Table 6. Suggested Levels of Grain Feeding for Complete Lactation 

 In Relation to Grain-Mi.k Price Ratiol^ 



Pounds of Milk Produced 

 Requiring One Pound of Grain 



^Estimates based on Jensen, et al., op. cit., and on Kitchen, et al., Cous — Hay Burners or Grain 

 Burners (mimeo.) New Jersey Agr. Expt. Sta. 



^Derived by dividing the price of 100 pounds of grain by the price at the farm of 100 pounds of milk. 



Milk Production Rates for Raised and Purchased Cows 



Records of milk production for raised and purchased cows were taken 

 from New Hampshire Dairy Herd Improvement Association herd books 

 for 25 farms. A total of 358 records of 305-day lactations were used. For 

 each record for a raised cow, a similar record was obtained for a pur- 

 chased cow of the same breed in the same herd that freshened on the 

 same date. The paired production records for raised and purchased cows 

 were converted to a 4-percent fat-corrected basis. 



The levels of milk output of pairs of raised and purchased cows in 

 the same herd and in the entire sample were compared. Although pro- 

 duction of raised and purchased cows varied considerably in individual 

 herds and among herds, there appeared to be no consistent pattern of 

 superiority of either raised or purchased animals (Figure 3). The average 

 production of 4-percent fat-corrected milk for all purchased cows and 

 all raised cows was about the same. Purchased cows produced on the aver- 

 age 10,608 pounds of 4-percent fat-corrected milk while raised cows produced 

 on the average 10,216 pounds. The difference of 392 pounds of milk in favor 

 of the purchased cows was not significant when tested statistically; it could 

 have occurred by chance.''* The average level of production of 4-percent fat- 

 corrected milk for raised cows exceeded that of purchased cows in 10 of the 

 25 herds in the sample. 



As purchased cows averaged 2.4 years older than raised cows, the 

 production records were further corrected to a mature-cow equivalent 

 basis to obtain better comparison of the quality of cows, as reflected in 

 production of milk. Differences in production between raised and purchased 

 cows still existed (Figure 4), but the distribution of the production of 

 purchased cows v,as similar to that of raised cows. The average production 

 (mature-cow equivalent) for the group of raised cows was 11,272 pounds of 

 milk, and production of the purchased-cow group averaged 11,189 pounds 

 of milk. The difference in production of 83 pounds of milk, however, when 



5 A Student's t test was used and the difference in average production was not 

 significant at the 5-percent level. 



15 



I 



