Effect of barley grinding method and sodium polyacrylate supplement in the diet on the performance and stomach ulcer development of growing finishing pigs Timo Alaviuhkola, Marja Hautala, Kaija Suomi and Juhani Vuorenmaa Alaviuhkola, t., Hautala, M., Suomi, K. & Vuorenmaa, J. 1993. Effect of barley grinding method and sodium polyacrylate supplement in the diet on the perform- ance and stomach ulcer development of growing finishing pigs. Agric. Sci. Finl. 2: 481-487. (Agric. Res. Centre of Finland, Swine Res. Sta., FIN-05840 Hyvinkää, Fin- land, National Veterinary and Food Research Institute, Seinäjoki Regional Lab., FIN- -60101 Seinäjoki, Finland and Cultor Ltd., F1N00240 Helsinki, Finland.) Two different grinding methods - rolling and hammer milling - as well as polyacrylate supplement in the diet were studied to evaluate their effect on the performance of pigs and the incidence of gastric lesions. The experiment was carried out in 2 x 2 factorial arrangement with a total of 160pigs. The grist size ofrolled barley was bigger than of hammermilled barley, but the difference in water-binding capacity was insignificant. No significant differences were observed in the performance traits of pigs fed either rolled or hammer-milled barley. The sodium polyacrylate supplement had no effect on the daily gain, feed;gain ratio or carcass quality of the pigs. Gastric ulcers and constric- tions of the oesophageal opening of the stomach were more frequent in the groups fed hammer-milled barley than in the groups fed rolled barley, the difference being statistic- ally significant (P<0.00l). Sodium polyacrylate supplementation had no protecting effect against the incidence of gastric ulceration in growing finishing pigs. Key words: grinding, gastric ulcer, sodium polyacrylate, pig Introduction Ulcers, erosive lesions and scars are relatively com- mon findings in the stomachs of slaughtered pigs. Prevalence of gastric lesions in slaughter pigs has been reported to be 36% (Messing et al. 1992), 5-100% (O'Brien 1986) or 2-50% (Taylor 1986). Unthriftiness and even sudden death caused by a bleeding gastric ulcer is a well-known disease in sows but is also found in fattening pigs. Gastric ulcers or their preliminary changes are mostly lo- cated in the pars oesophagica of the stomach (Curtin et al. 1963, O’Brien 1968). This kerati- nized area of gastric mucous membrane is located around the opening of the oesophagus, and is ap- proximately 8 cm long and 10cm wide (Figs. 1 and 2.). There are no mucus secreting glands in this area. Thus it is quite liable to the acidity of gastric juices. The other part of the stomach (pars glandu- laris) secretes gastric juices and mucus, the latter being an important protector of the mucous mem- brane. In this area gastric lesions are relatively un- common in pigs. Gastric lesions are mostly limited to the mucosal surface of the stomach, and are not found to cause clinical symptoms or pain. Further, there is no evid- 481 Agric. Sei. Fin!. 2 (1993) https://www.c-info.fi/en/info/?token=wonQogBk6Pg2OHk4.nDEcG5IIg9IdmW3CLWXEPQ.m-6OWU27gr0uB07by9puih20eTJDwd6j0fLqgEm20t1FMuHzNV3iBmlrsNeXh93KpBMaxrCDARB6t0asbqxdLUCjrbLuktPEns6KV-YNPYZbMVqN5KfJSGobjYKZk_YCFCtF0nJCouSlLrlkuoSn38pU7S-OGtN0xlGpmghIxttWTmf11AvIMEWUTpaTIK7WQSG7NqybeJgNfQPk33WdSeE-noAwjhEhKHeoDkboBoaTNaIEd0Mb_gCEEXXWnuD7YWdBadKW-Dj9jklGHjIID_goBjT6OkH3mFvmaifVgzzNjPBGzXDuHbY1zH7pLNyMAUTeGeWD-Qo ence of their negative effect on daily weight gain (Ehrensberger et al. 1976, Blackshaw and Kelly 1980),but they can still develop into fatally bleeding gastric ulcers (Fig. 3). In good circum- stances, an ulcer can be healed by scarring. The process of scar-formation may constrict the open- ing of the oesophagus, which may lead to slower eating, regurgitation and decreased weight gain, or even death (Blackshaw and Kelly 1980, Nielsen 1990). First-grade gastric lesions are mild, superficial lesions. Second- and third-grade gastric lesions are the real ulcers, thus called severe lesions. The con- strictions of the oesophageal opening of the stom- ach are observed beside epithelial findings, and are always regarded as severe lesions (Hautala and Rautiainen 1991).A minor proportion of the mild preliminary changes can be observed only his- tologically by light microscope (Embaye et al. 1990, Hautala and Rautiainen 1991). Fig. 1.Normal oesophageal region (pars oesophagica) in the stomach of the pig. (Photo: M. Hautala) Fig. 2. Ist1 st grade lesion in the oesophageal region (pars oesophagica) of the stomach. (Photo: M. Hautala) Fig. 3. 