482 NUTRITION OF FARM ANIMALS 



and work periods, beginning with a rest period, so that each 

 work period was preceded and followed by a rest period. 



The rather moderate amount of work performed caused some 

 decrease in the volume of milk produced, the effect tending to 

 be a little greater in the periods in which most work was done. 

 The decrease, however, was chiefly a decrease in the amount 

 of water secreted, although a slight diminution in the yield of 

 total milk solids, ranging from 10 to 85 grams per day, was ob- 

 served. In other words, the effect of the work was to render 

 the milk somewhat more concentrated. The most notable 

 effect, however, was upon the yield of, fat, which showed an 

 actual increase in every case but two. This increase was com- 

 pensated for by a decrease of the fat-free solids, so that analyses 

 of the milk showed a higher percentage of fat and of total solids, 

 while the percentage of fat-free solids remained practically un- 

 changed. 



578. Confirmatory results. Quite similar results, although 

 obtained in some cases by less rigorous methods, have been 

 reported by Domic, 1 Stillich, 2 Backhaus, 3 Torssell 4 and Dol- 

 gich. 5 



Observations by Sturtevant, 6 Henkel 7 and Hills 8 upon the 

 effect of fatigue on the yield and composition of milk are also 

 in accord with the results of experiments upon work and ex- 

 ercise in showing a tendency to reduce the quantity of milk 

 and at the same time to increase both the percentage and the 

 actual yield of fat. 



Aside from the question of the effects of overexertion, it 

 appears clear that a considerable amount of work may be per- 

 formed by cows without any serious diminution of the volume 

 of their milk and with an actual increase in the yield of fat, its 

 most valuable ingredient. The lightest work in Morgen's 

 experiments was roughly equivalent to hauling a load of a ton 

 if miles over a smooth level road. This is certainly much more 

 labor than the ordinary cow will perform when turned loose in 

 a comfortable yard or paddock. 



1 Milch Ztg., 25 (1896), 331- 2 Jahresber. Agr. Chem., 39 (1897), 529. 



3 Centbl. Agr. Chem., 28 (1899), 492; Expt. Sta. Rec., 10 (1899), 85. 



4 Expt. Sta. Rec., 12 (1901), 381. 5 Jahresber. Tier Chem., 33 (1904), 382. 

 6 N. Y. (Geneva) Expt. Sta., Rpt. 1882, p. 25. 



7 Landw. Vers. Stat., 46 (1896), 329. 



8 Vt. Expt. Sta., Rpts. 1894, p. 162, 1898, p. 367 and 1899, p. 309. 



