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Pearl millet grain was blended with corn in 1:1 or 2:1 ratios in beef finishing diets fed in two metabolism and two feedlot trials. In Exp. 1, diets contained 1) 79.5% corn and 4.5% soybean meal (C-SBM), 2) 28% corn, 54.5% sorghum, and 1.5% soybean meal [GSC(2:1)], and 3) 28% corn and 56% pearl millet [PMC(2:1)]. In Exp. 2, diets contained 1) 81.5% corn and 3.5% soybean meal (C-SBM) or 2) 42.5% corn and 42.5% pearl millet [PMC(1:1)]. Diets fed to steers in metabolism trials in Exp. 1 and 2 had similar (P > .10) apparent digestion coefficients for OM, crude fiber, NDF, and ADF. However, ether extract digestibility was higher (P < .05) for C-SBM than for GSC(2:1) and PMC(2:1) in Exp. 1, and it was higher (P < .10) for C-SBM than for PMC(1:1) in Exp. 2. In both experiments CP digestibility was higher (P < .10) for C-SBM diets, and N retention was similar (P > .10) for diets within each experiment. In each experiment, TDN calculated from apparent digestion coefficients was converted to NEm and NEg. The TDN, NEm, and NEg were lower (P < .10) for GSC(2:1) and PMC(2:1) than for C-SBM in Exp. 1. Experimental diets were fed to steers (n = 45; 396 +/- 19 kg initial BW; 70-d ad libitum feeding) in Exp. 1 and to heifers (n = 30; 318 +/- 15 kg initial BW; 92-d ad libitum feeding) in Exp. 2. The ADG, empty body weight gain (EBG), and predicted EBG were not different (P > .10) for diets composed of the different grain sources. Feed DMI and DM per gain were higher (P < .05) for PMC(1:1) than for C-SBM in Exp. 2. Pearl millet supplied approximately 88% as much NEm and 85% as much NEg as the corn-SBM portion of diets having similar CP concentrations.

The effect of duodenal slaframine (SF) infusion on site and extent of digestion was determined using four steers equipped with ruminal, duodenal, and ileal cannulas in a 4 x 4 Latin square. A 77% dry-rolled corn diet was provided in 12 equal portions daily at a DMI of 2.26% BW. Slaframine in a .9% saline excipient was infused into the duodenum every 12 h with total daily dose of 0, 30, 60, or 90 micrograms /kg of BW. Slaframine infusion had no effect on ruminal pH, ruminal NH3 N, or solids and liquids passage rate. Slaframine increased (linear, P < .10) total tract OM and starch disappearance and digestibility and tended to increase (linear, P = .14) total tract N digestibility. Ruminal starch disappearance tended to be decreased (quadratic, P = .16) by SF. Small intestinal OM digestibility was increased (linear, P < .10) but starch digestibility in the small intestine was not affected by SF. Increased total tract starch digestibility was caused by increased (quadratic, P < .10) starch fermentation in the large intestine. Ruminal feed N digestibility decreased at the intermediate doses of SF (quadratic, P < .10). Total N digestibility in the small intestine tended to be increased (cubic, P = .13) with 30 and 90 micrograms of SF/kg of BW. Decreased ruminal feed N digestion was compensated for by increased (quadratic, P < .10) small intestinal feed N disappearance for steers treated with intermediate doses of SF. The potential of SF to increase starch digestion in the rumen and small intestine seems to be limited.

