Efficacy of white rice - Based diets in nursery pigs

10 Nong Lam University, Ho Chi Minh City Efficacy of white rice-based diets in nursery pigs Tung M. Che∗, & Nhan T. M. Nguyen Department of Animal Production, Nong Lam University, Ho Chi Minh City, Vietnam ARTICLE INFO Review Paper Received: March 24, 2018 Revised: May 15, 2018 Accepted: May 31, 2018 Keywords Cereals and rice Digestibility Growth performance Health Nursery pigs ∗Corresponding author Che Minh Tung Email: tung.cheminh@hcmuaf.edu.vn ABSTRACT Rice is a staple cereal consumed by much of the world’s popu- lation but has received relatively little attention as a potential feedstuff for the animal industries in many parts of the world. It may be because its price is relatively high and only a small amount of rice produced is traded (6.2%). India, Thailand and Vietnam play a major role in the world rice export market. Rice is characterized by its high starch content, low fat and dietary fiber content, and lower crude protein content in comparison to other cereals. Rice-based diets have a higher apparent digestibil- ity of nutrients than corn-based diets. Complete replacement of corn with rice in weaned pig diets does not affect growth per- formance, but feed efficiency is improved when corn is replaced with brown rice. Heat processing of rice does not influence di- gestibility and growth performance of pigs. Due to rice’s high digestibility and low fiber content, pigs fed rice-based diets have lower concentrations of volatile fatty acids and viscosity of intesti- nal digesta compared to other cereal-based diets. Moreover, rice has been shown to have potential to ameliorate diarrhea, colo- nization of pathogens, severity of enteric bacterial diseases, and pig removals. The mechanism for this protective function is not fully understood, but it may be, to a certain extent, related to lower fiber content and high digestibility of rice and a so-called “rice factor”. In practice, when availability and cost of rice per- mits, pork producers can benefit from the use of rice-based diets for piglets. Cited as: Che, T. M., & Nguyen, N. T. M. (2018). Efficacy of white rice-based diets in nursery pigs. The Journal of Agriculture and Development 17(3), 10-21. 1. Introduction Rice is a staple cereal consumed by much of the world’s population, and a plethora of studies exist investigating the physical and chemical proper- ties of cooked rice for man. Most of these studies relate to the starch properties of rice, presum- ably because starch constitutes more than 75% of rice’s composition (Pluske et al., 2007; Stein et al., 2016), and hence forms the major carbo- hydrate consumed. The high starch content of cooked rice coupled with a very low non-starch polysaccharide (NSP) level makes cooked rice a ready source of absorbable glucose, and hence en- ergy, for the human population. More recently, there is interest in the use of rice-based oral re- hydration formulas for controlling enteric diseases in children (Iyngkaran & Yadav, 1998; Ramakr- ishna et al., 2000; Gregorio et al., 2016) and ani- mals (Hampson et al., 2001). In contrast, there is less information pertain- ing to the feeding of rice to animals, especially the pig, with respect to effects on production and intestinal “health”, which incorporates en- teric disease. This is predominately because other cereal sources, such as wheat, barley, corn, and sorghum, are used in pig production and can be fed to pigs cheaper than rice. Nevertheless, given the information available from the human liter- ature with respect to the cooking and milling The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 11 properties of rice, potential exists for the use of processed (cooked) rice in certain diets for pigs, especially the young pig. This is particularly when the intestine is compromised by enteric pathogens such as Escherichia coli, the agent of post-weaning colibacillosis (PWC) or, as it is more commonly recognized, post-weaning diar- rhea (PWD). Incorporation of processed rice into such diets has potential to add value to the world rice industry and reduce the pig industry’s re- liance on the use of growth promoting antibiotics. Furthermore, spin-offs into the biomedical field in the control of human enteric pathogens may be possible. Antimicrobial agents are presently the main tool used for control of PWD, and are provided to pigs to treat overt disease, to provide prophy- laxis in situations where disease is liable to occur, and to improve growth rates in the absence of disease. However, problems are arising over the use of antimicrobials in the pig industry. Their long-term use eventually selects for the survival of resistant bacterial species or strains, and genes encoding this resistance also can be transferred to other formerly susceptible bacteria. Currently, a variety of bacterial pathogens of pigs are show- ing resistance to a range of antimicrobial drugs. Not only is this reducing the number of antimi- crobials available