GRAIN PROCESSING EFFECTS ON STARCH UTILIZATION BY RUMINANTS 1'2

C. Brent Theurer 3

Univers i ty of Arizona, Tucson

A B S T R A C T

Starch utilization may be markedly enhanced by proper grain processing; however, extent of improvement is primarily dependent upon the ruminant species, grain source and method of pro- cessing. Grain processing has less impact on starch digestion by sheep than cattle. The magnitude of improvement is inverse to the starch digestion values for nonprocessed (or minimally processed) grains. Utilization of sorghum grain starch is improved most by extensive processing, and then corn, with little improvement in barley starch digestion. Studies comparing processing effects on barley or wheat starch utilization by cattle were not found. Steam-flaking consistently improves digestibility of starch by cattle fed corn- or sorghum grain-based diets over whole, ground or dry- rolled processes. Other extensive processing methods appear to enhance starch digestibility of corn and sorghum grain to a similar extent as steam-fiaking, but comparative data are too limited to quantitate adequately effects of these methods. This improvement in starch utilization appears to be the primary reason for enhanced feed conversion of cattle fed diets high in these processed grains. The major site of cereal grain starch digestion is usually the rumen. Processing increases microbial degradation of starch in the rumen and decreases amounts of starch digested post- ruminally. Rates of in vitro amylolytic attack of starch in cereal grains by both ruminal microbial and pancreatic enzyme sources are improved by processing methods employing proper combina- tions of moisture, heat and pressure. In vitro and in situ studies suggest that much of the increase in ruminal starch fermentation with steam-flaking is due to changes in starch granular structure, which produces additive effects beyond those of decreasing particle size. Thus, efficiency of rurninal starch fermentation by cattle appears to be improved by proper processing of corn and sorghum grain. Processing and grain source studies both suggest that maximal total tract starch digestibility is positively related to the extent of digestion in the rumen. (Key Words: Starch Digestion, Processing, Ruminants, Barley, Maize, Sorghum.)

I n t r o d u c t i o n

Starch is the pr imary nutr ient of those ruminant diets used to p romo te high levels of product ion. Thus, op t imal starch ut i l izat ion is fundamenta l to improving eff ic iency of produc- t ion of animal products . The principal sources of starch in these diets are the cereal grains, mos t c o m m o n l y barley, corn and sorghum grain. Enhancemen t o f starch ut i l izat ion by grain processing is dependen t upon the me thods o f processing, ruminant species and grain source.

1 Presented at a symposium entitled "Starch Utili- zation by Ruminants" at the 77th Annu. Meet. of the Amer. Soc. of Anim. Sci., August 15, 1985, Univ. of Georgia, Athens.

2 Arizona Agr. Exp. Sta. Journal Article 4092. 3 Dept. Anim. Sci. Received October 14, 1985. Accepted May 9, 1986.

Many methods of processing grain have been used in an a t t emp t to improve their feed utiliza- t ion by ruminants . A comple te descript ion o f these various processes are described by Hale and Theurer (1972) and Hale (1980). In this manuscript the t e rm "processed" grains applies to extensive me thods of preparing grains for feeding: steam-flaking, reconst i tut ing, early harvest ensiling (high moisture) , popping, exploding, roasting or microniz ing; whereas the te rm "nonproces sed" grains refers to whole grains or those minimal ly processed: cracked, ground, dry-rolled or raw.

As noted in recent reviews (Hale, 1973; ~rskov, 1976), processing me thods do not appear to be as impor tan t with sheep and goats (as with cattle), due to their ability to uti l ize effect ively whole grains.

In an excel lent review, Hale ( 1 9 7 3 ) s t a t e s that the effect of processing t r ea tment on starch ut i l izat ion by ruminants should be evaluated in the in tact grain rather than with isolated starches, because the relat ionship of

1649 J. Anim. Sci. 1986. 63:1649-1662

1650 THEURER

starch with other grain components may be altered with grain processing.

The magnitude of the processing effect on starch utilization is greater with corn and sor- ghum grain than with barley. This undoubtedly relates to inherent differences among these grains in starch and protein digestibility. Direct comparisons of starch digestibilities among feed grains are limited. Saba et al. (1964) and Keating et al. (1965) found that total starch digestibilities were higher in barley diets than in sorghum grain diets when fed to cattle. Table 1 summarizes starch and protein digestibilities for barley, corn and sorghum grain from values (mostly single grain studies) cited in the litera- ture, and from the only comparison trial among these three grains reported in recent years (Spicer et al., 1986). Apparent digestibilities of both starch and protein are lowest for sor- ghum grain, followed by corn and then barley. Protein and starch digestibilities appear to be directly related.

