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THE EFFECT OF SORGHUM GRAIN VARIETY ON SITE AND EXTENT OF DIGESTION IN BEEF HEIFERS^1,2

Oklahoma State University, Stillwater 74078-0425

	Abstract

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To determine the effect of sorghum grain variety on site and extent of digestion, three pureline sorghum varieties (Darset, Dwarf Redlan, 1133) and a commercially purchased millrun sorghum grain were dry-rolled and fed in an 88% grain diet to Angus-Hereford heifers (230) kg) equipped with ruminal, duodenal and ileal T-type cannulas. Darset is a normal endosperm, high tannin, bird-resistant (BR) type (normal-BR); Dwarf Redlan is a waxy endosperm, low tannin, non-BR type (waxy); 1133 is a waxy endosperm, high tannin, BR type (waxy-BR). The millrun sorghum, representative of most commercial sorghum grain, was a normal endosperm, non-BR type (normal). Diets were fed at 2% of BW (DM basis) in a 4 x 4 latin square. Total tract starch digestibility was similar (P > .05) for all varieties, averaging 90.8%. Ruminal starch digestion tended to be greater (P = .13) for BR types (normal-BR, 75.2%; waxy-BR, 77.3%) than for non-BR types (normal, 68.7%; waxy, 74.1%). Starch digestibility prior to the cecum was greater (P < .10) for varieties with a waxy endosperm than for varieties with a normal endosperm (84.8 vs 78.6%). The large intestine tended to be more important (P < .10) as a site of starch digestion (% of total tract digestion) for varieties with a normal endosperm compared to varieties with a waxy endosperm (13.2 vs 7.2%). Total tract apparent non-NH3 N digestibility was greater (P < .01) for non-BR types than for BR types (66.4 vs 50.9%). Additionally, ruminal feed N disappearance was greater (P < .05) for non-BR than for BR types (50.1 vs 30.1%). Sorghum with a waxy endosperm tended to have increased postruminal N digestion. Nitrogen disappearance (% of total tract disappearance) was nearly complete by the ileum for all varieties (98.4%). Sorghum grain variety altered the site and extent of nutrient digestion in cattle.

Key Words: Sorghum Grain • Starch • Protein • Digestion • Beef Heifers

	Introduction

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Sorghum grain requires less water and can be grown successfully under a wider variety of dryland or irrigated conditions than corn, but it is often discriminated against because of variable quality (Miller et al., 1962), inconsistent cattle growth rates and efficiencies (McCollough et al., 1972) and a lower feeding value than that of corn (NRC, 1984). Limited evidence suggests that endosperm type affects digestibility. Miller et al. (1972) observed that grains with a floury endosperm had higher in situ digestibility but tend to have a low density and test weight (Sullins and Rooney, 1974), limiting commercial use. Grains with a waxy endosperm also have been shown to have increased in vitro digestibility (Hibberd et al., 1982a,b,) and may have less peripheral endosperm and less amorphous protein matrix (Sullins and Rooney, 1974). Tannins in bird-resistant (BR) sorghum decrease bird deprivation and inhibit preharvest mold but reduce starch digestion in vitro (Saba et al., 1972; Hibberd et al., 1982a,b) and N digestion in vivo (Shaffert et al., 1974).

The extent to which sorghum grain variety affects site and extent of digestion is unknown. Endosperm characteristics and tannin level may alter efficiency of feed utilization (Black, 1971). The objective of this study was to quantitate the differences among four widely divergent sorghum grain varieties in chemical composition, in the extent of starch and N digestion in the rumen and in the small and large intestines, and in the extent of protein escape to the small intestine of beef cattle.

	Materials and Methods

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Three pureline sorghum grain varieties of known genetic background (Darset, Dwarf Redlan and 1133) were grown under dryland conditions at the Perkins Agronomy Experiment Station, Perkins, OK. A fourth sorghum grain (normal) was purchased commercially and was representative of most commercial sorghum grain (i.e., normal endosperm and non-BR or low in tannin content). Physical characteristics of these sorghum varieties are denoted in Table 1. Darset is a normal endosperm, BR (normal-BR), Dwarf Redlan is a waxy endosperm, non-BR (waxy), and 1133 is a waxy endosperm, BR (waxy-BR) variety.

