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Studies on the Chemical Composition of the Blood of Dairy Cattle

II. The Effect of Phosphorus Intake on the Calcium and Inorganic Phosphorus Content of Whole Blood of Dairy Heifers during the Period of First Gestation and Lactation^*

West Virginia Agricultural Experiment Station, Morgantown, W. Va.

ABSTRACT

The calcium and inorganic phosphorus content of the whole blood of two groups of Holstein heifers has been studied during the periods of gestation and first lactation. One group was fed a normal phosphorus ration while the other was fed a ration low in phosphorus. Both groups received approximately the same amount of digestible crude protein and total digestible nutrients in proportion to body weight and the amount of milk produced.

From the results obtained under the conditions of the experiment outlined the following conclusions were reached.

1. An average daily intake of 11.8 grams of phosphorus (equivalent to 1.2 grams per 100 pounds of body weight) was sufficient to maintain the inorganic phosphorus in the blood at approximately the normal level during the period of first gestation.
   
2. There was a decided drop in the inorganic phosphorus of the blood at or immediately following parturition, which was much more pronounced in the case of the animals on the low phosphorus ration.
   
3. Milk production combined with low phosphorus intake caused a lowering of the inorganic phosphorus content of the blood.
   
4. The phosphorus in the feed should exceed the phosphorus in the milk by 9 to 10 grams per 1000 pounds body weight in order to maintain the inorganic phosphorus content of the blood for Holstein heifers producing 20 to 30 pounds of milk per day.
   
5. The lower level of phosphorus intake, gestation, and lactation had no appreciable effect on the calcium content of whole blood.
   

^* Published with the approval of the Director of the West Virginia Agricultural Experiment Station as Scientific Paper No. 164.

¹ Department of Agricultural Chemistry and Dairy Husbandry, respectively.

² Department of Agricultural Chemistry and Dairy Husbandry, respectively.