TABLE 1. DIGESTIBILITY AMONG FEED GRAINS

Sor- ghum

Item grain Corn Barley

% Protein a

Total tract digestion 55 68 72

Starch a Total tract digestion 92 96 99 Ruminal digestion 66 73 93 Ruminal escape 34 27 7 Intestinal digestion b 79 82 78

Protein c Total tract digestion 61 66 68

Starch c Total tract digestion 97 99 99 Ruminal digestion 75 84 88 Ruminal escape 25 16 12 Intestinal digestion d 87 94 93

asummarized without regard to processing effects from individual values (or recalculations) presented in reviews by Waldo (1973), Sowe (1982), Theurer (1984) and data presented in tables 5 through 10.

bBased on amounts apparently presented to small intestine.

CAdapted from comparison trial data among the three minimally processed grains (Spicer et al., 1986).

dBased on amounts in abomasal digesta.

It is also interesting to note that grains pro- viding extensive ruminal degradation appear to exhibit higher overall starch digestibilities (table 1). Thus, the lower the ruminal escape, the higher the total starch utilization. Theurer (1984) concluded that the amount of starch escaping ruminal fermentat ion appears to be an important factor for explaining differences in both total starch and total protein digestibility among feed grains. Only minimal data (Kay et al., 1972; Spicer et al., 1986) are available directly comparing the extent of in vivo rumi- nal digestibilities of starch in feed grains. Kay et al. (1972) noted ruminal starch digestibility for barley to be greater than that for corn (81 vs 61%).

Studies concerned with processing effects on alteration of cereal grain starch and its utili- zation can be classified into three categories: 1) performance and efficiency of feed utiliza- tion, 2) in vitro measurements of starch struc- tural changes and rates of ruminal microbial fermentation or enzymatic degradation and 3) in vivo determinations of total, ruminal and postruminal digestion.

Performance and Efficiency of Feed Utilization

The influence of various processing methods on performance and feed conversion by beef cattle has. been reviewed by Hale (1980). The studies clearly demonstrate the efficacy of steam-flaking, reconstituting, early harvesting, popping, exploding or micronizing as methods for improving utilization of corn- or sorghum grain-based diets (table 2). Each of these pro- cessing methods appears to be about equally effective in improving feed conversion, if quality control is carefully practiced. Average feed conversions and daily gains for whole shell and dry rolled corn were similar in these sum- mary comparisons. Hale (1980) also notes that extensive processing of wheat or barley does not improve feed utilization, but may enhance feed intake and gain.

In Vitro Degradation and Starch Granule Alteration

Starch structure may be altered and in vitro or in situ rates of amylolyt ic at tack by both ruminal microbial and pancreatic enzyme sources may be markedly improyed by exten- sive processing of barley, corn and sorghum grain. In vitro starch digestion by ruminal

GRAIN PROCESSING AND STARCH UTILIZATION 1651

TABLE 2. COMPARISON OF CORN AND SORGHUM GRAIN PROCESSING SYSTEMS ON FEED CONVERSION AND DAILY GAIN IN BEEF CATTLE

FINISHING TRIALS a

Processing method

Feed/kg gain Daily gain (kg)

Sor- Sor- ghum ghum

Corn grain Corn grain

Dry-rolled 6.9 7.3 1.2 1.2 Flaked 6.3 6.5 1.2 1.2 Reconstituted b 6.4 6.3 1.3 1.2 Micronized, exploded, popped 6.5 1.2

aAdapted from Hale (1980).

bAlso includes early harvested processing system for corn comparisons.

microorganisms (Trei et al., 1970) or by pan- creatic enzymes (Osman et al., 1970) may be increased approximately threefold by steam- flaking or pressure-cooking *s dry-grinding of sorghum grain (table 3). Similar improvements in barley, sorghum grain and corn starch utili- zation, using in vitro amylase techniques, have been reported by Frederick et al. (1973) and McNeill et al. (1975). In situ ruminal incuba- tion of steam-flaked or high moisture ensiled corn also resulted in greater starch utilization than incubation of dry-ground corn (Galyean et al., 1981).

