Page 163 - Calculating Agriculture Cover 20191124 STUDENT - A

CH 14] Calculating Agriculture 14-13

Dairy Cattle:
Grain or Concentrate Rations for dairy cows and heifers

Feed rations containing approximately 12% protein. For lactating cows that are fed good alfalfa,
soybean, or cowpea hay (at least 1 lb. per 100 lbs. live weight daily) with corn silage, sorghum silage, corn
fodder, sorghum fodder, or roots will require a minimum 12% ration. When alfalfa, soybean, or cowpea hay is
fed as the only roughage, merely a mixture of farm grain supplies sufficient protein for all except unusually high
producing cows.

Example A: Grain Mixtures for dairy cows and heifers, Calculate the DP% and TDN % of this ration.
Look up Perform
TDM: Total Dry Matter % Data from Table I Calculations
Feed TDM Pounds DP% TDN% DP# TDN#
Ground Corn, Dent #2 ....................... 85.0 1,160 lbs 6.7 80.1 77.72 929.16
Ground oats ....................................... 89.8 500 lbs 9.0 68.5 45.00 342.50 Look up values from Table 14.1
Wheat Bran, hard wheat .................... 90.5 220 lbs 14.1 67.5 31.02 148.50 and multiply by weights
Soybean oil meal, solvent 44% (or
Cottonseed meal) ............................. 91.0 100 lbs 42.0 78.0 42.00 78.00
Salt ..................................................... --- 20 lbs --- --- --- ---
———————————————————————
Total ................................................ 2,000 lbs --- --- 195.74 1498.16 Sum to Totals

Digestible Protein % = [ ΣDP# ÷ Total Weight ] x 100% = Avg DP %
Digestible Protein % = [ 195.74# ÷ 2000# ] x 100% = 9.8%

Total Digestible Nutrient % = [ ΣTDN# ÷ Total Weight ] x 100% = Avg TDN%
Total Digestible Nutrient % = [ 1498.16# ÷ 2000# ] x 100% = 74.9%
14
Solution algorithm:

1) Look up the feedstuffs in Table 14-1 Average composition and digestible nutrients for each. The
description and %TDM (Percent Total Dry Matter) will identify the correct feed. Record the
Digestible Protein Percent (DP%) and Total Digestible Nutrients Percent (TDN%) to the right of
the feedstuff of each.
Using Ground Corn, Dent #2 with a TDM of 85.0% has a DP% of 6.7%, expressed as a
decimal of 0.067 and a TDN% of 80.1% which expressed as a decimal is 0.801.
DP% TDN%
Ground Corn, Dent #2 ......... 85.0 1,160 lbs 6.7 80.1

2) Calculate the pounds of DP and TDN by multiplying the pounds of each feedstuff by their
recorded DP% and TDN% as decimals; place those answers under their DP# and TDN# column.

DP# = 1,160 # x 0.067 = 77.2 #
TDN# = 1,160 # x 0.801 = 929.16 #

3) Sum up for a Total DP# and TDN#: In this problem the Total Pounds of DP is 195.74 and the Total
TDN pounds is 929.16.

4) Calculate the DP % and the TDN % for the ration. Divide each, ΣDP# and ΣTDN# by the total
weight of the feed ration as stated.

Digestible Protein % = [ ΣDP# ÷ Total Weight ] x 100% = Avg DP %
Digestible Protein % = [ 195.74# ÷ 2000# ] x 100% = 9.8%

Total Digestible Nutrient % = [ ΣTDN# ÷ Total Weight ] x 100% = Avg TDN%
Total Digestible Nutrient % = [ 1498.16# ÷ 2000# ] x 100% = 74.9%
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