JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND 245 Maataloustieteellinen Aikakauskirja Vol. 57: 245—253, 1985 Replacing protein supplements in barley-based diets for growing pigs with free lysine and methionine MATTI NÄSI University of Helsinki, Department of Animal Husbandry, SF-00710 HELSINKI, Finland Abstract. Protein metabolism and utilization, and performance were examined in pigs kept on diets with two protein levels, 15 and 17 % crude protein (cp), and supplementation with free L-lysine and DL-methionine. In the 5 x 5 Latin square balance trial, 15 and 17 % cp diets were fed with and without supplementation with 2 g lysine/kg feed and one 15 cp diet with both lysine and 0.7 g methionine. The diets had 120 and 136 g DCP/FU, lysine 7.8, 9.4 and 11.0 g/kg and sulphur amino acids 4.4, 5.0 and 5.1 g/kg. Nitrogen retention was 13 % higher on the 17 % cp diet than on the 15 % cp diet (P > 0.05). The lysine supplementation improved N retention by 4.3 % on the 15 % cp diet and supplementation with the two amino acids improved it by 2.5 % (P > 0.05 %). Urinary urea excretion on the 17 % cp diet was 17—12 % higher than on unsupplemented 15 % cp diet, and on the diets with amino acid sup- plementation it was 7—B % lower (P < 0.05) than on the diets without. In the first feeding trial with 500 pigs, the higher-protein diet gave 7.4 % better daily gains. The diet with 15 °/o cp supplemented with lysine gave only 2.3 % better gains than the basal 15 % cp diet. The difference in feed conversion efficiency (FCE) between protein levels was statistically significant (P < 0.05). The second feeding trial was a comparison of 17 % and 15 % cp diets in which the lysine and sulphur amino acid levels hqd been equalized by supple- menting the 15 % cp diet with lysine and methionine. The pigs were fed on a grower diet with 18 % cp to 50 kg live weight and afterwards the experimental diets were fed separately to the gilts and castrates. The pigs grew similarly on the two diets, 783 vs. 780 g daily. The FCE was better on the lower-protein diet and lower in the gilts then the castrates. The gilts gave better carcase quality than the castrates and the lower-protein diet tended to give better carcase quality. The rather poor response to supplemental free amino acids in the present study seems to indicate limitation of inadequate supply of other amino acid. Index words: Protein nutrition, synthetic amino acids, pig feeding, nitrogen balance Introduction sources to increase the total protein content and to counteract any essential amino acid deficiency. In experiments (Alaviuhkola 1981), in which the crude protein level is raised Pig formulas are normally based on grain and the diets are supplemented with protein https://www.c-info.fi/en/info/?token=x_sE3Jvm5rpgvS4m.Sq9CBjBLeJv8xQ9nCO0X_A.wJy3f5G68LhQGNEjK9-Co-hZG7nMsaarOH1nhsRWpAlrwoVcKV0zDH2Uv-IljMW88o0dLLTtu5cYrtlCzBYms3Sdd5oTefGuCltt1CqI0TtfEscJD-RDCWmftbRHGdEl-kwtCB58yHXCP6FRP0IT4eZQcTtArKNvh9H4wow progressively and the protein comes from con- ventional sources, it is likely that the response to protein which is measured is really a re- sponse to lysine. This is commonly the most limiting amino acid for pigs on a barley-based diet (Fuller et al. 1979). When the diet is supplemented with protein concentrate, with the aim of reaching levels of lysine and threonine optimal for protein synthesis, the amounts of other amino acids may become ex- cessive (Taylor et al. 1979). The digestible crude protein which the pig