WINTER FEEDING OF BEEF COWS

ByTom Hoagland

University of Connecticut

Water consumption at different environmental temperatures

Schematic of the influence of ambient temperature with HE (heat production) and IE (intake energy). RE is energy for production.

TABLE 12 Summary of Voluntary Food Intake of Beef Cattle in Different Thermal Environments15 to 25°C Preferred values as tabulated in Nutrient Requirements of Beef Cattle.

•5 to 15°C Intakes up 2 to 5 percent.

•-5 to 5°C Intakes up 3 to 8 percent. •-15 to -5°C Intakes up 5 to 10 percent.

•< - 15°C Intakes up 8 to 25 percent.

•Intakes during extreme cold (< -25°C) or during blizzards and storms may be temporarily depressed.

•Intake of high roughage feeds maybe limited by bulk.

TABLE 14: Water Requirements of Beef Cattle in Different Thermal Environments

•15 to 25°C 3 to 5 kg water per kg DM intake.

•Young and lactating animals require 10-50 percent more water.

•-5 to 15°C 2 to 4 kg water per kg DM intake.

•< -5°C 2 to 3 kg water per kg DM intake. •Increases of 50-100 % occur with a rise in ambient temperature following a period of very cold temperature, e.g., a rise from -20 to 0° C.

A = value adjusted for environment,B = diet component value from NRC feed composition table,Cf: correction factor (see below), andT = effective ambient temperature (°C).

ADJUSTMENTS TO FEEDING VALUES FORTEMPERATURE STRESS

A = B + B(Cf(T-20))

Cf for Effect of Temp on Diet ComponentDry matter 0.0016Energy components (ME, NE, TDN) 0.0010Acid detergent fiber 0.0037Nitrogen (crude protein) 0.0011

Example of Adjustment to the Feeding Value of Alfalfa Hay for Feeding to Beef Cattle Exposed to Warm (30C), Neutral (20C), and Cold (-5) Environmental Conditions

Temperature (°C) 30 20 - 5ME (Mcal/kg) 1.94 1.92a 1.87NEm (Mcal/kg) 1.14 1.13 1.11NEg (Mcal/kg) 0.40 0.40 0.39TDN (%) 53.5 53.0 51.7Digest protein (%) 11.5 11.4 11.1

a From Table 11, NRC, 1976a.

Net Energym = aW0.75

whereNEm = net energy for maintenance (Mcal/day),a = 0.077 for TNZ,W = live weight (kg).

For each °C prior exposure to ambient temperatures above or below 20°C, 0.0007 should be subtracted or added respectively to a in the above equation. Thus, for cattle with prior exposure to temperatures of 30, 20, 10, and 0°C, the value a becomes 0.070, 0.077, 0.084, and 0.091, respectively. This means that a 1400 lb cow at 0°C will need 18 % more net energy maintenance in her feed.

Adjustments can be made directly to the NEm and maintenance energy requirement values expressed in terms of ME or TDN by decreasing (for heat) or increasing (for cold) the tabulated values by 0.91 % for each °C the cattle have had prior extended exposure to conditionsabove or below 20°C.

Adjustments directly to NEm , ME or TDN

Lower Critical TemperatureNeed to make adjustments when ambient temp is below LCTLCT for Beef Cows is lower than for other livestockCold stress is generally not a practical nutritional problem in beef cattle

Cold Hardiness of Beef Cattle

Large sizeEffective thermal insulationLarge heat increment from digestion and metabolic processes

Storms and BlizzardsBigger Problem

Causes an immediate increase in energy requirementDepends on level of acclimatization

Cold Acclimatized Cattle

Increased metabolic rateEnhanced ability to increase their metabolic heat production

Calculating Actual LCT

Must be established to make nutritional adjustments for cold stress

whereLCT = lower critical temperature (°C),Tc = core temperature (°C) (39°C satisfactory assumption),I = total insulation, i.e., tissue plus external, (°C/Mcal/m2/day),HE = heat production (Mcal/m2/day), andHe = heat of evaporation (Mcal/m2/day).

LCT = Tc – I(HE – He)

HE = (ME – NEp)/AwhereHE = heat production (Mcal/m2/day),ME = metabolizable energy intake (Mcal/day),NEp = net energy for production (Mcal/day), andA = surface area (m2).NOTE: Surface area may be calculated from body weight according to thegeneral formula A(m2) = 0.09 kg0.75.

ME* = A(LCT –T)/IwhereME* = increase in maintenance energy requirement (Mcal/day),A = surface area (m2),LCT = lower critical temperature (°C),T = effective ambient température (°C), andI = total insulation, i.e., tissue plus external

TABLE 16 Estimates of Tissue and External Insulation for Beef CattleTissue Insulation (It )a It (°C/Mcal/m2/day)Newborn calf 2.5Month-old calf 6.5Yearling 5.5 to 8.0Adult cattle 6.0 to 12.0

External Insulation (Ie )b Ie (°C/Mcal/m2/day) in Relation to Coat DepthWind Speed(mph) <5 mm 10 mm 20 mm 30 mm <1 7 11 14 17 4 5 7.5 10 13.5 8 4 5.5 8 9 16 3 4 5 6.5

a Cattle in thin or emaciated body conditions and breeds with thin skins (dairy breeds and Bos indicus) have lower values than fat stock and breeds with thick skins (e.g., Hereford).

b Presence of moisture, wet snow, or mud in the coat could reduce Ie in affected areas by 50 to 80 percent.

Estimates of LCT , Increase in Energy Requirements of Beef Cattle Under Various ACUTE Stresses.

Increased Energy Environmental Stresses weight LCT °C per °C below LCT

Yearling Steer 300 kg -34.1 (-29.4) 0.202 1.3%Gaining 1.1 kg/dDry low wind

Yearling Steer 300 kg -9.5 (14.9) 0.310 2.0 %Gaining 1.1 kg/dWet snow, mud10 mph wind

Dry Pregnant cow 500 kg -25.0 (-13) 0.237 1.45 %Middle thirdDry low wind

Dry Pregnant cow 500 kg -7.3 (19) 0.334 2.04%Middle thirdWet snow 10 mph wind____________________________________________________________________

Recommendations

Feed More energy (~1.0 % more energy / drop in 1°C below 20 °C.

Protect cattle from wind (or ↑25%).

Wet and cold climates supply shelter and dry bedding (or ↑ 25%).

Recommendations

In Connecticut during Jan, Feb and March, beef cattle housed outside need to consume almost TWICE as much energy for maintenance.

Adjustments of Non Energy Components

Vitamin A requirement may increase with cold.Protein % may be decreased as feed intake increases to maintain amino acid requirements.Could increase roughage as heat increment will increase but don’t sacrifice performance for heat.

Problem: Evaluation for a 500 kg dry cow pregnant cow in the last third of pregnancy on a diet of brome hay. Two environmental situations have been

considered. Nonstressful conditions and a cold dry environment with seasonal temperatures of -15 ° C but during the past several days a winter

storm with air temperatures of -25 ° C, 10 mph winds, drifting snow and lack of suitable bedding or shelter.

nonstressful stressfulMaintenance energy requirement (Mcal ME/day)

adjusted for acclim temp 16.4 (table) 21.6 adjusted for direct cold stress 0.0 5.9

Total 16.4 27.5

Diet on dry matter basisenergy adjusted for conditions (ME/kg) 1.87 1.79feed required for maintenance (kg/day) 8.8 15.4

Calculations: 16.4 +(16.4 (.91%)(20-(-15))) = 21.6(.334)(-25-7.3) = 5.927.5/1.79 = 15.4 kg difficult to eat this much brome hay

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