3rd grade severe gastric lesion, a crater-like gastric ulcer in the oesophageal region of the stomach. An internal hemorrhage has caused sudden death. (Photo: M. Hautala) 482 Agric. Sei. Fin!. 2 (1993) Grist size has been reported to be one of the most important risk factors when reasons for gastric le- sions have been studied (Simonsson 1977). Ham- mer milling is the most common grinding method in the Finnish feed industry as well on the farms. It is well known that the smaller the particle size when grinding is done with a hammer mill the better the availability of cereal nutrients (Alaviuhkola 1971). No negative relationship between nutrient digestibility and ulceration in pigs was found when roller milling was used (Simonsson 1977). Proper milling and pelleting methods are import- ant in the prevention of gastric lesions. There are some reports about chemical feed supplements which may have beneficial effects. Tamas et al. (1983) succeeded in preventing oesogastric ulcers in pigs by using vitamin U (S-methyl-methionine sulfonium salt) in the diet. YAMAGUCHI et al. (1981) used sodium polyacrylate (SPA) 0.1 and 0.5% in the feed ofgrowing pigs and found that this supplementation not only decreased ulceration but also had a beneficial effect on pig performance. The purpose of the present experiment was to examine the effect of both the milling method and SPA supplementation on the performance of grow- ing finishing pigs and the development of gastric ulcers. Material and methods Animals and examination of stomachs A total of 160 piglets were divided into four groups in a 2 x 2 factorial experiment. The initial weight of the animals was around 25 kg. They were of Finn- ish Landrace and Large White origin and came from the sow unit of the Swine Research Station. The piglets were penned four animals in each pen, two females and two castrated males. Litter origin was also used as a balancing factor. The pens were furnished with concrete floor (170 x 150 cm) and dunging passage (170 x 100) with slats. There was 40 cm trough length for each pig. A small amount of wood shaving was used as the drying material. The animals were weighed fortnightly and sent to slaughter at a weight of 100 kg. At slaughter the stomachs of the pigs were col- lected individually. They were opened along the curvatura major of the stomach, emptied, rinsed and chilled close to O°C temperature. They were delivered for laboratory examination within 24 hours. Each stomach was categorizated according to the method of Hautala and Rautiainen (1991). Also stomachs with no visible pathological changes were examined histologically. Tissue samples from the margin ofpars oesophagica were fixed, dehydrated and embedded in paraffin. The tissue slices were stained withH & E (hematoxylin- eosin) and examined with 40x and IOOx magnifica- tions. Afterchilling the slaughter quality of all pigs was determined. Feeds and feeding Two grinding methods were used in the prepara- tion of the experimental feeds: hammer milling with a peripherally fed mill, 1500 rpm to pass a 3.5 mm sieve, and roll milling. The grist size of the two meals was measured with a test sieve shaker for 5 minutes. The water binding-capacity of both meals was measured by mixing 10 grams ofwater and two grams ofsample. The mixture was kept in room temperature for one hour. The free water was then separated in a centrifuge (5 min/ 3700 rpm). The water-binding capacity was calcu- lated as the amount of absorbed water (g)/sample weight (g). Two diets were prepared for the whole experi- mental period by mixing the barley (77%) with protein feeds (soybean meal 12%, meat and bone meal 3%), vitamins and minerals according to the Finnish recommendations (Salo et al. 1990). Half of both feeds was supplemented with 0.2% SPA. The arrangement of the experiment was as follows: 12 3 4group hammer-milled barley + + rolled barleyrolled barley - - + + Na-polyacrylate, 0.2% - + - + 483 Agric. Sei. Fin!. 2 (1993) 1 Finally the feeds were pelleted, and the content of crude protein