Duplicate grain samples, representing composite samples taken from each sack as the grain was rolled, were ground through a 1-mm screen prior to chemical analyses and through a.4-mm screen prior to starch analysis. Dry matter (AOAC, 1975), starch (as alpha-linked glucose by the procedure of MacRae and Armstrong, 1968, modified by Streeter et al., 1989), CP and OM (AOAC, 1975) and nonsequential ADF (Goering and Van Soest, 1970) contents were determined. Condensed tannin content, determined using a vanillin-HCl procedure (Burns, 1971) modified by Price et al. (1978), is reported as catechin equivalents per gram of DM. Grain samples were analyzed further for pepsin-insoluble nitrogen (PIN, Goering and Van Soest, 1970) and sodium chloride-soluble protein (NaCl-N, Waldo and Goering, 1979).

Animal Trial.

Four Angus-Hereford heifers (230 ± 6.4 kg) were surgically fitted, while under anesthesia, with permanent ruminal, duodenal (4 cm distal to the pylorus) and ileal (20 cm cranial to the ileo-cecal junction) T-type cannulas. Heifers were fed one of four diets, differing in sorghum grain variety, at 2% of BW (DM basis) in a 4 x 4 latin square. Sorghum grain was finely rolled through a 30.5-cm x 61-cm roller mill. Feed intake was lower than noted usually in a feedlot or production situation (ad libitum), but higher DM intakes were difficult to maintain under our experimental conditions (individual 2.4-m x 3.8-m pens). Diets (Table 2) were formulated to meet NRC (1984) requirements for CP, Ca and P for medium-framed heifers gaining .6 kg daily. Urea was used as the sole source of supplemental N and cottonseed hulls (containing approximately .3% total dietary N) were used as the roughage source so that feed N reaching the duodenum would be primarily from the grain. Chromic oxide (.20% of diet DM) was used as an indigestible marker.

Strained ruminal fluid (2,000 ml) used to estimate bacterial purine N, N and OM was collected for each heifer into flasks surrounded by ice on d 10 during period 2 at 1400. Bacteria were isolated from ruminal fluid 1 d after collection by differential centrifugation (Weakley, 1983), frozen (–20°C), lyophilized and ground with a mortar and pestle prior to analysis.

Digesta and fecal samples were lyophilized and ground through a 1-mm screen for chemical analyses. Feed, ruminal, bacterial, duodenal, ileal and fecal samples were analyzed for all components denoted in the laboratory trial in addition to NH₃ N by magnesium oxide distillation (AOAC, 1975), purine N (RNA basis; Zinn and Owens, 1986) and chromic oxide (Fenton and Fenton, 1979).

Partial digestion coefficients and amounts of different components presented to and disappearing from segments of the digestive tract were calculated from chromic oxide concentration and intakes. Chyme flows were calculated as chromic oxide intake (g/d) divided by the fractional chromic oxide concentration and DM content of the chyme. Microbial N reaching the duodenum was calculated as duodenal purine N divided by the average ratio of microbial purine N to microbial N obtained in period 2. Although total purine N:N ratio of ruminal bacteria may be influenced by diet and time after feeding (Miller, 1982), differences in bacterial composition generally have been associated with diets divergent in roughage content and have not been associated with grain source or variety (Kaufmann and Lupping, 1982). Therefore, extensive bacterial isolation should not be necessary to obtain valid relative comparisons of the effects of sorghum grain variety on microbial protein yield, efficiency of microbial protein production, ruminal feed N digestibility and escape. Feed N plus endogenous N reaching the duodenum was calculated as duodenal N minus the sum of NH₃ N and microbial N. Organic matter reaching the duodenum was corrected for microbial OM based on means determined for microbial ash (26.3%) and CP (41.9%). True ruminal OM disappearance (OM intake plus duodenal microbial OM minus duodenal OM) was used to calculate the efficiency of microbial protein synthesis (g microbial N/kg OM truly fermented in the rumen).

Statistical Analysis.

The data from the animal trial were described by the following model: Y_ijk = µ + A_i + P_j + V_k + E_jjk, where Y_jjk is the observed value of interest, A is animal, P is period and V is variety of sorghum grain. The components µ, A_i, P_j and V_k were treated as fixed effects of all records of animal i, period j and variety k. Random errors, E_ijk, were specific to each observation. Differences among treatment groups were compared by orthogonal contrasts between least squares means. The orthogonal contrasts compared BR varieties to non-BR varieties, varieties with waxy endosperm to varieties with normal endosperm and the interaction of BR and endosperm type. If the interaction was significant, individual varietal least squares means were contrasted within BR and endosperm types (Steel and Torrie, 1980).

