Protein utilization responses of growing pigs to supplemental lysine as liquid versus crystalline form in barley-barley protein diet MattiNäsi Näsi, M . 1992. Protein utilization responses of growing pigs to supplemental lysine as liquid versus crystalline form in barley-barley protein diet. Agric. Sci. Finl. 1: 215-223. (Univ. Helsinki, Dept. Anim. Sei., SF-00710 Helsinki, Finland.) The study examined the influence of increasing dietary supplements of liquid com- pared to crystalline lysine on nitrogen (N) balance and protein utilization in growing pigs (30-100 kg LW) in a B*B Latin square. Eight isonitrogenous diets with 160 g CP/kg were formulated from barley and barley protein supplemented with the two lysine sources at levels of none, I, 2 and 3 g/kg to provide 5.5, 6.5, 7.5 and 8.5 g/kg total dietary lysine. Barley-SBM served as a contol diet. The dietary lysine concen- tration had substantial effect on N retention and metabolism. The lysine supplements to the cereal-based diet with a low lysine content, 5.5 g/kg, significantly improved N- retention, decreased urinary-N excretion and enhanced protein utilization and daily gain. There was a linear response of N-retention, urinary-N and urea-N excretion and apparent biological value (P<0.001) to lysine supplementation level. As the lysine con- centration was gradually increased, the efficiency of N retention in relation to N intake and absorbed N increased linearily. No difference was found in N balance parameters between the two lysine sources, liquid vs. crystalline form being equal in their response. Pigs fed the SBM-diet compared to the barley protein diet fortified with lysine did not differ in response of N retention and protein utilization, but SBM lead to lower urinary-N excretion. N retention, urinary-N excretion and biological value as parameters for protein utilization showed lower variability (CV 0.08-0.10) compared to urinary urea-N excretion (CV 0.20). Regression coefficients of responses of protein utilization to liquid lysine were overall lower than those to crystalline lysine. Key words: lysine, pure amino acid, protein, nitrogen balance, pig Introduction A feed protein seldom contains an amino acid com- position which is similar to the requirements of the growing pig. Lysine is generally considered as the first limiting amino acid in conventional cereal based diets for pig (Fuller et al. 1979, Näsi 1989). The cereal based pig diets are supplemented with protein sources to increase the total protein content and to counteract any essential amino acid defi- ciency. When the diets are supplemented with pro- tein concentrate, with the aim of reaching levels of lysine optimal for protein synthesis, the amounts of other amino acids may become excessive. Amino acids surplus to the pig's requirement are cataboliz- ed causing nitrogen (N) and urea losses in urine. Increasing amounts of digestible crude protein (CP) in the diet enhance the energy loss in the 215 Agric. Sei. Finl. 1 (1992) https://www.c-info.fi/en/info/?token=AiivjdBrx4teD2up._KNQxwQvhVIFAja8jr1-NQ.TeKePqPG8GrBn4tbuMqYQl5ashe_pTb_1LtxhDTNNCQhy9yPcyVEhkrrYM_PCVVoR-XJOnckbUOD7OnhIniF-onlo0bSufScsmndQ9DuKquXCnwoFPQrbwFgri0HVZCPpOcvxMLapZBpIQ_JULNKG0xp0lwGx56CebVMjtho5lLsn0sd-D8rV5jEhWpqG2yRrcZtO3tFmOhVZESA2g7-ItpIBXqhkeanwBVx2yarjRLRkfkvZPsse__S71dLb88gH_AkXibw urine, decrease metabolizable energy (ME) in rela- tion to digestible energy and also decrease the effi- ciency of utilization of ME. Thus the catabolism of excess protein reduces net energy available for pig growth (Just 1982). An ideal protein for pig growth can be described as one which supplies the optimum balance of essential amino acids together with sufficient N for the synthesis ofnon-essential amino acids. Proteins of high nutritional value for pig tend to resemble the lean tissue in their amino acid composition and are close to the dietary amino acid pattern which leads to the highest utilization of