JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND 475 Maataloustieteellinen A ikakauskirja Vol. 63: 475—482, 1991 Effects of thermal processing on digestibility and protein utilization of rapeseed meal of medium and low glucosinolate type in diets for growing pigs MATTI NASI and HILKKA SILJANDER-RASI University of Helsinki, Department of Animal Husbandry SF-00710 Helsinki, Finland Abstract. The nutritive value of rapeseed meals (RSM) from Brassica campeslris, 0 and 00-cultivars, with medium (25—55 pg/g defatted meal) and low (<25 pg/g) level of glucosino- lates (GL), normal solvent extracted meal or thermal treated in order to decrease protein rumi- nal degradability (Opex-process) or followed also by treating for GL-reduction, was investigated in three digestibility and balance trials with growing pigs. The GL-reduction treatment used removed 0.68 of the original GL, while Opex treated RSM’s had 0.33 to 0.45 lower total GL- content than untreated RSM’s. The various cultivars or differently processed RSM’s were close to each other in their proximate composition. However, thermal treated 0-RSM had a slightly reduced lysine content compared to untreated meal. The efficient degradability of dry matter in the untreated RSM’s was on average 0.532 and that of the Opex-treated 0.485. The digesti- bility of CP in different RSM’s varied from 0.677 to 0.842 with no significant difference be- tween 0 and 00-RSM’s or to the RSM treated for GL-reduction (P>0.05), although 00-RSM’s tended to have higher OM and CP digestibilities compared with 0-RSM; pooled mean values being 0.638 vs. 0.715 for OM and 0.715 vs. 0.775 for CP. RSM treated for ruminant escape protein had the same or better digestibility than untreated RSM; pooled average values being 0.669 vs. 0.680 forOM and 0.746 vs. 0.757 for CP. This observation has practical importance since the same treatments of RSM could be employed for meals to be used in diets of both ruminants and pigs. In these experiments, the protein utilization was efficient and differences between the dietary treatments were small and insignificant. Heat treatment (Opex) did not decrease protein utilization despite a small reduction in lysine content. Index words; rape seed meal, glucosinolate, thermal processing, digestibility, pig Introduction value in Finland. The harvested seed is rich in oil and protein, the former being increas- ingly used for human consumption. Produc-Production of rapeseed is one of the most readily available means of increasing the tion of rapeseed oil for fuel purposes is also domestic supply of protein of high biological under evaluation, which means increased oilunder evaluation, which means increased oil https://www.c-info.fi/en/info/?token=BZ-XTZ-DJfq4_iRs.Sy_ah2ycmDVLfHx0qJDthw.TovuCx-EPlQe8ZC4jy6qwx1WpgnZHufh1jDYWjPnU7kHSHfVizyG5dqh4gSAuRyu6sV5X_gYMDj6J5Gvw3kkUXXHLXtR1EKqDNzx1ExX6520vXfybjoOCxhcJmIiRhdSSQIACCeciDIH9G95HKM3CS2tT0M3dhEKKMlnzN31mzF_R12jl1oEf9ocCCCaSY4iX9cm_qJwurzkrFDxDuA4rt_ULkqR45Zn08ykMjzs1AS3cP_3Qp4eDFXCwdk seed meal supply as a protein source for ani- ical or physical treatments alone, or in com- mal feeding. Removal of the oil leaves rape seed meal (RSM) containing 350—400 g/kg crude protein with an amino acid balance that compares well with that of soybean meal. Whilst RSM is currently included inruminant rations with promising response (Tuori et al. 1989, unpubl. Huhtanen et al. 1991), the use in pig and poultry rations has not been rea- lised because of the presence of a number of undesirable factors. However, many investi- gations have shown RSM as a potential re- placement for e.g. soybean meal (Kiiskinen 1984, NAsi et al. 1985). Rapeseed meal has some antinutritional fac- tors and toxic constituents which restrict the utilization of RSM as feed for pigs. The main factors responsible for lowering the nutritive value are the hulls