Animal Feed Science and Technology 84 (2000) 13±21

Particle size and heat treatment of barley in diets for early-weaned piglets P. Medel, M. GarcõÂa, R. LaÂzaro, C. de Blas, G.G. Mateos* Departamento de ProduccioÂn Animal, ETSI AgroÂnomos, Universidad PoliteÂcnica de Madrid, 28040 Madrid, Spain Received 4 October 1999; received in revised form 18 January 2000; accepted 31 January 2000

Abstract One hundred and twenty male piglets weaned at 20 days and weighing 5.71.0 kg were used in a 28-day trial to evaluate the effect of dietary particle size and heat treatment of barley on performance and total tract apparent digestibility. There were four dietary treatments: coarsely ground barley (4.5 mm screen); ®nely ground barley (2.5 mm screen); micronized and then ®nely ground barley (2.5 mm screen); and ®nely ground (2.5 mm screen) and then expanded barley. All the diets contained 500 g of barley issued from the same batch/kg. There were six replicates of ®ve piglets per treatment. Total tract apparent digestibility of organic matter (OMD), energy (ED) and crude protein (CPD) were assessed from samples taken at 14 and 28 days from each replicate using chromic oxide as indigestible marker. No differences were found between results associated with screen sizes in the raw barley-based diets. Processing of barley caused an increase in starch gelatinization, a decrease in the proportion of large particles (>1.25 mm) and an increase in the proportion of ®ne particles (0.15). Feed ef®ciency and incidence of scours as measured by proportion of animals that needed antibiotic treatment were not affected by diet. Neither particle size nor type of processing affected any of the performance traits studied. The OMD, ED and CPD of the diets are shown in Table 6. Processing of barley tended to increase OMD (0.817 vs. 0.784; pˆ0.07) and ED (0.793 vs. 0.766; pˆ0.13), but neither grinding size nor type of processing affected nutrient digestibility. Digestive ef®ciency was similar among treatments at 14 or 28 days (p>0.15), and no interactions between age and type of diet were detected for any trait. 4. Discussion Grinding size did not affect signi®cantly piglet performance or apparent digestibility of nutrients. Previous results with piglets are confusing due to the wide range of screen sizes used, the type of cereal tested and the differences in complexity of the experimental diets. Reducing particle size is generally expected to improve performance and FCR because the surface area of the ingredients available to the digestive enzymes is increased. At this respect, Wu and Fuller (1974) found a positive response in ADG and FCR for the ®rst week after weaning (28±35 days of age) when the screen size used for maize grinding was decreased from 9.5 to 1.6 mm. However, they did not ®nd any difference when comparing samples prepared with screen sizes of 4 and 1.6 mm. Healy et al. (1994) reported that reducing the particle size of maize from 900 to 300 mm improved ADG and FCR for the ®rst two weeks after weaning (22±36 days of age), but not thereafter. However, reducing the particle size of hard or soft sorghum to the same extent as for maize, did not affect performance for any of the periods studied. An excessive ®neness of the feed induces gastric ulceration and impairs AFI and ADG of pigs (Hedde et al., 1985; Hale and Thompson, 1986; Ayles et al., 1996). Partridge and Gill (1993) suggested that the negative effect of an excessive ®neness of particle size is especially important with wheat, due to the tendency of this cereal to become sticky and pasty in the buccal cavity because of its high gluten content. The problem might be of less importance for barley because particles of 0.2 mm did not affect the performance of growing pigs (Chu et al., 1998). Goodband and Hines (1988) working with barley diets, did not observe any difference in piglet performance from 0 to 14 days, but a positive response of 5% in ADG and in FCR was found from 0 to 35 days when the screen size was reduced from 4.8 to 3.2 mm. On the other hand, Gipp et al. (1995) failed to ®nd differences in performance of 7.5 kg piglets with screen sizes of 6.35, 4.76 or 3.18 mm. Similarly, we did not observe any improvement on performance or digestibility of nutrients due to a reduction of screen size from 4 to 2.5 mm. In the current experiment processing of barley caused a 13% improvement in growth in the ®rst 14 days of the experiment, which agrees with previous results in piglets (Aumaitre, 1976; Medel et al., 1999). However, no differences were detected between 14 and 28 days. Studies conducted with piglets fed barley diets show that processing caused an increase in nutrient digestibility (Chu et al., 1998; Huang et al., 1998). In the current study, processed barley diets showed a 4% higher total tract apparent OMD than the control diet at 14 and 28 days, although this improvement was not associated with better

