20 X. H. Agr. Experiment Station [Bulletin 313 



ences have on production is still to be determined. K. S. Morrow- 

 supervised this work. (Bankhead-Jone,^ Offset Fund) 



Variability in Milk Solids-Not-Fat 



Although the university is said to have had exceptionally good 

 pasture seasons in the years 1937 and 1938, the average solids-not- 

 fat percentage in the milk did not increase to its high level of the 

 previous two years. H. C. Moore, who is in charge of this project, 

 reports that for the year April, 1937, through March, 1938, the fat 

 content increased 0.17 per cent over the i)revious year and the solids- 

 not-fat decreased 0.11 per cent. This is puzzling because it has been 

 believed that the solids-not-fat-content of milk increases as the fat 

 content increases. When we compare the university data with that 

 compiled from approximately 50 herds supplying a commercial milk 

 plant in central New Hampshire, we lind about the same abnormally 

 low solids-not-fat content for the year 1937-38. 



Comparisons will have to be continued for some years before defi- 

 nite conclusions can be drawn ; but it is obvious that there is a 

 decided variation in both fat and solids-not-fat content in the milk 

 produced on the same farm from year to year and one year cannot be 

 taken as an indication of the composition of the milk from any one 

 farm or group of farms. 



According to comparison studies on the daughters of various 

 dams and sires, inheritance is an important factor in determining 

 the composition of the milk given by a herd. {PurneU Fund) 



Controlling Contagious Abortion in Cattle 



Experiments under the direction of C. L. Martin continued as pre- 

 viously to see how long calves vaccinated with a Bang's disease 

 vaccine would react to the standard tube agglutination blood test. 

 The previous years' findings were substantiated to the effect that if 

 calves are vaccinated between the ages of four to six months, the 

 majority of them will give a negative blood test before a year has 

 passed following the inoculation. A few, however, will not give this 

 desired negative reaction. The inoculation did not give 100 per cent 

 protection against abortion, since two abortions occurred in heifers 

 previously inoculated. {PurneU Fund) 



Control Bovine Mastitis through Prevention 



L. W. Slanetz, C. L. Martin and K. S. Morrow have been working 

 on this problem cooperatively, approaching it from the viewpoint of 

 bacteriologist, veterinarian and dairyman, respectively. Surveys 

 conducted during the past three years show that the disease is preva- 

 lent in many New Hamjjshire herds. Out of a total of 243 cows 

 tested in 12 herds from different parts of the state, 92 animals, or 38 

 per cent, showed mastitis infection. Applying this rate of infection 

 to the aiiproximatoly 80,000 milking cows in the state, it is estimated 

 that more than ;>0,000 cows are infected with mastitis. 



The diagnosis of this disease is not always simple. The strip cup 

 and brom thymol blue tests are of practical value in instituting a 

 l)ai-tial control i>rogram : but in order to detect all cases of mastitis in 

 a herd, bacteriological analysis of milk sami)les has been found neces- 

 sary. It has been found that composite sami)les can be employed for 

 diagnosis, which greatly reduces the labor, time and materials neces- 