cannot utilize for protein deposition is mainly transformed into urea and excreted in the urine, raising energy costs and reducing protein efficiency (Fuller et al. 1979). The restrictions now placed on the import of feed protein into Finland and the desir- ability of developing domestic protein sources have increased interest in formulation of ani- mal diets on an amino acid basis, using syn- thetic amino acids to ensure efficient protein utilisation. The growth rate, feed conversion efficiency and leanness of Finnish pigs have been improved considerably. Whether the pro- tein and lysine requirements have been altered by the increased potential for protein deposi- tion now requires to be investigated. The objective of the present study was to examine the protein utilization the daily gain and carcase quality of growing pigs when part of theirprotein supplements was replaced with synthetic lysine and methionine. Materials and methods The experimental diets were barley-based and supplemented with soybean meal and fish meal (4 + 1) to give crude protein levels of 15 and 17 ®/o. Synthetic L-lysine HCI alone or lysine and DL-methionine together were added to some diets, to give the same amino acid levels as were supplied by the protein supplements in others. One of the 17 % cp diets was had a higher level of lysine. The composition of the diets used in the balance trial and an analysis of their ingredients are shown in Table 1. The data on the complete feeds used in the feeding trials are shown in Table 2. The nitrogen balance trial was carried out with six castrated Landrace xLarge White pigs weighing 38—80 kg, the design being a 5 x 5 Latin square. One pig was kept on a protein- free diet, based on barley starch (84.5 %) and supplemented with barley straw (10 %), but- ter (2.5 %) and a mineral mixture (3 °7o), to measure metabolic faecal nitrogen and urinary endogenous nitrogen. The experimental ani- mals were housed individually in metabolic cages, which allowed separate quantitative collection of urine and faeces. These were col- lected twice daily and representative samples were frozen and stored until analysis. The pigs were fed twice daily according to a standard scale based on the live weight (Salo et ai. 1982). The diet was mixed with water (1 + 2 w/v) and water was given after feeding. The feed spillage was collected and substracted from the ration. The daily rations in the dif- ferent periods were 1.6—2.8 kg. The pigs were weighed before and after each period. The details of the procedure are the same as de- scribed by Nasi (1984). The two growth trials were performed on a commercial pig farm (T. Ahonranta, Loi- maa) wtih 500 pigs in each experiment. The pigs were assigned at random to the different feeds, the variations in starting weight between the groups being kept as small as possible. Twelve pigs were placed in each pen, there were ten replicates of each of the four treat- ments and the animals were fed on the same diet throughout the experimental period. In the second trial rearing methods were com- pared and the gilts and castrates were kept either in separate pens or together. In this trial all the pigs were fed the same grower diet, 18 % cp, to 50 kg live weight, after which they received one of the two experimental diets. In the second trial the number of replicates was 6—7 per treatment. In the trials the pigs were fed according to a restricted feeding regimen and feeding was the same for the two sexes (Salo et ai. 1982). 