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Feeding Barley to Poultry: A Review1
The Professional Animal Scientist 8:1-7
Feeding Barley to Poultry: A Review1 S. L. BOYLES and R. L. JOHNSON
North Dakota State University Fargo, ND 58105
K. B. KOCH
Northern Crops Institute Fargo, ND 58105 Abstract
Barley is utilized to best advantage in poultry diets when consideration is given to the class of bird being fed and the desired level of performance. As with other cereal grains barley must be ground to achieve maximum utilization when used in poultry diets. The ~-glucans inherent to most barleys can create problems for young birds and birds raised on litter. The amount of barley in broiler diets can gradually by increased as the birds become adapted to it. When poultry are fed barleybased diets, reduced variability in performance and improved growth can be obtained through the use of enzyme supplementation. Enzyme supplementation is not required in iayer diets that contain barley. However, during peak production periods barley should not be used as the sole grain components. Young turkeys responded to enzyme supplementation of barley diet with improved average daily gains and feed efficiencies. (Key Words: Barley, Poultry, p-glucanase.) Introduction
It is generally understood that barley contains higher fiber and lower energy values than either wheat or corn (55, 56). Energy-dense diets have become the norm in the poultry industry. Because cereal grains can supply 60 to 85% of the energy contained in such diets (72), barley's lower energy and high fiber values may preclude its use (11).
1Approved for publication by Director of the North Dakota Agric. Exp. Sta. Reviewed by L. W. Luther and R. H. Stock.
Barley has been considered a nontraditional feedstuff for poultry and as such is perhaps underutilized. Under certain circumstances its use could yield reduced production costs. Results of a turkey feeding study showed that a barley-soybean meal diet provided a $361ton savings when compared to a corn-soybean meal diet (27). Turkeys fed the corn-soybean meal diet gained more weight per pound of feed consumed, but the cost of gain during the study favored the barley-soybean meal diet by $.05/1b of weight gained. Feed Preparation
Poultry diets are fed in a mash (meal), pelleted, or crumbled form. Particle size reduction of whole grains is required when feeding poultry. Particle size reduction facilitates the mixing of ingredients, provides increased pelleting efficiency and pellet quality, and perhaps most importantly improves digestion through exposure of increased surface area (5). The degree of particle size reduction is limited by practical considerations. Sibbald (69) found when all ground material was less than 841 J.l in diameter with more than 95% less than SOO J.l, "true metabolizable energy" values of barley were reduced (69). Particle sizes referred to as "fine" or "medium" (700 to 1,000 J.l) in the literature are preferred for swine and poultry (65). More descriptive terminology for defining particle size is provided by ASAE Standard-S319 (1). Pelleting or crumbling of poultry feeds offers several advantages including improved feed-to-gain ratio, prevention of selective feeding, more uniform intake of nutrients, reduced feed wasting, improved palatability, and improved handling characteristics (25). When high-fiber feeds, such as those contain-
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ing barley, are pelleted, an improvement in energy density is observed. Performance of poultry fed barley-based diets can be improved by the addition of dietary betaglucanase (f3-glucanase). f3-glucanase activity is relatively stable to pH above 1 for 30 min and temperatures up to 60 C for 10 min. Edney et al. (25) observed endo-f3-glucanase activity to be 100, 104, 81, 88, 98, and 42% at 7, 5, 4, 3, 2, and 1 pH, respectively. There was a 20 to 36% decrease in f3glucanase as a result of pelleting (25). Variability in temperature, time of exposure, and moisture conditions during the pelleting process will affect enzyme activity loss. Steam conditioning of feed mash to moisture levels of 15% and greater is commonly required to produce quality pellets. One possible way to protect f3-glucanase during pelleting would be to encapsulate it in wax. However, encapsulation using beef fat impeded enzyme availability (29). Enzymes can be added in liquid form and sprayed on the feed after pelletization. Water treatment increased the nutritive value of barley (31). Hesselman et al. (44) demonstrated that high-moisture storage of barley prior to use in feed improved chick growth. Other researchers have confirmed the benefits of water treatment (32, 71). However, water addition has proved to be impractical in most poultry feeding systems. Beta-glucans
Barley is not extensively used in poultry diets because of necrotic enteritis, dehydration, and sticky droppings, and problems associated with it. Beta-glucan (f3-glucan) a component of the endospermal cell walls of barley has been identified as the primary causative agent. f3-glucan is a polymer composed of f31-4 linked glucose units interspersed with f31-3 bonds that prevent interchain aggregation (30). The f3-glucan content of a barley kernel may represent 2 to 10% of the total when expressed on a weight basis. A mean f3-glucan content of 7% was reported by Henry (41) for Australian barleys. The detrimental effect of f3-glucan is primarily attributed to its ability to absorb and control water.. In solution f3-glucan is highly viscous (10, 71, 74). Materials such as f3-glucan impede the digestion and absorption of nutrients by enclosing them
within a gel-like matrix (11, 13, 26). Because fat is absorbed as a large conglomerate particle its assimilation is affected more than other nutrients by containment within the gel-like matrix (11, 13, 26). Poultry lack the appropriate enzyme system needed to reduce the matrix and thereby alleviate the problem. When barley-based diets are consumed by poultry, the problem of reduced nutrient assimilation is coupled to increased transit time through the gut. The net effect is reduced nutrient assimilation per unit of time. Young poultry are more affected than adult birds by this phenomenon. Most research has shown that a reduction in the viscosity of digesta using enzyme degradation produced positive results. Work by Burnett (10) identified f3-glucanase as the effective enzyme contained in previous crude enzyme preparations. The principle effect of dietary f3-glucanase was reduced matrix formation by f3-glucan, which allowed degradation of endosperm cell wall by other dietary enzymes and resulted in the exposure of intracellular starch and protein to endogenous digestive enzymes (42, 62). A mixture of dietary enzymes, such as f3-glucanase and a-amylase, may maximize weight gain and reduce sticky droppings. The 1989 cost associated with treatment of barley and barley-based diets with dietary f3-glucanase was about $3.00Iton (27). In addition to the detrimental effect of f3-glucan, barley has been found to increase levels of microbial activity in the intestine (13, 73). It has been suggested that this increased microbial activity is due to the slower rate of passage observed with barley-based diets. Chicks fed barley exhibited a greater response to antibiotics than those fed wheat or corn. Chicks fed barley supplemented with f3-glucanase had lower mortality rates than those fed barley without f3-glucanase or a cornbased diet (16, 17). Climatic factors have been found to influence the feeding value of barley by altering the f3-glucan content (36). Hesselman and Thomke (45) reported barley grown under warm climatic conditions in~ creased water extract viscosity. Increased f3-glucan content has been associated with increased levels of cell wall and kernel hardness (41). Drought conditions tended to elevate f3-glucan deposition. Barley grown in low rainfall regions of the Western United States responded to enzyme supplementa-
FEEDING BARLEY TO POULTRY: A REVIEW
