Abomasal and plasma nitrogen constituents of steers fed on different physical forms of shelled maize

Eight abomasally fistulated steers were fed on diets of either ground, cracked or whole shelled maize at equalized intakes. Dry matter disappearance as a percentage of dietary intake averaged 73.1, 69.9 and 65.1 for steers fed ground, cracked and whole shelled maize, respectively, but these differences were not significant (P > 0.05). Total abomasal N tended to be lower in steers given cracked maize; however, this difference was nonsignificant. Abomasal nonprotein N was somewhat lower, and protein N tended to be higher with ground maize, these differences also being nonsignificant. Cracked maize resulted in slightly greater amounts of abomasal nonprotein N and lower amounts of protein N. Plasma urea-N was highest in steers fed on cracked maize. Concentrations of abomasal amino acids were not significantly (P > 0.05) affected by the form of the maize. Of the plasma amino acids, lysine and alanine were significantly higher (P < 0.05) with cracked maize and glutamic acid was significantly higher (P < 0.01) with whole shelled maize. Total essential amino acids were significantly (P < 0.05) higher with cracked maize. The ratios of glycine to the branched-chain amino acids (valine, leucine and isoleucine) in either plasma or abomasal digesta were similar for ground, cracked or whole shelled maize.