the dietary protein (ARC 1981,Wang and Fuller 1989).L-lysine and DL-methionine are two amino acids which are commonly used in pig diets to replace or supple- ment natural intact protein sources of lysine and methionine. The purpose of using synthetic amino acids in the pig diets is to reduce CP levels and cut the cost of the diets without deteriorating pig per- formances. Cereal protein after starch and ethanol process (Näsi 1988) has a low quality of protein (Linko et al. 1989) considering the degree to which the com- position of the absorbed amino acids is in accord- ance with the balance that is required by the pig (Näsi 1989). The amino acid composition of barley protein can be improved as a protein souce for pig feeding by fortification with pure lysine (Näsi 1989). Barley feed fractions to the pig farms are delivered commonly in a liquid form, which re- duces the feed cost due to dehydration and elimina- tes deterioration of the protein quality in drying process. Lysine supplementation to wet barley pro- tein could be employed as liquid form, which would reduce the production costs of the lysine process and would avoid to a greater extent the environmental problems of waste waters in crystal- lizationand purification of crystalline lysine. The present paper reports an experiment which was conducted to determine the efficiency of the liquid lysine product compared to crystalline form in protein utilization of growing pigs as affected by the dietary lysine concentration in a barley-barley protein lysine deficient diet. Material and methods Eight dietary treatments were used in comparisons of the lysine forms and levels of supply as outlined in Table 1. The diets were formulated isonitrogen- ous to supply 160 g CP per kg barley meal based feed mixture. Protein supplementation was made with barley protein derived from integrated starch- ethanol production (Alko Ltd. Koskenkorva) according to the process described by Näsi (1988). As the (positive) control diet served barley supple- mented with soybean meal to yield equal protein supply. The chemical composition of the feed in- gredients are presented in Table 2. Lysine supple- mentation of the diets (1, 2, and 3 gpure lysine/ kg feed mixture) was made using a liquid product form in fermentation by Brevibacterium flavum, strain V-5, emloying the technology developed at the August Kirchenstein Institute of Microbiology of the Latvian Academy of Sciences, Riga (Beker et al. 1971). The culture liquid was sterilized and dehydrated in a vacuum-vapour evaporator up to a DM content of 400 g/kg. This product was stabi- lized by adding hydrochloric acid to pH 5.1. The crystalline lysine was a commercial product, L- lysine monohydrochloride (Eurolysine). The experiment was designed as a 8 x 8 balanced Latin square with growing pigs of castrated males (Landrace x Large White) with initial weight of 30.4 (SE 0.39) kg and final weight of 101.3 (SE 0.41) kg. The pigs were kept during the whole experiment in metal metabolism cages equipped with collection trays allowing separate collection of faeces and urine. Each period comprised 5 days of adjustment and 5 days of total collection of faeces and urine. The pigs were fed twice daily according to a restricted feeding regime and their diets were adequately fortified with minerals and vitamins (Salo et al. 1982). The average daily DM intake was kept at 93 g/kg W° 75 . The details of the procedure are the same as described by Näsi (1984). Amino acids in liquid lysine and barley protein were determined by high-performance liquid chromatography. All animals completed the experiment successfully and the average daily 216 Agric. Sei. Finl. 1 (1992) Table I . The outline of the experimental design and diet composition. DIET No 12345678 Barley, g/kg 867 786 786 786 786 786 786 786 Protein supplement Soybean meal, g/kg 133 - - - - - - - Barley protein, g/kg - 214 214 214 214 214 214 214 Total protein supply, g/kg 