Nutrient Requirements of Beef Cattle - MP 391 Overview

Nutrient Classes Carbohydrates Fats Protein Minerals Vitamins Water ENERGY (calories)

Factors Affecting Nutrient Requirements Age Size Breed (Brahman influence, maternal) Stage of Production (growing, gestating, lactating) Level of Production (milk, growth rate) Environment Thermal stress (insulation)

Protein Requirements commonly expressed as Crude Protein (N x 6.25) Growing/finishing diets may be segragated into Rumen degradable and rumen undegradable protein.

Example Cow CP Requirement Page 6. MP 391

Example Cow CP Requirement

Energy Commonly expressed as TDN for beef cows TDN = digestible fat + digestible carbohydrate + digestible protein May also be expressed as Calories for growing cattle Net Energy for Maintenance (NEm) Net Energy for Gain (NEg)

Example Cow TDN Requirement Page 6. MP 391

Example Cow TDN Requirement

Example NE Requirement for Growing Calf

Dry Matter Intake Intake expressed on DM basis to account for differences in feedstuff moisture Affected by Size (Body weight) Stage of pregnancy Diet digestibility Environment Thermal stress Housing conditions Anti-quality factors Palatability Negative feedback mechanisms (toxins)

DMI As Affected By Cow Size and Diet Quality

Example Energy Supply for Cows Diet Digestibility50% TDN60% TDN70% TDN DMI (1100 lb cow) TDN (lbs) Late Gestation (11.7 lb) Early Lactation (14.5 lb) Mid Lactation (13 lbs)

Example Energy Supply for Growing Calves TDN67% NEm (Mcal/cwt)70 NEg (Mcal/cwt)43 DMI (lbs)12.5 NEm required (Mcal)4.5 Feed DM available for maintenance (lbs)(4.5 / 0.70) = 6.4 Feed DM available for gain (lbs)(12.5 – 6.4) = 6.1 NE available for gain (Mcal)(6.1 * 0.43) = 2.62 Expected ADG1.7 lb/d