Effects of partial replacement of barley with rapeseed oil or birch wood in comparison to barley and oats on the performance and blood metabolites of lactating cows Alem Tsehai Tesfa, Mikko Tuori, Liisa Syrjälä-Qvist and Kaisa Kaustell Tesfa, A. T„ Tuori, M., Syrjälä-Qvist, L. & Kaustell, K. 1992.Effects of partial replacement of barley with rapeseed oil or birch wood in comparison to barley and oats on the performance and blood metabolites of lactating cows. Agric. Sci. Finl. 1: 255-265. (Univ. Helsinki, Dept. Anim. Sei. SF-00710 Helsinki, Finland.) Barley was partially replaced with either rapeseed oil (RSO), unextracted steam- exploded birch wood (Wl) or extracted steam-exploded birch wood (W2), and fed to 10 lactating cows (5 multiparous and 5 primiparous cows) in comparison to rolled bar- ley and oats. The experiment was designed in two balanced 5x5 Latin squares. The experimental periods lasted for4 weeks and the cows were fed with a fixed amount of 8 kg (air dry basis) concentrate in two equal portions. Timothy dominant unwilted grass silage was provided ad libitum. The nutrient digestibility, blood metabolites, milk yield and composition were studied. Grass silage intake decreased by replacing barley with RSO and increased with W 1 and W2. Oat feeding also increased silage intake compared to barley feeding. Oat feed- ing decreased the digestibility of the organic matter(OM) compared to barley. No sig- nificant difference was observed between diets in plasma concentrations of insulin, free fatty acids, acetoacetate, 6-hydroxybutyrate and glucose. Replacing part of the barley with RSO increased milk yield by 1.3 kg and 0.87 kg compared to oats and bar- ley feeding, respectively. Replacement of barley by low energy birch wood decreased milk yield. Both RSO and oat feeding decreased milk protein content. Milk urea con- centration was elevated by oats and depressed by RSO and birch wood. RSO and oat feeding decreased the short chain fatty acid content of milk, with a concomitant increase in stearic and oleic acids. Key words: milk yield, fatty acids, insulin, glucose Introduction Grain has been partly replaced or supplemented by fats and oil for dairy cows with the aim of increas- ing the energy density of the diet. Recently, fats have been included in an attempt to alter the fatty acid composition of milk, thereby improving its nutritional and physical properties. Direct feeding of oil/fat to a cow on the farm creates day-to-day handling problems due to their organoleptic cha- racter which limits their acceptance. An alternative approach to dietary manipulation of the fatty acid composition of milk fat is to feed lactating dairy cows with oats (Lampila and Heikkilä 1986; Mar- tin and Thomas 1988), because oats contain more lipid than barley or wheat, and its fatty acids are highly unsaturated (Morrison 1977). The digestibility of lignocellulosic materials like wood and wood products has been improved by chemical or steam treatments (Tarkow and Feist 1969; Bender et al. 1970; Reddy et al. 1972). Steam explosion is a method, where wood chips are 255 Agric. Sei. Finl. 1 (1992) https://www.c-info.fi/en/info/?token=OTr2KeXY9meoSv7Q.RIyWdXrDnLRXkGUUbegCZQ.Aot3Jb0U0LNyRHhg1uJA0iKIQ4ZooDaaR6-q2PvBFrzMMBBBUbr_kGiO79LWBTLt6hDnzR98HLp0URW-ZuwLrK7emN-dxD-_-EfobH8gJkJ4G2WJ2cnEHbk6IR22kL4L3RJRjIRbDyrnqt5ebYpfU9tNl1MB-FWjz5v_ixAl1m15c2pda0FSXmXVIpMdAXTQnJ3YPdtqfqrVdvv1sYlY-OgPG4UrLK_Sedp6S3VuGfSi2Ya_aa3OWLcLgrGjFGeOFHJWaSa-GGQh9VW47cYLXRVRNQ1b-UNU1riE3qVZShvBL4hAKddckPqD1RkZuJdd3xARWUJl2sG37u14gs16rhOcAiNQiNI steamed using saturated steam of over 200°C and a high speed discharge of steamed wood into the air, utilizing the concept of making popcorn. After the process, the hemicellulose of hardwood is hydroly- sed into a low molecular substance and it becomes water soluble. Cellulose is easily decomposed by enzymes, lignin is degenerated, and part of it be- comes soluble (Takigawa 1987). A 49-60 % digest- ibility has been obtained for steam-exploded aspen wood and white birch (Terada et al. 1986, ref. Takigawa 1987,Tuori 1990). Replacement of the dry matter of com silage by 20 % of steam-explod- ed aspen wood had no influence on milk yield or milk composition (Fisher 1980). In Japan, when steamed white birch comprised 15 % of dairy cow ration, it had no influence on yield, but 30 % of wood tended to decrease production (Miyamoto et al. 1986,ref Takigawa 1987). In Finland, birch wood