Effects of milk fat, unhydrogenated and partially hydrogenated vegetable oils on fat metabolism of growing pigs 1. Growth, feed utilization and carcass quality in pigs fed different fats and oils Kaija Suomi, Timo Alaviuhkola, JarmoValaja, Veikko Kankare and Asmo Kemppinen Suomi, K., Alaviuhkola. T., Valaja, J., Kankare. V. & Kemppinen,A. 1993. Effects of milk fat, unhydrogenated and partially hydrogenated vegetable oils on fat metabo- lism of growing pigs. I. Growth, feed utilization and carcass quality in pigs fed different fats and oils. Agric. Sci. Finl. 2: 7-13. (Agric. Res. Centre of Finland, Inst. Anim, Prod., Swine Res. Sta. FIN-05840 Hyvinkää, Finland, Agric. Res. Centre of Finland, Food Res. Inst. FIN-31600 Jokioinen, Finland and Dept. Food Tech./Dairy Section, Viikki, FIN-00014 University of Helsinki, Finland.) Two trials were conducted to study the effects of different dietary fats on the perform- ance, carcass quality and meat quality of 75 crossbred growing pigs. The experimental diets contained 14.3% butter oil (BO), low erucic acid rapeseed oil (RO), sunflower oil (SO) or partially hydrogenated sunflower oil (HSO). The cream (CR) content of the diets was 29.4%. The dietary fat addition comprised about 36% of the net energy content of the diets. The fatty acid composition of the dietary fats had a clear influence on the fatty acid composition of the adipose tissue of the pigs. Vegetable oils (RO and SO) increased the unsaturated fatty acid content of the adipose tissue and decreased the firmness of the backfat compared to the effects by milk fat (80, CR) (p<0,001). The correlation between linoleic acid content and firmness of back fat was significant (r=-0.83) (p<0.001). The trans fatty acid (Cl8:1) found in HSO seems to be incorporated intact into the fatty tissue of the pig to a large extent and a significant difference was found in the contents of trans fatty acid C18:1 between the SO and HSO treatments (p<0.001). Significant differences were found in feed conversion efficiency, kg DM/kg gain, (p<0.05) and in the firmness of back fat (p<0.001) between the present vegetable oils (RO, SO, HSO) and the milk fat (80, CR) dietary groups. Hydrogenated sunflower oil (HSO) increased the firmness of back fat compared to unhydrogenated sunflower oil (SO) (p<0.001), but in contrast, it significantly reduced daily gain and feed conversion efficiency (p<0.05). A vegetable oil addition of the level used in the present study is not recomended forpig diets because of the undesirable consistency ofback fat. Key words: pig, butter oil, rapeseed oil, sunflower oil, partially hydrogenated sunflower oil, cream, growth rate, feed conversion, meat quality Introduction they are not able to synthesize these fatty acids. The requirement of dietary linoleate for normal growth Dietary fatty acids are required only in the form of rate and feed efficiency is only 0.26% of ME ac- linoleic and linolenic acid by growing pigs because cording to Christensen (1985) and it can be met 7 Agric. Sei. Finl. 2 (1993) https://www.c-info.fi/en/info/?token=KGDpmAuZWrrRg85N.gVqR2nSeOnYOqKuCwwDegA.4FmHN75PRtsvlOvsEWVjVLBmfs3zAq1q0IyJEwXiFiWo3cy7Ka6a-uCNczdcgzwGy0ZquxP-_u3JWPaaVFdrBZ-62y7AeWtk9c6cB-GQmEzgDgdNsOUQmPYBCHnhXP2--crGI5mOTn2J6X_09xmWryJtdylXiD9ZSXW32pbCOxM9wKIB6jlKVF-sEo-Yq1FtoBsht1jGXdkrf4I1KRM1t8RV13SYs00hhWo6P2F-KIS_Hj3F_YD7eBUQVpc-Zzv7hAAv5gAYelOPFQhb_VUYqCxRdsNVB-AtUCZebF-c5dnHRJZr5Uvz-RINm3a9Yio2NiL5E2cRPSH4oyTj9nuoTrLseiw