Nutrient Requirements of Beef Cattle

Nutrient Requirements of Beef Cattle Oklahoma Cooperative Extension Service Oklahoma State University

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

Nutrition vs. “Fill” • Cattle have specific requirements for certain 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.

Forage Intake as a Function of Forage Quality

Dry Matter Intake Factors (cont.) Examples include: • Larger-framed cattle eat more forage than smaller-framed cattle. • 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.

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 • First nutrient limited by forage quality impact on microbial activity.

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.

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.

Protein Table Tips • Protein requirements expressed in pounds/day of crude protein, and percent of dry matter. • Replacement heifers need to gain 1-1.5 lbs./day to reach optimal breeding weight (60-65% mature weight) by 15 months of age. • Bred heifers need to gain 1 lbs./day from breeding to calving to reach 80-85% of their mature weight.

Table Tips (cont.) • The high protein requirement of heifers is due to their low dry matter intake capacity. • Growing heifers will generally need to be supplemented for adequate growth prior to their first breeding season. • Cow protein requirements increase during last 1/3 of gestation because the fetus obtains 2/3 of its growth at that time.

Table Tips (cont.) • Lactation is the most nutritionally stressful period for the cow, and therefore resquires neary twice the daily protein of dry cows. • Protein deficiency at calving can result in long intervals to rebreeding. • Larger-framed cattle require more protein for growth and maintenance than smaller-framed cattle.

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

Energy (cont.) • Heifers require additional energy for growth up to 4-5 years of age. • Thin cows require additional energy to restore body condition. • On forage-based diets, most of the energy comes from fiber digestion. • Inadequate protein in the diet for microbial synthesis means insufficient energy produced from decreased fiber digestion.

Energy Table Tips • 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, fiber, protein and fat in a feed with a correction factor of (2.25) for the high energy content of fat, and nitrogen-free extract.

Energy Table Tips (cont.) • 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 50% more than when dry.

Energy Table Tips (cont.) • Due to the increased energy demand, lactating cows will consume more forage than dry cows. • First and second-calf heifers need additional energy compared to mature cows because they are still growing.

Energy Table Tips (cont.) • 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 over the 900 lb. cow will increase energy demand and the requirement for additional feed resources by 6-8%.

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.

Questions?

Introduction • Define the subject matter • State what the audience will learn in this session • Find out any relevant background and interest of the audience

Agenda • List the topics to be covered • List the times allotted to each

Overview • Give the big picture of the subject • Explain how all the individual topics fit together

Vocabulary • Glossary of terms • Define the terms as used in this subject

Topic One • Explain details • Give an example • Exercise to reinforce learning

Topic Two • Explain details • Give an example • Exercise to reinforce learning

Summary • State what has been learned • Define ways to apply training • Request feedback of training session

Where to Get More Information • Other training sessions • List books, articles, electronic sources • Consulting services, other sources

Nutrient Requirements of Beef Cattle