is used as raw materialby xylitol manufacturers. Using the steam explosion method for birch wood it would be possible to sep- arate hydrolysed xylans for further processing. In this experiment, the effect of substituting barley with rapeseed oil or steam-exploded birch wood and water-extracted steam-exploded wood (xylans removed) on milk production was studied. The effect of oats and rapeseed oil feeding on the fatty acid composition of milk fat was compared to that of barley feeding. Material and methods Experimental design and animals Five primiparous (PP) and five multiparous (MP) Ayrshire cows that had calved on average 46 days before the start of the experiment, were used in a two balanced 5x5 Latin square design (MP and PP cows in separate squares). Each experimental period lasted for four weeks. Data from weeks 3 and 4 were used for the statistical analysis. One cow ceased eating before the completion of the fifth period, and the data on the oat diet was calcu- lated only on four observations. Feeds and feeding The concentrate feed was formulated as shown in Table 1. The first two grain feeds were rolled bar- ley (barley) and rolled oats (oats). An equal amount (w/w) ofrolled barley was replaced either by 0.4kg rapeseed oil (RSO), 2 kg unextracted steam-explod- ed birch wood (Wl), or 2 kg water-extracted steam-exploded birch wood (W2). Wl and W2 were lignocellulosic materials which were steam- exploded (Stake-process) under a pressure of 14 kg per cm2 at 210°C for 5 min to break the cell wall material and to facilitate digestion (Bender et al. 1970). Degraded xylans were removed from W2 by water extraction. Both Wl and W 2 were in a form of finely ground wad and were easy to mix with barley. RSO was from a double zero (00) variety of Brasica campestris. All cows received 1.3 kg (16 %ofconcentrate) soya bean meal as pro- tein supplement. Each ingredient replacing rolled barley was mixed manually with the barley before each meal. The cows were fed individually twice a day at 0600 h and 1400 h. Concentrate was offered 8 kg (air dry) d' 1 and first cut unwilted grass silage was given ad libitum throughout the trial.All diets were supplemented with a mineral mixture fed at a rate of 250 g d l . The apparent digestibility of feeds was determined on five multiparous cows using chro- mium oxide (Cr2 03) as an external marker. Cr203 impregnated paper (20 g Cr per day in two por- Table 1.Feed ingredients, kg (air dry basis). Dietary groupsIngredients Barley Oats RSO Wl W 2 Rolled barley 6.7 - 6.3 4.7 4.7 Rolled oats - 6.7 Soya bean meal 1.3 1.3 1.3 1.3 1.3 Rapeseed oil - - 0.40.4 Unextracted steam explodedbirch wood 2.0 Extracted steam- explodedbirch wood ... - 2.0 Mineral Mix 0.25 0.25 0.25 0.25 0.25 256 Agric. Sei. Finl. 1 (1992) tions) was introduced to the rumen using a stomach tube for eleven days on each period. The efficiency of utilization ofmetabolizable energy (ME) in milk production was calculated on the basis ofdigestible organic matter (5 MP cows). Recording and sampling The cows were weighed on two consecutive days at the beginning of the experiment, as well as in the middle and at the end ofeach period. The daily feed offered and refusals were recorded. The weekly feed samples were collected and pooled into one sample per diet per period. The pH and dry matter (DM) content were determined from the weekly sample of grass silage for quality control purposes. An extra weekly sample was frozen at -18°C for the determination offermentation characteristics. The milk yield was recorded at each milking and sampled at four milkings during the two last weeks of each period for the determination of fat, protein, urea, lactose and fatty acids. Blood samples were collected from the jugular vein (Vena jugularis) into vacutainers on day 24 at 0,2, 4 and 6 h post- morning feeding. Plasma was separated by centri- fuging at 2000 rpm for 10 min and deep frozen at -18°C until analysed for insulin and free fatty acids (FFA) concentration. Samples for 13-hydroxy- butyrate (BHBA) and acetoacetate (AA) analyses were immediately precipitated with 2 ml of 0.6 M perchloric acid to avoid loss of AA and kept at -18°C (Työppönen and Kauppinen 1980). Faecal grab samples were collectedrectally twice a day at 0800 and 1500 h for 6 days, starting on the 23 day, and stored at -18°C. At the end of the collection period, samples were thawed and pooled into one sample per treatment. Chemical analysis