Oct. 15, 1925 Calcium Phosphate as Supplement to Dairy Ration 
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METHODS OF EXPERIMENTATION 
General Procedure 
The station herd is made up of high-grade Holsteins and Jerseys, 
and usually numbers, including young stock, about 18 to 20 head. 
At present there are 20 animals included in the experiment, 15 milk 
cows, 3 yearling heifers, and 2 eight-months-old heifers. 4 There 
have of necessity been some changes in the herd since the experiment 
was started, but of the 19 individuals originally included, 13 are still 
in the herd. Since the commencement of the experiment in Decem¬ 
ber, 1921, the milking herd has had an average annual production 
E er cow of 8,200 pounds of milk, testing 4.52 per cent of fat. The 
erd is maintained for the most part by raismg the heifer calves; 
only occasionally are any cows purchased. 
All the herd is housed in a well-lighted, well-ventilated stable, and 
except in inclement weather receives daily exercise in adjacent yards. 
Up until last year all cows dry during the pasture season have been 
sent to pasture regularly for a period of four to six weeks. For 
reasons outlined later, this practice is no longer followed, only the 
young stock being pastured. All cows are given a two-months’ dry 
period, during which time they are liberally led. The aim is to have 
the cows freshen in the autumn whenever possible, but this is a matter 
which is difficult to regulate in practice. The cows are maintained 
on dry feed the year around, except for a period commencing about 
June 25 and ending about October 10, during which time they are 
fed such green soiling crops as oats, millet, sorghum, and fodder corn 
as a substitute for a portion of their hay. No ensilage or roots are 
fed. Running water is before the cows at all times, and salt is fur¬ 
nished to the extent of 0.75 per cent of the grain ration. The cows 
are fed and milked twice daily (at 7 a. m. mid 5 p. m.); each cow’s 
daily ration is carefully weighed out—the hay into 4-bushel baskets, 
the grain into suitable trays. The milk is weighed and accurate 
records kept of the production of each cow and the cost of the feed. 
Composite samples of every lot of hay and grain purchased are taken 
regularly, and the milk is sampled once each month for five consecu¬ 
tive days. The composite samples are analyzed as outlined later on 
in this paper. 
All animals are weighed on the 1st and 2d of each month, and their 
rations adjusted according to their body weights and the amounts of 
milk they are giving. The standards for digestible nutrients em¬ 
ployed in formulating and adjusting the rations are:] 
For mature cows,* Haecker’s standard for the aged cow (12 , p. 56-57). 
For heifers that have had one calf, Haecker’s standard for heifers (11, p. 107). 
For heifers previous to their first calving, Armsby’s standard for maintenance 
and growth in the dairy breeds ( 1 , p. 713). 
The standard adopted for calcium and phosphorus requirements of 
all the animals has been that proposed by Kellner (20, p. 618 ), founded 
in part on the observations of Henneberg (18, p. 58) and in part on 
Kellner’s own work. This standard calls for a daily minimum of 100 
grams of calcium oxide (CaO) and 50 grams of phosphoric acid 
TP2O5) for each 1,000 kg. of live weight, for maintenance only. In 
addition, for each 20 kg. of milk produced, there must be supplied 
4 All heifer calves are included in the experiment as soon as old enough to subsist on hay and dry grain. 
The age varies with the calf from 5 to 7 months. 