with a high fibre content of therapeseed, the glucosinolates (GL), tan- nins, rapeseed gums, myrosinase and phytic acid (Fenwick and Curtis 1980, Bell 1984). The most important factor limiting the potential RSM as a protein supplement in pig feeding is the presence of glucosinolates (Rundgren 1983). These compounds are bro- ken down by the enzyme myrosinase into tox- ic, goitrogenic substances which cause meta- bolic disturbances and depress food intake and growth rate. Some of these are goitrogenic and others are potentially hepatotoxic, whilst the majority are volatile and have a strong bit- ter taste (Bell 1984). Plant breeding has managed to develop varieties with lower lev- els of GL. Meals prepared from rapeseed var- ieties with low or medium contents of GL are finding increasing acceptance as a protein source in pig diets and are being used as re- placements for soybean meal (SBM) (Thomke 1984, NAsi et al. 1985, Rowan and Lawrence 1986). An improvement in the nutritional quality of RSM would be expected from a reduction in the glucosinolate content. In addition, a va- riety of processes have been reported for the removal of glucosinolates from rapeseed products. Such processes, generally termed detoxification, involve chemical, microbiolog- bination (Fenwick et al. 1986). The fibre content of RSM is almost double that of SBM which lowers the nutrient digest- ibility and energy value. Rapeseed contain hulls 165—187 g/kg, on dry matter basis (Ap- pelqvist and Ohlson 1972). After oil extrac- tion, the resulting meal contains about 300 g/kg of hulls. Rapeseed hulls contain about 200 cellulose, 230 lignin, 90 pectin, 200 pro- tein and 50 ash g/kg, but very little free car- bohydrates or lipids. Pectins, cellulose and arabinose-based carbohydrates are dominant carbohydrates in hull-free RSM and these are not regarded as being readily digested by en- zymes secreted by the intestine of pig. Insolu- ble fibre tends to increase transit time and form an insulating coat on the digestible nutrients, thus reducing the nutrient supply. Soluble fibres slow down the transit time, but their gelling, ion-exchange and absorbing characteristics retard digestion and absorp- tion. The breeding work directed towards reduction of hull content may also make RSM more suitable for pig feed. Attempts to dehull rapeseed have been directed toward the same goal. Proper processing is of great importance to the nutritional value of rapeseed meals for pig diets, and heat treatment in oil extraction and meal toasting inactivates some antinutrition- al factors in RSM. Heat treatment and hydro- thermal processing can be used to rupture the cell wall matrix and modify the chemical struc- ture of the constituents in order to render them more susceptible to enzyme degradation in the small intestine, thus improving the di- gestibility and utilization of the nutrients, es- pecially amino acids (Nasi 1991). The first objective of the present study was to compare the nutrient digestibility of rapeseed meals with various levels of glucosinolates of different varieties before and after processing for GL-reduction. The second objective was to elucidate the effect of ther- mal processing used in order to decrease pro- tein ruminal degradation on the nutritive val- 476 ue of rapeseed meals as protein supplement in pig nutrition. Material and methods The rapeseed meals used in Expt. I, pre- pared from medium glucosinolate variety 0- type (Brassica campestris), were: 1.) normal solvent-extracted 0-RSM (cv. Emma), 2.) same as 1) but heat-treated (Opex), to yield a low-degradable rape seed protein for rumi- nants. The RSM’s, prepared from medium or low glucosinolate varieties, in Expt. 11. were: 1. normal solvent-extracted 0-RSM (Emma), 2. same as 1) but heat-treated (Opex) 3.) heat- treated (Opex), low rumen degradable 00- RSM (cv. Esko), 4.) normal