Feeds and milk samples were analyzed as described previously (Tesfa et al. 1991). Faecal samples were analyzed for DM by drying at 105°C to con- stant weight, and for organic matter (OM) by ashing in a muffle furnace at 550°C for 24 h. Fresh faecal and dried feed samples were determined for crude protein by the Kjeldahl method. Dried faecal and feed samples were used for the determination of neutral detergent fibre (NDF) and acid detergent fibre (ADF) (Goering and Van Soest 1970). Chromium in faeces was determined by atomic absorption spectrophotometry (Williams et al. 1962). The blood glucose concentration was analyzed by the enzymatic glucoseoxidase and FFA by an enzymatic colorimetric method (Wako chemicals). Insulin was analyzed by radioimmunoassay using a double antibody solid phase technique (Phadeseph Insulin RIA). AA and BHBA were analyzed accord- ing to Hansen and Freier (1978) with a Gilford 3500 analyzer at a temperature of37°C and a wave- length of 340 nm. Milk urea was determined with an enzymatic colorimetric system according to Rajamäki and Rauramaa (1984). Statistical Analysis The data were analyzed by the least square analysis ofvariance using: Model I. For apparent digestibility of nutrients: Yijkl =p+C+D. + Pk + eijk|, where pis the mean, and C, D, and P are cow, diet and period effects, resprctively, and ejk| is the residual effect. Model 11. For production parameters: YiJklm = M + S,+ C(S,) + P k + Dj+ (SP)]k+ (SD),j + where C, P, and D are as above. S is the square (parity) effect and SP is the square*period effect, SD is the square*diet effect and ejjklm is the error. Model 111. Blood metabolites were analyzed using a split-plot analysis ofvariance using the following model: Yljkta =R+SI +C(S 1) + P k +D j+ e j,kj+ Tm + Tm(Ci(S,)) + (PT)km + (DT) jm + eikj|m , where T m is the sampling time effect, e ikj is the main plot error, T m(C j(S 1)) is the interaction between cow and sam- pling time; (PT)km, is the interaction between period and sampling time, (DT). m, is the interaction between diet and sampling time, and eikj|m is the sub-plot error and p is the constant. The differences 257 Agric. Sei. Fin!. 1 (1992) between treatments were tested with Tukey's test (Steele and Torrie 1960). Values given in Tables 3-8 are least square means oftreatments. Results The mean chemical composition and feed values of feeds used are given in Table 2. As can be seen from Table 3, the total DM intake in barley and oat diets was equal. However, the cows fed with oats had more leftovers of concentrate. Silage intake decreased by 0.5 kg whenRSO replaced part of the barley and increased by 0.6 kg with oat feeding. The main difference in feed intake was the in- creased (1.1 kg DM) silage intake by cows fed on W 2 increasing their total DM intake by 1 kg com- pared to barley or oats fed cows. Multiparous cows consumed 2.1 kg DM more than the PP cows. Feed apparent digestibility The digestion coefficients of dietary nutrients are given in Table 4. Oat feeding decreased (P<0.05) the digestibility of OM compared to barley. Crude protein (CP) digestibility was higher (P<0.05) for the oat group than for the RSO group. Table 2. Chemical composition of experimental feeds. Silage SBM Barley Oats W 1 W 2 DM, g kg' 1 246 877 869 874 970 968 Compositions, g kg' 1 DM Ash 72 66 24 31 5 3 Crude protein 162 486 139 157 7 8 Crude fat 48 42 36 60 14 22 Crude fibre 254 71 57 130 413 524 Nitrogen free extract 461 335 744 622 561 444 Neutral detergent fibre 490 123 211 330 583 728 Acid detergent fibre 268 75 60 148 544 685 Acid detergent lignin 20 3 10 27 71 86 Feed value ME, MJ kg 1 DM 10.09 12.65 13.67 12.22 8.53 5.53 DCP.gkg 1 DM 109 437 104 129 FFU, kg" 1 DM 0.72 1.07 1.17 1.03 0.71 0.43 SBM, soya bean meal; DCP, digestible crude protein; ME, Metabolizable energy (MAFF 1975); FFU, fattening feed units = 0.7 kg starch (Salo et al. 1982). Table 3. Mean daily feed intake, kg DM d' 1 cow 1. Dietary groups Cow naritv Barley Oats RSO W 1 W 2 SEM MP PP SEM Total 17,4 17.4 17.1 17.8 18.4 0.23 18.6 16.5 0.14 Silage 10.6 11.2 10.1 10.8 11.7 0.25 11.7 10.0 0.16 Concentrate 6.8 6.2 7,0 7.0 6.7 0.15 6,8 6.3 0.09 NDF 6.6 7.4 6.3 7.5 8.0 0.11 7.6 6.6 0,06 Total fat 0.75 0.88 1.12 0.72 0.77 0.13 0.89 0.78 0.01 CP 2.99 3.05 2.90 2.81 2.92 0.04 3.10 2.76 0.03 MEMJd-' 195 187 201 191 191 2.50 204 182 1.58 See Table 2. for NDF and ME. CP, crude protein. 