	Results and Discussion

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Laboratory Trial.

Crude protein content (Table 3) was lower (P < .01) for normal (10.3%) than for normal-BR (13.2%) or waxy (12.4%) sorghum grain. Normal-BR contained a greater amount (P < .01) of CP than waxy-BR (12.0%). Differences in CP content among complete mixed diets reflected differences in grain variety. Starch content was greatest for normal sorghum (78.8%) and lowest for normal-BR (72.1); waxy (77.1%) and waxy-BR (76.4%) were intermediate. Condensed tannin content was greater (P < .01) for the BR varieties than the non-BR varieties, typical of BR sorghum grain (Price et al., 1979). Nitrogen solubility in NaCl was highest for the non-BR varieties (normal, 7.4%; waxy, 7.5%); normal-BR (2.1) contained less than waxy-BR (4.2%). Increased NaCl-N has been reported previously for waxy sorghum grains (Lichtenwalner et al., 1978). Within BR varieties, normal-BR (22.0%) had more PIN (P < .01) than waxy-BR (18.3%). Within endosperm types, waxy (13.3%) had less PIN than waxy-BR (18.3%), and normal (13.8%) had less than normal-BR (P < .01). Hibberd et al. (1985) reported that BR sorghum types contained more PIN than non-BR sorghum grain. In our study, the waxy gene appeared to increase NaCl-N content and to reduce the PIN level. Acid detergent fiber content was greater (P <.01) for BR than for non-BR feeds, which was probably caused by tannin, which analytically appears as ADF (Van Soest, 1982).

Total tract OM and starch digestion were similar for all four varieties (Table 4). However, BR varieties tended to have lower OM digestibility than non-BR varieties. From 14 to 30% of this decrease was due to reduced ADF digestion for BR compared with non-BR varieties (P < .01). Reduced ADF digestion of normal endosperm compared with waxy endosperm varieties (P < .05) can explain 20 to 100% of the differences in these varieties. Lower ADF digestion may result from inhibition of digestive enzymes by tannins (Barry and Manley, 1984). Nevertheless, because tannins may interfere with ADF determination (Van Soest, 1982), ADF values probably were overestimated.

Ruminal Digestion.

Due to greater CP content of normal-BR and waxy grain, N intakes were greater when heifers were fed normal-BR or waxy than when fed normal or waxy-BR sorghum grains (Table 5). With all diets, more N reached the duodenum than was fed, which presumably reflects N recycling to the rumen (Kennedy and Milligan, 1980). Ruminal NH₃ N concentrations were relatively low across all diets, which may enhance trapping of recycled N but reduce microbial growth and DM digestion (Satter and Slyter, 1974; Weakley, 1983).

True ruminal OM digestion was not different (P > .10), ranging from 50.1% (waxy-BR) to 57.1% (waxy); normal (56.2%) and normal-BR (52.5%) were intermediate. Non-BR diets tended (P = .17) to result in greater true ruminal OM digestibilities than BR diets. Ruminal starch digestibility did not differ (P > .10) among diets, but values for BR varieties tended to be greater (P = .13) than values for non-BR varieties. Benson et al. (1984) suggested that some ruminal bacteria may be inhibited by certain phenolic compounds and stimulated by others; those phenols may be similar to metabolites formed during attack on condensed tannins. However, in vitro DM disappearance (IVDMD) suggests that non-BR varieties are more digestible than BR varieties (Streeter et al., 1990). Hibberd et al. (1985) noted slightly greater ruminal starch digestion for a BR sorghum grain hybrid than for a non-BR hybrid, similar to our trend, but their tannin levels were considerably lower than in our grains. Explanations for this trend are unclear, but perhaps certain tannins enhance ruminal starch digestion. Streeter et al. (1990) observed that in vitro rate of CO₂ production, presumably an index of the rate of starch digestion in vitro, was greater for BR varieties (normal-BR and waxy-BR) than for normal but was lower than for wax. Condensed tannins have been shown to inhibit bacterial growth (McLeod, 1974), protease and deaminase activity (Tagari et al., 1965; Singh and Arora, 1980) and alpha-amylase activity (Griffiths, 1979) in vitro. In vivo, however, some digestive enzymes appear not to be inhibited by dietary condensed tannin (Mitjavila et al., 1977). Mole and Waterman (1985) showed that tannin binding of protein enhanced tryptic digestion of specific proteins, presumably by causing conformational changes to denature the protein. Denaturation of the protein matrix surrounding sorghum starch granules in the peripheral endosperm may increase digestion of peripheral endosperm starch in the rumen. Therefore, perhaps it is not surprising that IVDMD data do not agree with ruminal OM and starch digestibility.