246 Table 1. Composition and analyses of the diets and ingredients used in the balance trial. Diets 1 2 3 4 5 Ingredients Barley 86.5 81.5 86.3 81.3 86.2 Soybean meal 10.5 14.5 10.5 14.5 10.5 Fish meal 3.0 4.5 3.0 4.5 3.0 L-lysine HCI 0.2 0.2 0.2 DL-methionine 0.07 Calculated composition Crude protein, % in feed 15 17 15 17 15 Lysine, g/kg feed 8.1 9.7 9.7 11.3 9.7 Methionine + cystine 5.9 8.6 5.9 6.6 6.6 Sulphur amino acids/lysine 0.72 0.67 0.60 0.58 0.67 Barley Soybean meal Fish meal Dry matter, % 88.4 88.0 93.3 Ash, % 2.9 8.3 11.2 Crude protein, % 10.1 51.7 72.6 True protein, % 8.6 48.3 52.4 Ether extract, % 2.4 3.2 13.8 Crude fibre, % 5.2 5.3 0.8 NFE, % 79.4 31.6 1.6 Amino acids, g/kg feed Alanine 4.1 17.4 39.3 Arginine 6.7 40.1 36.1 Aspartic acid 4.9 34.4 62.2 Cystine 1.2 4.8 4.3 Glutamic acid 23.9 88.6 103.3 Glycine 4.9 21.5 45.0 Histidine 3.6 16.2 25.1 Isoleucine 3.8 20.4 30.0 Leucine 6.9 31.6 49.1 Lysine 3.9 30.1 42.7 Methionine 1.7 5.5 21.6 Phenylalanine 5.2 22.9 26.4 Serine 3.8 17.5 25.7 Threonine 3.7 20.0 32.3 Tyrosine 3.2 15.4 19.4 Valine 5.1 22.2 35.0 The chemical analyses of the feeds and faeces were performed according to the offi- cial procedures and the other analyses were the same as described by Nasi (1984). The data were treated by the analysis of variance and the differences between the treatment means were tested by the Tukey test (Steel and Tor- rie 1960). In the second growth trial, covari- ance was applied to eliminate the effect of the difference in starting weights between treat- ments. Results and discussion The experimental diets used in thebalance trial had slightly lower protein contents, 14.5 and 16.9 %, than estimated (15.0 and 17.0%), because the barley proved to have a rather low crude protein (CP) content (10.1 % of DM). The digestible crude protein contents of the diets were calculated to be 120 and 136 g/feed unit (FU), and thus the diet with the lower cp value did not satisfy the protein requirements 247 248 Table 2. Composition and analyses of the experimental diets used in the feeding trials. Trial 1 Trial 2 Treatments Treatments 12 3 4 5 6 Ingredients, % Barley 78.5 78.5 82.0 82.0 57.7 61.7 Oats 20.0 20.0 Soybean meal 13.0 13.0 11.0 11.0 12.8 10.5 Fish meal 5.0 5.0 3.0 3.0 5.0 3.0 Feed fat 1.0 1.0 Limestone flour 1.5 1.5 1.5 1.5 1.3 1.3 Dicalcium phosphate 1.0 1.0 1.5 1.5 1.2 1.3 Min. vit. mix. 0.8 1.0 0.8 1.0 1.0 1.0 L-lysine-HCI 0.2 0.2 0.151 DL-methionine 0.07 Calculated nutrients Crude protein, % 17.0 17.0 15.0 15.0 17.0 15.0 DCP, % of feed 13.5 13.5 12.0 12.0 13.5 12.0 Kg feed/FU 1.03 1.03 1.03 1.03 1.02 1.02 Lysine, % 1.05 0.90 0.90 0.75 0.93 0.93 Methionine + cystine 0.50 0.50 0.42 0.42 0.53 0.53 Analysed composition, in DM Dry matter, % 87.4 87.6 87.6 87.6 88.7 88.7 Ash, % 6.0 5.9 6.1 6.3 6.1 5.8 Crude protein, % 19.2 18.8 16.9 16.7 19.0 17.1 Ether extract, % 3.1 3.0 2.7 2.6 4.6 4.3 Crude fibre, % 5.1 5.8 5.4 4.8 5.1 5.4 NFE, % 67.2 67.0 69.6 69.9 65,2 67.4 Amino acids, g/kg feed Alanine 7.2 7.0 6.1 6.2 8.2 7.2 Arginine 8,5 8.2 7.1 7.3 10.8 10.4 Aspartic acid 15,8 15.8 13.4 13.4 14.5 13.5 Cystine 3,6 3.4 3.5 3.6 3.3 3.1 Glutamic acid 30.4 28.3 28.0 28.5 30.4 29.0 Glycine 7.5 7.1 6.4 6.3 8.0 7.1 Histidine 3.5 3.5 3.0 3.0 3.8 3.6 Isoleucine 5.4 5.4 4.7 4.7 6.7 6.0 Leucine 10.8 10.8 9.5 9.8 12.3 11.4 Lysine 10.5 9.0 8.9 7.7 8.7 8.8 Methionine 2.1 2.2 1.7 1.9 1.5 2.6 Phenylalanine 6.8 7.0 5.9 6.2 7.9 7.2 Proline 11.3 11.6 10.9 11.8 11.6 11.1 Serine 8.1 7.9 7.1 7.2 8.2 7.3 Threonine 6.7 6.6 5.7 5.8 6.6 5.8 