160 160 160 160 160 160 160 160 Lysine supplement Liquid lysine, g/kg - - 1.0 2.0 3.0 ... Crystalline lysine, g/kg - - - - 1.0 2.0 3.0 Total lysine supply, g/kg 7.4 5.5 6.5 7.5 8.5 6.5 7.5 8.5 Table 2. The chemical composition of the experimental feeds. Feedstuff Barley Barley Soybean Liquid Crystalline Composition protein meal lysine lysine Dry matter, g/kg 883 915 877 401 993 Ash,g/kgDM 28 31 69 146 1 Crude protein" 133 352 488 604 822 Ether extract" 35 60 38 1 Crude fibre" 51 20 70 Total sugars " 79 Amino acids g/ 160 g N g/kg g/kg Lysine 30 67.9 800 Threonine 29 0.1 Methionine+cystine 31 Histidine 20 0.5 Leucine 65 0.3 Isoleucine 55 0.3 Phenylalanine 56 Arginine 43 0.2 weight gain during the entire experiment was 814 g. Pig response to graded levels of the supplemental lysine of two sources was assessed in terms of N balance, urinary-N and urea excretion, biological value and daily gain. The results were analysed by analysis of variance for Latin Square experiments and linear and quadratic functions were fitted to describe the response of lysine supplementation. The sums of squares for treatment effect were fur- ther separated into single degrees of freedom for comparisons of the dietary treatments (Snedecor and Cochran 1967). Results and discussion The liquid lysine product contained 67.9 g/kg pure lysine and by adding to the diet one gram of lysine supplied at the same time 0.56 g N which is shown as a small increase of N supply in the diets (Table 3). The supply of other amino acids to the diet by adding liquid lysine was negligible due to the low 217 Agric. Sei. Finl. 1 (1992) concentrations of these (Table 2). The average daily DM intake was 2013 g, increasing at the beginning of the experiment from 1388 g to 2617 g at the end, averaging 93 g/W0 7Vd during the trial. Refusals of the diet were negligible. Organic matter digestibility of the diets was on average 0.852 with the coefficient of variation (CV) being 0.0088. Average CP digestibility of the diets increased from 0.809 to 0.862 (P<0.001) during the trial, show- ing only a very small variation between the diets. The CV of CP-digestibility was as low as 0.013, indicating a very high precision of the experimental techniques. Lysine concentration in feed protein was calcu- lated to be 46, 34, 41, 47 and 53 g/kg protein in diets with SBM addition, without lysine supple- Table 3. The effect of lysine supplementation on the protein metabolism in pigs. DIET No Prot.supplement Lysine suppl.g Lysine, g/kg 4 5 6 7 8 SEM BP BP BP BP BP LL 2 LL 3 CL 1 CL 2 CL 3 7,5 8,5 6.5 7.5 8.5 I 2 3 SBM BP BP LL 1 7.4 5.5 6.5 N intake, g/d N faeces, g/d N absorbed, g/d N digestibility N in urine,g/d Urea-N, g/d Urea-N/tot.urinary-N N retained, g - of intake - ofabsorption - g/kg W0.75 Biological value Daily gain, g/d 55.7 56.2 57.5 9.4 9.6 9.8 46.2 46.6 47.8 0.825 0.826 0.826 19.3 24.7 23.4 17.7 20.5 20.9 0.776 0.839 0.764 26.9 22.0 24.4 0.478 0.385 0.425 0.579 0.466 0.515 1.23 1.00 1.14 0.647 0.540 0.585 808 682 781 58.7 59.8 56.3 56.7 57.3 0.188 10.0 10.1 9.2 9.8 9.3 0.237 48.6 49.8 47.1 47.0 48.0 0.254 0.823 0.827 0.833 0.825 0.828 0.0039 22.9 21.1 22.6 21.9 19.7 0.844 19.8 16.5 19.9 18.6 16.5 1.390 0.850 0.760 0.758 0.857 0.706 0.067 25.7 28.7 24.5 25.9 28.3 0.858 0.442 0.480 0.431 0.442 0.492 0.015 0.539 0.581 0.518 0.536 0.590 0.018 1.21 1.34 1.13 1.17 1.30 0.041 0.606 0.645 0.588 0.606 0.656 0.017 859 904 731 815 927 44.62 Statistical significance of effect Lysine supplementation Lysine form SBM vs. Barley prot. Linear Quadratic Liquid vs. lysine vs. lysine crystalline supplement supplement N intake, g/d *** NS *** *** *** N faeces, g/d NS NS ** NS NS N absorbed, g/d *** NS *** *** *** N digestibility NS NS NS NS NS N in urine, g/d ** NS NS ** ** Urea-N, g/d ** NS NS NS NS Urea-N/tot.urinary-N NS NS NS NS NS N retained, g *** NS NS NS *** -of intake *** NS NS NS *** -ofabsorption *** NS NS NS *** -g/kgWO.75 *** NS NS NS *** Biological value *** NS NS NS ** Daily gain, g/d *** NS NS NS ** SEM =standard error of the means; significance: NS =non-significant; ** (P<0.01), *** (P0.001). 