Dan LoyProfessor of Animal ScienceDirector, Iowa Beef Center

Iowa State University

I. Cattle Performance and Comfort under Different Environmental Conditions

January 2013 Feedlot Inventories 1,000 Head

Texas 2,730

Nebraska 2,550

Kansas 2,250

Iowa 1,280

Colorado 1,030

US Cattle Feeding Regions

Market share change 2012-2013

Percent of US Cattle on Feed

2012

Percent of US Cattle on Feed

2013

Change

Texas 20.9 20.4 -.5%

Kansas 16.9 16.9 NC

Nebraska 18.7 19.1 +.4%

Iowa 9.2 9.6 +.4%

Source: World weather online

Source: World weather online

Source: World weather online

Location of Cattle Feeding and Average Annual Precipitation

Location of Cattle Feeding and Days less than 0°C

Environmental Challenges

• Cold Stress

• Heat Stress

• Mud

Effect of Environment on Energy

Requirements

EFFECTIVE AMBIENT TEMPERATURE

THERMONEUTRALZONE

Low High

Heat StressCold stress

OptimumforPerformanceand Health

LowerCriticalTemperature

UpperCriticalTemperature

Cold Stress

Hair as insulation

Lower Critical Temperature °C

•Coat Description LCT

•Summer or wet 15

•Fall 7

•Winter 0

•Heavy winter -8

Effective Temperature

Wind Speed Temperature (celcius) (kph) -23 -18 -12 -7 -1Calm -23 -18 -12 -7 -18 -27 -21 -16 10 -524 -32 -26 -21 -16 -1048 -43 -37 -32 -27 -21

*Maintenance Requirements increase 1.25% for each degreeof cold stress.

Heat Stress• Affected by effective

ambient temperature• Air temperature• Solar radiation• Air movement• Contact surfaces• Precipitation

Heat Stress

• Beef NRC (2000)

• Maintenance requirement increased when temperatures exceed 30 C– 7% for rapid shallow breathing– 18% for open mouth panting

July 19, 2011 - 3:00 pm• 35 degrees C

• SunnyFeels like 44 degrees CWind 9.3 km/hr southHumidity 58%

Images and data from Dr. Grant Dewell, DVM, Extension Beef Veterinarian, ISU

Black Steer Full Sun

40.0 C51.6 °C 50.8 °C

43.7 °C

54.0 °C

Black Steer Shade Monoslope

41.9 °C

38.6 °C

41.8 °C

42.2 °C41.0 °C

Black vs White Steer Full Sun

45.3 °C

42.0 °C

52.4 °C

http://www.iowabeefcenter.org/heatresources.html

NRC (1981)

Effects of Mud on Performance

Mud depth Intake reduction

10-20 cm 5-15%

30-35 cm 15-30%

NRC (1981, 2001)

Plus: reduced insulation value of hair coat and increased energy cost for walking

Effects of Mud on Cattle Performance

• Reduction in intake

• Loss of insulation value of hair coat

• Increased energy expenditure to move between feed, water and resting location

Energy Requirements vs. Previous Temp.

50

60

70

80

90

100

110

120

-20 -10 0 10 20 30 40

Previous Temperature, OC

NE

m R

equ

ired

, M

cal/

BW

0.75

Questions?

Thanks !!!

Dan LoyProfessor of Animal ScienceDirector, Iowa Beef Center

Iowa State University