tion whereas barley from regions with greater rainfall failed to respond in a like manner (75). Increased moisture during the ripening season or after harvest when the grain is stored has been associated with lowered digesta viscosity (43). Poultry feeders and feed manufacturers would benefit from development of techniques that would define the conditions under which high levels of [3glucans could be expected in barley. With such information certain batches of grain could be diverted from feed use or treated with enzymes before being used as feed. The long-term solution may be reduced [3-glucan content through plant breeding. Agronomic practices also influence [3glucan levels. Delaying ripening until cooler weather through delayed seeding or fertilization may reduce [3-glucan levels. Chicks
Barley contains between 1.5 and 8.0% [3-glucans (9) which are suspected to cause the high intestinal viscosity and wet sticky droppings observed in chicks fed diets containing barley (23, 50). Supplementation of barley diets with [3-glucanase has resulted in increased gain when used with chicks (6, 44). Supplementation of diets with a mixture of [3-glucanase and protease resulted in heavier body weights and improved feed-to-gain (FIG) ratios (57). Berg (7) improved the growth of chicks from 0 to 8 wk with enzyme supplementation, but found no response from 8 to 21 wk. However, littler conditions were improved for all the chicks receiving enzyme supplementation. Broilers
To date barley has not been utilized to any great extent in broiler diets. Currently the feed industry and broiler producers favor cereals with lower fiber contents and higher energy values, such as corn and wheat. Birds fed barley diets usually have lower body weights and poorer FIG ratios than corn- or wheat-fed broilers (20). Pelleted barley may prove to be similar to wheat in production value (63). Rotter et al. (64) observed that performance of broilers fed hulled barley was equal to that of birds fed wheat. However, their FIG
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ratios were somewhat inferior due to the presence of increased levels of fiber. These differences could be reduced by reformulating diets based on an equivalent nutrient density basis or through addition of dietary fat. Ingestion of [3-glucans causes increased water consumption. This, along with the viscous condition in the gut, results in the associated problems of wet litter and carcass cleaning. The addition of [3glucanase to broiler diets that contain barley reduced the viscous condition within the intestine (42) and aided in alleviating the problem of wet litter (35). Campbell et al. (14) observed that the time required to reach market weight was increased by 4 to 5 d when barley diets without enzyme supplementation were compared to a typical broiler diet. This time difference was reduced to 1.5 d when enzyme supplementation was used. In addition, feed costs per unit of live body weight were less for the enzyme-supplemented barley diets. Other research supports the use of enzymes in broiler diets containing barley (18, 42, 43, 65). Although observed improvement is greatest during the starter phase, it is suggested that enzyme treatments be continued throughout the growth period. Coon et al. (22), Campbell et al. (12), and Classen et al. (20) reported that enzyme addition to a barley-based diet not only improved overall performance but also reduced the variability in weight gain and feed conversion efficiency. This resulted in more uniform flocks. Metabolizable energy content of barley can vary with variety (8). A reduction of this variability would increase the accuracy of diet formulation and reduce the risk of unpredictable performance. Campbell and Classen (11) devised a system they called a "sliding density" program. Under the guidelines of the program the diet density is gradually reduced and the barley level increased throughout the feeding period. Typically the initial density is 96% (starter diet), which is reduced to 94 and 92% in the grower and finisher diets, respectively. This corresponds to barley incorporated at 40,60, and 80%, with fat ranging from 3 to 4%. The economics of this program do not differ substantially from a continuous low density-high barley feeding program. However, the slower growth for the first 3 wk of age is largely eliminated. An alternative
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would be to feed a conventional starter (or prestarter) diet, with barley introduced in the grower and finisher diets. Chicks and HUll-less Barley
The absence of the fibrous hull should reduce objections to barley when used as a poultry feedstuff. However, several reports have indicated unfavorable results when hull-less barley was fed to broiler chicks (12, 18). Anderson et al. (3) observed that the performance of chicks fed hull-less barley was not different from those fed conventional barley, but gains and feed efficiency were 17% lower than chicks fed corn. Jensen et al. (47) observed that enzyme supplementation improved the performance of chicks. Rotter et al. (65) reported the weight gain and F/G ratios for p-glucanase treated hull-less barley diets were equal to or superior to those of birds fed wheat-corn diets. Layers
Barley is an excellent grain for laying birds provided their energy and amino acid requirements are met (59). Fats and oils can be used to supplement barley-based layer diets (4). Gillingham et al. (34) concluded that corn and barley can be used as the major energy source in laying hen rations. Moss (53) observed that barley can replace wheat in layer rations and may actually lead to greater egg production. However, Nwokolo and Sim (58) observed reduced egg production when unpelleted barley diets were fed. A combination of barley and corn improved egg production and feed efficiency when compared to either grain used alone (46). Coon et al. (21) reported egg production rates and egg weight were similar for barley and corn diets. Sell (67), Sell et al. (68), and Dunstan (24) observed similar results. Barley gave performance similar to corn when supplemented with fish meal but was inferior to corn when supplemented with soybean meal (54). Pelleted barley-canol a meal resulted in production rates equivalent to wheat-soybean meal or barley-soybean meal diets (59). Barley fed as the sole grain source will support egg production but not body weight (7). This situation occurred most often with birds during peak production. The critical time period is from 20 to 40
wk of age, during which hens are increasing feed consumption to meet both egg production and body tissue demands (11). A combination of grains should result in more consistent performance. Coon et al. (21) suggested the use of barley in layer diets can be beneficial for regulating egg size and minimizing body weight gain in post peak layers, if barley is priced low enough to offset its increased feed consumption and lower utilization rate compared to a corn-based diet. The use of barley in full-feed layer programs would allow egg producers to restrict nutrient intake without the use of automated weighing facilities associated with limit feeding. LOW-density diets with barley may be of benefit for older, obesity-prone hens. Several researchers have observed that daily feed consumption of barley diets was greater than corn diets (15, 21, 49). Conditions that affect intake such as hot weather or inadequate ventilation may affect barley-fed birds more than those given a more energy-dense diet (11). Inclusion of dietary fat may reduce the effects of heat stress (33). Cold conditions that increase maintenance requirements may also have an effect on hens that are not able to maintain nutrient intake. The problems related to p-glucans should be less critical with laying hens since older birds are less affected (19). This may be related to the declining impact gut microflora have on older birds, and/or the reduced need for food intake per unit of body weight. Layers housed in cages will have less problems contending with sticky droppings than broilers maintained on litter. One opinion for using enzymes in laying hen diets is reduction of dirty eggs. However, Campbell and Classen (11) did not observe a higher incidence of dirty eggs in barley diets fed to caged layers. Age and facilities are an important factor. Feeding barley in the form of crumbles should provide increased intake thereby increasing egg production (60). However, Gillingham et al. (34) found no advantage to pelleting barley or corn for laying hens. Fat additions from 3 to 5% may have merit with low bushel weight barley. Barley inhibits the absorption of xanthophyll pigments and will reduce yolk pigmentation. Barley grown under dry climatic conditions will further reduce pigmentation of the yolk (48). This problem cannot be overcome by feeding low levels of antibi-