The effects of supplemental fish meal on site and extent of digestion were determined using four steers equipped with ruminal, duodenal, and ileal cannulas. Fish meal was included in diets to supply 0 (0FM), 25 (25FM), 50 (50FM), or 75 (75FM) g of N daily above the CP requirement of a 400-kg steer gaining 1.2 kg/d. Total tract starch digestibility tended to be greatest for 25FM (95%), lowest for 0FM (90%), and intermediate for 50FM (94%) and 75FM (92%). Total tract N digestibility was greatest for 25FM, lowest for 0FM, and intermediate for 50FM and 75FM (cubic, P < .05). Total tract starch digestibility increased .46 percentage units for each unit increase in N digestibility (n = 16, P = .03). Ruminal starch digestibility was greatest for 25FM, intermediate for 50FM and 75FM, and lowest for 0FM (quadratic; P < .10). Starch flow to the duodenum was decreased for 25FM and 50FM vs 0FM and 75FM (quadratic, P < .10) and N flow to the duodenum was increased (linear, P < .01) by fish meal. Fish meal supplementation increased N digestibility (quadratic, P < .05) but had no effect (P > .10) on starch digestibility in the small intestine. Starch digestibility in the small intestine was not related to N flow to the duodenum; however, starch digestibility increased .9 percentage units for each percentage unit increase in N digestibility (n = 16, P = .02). Fish meal supplementation tended to increase total tract starch digestibility by increasing ruminal, but not small intestinal, digestibility.

The effects of sorghum type on amino acid digestion were determined by feeding heifers (230 kg) equipped with ruminal, duodenal, and ileal cannulas bird-resistant (BR) or non-BR grains that had a normal or waxy endosperm (NORMAL-BR, WAXY-BR, NORMAL, WAXY). Dry-rolled grain diets were fed at 2% of BW in a 4 x 4 Latin square design. Total (TAA), essential (EAA), and nonessential (NAA) amino acid intake (grams/day) tended to be greater for BR than for non-BR grains. Feed (plus endogenous) amino acids reaching the duodenum were calculated by subtracting amino acids of microbial protein from total flow. Flow (grams/day) of total and feed TAA, EAA, NAA, and proline-rich-protein (sum of aspartate, glutamate, glycine, and proline) to the duodenum was greater (P < .05) for BR than for non-BR grains. The ratio between feed proline-rich-protein and NAA reaching the duodenum was similar to that noted with feed intake. Amino acid disappearance (grams/day) from the small intestine was unchanged (P > .10) by sorghum type, although the digestibility (percentage of duodenal flow) of TAA, EAA, NAA, and most individual amino acids was decreased (P < .05) for BR varieties. Amino acid flow to the cecum (grams/day) was generally greater for NORMAL-BR than for WAXY-BR (P < .10) or for NORMAL (P < .01) and greater (P < .10) for WAXY-BR than for WAXY.(ABSTRACT TRUNCATED AT 250 WORDS)

A double L-shaped intestinal cannula was developed in an attempt to overcome problems observed previously with simple T-type cannulas. The cannula was constructed from cyclopolyvinyl chloride water pipe fittings. Construction materials were fairly rigid, but by connecting the split cannula pieces with elastic castration bands the cannula had some flexibility. Placing a short cone over the exposed cannula barrel reduced mechanical damage to the intestine. The double L cannula required a much smaller incision in the intestine during surgical insertion than a T-type cannula; it also simplified replacement. Construction is described; use and performance of the cannula has been satisfactory.

To compare the effects of sorghum grain hybrids on site and extent of digestion, two yellow (Y1 and Y2), two cream (C1 and C2), and two hetero-yellow (HY1 and HY2) sorghum grains were fed (1.85% BW, DM basis) in an 81% dry-rolled grain diet to steers (342 kg BW) equipped with ruminal, duodenal, and ileal cannulas within a 6 X 6 Latin square. Yellow (YEL) hybrids had a homozygous yellow endosperm and a yellow seed coat; cream (CREAM) and hetero-yellow (HET-YEL) hybrids had a heterozygous (partial) yellow endosperm, with white or red seed coats, respectively. Total tract starch digestibility (percentage) was greater (P less than .10) for CREAM and HET-YEL (82.3) than for YEL (78.9), primarily because of greater (P less than .05) starch digestion in the large intestine. Ruminal starch digestibility (percentage) was greater (P less than .10) for HET-YEL (73.2) than for CREAM (66.3) and was a larger proportion of total tract digestion for HET-YEL (90.6) than for CREAM (80.1). Ruminal starch digestion was correlated negatively (r = -.46; P less than .08) with ruminal escape of feed N. Prececal starch digestibility (average 76.2%) was more strongly correlated with ruminal digestibility (r = .69; P less than .01) than with digestion in the small intestine (r = .41; P = .12). Total tract nonammonia N (NAN) digestibility (percentage) was greater (P less than .10) for CREAM than for HET-YEL, greater for Y1 (P less than .10) than for Y2, greater for C2 (P less than .05) than for C1, and greater for HY2 (P less than .05) than for HY1. Flow of NAN to the duodenum was correlated negatively (r = -.55; P less than .05) with prececal starch digestion. Small intestinal NAN disappearance (g/d) was greater (P less than .01) for HY1 (76.0) than for HY2 (52.2). Microbial N flow (r = .88; P less than .01), but not feed N flow (r = .17; P = .52), to the duodenum was correlated with partial NAN digestibility in the small intestine. Hybrids differed in site and extent of digestion. Differences were generally larger for N than for starch.