218 Agric. Sei. Fin!. 1 (1992) mentation and with 1,2, and 3 g pure lysine / kg, respectively. The diets containing lysine 5.5-8.5 g/kg supplied total dietary lysine from 8.3 to 24.7 g/d during the experimental period and averaged 12.1, 14.3, 16.5 and 18.7 g/d for diets with different lysine concentrations. The results of the N balance and various calcu- lated parameters of protein utilization are shown in Table 3. The results indicate that dietary lysine con- centration had a substantial effect on nitrogen retention and metabolism. Lysine supplementation in barley-barley protein diet with dietary protein concentration (160 g/kg) according to the require- ment of growing pig, but insufficient for lysine requirements (5.5 g/kg), improved significantly (P<0.001) N retention and decreased urinary N excretion and enhanced protein utilization and also daily gain. There was a linear response of N reten- tion, urinary-N and urea-N excetion and apparent biological values (P0.001) to lysine supplementation. The efficiency of N retention in relation to N intake and absorbed N increased lin- earily with gradually increasing lysine concen- tration. No difference was found in N balance between the two lysine sources; liquid versus crys- talline form being equal in their response (P>0.05). Soybean meal as a lysine supplement compared to the pure lysine supplementation for equal dietary supply did not differ in response ofN retention and protein utilization (P>0.05), but lead to lower urinary-N excretion (P<0.01) and tended to achieve a littlehigher N retention in relation to N intake and biological value(P<0.06). The observation is simi- lar to the previous study in which soybean meal was isonitrogenously replaced by barley protein fortified with lysine (Näsi 1989). Since the threo- nine and sulphur-containing amino acid contents of the diets were marginally low, it is possibile that these amino acids could have become the limiting factors on addition of lysine. The fortification of the diet further with methionine and threonine did not have any response in the trial conducted by Näsi (1989) so that lysine was the limiting amino acid here, in accordance with the observations of replacement studies by Low et al. (1980) and Fuller et al. (1986). Contrary to these results, however, Fuller et al. (1979) found improvements of protein utilization with threonine supplemen- tations to barley diets. Nitrogen retention in this trial was on average 1.20 g/kgW075 /d (CV 0.095) showing the highest value (1.34) in the middle of the trial and lowest value at the end (1.10). The curve for nitrogen retention in relation to the live weight (30- 100 kg) at different periods is shown in Figure 1. Similar retentions have been noted by Thorbek et al. (1984) for pigs at 25-80 kg live weight (1.20 g/kgW075 /d) but much lower in heavier pigs (0.80 g/kgW075 /d). Berschauer et al. (1983) gave wider values of N-retention 0.46-1.85 g/kgW0 75 /d. The regression equations for N retention g/kgW° 75 /d as a function of lysine supplementation were 1.012 (SE 0.0307) + 0.092 (SE 0.0164) * X, R 2 = 0.628 (where X = suppl. of lysine g/kg) for crystalline lysine and 1.012 (SE 0.0389) + 0.108 (SE 0.0208) * X, R 2 = 0.457 for liquid lysine source. The regression equation relating N-retention to dietary lysine supplemen- tation indicates that lysine was used with a constant efficiency up to a supply of 8.5 g/kg. The response of daily gains of the pigs was in accordance with the N-retention results indicating that nitrogen bal- ance can reasonably explain the protein accretion in the body. Lysine supplementation of 1 g/kg feed achieved 0.1 increase in N retention in this study. Low and Pittman (1979) found N retention to improve sig- nificantly by 0.106 in response to 0.2 increase of extra lysine, total