142 



MASS. EXPERIMENT STATION BULLETIN 230 



Large a^ dam Smaller than dam 



Bone meal— 3 (2H & IJ) Bone meal— 3 (IH & 2J) 



No bone meal— 3 (2H & IJ) No bone meal— 3 (2H & IJ) 



So far, then, as growth records go the evidence is about evenly divided, 

 there being nothing in favor of the bone meal. 



Milk production 



The milk yield has remained at a fairly constant average level all through 

 the experiment. The average daily yield per cow from year to year is given 

 below, commencing two years before the experiment ivas started. 



Average daily yield 



Year of milk per cow, lbs. 



1920 21.87 



1921 21.65 



1922 22.67 



1923 21.56 



1924 21.06 



1925 22.30 



The above record is for the whole herd. Dividing the herd into the two 

 groups, tiiose that received bone meal and those that did not, we find the 

 following records: 



Year Average daily yield of milk per cow, lbs. 



1922 

 1923 

 1924 

 1925 



On this basis it would seem that the cows not receiving bone meal were the 

 better producers. When we subjected our data to careful analysis, studying 

 the records of the individual cows from year to year, and took into account 

 the influence of breed, age, and length of lactation on the milk yield of the 

 two groups, it was found that the evidence is not so favorable to the "no bone 

 meal" group. In fact, it favors slightly the "bone meal" group of cows. 



Composition of the Milk. 



The milk from each cow in the herd is sampled for live consecutive days 

 each month. Total solids and fat have been determined in the composite 

 samples each month during the course of the experiment. In addition the 

 total ash, and calcium and phosphorus content of tlie milk have been deter- 

 mined from time to time,^on an average, about four times a year. 