without the addition of dietary fat on a barley based diet because of the 2% fat content of barley, 60% is in the form of linoleic acid (Madsen 1983). Approximately 4kg fat (growth range from 20 to 90 kg) is supplied by feed on a barley based diet (Madsen et al. 1991). However, there is a remark- able synthesis of fat from other nutrients, mainly from carbohydrates, and therefore the carcass con- tains 3-4 times as much fat as that provided by conventional feed (Madsen 1983). The efficiency of the utilization of carbohydrates for fat retention is lower than the utilization of fat energy because dietary fat is preferentially utilized for body fat in the pig (Berschauer 1986). Therefore, dietary fatty acids are directly incorporated into the body fat, thus minimizing the heat losses associated with fat synthesis from acetyl CoA (BERSCHAUER 1986). The firmness and cohesiveness of carcass fats in the pig are affected by the fatty acid composition of dietary fat. An excess of vegetable fats containing high amounts of unsaturated fatty acids in swine diets causes the body fat to be undesirably soft and decreases the keepability of fat (PALMQUIST 1988). The inclusion of high levels of animal fat (technical pig fat) into the diets also increased the content of unsaturated fatty acids, especially oleic acid and linoleic acid in the body fat (Madsen 1983). Linoleic acid had a negative influence and stearic acid positively influenced the firmness of body fat (Madsen et al. 1991). The objectives of this part of the experiment were to study the effects of different dietary fats on the performance, carcass quality and fatty acid composition of the adipose tissue of growing pigs. The experiment was carried out in co-operation with the National Public Health Institute, the Agri- cultural Research Centre, the National Veterinary Institute, the University of Helsinki, the Depart- ment of Food Technology/Dairy Section, the Raisio Group and the Valio Finnish Co-operative Dairies’ Association. The results concerning the effects of dietary fats on the lipid and cholesterol values of porcine serum and lipoprotein fractions and the evaluation of the suitability of pig as a model for human nutritional studies are presented in Kemp- pinen et al. 1993. Material and methods A total of 75 growing pigs were used in two expe- riments. In January 1990 50 pigs were assigned to five different treatments with ten pigs per treatment (5 females and 5 castrates). Eighty percent of the animals were crossbred (Yorkshire x Landrace), the rest belonged to the Yorkshire breed. The second experiment was conducted in September 1990 with 25 growing pigs which were divided into five diffe- rent treatments. Half of the animals were crossbred (Yorkshire and Landrace) and half were York- shires. The treatments were similar to the first trial and contained five pigs in each (three females and two castrates). The pigs were divided into the treat- ments according to litter origin, initial live weight and sex in both trials. One pig was placed in each pen. The diet contained 14.3% (w/w) added fat of butter oil (BO), low erucic acid rapeseed oil (RO), sunflower oil (SO) or partially hydrogenated sun- floweroil (HSO). A 29.4% (w/w) addition ofcream (CR) was added into the diet. The rest