FEEDING MII^K cows 467 



For example, suppose the .results with the standard ration 

 during the first and fifth period of 20 days each, are as follows : 



First period, average 14.27 kg. milk and 4.38 grams fat per day 

 Fifth period, average 13 63 kg. milk and 4.22 grams fat per day 



Decrease 0.64 kg. 0.16 kg. 



From the middle of the first to the middle of the fifth period is 

 So days, or four periods. The decrease is thus 0.16 kg. milk 

 and .04 grams fat for each period, and if the same ration were 

 continued, the daily production for each period should be : 



Period i (found) 14.27 kg. milk and 4.38 grams fat per day 



Period 2 (calculated) 14.11 " " 4.34 " " 



Period 3 13.95 " " 4.30 " 



Period 4 13-79 " " 4.26 " 



Period 5 (found) 13.63 " " 4.22 " " 



The actual production with the ration being tested during the 

 intermediate periods is compared with the calculated production. 

 For example, if the production is 13.00 kg. milk and 4.10 grams 

 fat in period 2, the ration fed has decreased the production i.n 

 kg. milk and 0.24 grams fat. 



This method assumes a regular decrease in the production dur- 

 ing the period of lactation. This assumption may or may not be 

 true with one or two animals, but with eight or ten cows, it is 

 practically true. 



The difference in the condition of the animal due to the 

 previous feeding also has some effect upon the quantity and 

 quality of the milk. 



Group System. This corresponds to the group system for fat- 

 tening experiments. Each cow should be matched in race, age, 

 weight, period of lactation, quantity and composition of milk 

 against similar animals in the other groups. The groups are fed 

 alike for a preliminary test period of 30 to 60 days, during which 

 the yield and composition of the milk is estimated. If any 

 differences in the groups appear, the cows should be rearranged, 

 or new animals brought in, and another test made. When each 

 group makes the same production with the same ration, the ex- 



