MILK PRODUCTION 525 



The results show distinct effects of certain feeding stuffs on 

 the milk yield which were apparently quite independent of the 

 supply of digestible nutrients or of energy values, or of the pro- 

 tein supply, and which were consistent when the experiments 

 were repeated. 



Hansen 1 distinguishes three groups of these feeding stuffs. 

 Those of the first group, including " maizena " (apparently 

 gluten feed), maize and oats, increase the quantity of milk but 

 depress the percentage of fat, so that the total yield of fat is not 

 materially changed. Those of the second group, including 

 palmnut meal, cocoa residues, maize distillers' grains, and to a 

 less degree linseed and cottonseed meal and the legumes, in- 

 crease the total yield of fat without materially affecting the 

 quantity of milk, so that the percentage of fat in the milk is 

 increased. Those of the third group, including poppy cake, 

 " false flax " 2 cake, rice feed and to a less degree sesame cake, 

 diminish the yield of fat but do not sensibly affect the quantity 

 of milk, so that the percentage of fat is decreased. 



In a subsequent investigation 3 on substantially the same plan, 

 Hansen has compared the effects of palmnut cake containing 

 respectively 5.55 and 12.42 per cent fat when fed in different 

 amounts. He concludes that the specific effect increases with 

 the proportion of palmnut cake in the ration and with the per- 

 centage of fat contained in the cake. He finds that to secure 

 significant results in practice, about 2 pounds per 1000 pounds 

 live weight of fat-rich cake and 2^ to 3 pounds of the poorer 

 grades are necessary. Different individual animals have dif- 

 ferent degrees of susceptibility to the effects of palmnut cake 

 but the result can be obtained if sufficient is fed. 



The principal criticism to be made of Hansen's experiments 

 is that the experimental periods were so short usually 7 days 

 preliminary and 7 days for the experiment proper. It is not 

 an unusual experience in dairy feeding experiments to see a 

 change of rations followed by a temporary stimulation of the 

 milk production which is not sustained, and the question natu- 

 rally arises whether the " specific " effects which seem to be 

 demonstrated in the first week or two would have continued 

 for a longer tune. 



1 Loc. cit., Bd. 40, pp. 187-188. * Camelina Sativa. 



3 Landw. Jahrb., 47 (1914), 30. 