Osman et al. (1970) showed that with moist- heat t reatment of grains (steam-flaking or pressure-cooking), the degree of flaking (flake flatness) is the principal factor in improving availability of barley and sorghum grain starch

tO in vitro enzymatic degradation. Proper inter- action of heat, pressure and moisture seems to be involved in altering susceptibili ty of cereal starches to enzymatic attack. The data of Frederick et al. (1973) suggest that there is a critical pressure at which enzymatic degrada- t ion of cereal starches will be improved. This critical pressure appears to be altered by mois- ture content of the grain and temperature of the contact surfaces used to flake the grain.

Moist-heat processing of barley or sorghum grain also markedly increases in vitro volatile fat ty acid (VFA) production (#M/g of dry matter incubated) by ruminal microorganisms (Theurer et al., 1967; Trei et al., 1970). Results from the latter s tudy indicate that in vitro VFA production and starch digestion are closely cor- related. This apparent increase in efficiency of

TABLE 3. IN VITRO SORGHUM GRAIN STARCH DIGESTION BY RUMINAL MICROORGANISMS OR PANCREATIC ENZYMES a

Enzyme source Processing method

Starch diges- tion, %

Ruminal microbial suspension b

Bovine pancreas homogenate

Porcine pancreatin

Dry-ground 18 Pressure-cooked and flaked 53

Dry-ground 13 Steam-flaked 37

Dry-ground 17 Steam-flaked 49

aAdapted from Osman et al. (1970) and Trei et ai. (1970).

bMicrobial fraction was separated by continuous flow centrifugation at 39,000 • g from ruminal ingesta of steers fed 65% grain diet.

1652 THEURER

starch fermentation is in agreement with the nylon bag studies of Galyean et al. (1981), who demonstrated that processing corn by steam- flaking or high moisture ensiling produces additive effects beyond those of reduction in particle size alone (table 4). In situ starch dis- appearance within each particle size was higher for processed (steam-flaked or high moisture ensiled) than for nonprocessed (dry-ground) corn, in nearly every comparison.

Hale (1973) hypothesized from histological studies on reconstituted grain (Sullins et al., 1971) that disrupting the protein matrix around starch may be essential in improving digestion of processed grains. McNeill et al. (1975) suggest that the effect of processing upon the solubility (or integrity) of the protein matrix encapsulating starch granules is the primary factor affecting efficiency of starch utilization. Using scanning electron micro- scopy, Harbers (1975) concluded that pro- cessing sorghum grain clearly alters starch so it is more susceptible to amylolytic attack. He studied starch granule structural changes in steam-flaked, micronized and popped sorghum grain and amylolysis of that starch by purified pancreatic amylase and ruminal microorga- nisms. His studies with sorghum grain clearly demonstrated that 1) steam-flaking or micro- nizing alters starch granules and produces small conglomerates of non-descript starch, 2) pop- ping grain expands individual starch granules into thin lattices of interconnecting sheets and 3) for each of the processes, protein bodies (kafrin) seem to remain intact, but protein sur- rounding and between individual starch granu- les is disrupted.

Total, Ruminal and Post-ruminal Digestion

Many studies have used abomasally or duo- denally cannulated animals to determine the effect of grain processing on in vivo starch utili- zation by ruminants. Several researchers have concluded that cannulation has no major nega- tive effect on digestive functions of sheep and cattle recovered from surgery (Harris and Phillipson, 1962; Hayes et al., 1964; MacRae and Wilson, 1977). It has been generally accepted that flow of duodenal digesta is depressed as a result of continuous collection procedures in the first 24 h with a possible compensatory increase during subsequent days. However, with long-term total collections, several researchers (Thompson and Lamming, 1972; Oldham and Ling, 1977; Wanderley et al., 1985) found no consistent evidence of flow inhibition. Thus, the use of cannulated animals, well-trained to the collection procedures, appears to be satisfactory for partitioning starch utilization in the digestive tract. Collec- tion procedures and marker methods for esti- mating duodenal flow appear to be important factors altering flow and digestibility estimates (Drennen et al., 1970; Theurer, 1979; Wander- ley et al., 1985), and should be carefully con- sidered in making comparative evaluations of ruminal and post-ruminal starch utilizations among grains.

Due to incomplete recovery of markers at the duodenum (Tamminga, 1975; Zinn et al., 1980; Wanderley et al., 1985), ruminal disap- pearance of starch may be underestimated in studies employing marker ratio techniques. In the studies of Wanderley et al. (1985), con-

TABLE 4. PERCENTAGE IN SITU RUMINAL CORN STARCH DISAPPEARANCE AS INFLUENCED BY PARTICLE SIZE AND PROCESSING ab

Com- Mean particle size, gm parison Processing method 3,000 1,500 750

1 Dry-ground 12 12 19 Steam-flaked 31 37 41

Dry-ground 19 17 27 High-moisture ensiled 12 24 44

aAdapted from Galyean et al. (1981). bDisappearance values are averaged over all incubation times (2, 4, 6, 8 h) with 16 observations per mean.

