•V Maataloustieteellinen Aikakauskirja Vol. 61: 451—462, 1989 By-products from integrated starch-ethanol production from barley in the diets of growing cattle PEKKA HUHTANEN, MATTI NÄSI and HANNELE KHALILI Department of Animal Husbandry, University of Helsinki SF-00710 Finland Abstract. Two experiments were carried out to evaluate the nutritive value for growing cattle of by-products from a new process for integrated starch-ethanol production from bar- ley. Experiment I was a 4 x 4 Latin Square, in which the effects of barley protein (375 g crude protein (CP)/kg dry matter (DM)) on digestibility and N retention were examined in four male cattle (initial live weight (LW) 147 kg). The control diet (C) consisted of hay and rolled barley (1 : I). In isonitrogenous experimental diets, soybean meal (S), a mixture of soybean meal and barley protein (SB) or barley protein (B) was substituted for barley to increase the dietary CP content from 125 to 150 g/kg DM, Replacement of barley with protein supplements increased (P<0.01) the apparent digest- ibility of CP but had no effect on organic matter (OM) digestibility. Gradual replacement of soybean meal with barley protein decreased N retention linearly (P'o.l) linear decrease in LW gain (from 1278 to 1214 g/d). Feed conversion rate in terms of feed units per kg LW gain improved linearly (P <0.05) with the level of barley fibre. Carcass characteristics were not sig- nificantly affected by the diet given. Index words: barley protein, barley fibre, barley, rapeseed meal, silage, growing cattle 451 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=tvxZaOHeNns3TzzC.7etAVKDP-APFt4k47VC0gQ.TqNMdGRuuAgHEdJQtGfzoX85vk9Zm_39LNYsIDcTRNDvplU5xGlJSTeeeb3Rv8FHFPlPsv4mtuyElKYWCWwJFVzH0AZ7VDUCKJ-065q-k68x2nZHQ6uZc-_vgXY41FLqcoMs4ElMQzh63VAyO7DwSsQNCmkW9D4MZFgZEGCDInswvkoA8g4RerChwXfaxMOkCXfocO2jbHJ5jrLvBUmL5zI Introduction By-products from a new process for in- tegrated starch-ethanol production from bar- ley (Alko Ltd., Helsinki) are now available in Finland. The process, chemical composition and feed values of the products have been described by Nasi (1988). One of the by- products is barley fibre, consisting of the cell wall fraction of the endosperm (550 g neutral detergent fibre/kg dry matter (DM), 120 g starch/kg DM). In dairy cows given grass si- lage ad libitum the performance with barley fibre was found to be equal to (Huhtanen et at. 1988) or higher than (Ala-Seppälä et al. 1988) the performance with barley. High per- formance on barley fibre diets in spite of reduced estimated energy intake may be the result of improved forage digestibility, changes in the rumen fermentation pattern or nutrient partitioning. Barley protein is another by-product from the same process. The protein content of bar- ley protein is equal to or slightly higher than that of rapeseed meal, the most important domestic protein supplement in ruminant diets in Finland. The supply of amino acids to the tissues is often limiting the growth rate of cat- tle given grass silage based diets, and protein supplements have produced large responses in growth rate (eg. Waterhouse et al. 1983, Huhtanen et al. Gill et ai. 1987, Jaakkola et ai 1989). Although the high crude protein content of barley protein makes it an attrac- tive protein supplement for growing cattle, the protein degradability may be greater than that of oilseed meals, and the amino acid compo- sition of the undegraded protein may not be ideal. The effects of including these two by- products in the diets of growing cattle were studied in two experiments. In the first experi- ment the effect of barley protein on nutrient digestibility and N retention was studied rela- tive to the effect of soybean meal. The second experiment was planned to study the effect of replacing barley with barley fibre and inclu- sion of protected rapeseed meal in the diet on the performance of growing cattle given grass silage ad libitum. Material and methods