254 The Feeding of Animals 



a colt, it should be diluted and have its content of 

 milk sugar increased; or when lambs are given cow's 

 milk it may well be made richer, by the addition of 

 cream, perhaps. The milk of the cow varies with the 

 breed, the individual and the period of lactation, and 

 in its use for feeding purposes these variations should 

 be considered. While we have little or no data on 

 the subject, it is probable that the same causes op- 

 erate in affecting the milk of all species. 



Dairy by-products. These by-products are three 

 in number, skim -milk both from the gravity and the 

 separator processes, buttermilk, and whey. Their aver- 

 age composition, as taken from compilations by several 

 authors, is as follows: 



Composition of dairy offals (per cent) 



Total Casein and 



Water solids Ash albumin Sugar Fat 



Skim-milk, general average, Cooke... 90.25 9.75 .80 3.50 5.15 .30 



Skim-milk, gravity, Fleischman 89.85 10.15 .77 4.03 4.60 .75 



Separator-milk, Richmond 90.50 9.50 .78 3.57 4.95 .10 



Buttermilk, Cooke 90.50 9.50 .70 3. 5.30* .50 



Buttermilk, Vieth 90.39 9.61 .75 3.60 4.06t .50 



Whey, Cooke 92.97 7.03 .60 .93 5. .50 



Whey, Van Slyke 93.07 6.93 .60j .83 5.16 .34 



Skim -milk and buttermilk are not greatly unlike 

 in richness in solid matter or in general composition. 

 In case the skim -milk is sweet, buttermilk differs 

 from it because in the latter the sugar Has changed 

 partially or wholly to lactic acid. Whey is considera- 

 bly poorer in solids than the other dairy by-products 

 and also differs from them in the proportions of the 

 several constituents. 



* Probably includes the lactic acid, t.80 per cent lactic also present, f Assumed. 