258 Agric. Sei. Fin!. 1 (1992) Table 4. Digestibility coefficients of dietary nutrients. Dietary groups Barley Oats RSO Wl W 2 SEM Dry matter 0.737 0.697 0.710 0.705 0.685 0.0074 Organic matter 0.752 0.709 0.725 0.717 0.696 0.0073 Crude protein 0.718 0.737 0.700 0.699 0.710 0.0071 Ether extract 0.575 0.633 0.610 0.544 0.560 0.0119 Neutral detergent fibre 0.677 0.607 0.637 0.662 0.627 0.0127 Acid detergent fibre 0.671 0.622 0.629 0.649 0,592 0.0131 SEM, Standard error of mean. Table 5. Effects of dietary treatment and cow status on blood acetoacetate (AA), 13-hydroxybutyrate (BHBA), glucose and free fatty acids (FFA) (mmol I 1) and insulin (mU T 1). Dietary groups Cow parity Barley Oats RSO W 1 W 2 SEM MP PP SEM AA 0.142 0.143 0.154 0.161 0.144 0.016 0.154 0.144 0.010 BHBA 0.817 0.822 0.831 0.886 0.796 0.103 0.878 0.783 0.065 FFA 0.155 0.174 0.173 0.165 0.150 0.021 0.176 0.151 0.013 Glucose 2.58 2.52 2.57 2.46 2.57 0.102 2.52 2.56 0.064 Insulin 31.3 31.9 32.4 29.8 28.5 7.005 37.8 23.1 4.430 MP, multiparous; PP, primiparous; SEM, standard error of mean. Blood metabolites Although there was some variation in blood meta- bolites between cows fed on the different diets, none of these differences were statistically signific- ant, except for BHBA on Wl and W 2 (Table 5). There was a slight increase in AA, FFA, BHBA and insulin concentration on RSO. Insulin concentra- tions slightly decreased on W 1 and W 2 diets. The blood metabolites of both multiparous and first lactation heifers were generally similar. However, blood insulin (23.1 vs 37.8), blood FFA (0.151 vs 0.176) and BHBA (0.786 vs 0.878) were lower for PP cows than for MP cows. No significant change in body weight (0.22 vs 0.10 kg d 1) was observed between cow parity. Milk yield and composition The overall milk yield of cows fed with oats, Wl and W 2 is lower as compared to barley fed cows. A more significant (P<0.01) difference was observed between cows fed on oats and RSO (Table 6). Slightly more milk fat was produced by animals fed on Wl as compared to those fed on W2. Replace- ment of barley with RSO decreased milk fat con- tent and increased milk yield by 5.4 % (0.87 kg d 1) compared to barley, but this increment was not sta- tistically significant (Table 6). A decrease (P<0.05) of milk protein content was observed in cows fed with oats and RSO compared to those fed withbar- ley. The milk urea content of cows fed oats was increased (PO.01); those fed with Wl and W2 showed a decrease (P<0.01) compared to those fed with barley. There was no significant difference between those fed with RSO and barley. Similar to their total feed intake, milk yield and FCM yield was significantly (P<0.001) higher for MP cows compared to PP. The efficiency of utilization of ME in milk pro- duction is given in Table 7. There was no signific- ant (P>0.10) difference in efficiency of utilization 259 Agric. Sei. Fin!. 1 (1992) Table 6. Effects of diet and cow status on daily milk yield (kg) milk composition (g kg '), and live weight changes (LWC). Dietary groups Cow parity Barley Oats RSO Wl W 2 SEM MP PP SEM Yields, kg d 1 Milk 24.6 24.2 25.5 23.3 22.9 0.30 26.6 21.4 0.19 FCM 25.9 25.5 26.4 24.6 24.1 0.40 27.8 22.8 0.25 Fat 1.07 1.05 1.08 1.02 0.99 0.016 1.14 0.94 0.010 Protein 0.79 0.75 0.79 0.74 0.75 0.008 0.85 0.68 0.009 Lactose 1.12 1.12 1.18 1.07 1.05 0.011 1.19 1.02 0.007 Compositions, g kg' 1 Fat 43.6 43.6 42.9 44.3 43.6 0.59 43.5 43.7 0.37 Protein 32.4 31.1 31.4 32.2 32.7 0.58 32.3 32.1 0.36 Lactose 45.6 46.2 46.5 45.9 46.0 0.26 45.0 47.1 0.16 Urea, mg 100'ml 31.6 37.6 30.8 27.6 29.5 0.75 30.1 32.6 0.47 LWC, kgd 1 -0.13 0.21 0.24 0.15 0.32 0.11 0.10 0.21 0.07 FCM =0.4 * milk yield + 15 * fat yield; See Table 5 for MP, PP and SEM. Table 7. Efficiency ofutilization ofmetabolizable energy for milk production (5 multiparous cows). Dietary groups Barley Oats RSO W 1 W 2 SEM Intake, Dry matter, kg 18.2 18.4 18.1 18.9 19.7 0.41 DE, Mid' 244.4 236,9 239.0 241.8 245.6 4.97 ME, Mid 1 210.2 203.8 205.5 207.9 211.2 4.27 NE requirement 122.5 126.5 127.9 121.2 127.5 3.90 For production (NE,) 86.7 85.3 88.1 82.1 80,8 1.88 For maintenance 37.2 37.1 37.0 37.3 37.0 0.12 In weight change -1.4 4.2 2.8 1.8 9.7 5.02 Efficiency k, 1 0.57 0.58 0.59 0.55 0.52 0.024 k, 2 0.55 0.60 0.61 0.55 0.60 0.023 DE, digestible energy = 24.2 * DCP + 34.1 * digestible crude fat + 18.5 * digestible crude fibre+ 17.0 * digestible nitrogen free extracts (Floffmann and Schiemann 1980); ME, metabolizable energy =0.86 * DE; NEI, net energy for milk production =milk yield * (0,383 * fat % + 0.242 * protein % +0.165 * lactose % + 0.0207) (Baevre et al. 1988); k, 1, ME for milk pro- duction corrected for maintenance and live weight change; k, 2 , without considering live weight changes requirements; See Table 5. for SEM. of ME in milk production between cows fed with oats and RSO, but cows fed with oats were more efficient than those fed with barley, when cor- rections were made for changes in live weight and for maintenance. Differences in body weight change were not significant (P>0.10) between treatments. However, the trend suggests that cows fed on barley were mobilizing more tissue than cows on other diets. 260 Agric. Sei. Finl. 1 (1992) Milk fat fatty acids There was no significant (P>0.10) difference between diets on certain fatty acids such as C 4 C6:o’ C 10:l’ C 12;0 C.4:P C 18:3 alld C20:0 (Table 8)' Concentrations of Cl2 C ]4.o and C l 6 0 decreased on oats and RSO feeding, but no apparent difference was observed between barley, W 1 and W 2 feeding on these fatty acids. Substitution ofRSO for barley significantly decreased (PO.OOl) C l6O and in- creased C ]g o and C |B ] fatty acids compared to barley. Table 8. Fatty acid composition ofmilk fat, g 100 g' 1 of total fatty acids. Dietary groups Barley Oats RSO W 1 W 2 SEM C4:O 3.7 3.8 3.9 3.5 3.5 0.12 C6:O 2.8 2.7 2.8 2.6 2.6 0.08 C8:0 1.8 1.8 1.8 1.6 1.6 0.05 CI0:0 4.4 3.7 3,9 3.8 3.9 0.11 CIO.T 0.5 0.4 0.4 0.4 0.4 0.02 C12:0 4.9 4.0 4.1 4.3 4.5 0.12 C12:1 0.1 0.1 0.1 0.1 0.1 0.06 €14:0 13.7 12.9 12.6 13.7 13.8 0.21 €14:1 1.2 1.2 1.1 1.2 1.3 0.03 C 15:0 1.0 0.9 0.9 1.0 1.1 0.03 C16:0 34.531.9 26.436.1 36.00.58 C 16:1 1.5 1.3 1.0 1.5 1.5 0.06 C18:0 8.010.2 12.38.1 7.90.27 C18:1 14.317.7 20.014.2 13.80.55 ClB:ltrans 0.4 0.4 0.5 0.4 0.4 0.02 €18:2 1.7 1.5 1.8 1.6 1.6 0.121.7 1.5 1.8 1.6 1.6 0.12 ClB:2Conj. 0.3 0.4 0.4 0.4 0.4 0.02 €18:3 0.4 0.4 0.4 0.5 0.5 0.010.4 0.4 0.4 0.5 0.5 0.01 See Table 5. for SEM. Discussion and conclusion Two hypotheses were proposed in this experiment. The first hypothesis was that if part of the grain in the ration is replaced by fat/oil, the daily milk yield will not be higher than with the control concentrate feed, or it will be lower than with the control concentrate feed due to the negative effect of fatty acids on the rumen environment. The second hypothesis was that low energy lignocellulose feeds can sustain milk production when grass silage is provided ad libitum. The results confirmed however, that the daily milk yield can be increased by replacing part of barley with RSO but not with birch wood. Feed intake and digestion We observed increased silage DM intake and decreased concentrate intake by cows fed with oats compared to barley fed cows. This is contrary to the findings ofMartin and Thomas (1987) with lacta- ting milking cows. The reduced silage intake by cows fed on RSO agrees with the work of Steele (1985) where soya bean oil or crushed soya beans were added to silage and fed with supplementary protein. W 1 and W 2 fed cows consumed more silage to compensate the low energy content of the concentrate diet. Although there was a substantial difference in energy content of the test feeds, it seems that the difference in energy intake was com- pensated by higher silage intake by cows fed on W 1 and W2. The decrease in apparent digestibility of OM by cows fed with RSO was expected due to its toxic effect on cellulolytic organisms. However, the reduction in OM digestibility with RSO feeding observed in this trial was not significant. The absence of a negative effect on nutrient digestibility with RSO feeding to cows is in agreement with the reports ofPalmquist and Conrad (1978). Under conventional feeding systems, the feeding of wood industry by-products to milking cows is not customary. A basic argument against its use is its low digestibility. Contrary to this, the apparent digestibility coefficient of OM was higher in cows fed W 1 than in those fed with oats. In fact, it was observed that RSO and oats depressed the digest- ibility of NDF and ADF more than W 1 did . The lower digestibility of OM, NDF and ADF observed with oats compared to barley and RSO feeding was not expected. We assume that this depression can 261 Agric. Sei. Finl. 1 (1992) be attributed to the exceptionally high fibre content of the oats used in this trial. Blood metabolites and milk yield It is expected that silage based