Experiment I Four intact male cattle (initial live weight (LW) 147 kg; SE 12) were used in a 4 x 4 Latin Square experiment to study the effects of bar- ley protein from integrated starch-ethanol production (Näsi 1988) as a protein source for growing cattle. The control diet (C) con- sisted of hay and barley (1 : 1). Organic mat- ter (OM) digestibility of the hay was 0.615 in sheep. In isonitrogenous experimental diets, soybean meal (S), a mixture (1 : 1 on crude protein (CP) basis) of soybean meal and bar- ley protein (SB) and barley protein (B) were used to increase the dietary CP content from 125 to 150 g/kg dry matter (DM). The com- positions of the experimental diets are given in Table 1. Water was freely available and 100 g of a commercial mineral mixture was given daily. The feeding level was 90 g DM/kg LWn 75 based on the initial LW at the begin- ning of each period. The animals were kept in metabolism cages allowing a separate collection of faeces and urine. Each experimental period lasted 21 d, of which adaptation and standardization com- prised 14 d and total collection of faeces and urine was made during the final 7 d. The procedures used for faecal and urine collec- tion, the feed sampling and methods of chem- ical analyses have been described by Huhta- nen and Poutiainen (1985). Table 1. Formulation of experimental diets (g DM/ kg DM) in Exp. 1. Diet C S SB B 500 500 500 500 500 430 417 405 70 35 Hay Barley Soybean meal Barley protein 48 95 452 453 The analyses of variance for Latin Square experiments were made. The sums of squares for treatment effect were further separated into single degrees of freedom for compari- sons of diet C with the three other diets, and into linear and quadratic effects of the replacement of soybean meal withbarley pro- tein (Snedecor and Cochran 1967). Experiment 2 Design and diets A 3 X 2 factorial experiment was designed to compare barley (B), a mixture (1:1 on DM basis) of barley and barley fibre (BF) and barley fibre (F) as energy supplements, each given without additional protein (C) or sup- plemented with rapeseed meal (R) to growing bulls given grass silage ad libitum. Barley fibre obtained from integrated starch-ethanol pro- duction consists mainly of the cell wall frac- tion of the endosperm (Näsi 1988). Barley was fed in crushed form. Rapeseed meal (RSM) was treated for reduced degradability of N in the rumen (Öljynpuristamo Ltd., Hel- sinki, Finland). The concentrate supplements, including 0.5 kg of RSM on R diets, were given at the rate of 45 g DM/kg LW° 75 based on the initial LW of each 28 d experimental period. A commercial mineral mixture was supplied at the rate of 100 g/d throughout the experiment. All the ingredients of the concen- trate mixture were weighed separately and mixed prior to feeding. Grass silage was made from timothy-meadow fescue sward, which was harvested after a wilting period of 4—6 h using a precision-chop forage harvester and ensiled in a bunker silo with a formic acid based additive (AIV II; 800 g formic acid/kg, 20 g orthophoshoric acid/kg) applied at the rate of 4—5 1/t. Animals and management Animals were 12 Ayrshire bulls with a mean initial LW of 154 kg (SE 7.5) and 12 Friesian bulls with a mean initial LW of 172 kg (SE 11.3 kg). These were divided into four blocks by breed and LW, and within each block al- located to the treatments at random. All the animals were housed and fed individually twice daily. The treatments were imposed for 228 days (8 periods of 28 days). Measurements Samples of feeds offered were taken week- ly and analysed for DM. Silage samples were bulked over 4 weeks and concentrate samples over 8 weeks to provide the samples for ana- lyses. The analytical methods have been described by Huhtanen (1987). Feeds offered were weighed daily and refusals were recorded on 5 consecutive days per week. The animals were weighed on two consecutive days at the beginning and end of the experiment, and otherwise every 4 