Condensed tannin flow to the duodenum was greater (P < .05) for BR than for non-BR varieties (1,583 vs 249 CE/g). Ruminal tannin digestibilities for BR varieties were 75.2 and 71.8% for normal-BR and waxy-BR, respectively. Tannin disappearance in the rumen and in other anaerobic fermentation systems has been reported by Reichert et al. (1980) and Hibberd et al. (1985). Although the precise mechanism remains unknown, tannin disappearance in the rumen may occur by bacterial destruction of condensed tannin (Deschamps et al., 1980), or acid-catalyzed tannin condensation within the rumen may reduce the number of specific functional groups available to react with the vanillin-HCl reagent (Hagerman and Butler, 1978). The metabolic fate of condensed tannin has not been determined in cattle. Potter and Fuller (1968) identified metabolic products of dietary tannic acid in the urine of chickens. Moreover, Sell and Rogler (1983) suggested that the depressed performance of chickens fed BR sorghum grain may be due to adverse effects of tannins on liver metabolism. Further study is needed to determine the metabolic fate of condensed tannins in cattle and effects of tannin on liver metabolism.

Ruminal digestibilities of total feed N and non-urea feed N were depressed (P < .01) for BR varieties, resulting in a dramatic increase (P < .01) in ruminal escape of feed N for BR varieties compared with non-BR varieties (93.3 vs 68.2%). Condensed tannin in some forage species decreased NAN digestion in the rumen (Barry and Manley, 1984). Tannin treatment of soybean meal also has been shown to increase ruminal N escape (Driedger and Hatfield, 1972). Hibberd et al. (1985), however, found no effect of a BR sorghum grain on ruminal escape of feed N, but in that study bacteria were not quantitated and the tannin content of the BR grain was considerably lower than in our grains. Condensed tannins are known to bind preferentially to several organic compounds, including urea (McLeod, 1974). Escape of non-BR feed protein from ruminal fermentation is similar to values reported by Hibberd et al. (1985) of 69.0%. However, lower values have been reported for dry-rolled sorghum grain of 58% by Theurer (1979) and 49% by Potter et al. (1971). Reduced DM intake and sorghum varietal differences may partially explain lower escape of feed protein.

Mehansho et al. (1983) reported that feeding of high-tannin sorghum grain to rats resulted in a dramatic change in the parotid salivary gland. After 3 d of feeding BR grain to rats, their parotid glands had enlarged threefold, and a group of proline-rich proteins (PRP) in the saliva had increased about 12-fold. Hagerman and Butler (1981) reported that proline concentration was the protein characteristic having the greatest correlation with tannin affinity. The PRP from rat and human saliva contain 25 to 45% proline. Salivary PRP have a very high affinity for condensed tannins and are thought to protect against the anti-nutritional effects of dietary tannin (Mehansho et al., 1987). When rats are fed high-tannin sorghum grain, weight loss is observed for about 3 d, followed by an initiation of weight gain coincident with maximal PRP synthesis (Asquith et al., 1985). The size of the parotid gland and the production of PRP are greater in ruminant animals, which naturally consume a large portion of their diet as browse, which is high in tannin (Robbins et al., 1987). Gieseck et al. (1976) noted that resting saliva flow was increased by 42% when phenolic monomers (vanillin) were injected into the oral cavity of sheep. Cattle may have the capacity to adapt to high condensed tannin levels by dramatically increasing the production of PRP, although this is unknown. Proline-rich protein production and elevated salivary flow could explain greater chyme flow through the duodenum and increased flow of endogeneous N from the rumen. Greater ruminal starch digestion also could result from increased salivary flow due to enhanced buffering capacity within the rumen. Ruminal pH tended to be higher with BR varieties despite greater fermentation of starch in the rumen. Microbial N (g/d) and OM (g/d) reaching the duodenum were not affected (P > .10) by BR or endosperm type, and diet had no effect (P > .10) on the efficiency of microbial protein synthesis.