of the diet consisted of a low-fat, high-fiber basal feed (Table 1). Approximately 36% ofthe net energy content of the diet originated from added fats and oils. The individually fed pigs received an equal amount of energy and protein daily in accordance with the Finnish energy and protein feeding recom- mendations (Salo et a 1.1982). The animals were housed on concrete flooring and fed twice daily. The pigs had free access to water. Daily rations of basal feed and fat were weighed into separate con- tainers and given in two portions at 7.00 am and 14.30 pm. Feed consumption was registered daily and weight gain fortnightly. The average initial weight of the pigs was 25kg and they were slaugh- tered after an experimental period of 88 days. Blood samples were collected from the vena jugularis at baseline, after 42 days and finally after 88 days for the analysis of lipid values, cholesterol values and lipoprotein fractions in porcine serum. The sample was taken after about an 18-h fast. Fatty acids were analyzed from the basal feed, dietary fats and from the adipose tissue of the pig by the method of the AOAC (1984). The tocopherol con- tent of the dietary fats was determinedwith a liquid 8 Agric. Sei. Fin!. 2 (1993) Table 1.Dietary ingredients (%) and chemical composition of the basal diet. Ingredients: Barley Soy bean meal Fat-free milk powder Barley hulls Mineral and vitamin mixture2 Calculated chemical composition: Feed unit (FU/kg) 1 Digestible crude protein, % Crude fibre, % Crude fat, % Lysine, g/kg Calcium, g/kg Phosphorus, g/kg Selenium, mg/kg Vitamin E, mg/kg 1. FU = 0.7 kg starch equivalent. 2. Composition of vitamin and mineral mixture: Ca, g/kg 200 P, " 75 NaCl, " 103 Vitamin A, 1000ky/kg 350 Vitamin D, " 57.257.2 Vitamin E, mg/kg 1200 Se, mg/kg 4 chromatograph by the method of Gertzand HERR- MANN (1982). The data were subjected to analysis of variance using the GLM procedure of SAS (1985). The model used to analyse the data was Yijkl +E;+Tj + Sk + TSij + eijkl where Yijkl = each individual observation, |i = over- all mean, Tj = effect of the treatment (i=l-5), Sk = effect of sex (j=l ,2), Ei = effect of experiment (k=l,2) and eijkl = residual term. The orthogonal contrasts used to compare diet- ary fats were 1. vegetable fat (the sum ofthe effects of RO, SO and HSO) vs milk fat (the sum of the effects ofBO and CR); 2. BO vs CR; 3. SO vs HSO; 4. RO vs SO. Results and discussion The fatty acid compositions of the basal feed and (%) 36.5 7.5 38.5 13.0 4.5 m: 0.95 19.8 5.1 0.99 14.7 14.7 9.0 0.27 62.5 the dietary fats are presented in Table 2. The basal feed containedpredominantly linoleic acid (Cl8:2) 52.9%, because of the high content of barley and soya bean meal in the feed. According to Madsen et al. (1991) the linoleic acid contents of barley fat and soya bean meal fat are 44 and 51%, respect- ively. Both RO and SO contained large amounts of unsaturated fatty acids and the most predominant fatty acid was oleic acid (Cl8:1) in RO (57.1 %) and linoleic acid in SO (61.8%) which is in agreement with the results of Madsen et al. (1990) and OSTERBALLE et al. (1990). Partial hydrogenation of sunflower oil increased the content of trans fatty acids (36.5%) compared to unhydrogenated sun- flower oil. The saturated fatty acid content was clearly higher for milk fat (BO and CR) compared to the vegetable oils and milk fat is