Effects of Frequency of Feedingo on Excretion of Chromic Oxide, Crude Protein and Gross Energy and on Nutrient Digestibility by Steers

Abstract

Six yearling Angus steers averaging 295 kg. were used in a single reversal digestion trial to study effects of frequency of feeding on diurnal excretion of chromic oxide, crude protein and gross energy. A complete pelleted ration including 0.5% chromic oxide was fed at the rate of 4.54 kg. daily either once at 8:00 a.m. or in six equal amounts at 4-hr, intervals. Fecal grab samples were taken at 2-hr, intervals for a 2-day period to determine excretion patterns of indicator and nutrients. The rate of excretion of chromic oxide, crude protein or gross energy was not affected significantly by frequency of feeding, time of sampling or days sampled. However, there was a significant (P<.01) difference between steers in rates of excretion of both indicator and nutrients. Digestion coefficients calculated from chromic oxide were lower than those calculated by the conventional method using total fecal collection, because only 94.2% of the chromic oxide was recovered. Chromic oxide and crude protein excretion patterns were significantly (P<.01) correlated. Digestion coefficients for dry matter and gross energy calculated from chromic oxide in grab samples did not differ significantly from those calculated from the 7-day total collection. Digestion coefficients for crude protein calculated by the two methods differed at 8:00 a.m. and 10:00 p.m. for steers fed once daily and at 2:00 p.m. for those fed six times daily. Apparent digestibility of crude protein was decreased significantly by feeding six times daily compared with feeding once daily. Digestibility of other nutrients was unchanged or slightly improved by frequent feedings.