solvent-extracted 00-RSM followed by a process of reduction of glucosinolates (Oljynpuristamo Oy, Hel- sinki) and in Expt. 11l 1.) normal solvent-ex- tracted 00-RSM (cv. Esko) and 2.) same RSM as 1.) but heat-treated (Opex), for low rumen degradable protein. Opex process (Oljynpuristamo Oy, Hel- sinki) is a pressurized heat-moisture treatment, where a sequence of cell rupturing pressure is added to achieve a rapid protein denaturation of the surface molecules. The process is a pro- grammed semi-batch treatment. It also elimi- nates a part of the antinutrional compounds in the meal as well as producing rumen low- degradable protein. Ferrous sulphate was used as a supplement at a level of 1.0 g/kg meal during toasting to reduce the GL content. In the first digestibility and balance trial, the normal and Opex processed 0-RSM’s were used at the inclusion level of 202—212 g/kg as protein supplements in isonitrogenous, 160 g/kg diet crude protein (CP) barley-based diets. In the second digestibility and balance trial, the variously processed 0- and 00-RSM’s were used at the inclusion level of 200 g/kg as protein supplements in four isonitrogenous, 152 g/kg CP, barley-based diets adjusted with barley protein. The third trial comprised as- says of normal and Opex 00-RSM’s at inclu- sion levels of 203 and 192g/kgproviding diets with 160 g/kg CP. The first experiment was made with six castrates from 89 to 109 kg of live weight with a switch over experimental design and a basal dietassay made separately. The second experi- ment, in which pigs were at the live weight from 28 to 74 kg, had a 6 x 6 Latin square design including a basal diet assay simultane- ously. The third trial was made with four pigs of weight between 66 and 89 kg using a swich over design. Each period comprised 6 days of adjustment and 6 days of total faeces and urine collection. The coefficients of the apparent digestibil- ity of the nutrients and the nitrogen balance were calculated for each diet and, using the difference method, for each RSM. Assay procedures were similar to those reported by Nasi (1984), but crude fat was determined after acid hydrolysis. The glucosinolate con- tent was analyzed withhigh-performance liq- uid chromatography which separates and quantifies individual components of GL. The degradability of the organic matter in the RSM’s was tested by the method of orskov and McDonald (1979). Results and discussion The total GL levels (pmol/g defatted meal) of the RSM’s made from cv. Emma, a medi- um GL 0-type, were between 16 and 55. The 00-RSM’s made from cv. Esko, a low GL 00-type contained from 7 to 22 pmol of total GL (Table 1). The individual components of GL in relation to others did not vary between varieties. The GL-reduction treatment was reduced to 0.32 of the original total GL- content compared to untreated. The GL-level of Opex-treated 0-RSM’s was 0.55 of the nor- mal untreated meals. Correspondingly Opex- treated 00-RSM’s had a level of 0.67 of the original. No difference in destroying various GL-components were found in present study, they decreased equally in relation to the total content. Lower responses have been reported by Aumaitre et al. (1989) who found micro- wave treatment decrease the total GL content in RSM by 0.07, while extrusion has removed 0.19 of these antinutritive factors, principal- 477 ly procoitrin (Aumaitre et al. 1989). Extru- sion has been shown to inactivate myrosinase efficiently but has had relatively little effect on glucosinolate content, unless chemicals were added before extrusion (Fenwick et al. 1986). They also found that the combihation of alkali and ferrous sulphate produces a de- crease in total GL-content to 0.80. This later figure is at the same level as shown in present trial using ferrous sulphate supplementation during toasting the meal. The chemical composition of the ex- perimental