constituted mainly of myristic (C14:0), palmitic (C16:0), stearic (18:0) and oleic acid. Vegetable oils (RO, SO, HSO) clearly contained more a-tocopherol compared to milk fat (80, CR) (Table 2). Dietary fat had a clear influence on the fatty acid composition of the adipose tissue (Table 3). The adipose tissue of the vegetable oil treatment groups (RO, SO, HSO) had a higher unsaturated/saturated fatty acids ratio (U/S) compared to the milk fat (BO and CR) treatment groups. The vegetable oils caused significantly softer adipose tissue compared to milk fat (p<0.001) (Table 4). In contrast to the other vegetable oils HSO had no negative effects on the firmness of the back fat. The reason for this was assumed to be the higher content oftrans fatty acids in the back fat. According to Madsen et a1.(1977) the hydrogenation of fat changed the backfat from very soft (9.9 points) to very hard (14.9 points) (14% hydrogenated fat/14% unhydrogenated fat). Several reports confirm that an increased amount of vegetable fat in diet has negative effect on the firmness of adipose tissue (Palmquist 1988, Scherf and Bieber-Wlaschny 1990, osterbal- le etal. 1990, Madsen et al. 1991). Sunflower oil caused the highest content of linoleic acid in the adipose tissue and had the most negative effect on the firmness of the backfat (Table 3). According to Berschauer (1984), the dietary intake of linoleicacid has the greatest influ- ence on the firmness of adipose tissue. Our study 200 9 Agric. Sei. Finl. 2 (1993) Table 2. Fatty acid composition and cx-tocopherol content of basal feed and dietary fats (% w/w) (BO = Butter oil, CR = Cream, RO = Rapeseed oil, SO = Sunflower oil, HSO = Partially hydrogenated sunflower oil). Feedstuff Basal feed BO CR RO SO HSO Fatty acid, % w/w C4:O 3.8 3.7 C6:O 2.5 2.7 C8:0 1.5 1.5 C 10:0 3.1 3.3 C 12:0 3.2 3.5 C14:0 0.2 10.7 11.8 0.1 0.1 C16:0 19.1 25.3 30.0 3.5 6.2 7.1 C 16:1 0.2 1.4 1.6 0.2 0.1 C18:0 1.5 12.9 11.1 1.5 4.3 19.7 C18:l cis 16.4 23.6 21.0 57.1 24.9 34.2 C 18:1 trans 2.6 1.6 36.0 ClB:2cis 52.9 2.1 1.8 23.0 61.8 1.0 C18:2 trans 0.3 0.3 0.5 C 18:3 7.0 0.6 0.4 11.0 1.5 0.1 Unsaturated fatty acids, % 77.4 32.8 29.0 94.2 88.3 72.1 Saturated fatty acids, % 22.6 67.2 71.0 5.8 11.7 27.9 U/S-ratio 1 3.4 0.5 0.4 16.2 7.5 2.6 rx-tocopherol mg/kg 30.5 9.8 4.5 145.0 412.5 352.5 1 The ratio of unsaturated to saturated fatty acids found a significant negative correlation between the linoleic acid content of adipose tissue and the firmness of the backfat (r=-0.83) (p<0.001). Ac- cording to Madsen et al. (1991) the content of the sunflower seeds in the diet of growing pigs should not exceed 4% because the higher amount causes undesirably soft backfat and decreases the consist- ency and keepability of the meat. The content of polyenoic fatty acids in the back- fat should not exceed 12-15% w/w for the produc- tionoffermented sausages and bacon (Houben and Krol 1984). In our study the polyenoic fatty acid content of adipose tissue exceeded the 15% level in the RO and SO pigs (25.4 and 45.0%, respectively) and was under the 15% level in the other treatment groups (80, HSO, CR) (7.3, 7.5 and 6.9%, respect- ively). Consequently, the quality of the fatty tissue of RO and SO pigs was unacceptable. The pooled performance results of the two trials are presented in Table 4. No differences were found in the daily gain of the pigs fed