| Barley (TAMBAR 401), wheat (TAM 101), oats (Coker 234), and wheat middlings were fed to 40 kg cannulated pigs to determine amino acid (AA) digestibilities at the end of the small intestine and over the total tract. Percentages of protein and lysine among the four feedstuffs varied widely (14.3, .44; 14.5, .38; 11.6, .43; 15.73, .66; for barley, wheat, oats, and wheat middlings, respectively). Grains were ground twice with a hammer mill (4mm screen) before mixing. Casein (3%) was added to each grain diet, but not to wheat middlings.;Apparent digestibility of AA measured at the terminal ileum and over the total tract tended to be highest in the wheat diet, lowest for wheat middlings with barley and oats intermediate. Measured in ileal digesta, average digestibility of essential amino acids (EAA) was 85.97, 84.90, 84.31, and 81.18% for wheat, oats, barley, and middlings, respectively. Among the EAA, threonine and tryptophan were either first or second lowest in all but wheat middlings. Arginine, histidine, methionine, and phenylalaline digestibilities were consistently high in all four feedstuffs. Similar lysine digestibilities for all diets (82.58 to 84.46%) suggests that differences in digestibilities of the other AA have little practical importance.;Digestibilities determined over the total tract were generally higher than those measured at the end of the small intestine but the same relative differences were found. Average digestibility for EAA was: wheat (91.43%), oats (89.47%), barley (87.08%), and middlings (79.09%). Among the EAA, lysine and threonine digestibilities were lowest or second lowest in all four feedstuffs.;Differences in nitrogen digestibility between the sampling sites were fairly uniform among the four feedstuffs (5.1 to 6.4%) but there was a wide difference in individual AA and among feedstuffs. Unexpectedly, middlings showed a net increase in 10 AA in the large intestine resulting in an increase in digestibility of 2.09% for the EAA. Synthesis in the hind gut has been reported by others but the number of amino acids and the amount of synthesis found here is unusual.;A replicated 3 x 3 Latin square design was used for the barley, wheat, and wheat middlings diets. The oat diet was fed to four pigs in a fourth period. Pigs were maintained in stainless steel metabolism cages and fed equally.;Since the high digestibility of casein in AA might increase the digestibilities of the test grains, AA digestibilities were calculated to remove the effect of casein. The casein-corrected AA digestibilities for barley, wheat, and oats were lower at the terminal ileum (middlings remained the same since casein had not been added). Average digestibilities of the EAA were similar, 82.5% (wheat), 81.2% (middlings), 81.1% (barley), and 80.4% (oats) but there was still wide variation for individual AA among the four feedstuffs. The casein-corrected values measured over the total tract were also lower than uncorrected values.;Performance of 36 crossbred pigs (average initial weight 22 kg) was used in a 30-day trial to determine the effects of the arginine:lysine ratio in sorghum-based diets. Diets were formulated to contain .78% lysine and arginine using sorghum, soybean meal, and bloodmeal. Synthetic arginine was added to the basal diet to give dietary treatments with arginine:lysine ratios (weight:weight) of 1:1, 1.3:1, 1.6:1.;Feed intake, average daily gain, and feed efficiency were essentially the same for the three dietary regimes which suggests that the arginine:lysine ratios found in simple corn-soybean or sorghum-soybean meal diets should not have an adverse effect on growing pig performance. |
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