to control bacterial diseases in pigs, but this resistance also poses risks to human health. Risks include the transfer of multidrug re- sistant zoonotic pathogens (e.g., Salmonella spp. and Campylobacter spp.) from pigs to humans, the direct or indirect transfer of resistance genes from the porcine intestinal microflora to human bacterial strains, and the presence of antimicro- bial drug residues in pig meat (Hampson et al., 2001). Public concern about these issues is lead- ing to reduced availability or the complete ban- ning of certain antimicrobial agents for use in pig production, as has occurred in certain parts of Europe. Although there are currently no to- tal bans on the use of growth promoting antibi- otics in the Vietnam pig industry, it is imperative to develop alternative means, such as the use of nutrition, both of controlling bacterial infections and promoting growth in pigs without recourse to the use of antimicrobials. Swine rations usually contain a large amount of cereal grains such as corn, barley, wheat, oat, and rice. Among these ingredients, corn is the cereal grain preferred by most pork producers in Viet- nam and many regions of the world. However, other cereal grains may be considered, at times, due to their lowered costs or their positive ef- fects on growth performance and health of young pigs. Cereal grains have different carbohydrate composition which may affect the health of the digestive tract by providing different substrates for microbial activity (Jensen & Jorgensen, 1994; Bach Knudsen et al., 2012). Unfortunately, there are few reliable data to support intelligent selec- tion of the most appropriate cereals for the health of young pigs. Oat, wheat, and barley are ingre- dients with high content of non-starch polysac- charides which can stimulate the growth of com- mensal gut flora (Bach Knudsen, 1991), leading to a healthy digestive tract. In other words, stud- ies of McDonald et al. (1999 & 2001), Hopwood et al. (2004), and Mateos et al. (2006) indicate benefits of rice, which contains almost no fiber. Apparently, more information is needed on both the practical and physiological effects of various cereal grains in the diet of young pigs. The aim of this paper is to review the effects of rice-based diets on growth perfor- mance, digestibility, gastrointestinal parameters, and health of weaned pigs in comparison to other cereal-based diets. 2. Global Rice Production and Trade Rice is widely grown all over the world and a staple food for humans. Approximately 673.8 million metric tons (MMT) of rice are produced annually in the world, with overwhelming ma- jority of this entering the human food markets. Only about 6.2% of rice produced is traded in the global markets. As with most crops, China has a major role in rice production and use, but a minor role in trade. In the 2016 marketing year China accounted for 31.0% of world production of 673.8 MMT (Table 1). The second largest rice producer is India, with a total production of 165.2 MMT in 2016. It may be surprising that India is now emerging as the world’s largest rice exporter with an amount of 10.1 MMT. With a large popula- tion, strong economic growth and internal food price pressures, China could quickly disappear from the rice export market. In contrast, Thai- land and Vietnam, though with smaller amounts of rice production as compared to China, play a major role in the world rice export market. The second largest rice exporter is Thailand at 9.9 MMT for 2016. Vietnam is the third rice exporter www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3) 12 Nong Lam University, Ho Chi Minh City at 6.1 MMT, 15.8% of the world total in 2016. Most of the current price problems are related to exporters withdrawing supplies from the mar- ket and the general rise in all commodity prices. The longer-term structural question of who will produce rice for international markets will con- tinue to influence market prices for years to come. It appears that India, Thailand and Vietnam are more committed to export markets. 3. Chemical Composition of Rice Rice is characterized by its high starch con- tent, low fat and dietary fiber content, and lower crude protein content in comparison to other ce- reals (Table 2). In term of crude protein, rice (8.1- 8.6%) is comparable to corn (8.1%), even with a better balanced essential amino acid profile (Fig- ure 1). Both brown rice and white rice has a higher concentration of essential amino acids, ex- cept for histidine and leucine, than corn. Piao et al. (2002) and Li et al. (2002), however, found that the balance between isoleucine and leucine is better in brown rice than that in corn. Barley (10.8%), oat (11.3%), and wheat (14.0%) have a greater content of crude protein than corn and rice. Figure 1. Essential amino acids in corn and white rice. Data from: Bach Knudsen (1997); Kim et al. (2007); Che et al. (2012). Apart from high contents of crude protein, other cereals also contain a considerable