vegetable oil or milk fat in our study (Table 4). Mortensen et al. (1983) found no differences between a dietary fat addition of animal fat or vegetable oil/fatty acid mixture in the performance of pigs. Palmquist (1988) found no difference in the daily gain and feed:gain ratio of the pigs fed tallow, lard or vegetable oil. The long- chain saturated fatty acids (palmitic and stearic acid) present in milk and animal fat are less effi- ciently digested than the unsaturated fatty acids of vegetable oils (Berschauer 1986). According to Stahly (1984), the digestibility of fat from diets containing a ratio of unsaturated to saturated (U/S) fatty acids greater than 1.5 is relatively high, avera- ging 85-92%, and the digestibility of fat in diets with a U/S ratio ofless than 1.0-1.3 is substantially lower, ranging from 35% to 75%. In our study, the U/S ratio was clearly lower than 1.5 for milk fat (BO and CR) and higher than 1.5 for vegetable oils (RO, SO and HSO) (Table 2), respectively. There was a significant difference in feed:gain ratio between animals fed diets supplemented with animal or vegetable fats. This result supports the finding of Prabuck (1977) and Stahly (1984) 10 Agric. Sei. Finl. 2 (1993) Table 3. Fatty acid composition ofadipose tissue of the pigs (% w/w). LS-means of treatments are presented. (BO =Butter oil. CR =Cream, RO = Rapeseed oil, SO = Sunflower oil, HSO = Partially sunflower oil) BO CR RO SO HSO SEM 1 Statistical significance2Treatment Cl C 2 C 3 C4 Number of Animals Fatty acid, % w/w C 10:0 C 12:0 C14:0 C 16:0 C 16:1 C 18:0 C18:l cis C18:l trans C18;2 cis C18:2 trans C18:3 Unsaturated fatty acids, % Saturated fatty acids, % U/S-ratio3 II 11 II 11 0.20 0.20 0.06 0.06 0.46 0.48 0.09 0.08 4.46 4.85 1.02 0.97 24.98 26.12 12.38 13.22 3.67 4.07 1.01 0.91 11.45 10.90 6.32 7.31 41.99 41.21 48.51 28.65 1.05 0.96 0.83 0.76 5.97 5.65 18.71 43.33 0.31 0.31 0.01 0.00 0.93 0.92 6.93 1.44 55.89 55.05 79.05 77.49 44.11 44.95 20.95 22.51 1.3 1.2 3.7 3.5 11 0.05 0.009 *** NS NS NS 0.11 0.012 *** NS NS NS 1.25 0.083 *** ** * NS 14.33 0.266 *** ** * NS 1.81 0.084 *** ** *** NS 9.80 0.282 *** NS *** * 42.12 0.452 *** NS *** *** 18.89 0.249 *** NS *** NS 5 40 0 388 *** NS *** *** 1.23 0.012 *** NS *** NS 0.82 0.054 *** NS *** *** 73.12 0.454 *** NS *** * 26.88 0.453 *** NS *** * 2.7 1 SEM = standard error of means 2' Significance: NS(nonsignificant), * (P<0.05), ** (PcO.Ol), *** (PcO.OOl) Cl = Vegetable fat (RO, SO, HSO) vs. Milk fat (80, CR), C 2 = Butter oil vs. Cream, C 3 = Hydrogenated sunflower oil vs. Unhydrogenatedsunflower oil, C 4 = Rapeseed oil vs. Sunflower oil 3 The ratio of unsaturated tosaturated fatty acids Table 4. Performance and carcass quality of the pigs. LS-means of the treatments are presented. (BO = butter oil, CR = cream, RO = rapeseed oil, SO = sunflower oil, HSO =partially hydrogenated sunflower oil). Treatment BO CR RO SO HSO SEM 1 Statistical significance2 Cl C 2 C 3 C4 Number of Animals 15 15 14 15 Daily gain, g/day 754 796 795 818 Feed conversion rate, kg DM/kg gain 2.16 2.12 2.05 1.99 Loss at slaughter, % 24.0 22.9 24.0 23.2 Sidefat, mm 15.3 14.8 12.7 16.1 Firmness of fat score9-15 14.6 14.8 10.3 10.1 Meat in carcass, % 55.9 55.6 55.4 54.9 15 776 13.82 NS * * NS 2.12 0.04 * NS * NS 23.8 0.34 NS * NS NS 14.0 0.91 NS NS NS * 14.7 0.12 *** NS *** NS 55.6 0.77 NS NS NS NS 1 SEM = standard error