and amino acids in the feeds was analyzed. The pigs were fed twice daily restrictedly. The same amount offeed was used in all treatments, and increased weekly from 1.2 kg/pig/day in the begin- ning up to the maximum (3 kg), which was reached in 10 weeks. Dry feed was moistened in the trough before feeding. Water was available all the time. The data were subjected to an analysis of vari- ance (Snedecor and Cochran 1967), using the following model: Yjjk = |i + ai +bj -t- (ab)ij + Cijk Y = each individual observation p = overall mean a = effect of grinding method (a = 1,2) b = effect of SPA supplement (b = 1,2) (ab)ij = grinding x SPA interaction eijk = residual term The result of a single pig was used as an observa- tion except in the calculation of feed:gain ratio, where theresult ofpen was used. The Kruskal-Wal- lis method was applied to test the frequency of gastric lesions in the stomachs. The relationship between the incidence of gastric lesions and daily weight gain of pigs was tested by the Spearman correlation test (Snedecor and Cochran 1967). Results and discussion Two pigs were lost from group 3. The reasons were inborn heart defect in the first case and umbilical hernia in the other. One pig was removed from group 4 due to slow growth. One stomach was lost in therinsing process at the slaughterhouse. The crude protein and amino acid content in the four mixtures was almost the same as expected. In the three samples taken from the barley meal, the water-binding capacity was higher in rolled than in hammer milled barley (2.2 vs 1.9). This indicates that the total surface area of the meal particles was probably bigger in rolled than in hammer milled barley. The grist spectrum of the two meals is shown in Table 1. Table 1. Particle size distribution of rolled and hammer-milled barley. Particle diameter, mm Rolled Hammer- barley milled barley 4.0 > % 2 0 2.5-4.0 % 21 0 1.6-2.5 % 35 2 1.0-1.6 % 26 22 0.3-1.0 % 14 66 <0.3 % 2 10 There were no differences in the performance between pigs fed hammer milled or rolled barley. This agrees with theresults reported by Simonsson (1977). It may be concluded that grist size is not the best indicator of the nutrient availability of ground meal. The total surface area of the particles seems to be more important. Digestibility trials done by NÄSI (1992) with barley handled with same grind- ing methods as in the present experiment, showed the same digestibility for crude protein and nitro- gen-free extract. No significant differences in the carcass quality of pigs between the treatments were found. The performance and carcass quality of the pigs is shown in Table 2. SPA supplementation had no effect either on the daily gain or the feed:gain ratio of the pigs. Neither was there any grinding method x SPA interaction. In their studies on the mode of action of SPA, Kokue et al. (1983) and YAMAGUCHI et al. (1981) found that SPA had an antipeptic activity and caused a reduction of the free-acid content of gas- tric juice in rat trials. In pigs, a prolonged retention of the diet in the stomach was noticed. In the pres- ent experiment, SPA was not observed to have any effect on the performance of pigs. The observed gastric lesions are presented in Table 3. The expression "severe lesions" denotes the sum of second and third grade lesions and the oesophageal constrictions. All the lesions, except one, were located in the pars oesophagica. In the stomach ofone pig fed hammer-milled barley with- out SPA supplement, the second-grade ulcer was found in pars glandularis. All the first-grade lesions 484 Agric. Sei. Fint. 2(1993) Table 2. Effect of two different grinding methods and sodium polyacrylate (SPA) supplement on daily gain, feed consump- tion and carcass quality of growing pings. Group 1 2 3 RM 4 RM Significance Milling SPA MillingMilling" HM HM SPA. 0.2% Number of pigs •SPA+ + 40 40 40 40 mean s mean s mean s mean s Initial weight kg 25.2 1.19 25.2 1.23 Final weight ” 101.0 3.70 101.6 3.09 25.2 1.23 25.1 1.01 NS NS NS 100.9 3.08 101.7 2.79 NS NS NS101.0 3.70 101.6 3.09 (corr. to 25% loss) Days in trial 85.7 6.95 86.0 6.76 84.6 6.61 85.4 7.71 NS NS NS 899 64.30 903 65.27 NS NS NSDaily gain, g 889 66.53 893 58.65 Feed: gain ratio 2.28 0.09 2.29 0.07 2.26 0.06 2.29 0.07 NS NS NS Side fat, mm 16.9 4.51 