amount of total dietary fiber (> 9.0%) which is much higher than that (1.2%) in rice (Table 2). In con- trast, rice contains a significantly higher level of starch (75.3-87.4%) than other cereals. Regarding the energy content, rice has a higher level (3.54 Mcal/kg) of metabolizable energy (ME) than bar- ley, oat, and wheat. In comparison to corn, al- though both rice and corn have the same gross energy content (Li et al., 2002; Vicente et al., 2008), the ME of rice is lightly greater than that of corn. The higher ME content of rice might be resulted from its higher digestibility. In addition, other cereals, particularly barley, oat and corn, have higher lipid content than white rice. Because of its low fiber content and high starch content, rice might be a good alternative to other cereals in the pig’s diet immediately after wean- ing. It may have a major impact on the digestibil- ity of dietary nutrients and the microbial popula- tions through providing fewer substrates for bac- terial fermentation in the intestinal tract (Pluske et al., 2003; Montagne et al., 2004; Vicente et al., 2008). This in turn may prevent the proliferation of pathogenic bacteria. The interaction between the components of diet (e.g. fiber) and the devel- opment of intestinal bacteria and gut is complex. Thus, a rice-based diet does have an important role to play in intestinal disease and health of young pigs. 4. Effects on Growth Performance Replacement of other cereals with rice in wean- ing diets for pigs has been conducted by several researchers, but most of the research has focused on comparing the effect of substituting rice for corn in the weaned pig’s diet. In a series of exper- iments carried out at the same commercial farm testing whether corn, barley, rolled oat, or rice as the main energy source in the diet for weaned pigs affects growth performance, Che et al. (2012) reported that average daily gain (ADG) of pigs fed the rice diet was significantly higher than that of pigs fed barley or rolled oat diets, but not different from that of pigs fed the corn diet (Table 3). No difference in feed/gain (F/G) was seen among the treatment diets. Average daily feed intake (ADFI) of pigs fed corn, rolled oat, and rice diets were similar, but was significantly higher than that of pigs fed barley diet. In the second experiment, Che et al. (2012) investigated effects of complete replacement of corn with rice in diets and length of rice feeding on growth per- formance of weaned pigs (Table 3). The results showed that there were no significant differences in ADG, ADFI, and F/G. This suggests that rice can substitute for corn in the diet for weaned pigs, reared under commercial conditions, without af- fecting the growth performance of pigs. However, with studies conducted at the univer- The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 13 Table 1. Top paddy rice producers-2016 and rice exporting countries worldwide in 20161 Producers Amount Exporters Amount Million metric ton % Million metric ton % China 208.7 31.0 India 10.1 24.3 India 165.2 24.5 Thailand 9.9 23.9 Indonesia 72.7 10.8 Vietnam 6.1 14.7 Bangladesh 52.1 7.7 Pakistan 4.0 9.6 Vietnam 43.6 6.5 USA 3.3 8.0 Thailand 32.6 4.8 Myanmar 1.4 3.4 Myanmar 28.6 4.2 Cambodia 1.2 2.9 Philippines 18.5 2.7 Uruguay 0.9 2.2 Japan 10.7 1.6 Brazil 0.6 1.4 Brazil 10.6 1.6 Argentina 0.5 1.2 Pakistan 10.3 1.5 Others 3.5 8.4 USA 10.2 1.5 Cambodia 10.0 1.5 World total 673.8 100.0 41.5 100.0 1Data from FAO (2017). Table 2. Chemical composition of cereal grains (as fed) Barley1 Oat1 Wheat1 Corn3 Rice2 Rice3 Protein, % 10.8 11.3 14.0 8.1 8.1 8.6 Ether extract, % 3.0 4.0 1.1 2.9 0.9 2.4 Starch, % 49.7 40.1 57.6 62.1 75.3-87.4 n.a. Dietary fiber, % 18.8 22.8 9.8 9.5 1.2 n.a. Ash, % 4.1 2.6 2.0 1.4 0.5 1.1 ME, Mcal/kg 2.91 2.60 3.30 3.39 3.54 n.a. 1Stein et al. (2016). 2Pluske et al. (2007); Stein et al. (2016). 3n.a.: not available; Li et al. (2002). Table 3. Effects of cereals on growth performance of pigs from d 0 to 42 post-weaning1 Experiment 1 Dietary treatments Corn Barley Rolled oat Rice ADG, g 331a 307c 323bc 337a ADFI, g 495a 462b 489a 504a F:G, g/g 1.49 1.49 1.52 1.49 Experiment 2 Dietary treatments2 Corn (6 wk) Rice (1 wk) Rice (2 wk) Rice (4 wk) ADG, g 307 315 318 307 ADFI, g 455 459 468 446 F:G, g/g 1.35 1.33 1.33 1.33 112 pens of 21 pigs/treatment. Data from Che et al. (2012). 