization by Beef Cattle • • Tissue growth and maintenance Immune system antibodies Blood proteins Milk production • Function of Rumen Microorganisms • Utilize proteins from feed • Digest Roughages for cattle utilization • Are digested in small intestine as protein

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

A New Way to Look at Protein By-Pass protein • Metabolizable Protein System – Characterizes Protein Degradability – Site and Extent of Protein Digestion • DIP - Degradable intake protein is broken down in the rumen. • UIP - Undegradable intake protein is not broken down in the rumen, but in the small intestine. • MP - Metabolizable protein is the sum of microbial-derived protein plus UIP.

Metabolizable Protein System Rumen Feed MP CP UIP DIP Small Intestine NH 3 Microbial Protein NH 3 Indigestible Protein

Energy Requirements • • • Grazing Movement Digestion Temperature Maintenance Reproduction Fetal Development Milk Production Heifer Growth (4 yrs old) Body Condition Changes

Energy Requirements • Key requirement factors – Weight – Rate of gain – Lactation/fetal development • Grazing cattle – energy is produced from rumen digestion of forage • Linked to adequate protein intake

Expressing Energy Requirements Digestible starch + Digestible fiber + Digestible protein + Digestible fat = Total Digestible Nutrients (TDN)

Mineral Requirements • Main Macro Minerals – Calcium + Phosphorus – Tables 11. 2 to 11. 6 – Master Cattlemen – Ch. 14 • Other Macro Minerals – General Dietary Guidelines – Table 11. 7 • Micro Minerals & Vitamins – Table 11. 7

Water Requirements • Important Nutrient • Factors Affecting Intake – Age – Weight – Temperature Intake in Gallons Temp = 60° F Temp = 90° F 400 lb calf 5. 0 9. 5 800 lb yearling 9. 1 17. 4 900 lb Lactating cow 14. 5 16. 2

Nutrient Requirement Tables Nutrient Requirements: Class Beef Cattle Manual 2004 Beef Cows Table 11. 2 Pregnant Replacement Heifers Table 11. 3 Growing Steer and Heifer Calves Table 11. 4 Growing Yearlings Table 11. 5 Growing and Mature Bulls Table 11. 6 Minerals and Vitamins Table 11. 7 Water Table 11. 8

Nutritional Requirement Table Tips • Protein requirements are expressed two ways: Ø Total pounds per day of crude protein Ø Percent protein in ration dry matter. • Cow protein requirements increase during last 1/3 of gestation as the fetus obtains 2/3 of its growth. • Lactation is a very nutritionally demanding period for cattle, significantly increasing protein and energy needs compared to dry cows. • The high protein requirement of heifers is due to their low dry matter intake capacity. • Large-framed cattle require more protein and energy for growth and maintenance than small-framed cattle.

Nutritional Requirement Table Tips • Requirements expressed as: Ø Total digestible nutrients (TDN) Ø Net energy for maintenance (NEm) Ø Net energy for gain (NEg) • 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. • Inadequate protein in the diet for microbial synthesis means insufficient energy produced from decreased fiber digestion.

Summary • Determining feed intake is the first step to calculating nutrient needs. • Rumen microorganisms break down roughages and provide energy and protein in the diet. • Beef cattle have specific requirements for protein, energy, vitamins, minerals, and water. • The National Research Council has published information to enable beef cattle producers to determine the nutrient needs of their cattle.

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