Pre-Cecal Digestion.

More (P < .01) ADF and tannin entered the cecum (Table 6) with BR sorghum diets than with non-BR diets. Feeding normal endosperm varieties resulted in more (P < .01) tannin leaving the ileum than waxy endosperm varieties. As with duodenal N flow, NAN exiting the ileum was greater for BR varieties; however, an interaction between BR and endosperm type (P < .05) was noted. Within BR types, normal-BR had a greater (P < .10) amount of NAN leaving the ileum than waxy-BR (55.5 vs 43.5 g/d), perhaps reflecting higher tannin levels in normal-BR, whereas normal and waxy were similar (P > .10) in ileal NAN flow (31.5 vs 36.9 g/d). Within endosperm type, normal grain had less (P < .10) NAN leaving the ileum than normal-BR, whereas waxy and waxy-BR were similar (P > .10). Hibberd et al. (1985) also reported that NAN flow into the cecum was greater with a BR sorghum grain. Increased N flow may be caused by tannin binding of either feed or endogenous N (PRP), decreased grain protein solubility (Chibber et al., 1978; Hibberd et al., 1985) or increased chyme flow. Unlike hydrolyzable tannins, condensed tannins from sorghum grain do not appear to greatly increase intestinal mucin secretion or alter intestinal morphology (Sell et al., 1985). However, increased intestinal mucin secretion could increase NAN flow to the cecum. Non-NH₃ N digestibility ahead of the ileum was depressed (P < .05) for BR diets (normal-BR, 46.2%; waxy-BR, 55.0%) compared with non-BR diets (normal, 63.8%; waxy, 64.4%). Within BR varieties, NAN digestion tended to be less for normal-BR than for waxy-BR, perhaps in part due to higher tannin levels.

Intestinal Digestion.

Starch digestion in the small intestine (Table 7) was low and similar (P > .10) with all varieties, when expressed either as a percentage of starch consumed (7.5, 5.8, 10.6 and 7.6% for normal, normal-BR, waxy and waxy-BR, respectively) or as a percentage of total tract starch disappearance (8.2, 6.4, 11.7 and 8.3% for the same treatments, respectively). Only 24.5 to 41.5% of the starch entering the small intestine disappeared or was digested therein. Generally, varieties with a waxy endosperm tended to have slightly greater fractional starch digestion in the small intestine.

Starch digestibility in the large intestine averaged 9.2% (6.8 to 14.2%) of starch intake or 10.2% (6.9 to 16.4%) of total tract starch digestion, emphasizing its importance as a site of fermentation. Starch digestion in the large intestine tended to be greater (P < .10) for normal than for waxy endosperm varieties (13.2 vs 7.2%). The large intestine partially compensated for lowered starch digestion anterior to the large intestine and was an important site of starch digestion with sorghum grain; much of the residual starch appears to be fermented therein. Greater starch digestion in the large intestine for normal endosperm varieties probably reflects lower starch availability prior to the cecum. Based on ileal starch infusion data collected by Ørskov et al. (1970), increased N excretion might be expected with normal endosperm sorghum because of increased fermentation and increased microbial N synthesis in the large intestine; however, no such relationship was detected. Hibberd et al. (1985) also reported that large quantities of starch were fermented in the large intestine with no effect on fecal N excretion. Net N influx into the large intestine may be apparent only when the ammonia supply associated with the chyme flow is inadequate to match energy available for microbial growth, or perhaps starch that is infused into the ileum is more available for fermentation than is that in grain that has passed through the digestive tract. Why increased fecal N excretion may accompany increased starch fermentation in the large intestine in some studies but not in others is not clear.

In summary, the sorghum grain varieties tested differed in site and extent of digestion. Starch digestion was not inhibited by the BR characteristic (Figure 1) at any site, although there was a tendency for ruminal starch digestion (%) to be enhanced and small intestinal starch digestion to be reduced by tannin. Further study is needed to determine the factors (e.g., pH) responsible for these trends. Ruminal feed N digestibility and prececal and total tract NAN digestibility were reduced greatly by tannin. Non-NH₃ N absorption from the small intestine was less clearly affected by tannin but was higher for waxy than for normal endosperm sorghum. Generally, starch was more digestible ahead of the ileum in waxy than in normal endosperm sorghum, and the waxy characteristic moderated the depression in NAN digestion ahead of the ileum caused by tannin. Consequently, less starch flow to and digestion within the large intestine was observed with waxy endosperm sorghum. Future studies should attempt to correlate these difference in the site and extent of digestion with animal performance data.

