FEEDING UREA TO DAIRY COWS 11 



Table 11. — Average Rfproductive Performance of the "Continuous" 



Groups 



Days from Number of Days Calf Calves 



Calving to Services Re- Was Carried 



Next quired for while Cow Average Vigor 



Conception Conception Was Milking Weight^ at 



at Birth Birth 



8 6 8 Cows 8 6 8 6 8 Cows 

 Cows Cows Cows Cows Cows Cows 



Regular Ration 



1939 -* 93 2.0 -* 210 -* 87 Normal 



1940 106 102 1.5 157 151 100 98 Normal'^ 



1941 96 87 1.6 196 199 102 102 Normal^ 



Average, 



1940 & 41. 101 95 1.55 177 175 101 100 



Urea Ration 



1930 -* 105 2.1 -* 208 -* 100 Normal 



1940 74 78 1.5 185 174 101 104 Normal 



1941 119 121 1.5 174 170 101 100 Normal* 



Average, • — 



1940 & 41 97 100 1.50 180 172 101 102 



*Two of the eight cows were first-calf heifers in 1940; hence had no record in 1939, the year 

 before the beginning of the experiment. The averages for the six cows are given for each year as 

 well as the average for all eight. 



' Corrected for sex ratio. 



-One calf very weak at birth, posterior presentation; all others normal. 



'One cow aborted in the 5th month; all others had normal calves. 



''One calf born dead, two weeks premature; all others normal. 



In addition to the above, one cow on the regular ration had a retained placenta in 1941. 



Table 12. — Concentration of Urea in Blood and Milk 



Urea — mgm. per 100 cc. 



In Blood 



In Milk 



May '41 July '41 



Regular Ration 



"Double Reversal" group .' 27.8 23.5 25.9 



"Continuous" group 23.5 15.2 26.1 



Average 25.7 19.4 26.0 



Urea Ration 



"Double Reversal "group 25.7 25.7 25.9 



"Continuous" group 25.3 15.6 26.3 



Average 25.5 20.7 26.1 



Values given in the literature range from 30 to 50 mgm. for blood and from 11 to 43 mgm. for 

 milk. 