Tyrosine 3.7 3.4 3.0 3.0 5,5 5.1 Valine 6.7 6.9 6.1 6.2 8.6 7.6 of growing lean-type pigs on a restricted feeding regimen. The amino acid contents of the diets were calculated to be also a little lower than intended, 0.78, 0.94 and 1.10 % for lysine (LYS) (0.81,0.97 and 1.13 %)and 0.44, 0.50 and 0.51 % for methionine and cystine (0.59 and 0.66 %). The low values for sulphuric amino acids (SAA) may partly be an analytical error, because these are easily destroyed when the samples are prepared. The threonine contents were 0.63 and 0.74 % (Table 1). The amino acid requirements pre- sented for growing pigs are 0.85—0.9 % for lysine, 0.55—0.6 % for SAA and 0.5 % for threonine (Salo et ai. 1982). The fish meal in the present study had a low lysine content, 6.3 Table 3. Nitrogen balance and protein utilisation in pigs on diets with different protein contents and supplemented with synthetic amino acids. Treatments 1 2 3 4 5 Protein content, % 15 17 15 17 15 Lysine supplement/kg 2g 2g 2g Methionine supplement/kg 0.7 g Nitrogen intake, g/d 53.6C 61.CP 54.2C 61.90 54.3C N excreted in faeces, g/d 11.4* 12.7b 11.2* 12.0*b 11.5ab N absorbed, g/d 42.2' 48.3d 43.fr 49.9 d 42.8' Apparent N digestibility, % 78.5 79.0 78.9 80.6 78.9 N excreted in urine, g/d 21.2" 24.6ab 21.1* 25.9 b 21.4“ N retained, g/d 21.fr 23.7ab 21.9ab 24.0 b 21.5* b % of intake 39.9 39.6 41.9 39.9 41.0 % of absorption 51.0 50.1 53.4 49.8 52.2 g/kgWO75 1.02* 1.15*b 1.09ab 1.17b 1.06“b Urea excreted, g/d 39.8ab 47.5* b 38.3a 50.5b 37.9* g/kgWO7S 1.82ab 2.13ab 1.67* 2.27b 1.70“ Creatinine excreted, g/d 2.5 2.6 2.5 2.6 2.3 Biological value 58.8 57.0 61.0 56.6 59.8 Daily gain, g/d 788 929 800 901 892 Means with different letters were significantly different (a, b, Pc0.05; c, d, P<0.01). g/16 g N. In the growing pig diets, the analy- sis values were close to the estimated values (Table 2), except that the crude protein con- tents were a little low and the SAA contents of the diets in growth trial 1 were a little higher than estimated. The crude protein intake on the 17 % cp diet was significantly higher (P < 0.01) than on the 15 % cp diet (Table 3). The apparent digestibilities of nitrogen were slightly higher on the diet with a higher protein content (P > 0.05), which indicates that the protein supplements were more digestible than barley protein. N excretion in the urine was higher on the diets containing more protein (P < 0.05), which indicates that the protein supply was excessive or the amino acids not properly balanced. N retention was 13 % better in pigs on the 17 % cp diet than on the 15 % cp diet (23.7 vs. 21.0 g N/d). Lysine supplementation of 2 g/kg feed on the 15 % cp diet improved nitrogen retention by 4.3 °7o (P > 0.05). When Low and Pittman (1979) supplemented a control diet containing 7 g/kg feed with 1 g/kg L-lysine, nitrogen retention increased from 20.3 to 23.1 g/d. In the present study the comparatively low response to sup- plemental lysine indicated that an essential amino acid or possibly the supply of non- essential amino acids was limiting for protein synthesis. Supplementation of the diet with both lysine and methionine, however, in- creased nitrogen retention by only 2.5 % of the level on the basal diet. Supplementation with methionine improved nitrogen retention only slightly, but the diets proved to be defi- cient in this respect. Increased response of SAA in growing pig diets up to 0.60 % in feed have been found when one third originated from synthetic methionine (Berende and