FEEDING BARLEY TO POULTRY: A REVIEW
otic. When reduced pigmentation of the yolk occurs, the inclusion of a high level of barley may aggravate the problem. A small amount of alfalfa meal could improve yolk pigmentation. Layers and Hull-less Barley
The most suitable use of nonenzyme-treated hull-less barley is in laying hen diets. Anderson et al. (2) reported favorable results with hull-less barley. Guillaume and Calet (39) compared hull-less barley at three dietary levels (10, 20, and 30%) to wheat or corn and found no detrimental affect on egg production, egg weight, or feed intake. In a second study, Guillaume (38) reported similar performance with hull-less barley at 30% of the diet; however, both laying rate and feed conversion were slightly depressed at a 60% inclusion level. Classen et al. (19) substituted hull-Ies barley for wheat at 0, 20, 40, 60, or 80% of the diet. They also compared hull-less and conventional barley at 0, 36, and 71 % of the diet to wheat. Hull-less barley was equivalent to or s.ightly superior to wheat in both trials. Hull-less barley appeared to be more acceptable for laying hens then conventional barley. Turkeys
Barley has been found to retard growth promotion in turkey poults (28, 51, 52, 61). Although body weight and abdominal fat were reduced, percent breast meat was increased by barley diets compared to corn diets (40). Reduced amounts of abdominal fat were also observed in broilers fed barley when compared to those fed wheat (70). The decision to use barley as a feed ingredient depends on flock performance and feed prices. Grimes et al. (37) observed that the net return when feeding corn was greater than feeding barley one year, but was reversed the next year. Body weight and feed-to-gain values are increased by ~-glucanase treatment of barley diets (28). Improved performance was observed in birds fed barley or hull-less barley diets up to 4 wk of age when ~-glucanase treatment was used (66). Enzyme treatment had little or no effect on performance from 4 wk to slaughter, although weight gains and feed efficiency tended to be slightly higher in
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groups fed enzyme-supplemented diets. Enzyme treatment of either conventional of hull-less barley improved weight gain by 2 to 3% through 13 wk of age, increased feed efficiency 1.8 to 2.5%, and improved carcass finish. Also noted was improved litter condition. This could be a significant economic factor in confinement feeding of turkeys. Turkeys given the enzyme-treated barley or hullless barley beginning at 4 wk of age had a 3 to 5% improvement in feed conversion during the grower period, as well as 6% improvement in final live weights compared to untreated groups (64). Carcass grades were also improved from 85 to 96% Grade A. Supplemental fat may be necessary to maximize performance. It can be concluded that enzyme supplementation of barley or hull-less barley diets for turkeys is beneficial. Conclusions
A greater variety of feed sources offers a tremendous economic opportunity for the poultry industry. Barley is an acceptable grain source for poultry. The lower energy content of barley caused by the hull may be partially compensated for by an increase in feed consumption. Dietary enzyme supplementation in certain cases greatly improved the utilization of barley, especially for rapidly growing birds. The decision to utilize barley in a poultry feeding program cannot be determined by cost per unit of feed but rather by cost per unit of gain. Literature Cited 1. American Society of Agricultural Engineers. 1983. Method of determining and expressing fineness offeed materials by sieving. In Agricultural Yearbook of Standards, ASAE. p. 325-326. 2. Anderson, J. 0., R. K. Wagstaff, and D. C. Dobson. 1960. Value of barley and hulless barley in rations for laying hens. Poult. Sci. 39(Suppl.1):123O. 3. Anderson, J. 0., D. C. Dobson, and R. K. Wagstaff. 1961. Studies on the value of hulless barley in chick diets and means of increasing this value. Poult. Sci. 40:1571-1584. 4. Arscott, G. H., L. E. Johnson, and J. E. Parker. 1955. The use of barley in high-efficiency broiler rations. 1. Influence of methionine grit and stabilized animal fat on efficacy of utilization. Poult. Sci. 34:
655-662. 5. Behnke, K. C. 1983. In: Particle Size Reduction in the Feed Industry. Kansas State Univ., Manhattan, KS p.C-1. 6. Bell, D. E. and G. L. Bradley. 1989. The efficacy of an amylase/protease, Ban-120 (R), improving the feed value of barley in pullet diets. Poult. Sci. 68(Suppl. 1):170. 7. Berg, L. R. 1961. Effect of adding enzymes to barley diets and different ages of pullets on laying house performance. Poult. Sci. 40:
34-39.
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8. Boldaji, F., M. P. Goeger, H. S. Nakaue, G. H. Arscotts, and T. F. Sawaje. 1986. Apparent, true and nitrogen-corrected metabolizable energy values of different varieties of triticale, wheat and barley in poultry. Nutr. Rep. Int. 33:499-503. 9. Bourne, D. T. and J. S. Pierce. 1970. l3-glucan and I3-glucanase in brewing. J. Inst. Brew. 76:328-335. 10. Burnett, G. S. 1966. Studies of viscosity as the probable factor involved in the improvement of certain barleys for chickens by enzyme supplementation. Br. Poult. Sci. 7:55-75. 11. Campbell, G. L. and H. L. Classen. 1989. Commercial application of enzyme technology in feeding barley to poUltry. Pacific NW Anim. Nutr. Cont. pp. 65-73. 12. Campbell, G. L., H. L. Classen, and G. M. Ballance. 1986. Gamma irradiation of cereal grains for chick diets. J. Nutr. 116:560-569. 13. Campbell, G. L., H. L. Classen, and K A. Goldsmith. 1983. Effect of fat retention on the rachitogenic effect of rye fed to broiler chicks. Poult. Sci. 62:2216-2223. 14. Campbell, G. L, H. L. Classen, and R. E. Salmon. 1984. Enzyme supplementation of barley diets for broilers. Feedstuffs, May 7. pp. 26-27. 15. Campbell, L. D. and W. Guenter. 1985. Barley as an energy source for laying hens. Poult. Sci. 64{Suppl. 1):74. 16. Cantor, A. H., A. J. Pescatore, T. H. Johnson, and W. K Pfaff. 1989. Influence of beta-glucanase additions to barley-based diets for broiler chicks. Poult. Sci. 68{Suppl. 1):24. 17. Cantor, A. H., A. J. Pescatore, T. H. Johnson, and W. K Pfaff. 1989. Influence of beta-glucanase allzyme on performance of broiler checks fed barley-based diets. In: Biotechnology in the Feed Industry. pp. 161-166. Alltech Technical Publications, Nicholasville, KY. 18. Classen, H. L., G. L. Campbell, B. G. Rossnagel, R. Bhatty, and R. D. Reichert. 1985. Studies on the use of hulless barley in chick diets: Deleterious effects and methods of alleviation. Can. J. Anim. Sci. 65: 725-733. 19. Classen, H. L., G. L. Campbell, G. G. Rossnagel, and R. S. Bhatty. 1988. Evaluation of hulless barley as replacement for wheat or conventional barley in laying hen diets. Can. J. Anim. Sci. 68:1261-1266. 20. Classen, H. L., G. L. Campbell, and J.W.D. Grootwassink. 1988. Improved feeding value of Saskatchewan·grown barley for broiler chickens with dietary enzyme supplementation. Can. J. Anim. Sci. 68:1253-1259. 21. Coon, C. N., I. Obi, and M. L. Hamre. 1988. Use of barley in laying hen diets. Poult. Sci. 67:1306-1313. 22. Coon, C. N., R. Shepler, D. McFarland, and J. Nordheim. 1979. The nutritional evaluation of barley selections and cultivars from Washington State. Poult. Sci. 58:913-918. 23. DeSilva, S. K, K Hesselman, and P. Aman. 1983. Effects of water and beta-glucanase treatment on non·starch, polysaccharides in endosperm of low and high viscosity barley. Swed. J. Agric. Res. 13: 211~19.