feeds and their calculated feed values are presented in Table 1. Only small differences were found in theproximate com- position of the processed RSM’s. Oil was left in meal in solvetizing 101—125 g/kg to in- crease the energy density of RSM. The differ- ent RSM’s were close to each other in their amino acid composition. However, the RSM treated for ruminants had a slightly lower ly- sine and available lysine content compared to the untreated normal meal. Excessive heat treatment during processing can lead to the de- struction of amino acids and the formation of biologically unavailable amino acid carbohy- drate complexes, which was noticed by Nasi et al (1985) and Nasi (1991). The mean effi- cient degradability of the dry matter in un- treated RSM’s was 0.532 (s.d. 0.0129) and somewhat lower in Opex-treated RSM’s, on average 0.485 (s.d. 0.0217). Tuori (1991, un- published) found similar degradabilities of the RSM’s with equal processing as in present study, but the process of RSM for lower ru- men degradability with the Opex-treatment did not show any response in milk production in that study. The digestibility of crude protein in the different RSM’s varied from 0.677 to 0.842 Table 1. Chemical composition and calculated values of the experimental feeds (Experiments 1, 2 and 3). Experiment Experiment 2 Experiment 3 Barley O—RSM O—RSM 00—RSM 00—RSM Norm Opex Norm Opex Opex Glucos. Norm Opex reduct. Total glucosinolates pmol/g defatted meal 55 25 28 16 13 7 22 16 Gluconapin 15 7 8 6 4 2 6.3 4.6 Glucobrassicanapin 14 7 8 4 3 1.5 4.1 2.8 Progoitrin 18 9 10 5 4 2 8.0 5.9 Napoleiferin 4 2 2 1 1 1.5 0.9 0.7 Others 0 0 0 0 1 1 3.0 1.8 Crude protein, g/kg DM 361 353 336 340 335 331 325 337 130 Ether extract » 100 118 107 101 106 119 125 107 37 Crude fibre » 130 130 124 125 121 123 125 123 47 Nitrogen free extract » 335 325 353 352 354 344 349 354 759 Neutr. deterg. fibre » 243 240 256 267 249 236 257 265 187 Acid deterg. fibre » 176 173 183 187 176 166 170 172 42 Acid deterg. lignin » 77 73 74 76 66 58 74 72 Lysine, g/160 g N 56 54 41 Threonine » 44 44 35 Methionine » 23 24 19 Cystine » 23 23 24 Available lysine » 53 50 40 FU/kg DM 0.84 0.86 0.73 0.71 0.89 0.90 0.95 0.98 1.14 Kg/FU 1.32 1.31 1.57 1.45 1.28 1.28 1.05 1.02 1.03 DCP, g/kg DM 265 235 234 230 250 234 262 284 68 ME, MJ/kg DM 12.7 13.0 12.3 12.0 13.5 13.0 13.78 14.31 14.71 Efficient degradability DM 0.549 0.514 0.523 0.462 0.477 0.523 0.534 0.488 478 (Tables 2—4). The 00-RSM’s tended to have higher organic matter and crude protein diges- tibilities compared to 0-RSM’s; pooled mean values being 0.638 vs. 0.715 for OM and 0.715 vs. 0.775 for CP, respectively. The treatment for GL-reduction did not have any response to protein digestibility. This is in agreement with the results of Sauer and Cichon (1980), who found no significant differences in the il- eal apparent digestibility of essential amino acids between a high and two low GL-RSM. The Opex-treated 00-RSM had significantly higher protein digestibility (P< 0.001) than other RSM’s in Expt. 2. RSM’s treated for ru- minant escape protein had the same or better digestibility than untreated RSM’s; pooled average values being 0.669 vs. 0.680 for OM and 0.746 vs. 0.757 for CP, respectively. This observation has practical importance since the same lots can be used for both ruminants and monogastrics. In Expt. 1 and 3. values of digestion were slightly higher which is to be expected because the pigs were older and made more efficient use of high fibre contents of RSM than younger pigs. Similarily, improve- ment of CP digestibility by 0.09 units and the ME content by 0.7 MJ per kg DM in sows was demonstrated when compared the results on growing pigs (Just et al. 1983). Carbohydrate digestibility of all the lots of RSM’s investigated was rather low. Howev- er, 00-RSM’s tended to show higher digesti- bility of organic