Cattlemen's Day, 1997; Kansas Agricultural Experiment Station contribution; no. 97-309-S; Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service); 783; Beef; Grain sorghum; Particle size; Processing; Digestibility; Enzyme; Growing cattle


A 73-day growing study utilizing 203 crossbred steers (681 lb) and a digestion trial examined the effect o f sorghum grain particle size on rumen fermentation, ration digestibility, and performance of growing steers fed 37% grain and 63% ground alfalfa. Dry-rolled grain sorghum p article sizes in both trials were about 2000, 1500, and 1000 microns, for the coarse- (CR), medium- (MR), and fine-rolled (FR) treatments , respectively. Coarsely rolled corn (2000 microns) was included as a positive control. In the growing study, half of sorghum was treated at feeding time with an enzyme product, Digest "M". The rations were 35 to 37% dry grain plus ground alfalfa hay and supplement. Total ration dry matter, neutral detergent fiber, and starch digestibilities increased linearly (P<.02) with decreasing sorghum grain particle size. Rumen pH, ammonia and total volatile fatty acid concentrations, and acetate-to-propionate ratio were unaffected by grain type or particle size. Dry matter intake was not influenced by grain types or particle size. Steers fed FR sorghum gained 9% faster (P<.03) during the first 28 days and tended to gain faster (5%, P<.14 ) over the entire trial than those fed CR sorghum , with gains on MR sorghum being intermediate. FR sorghum produced 6% more efficient gains (P<.07) than CR, and MR grain was intermediate. Digest "M" enzyme treatment of the sorghum grain had no influence. Feed con versions of CR, MR, and FR sorghum were 93, 94, and 99% of corn. This research indicates that grain sorghum in high roughage backgrounding programs should have a maximum average particle size of 1000 microns.


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