weeks. LW gains were cal- culated for each animal, either by difference method or from a second degree polynomial regression of LW on time. All the cattle were slaughtered at the end of the experiment. Dressing proportions were calculated from hot carcass weight. The car- cass quality and fatness were graded visually using the carcass classification scheme em- ployed in commercial slaughterhouses in Fin- land. To evaluate energy utilization, metaboliz- able energy (ME) requirements were calculat- ed for each animal for each 28 d experimen- tal period using the equations proposed by the Agricultural Research Council (Arc 1980). ME values for the feeds were calculated ac- cording to the Ministry of Agriculture, Food and Fisheries (Maff 1975). Corrected live weights and LW gains calculated from regres- sion equations were used to estimate ME re- quirements. The model used to analyse data was yijk | = H + E| + Pj + (EP)jj + B k + eijkl, where E, P and B are the effects of energy supplement, protein and breed. The effect of the energy supple- ment was further partitioned into linear and quadratic effects of the replacement of bar- ley with barley fibre, using polynomial con- trasts (Snedecor and Cochran 1967). Initial LW was used as covariate to analyse the data for feed conversion efficiency. Because there was no interaction between the energy supple- ment and additional protein, results are presented only for the main factors. Results The chemical composition and feed values of the experimental feeds are presented in Ta- ble 2. CP content of barley used in Exp. 1 was exceptionally high (155 g/kg DM). Barley pro- tein had a lower CP content than soybean meal (375 v. 527 g/kg DM). The silage used in Exp. 2. was of high quality in terms of both fermentation characteristics and D-value. Experiment I The digestibilities of the different dietary constituents are given in Table 3. There were no differences between the diets in the digest- ibility of OM, crude fibre or NFE. Apparent digestibility of CP was significantly (Po.l) (Table 6). Differences be- tween the energy supplements in their effect on LW gain were greater during the first 112 days (4 periods), diminishing towards the end of the experiment (Fig. 1). RSM supplemen- tation failed to enhance the LW gain during the experimental period as a whole. Although cattle given RSM had a substantially higher LW gain during the first 112 days (1293 v. 1200 g/d; SEM 33), this increase was totally lost by a faster gain during the last 112 days of the cattle fed without extra protein. Feed conversion rate in terms ofkg DM/kg LW gain was not significantly affected by the energy supplements, but in terms of FFU/kg LW gain, feed conversion was linearly im- proved (P<0.05) with the level of barley fibre in the diet. Cattle given RSM used more DCP/kg LW gain than those not given addi- tional protein. There were no significant differences in car- cass weight or carcass quality between the treatments (Table 7). Differences in carcass weight reflected differences in the initial LW and daily gain, because the dressing propor- tion was not affected by the diet given. Estimated ME supplies and calculated ME requirements for cattle given different ener- gy supplements (B, BE and F) are shown in Table 7. Comparison of observed data with require ments proposed by Arc (1984). Diet C S SB B RDN supplied 1 RDN required UDN supplied UDN required Tissue N 2 Assuming nitrogen degradabilities of hay, barley, soy- bean meal and barley protein to be 0.70, 0.80, 0.60 and 0.80. 2 Calculated according to Arc 1984. Fig. 2. ME requirement (+) and ME supply (*) during the experiment in cattle given the three energy supplements. 