View larger version (54K): [in this window] [in a new window]   Figure 1. Daily starch disappearance (kg/d) from the rumen (SE = .0712 kg/d), small intestine (SE = .0825 kg/d) and large intestine (SE = .0757 kg/d) of beef heifers (values above each bar denote starch disappearance from each location as a percentage of daily starch intake; SE = 2.73%, 2.74%, 2.54% for the rumen, small intestine and large intestine, respectively).

	Implications

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	Footnotes

 
¹ Journal Article No. 5561 of the Agric. Exp. Sta., Oklahoma State Univ., Stillwater.

² The assistance of Dave Buchanan in statistical analysis is greatly appreciated.

Received for publication March 21, 1989. Accepted for publication July 27, 1989.

	Literature Cited

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AOAC. 1975. Official Methods of Analysis (12th Ed.). Association of Official Analytical Chemists, Washington, DC.

Asquith, T. N., H. Mehansho, J. C. Rogler, L. G. Butler and D. M. Carlson. 1985. Induction of proline-rich protein biosynthesis in salivary glands by tannins. Fed. Proc. 44:1097.

Barry, T. N. and T. R. Manley. 1984. The role of condensed tannins in the nutritional value of Lotus pedunculates for sheep. II. Quantitative digestion of carbohydrates and proteins. Br. J. Nutr. 51:493.[Medline]

Benson, M. E., D. G. Ely, K. A. Dawson and T. J. Smith. 1984. Phenolic compounds effect on rumen microbes and in vitro digestibility. J. Anim. Sci. 59 (Suppl.1): 417(Abstr.).

Black, J. L. 1971. A theoretical consideration of the effect of preventing rumen fermentation on the efficiency of utilization of dietary energy and protein in the lamb. Br. J. Nutr. 25:31.[Medline]

Burns, R. E. 1971. Methods for estimation of tannin in grain sorghum. Agron. J. 63:511.[Abstract/Free Full Text]

Chibber, B.A.K., E. T. Mertz and J. D. Axtell. 1978. Effects of dehulling on tannin content, protein distribution and quality of high and low tannin sorghum. J. Agric. Food Chem. 26:679.

Deschamps. A. M., G. Mahoudeau, M. Conti and J. M. Lebeault. 1980. Bacteria degrading tannic acid and related compounds. J. Ferment. Technol. 58:93.

Driedger, A. and E. E. Hatfield. 1972. Influence of tannin on the nutritive value of soybean meal for ruminants. J. Anim. Sci. 34:465.[Abstract/Free Full Text]

Fenton, T. W. and M. Fenton. 1979. An improved procedure for the determination of chromic oxide in feed and feces. Can. J. Anim. Sci. 59:631.

French, D. 1973. Chemical and physical properties of starch. J. Anim. Sci. 37:1048.[Abstract/Free Full Text]

Gieseck, D., R. Unzel and P. Hoppe. 1976. Effect of certain organic compounds on saliva secretion in sheep. Arch. Int. Physiol. Biochim. 84:129.[Medline]

Goering, H. K. and P. J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures, and some applications). Agric. Handbook 379, ARS, USDA, Washington, DC.

Griffiths, D. W. 1979. The inhibition of digestive enzymes by extracts of field bean (Vicia faba). J. Sci. Food Agric. 30:458.[Medline]

Hagerman, A. E. and L. G. Butler. 1978. Protein precipitation method for the quantitative determination of tannins. J. Agric. Food Chem. 26:809.

Hagerman, A. E. and L. G. Butler. 1981. The specificity of proanthocyanidin-protein interactions. J. Biol. Chem. 256:4494.[Abstract/Free Full Text]

Hibberd, C. A., D. G. Wagner, R. L. Hintz and D. D. Griffin. 1985. Effect of sorghum grain variety and reconstitution on site and extent of starch and protein digestion in steers. J. Anim. Sci. 61:702.[Abstract/Free Full Text]

Hibberd, C. A., D. G. Wagner, R. L. Schemm, E. D. Mitchell, Jr., R. L. Hintz and D. E. Weibel. 1982a. Nutritive characteristics of different varieties of sorghum and corn grain. J. Anim. Sci. 55:665.[Abstract/Free Full Text]

