how2cap

How To - Calculate Ca and P in Rations

Always calculate PHOSPHORUS first

Calculate the amount of Dical (or other P source) by:

Calculating the amount of P present from each feed in the diet; do that by:

Multiply each feed by the %P in that feed. Sum the results

Subtract the amount of P present from the amount needed.
Obtain the remaining P needed from dical, by dividing the amount of P needed by the % P in Dical (18.5%)

Algebraically:

Let X stand for unknown amount of Dical. Assume Corn and SBM are the feeds in the ration.
P needed = (Lbs Corn) * (% P in Corn) + (Lbs SBM) * (% P in SBM) + (X) * (.185)

Calculate CALCIUM second

Calculate the amount of Limestone (the calcium source) by:

Calculating the amount of Ca present in each feed in the diet, including DICAL; do that by:

Multiply each feed by the % Ca in that feed. Sum the results

Subtract the amount of Ca present from the amount needed
Obtain the remaining Ca needed from Limestone, by dividing the amount of Ca needed by the % Ca in Limestone (38%).

Algebraically:

Let X stand for the unknown amount of Limestone. Assume Corn, SBM and DICAL are now the feeds in the ration.
Ca needed = (Lbs Corn) * (% Ca in Corn) + (Lbs SBM) * (% Ca in SBM) + (Lbs Dical) * (% Ca in Dical, typically 22%) + (X) * (% Ca in Limestone, 38%)

EXAMPLE

Suppose the ration you are balancing contains 80% corn and 17% SBM. Analysis is shown below. The requirement for Ca is 0.6% and for P is 0.5%. How much Dical and Limestone should you use?

Feed	% Ca	% P
Corn	0.02	0.28
SBM	0.25	0.60
Dical	22.0	18.5
Limestone	0	38

PHOSPHORUS:

0.5 = (80)(.0028) + (17)(.006) + (X)(.185)

0.5 = 0.224 + 0.102 + 0.185X

0.5 - 0.224 - 0.102 = 0.185X

0.174 = 0.185X

0.174 / 0.185 = X

0.94 = X = Lbs. Of Dical

CALCIUM:

0.6 = (80)(.0002) + (17)(.0025) + (0.94)(0.22) + (X)(0.38)

0.6 = 0.016 + 0.0425 + 0.2068 + 0.38X

0.6 - 0.016 - 0.0425 - 0.2068 = 0.38X

0.3347 = 0.38X

0.3347 / 0.38 = X

0.88 = X = Lbs. Of Limestone

Trace Minerals, Salt, Vitamins

Add prepared, commercial premixes at the recommended level for which they were formulated. The information for that will be on the feed tag.

Vitamins are often formulated to be added at about 0.5% of the ration

Trace Minerals may be as concentrated as 1 pound per Ton, or 0.05% of the ration.

Salt is typically added at 0.5% of many rations, though growing/finishing pigs only need 0.25% salt.