66.172.6 75.175.4 63.361.3 62.861.8 20.528.3 26.022.8 25.232.0 27.626.8 48.452.6 51.849.1 457 Fig. 2. In cattle given B diets, ME supply exceeded the ME requirement by 6.6 MJ/d and in cattle given F diets the ME supply was 2.7 MJ/d smaller than the calculated require- ment. On BF diet ME supply met the require- ment closely during the whole experiment. Discussion Experiment 1 Rumen microbial protein synthesis cannot supply enough amino acids for cattle weighing 100—200 kg when daily gains exceed 1 kg (Arc 1984), and protein supplements are widely used to increase LW gain. The animals used in the present study were at this range of LW, and ME supply was sufficient to al- low daily gains above 1 kg. This argues that differences in protein supply or quality would be reflected in changes in N retention. The relationship between the supply of N to the body tissues calculated as proposed by Arc (1984) was fairly close to the observed N retention (Table 7). When protein supple- ments were given, N retention increased with the supply of rumen undegradable protein (UDP). Rumen degradability of barley pro- tein cannot be determined by nylon bag tech- nique owing to the small particle size, and the value (0.80) for the ruminal degradability of N of barley was used instead. The real value may in fact be higher, since barley protein does not contain any cell wall bound N. Higher buffer solubility (McDougall) of bar- ley protein (0.291) than of barley (0.244) and soybean meal (0.095) also points to a higher degradability of barley protein. Higher N retention in cattle given diet S than in those given the control diet indicated that the hay-barley diet did not supply suffi- cient amino acids to the tissues for maximal protein deposition. Reduced N retention with increasing level of barley protein in the pro- tein supplement suggests either differences in the flow of UDP at the duodenum or in the quality of UDP. Methioninehas been suggest- ed to be the first limiting amino acid in microbial protein (Storm and orskov 1985), and on that basis soybean meal is not an ideal supplement for microbial protein. The lower methionine content of soybean meal than of barley protein (1.5 v. 1.8 g/16 g N) suggests that the differences in N retention are more likely to be related to the supply than the qual- ity of UDP. As compared with the control diet (C) barley protein had no effect on the N retention, indicating that also hay-barley diet supplied enough RDP. The absence of a re- sponse to barley protein in N retention is in agreement with the absence of response in a feeding experiment in growing cattle (Aronen 1988). However, in sheep fed a hay-based diet, increasing the proportion of barley protein in the diet enhanced N retention (Näsi 1988). The value of barley protein might be im- proved by treatments to reduce protein degradability in the rumen. Responses in growing cattle to the treatment of corn (Thornton et al. 1977) and barley (Huhta- nen et al. 1985) with formaldehyde contain- ing reagents have not been promising, though treatment of barley has increased milk yield in dairy cows (Kassem et al. 1987). Experiment 2 Protein supplementation The absence of any response in perfor- mance to protein supplementation of the grass silage based diet is in agreement with the results of Kirby et al. (1984), Steen (1985, 1988) and Steen and Moore (1988) but in contrast to many other experiments (eg. Waterhouse et al. 1983, Kirby et al. 1983, Huhtanen et al. 1985, Gill et al. 1987, Jaak- kola et al. 1987). Much of this variation can be attributed to the differences in the quality of the silage offered. According to Dawson et al. (1988), the greatest responses to fish meal have generally been obtained with medium- and poor-quality silages. With high- quality silage, reasonable (above 0.9 kg/d) LW gains can be achieved even when silage 458 is given alone (Lampila et al. 1988). The responses to protein supplements also seem to be related to the level of concentrate supple- ment and to the live weight of the animal greater effects being observed with small amounts of concentrates and small animals (Pike et al. 1988). The use of RSM as protein supplement in the present study should also be noted; in general, the