matter, crude fibre and nitro- gen free extracts compared to 0-RSM’s, but the differences were not statistically signifi- cantly (P>0.05). Rundgren et al. (1985) also found lower carbohydrate and OM diges- tibilities for summer HG-RSM in comparison to LG-RSM. The dietary fibre in RSM represents the unavailable part of the diet, which reduces the digestibility of energy and amino acids. Degradation of the structural polysaccharides in rapeseed fibre and the cell wall matrix by physical or other means pro- motes the release of intracellular nutrients es- pecially that of protein in the small intestine for digestion and absorption (Nasi 1991). A small insignificant trend to improved NDF di- gestibility of RSM followed after Opex-pro- cess was noticed. The present digestibility data of various RSM tested in pigs are in agreement with the recent literature, which shows a superiority in the nutritive value low glucosinolate (LG)- compared with high glucosinolate (HG)-RSM (Bourdon and Aumaitre 1990). The average digestibility valueof CP ofLG-RSM has been 0.79 versus 0.73 for HG-RSM and cor- responding average values for content of ME for two RSM-types were calculated to be 13.1 Table 2. Digestibilities of processed rapeseed meals and protein utilization of the diets (Experiment 1). O—RSM SEM Statist. Normal Opex signif. Organic matter 0.645 0.656 0.0039 NS Crude protein 0.736 0.748 0.0059 NS Ether extract 0.623 0.597 0.0073 NS Crude fibre 0.321 0.362 0.0140 NS Nitrogen free extract 0.677 0.699 0.0091 NS Neutr. deterg. fibre 0.239 0.298 0.0165 NS Acid deterg. fibre 0.182 0.212 0.0118 NS N intake, g/d 72.2 71.8 0.30 NS N excr. in faeces, g/d 14.5 14.2 0.19 NS N excr. in urine, g/d 32.2 a 30.7 b 0.21 P<0.05 N retained, g/d 25.6 26.9 0.33 NS of intake 0.354 b 0.375 a 0.0036 P<0.05 of absorbed 0.444 b 0.467 a 0.0043 P<0.05 Urea excr. in urine, g/d 55 52 Biological value 0.529 0.550 0.0040 P<0.05 479 and 11.3 MJ per kg DM, respectively (Rund- gren 1983). Danish experiments performed according to the regression technique on three different baches of LG-RSM resulted in an es- timated average of the CP digestibility of 0.73 and of the ME value of 11.9 MJ per kg DM (Just et al. 1983). In these experiments, the differences in pro- tein utilization between the dietary treatments were very small. Results of protein utilization in Expt. 1. were poorer than in Expt. 2, but the protein intake was excess to the require- ments and pigs were also heavier in that trial. Damages in protein quality were not caused by the thermal treatment in the Opex process, according thepresent data. Usually heat treat- ed meals, processed for rumen escape protein, are lower in protein value for pigs compared to untreated (NAsi et al. 1985, Chang et al. 1987), probably due to exessive heat which Table 3. Digestibilities of processed rapeseed meals and protein utilization of the diets (Experiment 2). O—RSM 00—RSM SEM Statist. Normal Opex Opex Glucos. signif. reduct. Organic matter 0.630 0.619 0.703 0.660 0.031 NS Crude protein 0.696 b 0.677 b 0.746 a 0.706 b 0.007 P< 0.001 Ether extract 0.656 0.624 0.670 0.678 0.036 NS Crude fibre 0.336 0.332 0.497 0.389 0.061 NS Nitrogen free extract 0.649 0.650 0.730 0.692 0.053 NS Neutr. deterg. fibre 0.335 0.408 0.526 0.400 0.069 NS Hemicellulose 0.620 0.748 0.871 0.718 0.112 NS Cellulose 0.440 0.512 0.630 0.510 0.064 NS N intake, g/d 50.5 50.6 50.4 50.0 0.39 NS N excr. in faeces, g/d 13.6 14.1 12.8 13.2 0.35 NS N excr. in urine, g/d 13.8 14.1 14.0 14.1 0.59 NS N retained, g/d 23.1 22.4 23.6 22.7 0.68 NS of intake 0.458 0.444 0.474 0.453 0.014 NS of absorbed 0.634 0.620 0.637 0.621 0.017 NS Urea excr. in urine, g/d 27.4 28.8 30.1 24.8 1.40 NS Biological value 0.705 0.693 0.706 0.694 0.016 NS Table 4. Digestibilities of processed rapeseed meals and protein utilization of the diets (Experiment 3). 