24. Dunstan, E. A. 1973. The performance of laying hens on diets using barley as the main energy source. Aust. J. Exp. Agri. Anim. Husb. 13: 251~.
25. Edney, M. J., H. L. Classen, and G. L. Campbell. 1986. Application of a simple radial gel diffusion assay for endo-l3-glucanase activity in dietary enzyme supplements. Poult. Sci. 65:72-77. 26. Edney, M. J., G. L. Campbell, and H. L. Classen. 1989. The effect of beta·glucanase supplementation on nutrient digestibility and growth in broilers given diets containing barley, oat groats or wheat. Anim. Feed. Sci. Technol. 25:1~. 27. Ferket, P. 1989. Turkey producers examine feeding potential of barley. Feedstuffs, January. p. 30. 28. Ferket, P. R., C. E. Brewer, and J. L. Grimes. 1989. Effect of level of supplementall3-glucanase in barley-soy diets on the performance of marketturkey toms. Poult. Sci. 68{Suppl. 1):181. 29. Ferket, P. R., C. E. Brewer, and J. L. Grimes. 1989. Encapsulation of l3-glucanase supplemented to barley-soy diets of market turkey toms. Poult. Sci. 68{Suppl. 1):182. 30. Forrest, I. S. and T. J. Wainwright. 1977. The mode of binding of beta·glucans and pentosans in barley endosperm cell walls. J. Inst. Brew. 83:116-122.
31. Fry, R. E., J. B. Allred, and L. S. McGinnis. 1957. Influence of watertreatment on nutritional value of barley. Proc. Soc. Exp. Bio. Med. 95: 249-251. 32. Fry, R. E., J. B. Allred, L. S. Jensen, and J. McGinnis. 1958. Influence of enzyme supplementation and water treatment on the nutritional value of different grains for poults. Poult. Sci. 37:372~75. 33. Fuller, H. L. 1986. The value of dietary fat in poultry nutrition. Prot. Anim. Sci. 2(2):10-17. 34. Gillingham, J. T., G. T. Davis, A. F. Beeckler, T. W. Wilcox, and E. Guenthner. 1960. The effect of pelleting of com, barley, and wheat mixed feeds on laying rations. Mont. Nutr. Conf. p. 71-73. 35. Gohl, B., S. Alden, K. Elwinger, and S. Thomke. 1978. Influence of beta·glucanase on feeding value of barley for poultry and moisture content of excreta. Br. Poult. Sci. 19:41-47. 36. Gohl, B. and S. Thomke. 1976. Digestibility coefficients and metabolizable energy of barley diets for layers as influenced by geographical area of production. Poult. Sci. 55:236~2374. 37. Grimes, J. L, C. E. Brewer, and J. F. Ort. 1989. Effect of various feed grains on profitability and body composition of large white market turkeys. Poult. Sci. 68{Suppl. 1):183. 38. Guillaume, J. 1977. Notes sar I'utilisation des orges francaises dans l'a1imentation des volailles. 1. Utilisation de I'orge nuw dans l'a1imentation de lapoule pondeuse. Ann. Zootech. 26:105-111. 39. Guillaume, J. and C. Calet. 1973. Orge et avoine nues dans l'a1imentation du poulet et de la pondeuse. J. Rech. Avic. Cunic. 73:173-178. 40. Halvorson, J. C., P. E. Waibel, E. M. Oju, S. L. Noll, and M. E. EI Halawani. 1991 . Effect of diet and population density on male turkeys, under various environmental conditions. 2. Body composition and meat yield. Poult. Sci. 70:935-940. 41. Henry, R. J. 1985. A comparative study of the total beta-glucan content of some Australian barleys. Aust. J. Exp. Agric. 25:424-427. 42. Hessleman, K. and P. Aman. 1986. The effect of beta-glucanase on the utilization of starch and nitrogen by broiler chickens fed on barley of low- or high·viscosity. Anim. Feed Sci. Technol. 15:83-93. 43. Hessleman, K, K. Elwinger, M. Nilsson, and S. Thornke. 1981. The effect of l3-glucanase supplementation, stage of ripeness, and storage-treatment of barley in diets fed to broiler chickens. Poult. Sci. 60: 2664-2671. 44. Hesselman, K, K Elwinger, and S. Thornke. 1982. Influence of increasing levels of beta-glucanase on the productive value of barley diets for broiler chickens. Anim. Feed Sci. Technol. 7:351~. 45. Hesselman, K and S. Thomke. 1982. Influence of some factors on development of viscosity in the water-extract of barley. Swedish J. Agric. Res. 12:17-22. 46. Horani, F. and J. L. Sell. 1977. Effect of feed grade animal fat on laying hen performance and on metabolizable energy of rations. Poult. Sci. 56:1972-1980. 47. Jensen, L. S., R. E. Fry,J. B.A1lred, andJ. McGinnis. 1957. Improvement in the nutritional value of barley for chicks by enzyme supplementation. Poult. Sci. 36:919-921 . 48. Karwnajeewa, H. and I. Bagot. 1977. Effect of litter condition, antibiotics, barley and lucerine meal on egg yolk color and crossbred layers. Aust. J. Exp. Agric. Anim. Husb. 17:926-933. 49. Lillie, R. J. and C. A. Denton. 1968. Evaluation of four cereal grain and three protein level combinations for layer performance. Poult. Sci. 47:1000-1004. SO. Mannion, P. F. 1981. Enzyme supplementation of barley based diets for broiler chickens. Aust. J. Exp. Agric. Anim. Husb. 21:296-3)2. 51. Moran, E. T., Jr. and J. McGinnis. 1965. The effect of cereal grain and energy level of the diet on the response of turkey poults to enzyme and antibiotic supplements. Poult. Sci. 44:1253-1261. 52. Moran, E. T., Jr. and J. McGinnis. 1968. Growth of chicks and turkey poults fed western barley and corn grain-based rations: Effect of autoclaving on supplemental enzyme requirement and asymmetry of antibiotic response between grains. Poult. Sci. 47:152-158. 53. Moss, B. R. 1980. Layers vote for barley. MSU. Anim. Range Res. Highlights. p.41. 54. Mundheim, H. and J. Opstvedt. 1981. The value of herring-type fishmeal and soybean meal as protein supplements to poultry diets
FEEDING BARLEY TO POULTRY: A REVIEW