of means 2 Significance: NS (nonsignificant), * (P<0.05), ** (PcO.Ol), *** (P<0.001) Cl = Vegetable fat (RO, SO, HSO) vs. Milk fat (80, CR), C 2 = Butter oil vs. Cream, C 3 = Hydrogenated sunflower oil vs unhydrogenated sunflower oil, C 4 = Rapeseed oil vs. sunflower oil 11 Agric. Sei. Fin!. 2 (1993) (ref. Berschauer 1986), who reported the ME- con- tent of vegetable oils to be 31.4 - 35.8kj/g and 27.6 - 35.6 kj/g in animal fats. In the comparison between the individual fats, pigs grew significantly better with CR than with BO (p<0.05) and with SO better than with HSO (p<0.05). HSO significantly impaired feed conver- sion efficiency (p<0.05). Hydrogenation impaired the digestibility of animal fat from 97 to 88% (Madsen et al. 1977). The same effect was also noticed with fish oil according to Opstvedt (1984). It can be concluded that the availability ofenergy from HSO compared to SO was lower. The pigs in HSO group grew slower and had lower carcass fat contents than the pigs in SO group. In conclusion, our results showed that the dietary fatty acids were directly incorporated into the adip- ose tissue. Both vegetable oils and milk fat seemed to be suitable for swine diets. However, vegetable oils increased the unsaturated fatty acid content of the fat and decreased the firmness of the backfat. Because of that, the vegetable oil addition of 14.3% (w/w) of the diet is not recommended for swine diets. It was also found that hydrogenation dec- reased the net energy value of sunflower oil. References AOAC 1984. Official methods of analysis. Ed. Association of Official Analytical Chemists, Virginia. Berschauer, F. 1984, Influence of fatty acid intake on the fatty acid composition of the backfat in pigs. In: Wood, J.D. (ed.). Fat quality in lean pigs. Brussels. Commision of the European Communities, p. 74-82. 1986. Fats in diets for growing pigs. Pig News and Information. 7,2: 153-158. Christensen, K. 1985. Bestemmelse af linolsyrebehov til slaktesvin. 577. Beretn. fra Statens Husdyrbrugsforspg, Kobenhavn. 158 p. Gertz, C, & Herrmann, K. 1982. Zur Analytik der Toco- pherole und Tocotrienole in Lebensmitteln. Z. Lebensm. Unters. Forsch. 174: 390-394. Houben, J.H. & Krol, B. 1984. Pig fats and the manufacture and storage of meat products. In: Wood, J.D. (ed.). Fat quality in lean pigs. Brussels. Commision of the Europe- an Communities, p.15-26. Kemppinen, A., Jauhiainen, M., Kankare, V., Valaja, J., Alaviuhkola,T., Aro, A. & Antila, P. 1993. Effects of milk fat, unhydrogenated and partially hydrogenated vegetable oils on fat metabolism of growing pigs. 11. Changes in serum lipoprotein and lipid levels. Agric. Sci. Finl. 2: 15-23. Madsen, A., Christensen, K., Christensen, K. D. & Mor- tensen, H. P. 1977. Dietary fats for growing pigs. Inter- national Symposium on Animal Fats in Pig Feeding. Dubrovnik. 86-100. 1983. Feeding effects on fat deposition and fat quality. CEC Workshop on Fat Quality in Lean Pigs. p. 1-6. —, Mortensen.H.P. & Jakobsen.K. 1991. Dietary Influence on Carcass Fat in Pigs. Proc. 42nd Annual Meeting of EAAP, Berlin. , OSTERBALLE, R., MoRTENSEN H.P., BeJERHOLM, C. & BAR- TON,P. 1990. Rävarekvalitet. Fodrets indflydelse pä räva- rekvaliteten hos slagtesvin 1. 673. Beretn. fra Statens Husdyrbrugsforspg, Foulum. 73 p. Mortensen, H. P., Madsen, A., Beierholm, C. & Barton, P. 1983. Fedt og fedtsyrer til slagtesvin. 