Four diverse sorghum hybrids (yellow, cream, hetero-yellow and red) and corn grain were dry-rolled and fed in an 85% grain diet to Angus-Hereford steers (241 kg) equipped with ruminal and double L-type duodenal and ileal cannulas to compare the effects of grain source on site and extent of digestion. Yellow (yel) has a homozygous yellow endosperm, with a yellow seed coat, whereas cream and hetero-yellow (het-yel) have a heterozygous yellow endosperm with white and red seed coats, respectively. Red has a homozygous white endosperm with a red seed coat. Diets were fed at 2% of initial BW (DM basis) in a 5 x 5 Latin square. Total digestive tract starch digestibility (%) was greater (P less than .05) for corn (92.5) than for red (84.3), yel (84.3) and het-yel (82.9) but not greater (P greater than .10) than for cream (87.9). Ruminal starch digestibility (%) was greater (P less than .10) for corn (85.8) than for sorghum hybrids (69.1). Pre-cecal starch digestibility (%) was greater (P less than .05) for corn (90.6) than for het-yel (76.2), red (74.8) and yel (74.1). Ruminal escape (%) of grain N was greater (P less than .10) for red (79.9) than for het-yel (69.2), cream (66.5) and yel (66.1), with corn (53.6) being less (P less than .10) than sorghum hybrids. Pre-cecal and total tract non-NH3 N digestibilities (%) were not altered (P greater than .10) by grain source. Hybrid of sorghum altered site and extent of starch digestion and ruminal escape of grain N; hybrids had estimated gain:feed ratios that were 81 to 93% of those of rolled corn grain.

To determine the effects of blends of high-moisture harvested sorghum grain (HMS) and dry-rolled corn (DRC) on site and extent of digestion, high-grain diets were fed to Angus-Hereford heifers (315 kg) in a 5 x 5 latin square. The grain portion consisted of ratios (HMS:DRC) of 0:100, 25:75, 50:50, 75:25 and 100:0. Heifers were equipped with ruminal, duodenal and ileal T-type cannulas. Digestibilities of OM (P less than .05) and non-ammonia nitrogen (NAN; P less than .01) in the total tract declined linearly as HMS replaced DRC. Chyme flow (liters/d) through the duodenum increased linearly (P less than .01), and true ruminal OM disappearance tended to decline linearly (P less than .10) as HMS replaced DRC. A quadratic response (P less than .05) in extent of starch disappearance (g/d) in the rumen was noted; blends were lower than either individual grain. Ruminal escape of feed N tended to be quadratic (P less than .10); values for individual grain types were greater than blends. Microbial efficiency increased linearly (P less than .05) as HMS replaced DRC. Extent of starch digestion in the rumen averaged 82.7% compared to only 2.9% in the small intestine and 5.7% in the large intestine. Altering the ratio of HMS to DRC appeared to have more effect on ruminal fermentation than on digestion in the small intestine; most starch and nitrogen responses were quadratic. Increases in ruminal pH and chyme flow, potentially caused by increased salivary flow, may cause non-linear changes in the solubility of proteins in HMS and DRC, when fed as blends, altering the digestibility of protein and starch from values predicted from the individual grains.