GRAIN PROCESSING AND STARCH UTILIZATION 1653

ducted with steers fed a high grain diet, appar- ent ruminal dry matter disappearance estimated by chromium oxide and lignin ratio techniques were 12 and 29% lower, respectively, than those determined by automated, continuous total collection of duodenal digesta.

The major site of cereal grain starch diges- tion is usually the tureen. As expected from the relative starch digestion values for nonprocessed grains, in vivo ruminal and total starch utiliza- tion of sorghum grain is improved most by processing, followed by corn, with little or no improvement in ruminal or total starch diges- tion for barley. Tables 5, 6 and 7 summarize studies comparing the effect of processing methods on total and ruminal starch digestion of barley, corn or sorghum grain diets fed to sheep and cattle. Values for sheep (table 5) are averaged over all grains, due to limited compari- sons within grains, whereas total and ruminal digestibilities for cattle are summarized sepa- rately for corn (table 6) and sorghum grain (table 7). Studies comparing processing effects on barley or wheat starch utilization by cattle were not found.

With sheep, only small increases in total and ruminal starch utilization were observed by rolling or flaking, reconstituting, high moisture ensiling or roasting as compared to feeding the grain whole, ground, cracked or raw (table 5). Data are not consistent within or among grains and essentially no improvements occurred due to processing barley. This minimal impact of processing might be expected because total digestibilities for nonprocessed grains averaged several percentage units higher for sheep than cattle (96 vs 91%; table 5 vs 6 and 7), and average percentage of starch escaping ruminal fermentation in sheep is markedly lower than that for cattle (11 vs 30 and 43%; table 5 vs 6 and 7).

Steam-flaking consistently improves ruminal degradation by microorganisms, as well as total starch digestibilities, by cattle fed corn-based diets over whole, dry-rolled or steamed-whole processes (averages of 86 and 99 vs 70 and 91%, respectively; table 6). Grinding or cracking apparently improves total starch digestibilities over whole corn (Galyean et al., 1979; Turgeon et al., 1983). In one study (Galyean et al., 1976), corn processed by high moisture harvest- ing (ground before ensiling) improved starch utilization to the same extent as steam-flaking. It is interesting to note that all of the compari- sons of corn processing systems cited with

cattle have been published since 1976. As with corn, ruminal escape of extensively

processed sorghum grain fed to cattle is de- creased to about one-half that of dry-rolled or ground grain (table 7). Total starch digestion averages 98% for sorghum grain processed by steam-flaking, micronizing or reconstitution compared with 91% for dry-rolled or ground grain. Total tract digestibility of extensively processed sorghum grain and corn appears to be similar (98 vs 99%), whereas ruminal escape appears to be somewhat lower for corn than for sorghum grain (14 vs 24%; table 6 vs 7).

Daily starch intakes are generally low in the cattle studies reported herein, averaging only 3,300 g. Typical intakes for finishing feedlot cattle in the United States will usually exceed 5,000 g daily. Only four studies approached or exceeded this level. Limited data (Kartchner, 1972; Garcia et al., 1981b) suggest that in- creasing intake has little effect on total digesti- bility coefficients or percentage ruminal escape of starch from steam-flaked sorghum grain. Despite the low starch intakes, the studies sum- marized may be fairly representative of the effects of processing on starch utilization by cattle with greater daily intakes; however, suffi- cient data are lacking to substantiate processing effects with various grains fed at high levels of intake.

~lrskov (1976) concluded that the extent of processing of cereals for cattle should be suffi- cient to avoid large reductions in digestibility, but further processing to increase the extent and rate of ruminal fermentation would be of doubtful value or even undesirable. In contrast, from the experimental results summarized herein, increasing the extent or rate of ruminal microbial degradation of starch by processing is advantageous to the animal in terms of total starch utilization (and usually efficiency of feed utilization). The data of Rahnema (1977), Theurer (1979) and Spicer et al. (1986)suggest that factors (i.e., processing or grain source) decreasing escape of feed starch from ruminal fermentation also may alter feed protein escape, as well as amounts of microbial N pre- sented to the intestines.