540. Beretn. fra Statens Husdyrhrugsforsog, Kobenhavn. 48 p. Opstvedt, J. 1984. Fish fats. In. Wiseman, J. (ed.). Fats in Animal Nutrition. Butterworths, Boston p. 53-82. Palmquist, D. L. 1988. The Feeding Value of Fats. In: or- skov, E.R. (ed.). Feed Science. World Animal Science. B4p. 293-311. Prabuck, A. L. 1977. Fats and oils as feedstuffs. In: Kling, M. & Wöhlbier, W. (eds.). Handelsfuttermittel 1, Stutt- gart, Ulmerp. 565-579. (Ref. Berschauer, F. 1986). Salo,M.-L., Tuori.M. & Kiiskinen, T. 1982.Rehutaulukot ja ruokintanormit. 70 p. Helsinki. SAS 1985. SAS User’s Guide; Statistics. 5 th Ed. SAS Institute Inc., Cary, NC, USA. 956 p. Scherf, H. & Bieber-Wlaschny, M. 1990. How nutrition influences fat quality. Pig International, 2: 14, 16, 18,20. Stahly,T. S. 1984. Use of fat in diets for growing pigs. In: Wiseman, J. (ed.). Fats in Animal Nutrition. Butter- worths, Boston, p. 313-331. OSTERBALLE.R., Madsen, A., Mortensen.H. P. Bejerholm.C. & Barton, P. 1990. Rävarekvalitet. Fodrets indflydelse på rävarekvaliteten hos slagtesvin 2. 685. Beretn. fra Statens Husdyrbrugsforspg, Foulum. 58 p. Manuscript received June 1992 Kaija Suomi Timo Alaviuhkola Jarmo Valaja Agricultural Research Centre of Finland Swine Research Station Tervamäentie 179 FIN-05840 Hyvinkää, Finland Veikko Kankare Agricultural Research Centre ofFinland Food Research Institute FIN-31600 Jokioinen, Finland 12 Agric. Sei. Fin!. 2 (1993) Asmo Kemppinen Department of Food Technology/Dairy Section P. O. Box 27 (Viikki) FIN-00014 University of Helsinki, Finland SELOSTUS Ravintorasvat lihasikojen ruokinnassa Kaija Suomi, Timo Alaviuhkola, JarmoValaja, VeikkoKankare ja Asmo Kemppinen Maatalouden tutkimuskeskus ja Helsingin yliopisto Tutkimus kuului yhteistutkimukseen "Ravintorasvojen vaiku- tus sydän - ja verisuonitautienriskitekijöihin". Tämän osatut- kimuksen tarkoituksena oli selvittää erilaisten ravintorasvo- jen; voi -, rypsi -, auringonkukka - jakovetetun auringonkuk- kaöljyn sekä kerman vaikutus sikojen kasvuun, rehun hyväk- sikäyttöön, teuraslaatuun ja lihan laatuun. Veren kolesteroli- tutkimuksen tulokset julkaistaan toisaalla tässä lehdessä (Kemppinen et ai. 1993). Voi-, rypsi-, auringonkukka- ja kovetetun auringonkukka- öljyn osuus rehusta oli 14,3 %. Kerman määrä rehuseoksessa oli 29,4 %. Perusrehu, johon rasvat lisättiin, koostui vähäras- vaisista ja kuitupitoisista raaka-aineista. Rasvan lisäystaso vastasi noin 36 % rehun nettoenergiasta. Siat ruokittiin kaksi kertaa päivässä rajoitetuin normein (1,2-2,8 ry/el/pv). Ravintorasvojen rasvahappokoostumuksella oli selvä vai- kutus sikojen silavan rasvahappokoostumukseen. Kasviöljy- jen monityydyttymättömätrasvahapot, erityisesti linolihappo, varastoituivat suoraan silavaan ja heikensivät merkitsevästi silavan kiinteyttä. Kovetettu auringonkukkaöljy nosti transrasvahappojen pitoisuutta silavassa. Silavan linolihappo- pitoisuuden ja kiinteyden välillä oli voimakas negatiivinen korrelaatio (p<0.001). Kasviöljyjen ja maitorasvan välillä ei ollut muita eroja sikojen tuotantotuloksissa kuin maitorasvalla saatu hivenen heikompi rehun hyväksikäyttö. Öljyn kovettaminen heikensi sen energia-arvoa. Tulokset osoittivat, että kasviöljy ja voirasva soveltuvat lihasikojen rehuksi. Kokeessa käytetty kasviöljyn lisäystaso oli kuitenkin liian korkea, koska se heikensi selvästi silavan kiinteyttä. 13 Agric. Sei. Finl. 2 (1993)