Bertram 1983). The only statistically signifi- cant difference in the nitrogen balance was found between the 15 % cp diet and the 17 % diet supplemented with LYS (P > 0.05). The nitrogen retention calculated as g/kg W 0 accorded with the daily nitrogen retention values (Table 3). For the pig on the protein- free diet the measured faecal metabolic nitro- gen excretion was 1.43 g N/kg DM intake and the urinary endogenic N excretion was 0.099 249 Table 4. Performance of growing pigs on diets with different protein content and supplementedwith L-lysine HCI in trial 1. Diet no. 12 3 4 Protein % 17 17 15 15 Lysine suppl. 2 g 2 g No. of pigs at start 126 125 126 126 No. of pigs at end 124 125 126 124 Mortality, % 1.6 0 0 1.6 Initial weight, kg 23.6 24.2 23.8 24.0 Final weight, kg 101.7 103.7 101.2 99.6 Carcase weight, kg 74.4 74.7 73.8 73.0 Slaughter loss, % 26.8 28.0 27.1 26.8 Days in experiment 114.8 114.7 116.2 116.1 Daily gain, g 680 699 666 651 FCE kg/kg gain 2.98' 3.12“ 3.17d Feed kg/d 2.02» 2.09b 2.08 b 2.06» b Carcase grading, E+,% 14.5 18.4 11.9 8.9 E 30.7 24.8 23.0 19.4 I 41.9 48.8 53.2 58.9 I— 10.5 7.2 11.9 8.9 Withdrawal 2.4 0.8 0 4.0 Means with different letters were statistically significant (a, b P<0.05, c, d, P<0,0l). g N/kg W O7S . The values found here are in accordance with those reviewed by Carr et al. (1977). Urinary urea excretion on the 17 % cp diets was 17—12 % higher than on the unsupple- mented 15 % cp diet and on the diets with amino acid supplementation it was 7 —B % lower (P < 0.05) than on the diets without. The urea excreted in the urine of the pig on the protein-free diet was only 0.9 g/d. The quantity of urinary urea, which is the major metabolite of nitrogen excretion in the pig, is greatly influenced by the protein quality and the amino acid balance (Brown and Cline 1974). Lysine supplementation improved the biological value of the diet protein by 2.2 % units and the lysine + methionine supple- ments given together improved it by 1.0 %- units. Fuller et al. (1979) have shown that supplementation of barley with lysine and threonine increased the biological value of barley protein from 51 to 86, and histidine supplementation further increased the biologi- cal value to 93. The daily gains on the diets with a lower protein content were ca. 100 g lower, than on the 17 cp diets, except in the case of the 15 % cp diet supplemented with both the synthetic amino acids, which gave the same daily gain as the diets with 17 % cp. The response of pigs to supplementation of low protein diets with essential amino acids can depend on several factors (Low 1980). Addi- tions of single amino acids should evoke a positive response only if the amino acid is first limiting (Fuller et al. 1979). Here supple- mentation of a deficient protein supply with synthetic amino acids gave poorer results than expected from the amino acid figures of the supplemented diets, which indicated some es- sential amino acid deficiency or that the pro- tein supply was inadequate, since the pigs at the higher protein level performed better. Uti- lization of the high levels of synthetic amino acids may have been impaired by unequal rates of absorption of protein derived and synthetic amino acids, as suggested by Bat terham (1984). However, Partridge et al. (1985) did not find any differences in N use when pigs were fed twice a day or more fre- quently with diets supplemented with free lysine. Table 4 shows the performance of the pigs 250 Table 5. Performance of growing