774 
Journal of Agricultural Research 
Vol. XXXI, No. 8 
the region. The trouble can be largely corrected, if not altogether 
removed, by mixing small doses of potassium iodide with the feed 
of pregnant sows, ewes, does, cows, etc. 
The foregoing researches constitute the chief contributions of 
recent years to the subject of the mineral requirements of farm 
animals. Although they have done much to advance the knowledge 
of the subject, there yet remain many phases of it to be investigated. 
The investigations with cows have for the most part been metabolism 
experiments, which of necessity can be conducted for only relatively 
short periods of time. Long-time experiments on the effect of feed¬ 
ing mineral supplements to milking cows are not recorded in the 
literature. Forbes, in his most recent paper on the subject (5), 
remarks that “The advantage to be derived from the feeding of 
mineral supplements seems to us doubtful, but . . . that the possi¬ 
bilities of benefit from so doing should be thoroughly investi¬ 
gated . . .” In a recent report of the subcommittee on animal 
nutrition of the National Research Council (10) occurs the following 
paragraph: 
An important problem in this field is to determine, by carefully controlled, 
long-time feeding experiments with dairy cattle, under conditions of practice, 
the effect of differences of intake of mineral nutrients, especially as contained 
in leguminous as compared with gramineous roughage, and in mineral supple¬ 
ments, on growth and productive efficiency. 
Such an investigation has been in progress at this station for the 
past two and one-half years and is still being conducted. This paper 
constitutes a report oi progress on the project up to May 1, 1924. 
SCOPE, METHODS, AND RESULTS OF THE INVESTIGATION 
OUTLINE OF THE PROJECT 
In brief, the essentials of the investigation have been as follows: 
(1) Feeding to the station dairy herd of a ration as deficient in 
calcium and phosphorus as it has been possible to formulate from the 
roughages and concentrates available, but at the same time adequate 
in other respects. 
(2) Division of the herd into two halves as nearly identical as the 
individuality of the animals would permit, and the addition to the 
grain ration of one of these groups (always the same group) of sup¬ 
plemental calcium phosphate in the form of a special steamed bone 
meal, the amount varying from 3 to 8 ounces daily, depending on the 
weight and milk yield of the cow. 
(3) Observation of the effects of the mineral supplement upon: 
(a) The general condition of the animals .as apparent to the 
eye and as revealed by handling. 
(b) Body weight. 
(c) MilK production. 
(d) Composition of the milk, especially its content of calcium 
and phosphorus. 
(e) Reproduction, under which general heading have been 
observed: 
(1) Recurrence of oestrum. 
(2) Difficulties in getting cows to breed. 
(3) Such abnormalities as abortions, retained pla¬ 
centas, etc. 
(4) Condition of the calves at birth and subsequently. 