2Pigs were fed rice diets for 1, 2 or 4 weeks and then on a corn diet until the end of experiment. a-cMeans within a row with different superscripts differ (P < 0.05). sity research farms, better performance of weaned pigs has been often reported. Mateos et al. (2006) showed that pigs fed the cooked-rice diet grew faster (12.3%) than those fed the cooked-corn diet. In another experiment using brown rice, Li et al. (2002) found that 50% or complete replace- www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3) 14 Nong Lam University, Ho Chi Minh City ment of corn with brown rice in nursery diets improved the feed efficiency. In comparison to wheat, pigs fed rice-based diets from 46-63 days of age, regardless of low or high dietary protein, ate more, gained faster, and had better feed efficiency than those fed the wheat-based diets (Bonet et al., 2003). Rice has a high level of starch, thus gelatiniza- tion of the starch portion of the grains might improve nutrient utilization and thereby result- ing in a better growth performance. Vicente et al. (2008) evaluated effects of cooked-flaked corn, raw-ground rice, cooked-ground rice, and cooked- flaked rice on performance of weaned pigs for 28 days post-weaning (Table 4). They showed that pigs fed rice consumed more feed (678 vs. 618 g/d), grew faster (466 vs. 407 g/d), and tended to have lower F/G than those fed corn. No differ- ences in growth performance due to heat process- ing of rice were observed. This suggests that heat processing does not affect growth performance of pigs fed rice-based diets. 5. Effects on Nutrient Digestibility Rice-based diets have a higher apparent total tract digestibility of nutrients than corn-based diets. Mateos et al. (2006) found that the di- gestibility of GE, OM, DM, and fat was higher for rice- than for corn-based diets (Table 5), which agrees with the results of Li et al. (2002), Piao et al. (2002) and Vicente et al. (2008). It was also shown that heat processing did not affect the di- gestibility of nutrients in the rice-based diets (Ta- ble 6). A similar result was obtained when corn was replaced with 50% or 100% of brown rice in the diets. The corn-based diet had a signifi- cant lower apparent digestibility of dietary com- ponents than the brown rice-based diet or the diet with 50% replacement of corn. The higher digestibility of a rice-based diet would be likely to explain the improved growth performance in weaned pigs fed rice diets compared to corn di- ets. It is pointed out that fewer substrates for bacterial fermentation might be resulted from a rice-based diet, but ileal digestibility of rice vs. other cereal diets needs to be determined. 6. Gastrointestinal Effects With high digestibility of nutrients and low fiber content, rice-based diets may greatly influ- ence activity of microbial fermentation and in- testinal environment. Hopwood et al. (2004) re- ported that the barley-based diet or the diet with high inclusion level of barley fed to pigs caused a significant decrease in pH of distal colon and feces compared to pigs fed the rice-based diet (Table 7). However, no differences were observed in di- gesta pH in duodenum and ileum of pigs among the treatments. It is obvious that a diet contain- ing high fiber ingredients, like barley, increases the pH in the large intestine via providing fer- mentable substrates to the microbial activity as compared to the rice-based diet. In another ex- periment, different types of fiber such as high- amylose corn starch, lupin isolate, or a combina- tion of both included in a rice-based diet reduced the digesta pH in cecum, proximal colon, and dis- tal colon (Table 8). Further, a rice-based diet re- sulted in a numerically higher pH in the large intestine as compared to a wheat-based commer- cial diet (Pluske et al., 2003). The inclusion of animal or plant protein in a rice-based diet also significantly influenced the digesta pH of the large intestine. The rice diet with animal protein had a higher cecum and colon pH than that with plant protein. The increase in pH is likely to be because of the increased pool of volatile fatty acid (VFA) through the high activity of microbial fermenta- tion in the large intestine. The rice-based diet had a lower total pool of VFA than that with increas- ing levels of barley. It was further indicated that rice-based diets with inclusion of various types of fiber sources produced different amounts of pooled VFA (Table 9). In order to prove that the fiber components added to rice diets increase the production of VFA, McDonald et al. (2001) added a viscous but unfermentable component, carboxymethylcellulose (CMC) to a rice-based diet. They found that no differences in concen- tration of VFA of digesta in the large intestine of pigs. The high level of fiber in the cereals, e.g. bar- ley, caused not only an elevated total pool of VFA and decreased pH but also an increased viscosity. The rice-based diets with different inclusion lev- els of barley resulted in an increase in viscosity in the small intestine of pigs (Figure 2). The vis- cosity in pigs fed the rice-based diet was lower than that in those fed the barley-based diet or the diet with the inclusion of 500 g/kg of bar- ley. Hopwood et al. (2004) reported that the in- take of non-starch polysaccharide was positively The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 15 Table 4. Effects of cereals and heating processing on performance of pigs from d 0 to 28 post-weaning1 Item Corn Rice Cooked-flaked Raw-ground Cooked-ground Cooked-flaked ADG, g2 407 459 482 456 ADFI, g2 618 680 680 672 F:G, g/g 1.52 1.49 1.41 1.47 18 pens of 5 pigs/treatment. Data from Vicente et al. (2008). 