lysine from 7.0 to 8.4 g/kg, but further supplementation was of no benefit. An almost similar response to N retention as in the present study has been found in boars when lysine was supplemented 1.5 and 3.0 g/kg (total lysine 4.7-7.7 g/kg). However, in barrows, only supple- mentsup to 1.5g/kg improved retention (Williams et al. 1984). The genetical potential of the pigs causes a large variation in this respect. In the 219 Agric. Sei. Finl. 1 (1992) present experiment increasing increments of lysine to 8.5 g/kg of the diet did not reach a plateau so that the inflection point is at a higher concentration of lysine. The present observations of the response of protein utilization to supplemental lysine are in good agreement with theresults given by Fuller et al. (1974) where it was found that a minimum uri- nary N excretion was obtained when L-lysine was added to barley at the rate of 3.6 g/kg.Further addi- tions of lysine, methionine, isoleucine or trypto- phan were without effect but additon of threonine reduced N excretion substantially, demonstrating it to be the second limiting amino acid. Nitrogen retention in relation to absorbed N was low (0.466) in pigs fed diet, in which protein was provided by cereal protein only. Although barley protein derived in the starch ethanol process has a high digestibility of crude protein, 0.92 (Näsi 1989), its potential as a protein source is rather low, because it is composed of the storage protein frac- tions of the seed having a low unbalanced lysine content (30-35 g/kg protein) (Linko et al. 1989). Lysine supplementation improved the value up to 0.59, which is a similar value as that in a diet supplemented by lysine from soybean meal. Equal efficiencies of protein utilization have also been reported by Thorbek et al. (1984) in pigs on barley soybean diets. Protein utilization expressed as the ratio of retained N to absorbed N as function of lysine supplementation were 0.469 (SE 0.0132) + 0.039 (SE 0.0071) * X, R 2 = 0.583 (where X = suppl. of lysine g/kg) for crystalline lysine and 0.470 (SE 0.0147) + 0.037 (SE 0.0079) * X, R 2 = 0.405 for liquid lysine. The response of efficiency of N retention in rela- tion to absorbed N to supplemental lysine during the course of the experiment is shown in Figure 1. The values decreased with the development of the pig and with diets having higher lysine concentration. This is in line with the data pre- sented by Thorbek et al. (1984), who found 0.16 lower efficiency in pigs 80-120 kg live weight compared to pigs weighing 25-80 kg. Under practi- cal conditions growing pigs retain about 0.45 of N fed with typical diets based on barley and SBM. Studies with growing gilts by Fuller et al. (1979) have shown that supplementation of barley diet with lysine and threonine increased the BV of bar- ley protein from 0.51 to 0.86 while histidine supplement further increased the BV to 0.93. The highest efficiency ofN retention was achieved with diets having a ratio of at least 45:55 between the essential and the non essential amino acids. This included(g/16 g N) lysine 6.5, threonine 4.7, valine 4.9, methinine+cystine 4.1, isoleucine 3.9, leucine 7.2, phenylalanine+tyrosine 7.8 and tryptofan 1.2 (Wang and Fuller 1989). In the present study lysine concentrations in feed protein were from as low as 34 g/kg for protein without lysine supple- mentation where the diet was based on barley pro- tein, and increased gradually to 53 g/kg CP with lysine supplmentation, so that lysine levels were low in comparison to idealprotein composition. Lysine supplementation in the diet decreased urea excretion g/kgW075/d, and the regression equation for urea excretion as a function of crystal- line lysine lysine was found to be: -0.986 (SE 0.0403) - 0.072 (SE 0.0212) * X, R 2 = 0.434 (X = lysine supplement g/kg). The corresponding equation for liquid source was 0.996 (SE 0.050) - 0.074 (SE 0.0278) * X, R 2 = 0.176. If the diet is kept constant in