diets that contain less fibre than hay based diets would interact with RSO or fat from oats to increase propionate pro- duction in the rumen (Steele and Moore 1968) and to increase blood glucose. This increased out- put of glucose then concomitantly increases plasma insulin which redirects fat synthesis from mammary tissue towards adipose tissues (Vernon 1980). However, in the present study neither glu- cose nor insulin concentration was significantly increased on RSO or oat feeding. Regarding plasma glucose concentration on RSO feeding, the result is contradictory to the previous observation with increasing level of rapeseed oil feeding to cows (Tesfa et al. 1991). There were no significant changes in the BHBA or AA of blood plasma either. Therefore, the slight depression in the milk fat content seems not to have been caused by an alteration in concentration of blood metabolites on RSO diet. The observed slight increase in BHBA on RSO diet probably resulted from the oxidation of dietary fatty acids (Steele 1984). The increase in BHBA, therefore, cannot be attributed to any pathological condition as the cows were in a posi- tive energy balance during the observation. In the case of W 1 fed cows, the elevated BHBA concen- tration could be due to high butyrate production in the rumen from the xylose contained in the birch wood. An increased milk yield with oats compared to barley at a similar level of DM intake by the cows has been reported (Heikkilä et al. 1988; Lampila and Heikkilä 1986; Martin and Thomas 1987; Moran 1986). In our study, despite similar DM intakes, cows fed with oats produced less milk than barley and RSO fed cows. Moss and Frier (1981) also reported increased FCM yield on oat diet, al- though oats is inferior to other grain on the basis of its ME content. In the present study, oats depressed milk, FCM and protein yields compared to RSO. RSO diet slightly increased milk and FCM yield and sustained milk protein yield but decreased milk fat and protein contents compared to barley. The reported depression in milk fat content with oats (Martin and Thomas 1987) and with canola oil (Beaulieu et al. 1990) is in agreement with our observation with oat and RSO feeding. The feed values of non-conventional feeds such as W 1 and W 2 are low compared to grain for high yielding milking cows. Owing to this fact, reduced milk yield was inevitable with W 1 and W 2 compar- ed to both grain sources. The slightly higher or sus- tained milk fat content of cows fed with W 1 and W 2 can be viewed as a result of high intake of silage and higher fibre content of the birch wood- barley concentrate. This would have provided high output of acetate which in turn would be used to enhance de novo synthesis of short chain fatty acids of milk fat (Moore and Christie 1979). However, the short chain fatty acid concentration of milk fat from cows fed with W 1 and W 2 was lower compar- ed to that of barley fed cows. The milk protein content has been found to res- pond to diets containing high fat negatively (Depe- ters et al. 1987, Steele 1985). Compared to con- trol diets, additional fat containing diets may cause a decrease in milk protein content but an increase in milk yield (Banks et al. 1980), the protein yield remaining unchanged. Contrary to these findings, Steele et al. (1971) observed an increase in milk protein yield on soya oil feeding. When cows consumed complete diets containing 600 gkg' 1DM as oats or barley, the oat diet reduced the milk protein content (Moran 1986). Martin and Thomas (1988) also observed decreased milk protein yield and content when cows were fed with oats. Although the effect of oats on the milk protein content varies slightly, our observation is in agree- ment both with the work of Martin and Thomas (1988) and that of Moran (1986). However, the higher negative effect of oats than RSO on the milk protein yield and content was not expected. The increase in milk urea content from cows fed with oat diet can be explained as a result ofhigher intake of crude protein. 