GROWTH AND FATTENING 85 



In most cases the animals had not entirely finished their growth when 

 the tests began. The table shows that in 100 Ibs. of live-weight gain made 

 by the fattening ox, 7.7 Ibs. was lean-meat tissue, 66.2 fat, 1.5 mineral 

 matter, and 24.6 water. The sheep resembles the ox in character of in- 

 crease during fattening, but stores more mineral matter, due to the 

 growth of wool. The fattening pig stores little mineral matter. These 

 studies, as well as other investigations, show that the fattening of 

 mature animals is what the term implies the laying on of fat with but 

 relatively little storage of protein. 



Animals which are fattened while still growing will gain not only in 

 fatty tissue, but also in lean meat. This is shown by the experiments of 

 Waters, Mumford, and P. F. Trowbridge, 19 who analyzed the entire 

 bodies of steers killed at various stages of fattening at the Missouri 

 Station. The following fable shows the composition of the carcass of a 

 748-lb. steer in thrifty growing condition and the composition of the gains 

 made by other steers during fattening : 



Composition of unf aliened steer and gains during fattening 



Water Fat Protein Ash 



Per ct. Per ct. Per ct. Per ct. 



Carcass of unfattened steer 56.4 18.6 18.8 5.7 



First 500 Ibs. of gain 37.6 48.6 11.9 2.0 



Second 500 Ibs. of gain 17.8 75.6 5.2 1.5 



Total 1,000 Ibs. of gain 27.7 62.1 8.5 1.7 



While the carcass of the steer killed before fattening was over half 

 water, the first 500 Ibs. of gain contained only 37.6 per ct. water and 

 the second 500 Ibs. but 17.8 per ct. The first half of the gain was 48.6 

 per ct. fat and 11.9 per ct. protein, showing marked increase in lean 

 meat. In the last half of the gain 75.6 per ct. was fat and only 5.2 per 

 ct. protein. The storage of ash was likewise less in the last 500 Ibs. of 

 gain. Thus, as a partly mature animal fattens it progressively makes 

 less growth in lean meat and skeleton, and a larger part of the gain is fat. 

 This fact is of much practical importance in finishing meat animals 

 for the market, for it is the primary reason why the feed cost of 1 Ib. of 

 gain increases rapidly after an animal has become fairly well fleshed. 

 The fat animal also requires a greater proportion of its feed for main- 

 tenance than one which is not yet well fleshed, on account of two differ- 

 ent factors. First, the maintenance requirement of a fat animal per 

 1,000 Ibs. live weight is higher than for a thinner one ; and second, the 

 fat animal eats less feed per 1,000 Ibs. live weight, consequently having 

 less nutrients left for meat production after the maintenance require- 

 ments have been met. 



124. Composition of steers of different ages. For several years Haecker 

 of the Minnesota Station 20 conducted extensive investigations on the 

 food requirements of steers of different ages, in which he had analyzed 

 the entire carcasses of many animals. The following table shows the 



"Information to the authors. See also Mo. Res. Bui. 30. 20 Minn. Bui. 193. 