17.5 4.95 37.7 2.76 38.2 3.89 18.0 3.99 17.8 4.76 NS NS NS 37.9 2.55 37.9 4.19 NS NS NSLean colour2 ' degr. Per cent lean + bone in carcass 54.0 2.52 53.9 2.27 53.9 1.49 53.5 2.68 NS NS NS " HM = hammer-milled, RM = roller-milled 21 EEL smoke reflectometer Table 3. Effect of grinding method and sodium polyacrylate (SPA) supplement on the incidence of gastric lesions in pigs. Number Grades of gastric lesion Number of stomachs Severe" lesions, tot. of pigs with constriction of 0 12 3 oesophageal opening Hammer-milled 80 1 66 13 0 5 15 % 1.25 82.50 16.25 0 6.25 18.75 Rolled 76 29 47 0 0 1 1 % 38.16 61.84 0 0 1.25 1.25 SPA - 78 17 54 7 0 3 8 % 21.79 69.23 8.97 0 3.85 10.26 SPA 0,2% 78 13 59 6 0 3 8 % 16.67 75.64 7.69 0 3.85 10.26 " Sum of 2nd and 3rd grade ulcers and constrictions. in stomachs of pigs fed hammer-milled barley could be observed macroscopically. Of the 47 first- grade lesions found in the stomachs of pigs fed rolled barley, 25 were detectable only microscopic- ally. Second-grade gastric lesions were found only in pigs fed hammer-milled barley. No third-grade ulcers were observed in this material. The number of severe gastric lesions was higher in the stomachs of pigs fed hammer-milled barley than those fed rolled barley. The difference was statistically significant (P<0.001). On the other hand, SPA supplement in the feed seemed to have no effect on the incidence ofgastric lesions. The result is in accordance with the findings reported by SIMONSSON (1977) and Mahan et al. (1966), who also compared different grinding methods. However, there is a contradiction be- tween this result and the results of Yamaguchj et 485 Agric. Sei. Fin!. 2 (1993) ai. (1981), which may be partly explained by differ- ences in further processing (pelleting) of the experi- mental feeds. The incidence of severe gastric lesions did not seem to affect the daily gain of pigs (r = 0.02). Earlier reports (Blackshaw and Kelly 1980, Nielsen 1990) have come to the same conclusion. However, the frequency of severe gastric lesions in pigs fed hammer milled barley was 16% in present experiment. The question may be raised whether it is acceptable from the ethicalpoint of view that pigs have pathological, maybe painful lesions, even though they do not affect performance. 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Pig Diseases. The Burlington Press (Cambridge) Ldt, Foxton. p. 256-261. Yamaguchi, M., Takemoto, T., Sakamoto, K., Asano, T., Uchimura, M. & Masuda, I. 1981. Prevention of gastric ulcers in swine by feeding of sodium polyacrylate. Am. J. Vet. Res. 42; 960-962. Manuscript received April 1993 Timo Alaviuhkola Kaija Suomi AgriculturalResearch Centre of Finland Swine Research Station FIN-05840 Hyvinkää, Finland Marja Hautala National Veterinary and Food Research Institute Seinäjoki Regional Laboratory Box 198 FIN-60101 Seinäjoki, Finland Juhani Vuorenmaa Cultor Ltd. Kyllikinportti 2 FIN-00240 Helsinki, Finland 486 Agric. Sei. Finl. 2(1993) SELOSTUS Viljan jauhatustavan ja natriumpolyakrylaattilisäyksen vaikutus lihasikojen kasvuun, rehun hyväksikäyttöön ja mahahaavauman esiintymiseen Timo Alaviuhkola, Marja Hautala, Kaija Suomi ja JuhaniVuorenmaa Maatalouden tutkimuskeskus, Eläinlääkintä-ja Elintarvikelaitos ja Cultor Oy Ohran jauhamistavan ja natriumpolyakrylaattilisäyksen (0,2 %) vaikutuksia lihasikojen kasvuun, rehun hyväksikäyt- töön sekä mahahaavauman esiintymiseen tutkittiin ruokinta- kokeessa 160 sialla. Koerehut sisälsivät ainoana rehuviljana ohraa 77 %. Osa ohrasta jauhettiin vasaramyllyllä, osa valssi- myllyllä. Vasaramyllyllä jauhetun viljan hiukkaskoko oli pie- nempi kuin valssatun ohran. Siitä huolimatta jälkimmäisen vedensidontakyky oli suurempi johtuen luultavasti partikkeli- en suuremmasta kokonaispinta-alasta. Jauhatusmenetelmällä ei ollut vaikutusta sikojen kasvuun, rehun hyväksikäyttöön eikä teuraslaatuun. Vasaramyllyllä jauhettua viljaa syöneiden sikojen mahalaukkujen esophagus- osassa todettiin selvästi enemmän mahahaavauman esiaste- muutoksia sekä vakavia mahahaavaumia kuin valssimyllyllä jauhetulla viljalla ruokittujen sikojen mahalaukuissa. Natriumpolyakrylaattilisäykselläei ollutvaikutusta sikojen tuotantotuloksiin. Se ei myöskään kyennyt ehkäisemään ma- hahaavauman esiasteiden syntymistä. 487 Agric. Sei. Fin!. 2 (1993)