other nutritive factors but its amino acid composition changes as in this study, urinary N excretion alone can be assumed to reflect total protein utilization (Low et al. 1980). The major end product ofamino acid catabolism in pigs is urea, the production ofwhich reflects amino acid catabolism more closely than total urinary N excretion (Eggum 1973,Fuller and Wang 1987). In this study the coefficient of variation in uri- nary urea-N excretion was 0.209, substantially higher than that ofurinary N which was 0.109. This may indicate decomposition of urea between col- lections despite acidification of the urine. In the liquid lysine source there may be some residual 220 Agric. Sei. Finl. 1 (1992) nitrogenous material from the fermentation of the molasses, and crude protein from the microbial cells, which may also increase the variation. Fuller et al. (1987) found in different studies with growing pigs that 0.95 ofurinary N excreted above N equilibrium is typically urea. In this study the ratio of the urinary urea-N of the total urinary N excretion was 0.79. A tendency to a quadratic responce of urea-N in relation to total urinary-N excretion (P<0.07) with lysine was noticed, diets with 7.5 g lysine/kg showed the lowest ratio. Increasing increments of lysine up to 8.5 g/kg showed a linear response of improved protein util- ization without reaching a plateau according to the parameters measured. The inflection point is at a higher concentration of lysine for pigs with improved genetical strain. Hankahan (1989) found the plateau region of lysine response as high as the 11 g/kg increment when daily gain and feed con- version were the criteria. There was a continued improvement in backfat reduction and increased lean meat content in pigs up to lysine concentration higher than that which gave the maximal growth response. However, Yen et al. (1986) achieved the maximal growth and carcass response at the same lysine concentration. The pigs in this study were Fig. I. Nitrogen retention and nitrogen retention in relation to absorption ofnitrogen in pigs at different experimental periods LL =liquid lysine, CL =crystalline lysine form. 221 Agric. Sei. Fin!. 1 (1992) castrated males, but in many investigations maxi- mum response was found in higher lysine levels for gilts or boars. The pigs in the present study were of high improved strain having a high potential for lean deposition which is indicated by the high daily gain. The conclusion is that the supply of a well bal- anced protein based on the use of reasonable quan- tities of synthetic pure lysine reduces the total pro- tein requirement due to the improved efficiency of protein utilization by bringing the pattern of ingested amino acids close to the needs of the pigs. Barley protein fortified with lysine could be substi- tuted for a major proportion of the protein of soy- bean meal without adverse effect on N-metabolism criteria of the pig. No difference was noticed in response of protein utilization to the form of lysine sources, the liquid form was as efficient as crystalline. References ARC 1981. The Nutrient requirements of farm livestock. Agricultural Research Council. Commonwealth Agri- cultural Bureaux, Slough. Beker, M.E., Wiestur, U.E., Latsars, A.A., Mezhinya, G.R. & Paberzs, A.O. 1971. Verfahren zur Herstellung des Futterkonzentrates von L-Lysin. Institut Mikrobiolo- gii imeni A. Kirhensteina Akademii Nauk Latvijskoi SSR. Pat. 93704. Berschauer, F., Gaus, G. & Menke, K.H. 1980. Effect of body weight on efficiency of utilization of energy and protein in pigs. Proc. Bth Symp. on Energy Metabolism, Cambridge. EAAP Pubi. 26: 101-105. Fuller, M.F, Livingstone,R.M., Baird, B.A. & Atkinson, T. 1979 a. The optimal amino acid supplementation of barley for the growing pig. 1. Responce of nitrogen metabolism to progressive supplementation. Br. J. Nutr. 41: 321-331. —, Mennie, I. & Crofts, R.M.T. 1979 b. The optimal amino acid supplementation of barley