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based on different types of cereals. I. Comparison of fish-meal and soybean meal in maize-based and barley/wheat-based layer diets. Acta Agric. Scand. 31 :287-298. NRC. 1982. United States-Canadian Tables of Feed Composition. (3rd Ed.) National Academy Press, Washington, DC. NRC. 1984. Nutrient Requirements of Poultry (8th Ed.) National Academy Press, Washington, DC. Nwokolo, E. and J. Sim. 1989. Barley and full-fat canola seed in broiler diets. Poult. Sci. 68:1374-1380. Nwokolo, E. and J. Sim. 1989. Barley and full-fat canola seed in layer diets. Poult. Sci. 68:1485-1489. Nwokolo, E. N., J. S. Sim, and A. R. Robblee. 1987. Barley and canola seeds in laying hen diets. Annual Feeders' Day Rep., Univ. Alberta 66:39-41. Petersen, C. F. 1960. The value of barley in laying rations as influenced by pelleting, enzyme additions and laying house temperatures. Mont. Nutr. Conf. p. 74-77. Potter, L. M., A T. leighton, Jr., andC. E. Howes. 1971. The effects offish meal, methionine and different cereal grains in diets of young tUrkeys. Poult. Sci. 50:1100-1108. Rickes, E. L., E. A Ham, E. A Moscatelli, and W. H. Ott. 1962. The isolation and biological properties of a beta-glucanase for B. subtilis. Arch. Biochem. Biophys. 96:371--175. Rotter, B. A, W. Guenter, and R. R. Marquardt. 1989. Effects of enzyme supplementation and standard pelleting or high temperature conditioning on the performance of broiler chickens fed wheat or barley-based diets. Poult. Sci. 68(Suppl1):126. Rotter, B. A., R. R. Marquardt, and W. Guenter. 1989. Optimizing responses from enzyme in poultry and pig diets: New methods for ensuring responses. In: Biotechnology in the Feed Industry. pp. 149-159A1ltech. Technical Publications, Nicholasville, KY.
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65. Rotter, B. A., M. Neskar, R. R. Marquardt, and W. Guenter. Effects of different enzyme preparations on the nutritional value of barley in chicken diets. 1989. Nutr. Rep. Int. 39:107-119. 66. Salomon, R. E., V. I. Stevens, H. l. Classen, and G. L. Campbell. 1986. Enzyme supplementation of cereals in diets for growing turkeys. NWAnim. Nutr. Cont. 21:1-11. 67. Sell, J. L. 1971. Barley and wheat for laying hens. Feedstuffs 43(10): 31--13. 68. Sell, J. L., F. Horani, and R. L. Johnson. 1975. Dietary fat and the utilization of laying hens of rations based on com, oats or barley. Poult. Sci. 54:1814. 69. Sibbald, I. R. 1976. The effect of grinding on the true metabolizable energy value of hulless barley. Poult. Sci. 61 :2509-2511. 70. Sim, J. S. and E. N. Nwokolo. 1987. Barley and full fat canola seeds in broiler diets. Annual Feeders' Day Rep., Univ. Alberta. 66:35-39. 71. Thomas, J. M., L. S. Jensen, and J. McGinnis. 1961. Further studies on the role of microbial fermentation in the nutritional improvement of barley by water treatment. Poult. Sci. 40:1209-1213. 72. Todorov, N. A 1988. Cereals, pulses and oil seeds. livest. Prod. Sci. 19:47-95. 73. White, W. B., H. R. Bird, M. L. Sunde, and J. A. Marlett. 1983. Viscosity of I3-D glucan as a factor in the enzymatic improvement of barley for chicks. Poult. Sci. 62:853-862. 74. White, W. B., H. R. Bird, M. L. Sunde, N. Prentice, W. C. Burger, and J. A. Marlett. 1981. The viscosity interaction of barley Beta-glucan with trichoderma viride cellulose in the chick intestine. Poult. Sci. 60: 1043-1048. 75. Willingham, H. E., K. C. leong, L. S. Jensen, and J. McGinnis. 1960. Influence of geographical area of production on response of different barley samples to enzyme supplements or water treatment. Poult. Sci. 39:103-108.
Feeding Barley to Poultry: A Review1 S. L. BOYLES and R. L. JOHNSON
North Dakota State University Fargo, ND 58105
K. B. KOCH
Northern Crops Institute Fargo, ND 58105 Abstract
Barley is utilized to best advantage in poultry diets when consideration is given to the class of bird being fed and the desired level of performance. As with other cereal grains barley must be ground to achieve maximum utilization when used in poultry diets. The ~-glucans inherent to most barleys can create problems for young birds and birds raised on litter. The amount of barley in broiler diets can gradually by increased as the birds become adapted to it. When poultry are fed barleybased diets, reduced variability in performance and improved growth can be obtained through the use of enzyme supplementation. Enzyme supplementation is not required in iayer diets that contain barley. However, during peak production periods barley should not be used as the sole grain components. Young turkeys responded to enzyme supplementation of barley diet with improved average daily gains and feed efficiencies. (Key Words: Barley, Poultry, p-glucanase.) Introduction
It is generally understood that barley contains higher fiber and lower energy values than either wheat or corn (55, 56). Energy-dense diets have become the norm in the poultry industry. Because cereal grains can supply 60 to 85% of the energy contained in such diets (72), barley's lower energy and high fiber values may preclude its use (11).
1Approved for publication by Director of the North Dakota Agric. Exp. Sta. Reviewed by L. W. Luther and R. H. Stock.
Barley has been considered a nontraditional feedstuff for poultry and as such is perhaps underutilized. Under certain circumstances its use could yield reduced production costs. Results of a turkey feeding study showed that a barley-soybean meal diet provided a $361ton savings when compared to a corn-soybean meal diet (27). Turkeys fed the corn-soybean meal diet gained more weight per pound of feed consumed, but the cost of gain during the study favored the barley-soybean meal diet by $.05/1b of weight gained. Feed Preparation
Poultry diets are fed in a mash (meal), pelleted, or crumbled form. Particle size reduction of whole grains is required when feeding poultry. Particle size reduction facilitates the mixing of ingredients, provides increased pelleting efficiency and pellet quality, and perhaps most importantly improves digestion through exposure of increased surface area (5). The degree of particle size reduction is limited by practical considerations. Sibbald (69) found when all ground material was less than 841 J.l in diameter with more than 95% less than SOO J.l, "true metabolizable energy" values of barley were reduced (69). Particle sizes referred to as "fine" or "medium" (700 to 1,000 J.l) in the literature are preferred for swine and poultry (65). More descriptive terminology for defining particle size is provided by ASAE Standard-S319 (1). Pelleting or crumbling of poultry feeds offers several advantages including improved feed-to-gain ratio, prevention of selective feeding, more uniform intake of nutrients, reduced feed wasting, improved palatability, and improved handling characteristics (25). When high-fiber feeds, such as those contain-
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BOYLES ET AL.