Alterations in escape of starch from ruminal fermentation will affect amounts of starch pre- sented to the intestines for subsequent digestive action. Tables 8, 9 and 10 summarize pro- cessing comparison studies on post-ruminal digestion by sheep and cattle. Published data for sheep are too limited to establish the effect

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The marked decrease in amounts of starch entering, the intestines of cattle due to pro- cessing is clearly documented in the corn and sorghum grain comparison studies summarized in tables 9 and 10. Amounts of starch digested post-ruminally by cattle are also markedly less for steam-flaked, reconstituted or micronized grains compared with whole, ground or dry- rolled grains (345 vs 591 for corn; 885 vs 1,425 g for sorghum grain). Percentage of starch digested in the intestines (of that presented) was consistently greater for the processed vs nonprocessed grains (92 vs 76% averaged over both grains). A major effect of proper grain processing is to shift the site of starch digestion from the intestines to the rumen, with con- comitant increases in percentage digested within both sites. When intestinal capacity to digest starch is limiting for nonprocessed grains, it appears that processing minimizes intestinal limitations by decreasing the amounts of starch presented to the intestines, as well as increasing percentage starch digested post-ruminally.

The effect of processing on starch digestion in the small intestine is not well documented; however, in two of three studies (Kartchner, 1972; Hibberd et al., 1983; Aguirre et al., 1984) steam-flaking or reeonstitution of corn or sorghum grain enhanced starch digestion in the small intestine of cattle. Although the per- centages of corn and sorghum grain starch fer- mented in the ceacum and large intestine (of that presented) in their studies appear to be increased by steam-flaking or reconstituting vs dry-rolling (or whole) grain, the amounts of starch escaping digestion in the small intestine are markedly decreased by one-third or more. Thus, the amounts of processed starch fer- mented post-ileally are somewhat lower than that for nonprocessed starch. Post-ileal starch digestion in the preceding studies ranges from 1 to 13% of the total starch ingested, but most values were 2 to 3% of ingested. These limited data suggest that most studies underestimate the value of processing on starch utilization because of the apparent compensating digesti- bility in the large intestine for incomplete diges- tion of starch in the rumen and small intestine for poorly processed (or nonprocessed) grains. In these three studies, starch digestibilities through the ileum averaged 89% for dry rolled or whole grains compared with 96% for the steam-flaked or reconstituted grains. This

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GRAIN PROCESSING AND STARCH UTILIZATION

TABLE 9. PROCESSING EFFECTS ON POST-RUMINAL DIGESTION BY CATTLE OF CORN STARCH PRESENTED TO THE INTESTINES a

1659

Reference

Grain processing Entering method intestines, g

Starch

Digested in intestines b

g %

Digested in small intestine, %

Cole et al. (1976)

Galyean et al. (1976)

Dry-rolled 710 Steam-flaked 222

Dry-rolled 673 Ground, high moisture

(GHM) 359 GHM + propionic acid 1,095 Steam-flaked 477

Lee et al. (1982) Whole 1,420 Steam-flaked 450

Turgeon et al. (1983) Whole 2,472 Cracked 1,935

Aguirre et al. (1984) Whole 550 Dry-rolled 500 Steam-flaked 350

Processing comparison avg Whole or dry-rolled 832 Steam-flaked 375

540 195

572

327 964 448

667 400

1,953 1,601

400 400 335

591 345

76 88

85

91 88 94

47 89

79 82

73 8O 96

71 92

67 71 88

aAdapted from data in references cited.

bBased on amount entering the intestines and appearing in the feces.

represents an 8% improvement over the non- processed grains, which is greater than the improvement based on total digestibility for these three studies (93 vs 98%). It is possible that with higher starch intakes that these ileal differences may be even greater than those noted by Kartchner (1972), Hibberd et al. (1983) and Aguirre et al. (1984).

In conclusion, proper processing of corn or sorghum grain for cattle fed high grain diets improves in vitro, in situ and in vivo starch utilization. This improvement appears to be due largely to a marked increase in ruminal fermen- tation of the processed starch, as well as in- creased digestion in the small intestine, while decreasing fermentation losses in the ceacum and large intestine. Processing also probably enhances energy and N economy for the animal by minimizing starch fermentation and micro- bial protein synthesis in the lower gut (Orskov et al., 1970; Spicer et al., 1986). In the corn-

parison studies reported herein, only about 10 to 25% of the starch from steam-flaked corn or sorghum grain escapes digestion in the rumen, whereas 30 to 45% of the starch from dry- rolled grains escapes ruminal fermentation. Although data are limited, similar differences in ruminal escape of starch are noted for other processing methods when compared with non- processed grains. Thus, a m o u n t s of processed starch digested in the intestines a r e decreased by one-third or more of that of p0st-ruminal digestion of nonprocessed corn or Sorghum grain starch.