262 Agric. Sei. Finl. 1 (1992) Milk fatty acid composition The effects of oats on the fatty acid composition of milk fat resembled those observed in response to dietary fat containing diets (Storry 1981; Clap- perton and Banks 1985; Tesfa et al. 1991). De- pression in short- and medium chain fatty acids on oats and RSO was expected as the dietary unsatura- ted fatty acids are thought to reduce de novo synt- hesis of C 6 0 - C l 6 0 fatty acids within the mammary gland through a reduced supply of acetate, which apparently inhibits mammary acetyl-CoA decarbo- xylase (Clapperton and Banks 1985; Mattos and Palmquist 1974). The increase in the proportions of C |B o and C in milk fat on RSO and oat diets is due to the hydrogenation of unsaturated fat in the rumen and subsequent intramammary desaturation of the ClBO formed (Banks et al. 1980; Christie 1981). RSO raised the proportion of Cl8:1 trans- fatty acid in milk fat, similar to the reports ofKen- nelly (1987) with diets containing full-fat canola seed. The elevated trans- fatty acid is a result of the hydrogenation of oil in the rumen as has been observed in our previous study (Tesfa et al. 1991). Based on the results obtained in this study, both oats and RSO diets showed a substantial reduction in C, nn - €,<„ fatty acid content of milk fat with a iu:u io:u J concomitant increase in C lBo and Clg|. However, oat feeding and replacing barley with RSO was observed to result in decreased milk protein content. Although there is a need, both nutritionally as well as technologically, for changing the fatty acid composition of milk fat, the emphasis should not be put on replacing grain with fat. Because replacing grain with fat reduces the availability of fermentable carbohydrate which could be used as energy sources by rumen microbes. Therefore, oil should be used as a supplement to the basal diet rather than as a replacement. References Baevre, L., Junkkarinen, L., Pedersen, J., Setälä, J. & Sjaunja, L.O. 1988. A Nordic proposal for an energy corrected milk (ECM) formula. International committee for recording the productivity of milk animals (ICRPMA) 26th session. 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Factors affecting the yields of milk and its constituents, particularly fatty acids, when dairy cows consume diets containing added fat. J, Sci. Food Agric. 36: 1205-1211. Depeters,E.J., Taylor, S.J., Finley, C.M. & Famula, T.R. 1987.Dietary fat and nitrogen composition ofmilk from lactating cows. J. Dairy Sci. 70: 1192-1201. Fisher, L.J. 1980. An evaluation ofsteam-treated aspen as a substitute for com silage in the rations of lactating cows. Can. J. Anim. Sci. 60: 379-384. Goerino, H.K. & Van Soest, P.J. 1970. Forage fibre analy- sis. U.S.D.A. Agricultural Flandbook, No. 79. Hansen, J.L. & Freier, E.F. 1978. Direct assays of lactate, pyruvate, 6-hydroxybturate, and acetoacetatewith cent- rifugal analyzer. Clin. Chem. 24: 475-479. Heikkilä, T., Väätäinen, H. & Lampila, M. 1988. Barley or oats for dairy cows. Procedigs VI World Conference on Animal Production. 2.119 (Abst.) Hoffmann, L. & Schiemann, R. 1980. Von der Kalorie zum Joule: Neue Größenbeziehungen bei Messungen des Enegieumsatzes und bei der Berechnung von Kennzah- len der energetischen Futterbewertung. Arch. Fiir Tierenährung. 30: 733-742. Kennelly, J.J. 1987.Full-fat canola seed for lactating dairy cows. In: Research on canola seed, oil, meal and meal fractions, Bth progress report. 63: 257-262. Canola 263 Agric. Sei. Fin!. 1 (1992) Council ofCanada, Winnipeg. Lampila, M. & Heikkilä, T. 1986. Ohraa vai kauraa lypsy- lehmille? Karjatalous 62: 35-36. MAFF. 1975. Energy allowance and feeding systems for ruminants. Tech. 8u11.33, 79 p. London. Martin, P.A & Thomas, P.C. 1987.Milk yield and compo- sition in cows given barley or oats as supplements to grass and lucerne silage. Eight silage conference. AFRC, IGAP, Herley. p. 177-178. & Thomas, P.C. 1988. Dietary manipulation of the yield and composition of milk: Effects of dietary inclusion of barley and oats in untreated or formaldehyde treated forms on milk fatty acid composition. J. Sci. Food Agric. 43: 145-154. Mattos, W. & Palmquist, D.L. 1974. Increased polyunsat- urated fatty acid yields in milk ofcows fed protected fat. J. Dairy Sci. 57: 1050-1054. Millett, M.A., Baker, A.J., Feist, W.C., Mellenberger, R.W. & Sätter, L.D. 1970.Modifying wood to increase its in vitro digestibility. J. Anim. Sci. 31: 781-788. Miyamoto, S. et al. 1986, Feeding trial of lactating cow by steamed white birch (the first report). Jpn. Soc. Zootech. Sci. 78 Ann. Meeting Abs. 60. Moore, J.H. & Christie, W.W. 1979. Lipid metabolism in the mammary gland of ruminant animals. In: Holman, R.T. (ed.). Progress in Lipid Research. Vol. 17. 