best responses have been obtained with fish meal. Better response to RSM than in the present study was obtained by Huhtanen et al. (1985), but the animals in that study were smaller (320 kg at the end of the experiment). The silage used in the present study was of high quality, in terms of both fermentation characteristics (low concentrations of fermen- tation acids and ammonia N) and high digest- ibility (D value 0.641). This, together with the relatively high proportion of concentrate in the diet (380—440 g/kg DM), resulted in a high intake of digestible OM. The absence of response to RSM may therefore at least part- ly be attributable to high intakes of DOM, and to rumen microbial protein meeting more of the amino acid requirements with consequent smaller requirements of UDP. The low con- centration of ammonia N in the silage may also have contributed to better utilization of silage N compared with silages of poorer qual- ity. High performance in cattle given high quality of grass silage ad libitum with 2—3 kg of barley (Lampila et at. 1988, present study) would indicate that protein supply is not limit- ing the growth rate or the partitioning of ener- gy to lean meat deposition in carcass. Protein requirement per unit of energy decreases with increasing LW of the animal (Arc 1980), so that greater responses to pro- tein supplements can be expected at an early stage of the growing period. This was ob- served with RSM in the present study. How- ever, the LW gain advantage was completely lost due to the high degree of compensatory growth of animals not given additional pro- tein in the later part of the experiment. Steen (1988) found similar compensatory growth in experiment where fishmeal was included in a silage based diet. orskov et al. (1976) and Abdalla et al. (1988) found that the ruminants have an ability to compensate reduced LW gains through protein undernutri- tion when the supply of protein is later in- creased to meet the requirements. Hence, it may not be economical to try to achieve max- imal LW gains with protein supplements at 100—250 kg of LW. As was concluded by Steen (1989), additional protein should be offered to cattle given silage based diet to enable the concentrate input to be reduced rather than to increase the performance above the optimum. The effect of barley fibre Although barley fibre tended to depress LW gain, the marginal increase in LW gain per unit of an increase in energy intake with barley supplement was small (86 g/FFU and 8.2 g/ MJ ME). This can partly be attributed to high energy intake and performance on all diets, so that the genetic growth capacity of the animals was more limiting than energy intake per se. In dairy cows given grass silage ad libi- tum, milk yields have been equal to (Huhta- nen et ai. 1988) or greater (Ala-Seppälä et Table 8. Efficiency of utilization of metabolizable energy (ME) of growing cattle given grass silage ad libi- tum with different energy supplements. Supplement FBFB Metabolizability of diet ( q) 0.625 0.597 0.565 ME intake (MJ/d) 80.7 77.4 72.9 ME requirement (MJ/d) 74.177.2 75.6 Difference (MJ/d) +6.6 +0.2 —2.7 Predicted effi- ciency (Ay) 1 0.493 0.472 0.447 Estimated effi- ciency (Ay)2 0.423 0.477 0.499 Proportion of ME from digestible cell walls 0.34 0.43 0.52 ' Ay= 0.78(7+ 0.006 (Arc 1980). 2 Estimated energy retention/(ME intake —ME require- ment for maintenance) (Arc 1980). 