The Level of Inorganic Phosphorus in the Blood of Dairy Cattle

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Abstract
Inorganic phosphorus was determined in the whole blood of over 200 cattle—mostly cows and heifers—in normal states of health and nutrition. The inorganic phosphorus of the blood of immature cattle diminished with increase in age in an approximately regular manner. As to the effect of age on inorganic blood phosphorus values of milking cows, no such effect was observed as between cows 2 to 3 years old compared with cows 4 to 5 years old, but aged cows had significantly less inorganic phosphorus in their blood than did middle aged cows. The effects of lactation on inorganic blood phosphorus were questionable. No influences of the breed of cow or of the kind of roughage consumed on inorganic blood phosphorus values, were observed. The average inorganic phosphorus content of the blood of sixty-four milking cows was 4.33 mg. ± 0.04 mg., with a standard deviation of 0.59 mg. per 100 ml. The corresponding value for dry cows was approximately the same.