2Corn vs. mean of the 3 rice treatments (P < 0.01). Table 5. Effects of cereals on total tract apparent digestibility of dietary components1 Item Cereal source Cooked rice Cooked corn DM, % 83.8a 80.6b OM, % 86.2a 82.9b GE, % 82.7a 79.0b Ether extract, % 60.9a 58.8b CP, % 72.9 72.9 Starch, % 99.2 99.4 18 pens of 4 pigs/treatment; Average of d 6 & 16 post-weaning. Data from Mateos et al. (2006). a-bMeans within a row with different superscripts differ (P < 0.05). Table 6. Effects of cereals and heat processing on apparent total tract digestibility of dietary components1 Item Corn Rice Cooked-flaked Raw-ground Cooked-ground Cooked-flaked DM, % 86.7a 88.1b 88.8b 88.3b OM, % 88.6a 90.6b 91.1b 90.8b GE, % 86.5a 88.4b 89.3b 88.8b CP, % 80.8 80.9 81.6 81.0 18 pens of 5 pigs/treatment; Average of d 5, 14 & 28 post-weaning. Data from Vicente et al. (2008). a-bMeans within a row with different superscripts differ (P < 0.05). Table 7. Digesta pH in various sections of the intestinal tract in pigs fed rice-based diet with different levels of barley1 Item2 Rice:barley (g/kg) 703:0 497:250 275:500 0:750 Duodenum 5.7 5.9 5.7 5.8 Ileum 6.7 6.3 6.6 6.1 Distal colon 6.8a 6.6a 6.1b 5.7b Feces 6.9a 6.9a 6.5b 6.4b 16 pigs/treatment; 210 d after weaning. Data from Hopwood et al. (2004). a-bMeans within a row with different superscripts differ (P < 0.05). correlated with the viscosity of small intestinal content of pigs. The viscosity of digesta is also dependent on, in addition to fiber sources, types of fiber combined in the diet. Addition of high- amylose corn starch and lupin isolate combined to the rice-based diet greatly increased the vis- www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3) 16 Nong Lam University, Ho Chi Minh City Table 8. Digesta pH in different sections of the intestinal tract in pigs fed rice-based diets1 Diet R+AP R+HACS R+LI R+HACS+LI Com Ileum 7.1 7.1 7.3 7.4 6.8 Cecum 6.2a 5.3b 5.5bc 5.4b 5.8ac Proximal colon 6.3a 5.2b 5.4b 5.3b 6.0a Distal colon 6.6a 5.7b 6.0b 6.1b 7.0bc 16 pigs/treatment. Data from Pluske et al. (2003). R = rice, AP = animal protein; HACS = high-amylose corn starch, LI = lupin isolate, Com = commercial diet con- taining wheat. a-cMeans within a row with different superscripts differ (P < 0.05). Table 9. Pools of VFA of digesta in the large intestine in pigs fed rice-based diets1 VFA pool (mmol per pig) Diet R+AP R+HACS R+LI R+HACS+LI Com Cecum 8 18 15 12 11 Colon 19a 45b 45b 27ac 36bc 16 pigs/treatment. Data from Pluske et al. (2003). R = rice, AP = animal protein; HACS = high-amylose corn starch, LI = lupin isolate, Com = commercial diet con- taining wheat. a-cMeans within a row with different superscripts differ (P < 0.05). Figure 2. Viscosity of intestinal contents of pigs fed rice-based diets containing different levels of pearl barley. 6 pigs/treatments; 10 d after weaning. Bars with different superscripts differ (P < 0.05). Data from Hopwood et al. (2004). cosity of ileal digesta if compared to diets with the inclusion of high-amylose corn starch or lupin isolate individually (Pluske et al., 2003). 7. Effects on Pig Health and Diarrhea Rice, when compared to other cereals, has been shown to reduce the diarrhea, intestinal colo- nization of pathogens, and the severity of en- teric bacterial diseases when pigs were challenged with enterotoxigenic Escherichia coli (ETEC) or Brachyspira pilosicoli. Hopwood et al. (2004) in- vestigated the effect of rice-based diet with high inclusion level of barley with or without NSP en- zyme supplementation. They showed that the fe- cal DM did not differ among dietary groups (Ta- The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 17 ble 10), but the post-infection fecal consistency score was different, with pigs receiving the rice- only diet having firmer and better-formed feces than pigs fed either of barley diets. Mateos et al. (2006) reported that pigs fed the cooked-rice diet had a lower diarrhea score than those fed the cooked-corn diet. This indicates that under nor- mal or disease conditions rice-based diets fed to pigs reduce the moisture content of feces. When pigs challenged with ETEC, the ADG for the ex- perimental period was negative for those pigs con- suming diets with barley, and positive for those fed the rice-only diet (Table 11). The intestinal viscosity was also greater in infected pigs fed 500 g/kg of barley compared with those fed the rice- based diet. In another ETEC challenge study, Montagne et al. (2004) showed that ileal and cecal viscosity of pigs fed rice-based diets with animal or plant protein was lower than that of pigs fed wheat-based diet with plant protein. In term of intestinal colonization of pathogens, culture of mucosal scrapings revealed greater pro- liferation of ETEC within the small and large in- testines of pigs consuming diets containing bar- ley than those eating the rice-only diet (Table 12). In addition, the ETEC were more domi- nant within the