ing barley, are pelleted, an improvement in energy density is observed. Performance of poultry fed barley-based diets can be improved by the addition of dietary betaglucanase (f3-glucanase). f3-glucanase activity is relatively stable to pH above 1 for 30 min and temperatures up to 60 C for 10 min. Edney et al. (25) observed endo-f3-glucanase activity to be 100, 104, 81, 88, 98, and 42% at 7, 5, 4, 3, 2, and 1 pH, respectively. There was a 20 to 36% decrease in f3glucanase as a result of pelleting (25). Variability in temperature, time of exposure, and moisture conditions during the pelleting process will affect enzyme activity loss. Steam conditioning of feed mash to moisture levels of 15% and greater is commonly required to produce quality pellets. One possible way to protect f3-glucanase during pelleting would be to encapsulate it in wax. However, encapsulation using beef fat impeded enzyme availability (29). Enzymes can be added in liquid form and sprayed on the feed after pelletization. Water treatment increased the nutritive value of barley (31). Hesselman et al. (44) demonstrated that high-moisture storage of barley prior to use in feed improved chick growth. Other researchers have confirmed the benefits of water treatment (32, 71). However, water addition has proved to be impractical in most poultry feeding systems. Beta-glucans
Barley is not extensively used in poultry diets because of necrotic enteritis, dehydration, and sticky droppings, and problems associated with it. Beta-glucan (f3-glucan) a component of the endospermal cell walls of barley has been identified as the primary causative agent. f3-glucan is a polymer composed of f31-4 linked glucose units interspersed with f31-3 bonds that prevent interchain aggregation (30). The f3-glucan content of a barley kernel may represent 2 to 10% of the total when expressed on a weight basis. A mean f3-glucan content of 7% was reported by Henry (41) for Australian barleys. The detrimental effect of f3-glucan is primarily attributed to its ability to absorb and control water.. In solution f3-glucan is highly viscous (10, 71, 74). Materials such as f3-glucan impede the digestion and absorption of nutrients by enclosing them
within a gel-like matrix (11, 13, 26). Because fat is absorbed as a large conglomerate particle its assimilation is affected more than other nutrients by containment within the gel-like matrix (11, 13, 26). Poultry lack the appropriate enzyme system needed to reduce the matrix and thereby alleviate the problem. When barley-based diets are consumed by poultry, the problem of reduced nutrient assimilation is coupled to increased transit time through the gut. The net effect is reduced nutrient assimilation per unit of time. Young poultry are more affected than adult birds by this phenomenon. Most research has shown that a reduction in the viscosity of digesta using enzyme degradation produced positive results. Work by Burnett (10) identified f3-glucanase as the effective enzyme contained in previous crude enzyme preparations. The principle effect of dietary f3-glucanase was reduced matrix formation by f3-glucan, which allowed degradation of endosperm cell wall by other dietary enzymes and resulted in the exposure of intracellular starch and protein to endogenous digestive enzymes (42, 62). A mixture of dietary enzymes, such as f3-glucanase and a-amylase, may maximize weight gain and reduce sticky droppings. The 1989 cost associated with treatment of barley and barley-based diets with dietary f3-glucanase was about $3.00Iton (27). In addition to the detrimental effect of f3-glucan, barley has been found to increase levels of microbial activity in the intestine (13, 73). It has been suggested that this increased microbial activity is due to the slower rate of passage observed with barley-based diets. Chicks fed barley exhibited a greater response to antibiotics than those fed wheat or corn. Chicks fed barley supplemented with f3-glucanase had lower mortality rates than those fed barley without f3-glucanase or a cornbased diet (16, 17). Climatic factors have been found to influence the feeding value of barley by altering the f3-glucan content (36). Hesselman and Thomke (45) reported barley grown under warm climatic conditions in~ creased water extract viscosity. Increased f3-glucan content has been associated with increased levels of cell wall and kernel hardness (41). Drought conditions tended to elevate f3-glucan deposition. Barley grown in low rainfall regions of the Western United States responded to enzyme supplementa-
FEEDING BARLEY TO POULTRY: A REVIEW
tion whereas barley from regions with greater rainfall failed to respond in a like manner (75). Increased moisture during the ripening season or after harvest when the grain is stored has been associated with lowered digesta viscosity (43). Poultry feeders and feed manufacturers would benefit from development of techniques that would define the conditions under which high levels of [3glucans could be expected in barley. With such information certain batches of grain could be diverted from feed use or treated with enzymes before being used as feed. The long-term solution may be reduced [3-glucan content through plant breeding. Agronomic practices also influence [3glucan levels. Delaying ripening until cooler weather through delayed seeding or fertilization may reduce [3-glucan levels. Chicks
Barley contains between 1.5 and 8.0% [3-glucans (9) which are suspected to cause the high intestinal viscosity and wet sticky droppings observed in chicks fed diets containing barley (23, 50). Supplementation of barley diets with [3-glucanase has resulted in increased gain when used with chicks (6, 44). Supplementation of diets with a mixture of [3-glucanase and protease resulted in heavier body weights and improved feed-to-gain (FIG) ratios (57). Berg (7) improved the growth of chicks from 0 to 8 wk with enzyme supplementation, but found no response from 8 to 21 wk. However, littler conditions were improved for all the chicks receiving enzyme supplementation. Broilers
To date barley has not been utilized to any great extent in broiler diets. Currently the feed industry and broiler producers favor cereals with lower fiber contents and higher energy values, such as corn and wheat. Birds fed barley diets usually have lower body weights and poorer FIG ratios than corn- or wheat-fed broilers (20). Pelleted barley may prove to be similar to wheat in production value (63). Rotter et al. (64) observed that performance of broilers fed hulled barley was equal to that of birds fed wheat. However, their FIG
3
ratios were somewhat inferior due to the presence of increased levels of fiber. These differences could be reduced by reformulating diets based on an equivalent nutrient density basis or through addition of dietary fat. Ingestion of [3-glucans causes increased water consumption. This, along with the viscous condition in the gut, results in the associated problems of wet litter and carcass cleaning. The addition of [3glucanase to broiler diets that contain barley reduced the viscous condition within the intestine (42) and aided in alleviating the problem of wet litter (35). Campbell et al. (14) observed that the time required to reach market weight was increased by 4 to 5 d when barley diets without enzyme supplementation were compared to a typical broiler diet. This time difference was reduced to 1.5 d when enzyme supplementation was used. In addition, feed costs per unit of live body weight were less for the enzyme-supplemented barley diets. Other research supports the use of enzymes in broiler diets containing barley (18, 42, 43, 65). Although observed improvement is greatest during the starter phase, it is suggested that enzyme treatments be continued throughout the growth period. Coon et al. (22), Campbell et al. (12), and Classen et al. (20) reported that enzyme addition to a barley-based diet not only improved overall performance but also reduced the variability in weight gain and feed conversion efficiency. This resulted in more uniform flocks. Metabolizable energy content of barley can vary with variety (8). A reduction of this variability would increase the accuracy of diet formulation and reduce the risk of unpredictable performance. Campbell and Classen (11) devised a system they called a "sliding density" program. Under the guidelines of the program the diet density is gradually reduced and the barley level increased throughout the feeding period. Typically the initial density is 96% (starter diet), which is reduced to 94 and 92% in the grower and finisher diets, respectively. This corresponds to barley incorporated at 40,60, and 80%, with fat ranging from 3 to 4%. The economics of this program do not differ substantially from a continuous low density-high barley feeding program. However, the slower growth for the first 3 wk of age is largely eliminated. An alternative
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BOYLES ET AL.