459 460 al. 1988) with barley fibre than with barley supplement. The efficiency of the utilization of corn gluten feed, a by-product of the corn wet milling process, was 87—100 % that of corn depending on the type of diet and the level and type of corn gluten feed (Green et al. 1987). Estimated utilization of ME above main- tenance (k r) was lower on B diets than predicted from Arc equations (1980), and the opposite was true on F diets (Table 8). According to our results, q (ME/GE) does not provide an adequate basis for the predic- tion of k r. Thomas et al. (1988) suggested that the nature of ME may influence the effi- ciency, and in their study there was an inverse relationship between the proportion of ME derived from digestible cell walls and observed efficiency. The present results are in disagree- ment with those of Thomas et al. (1988), since here the estimated k, increased with the proportion of digestible cell walls. A similar trend was also observed by Jaakkola and Huhtanen (1989), who compared barley and unmolassed sugar beet pulp in the grass silage based diets of growing cattle. Three points may be relevant to these con- flicting results. First, the nature of the digest- ible cell walls was different. In the study of Thomas et al. (1988) the proportion of digest- ible cell walls in ME intake was increased by decreasing the proportion of barley in the diet, whereas in the present study and that of Jaakkola and Huhtanen (1989) the increase was achieved by increasing the NDF content of the concentrate. Second, the silage of the present study was much less extensively fer- mented than that of Thomas et at. (1988), with a much lower ammonia N content (47 v. 120—124 g/kg total N). Third, Thomas et al. (1988) used steers and we used bulls. There is also considerable room for error in this kind of calculation. ME intakes may be biased. Nylon bag incubations (Huhtanen 1989, unpublished) and digestibility studies (Huhtanen et ai. 1988, 1989, unpublished) suggest no reason for a higher the digestibili- ty of silage with barley fibre than with barley at this level of supplementation, or for a higher digestibility of barley fibre in cattle than in sheep. Higher propionate to butyrate ratio in rumen VFA in cattle given barley fibre than in those given barley (Huhtanen 1989, unpublished) would reduce methane losses to some extent and thereby increase the metabolizability of BF and F diets. Higher molar proportion of propionate of rumen VFA with barley fibre diets than with barley diets (Huhtanen, unpublished) may have provided more precursors (NADPH 2 and glycerol phosphate) for the conversion of ace- tate to fatty acids, which could explain the higher efficiency of utilization of ME with barley fibre diets. Also, the energy content of the LW gain may be different for the three diets. Higher kf on barley fibre diets suggests that the protein to fat ratio was more favoura- ble than on barley diets. Carcass classification did not indicate any major differences in the fatness of the carcasses, although on the ba- sis of the Arc (1980) system there would be 140 g/day more fat deposition on diet B than on diet F. It is concluded that barley protein has no value as a protein source for growing cattle. Moreover, in conditions like those of the pres- ent study, with high quality silage and approx- imately 400 g of concentrates per kg DM in- take, no response to supplementation with RSM can be expected. Although LW gains were slightly less with barley fibre than with barley, the performance on barley fibre diets was much better than could be expected from its proportionally 0.22 lower energy value de- termined in digestibility trials in sheep. The high estimated efficiency of the utilizationof diets containing barley fibre compared with diets containing barley indicates either effi- cient use of ME or changes in the fat to pro- tein ratio of gain. Acknowledgements. The authors thank Mrs. Sirkka Käyhkö, Miss Pirjo Korhonen and Mr. Juhani Vuoren- maa for technical assistance and the laboratory staff for chemical analyses. The financial support of Alko Ltd. is greatfully acknowledged. References Abdai.i a, H.0., Fox, D.G. & Thonney, M.L. 1988. Compensatory gain by Holstein calves after under- feeding protein. Anim. Sci. 66: 2687—2695. (Arc) Agricultural Research Council 1984. The Nutrient Requirements of Ruminants. Supplement 1. Com- monwealth Agricultural Bureaux. 44 pp. London. 1980. The Nutrient Requirements of Ruminants. Commonwealth Agricultural Bureaux. 