pigs on diets with different protein content supplemented with L-lysine HCI and DL-methionine when the sexes were reared together and separately in trial 2. Treatments Diet 5 (17 % CP) Diet 6 (15 % CP + Significance Rearing Lys.Met.) of difference Gilts + Gilts Castra- Gilts + Gilts Castra- Diets Groups Castrat tes Castrat tes No. of pigs at start 84 84 84 96 72 84 No. of pigs at end 83 84 83 96 70 84 Mortality, % 1.2 0 1.2 0 2.8 0 Initial weight, kg 48.4 53.6 53.3 53.1 54.3 53.4 Final weight, kg 102.0 106.8 107.2 107.4 107.0 106.7 Carcase weight, kg 73.8 77.9 77.2 76.3 78.2 76.7 Slaughter loss, % 27.2 27.1 28.0 29.0 26.9 28.1 Days in experiment 73.0 65.1 67.5 68.9 66.5 66.6 Daily gain, g 755 811 784 777 767 796 NS NS FCE kg/kg gain 3.36 3.06 3.27 3.21 3.07 3.19 NS P 0.05). The lower-protein diet was rather defi- cient as a feed for the total growing period, 25—100 kg of live weight, and lysine supple- mentation alone could not improve the per- formance. There was a statistically significant difference in feed conversion efficiency (P < 0.01) between the diets with different protein levels. The difference caused by lysine sup- plementation was quite small. Throughout the experiment, the feed intake was unusually low, averaging 2.02—2.09 kg/d, and the pigs receiving the diet with 17 % cp supplemented with lysine consumed significantly less than the other groups (P < 0.05). The carcase quality of the pigs on the higher protein diets tended to be slightly better, grades E + and E were more frequent in these groups. Table 5 presents data on the performance of the pigs in trial 2, in which a 17 % cp diet was compared with a 15 % cp diet supple- mented with synthetic amino acids to the same lysine and methionine + cystine level as the higher-protein diet. The pigs were kept on the same grower diet to 50 kg live weight and then swiched to one of the two experimental diets. The pigs in group 1 had a lower initial weight and the results were calculated by the covari- ance method, taking into account the longer growth time. The pigs grew similarly on the two diets, 783 vs. 780 g daily gain (P > 0.05). On the higher protein diet the gilts performed better, but the results were the opposite on the lower-protein amino acid-supplemented diet (P > 0.05). Feed consumption was less on the lower-protein diet (P < 0.05) and less in the gilts (P < 0.01). Feed conversion efficiency was better on the lower-protein diet (P < 0.05) than on the 17 cp diet (3.16 vs. 3.23 kg/kg gain) and lower in the gilts (P < 0.01) than in the castrates. The gilts gave better car- case quality (P > 0.05) than the castrates and the lower-protein amino acid-fortified diet tended to give better carcase quality also. It can be concluded that supplementation 251 of a low-protein diet for growing pigs with synthetic amino acids improved performance and dietary protein use. In the present study improvement on the free amino acid-supple- mented diet was less, than could be expected from the amino acid supply. In these experi- mental diets in adequate amounts of other amino acids may have limited the utilization of synthetic amino acids as a protein substi- tute. Acknowledgements. This study was made possible by the support of the Finnish Sugar Co, Thanks are due to Mr. Ari Kettunen for technical assistance and toMr. Tuo- mo Ahoranta for providing the necessary facilities and arranging the care of the experimental animals. References Alaviuhkola, T. 1981. Energia- ja valkuaisnormikokei- ta lihasioilla vuosina 1975 —1980. Maatalouden tutki- muskeskus. Sikatalouskoeaseman tiedote 2. Batterham, E.S. 1984. Utilization of free lysine by pigs. Pig News Inform. 