microbiota of pigs eating barley compared with that within pigs eating rice. At each of the intestinal sites swabbed there were more ETEC on the culture plates from pigs eat- ing the barley diets compared with those not re- ceiving barley. With Brachyspira pilosicoli inoc- ulation (Figure 3), the period of fecal excretion ranged from 1 to 25 days. The pigs fed the rice diet excreted Brachyspira pilosicoli for a signifi- cantly shorter period than those fed the standard diet containing wheat and barley, regardless of diet forms. They also observed that a higher inci- dence of fecal excretion in all the groups fed the standard diet was accompanied by a significantly higher number of pigs showing clinical signs of disease compared to the pigs fed the rice diet. A similar protective effect of rice-based diets has been seen in pigs experimentally infected with the intestinal spirochete Brachyspira hyodysenteriae, the agent of swine dysentery (Pluske et al., 1996) and Brachyspira pilosicoli, the agent of porcine intestinal spirochetosis (Hampson et al., 2000). The protective effect of such a diet against bac- terial infection has been attributed in part to the high digestibility of its protein and carbohydrates (Siba et al., 1996; Pluske et al., 1998). In piglets, Figure 3. Fecal excretion of Brachyspira pilosicoli by pigs fed various diets and infected experimen- tally in 2 trials. STD=standard diet containing barley and wheat, FLF=fermented liquid feed, LAC=STD + lactic acid, PEL=pelleted STD; 6 pigs/treatment. Adapted from Lindecrona et al. (2004). it is generally thought that diets containing less fiber and highly digestible ingredients, thereby limiting the quantity of fermentable substrates entering the large intestine, are associated with a decrease in the incidence of PWC (Montagne et al., 2003). Such diets may result in less accumula- tion of potential bacterial substrate in the upper small intestine, the primary site of proliferation of the pathogenic E. coli causing PWC (Francis, 2002). One of the primary mechanisms by which toxin-producing bacteria, such as E. coli or Salmonella, initiate secretory diarrhea is the in- crease of water secretion by the small intestinal crypt cells, by a pathway involving cAMP (Keely et al., 2009). In young pigs, the large intestine is incompletely developed and may not be capable of absorbing enough fluid to prevent clinical di- arrhea and dehydration. A component of boiled white rice recently identified and named the rice factor has been shown to block the secretory re- sponse of intestinal crypt cells to cAMP in guinea pigs (Macleod et al., 1995; Mathews et al., 1999). A potential effect of this rice factor has not been demonstrated in other animal species; however, boiled rice has been used for many years in the treatment of diarrhea in humans and is included in various oral rehydration products (Gregorio et al., 2016). The reduction in diarrhea and intestinal colo- nization of enteric pathogens may help prevent infections and improve the pig health. In a se- ries of experiment conducted by Che et al. (2012) www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3) 18 Nong Lam University, Ho Chi Minh City Table 10. Fecal dry matter and consistency score in weaned pigs infected with enterotoxigenic Escherichia coli and fed different diets Item Rice:barley, g/kg1 703:0 275:500 275:500 + Enzyme Fecal DM (g/kg) Over 6d post-weaning 304 295 299 Post-infection 301 292 277 Fecal consistency score2 Pre-infection 1.5 1.8 1.7 Post-infection 2.9a 3.6b 3.7b 1n = 11, 13, & 12 for 0, 500, & 500+NSP Enzyme groups, respectively. Data from Hopwood et al. (2004). 2Score 0-5. a-bMeans within a row with different superscripts differ (P < 0.05). Table 11. Growth and digesta viscosity of weaner pigs killed 3-4 d after infection with enterotoxigenic Escherichia coli Item Rice:barley, g/kg1 703:0 275:500 275:500 + Enzyme Gain, g/d 10.5 -7.8 -27.0 Viscosity, mpa.s Duodenum 1.8 2.1 2.6 Ileum 1.6a 2.3b 2.2ab Small intestine 1.7 2.2 2.6 1n = 11, 13, & 12 for 0, 500, & 500+NSP Enzyme groups, respectively. Data from Hopwood et al. (2004). a-bMeans within a row with different superscripts differ (P < 0.05). Table 12. Proportion of β-hemolytic enterotoxigenic Escherichia coli (ETEC) cultured from intestinal swabs in weaner pigs infected with ETEC and fed different diets Item Rice:barley, g/kg1 703:0 275:500 275:500 + Enzyme Viable CFU/g (log10) 2 Mid-small intestine 1.0a 4.1b 3.5b Proximal colon 2.3a 5.2b 6.0b ETEC (%), intestinal swabs Duodenum 7.5 22.1 26.5 Ileum 11.0a 47.6b 21.4ab Cecum 16.5a 53.2b 53.0b Feces 27.9 44.5 38.8 1n=11, 13, & 12 for 0, 500, & 500+NSP Enzyme groups, respectively. Data from Hopwood et al. (2004). a-bMeans within a row with different superscripts differ (P < 0.05). at the same commercial pig farm, feeding rice- based diets to weaned pigs significantly reduced the pig removal by half, even when pigs were fed rice diets for only one week immediately af- ter weaning (Figure 4). Furthermore, Pluske et al. (2003) showed that the number of antibiotic treatments of pigs was also reduced in pigs fed the rice-only diet compared to a commercial diet and rice-based diets with the inclusion of various fiber sources. Obviously, feeding a rice-based diet improves pig health with evidence of reduced pig removal and number of antibiotic treatment. 