A STUDY OF THE PHYSICAL CHANGES IN FEED RESI- 

 DUES WHICH TAKE PLACE IN CATTLE DURING DI- 

 GESTION 



By P. V. EwiNG, Animal Husbandman, Texas Agricultural Experiment Station, and 

 L- H. Wright, Assistant Professor of Physiology and Pharmacology, School of Veteri- 

 nary Medicine, Texas Agricultural and Mechanical College 



INTRODUCTION 



The data reported in this paper were obtained by the senior writer and 

 others at the Georgia Agricultural Experiment Station in making studies 

 on the rate of passage of feed residues through the steer and its influence 

 on digestion coefficients.^ Most of the investigations on digestion in 

 cattle have been made from a chemical rather than from a physical 

 standpoint, yet the importance of the part physics plays has been fre- 

 quently referred to.^ This report covers the physical changes which took 

 place in the rations studied during the process of digestion and covers 

 these changes with relation to the several organs and steps in digestion 

 rather than the process of digestion as a whole. 



METHOD OF CONDUCTING THE INVESTIGATION 



Animals. — The animals used in this work were high-grade 3-year-old 

 Tennessee-bred Shorthorn steers. They had been used in the nutrition 

 studies^ in the winter of 191 5-1 6, after which they were killed late in 

 the spring of 191 6 when slaughter tests were made. 



Feeds. — Com silage and cottonseed meal especially prepared were the 

 feeds used in these experiments. The corn silage was prepared by having 

 the ears pulled oflf before it went into the silo. While this resulted in a 

 higher percentage of fiber and a lower percentage of nitrogen-free extracts 

 and other nutrients, it had the desired mechanical properties. Silage 

 that would not pass through a 2 -mm. screen was wanted. The meal was 

 of the best quality. It was prepared by first passing it through a 1 5 -mesh 

 screen and later through^^a 20-mesh screen. This removed all except the 



1 EwiNG, P. v., and Smith, F. H. a study of the rate of passage of food residues through thB 

 STEER AND its iNFtuENCE ON DIGESTION coEFFioENTS. In Jour. Agr. Research, lo, no. 2, p. 55-63. 1917. 



2 Smith, R. M. the physiology of the domestic animals, p. 337. Philadelphia, 1889. 



* EwiNG, P. v., Wells, C. A., and Smith, F. H. the associative digestibility of corn silage and 

 cottonseed meal in steer rations. Pt. 2. Ga. Agr. Exp. Sta. Bui. 125, p. 149-164, r fig. 1917. 



Journal of Agricultural Research, Vol. XIII, No. 12 



Washington, D. C. June 17, 1918 



ax Key No. Tex.-2 



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