5: 85—88. Berende, P.L.M. & Bertam, H.L. 1983. Sulpur amino acid requirement of young pigs. Z. Tierphysiol., Tierer- nährg. u. Futtermittelkde. 50: 93—100. Brown, J.A. & Cline, T.R, 1974. Urea excretion in the pig: An indicator of protein quality and amino acid re- quirements. J Nutr. 104: 542—. Carr, J.R., Boorman, K.N. & Cole, D.J.A. 1977. Ni- trogenretention in the pig. Br. J. Nutr. 37: 143—155. Fuller, M.F., Livingstone, R.M., Baird, B.A. & Atkin- son, T. 1979. The optimal amino acid supplementation of barley for the growing pig. 1. Response of nitrogen metabolism to progressive supplementation. Br. J. Nutr.; 321—331. Low, A.G. 1980. Amino acid use by growing pigs. Re- cent advances in animal nutrition. Ed. W. Haresign and D. Lewis. Butterworths. p. 141—156. & Pittman, R.J. 1979. Responses of growing pigs to practical diet supplemented with amino acids. Anim. Prod. 28: 435—436. Näsi, M. 1984. Nutritive value and metabolic effects of whey protein concentrate and hydrolysed lactose for growing pigs. J. Agric. Sci. Finl. 56: 227—238. Partridge, 1.G., Low, A.G. & Keal, H.D. 1985. A note on the effect of feeding frequence of nitrogen use in growing boars given diets with varying levels of free lysine. Anim. Prod. 40: 375—377. Salo, M.-L., Tuori, M. & Kiiskinen, T. 1982. Rehutau- lukot jaruokintanormit, Helsinki. 70 p. Steel, R.G. & Torrie, J.H. 1960. Principles and proce- dures of statistics. New York. 481 p. Taylor, A.J., Cole, D.J.A. & Lewis, D. 1979. Amino acid requirement of growing pigs. 1. Effects of reducing protein level in diets containing high levels of lysine. Anim. Prod. 29: 327—338. Ms received September 30, 1985 SELOSTUS Rehuvalkuaisen korvaaminen synteettisillä aminohapoilla kasvavan lihasian ruokinnassa Matti Näsi Helsingin yliopisto, Kotieläinlieleen laitos, 00710 Helsinki Sulavuus- ja tasekokeessa sekä kahdessa kasvatusko- keessa selvitettiin kahden valkuaistason (17 ja 15 % rv) ja synteettisen lysiini- ja metioniinilisäyksen vaikutusta valkuaisen hyväksikäyttöön ja tuotantotuloksiin liha- sikojen ruokinnassa. Eri dieettien ravintoaineiden sula- vuudet olivat samanlaisia. Typpitase oli sioilla, jotkasai- vat 17 % rv dieetissä 13 % korkeampi kuin 15 % rv- dieetillä (23.7 vs. 21.0g/d), Lysiinilisäys 0.2 % dieetissä lisäsi typen pidättymistä 4.3 °/o ja lysiini ja metioniini täy- dennettyinä samaan tasoon 17 °/o rv sisältävän dieetin kanssa lisäsi 2.5 % N-tasetta. Korkeammalla valkuaista- solla deaminaatio oli voimakkaampaa ja aminohappoli- 252 säys vähensi urean erittymistä virtsassa 7 —B %. Kasva- tuskokeessa 17 % rv-dieetillä sikojen lisäkasvu oli 7.4 % parempi kuin 15 % rv saaneilla ja 0.2 %;n lysiinilisäys paransi kasvua 2.4 %. Toisessa kasvatuskokeessa ami- nohappotasapainotetulla 15 %: n seoksella saatiin sama kasvutulos kuin 17 % rv sisältävällä seoksella, kun koe- seoksia käytettiin 50 kg:n elopainosta teurastukseen. Rehuseos, jossa oli 17 % rv (13.6 % srv), täytti siko- jen valkuaisentarpeen koko kasvatuskauden ajan, joskin deaminaatio oli suurta. 15 °/o:n (12.0 % srv) valkuaistaso oli riittämätön joidenkin aminohappojen osalta vaikka lysiiniä ja metioniiniä oli lisätty normien mukaisesti. Syn- teettisten aminohappojen täydennyksillä saatiin pienem- piä vaikutuksia valkuaisen hyväksikäytössä ja kasvutu- loksissa kuin dieettien pitoisuuksista olisi voinut olettaa. 253