Eight digestion trials were conducted with pigs fitted with ileal T-cannulas to determine the apparent digestibilities of N and amino acids in common protein feedstuffs. Trial-to-trial variation was minimal as determined by the variation in digestibilities for soybean meal, which was evaluated in each trial. Apparent digestibilities varied widely; ileal N digestibility ranged from 88 to 63%, and ileal lysine digestibility ranged from 93 to 40%. In general, ring-dried blood meal, corn gluten meal, Menhaden fish meal, poultry-by-product meal and extruded whole soybeans were the most digestible, followed by canola meal, sunflower meal, peanut meal and meat and bone meal. Cottonseed meal and feather meal were the least digestible. Mean values for each feedstuff agree well with published data. Variation in digestibilities among samples of the same feedstuff was greater for the meat and bone meals. Regression of ileal essential amino acid digestibilities on ileal and fecal N digestibility indicated that amino acid digestibilities can be predicted more precisely from ileal N digestibility than from fecal N digestibility. However, neither ileal nor fecal N digestibility could be used with a high degree of certainty to predict ileal amino acid digestibilities.

Apparent nutrient digestibilities of yellow-dent corn, low-tannin sorghum, hard red winter wheat, barley, oat groats and wheat middlings were determined near the end of the small intestine and over the total digestive tract of growing pigs. Gross energy digestibilities for corn, sorghum and oat groats were similar; wheat had a slightly lower (P less than .05) digestibility, followed by barley (P less than .05), with wheat middlings being the least (P less than .05) digestible. About 7% of the gross energy in corn, sorghum, wheat and oat groats was digested in the large intestine, compared with 11% for barley and 17% for wheat middlings. The starch in all products was essentially 100% digestible by the end of the small intestine. Ileal amino acid digestibilities tended to be highest for wheat and oat groats, followed by corn, sorghum, barley and wheat middlings. The range in ileal digestibilities was 73.8 (sorghum) to 84.2% (wheat) for lysine, 69.6 (corn) to 81.4% (wheat) for tryptophan and 63.4 (wheat middlings) to 77.9% (oat groats) for threonine. Amino acid digestibilities determined over the total tract were generally higher than ileal digestibilities; however, values for lysine, methionine and phenylalanine were generally lower, indicating a net synthesis of these amino acids in the large intestine.

Four sorghums, ranging widely in tannin content, and yellow corn were evaluated in two 5 x 5 Latin square digestion trials and a growth trial. All grains were grown in the same field under similar conditions. The sorgums and their tannin contents (milligrams of catechin/100 mg of dry matter, as determined by a modified vanillin-HCl method) were: Ga615, 3.40; NK300, 3.17; TAM680, .83, and G766-W, .88. Diets were supplemented with casein to provide .70 and .60% lysine in digestion trials 1 and 2, respectively. In trial 1, conducted with noncannulated, 25-kg pigs, digestibilities of dry matter, gross energy and N averaged for the low tannin sorghums (TAM680 and G766-W) were higher (P greater than .01) than the corresponding digestibilities averaged for the high tannin sorghums (Ga615 and NK300). N balance data indicated that utilization of absorbed N was not reduced in pigs fed the high tannin sorghums. Corn and the low tannin sorghums had similar digestibilities. In trial 2, conducted with 50-kg pigs fitted with T-cannulas at the terminal ileum, digestibilities of dry matter, gross energy, N and all amino acids again averaged higher (P greater than .01) for the low tannin sorghums than for the high tannin sorghums, whether measured at the end of the small intestine or over the total digestive tract. The one exception was methionine digestibilities at the terminal ileum, which did not differ between the high and low tannin sorghums. Among the amino acids, digestibilities of glycine, proline and histidine appeared to be the most depressed in the high tannin sorghums, as compared to the low tannin sorghums. Digestibilities of most nutrients were higher for NK300 than Ga615, suggesting a difference in type of tannin, or other compound, between grains. Corn and the low tannin sorghums, averaged together, had similar digestibilities for most nutrients. In the growth trial, 10 pigs, individually fed form 20 to 94 kg, received grain-soybean meal diets based on each grain except NK300. Gains were not affected by diet, but feed consumption was 9% higher (P greater than.05) and feed efficiency 10% (P greater than .01) poorer for pigs fed Ga615 than for those fed low tannin sorghums. Performance was similar (P greater than .10) for animals fed the low tannin sorghums and those fed corn.

A replicated trial of 3 X 3 Latin square design was conducted with growing pigs (about 29 kg initially) to determine the effects of different levels of feed intake on nutrient digestibilities determined near the end of the small intestine and over the total digestive tract. Pigs were fiftted with simple T-cannula. Feeding levels were ad libitum (AL) and limit-fed (4.5 or 3% of body weight/d). A 16% sorghum-soybean diet was used. Limit-fed pigs were fed at 12-h intervals and water was limited to 2 liters/kg of diet; AL pigs received water ad libitum. Consumption by pigs fed ad libitum averaged 6% of body weight/d. Neither feeding method nor level greatly affected nutrient digestibility measured at the end of the small intestine, but values tended to decrease as feeding level decreased. Comparisons of nutrient digestibility between AL and limit-fed pigs ranged from 2.9 to .7 percentage units, with only N (P less than .10) and methionine (P less than .05) reaching significance. Differences between 4.5 and 3% were slightly larger, ranging from 4.3 to -.2 percentage units, with differences for dry matter, N, gross energy and several amino acids reaching significance (P less than .10 or P less than .05). Measured over the total tract, observed differences among feeding levels were again small, but the trend was reversed, with digestibilities increasing as feeding level decreased. The estimated percentage of ingested nutrients that disappeared in the large intestine increased as feeding level decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of sorghum particle size on nutrient digestibilities at the terminal ileum and over the total digestive tract of growing-finishing pigs were investigated in a replicated 3 X 3 Latin square trial. Sorghum-casein diets were used. Sorghum was dry rolled (C) or ground in a hammer mill through 6.4 mm (M) or 3.2 mm (F) screens, producing particles with a modulus of fineness of 3.57, 2.85 or 2.36, respectively. Each successive reduction in particle size improved (P less than .05) the apparent ileal digestibility of dry matter, starch, gross energy and N. Measured over the total digestive tract, digestibilities of these components were highest (P less than .05) for the F diet but they did not differ (P greater than .10) between diets M and C because of increased (P less than .05) disappearance in the large intestine of dry matter, starch and gross energy from the C diet. N loss in the large intestine was also higher for pigs fed diet C than for those fed diet M, but the difference was not significant. The digestibilities of most amino acids at the terminal ileum were improved (P less than .05) as particle size decreased. Lysine digestibilities were not affected (P greater tha .10). Amino acid digestibilities measured over the total digestive tract were consistently higher (P less than .05) for diet F than diets M and C, which did not differ (P greater than .10) from one another. A comparison of ileal and total tract digestibilities indicated a net disappearance of all measured amino acids except lysine during large intestine transit. These data indicate that increasing fineness of grind will improve digestibility of nutrients in sorghum by growing-finishing pigs.