00—RSM SEM Statist. Normal Opex signif. Organic matter 0.729 0.769 0.055 NS Crude protein 0.807 0.842 0.025 NS Ether extract 0.604 0.645 0.053 NS Crude fibre 0.328 0.370 0.083 NS Nitrogen free extract 0.769 0.796 0.075 NS Crude carbohydrate 0.714 0.750 0.077 NS Neutr. deterg. fibre 0.278 0.381 0.1131 NS Acid deterg. fibre 0.103 0,185 0.0940 NS N intake, g/d 54.5 54.6 0.04 NS N excr. in faeces, g/d 11.8 11.1 0.05 NS N excr. in urine, g/d 21.0 21.3 0.78 NS N retained, g/d 21.7 22.2 0.43 NS of intake 0.400 0.410 0.0077 NS of absorbed 0.510 0.510 0.0122 NS Urea excr. in urine, g/d 29.6 39.7 3.96 NS Biological value 0.592 0.593 0.0122 NS 480 destroyes essential amino acids. An improve- ment in the nutritive quality of RSM would be expected from a reduction in their GL- content, but the treatment for GL-reduction in this study did not show in the protein utili- zation. The effect of extraction of RSM with hot 0.70 ethanoland with water has improved net protein utilization in rats significantly compared to untreated RSM (Fowler et al. 1987). Performance was also higher in pigs fed RSM washed with cold water extraction. Bille et al. (1983) concluded that only minor or no physiological effects in protein utiliza- tion in rats were observed at low levels of iso- lated glucosinolates similar to double low RSM, which is in line with the present obser- vations. In the present study, where fairly high rape seed meal supplements from cultivars of medi- um and low GL contents in barley meal diets were used in pig feeding, it can be concluded that RSM is a suitable protein source in sup- plementing grain protein. Double low cultivar tended to be slightly higher in nutritive value than 0-RSM. The thermal (Opex process) used to decreaseruminal degradation of RSM pro- tein and organic matter, did not decrease pro- tein utilization so that the same process could be used for RSM used in diets for ruminants and for pigs. From a practical point of view it is also important to retain as high a protein intestinal digestibility as possible, according to the results of the present assay. Processes directed to the decrease glucosinolate content of RSM, did not improve digestibility of nutrients nor protein utilization. References Appelqvist, L.A. & Ohlson, R. 1972. Rapeseed: Culti- vation, composition, processing and utilization. El- sevier Pub. Co. Amsterdam. Aumaitre, A., Bourdon, D., Peiniau, J. & Benoala Freire, J. 1989. Effect of graded levels of raw and processed rapeseeed on feed digesibility and nutrient utilization in young pigs. Anim. Feed Sci Technol. 24: 275—287. Bell, J.M. 1984. Nutrients and toxicants in rapeseed meal: A review J. Anim. Sci. 58: 996—1010. Bille, N., Eogum, 8., Jacobsen, 1., Olsen, O. & Soren- sen, H. 1983. Antinutritional and toxic effects in rats of individual glucosinolates added toa standard diet. I. Effects on protein utilization and organ weights. Z. Tierphysiol. Tierenahrg. u. Futtermittelkde. 49: 195—210. Bourdon, D. & Aumaitre, A. 1990, Low-glucosinolate rapeseeds and rapeseed meals: effect of technologi- cal treatments on chemical compaosition, digestible energy content and feeding value for growing pigs. Anim. Feed Sci. Technol. 30: 175—191. Chang, C.J., Tanskley, T.D. Jr., Knabe, D.A. & Zebrowska, T. 1987. Effects of different heat treat- ment during processing on nutrient digestibility of soy- bean meal in growing swine. J. Anim. Sci. 65: 1273 1282. Fenwick, G.R., Curtis, R.F, 1980. Rapeseed meal and its use in poultry diets. A review. Anim. Feed Sci. Technol. 5: 255—298. , Spinks, E.A., Wilkinson, A.P., Heaney, R.K. & Le- goy, M.A. 1986. Effect of processing on the an- tinutrient content of rapeseed. J. Sci. Food Agric. 