8. Conclusions Rice, widely grown over the world, is a highly digestible ingredient and has high potential to be a good feed ingredient for animals. Rice can sub- The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 19 Figure 4. Effect of different cereal-based diets on pig removals 6 weeks post-weaning. (A) Pigs fed diets with different cereals as a main source of energy for 6 weeks post-weaning. (B) Pigs fed corn-based diets for 6 weeks or rice-based diets for 1 (Rice-1), 2 (Rice-2) or 4 (Rice-3) weeks post-weaning. (C) Effects of feeding rice with 0 (Rice-0%), 50 (Rice-50%), 75 (Rice-75%), and 100% (Rice-100%) replacement of corn in diets for 1 week on the overall pig removal over 6 weeks post-weaning. 252 pigs/treatment. a-bMeans with different superscript letters within each experiment differ (P < 0.05). Data from Che et al. (2012). stitute for corn in diets for weaned pigs without affecting the pig’s performance. The rice-based diet appears to be better in growth performance and feed efficiency than a barley- or wheat-based diet. Rice included in diets makes feces less moist and reduces the incidence of diarrhea. Inclusion of rice in diets causes less viscous digesta and ap- pears to prevent the proliferation of pathogens. Feed ingredients in weaning diets that excessively increase the viscosity of the intestinal digesta may be detrimental to pig and production. Rice ap- pears to improve pig health with evidence of re- duced pig removal and antibiotic treatment. 9. Implications And Recommendations Reduced viscosity, diarrhea, and proliferation of pathogens by rice would be likely due to its low fiber content, high digestibility, and rice fac- tor. In practice, when availability and cost of rice permits, pork producers can benefit from inclu- sion of rice in diets for pigs immediately after weaning. References Bach Knudsen, K. E. (1997). Carbohydrates and lignin contents of plant materials used in animal feeding. An- imal Feed Science and Technology 67(4), 319-338. Bach Knudsen, K. E., Jensen, B. B., Andersen, J. O., & Hansen, I. (1991). Gastrointestinal implications in pigs of wheat and oat fractions. 2. Microbial activity in the gastrointestinal tract. British Journal of Nutrition 65(2), 233-248. Bach Knudsen, K. E., Hedemann, M. S., & Laerke, H. N. (2012). The role of carbohydrates in intestinal health of pigs. Animal Feed Science and Technology 173(1-2), 41-53. Bonet, J., Coma, M., Cortes, M., Medal, P., & Mateos, G. G. (2003). Rice vs. wheat feeding and protein level of the diet on performance of piglets from 10 to 16 kg BW. Journal of Animal Science 81, 47. Che, M. T., Perez, V. G., Song M., & Pettigrew, J. E. (2012). Effect of rice and other cereal grains on growth performance, pig removal, and antibiotic treatment of www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3) 20 Nong Lam University, Ho Chi Minh City weaned pigs under commercial conditions. Journal of Animal Science 90(13), 4916-4924. FAO (Food and Agriculture Organization of the United Nations). (2017). Rice market monitor. Food and Agri- culture Organization of the United Nations 20(3), 1-24. Francis, D. H. (2002). Enterotoxigenic Escherichia coli infections in pigs and its diagnosis. Journal of Swine Health and Production 10(4), 171-175. Gregorio, G. V., Gonzales, M. L. M., Dans, L. F., & Mar- tinez, E. G. (2016). Polymer-based oral rehydration solution for treating acute watery diarrhoea. Cochrane Database of Systematic Reviews 12, CD006519. Hampson, D. J., Robertson, I. D., La, T., Oxberry, S. L., & Pethick., D. W. (2000). Influences of diet and vaccination on colonisation of pigs by the intestinal spirochaete Brachyspira (Serpulina) pilosicoli. Veteri- nary Microbiology 73(1), 75-84. Hampson, D. J., Pluske, J. R., & Pethick, D. W. (2001). Dietary manipulation of enteric disease. Pig news and information 22, 21-28. Hopwood, D. E., D. W. Pethick, J. R. Pluske, & D. J. Hampson. (2004). Addition of pearl barley to a rice- based diet for newly weaned piglets increases the vis- cosity of the intestinal contents, reduces starch di- gestibility and exacerbates post-weaning colibacillosis. Br. J. Nutr. 92(3), 419-427. Iyngkaran, N., & Yadav, M. (1998). Rice starch oral rehy- dration therapy in neonates and young infants. Journal of Tropical Pediatrics 44(4), 199-203. Jensen, B. B., & Jorgensen, H. (1994). Effect of dietary fiber on microbial activity and microbial gas produc- tion in various regions of the gastrointestinal tract of pigs. Applied and Environmental Microbiology 60(6), 1897-1904. Keely, S. J., Montrose, M. H., & Barrett, K. E. (2009). Electrolyte secretion and absorption, small