for the growing pig. 1. Optimal additions of lysine and threonine for growth. Br. J. Nutr. 41: 321-331. Wang, T.C. 1987. Amino acid requirements of the growing pig. In Manipulating Pig Production, p. 97-111. Australasian Pig Science Association. Werribee, Austra- lia. , Wood, J., Brewer, A.C., Pennie, K. & Mac William, R. 1986. The responses of growing pigs to dietary lysine, as free lysine hydrochloride or in soy-bean meal, and the influence of food intake. Anim. Prod. 43: 477-484. Hanrahan, T.J. 1989. The response of growing pigs to lysine. The Feed Compounder 7: 32-39. Just, A. 1982. The net energy value of crude catabolized protein for growth in pigs. Livestock Prod. Sci. 9: 349- 360. Linko, R., Lapveteläinen, A., Laakso, P. & Kallio, H. 1989. Protein composition of a high-protein barley flour and barley grain. Cereal Chem. 66: 478-482. Low, A.G. & Pittman, R.J. 1979. Responses of growing male pigs to practical diets supplemented with amino acids. Anim. Prod. 28: 435-436. —, Pittman, R.J. & Fulford, R.J. 1980. Studies on the opti- mum amino acid composition of practical diets for growing pigs using changeover nitrogen balance met- hod. Proc. EAAP Symp. on Protein Metabolism and Nutrition, p. 680-687. Braunschweig. 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. 1988. Evaluating barley feed fractions from integrated ethanol-starch production in diets ofruminants. J. Agric. Sci. Finl. 60: 701-709. - 1989. Barley feed fractions from integrated ethanol- starch process in diets of pigs. J. Agric. Sci. Finl. 61: 441-450. Snedecor, G.W. & Cochran, W.G. 1963. Statistical methods. 7th ed. p. 597. The lowa State University Press, Ames, lowa. USA. Thorbek, G., Chwalibog, A. & Henkel, S. 1984. Nitrogen and energy metabolism in pigs of Danish Landrace from 20 to 120 kg live weight. Norm for protein and energy requirements for maintenance and growth. Ber. Stat. Husbyrbr. fors. 563: 1-114. Wang, T.C. & Fuller, M.F. 1989. The optimum dietary amino acid pattern for growing pigs. 1. Experiments by amino acid deletion. Br. J. Nutr. 62: 77-89. Yen, H.T., Cole, D.J.A. & Lewis, D. 1986. Amino acid requirements of growing pigs. 7. The response of pigs from 25 to 55 kg live weight to dietary ideal protein. Anim. Prod. 43: 141-154. Manuscript received October 1991 Matti Näsi University ofHelsinki Department of Animal Science SF-00710 Helsinki, Finland 222 Agric. Sei. Finl. 1 (1992) SELOSTUS Nestemäisen ja kiteisen lysiinin vaikutus ohra-ohravalkuaisdieetillä olevien lihasikojen valkuaisen hyväksikäyttöön Maiti Näsi Helsinginyliopisto Tutkimuksessa selvitettiin nestemäisen ja kiteisen puhtaan lysiinin lisäysten vaikutusta ohra-ohravalkuaisdieetillä ruo- kittujen lihasikojen valkuaisen hyväksikäyttöön. Tutkimus tehtiin BxB latinalaisena neliönä 30-100 kg elopainoisilla lihasioilla. Rehun raakavalkuaispitoisuus oli kaikissa kah- deksassa koerehuseoksessa sama 160 g/kg. Lysiinitäyden- nykset olivat 1, 2 ja 3 g/kg puhtaana lysiininä kumpaakin lysiinilähdettä käytettäessä. Seosten kokonaislysiinipitoi- suudet olivat 5.5 g/kg täydentämättömässa seoksessa ja vas- taavasti 6.5, 7.5 ja 8.5 g/kg täydennetyissä rehuseoksissa. Vertailuseoksena oli soija-ohraseos, jossa oli 7.4 g/kg lysii- niä. Lysiinilisäyksellä verrattuna täydentämättömään dieet- tiin oli merkitsevä vaikutus moniin valkuaisen hyväksikäyt- töä kuvaaviin tunnuslukuihin. Lysiinin lisääminen paransi lineaarisesti typen pidättymistä ja valkuaisen biologista arvoa sekä vähensi virtsan typen ja urean eritystä. Sikojen typpitase parani keskimäärin 10 % lisättyä lysiiniä g/kg kohti. Lysiinilähteiden välillä ei ollut eroa. Soija-ohraseok- sella ruokittujen sikojen ja vastaavalla lysiintasolla olleiden ohra-ohravalkuaisella ruokittujen sikojen valkuaisen hyväk- sikäytössä ei ollut eroja. Tutkimuksen tulosten mukaan lysiinitäydennyksellä voitiin viljavalkuaisen biologista arvoa parantaa samaan tasoon kuin viljan ja soijan seos. 223 Agric. Sei. Fint. 1 (1992)