1019] 



ANIMAL PRODUCJTIOlSr, 



769 



Pride of Invershie, Elba, Jilt, ami Pride of Aberdeen, for special mention on 

 account of the noteworthy qualities of their descendants. 



Determining the age of cattle by the teeth, G. W. Pope (U. S. Dept. Agr., 

 Farmers' Bui. 1066 (lOlD), Pi)- i, Pus. 6). — A series of cuts is given showing 

 the appearance of the internal face of the incisors of cattle shortly after birth 

 and at the ages of 2, 3, 4, 5, and 12 years. There is a brief explanatory text. 



The availability of the energy of food for growth, C. R. Moulton {Jour. 

 Biol. Chem., 31 {1911), No. 2. pp. 3S9-39Jt) .—To study the utilization for beef 

 liroduction of metabolizable energy derived from the feed and not needed for 

 maintenance, two mature beef steers at the Missouri Experiment Station were 

 fattened immediately after they had been subjected to a prolonged maintenance 

 trial in a thin condition. The feeds offered — corn chop and linseed meal (8:1), 

 and alfalfa hay to the extent of 40 per cent of the grain ration — were the same 

 in kind and proportion as during maintenance. The data from a digestion ex- 

 periment with these feeds and the maintenance trial have been published (E. 

 S. R., 33, p. 569). the animals being included in the "regular-maintenance" 

 group. In estimating the energy requirement for maintenance from the results 

 for the thin steer it was assumed that the energy required is propotional to 

 the five-ninths power of the body weight, in accordance with previous determi- 

 nations of the author (E. S. R., 35, p. 64). The metabolizable energy of the 

 feed was computed from the chemical composition by the Armsby method and 

 was found to be 1.72 therms per pound of digestible organic nutrients. 



One steer (No. 121) was slaughtered when iu full prime condition and the 

 other (No. 48) when 40 to 50 days under prime. Proximate analyses were made 

 of the dressed carcasses. A third steer (No. 18) which had also been on the 

 maintenance trial, was slaughtered at the beginning of the fattening period. 

 The percentage comiwsition of its carcass was taken as the initial percentge 

 composition of the other two steers, and in this way the chemical constitution 

 of the gains made by the latter are estimated. It was assumed, using average 

 data of other workers, that the thermal equivalents of the protein and of the fat 

 in the gains were respectively 5.6776 and 9.4889 calories per gram. 



The main results are assembled in the following table : 



Recovery of available energy in fattening steers. 



It is pointed out that about tlie same proportion of the available energj' was 

 recovered in both the vex-y fat and the medium fat steer. The former, howevei-, 

 had 5.06 therms while the latter had only 3.98 therms available for each pound 

 of gain, a difference explained by the higher proportion of fats in the gains of 

 the latter. 



It is estimated tliat if the grain and alfalfa hay of Armsby and Fries' experi- 

 ments (E. S. R., 33, p. 72) had been fed in the same proportions as in those 



