158 MASS. EXPERIMENT STATION BULLETIN 255 



One calf died in utero at about the sixth or seventh month stage as a result of 

 cervical and general uterine infection in the dam. This was in the "non- 

 mineral" group. 

 Apparently the cows that received the mineral supplement were a little closer 

 to normal in their reproductive function than those that did not receive it. They 

 came in heat a little sooner after calving, recurrence of heat was slightly more 

 regular, and they bred a little more readily. Other irregularities were about 

 evenly divided between the two groups. In any case the reproductive troubles 

 have not been greater than are ordinarily encountered in practical herd manage- 

 ment. 



The condition of the calves at birth and subsequently is also of interest in this 

 connection. Twenty-six calves have been dropped in the herd during the course 

 of the experiment. Classification of these according to group and condition 

 appears below. 



Vigorous Good Fair Delicate 



Mineral group 3 9 1 1 



Non-mineral group 3 5 4 



The main difference hei-e is seen to be in the "good" and "fair" groups. The 

 statistics undoubtedly favor the "mineral" group but they need to be examined 

 as to the make-up of the groups with respect to sex and breed, as these determine 

 to a considerable extent the apparent vigor of a calf. Bulls are usually more 

 lusty than heifers; Holsteins are generally more rugged than Jerseys. 



Of the four "fair" calves in the "non-mineral" group three were heifers, and the 

 fourth, although a bull, was a Jersey. On the other hand, of the nine "good" 

 calves in the "mineral" group, six were heifers, and three of these heifers were 

 Jerseys. These situations just about offset each other so that the balance is still 

 somewhat in favor of the "mineral" group. It would seem that the cows receiv- 

 ing the mineral supplement produced on the whole somewhat better calves. It 

 must be stated, however, that some very fine calves have come from the cows that 

 have not received the supplement. 



Summary and Conclusions 



The object of this work has been to determine the value for dairy cows of a 

 mineral supplement consisting of 80 per cent di calcium phosphate (precipitated 

 bone) and 20 per cent carbonate of lime (ground limestone) added to a ration 

 supposedly deficient in lime. Previous work with tricalcium phosphate in the 

 form of steamed bone meal as a source of lime and phosphorus showed little, 

 if any, advantage in supplying these elements in that form. As dicalcium 

 phosphate is somewhat more soluble and had given better results elsewhere with 

 lambs and goats than the tricalcium phosphate, it was thought worthy of a trial 

 with cows. 



A special effort was made to have the basal ration of the cows as deficient in 

 lime as possible. To this basal ration there was added for half of the herd (known 

 as the "mineral" group) sufficient of the phosphate-carbonate mixture to the- 

 oretically make good the deficiency. The experiment was carried on for two years 

 with the following results: 



1. All the cows in the herd maintained their general condition well. The 

 mature cows that received the mineral supplement maintained themselves slightly 

 better in this respect than did those not receiving the supplement. They also 

 made a considerable gain in weight while the "non-mineral" group showed little 

 change. 