Hibberd, C. A., D. G. Wagner, R. L. Schemm, E. D. Mitchell, Jr., D. E. Weibel and R. L. Hintz. 1982b. Digestibility characteristics of isolated starch from sorghum and corn grain. J. Anim. Sci. 55:1490.[Abstract/Free Full Text]

Kaufmann, W. and W. Lupping. 1982. Protected proteins and protected amino acids for ruminants. In: E. L. Miller, I. H. Pike and A.J.H. Van Es (Ed.) Protein Contributions of Feedstuffs for Ruminants. pp 36–75. Butterworth Scientific, London.

Kennedy, P. M. and L. P. Milligan. 1980. The degradation and utilization of endogenous urea in the gastrointestinal tract of ruminants: A review. Can. J. Anim. Sci. 60: 205.

Lichtenwalner, R. C., E. B. Ellis and L. W. Rooney. 1978. Effect of incremental dosages of the waxy gene of sorghum on digestibility. J. Anim. Sci. 46:1113.[Abstract/Free Full Text]

MacRae, J. C. and D. G. Armstrong. 1968. Enzyme methods for determination of alpha-linked glucose polymers in biological materials. J. Sci. Food Agric. 19:578.

McCollough, R. L. and B. E. Brent. 1972. Digestibility of eight hybrid sorghum grains and three hybrid corns. Kansas Agric. Exp. Sta. Bull. No. 557. p 27.

McCollough, R. L., C. L. Drake and G. M. Roth. 1972. Feedlot performance of eight hybrid sorghum grains and three hybrid corns. Kansas Agric. Exp. Sta. Bull. No. 557. p 21.

McLeod, M. N. 1974. Plant tannins – Their role in forage quality. Nutr. Abstr. Rev. 44:803.

Mehansho, H., L. G. Butler and D. M. Carlson. 1987. Dietary tannins and salivary proline-rich proteins: Interactions, induction and defense mechanism. Annu. Rev. Nutr. 7:423.[Medline]

Mehansho, H., A. E. Hagerman, S. Clements, L. Butler, J. Rogler and D. M. Carlson. 1983. Modulation of proline-rich protein biosynthesis in the rat parotid glands by sorghums with high tannin levels. Proc. Natl. Acad. Sci. USA 80:3948.[Abstract/Free Full Text]

Miller, E. L. 1982. Methods of assessing proteins for ruminants, including laboratory methods. In: E. L. Miller, I. H. Pike and A.J.H. Van Es (Ed.) Protein Contributions of Feedstuffs for Ruminants. pp 18–35. Butterworth Scientific, London.

Miller, F. R., R. S. Lowery, W. G. Monson, G. W. Burton and H. J. Cruzado. 1972. Estimation of dry matter digestibility differences in grain of some sorghum bicolor (L.) Moench varieties. Crop Sci. 12:563.[Abstract/Free Full Text]

Miller, G. D., C. W. Deyoe, T. L. Walter and F. W. Smith. 1962. Variations in protein levels in Kansas sorghum grain. Agron. J. 56:302.

Mitjavila, S., C. Lacombe, G. Carrera and R. Derache. 1977. Tannic acid and oxidized tannic acid on the functional state of rat intestinal epithelium. J. Nutr. 107:2113.[Abstract/Free Full Text]

Mole, S. and P. G. Waterman. 1985. Stimulatory effects of tannins and cholic acid on tryptic hydrolysis of proteins: Ecological implications. J. Chem. Ecol. 11: 1323.

NRC. 1984. Nutrient Requirements of Beef Cattle. National Academy Press, Washington, DC.

Ørskov, E. R., C. Fraser, V. C. Mason and S. O. Mann. 1970. Influence of starch digestion in the large intestine of sheep on caecal fermentation, caecal microflora and caecal nitrogen excretion. Br. J. Nutr. 24:671.[Medline]

Potter, D. K and H. L. Fuller. 1968. Metabolic fate of dietary tannins in chickens. J. Nutr. 96:187.[Abstract/Free Full Text]

Potter, G. D., J. W. McNeill and J. K. Riggs. 1971. Utilization of processed sorghum grain proteins by steers. J. Anim. Sci. 32:540.[Abstract/Free Full Text]

Price, M. L., A. M. Stronberg and L. G. Butler. 1979. Tannin content as a function of grain maturity and drying conditions in several varieties of sorghum bicolor (L.) Moench. J. Agric. Food Chem. 27:1270.[Medline]

Price, M. L., S. VanScoyoc and L. G. Butler. 1978. A critical evaluation of the vanillin reaction as an assay for tannin in sorghum grain. J. Agric. Food Chem. 26: 1214.