For sorghum grain, processing appears to improve starch utilization by disruption of the protein matrix surrounding the starch granules. Proper processing of corn or sorghum grain in- cludes quality control to ensure optimal condi- tions for adequate application o f moisture, heat and pressure (or early harvest ensiling or reconst i tu t ion) . Processing and grain Source

1660 THEURER

TABLE 10. PROCESSING EFFECTS ON POST-RUMINAL DIGESTION BY" CATTLE OF SORGHUM GRAIN ~TARCH PRESENTED TO THE INTESTINES a

Reference

Starch

Digested in Grain intestines b processrng Entering method intestines, g g %

Digested in small intestine, g

Holmes et al. (1970)

McNeill et al. (1971)

Kartchner (1972)

Hinrnan and Johnson (1974a)

Hinrnan and Johnson (1974b)

Steamed and rolled c 360 266 74 Pressure-steamed and

and rolled d 150 101 67

Ground 1,200 1,128 94 Micronized 1,220 1,159 95 Reconstituted 760 745 98 Steam-flaked 380 372 98

Dry-rolled 1,747 1,563 Steam-flaked 1,229 1,145 Dry-rolled 2,866 2,534 Steam-flaked 1,341 1,136

88 89 95 93 93 88 94 85

Ground 368 335 91 Dry-rolled 875 595 68 Micronized 534 518 97 Steam-flaked 699 664 95

Dry-rolled 1,394 711 51 Micronized-low 1,481 1,407 95 Micronized-rnedium 1,405 1,349 96 Micronized-high 1,202 1,118 93

Garcia et al. (1981a) Dry-rolled 2,715 2,362 87 Steam-flaked 848 789 93

Hibberd et al. (1983) Dry-rolled 1,923 1,290 67 33 Reconstituted 482 407 84 71

Processing comparison avg Dry-rolled or ground 1,781 1,425 80 Steam-flaked,

reconstituted or micronized 952 885 93

aAdapted from data in references cited.

bBased on amount entering the intestines and appearing in the feces.

CSteamed 8 rain before rolling (steaming time less than one-half of that recommended for steam-flaking).

dsteamed at 3.5 kg/cm 2 for 1.5 min before rolling (usually referred to as pressure-cooked).

s tudies bo th suggest tha t grains which are extensively degraded in the rumen also have the

highest overall s tarch digestibilities. Comparat ive studies on s tarch ut i l izat ion o f

processed feed grains are lacking and should be c o n d u c t e d to establish more clearly their com- parative value for providing energy to high pro- ducing ruminan t animals. Clearly, addi t ional i n fo rma t ion is needed on the impac t o f grain processing on pre- and post-ileal starch utiliza-

t ion and its re la t ionship to energy and N utiliza-

t ion in ruminants .

Literature Cited

Aguirre, E. O., A. L. Goetsch and F. N. Owens. 1984. Corn grain processing and site of digestion by heifers. Anim. Sei. Res. Rep. MP116, p 190. Oklahoma State Univ., Stillwater.

Beever, D. E., J. F. Coehlo Da Silva and D. G. Armstrong. 1970. The effect of processing maize on its digestion in sheep, Proc. Nutr. Soc. 29."

GRAIN PROCESSING AND STARCH UTILIZATION 1661

43A. Buchanan-Smith, J. G., R. Totusek and A. D. Tillman.

1968. Effect of methods of processing on digesti- bility and utilization of grain sorghum by cattle and sheep. J. Anim. Sci. 27:525.

Cole, N. A., R. R. Johnson and F. N. Owens. 1976. Influence of roughage level and corn processing method on the site and extent of digestion by beef steers. J. Anim. Sci. 43:490.

Drennan, M. J., J.H.G. Holmes and W. N. Garrett. 1970. A comparison of markers for estimating magnitude of rumen digestion. Brit. J. Nutr. 24: 961.

Frederick, H. M., B. Theurer and W. H. Hale. 1973. Effect of moisture, pressure, and temperature on enzymatic starch degradation of barley and sor- ghum grain. J. Dairy Sci. 56:595.

Galyean, M. L., D. G. Wagner and R. R. Johnson. 1976. Site and extent of starch digestion in steers fed processed corn rations. J. Anim. Sci. 43: 1088.

Galyean, M. L., D. G. Wagner and F. N. Owens. 1979. Corn particle size and site and extent of digestion by steers. J. Anita. Sci. 49:204.

