PROTEIN REQUIREMENTS OF CATTLE: MITCHELL 49 



of \) fetuses, of dillorciit ages, with their meinhraiies. The amniotic fluid 

 was collected, but its nitrogen content was not determined. Through 

 the courtesy of Professor Yapp, these unpuhlishcd data have been made 

 available for this stud}' of the protein requirements for intra-uterine 

 growth. 



TABLE 24 



Age and Breeding of Bovine Fetuses Analyzed bv W. W. Yai'p 



Fetus Age from date of 

 Xo. breeding days nam Sire 



718 91 F2 Holstein-Guernsey cross Pure-bred Guernsey bull 



2 95 Grade Holstein " " Holstein " 



26 95 Holstein-Guernsey back-cross to Hoi- '' " Guernsey " 



stein sire. 

 21 104 Holstein-Guernsey back-cross to Hoi- " " '' " 



stein sire. 



27 123 Holstein-Guernsey back-cro.ss to Hoi- '• " " " 



stein sire. 



1 162 Holstein-Guernsey back-cross to Hoi- " '' " " 

 stein sire. 



644 162 F, Holstein-Guernsey cross " " " " 



11 167 Grade Holstein " " Holstein " 



19 186 Grade Holstein " " " " 



TABLE 25 



The Protein Content of Bovine Fetuses of Different Ages, 

 FROM Data Secured by W. W. Yapp 



The fetuses were obtained from grade Holstein and Holstein-Guernsey 

 cows slaughtered at varying periods after being bred either to a pure- 

 bred Holstein bull, in the case of the Holstein cows, or to a pure-bred 

 Guernsey bull, in the case of the cross-bred cows. The description of 

 the fetuses is contained in Table 24 and data relating to their nitrogen 

 content will be found in Table 25. Fetuses Nos. 2, 11 and 19 were sired 

 by the same bull, as were the remaining six. 

 4 