Reichert, R. D., S. E. Fleming and D. J Schwab. 1980. Tannin deactivation and nutritional improvement of sorghum by anaerobic storage of H₂O–Hcl or NaOH–treated grain. J. Agric. Food Chem. 28:824.[Medline]

Robbins, C. T., S. Mole, A. E. Hagerman and T. A. Hanley. 1987. Role of tannin in defending plants against ruminants: Reduction in dry matter digestion. Ecology 68:1606.

Saba, W. J., W. H. Hale and B. Theurer. 1972. In vitro rumen fermentation studies with a bird resistant sorghum grain. J. Anim. Sci. 35:1076.[Abstract/Free Full Text]

Satter, L. D. and L. L. Slyter. 1974. Effect of ammonia concentration on rumen microbial protein production in vitro. Br. J. Nutr. 32:199.[Medline]

Seckinger, H. L. and M. J. Wolf. 1973. Sorghum protein ultrastructure as it relates to composition. Cereal Chem. 50:455.

Sell, D. R. and J. C. Rogler. 1983. Effects of sorghum grain tannins and dietary protein on the activity of liver UDP-glucuronyltransferase. Proc. Soc. Exp. Bio. Med. 174:93.[Medline]

Sell, D. R., W. M. Reed, C. L. Chrisman and J. C. Rogler. 1985. Mucin excretion and morphology of the intestinal tract as influenced by sorghum tannins. Nutr. Rep. Int. 31:1369.

Shaffert, R. E., D. L. Oswalt and J. D. Axtell. 1974. Effect of supplemental protein on the nutritive value of high and low tannin sorghum bicolor (L.) Moench grain for the growing rat. J. Anim. Sci. 39:500.[Abstract/Free Full Text]

Singh, K. and S. D. Arora. 1980. Effect of salseed-meal tannins on protein synthesis, ³⁵S incorporation and cellulose digestibility by rumen microbes in vitro. Indian J. Anim. Sci. 50:821.

Steel, R.G.D. and J. H. Torrie. 1980. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York.

Streeter, M. N., D. G. Wagner, F. N. Owens and C. A. Hibberd. 1989a. Combinations of high-moisture harvested sorghum grain and dry-rolled corn: Effects on site and extent of digestion in beef heifers. J. Anim. Sci. 67:1623.[Abstract/Free Full Text]

Streeter, M. N., D. G. Wagner, C. A. Hibberd, E. D. Milchel, Jr. and J. W. Oltjen. 1990. Effect of variety of sorghum grain on digestion and availability of dry matter and starch in vitro. Anim. Feed Sci. Technol. (In press).

Sullins, R. D. and L. W. Rooney. 1974. Microscopic evaluation of the digestibility of sorghum lines that differ in endosperm characteristics. Cereal Chem. 51: 134.

Tagari, H., Y. Henis, M. Tamir and R. Volcani. 1965. Effect of carob pod extract on cellulolysis, proteolysis, deamination and protein biosynthesis in an artificial rumen. Appl. Microbiol. 13:437.[Medline]

Theurer, C. B. 1979. Microbial protein synthesis as influenced by diet. In: W. H. Hale and P. Meinhardt (Ed.) Regulation of Acid Base Balance, pp 97–124. Church and Dwight Co., Piscataway, NJ.

Van Soest, P. J. 1982. Nutritional Ecology of the Ruminant. O&B books, Corvallis, OR.

Waldo, D. R. and H. K. Goering. 1979. Insolubility of proteins in ruminant feeds by four methods. J. Anim. Sci. 49:1560.[Abstract/Free Full Text]

Weakley, D. C. 1983. Influence of roughage level, ruminal pH and ammonia concentration on ruminal protein degradation and microbial protein synthesis in cattle. Ph.D. Dissertation. Oklahoma State Univ. Stillwater.

Zinn, R. A. and F. N. Owens. 1986. A rapid procedure for purine measurement and its use for estimating net ruminal protein synthesis. Can. J. Anim. Sci. 66:157.

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