Galyean, M. L., D. G. Wagner and F. N. Owens. 1981. Dry matter and starch disappearance of corn and sorghum as influenced by particle size and pro- cessing. J. Dairy Sci. 64:1804.

Gareia, J. A., C. B, Theurer and W. H. Hale. 1981a. Digestao ruminal e pos-ruminal do amido, em novilhos alimentados corn dois niveis de grao de sorgo floculado. Revista da Sociedade Brasileira de Zootecnia. 10(2):235.

Gareia, J. A., C. B. Theurer, W. H. Hale and R. Ray. 1981b. Emprego de dois periodos de coleta para determinar a digestao ruminal e pos-ruminal do amido, em novilhos. Revista da Sociedade Brasileira de Zootecnia. 10 (2) : 266.

Hale, W. H. 1973. Influence of processing on the utili- zation of grains (starch) by ruminants. J. Anita. Sci. 37:1075.

Hale, W. H. 1980. Feed preparation and processing. In: D. C. Church (Ed.) Digestion Physiology and Nutrition of Ruminants, Vol. 3 (2nd Ed.). pp 19--35. O & B Books, Inc., Corvallis, OR.

Hale, W. H, and C. B. Tbeurer. 1972. Feed preparation and feed processing. In: D. C. Church (Ed.) Digestive Physiology and Nutrition of Rumi- nants, Vol. 3 ( l s t Ed.). pp 49--76. O & B Books, Inc., Corvallis, OR.

Harbers, L. H. 1975. Starch granule structural changes and amylolytic patterns in processed sorghum grain. J. Anita. Sci. 41:1496.

Harris, L. E. and A. T. Phillipson. 1962. The measure- ment of the flow of food to the duodenum of sheep. Anim. Prod. 4:97.

Hayes, B. W., C. O. Little and G. E. Mitchell, Jr. 1964. Influence of ruminal, abomasal and intestinal fis- tulation on digestion in steers. J. Anim. Sci. 23: 764.

Hibberd, C. A., D. G. Wagner, R. L. Hintz and D. D. Griffin. 1983. Effect o f sorghum grain variety and processing method on the site and extent of starch digestion in steers. Anim. Sci. Res. Rep. MP114. p 28. Oklahoma State Univ., Stillwater.

Hinman, D. D. and R. R. Johnson. 1974a. Influence of processing methods on digestion of sorghum

starch in high concentrate beef cattle rations, J. Anita. Sci. 39:417.

Hinman, D. D, and R. R. Johnson. 1974b. Influence of degree of micronization on the site and extent of sorghum starch digestion in beef cattle fed high concentrate rations. J. Anim. Sci. 39:958.

Holmes, J.H.G., M. J. Drennan and W. N. Garrett. 1970. Digestion of steam-processed milo by rumi- nants. J. Anim. Sci. 31:409.

Kartchner, R. J. 1972. Starch digestion in the bovine as influenced by level and processing of sorghum grain. M.S. Thesis. Univ. of Arizona, Tucson.

Kay, M., N. A. MacLeod and A. Pavlicevie. 1972. The value of different cereals in diets for growing steers. Proc. Brit. Nutr. Soc. 31:57A (Abstr.).

Keating, E. K., W. J. Saba, W. H. Hale and B. Taylor. 1965. Further observations on the digestibility of milo and barley by steers and lambs. J. Anim. Scl. 24:1080.

Lee, R. W., M. L. Galyean and G. P. Lofgreen. 1982. Effects of mixing whole shelled and steam flaked corn in finishing diets on feedlot performance and site and extent o f digestion in beef steers. J. Anim. Sci. 55:475.

MacRae, J. C. and D. G. Armstrong. 1969. Studies on intestinal digestion in the sheep. 2. Digestion of some carbohydrate constituents in hay, cereal and hay-cereal rations. Brit. J. Nutr. 23:377.

MacRae, J. C. and S. Wilson. 1977. The effects o f various forms of gastrointestinal eannulation on digestive measurements in sheep. Brit. J. Nutr. 38:65.

McNeill, J. W., G. D. Potter and J. K. Riggs. 1971. Ruminal and postruminal carbohydrate utiliza- tion in steers fed processed sorghum grain. J. Anim. Sci. 33:1371.

McNeiU, J. W., G. D. Potter, J. K. Riggs and L. W. Rooney. 1975. Chemical and physical properties of processed sorghum grain carbohydrates. J. Anita. Sci. 40:335.

Oldham, J. D. and J. R. Ling. 1977. Measurements of the rate o f flow of dry matter in digesta passing through the duodenum o f sheep. Brit. J. Nutr. 37:333.