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performance. The observed improvement of digestibility due to processing agrees with previous data (Medel et al., 1999), and is slightly higher than the values reported by Aumaitre (1976). Expansion and micronization produced similar degrees of starch gelatinization, nutrient digestibility and piglet performance, results that agree with data presented by Vestergaard et al. (1990) and Medel et al. (1999). The digestibility of nutrients was similar when assessed at 14 and 28 days after weaning. Van der Poel et al. (1989) reported higher OMD and CPD in piglets of 7.2 kg than in piglets of 5.8 kg. In the current study, the digestibility of diets was determined with heavier pigs (8.8 and 15.6 kg) which might explain the lack of response with age. In conclusion, decreasing particle size of barley within the range tested (4.0 vs. 2.5 mm) had no signi®cant effect on total tract apparent digestibility or performance of piglets. Heat processing only improved performance in the ®rst 14 days after weaning and no differences between micronization and expansion were detected for any of the traits studied. Based on this experiment, heat processing of barley in diets for early-weaned piglets is recommended. Acknowledgements This research was supported by CICYT project AGF96-1142. Thanks are due to A. Sanz and G. Fructuoso for their help in the management of the animals and to Y. Alegre for typing the manuscript. References Ê man, P., Graham, H., 1987. Analysis of total and insoluble mixed-linked (1±3), (1±4)-û-D-glucans in barley A and oats. J. Agric. Food Chem. 35, 704±709. Aumaitre, A., 1976. EÂvaluation de divers traitements technologiques des ceÂreÂales. Ann. Zootech. 25, 41±51. Aumaitre, A., Peiniau, J., Madec, F., 1995. Digestive adaptation after weaning and nutritional consequences in the piglet. Pig News Inf. 16, 73N±79N. Ayles, H.L., Friendship, R.M., Ball, R.O., 1996. Effect of dietary particle size on gastric ulcers, assessed by endoscopic examination, and relationship between ulcer severity and growth performance of individually fed pigs. Swine Health Prod. 5, 211±216. Association of Of®cial Analytical Chemist, 1995. Of®cial Methods of Analysis, 16th Edition. AOAC, Washington, DC. Chu, K.S., Kim, J.H., Chae, B.J., Chung, Y.K., Han, I.K., 1998. Effects of processed barley on growth performance and ileal digestibility of growing pigs. Asian-Australasian J. Anim. Sci. 11, 249±254. FEDNA, 1999. Normas FEDNA para la formulacioÂn de piensos compuestos. de Blas, C., Mateos, G.G., Rebollar, P.G. (Eds.), FEDNA, Madrid, Spain, 496 pp. GarcõÂa, J., CarabanÄo, R., de Blas, J.C., 1999. Effect of ®ber source on cell wall digestibility and rate of passage in rabbits. J. Anim. Sci. 77, 898±905. Gipp, W.F., Clark, C.K., Bryan, K.S., 1995. In¯uence of barley ®neness of grind on starter, grower and ®nisher swine performance. J. Anim. Sci. 73 (Suppl. 1), 179. Goodband, R.D., Hines, R.H., 1988. An evaluation of barley in starter diets for swine. J. Anim. Sci. 66, 3086± 3093. Hale, O.M., Thompson, L.M., 1986. In¯uence of particle size of wheat on performance of ®nishing swine. Nutr. Rep. Int. 33, 307±311.

P. Medel et al. / Animal Feed Science and Technology 84 (2000) 13±21

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Healy, B.J., Hancock, J.D., Kennedy, G.A., Bramel-Cox, P.J., Behnke, K.C., Hines, R.H., 1994. Optimum particle size of corn and hard and soft sorghum for nursery pigs. J. Anim. Sci. 72, 2227±2236. Hedde, R.D., Lindsey, T.O., Parish, R.C., Daniels, H.D., Morgenthien, E.A., Lewis, H.B., 1985. Effect of diet particle size and feeding of H2-receptor antagonists on gastric ulcers in swine. J. Anim. Sci. 61, 179±186. Hongtrakul, K., Goodband, R.D., Behnke, K.C., Nelssen, J.L., Tokach, M.D., BergstroÈm, J.R., Nessmith Jr., W.B., Kim, I.K., 1998. The effects of extrusion processing of carbohydrate sources on weanling pig performance. J. Anim. Sci. 76, 3034±3042. Huang, S.X., Sauer, W.C., Pickard, M., Li, S., Hardin, R.T., 1998. Effect of micronization on energy, starch and amino acid digestibility in hulless barley for young pigs. Can. J. Anim. Sci. 78, 81±87. Hutton, K, Armstrong D.G., 1976. Cereal processing. In: Swan, H., Lewis, D. (Eds.), Nutrition Conference for Feed Manufacturers. Butterworths, London, UK, pp. 47±63. Kim, I.H., Hancock, J.D., Hines, R.H., Rantanen, M.M., Burham, L.L., 1995. Effects of particle size (1000 and 500 mm in simple and complex diets for weanling pigs. J. Anim. Sci. 73 (Suppl. 1), 179. Lawrence, T.J.L., 1970. Some effects of including differently processed barley in the diet of the growing pig. Anim. Prod. 12, 139±150. Lawrence, T.J.L., 1978. Processing and preparation of cereals for pig diets. In: Haresign, W., Lewis, D. (Eds.), Recent Advances in Animal Nutrition. Butterworths, London, UK, pp. 83±98. Medel, P., Salado, S., Mateos, G.G., de Blas, C., 1999. Processed cereals in diets for early-weaned piglets. Anim. Feed Sci. Technol. 82, 145±156. Partridge, G.G., Gill, B.P., 1993. New approaches with pig weaner diets. In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent Advances in Animal Nutrition. Nottingham University Press, UK, pp. 221±248. Saini, H.S., Henry, R.J., 1989. Fractionation and evaluation of triticale pentosans. Comparison with wheat and rye. Cereal Chem. 66, 11±14. SAS, 1990. SAS1 User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Theander, O., 1991. Chemical analysis of lignocellulose materials. Anim. Feed Sci. Technol. 32, 35±44. Van der Poel, A.F.B., Den Hartog, L.A., Van den Abeele, T.H., Boer, H., Van Zuilichem, D.J., 1989. Effect of infrared irradiation or extrusion processing of maize on its digestibility in piglets. Anim. Feed Sci. Technol. 26, 29±43. Vestergaard, E.M., Danielsen, V., Jacobsen, E.E., Rasmussen, V., 1990. Heat treated cereals for piglets. Beretning Fra Statens Husdyrbrugsforsog 674, 71. Wondra, K.J., Hancock, J.D., Behnke, K.C., Hines, R.H., Stark, C.R., 1995. Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in ®nishing pigs. J. Anim. Sci. 73, 757±763. Wu, J.F., Fuller, M.F., 1974. A note on the performance of young pigs given maize-based diets in different physical forms. Anim. Prod. 18, 317±320.