would be to feed a conventional starter (or prestarter) diet, with barley introduced in the grower and finisher diets. Chicks and HUll-less Barley
The absence of the fibrous hull should reduce objections to barley when used as a poultry feedstuff. However, several reports have indicated unfavorable results when hull-less barley was fed to broiler chicks (12, 18). Anderson et al. (3) observed that the performance of chicks fed hull-less barley was not different from those fed conventional barley, but gains and feed efficiency were 17% lower than chicks fed corn. Jensen et al. (47) observed that enzyme supplementation improved the performance of chicks. Rotter et al. (65) reported the weight gain and F/G ratios for p-glucanase treated hull-less barley diets were equal to or superior to those of birds fed wheat-corn diets. Layers
Barley is an excellent grain for laying birds provided their energy and amino acid requirements are met (59). Fats and oils can be used to supplement barley-based layer diets (4). Gillingham et al. (34) concluded that corn and barley can be used as the major energy source in laying hen rations. Moss (53) observed that barley can replace wheat in layer rations and may actually lead to greater egg production. However, Nwokolo and Sim (58) observed reduced egg production when unpelleted barley diets were fed. A combination of barley and corn improved egg production and feed efficiency when compared to either grain used alone (46). Coon et al. (21) reported egg production rates and egg weight were similar for barley and corn diets. Sell (67), Sell et al. (68), and Dunstan (24) observed similar results. Barley gave performance similar to corn when supplemented with fish meal but was inferior to corn when supplemented with soybean meal (54). Pelleted barley-canol a meal resulted in production rates equivalent to wheat-soybean meal or barley-soybean meal diets (59). Barley fed as the sole grain source will support egg production but not body weight (7). This situation occurred most often with birds during peak production. The critical time period is from 20 to 40
wk of age, during which hens are increasing feed consumption to meet both egg production and body tissue demands (11). A combination of grains should result in more consistent performance. Coon et al. (21) suggested the use of barley in layer diets can be beneficial for regulating egg size and minimizing body weight gain in post peak layers, if barley is priced low enough to offset its increased feed consumption and lower utilization rate compared to a corn-based diet. The use of barley in full-feed layer programs would allow egg producers to restrict nutrient intake without the use of automated weighing facilities associated with limit feeding. LOW-density diets with barley may be of benefit for older, obesity-prone hens. Several researchers have observed that daily feed consumption of barley diets was greater than corn diets (15, 21, 49). Conditions that affect intake such as hot weather or inadequate ventilation may affect barley-fed birds more than those given a more energy-dense diet (11). Inclusion of dietary fat may reduce the effects of heat stress (33). Cold conditions that increase maintenance requirements may also have an effect on hens that are not able to maintain nutrient intake. The problems related to p-glucans should be less critical with laying hens since older birds are less affected (19). This may be related to the declining impact gut microflora have on older birds, and/or the reduced need for food intake per unit of body weight. Layers housed in cages will have less problems contending with sticky droppings than broilers maintained on litter. One opinion for using enzymes in laying hen diets is reduction of dirty eggs. However, Campbell and Classen (11) did not observe a higher incidence of dirty eggs in barley diets fed to caged layers. Age and facilities are an important factor. Feeding barley in the form of crumbles should provide increased intake thereby increasing egg production (60). However, Gillingham et al. (34) found no advantage to pelleting barley or corn for laying hens. Fat additions from 3 to 5% may have merit with low bushel weight barley. Barley inhibits the absorption of xanthophyll pigments and will reduce yolk pigmentation. Barley grown under dry climatic conditions will further reduce pigmentation of the yolk (48). This problem cannot be overcome by feeding low levels of antibi-
FEEDING BARLEY TO POULTRY: A REVIEW
otic. When reduced pigmentation of the yolk occurs, the inclusion of a high level of barley may aggravate the problem. A small amount of alfalfa meal could improve yolk pigmentation. Layers and Hull-less Barley
The most suitable use of nonenzyme-treated hull-less barley is in laying hen diets. Anderson et al. (2) reported favorable results with hull-less barley. Guillaume and Calet (39) compared hull-less barley at three dietary levels (10, 20, and 30%) to wheat or corn and found no detrimental affect on egg production, egg weight, or feed intake. In a second study, Guillaume (38) reported similar performance with hull-less barley at 30% of the diet; however, both laying rate and feed conversion were slightly depressed at a 60% inclusion level. Classen et al. (19) substituted hull-Ies barley for wheat at 0, 20, 40, 60, or 80% of the diet. They also compared hull-less and conventional barley at 0, 36, and 71 % of the diet to wheat. Hull-less barley was equivalent to or s.ightly superior to wheat in both trials. Hull-less barley appeared to be more acceptable for laying hens then conventional barley. Turkeys
Barley has been found to retard growth promotion in turkey poults (28, 51, 52, 61). Although body weight and abdominal fat were reduced, percent breast meat was increased by barley diets compared to corn diets (40). Reduced amounts of abdominal fat were also observed in broilers fed barley when compared to those fed wheat (70). The decision to use barley as a feed ingredient depends on flock performance and feed prices. Grimes et al. (37) observed that the net return when feeding corn was greater than feeding barley one year, but was reversed the next year. Body weight and feed-to-gain values are increased by ~-glucanase treatment of barley diets (28). Improved performance was observed in birds fed barley or hull-less barley diets up to 4 wk of age when ~-glucanase treatment was used (66). Enzyme treatment had little or no effect on performance from 4 wk to slaughter, although weight gains and feed efficiency tended to be slightly higher in
5