~rskov, E. R. 1976. The effect of processing on diges- tion and utilization of cereals by ruminants. Proc. Nutr. 35:245.

~rskov, E. R., C. Fraser and R.N.B. Kay. 1969. Dietary factors influencing the digestion of starch in the rumen and small and large intestine of early weaned lambs. Brit. J. Nutr. 23:217.

~rskov, E. R., C. Fraser, V. C. Mason and S. O. Mann. 1970. Influence of starch digestion in the large intestine of sheep on caecai fermentation, caecal microflora and faecal nitrogen excretion. Brit. J. Nutr. 24:671.

Osman, H. F., B. Theurer, W. H. Haie and S. M. Mehen. 1970. Influence of grain processing on in vitro enzymatic starch digestion of barley and sorghum grain. J. Nutr. 100:1133.

Rahnema, S. 1977. Ruminal and postruminal utiliza- tion of sorghum grain protein by steers. Ph.D. Dissertation. Univ. o f Arizona, Tucson.

Ramirez, R. G., H. E. Kiesling, M. L. Galyean, G. P. Lofgreen and J. K. Elliott. 1985. Influence of steam-flaked, steamed-whole or whole shelled corn on performance and digestion in beef steers.

1 6 6 2 THEURER

J. Anim. Sci. 61:1. Saba, W. J., W. H. Hale, F. l lubbert , Jr., J. Kiemat and

B. Taylor. 1964. Digestion of milo and barley by cattle. J. Anita. Sci. 23:533.

Sowe, J. 1982. Ruminai and postruminal util ization of barley, corn and sorghum grain starch by beef steers. M.S. Thesis. Univ. of Arizona, Tucson.

Spicer, L. A., C. B. Theurer, J. Sowe and T. H. Noon. 1986. Ruminal and postruminal utilization o f nitrogen and starch from sorghum grain-, corn- and barley-based diets by beef steers. J. Anim. Sci. 62:521.

Sullins, R. D., L. W. Rooney and J. K. Riggs. 1971. Physical changes in the kernel during reconstitu- tion of sorghum grain. Cereal Chem. 48:567.

Tamminga, S. 1975. The influence of the me thod of preservation o f forage on the digestion in dairy cows. 2. Digestion o f organic mat ter , energy and amino acids in fores tomachs and intestines. Netherlands J. Agr. 23:89.

Theurer, C. B. 1979. Microbial protein synthesis as affected by diet. In: W. H. Hale and P. Meinhardt (Ed.) Regulation of Acid-Base Balance. pp 9 7 - 125. Church and Dwight, Piscataway, NJ.

Theurer, C. B. 1984. Digestibility differences among feed grains. In: Proc. Feed Grain Utilization Symp. p 1. Texas Tech Univ., Lubbock, Septem- ber 20, 1984.

Theurer , B., J. Trei and W. H. Hale. 1967. In vitro volatile fa t ty acid product ion as influenced by

s team processing and flaking o f milo and barley. Proc. West. Sec. Amer. Soc. Aniln. Sci. 18:189.

Thompson , F. and G. E. Lamming. 1972. The flow of digesta, dry mat ter and starch to the d u o d e n u m in sheep given rations containing straw of varying particle size. Brit. J. Nutr. 23:391.

Trei, J., W. H. Hale and B. Theurer. 1970. Effect of grain processing on in vitro gas production. J. Anim. Sci. 30:825.

Turgeon, O. A., Jr., D. R. Brink and R. A. Britton. 1983. Corn particle size mixtures , roughage level and starch utilization in finishing steer diets. J. Anita. Sci. 57:739.

Waldo, D. R. 1973. Extent and parti t ion o f cereal grain starch digestion in ruminants . J. Anim. Sci. 37:1062.

Wanderley, R. C., C. B. Tbeurer, S. Rahnema and T. H. Noon. 1985. Au toma ted long-term total collection versus indicator me thod to est imate duodenal digesta flow in cattle. J. Anim. Sci. 61: 1550.

White, T. W., T. W. Perry, B. R. Tonroy and V. L. Lechtenberg. 1973. Influence of processing on in vitro and in vivo digestibility of corn. J. Anim. Sci. 37:1414.

Zinn, R. A., L. S. Bull, R. W. Hemken, O.F.S. Button, C. Enlow and R. W. Tucker. 1980. Appara tus for measuring and subsampling digesta in ruminants equipped with reentrant intestinal cannulas. J. Anim. Sci. 51:193.