366 p. Pergamon Press, Oxford. Moran, J.B. 1986.Cereal grains in complete diets for dairy cows: A comparison ofrolled barley, wheat and oats and of three methods of processing oats. J. Anim. Prod. 43: 27-36. Morrison, W.R. 1977. Cereal lipids. Proc. Nutr. Soc. 36: 143-148. Moss, B.R. & Prier, S.G. 1981. 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Fint. 1 (1992) SELOSTUS Ohra, kaura sekä osittain rypsiöljyllä tai höyryräjäytetyllä koivulla korvattu ohra säilörehuvaltaisella ruokinnalla lypsylehmillä Alem Tsehai Tesfa, Mikko Tuori, Liisa Syrjälä-Qvist jaKaisa Kaustell Helsingin yliopisto Tässä kokeessa tutkittiin energiatäydennyksen vaikutusta maitotuotokseen ja maidon koostumukseen korkean mai- dontuotantokauden aikana säilörehuvaltaisella ruokinnalla. Väkirehun energiaväkevyyttä lisättiin rypsiöljytäydennyk- sellä tai energiaväkevyyttä vähennettiin vaihtamalla väkire- hun ohra kauraan tai korvaamalla osa ohrasta höyryräjäyte- tyllä koivulla. Viimeksimainittu tuote oli valmistettu ns. Stake-prosessilla, missä haketettu koivu kuummennetaan kyllästetyssä vesihöyryssä yli 200 °C:seen. Kun paine äkilli- sesti alennetaan, lehtipuun hemiselluloosa hydrolysoituu ja tulee vesiliukoiseksi. Entsyymit pystyvät tällöin hajotta- maan helpommin selluloosaa, jamyös ligniinistä osa hajoaa ja tulee liukoiseksi. Koivun hydrolysoituneet ksylaanit voi- daan uuttaavedellä jakäyttää esim. ksylitolin raaka-aineena. Tässä kokeessa ollut höyryräjäytetty koivu oli joko uuttama- tonta tai vesipestyä (ksylaanit poistettu). Kokeessa oli kymmenenen Ay-lehmää (5 ensikkoa ja 5 usean kerran poikinutta). Koekaaviona oli kaksi 5 5 tasapai- noitettua latinalaista neliötä. Kontrolliruokinnalla väkirehun vilja oli ohraa. Kauraruokinnalla vilja oli kauraa. Rypsiöljy- ruokinnalla (RSO) vilja oli ohraa kuten kontrolliryhmällä- kin, mutta 0.4 kg ohrasta oli korvattu 0.4 kilolla rypsiöljyllä. Kahdella viimeisellä ruokinnalla 2 kg väkirehun ohrasta oli korvattu joko höyryräjäytetyllä koivulla (Wl) tai vesipes- tyllä höyryräjäytetyllä koivulla (W2). Väkirehussa annettiin lisäksi 1.3 kg soijarouhetta päivässä. Väkirehun kokonais- määrä oli kaikilla ruokinnoilla sama, 8 kg päivässä, koko kokeen ajan. Säilörehua annettiin ad libitum. Kokeessa oli viisi neljän viikon pituista jaksoa. Tulokset on laskettu jak- sojen kahden viimeisen viikon tiedoista. RSO-ruokinnalla säilörehun syönti ja kokonaiskuiva- aineen saanti oli hieman pienempi kuin kontrolliruokinnalla (10.1 ja 17.1 vs. 10,6 ja 17.4 kg ka d 1). Muuntokelpoisen energian saanti RSO-ruokinnalla oli kuitenkin suurempi kuin kontrolliruokinnalla (201 ja 195 MJ/d). Kauraruokin- nalla väkirehun kulutus (6.2 kg ka d 1) oli alempi, koska väkirehua jätettiin tällä ruokinnalla enemmän syömättä kuin muilla ruokinnoilla. Säilörehun syönti oli 11.2 kg ka d 1 ja kuiva-aineen kokonaiskulutus 17.4 kg ka d’ 1 kauraruokin- nalla. Höyryräjäytettyä koivua saaneilla ruokinnoilla säilö- rehun kulutus oli 10.8 (Wl) ja 11.7 kg ka d' 1 (W2) sekä kuiva-aineen kokonaiskulutus vastaavasti 17.8 ja 18.4kg ka d l . Dieetin orgaanisen aineen sulavuus oli merkitsevästi alempi W- (P<0.01) ja kaura-ruokinnoilla (P<0.05) kuin ohraruokinnalla (69.6, 70.9 ja 75.2 %). NDF:n sulavuus oli alin kauraruokinnalla ja korkein ohraruokinnalla (60.7 ja 67.7 %, P<0.05). ADF:n sulavuus W2-ruokinnalla oli alin, ja ero ohraruokintaan oli merkitsevä (60.7 ja 67.1 %, P<0.05). Myös kaura- ja RSO-ruokinnalla oli suuntausta alentuneeseen ADF:n sulavuuteen (62.2 ja 62.9 %). RSO-ruokinnalla oli korkein maitotuotos, 25.5 kg d l , ja ero kaura-, Wl- ja W2-ruokintoihin oli merkitsevä (24.2, 23.3, 22.9 kg d' 1 , P<0.05). Ohraruokinnalla maitotuotos oli 24.6 kg d' 1 (n.s.). Vaikka maidon rasva- ja valkuaispitoi- suuksissa ei ollut tilastollisesti merkitseviä eroja ruokintojen välillä, oli tendenssinä sekä kaura- että RSO-ruokinnalla maidon alentunut valkuaispitoisuus. Maidon ureapitoisuus oli kauraruokinnalla korkein (37.6 mg/100 ml). Ero muihin ryhmiin oli merkitsevä (P<0.01). Sekä kaura että rypsiöljy lisäsivät mm. maitorasvan steariinihapon ja öljyhapon osuutta verrattuna muihin ruokintoihin. Tässä kokeessa 5 % rypsiöljyä väkirehussa vaikutti posi- tiivisesti maitotuotokseen. Kaura- ja ohraruokinnoilla mai- totuotoksessa ei ollut suurta eroa. Sekä RSO että kaura alen- sivat maidon valkuaispitoisuutta. Lignoselluloosatuotteiden (höyryräjäytetyt koivut) sisällyttäminen dieettiin (15 % väkirehuseoksessa) alensi maitotuotosta, eikä niiden rehu- käyttö tässä mitassa ole kannattavaa. 265 Agric. Sei. Finl. 1 (1992)