intestine and colon. In T. Yamada (ed.), Textbook of Gastroen- terology. New Jersey, USA: Blackwell Kim, J. C., Mullan, B. P., Hampson, D. J., Rijnen, M. M. J., & Pluske, J. R. (2007). The digestible energy and net energy content of two varieties of processed rice in pigs of different body weight. Animal Feed Science and Technology 134(3-4), 316-325. Li, D., Zhang, D. F., Piao, X. S., Han, I. K., Yang, C. J., Li, B., & Lee. J. H. (2002). Effects of replacing corn with Chinese brown rice on growth performance and apparent fecal digestibility of nutrients in weaning pigs. Asian-Australasian Journal of Animal Science 15(8), 1191-1197. Lindecrona, R. H., Jensen, T. K., & Moller, K. (2004). Influence of diet on the experimental infection of pigs with Brachyspira pilosicoli. Veterinary Record 154(9), 264-267. Macleod, R. J., Bennett, H. P., & Hamilton, J. R. (1995). Inhibition of intestinal secretion by rice. Lancet 346(8967), 90-92. Mateos, G. G., Martin, F., Latorre, M. A., Vicente, B., & Lazaro, R. (2006). Inclusion of oat hulls in diets for young pigs based on cooked maize or cooked rice. British Society of Animal Science 82(1), 57-63. Mathews, C. J., Macleod, R. J., Zheng, S. X., Hanrahan, J. W., Bennett, H. P., & Hamilton, J. R. (1999). Char- acterization of the inhibitory effect of boiled rice on intestinal chloride secretion in guinea pig crypt cells. Gastroenterology 116(6), 1342-1347. McDonald, D. E., Pethick, D. W., Mullan, B. P., & Hamp- son, D. J. (2001). Increasing viscosity of the intestinal contents alters small intestinal structure and intestinal growth and stimulates proliferation of enterotoxigenic Escherichia coli in newly-weaned pigs. British Journal of Nutrition 86(4), 487-498. McDonald, D. E., Pethick, D. W., Pluske, J. R., & Hamp- son, D. J. (1999). Adverse effects of soluble nonstarch polysaccharide (guar gum) on piglet growth and exper- imental colibacillosis immediately after weaning. Re- search in Veterinary Science 67(3), 245-250. Montagne, L., Cavaney, F. S., Hampson, D. J., Lalles, J. P., & Pluske, J. R. (2004). Effect of diet composition on postweaning colibacillosis in piglets. Journal of Animal Science 82(8), 2364-2374. Montagne, L., Pluske, J. R., & Hampson, D. J. (2003). A review of interactions between dietary fiber and the intestinal mucosa, and their consequences on digestive health in young monogastric animals. Animal Feed Sci- ence and Technology 108(1-4), 95-117. Piao, X. S., Li, D., Han, I. K., Chen, Y., Lee, J. H., Wang, D. Y., Li, J. B., & Zhang, D. F. (2002). Evaluation of Chinese brown rice as an alternative energy source in pig diets. Asian-Australasian Journal of Animal Sci- ence 15(1), 89-93. Pluske, J. R., Black, B., Pethick, D. W., Mullan, B. P., & Hampson, D. J. (2003). Effects of different sources and levels of dietary fiber in diets on performance, digesta characteristics and antibiotic treatment of pigs after weaning. Animal Feed Science and Technology 107(1- 4), 129-142. Pluske, J. R., Durmic, Z., Pethick, D. W., Mullan, B. P., & Hampson, D. J. (1998). Confirmation of the role of rapidly fermentable carbohydrates in the expression of swine dysentery in pigs after experimental infection. Journal of Nutrition 128(10), 1737-1744. Pluske, J. R., Montagne, F., Cavaney, S., Mullan, B. P., Pethick, D. W., & Hampson, D. J. (2007). Feeding different types of cooked white rice to piglets after weaning influences starch digestion, digesta and fer- mentation characteristics and the faecal shedding of β-haemolytic Escherichia coli. British Journal of Nu- trition 97, 298-306. Pluske, J. R., Siba, P. M., Pethick, D. W., Dur-mic, Z., Mullan, B. P., & Hampson, D. J. (1996). The inci- dence of swine dysentery in pigs can be reduced by feeding diets that limit the amount of fermentable sub- strate entering the large intestine. Journal of Nutrition 126(11), 2920-2933. The Journal of Agriculture and Development 17(3) www.jad.hcmuaf.edu.vn Nong Lam University, Ho Chi Minh City 21 Ramakrishna, B. S., Venkataraman, S., Srinivasan, P., Dash, P., Young, G. P., & Binder, H. J. (2000). Amy- lase resistant starch plus oral rehydration solution for cholera. The New England Journal of Medicine 342(5), 308-313. Siba, P. M., Pethick, D. W., & Hampson, D. J. (1996). Pigs experimentally infected with Serpulina hyo- dysenteriae can be protected from developing swine dysentery by feeding them a highly digestible diet. Epidemiology and Infection 116(2), 207-216. Stein, H. H., Lagos, L. V., & Casas, G. A. (2016). Nutri- tional value of feed ingredients of plant origin fed to pigs. Animal Feed Science and Technology 218, 33-69. Vicente, B., Valencia, D. G., Perez-Serrano, M., Lazaro, R., & Mateos, G. G. (2008). The effects of feeding rice in substitution of corn and the degree of starch gela- tinization of rice on the digestibility of dietary compo- nents and productive performance of young pigs. Jour- nal of Animal Science 86(1), 119-126. www.jad.hcmuaf.edu.vn The Journal of Agriculture and Development 17(3)