groups fed enzyme-supplemented diets. Enzyme treatment of either conventional of hull-less barley improved weight gain by 2 to 3% through 13 wk of age, increased feed efficiency 1.8 to 2.5%, and improved carcass finish. Also noted was improved litter condition. This could be a significant economic factor in confinement feeding of turkeys. Turkeys given the enzyme-treated barley or hullless barley beginning at 4 wk of age had a 3 to 5% improvement in feed conversion during the grower period, as well as 6% improvement in final live weights compared to untreated groups (64). Carcass grades were also improved from 85 to 96% Grade A. Supplemental fat may be necessary to maximize performance. It can be concluded that enzyme supplementation of barley or hull-less barley diets for turkeys is beneficial. Conclusions
A greater variety of feed sources offers a tremendous economic opportunity for the poultry industry. Barley is an acceptable grain source for poultry. The lower energy content of barley caused by the hull may be partially compensated for by an increase in feed consumption. Dietary enzyme supplementation in certain cases greatly improved the utilization of barley, especially for rapidly growing birds. The decision to utilize barley in a poultry feeding program cannot be determined by cost per unit of feed but rather by cost per unit of gain. Literature Cited 1. American Society of Agricultural Engineers. 1983. Method of determining and expressing fineness offeed materials by sieving. In Agricultural Yearbook of Standards, ASAE. p. 325-326. 2. Anderson, J. 0., R. K. Wagstaff, and D. C. Dobson. 1960. Value of barley and hulless barley in rations for laying hens. Poult. Sci. 39(Suppl.1):123O. 3. Anderson, J. 0., D. C. Dobson, and R. K. Wagstaff. 1961. Studies on the value of hulless barley in chick diets and means of increasing this value. Poult. Sci. 40:1571-1584. 4. Arscott, G. H., L. E. Johnson, and J. E. Parker. 1955. The use of barley in high-efficiency broiler rations. 1. Influence of methionine grit and stabilized animal fat on efficacy of utilization. Poult. Sci. 34:
655-662. 5. Behnke, K. C. 1983. In: Particle Size Reduction in the Feed Industry. Kansas State Univ., Manhattan, KS p.C-1. 6. Bell, D. E. and G. L. Bradley. 1989. The efficacy of an amylase/protease, Ban-120 (R), improving the feed value of barley in pullet diets. Poult. Sci. 68(Suppl. 1):170. 7. Berg, L. R. 1961. Effect of adding enzymes to barley diets and different ages of pullets on laying house performance. Poult. Sci. 40:
34-39.
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8. Boldaji, F., M. P. Goeger, H. S. Nakaue, G. H. Arscotts, and T. F. Sawaje. 1986. Apparent, true and nitrogen-corrected metabolizable energy values of different varieties of triticale, wheat and barley in poultry. Nutr. Rep. Int. 33:499-503. 9. Bourne, D. T. and J. S. Pierce. 1970. l3-glucan and I3-glucanase in brewing. J. Inst. Brew. 76:328-335. 10. Burnett, G. S. 1966. Studies of viscosity as the probable factor involved in the improvement of certain barleys for chickens by enzyme supplementation. Br. Poult. Sci. 7:55-75. 11. Campbell, G. L. and H. L. Classen. 1989. Commercial application of enzyme technology in feeding barley to poUltry. Pacific NW Anim. Nutr. Cont. pp. 65-73. 12. Campbell, G. L., H. L. Classen, and G. M. Ballance. 1986. Gamma irradiation of cereal grains for chick diets. J. Nutr. 116:560-569. 13. Campbell, G. L., H. L. Classen, and K A. Goldsmith. 1983. Effect of fat retention on the rachitogenic effect of rye fed to broiler chicks. Poult. Sci. 62:2216-2223. 14. Campbell, G. L, H. L. Classen, and R. E. Salmon. 1984. Enzyme supplementation of barley diets for broilers. Feedstuffs, May 7. pp. 26-27. 15. Campbell, L. D. and W. Guenter. 1985. Barley as an energy source for laying hens. Poult. Sci. 64{Suppl. 1):74. 16. Cantor, A. H., A. J. Pescatore, T. H. Johnson, and W. K Pfaff. 1989. Influence of beta-glucanase additions to barley-based diets for broiler chicks. Poult. Sci. 68{Suppl. 1):24. 17. Cantor, A. H., A. J. Pescatore, T. H. Johnson, and W. K Pfaff. 1989. Influence of beta-glucanase allzyme on performance of broiler checks fed barley-based diets. In: Biotechnology in the Feed Industry. pp. 161-166. Alltech Technical Publications, Nicholasville, KY. 18. Classen, H. L., G. L. Campbell, B. G. Rossnagel, R. Bhatty, and R. D. Reichert. 1985. Studies on the use of hulless barley in chick diets: Deleterious effects and methods of alleviation. Can. J. Anim. Sci. 65: 725-733. 19. Classen, H. L., G. L. Campbell, G. G. Rossnagel, and R. S. Bhatty. 1988. Evaluation of hulless barley as replacement for wheat or conventional barley in laying hen diets. Can. J. Anim. Sci. 68:1261-1266. 20. Classen, H. L., G. L. Campbell, and J.W.D. Grootwassink. 1988. Improved feeding value of Saskatchewan·grown barley for broiler chickens with dietary enzyme supplementation. Can. J. Anim. Sci. 68:1253-1259. 21. Coon, C. N., I. Obi, and M. L. Hamre. 1988. Use of barley in laying hen diets. Poult. Sci. 67:1306-1313. 22. Coon, C. N., R. Shepler, D. McFarland, and J. Nordheim. 1979. The nutritional evaluation of barley selections and cultivars from Washington State. Poult. Sci. 58:913-918. 23. DeSilva, S. K, K Hesselman, and P. Aman. 1983. Effects of water and beta-glucanase treatment on non·starch, polysaccharides in endosperm of low and high viscosity barley. Swed. J. Agric. Res. 13: 211~19.
24. Dunstan, E. A. 1973. The performance of laying hens on diets using barley as the main energy source. Aust. J. Exp. Agri. Anim. Husb. 13: 251~.
25. Edney, M. J., H. L. Classen, and G. L. Campbell. 1986. Application of a simple radial gel diffusion assay for endo-l3-glucanase activity in dietary enzyme supplements. Poult. Sci. 65:72-77. 26. Edney, M. J., G. L. Campbell, and H. L. Classen. 1989. The effect of beta·glucanase supplementation on nutrient digestibility and growth in broilers given diets containing barley, oat groats or wheat. Anim. Feed. Sci. Technol. 25:1~. 27. Ferket, P. 1989. Turkey producers examine feeding potential of barley. Feedstuffs, January. p. 30. 28. Ferket, P. R., C. E. Brewer, and J. L. Grimes. 1989. Effect of level of supplementall3-glucanase in barley-soy diets on the performance of marketturkey toms. Poult. Sci. 68{Suppl. 1):181. 29. Ferket, P. R., C. E. Brewer, and J. L. Grimes. 1989. Encapsulation of l3-glucanase supplemented to barley-soy diets of market turkey toms. Poult. Sci. 68{Suppl. 1):182. 30. Forrest, I. S. and T. J. Wainwright. 1977. The mode of binding of beta·glucans and pentosans in barley endosperm cell walls. J. Inst. Brew. 83:116-122.
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