37; 735—741. Fowler, V.R., Pusxtai, A., McWILLIAM, R. & Frank, R. 1987. The use of simple methods of extracting the antinutritive factors in rapeseed meal to improve the growth of pigs and rats. Anim. Prod. 44: 463. Just, A., Jorgensen, H., Fernandez, J.A., Bech-An- dersen, A. & Enoaard Hansen, N. 1983. Forskellige foderstoffers kemiske sammensaetning, fordoelighed, energi- og proteinvaerdi til svin. 556 Beretn. Stat. Husdyrbrugsf. 99 p. Huhtanen, P., Khalili, H. & Nasi, M. 1991. A compar- ison of untreated and formaldehyde-treated barley dis- tiller’s solubles and rapeseed meal as protein supple- ments in dairy cows given grass silage ad libitum. J. Agric. Sci. Finl. 63 (in press). Kiiskinen, T. 1984. Nutritive and feeding value of some domestic protein sources for poultry in Finland. Hel- sinki. 40 p. Nasi, M. 1984. Nutritive value and metabolic effects of whey protein concentrate and hydrolysed lactose for growing pigs. J. Agric. Sci. Finl, 56: 227—238. 1991. Digestibility and protein utilization responses of soybean and rape seed meal to physical and en- zymatic treatments in diets for growing pigs. J. Agric. Sci. Finl. 63: 465—474. —, Alaviuhkola, T. & Suomi, K. 1985. Rapeseed meal of low- and high- glucosinolate type fed to growing- finishing pigs. J. Agric. Sci. Finl. 57: 263—269. 481 Rowan, T.G. & Lawrence, T.L.J. 1986. Growth and metabolism studies in growing pigs given diets con- taining a low glucosinolate rapeseed meal. J.Agric. Sci., Camb. 107: 483—492. Rundgren, M. 1983, Low-glucosinolate rapeseed products for growing pigs a review. Anim. Feed Sci. Technol.: 239—263. —, Askbrant, S. & Thomke, S. 1975. Nutritional evalu- ation of low- and high-glucosinolate rapeseed meals with pigs, laying hens and rats. Swedish J. Agric. Res. 15: 61—69. Sauer, W.C., Cichon, R. & Misir, R. 1982. Amino acid availability and protein qualityof canola and rapeseed meal for pigs and rats. J. Anim. Sci. 54: 292—301. Thomke, S. 1984. Further experiments with RSM of Swedish low-glucosinolate type fed to growing-finish- ing pigs. Swed. J. Agric. Sci. 14: 151—157. orskov, E.R. & McDonald, I.M. 1979. The estimation of protein degradability in the rumen from incuba- tion measurements weightedaccording to rate of pas- sage. J. Agric. Sci. (Camb.) 92: 499. Ms received August 12, 1991 SELOSTUS Kuumennuskasittelyn vaikutus eri glukosinolaattipitoisten rypsirouhciden sulavuuteen ja valkuaisen hyvaksikayttoon lihasikojen ruokinnassa Matti Nasi ja Hilkka Siljander-Rasi Helsingin yliopisto, kolielaintieleen laitos Tutkimuksessa selvitettiin kuumennuskasittelyn ja glu- kosinolaattien vahentamisen vaikutusta 0- ja 00-rypsi- rouheiden sulavuuteen ja valkuaisen hyvaksikayttoon kas- vavilla lihasioilla. Tutkimus kasitti kolme sulavuus- ja ta- sekoetta, joissa kaytettiin kokonaiskeruumenetelmaa. Tutkittavina lajikkeina olivat 0-rypsi Emma ja 00-rypsi Esko, joissa glukosinolaattien kokonaismaara oli 16—55 ja 7—22 pmol/g rasvatonta rouhetta. Rouheet olivat nor- maalisti uuttamalla tuotettuja jakuumennuskasittelyna oli Opex-prosessi, jolla alennettiin rouheiden valkuaisen potsihajoavuutta. Glukosinolaattien vahentaminen teh- tiin kayttaen rautasulfaattikasittelya. Rouheet olivat ke- mialliselta koostumukseltaan lahella toisiaan. Opex- kasittely alensi hieman lysiinipitoisuutta kasittelematto- maan verrattuna. Rouheiden raakavalkuaisen sulavuus vaihteli 0.677 ja 0.842 valilla. 00-rouheet olivat sulavuu- deltaan hieman parempia kuin 0-rouheet: orgaaninen ai- ne keskimaarin 0.638 vs. 0.715 ja vastaavasti raakaval- kuainen 0.715 vs. 0.775. Glukosinolaattien poistaminen ei vaikuttanut sulavuusarvoihin. Opex-kasitellyt rouheet sulivat yhta hyvin tai hieman paremmin kuin kasittele- mattomat rouheet: orgaaninenaine keskimaarin 0.669 vs. 0.680 ja vastaavasti raakavalkuainen 0.746 vs. 0.757. Talla havainnolla on kaytannon merkitysta, koska samalla ta- valla kasiteltyja rouheita voidaan kayttaa rehuna seka ma- rehtijbille etta yksimahaisille. Valkuaisen hyvaksikaytbssa ei ollut eroja eri rouheiden tai erilaisten kasittelyiden va- lilla. 482