351 pp. Lon- don. Ala-Seppälä, H., Huhtanen, P. & Näsi, M. 1988. 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Nutr. 52: 613—620. Steen, R.W.J. 1989. A comparison of soya-bean, sun- flower and fish meals for yearling cattle offered grass silage based diets. Anim. Prod. 48: 81—89. 1988.The effect of additive treatment of grass silage and food additive avoparein on the response of calves to supplementation of silage-based diets with fish meal. Anim. Prod. 47: 245—252. 1985, Protein supplementation of silage-based diets for calves. Anim. Prod. 41: 293—300. & Moore, C.A. 1988. A comparison of silage-based and dried forage-based diets for finishing beef cattle. Anim. Prod. 47: 29—37. Thomas, C., Gibb, 8.G., Beever, D.E. & Thurnham, B.R. 1988. The effect of date of cut and barley sub- stitution on gain and on the efficiency of the utiliza- 461 tion of grass silage by growing cattle. Br. J. Nutr, 60: 297—306. Thornton, J.H., Owens, F. N., Williams, D.E. & Ar nolo, M. 1977. Fermentation and digestion of form- aldehyde treated ensiled high moisture corn grain. Okia. Agr. Exp. Sta. MP-101; 62—67. Waterhouse, A., Laird, R. & Holliday, R.J. 1984. A response to protein supplementation of grass silage for growing cattle. Anim. Prod. 36: 503. (Abstr.). Ms received May 25, 1989 SELOSTUS Integroidun ohralärkkelys-etanoliprosessin sivutuotteet lihanautojen ruokinnassa Pekka Huhtanen, Matti Näsi ja Hannele Khalili Helsingin yliopisto, kolieläinlieteen laitos, 00710 Helsinki Tärkkelys-etanoliprosessin sivutuotteiden vaikutuksia kasvavien nautojen ruokinnassa tutkittiin kahdessa eri ko- keessa. Kokeessa I koejärjestelynä oli 4 x 4 Latinalainen neliö, jossa selvitettiin ohravalkuaisrehun (37.5 % raa- kavalkuaista kuiva-aineessa) vaikutusta dieetin sulavuu- teen ja typen pidättymiseen neljällä sonnilla (elopaino kokeen alussa keskimäärin 147 kg). Kontrolliruokinnal- la (C) eläimet saivat ohraa ja heinää (I : 1). Koeruokin- noilla osa ohrasta korvattiin soijarouheella (S), soijarou- heen ja ohravalkuaisrehun seoksella (SB) tai ohraval- kuaisrehulla (B). Dieetin raakavalkuaispitoisuus oli C- ruokinnalla 12.5 % ja koeruokinnoilla 15.0 %. Ruokinnoilla ei ollut vaikutusta orgaanisen aineen sulavuuteen, mutta dieetin raakavalkuaisen näennäistä sulavuutta lisävalkuaisen antaminen paransi merkitse- västi (P< 0.01). Soijarouhecnkorvaaminen ohravalkuais- rehulla vähensi typen pidättymistä lineaarisesti 32.0g:sta 28.9 g:aan/pv (P<0.05). Dieetin valkuaispitoisuuden li- sääminen yksistään ohravalkuaisrehulla ei lisännyt typen pidättymistä ohra-heinäruokintaan verrattuna. Kokeessa 2 tutkittiin ohrarehun (56.6 % NDF, 13.7 % raakavalkuaista kuiva-aineessa) tuotantovaikutusta kas- vavilla sonneilla, jotka saivat säilörehua vapaasti. Koe teli- tiin 3x2 faktoriaalisena kokeena, jossa väkirehuina oli- vat ohra (B), ohran ja ohrarehun seos (1:1) (BF) ja oh- rarehu (F), jotka annettiin joko ilman lisävalkuaista tai yhdessä rypsirouheen (0.5 kg/pv) kanssa. Väkirehua an- nettiin 45 g ka/kg W <)7s rypsirouhe mukaan luettuna. Koe-eläiminä oli 24 sonnia ja koe kesti 224 pv. Kokeessa käytetty säilörehu oli sekä käymislaatunsa että sulavuutensa puolesta hyvälaatuista, ja dieetin kuiva- aineen syönti oli runsasta (96 g/kg W075). Rypsirouheella ei ollut vaikutusta säilörehun syöntiin eikä lisäkasvuun. Ensimmäisen 16 viikon aikana rypsirouhe lisäsi päivä- kasvua 93 g, mutta tämä ero kompensoitui täydellisesti kokeen loppupuolella. Väkirehuilla ei ollut merkitsevää vaikutusta säilöiehun tai kuiva-aineen syöntiin. Ohran korvaaminen ohrarehulla vähensi hieman lisäkasvua (1278 g:sta 1214 g:aan/pv; P>o.l). Rehun muuntosuh- de (Ry/LK-kg) parani lineaarisesti (P<0.05) korvattaessa ohraa ohrarehulla. Laskelmat energian hyväksikäytöstä osoittivat, että ohrarehun tuotantovaikutus oli selvästi pa- rempi kuin lampailla määritettyjen sulavuuskerrointen pe- rusteella voisi päätellä. Tuotantokokeen perusteella oh- rarehun energia-arvoksi tuli noin 90 % ohran arvosta. 462