Maataloustieteellinen A ikakauskirja Vol. 56: 73—82, 1984 Feeding of high producing dairy cows according to rumen undegradable protein requirements in grass silage based diet JOUKO SETÄLÄ 1, LIISA SYRJÄLÄ-QVIST, ESKO POUTIAINEN, MIKKO TUORI and ULLA RIIPINEN Department of Animal Husbandry, University of Helsinki, SF-00710 HELSINKI 71, Finland Abstract. The experiment was performed with 21 Ayshire cows 4—16 weeks post calving. Cows received restricted amounts (according to calculated intake) of unwilted grass silage, preserved with a mixture of acetic acid and formalin and two kilograms of hay/cow/day. A concentrate mixture including dried and propionic acid treated barley and oats together with a mineral-vitamin mixture was given 0.3 kg/kg FCM. During the standardization period (2 weeks) protein feeding of the cows was performed according to the DCP requirements and the diet was supplemented with soybean meal if neces- sary. For the adaptation period (3 weeks) and the comparison period (8 weeks) the cows were divided in 3 equal groups of7 cows (Gl, G2, G3). G 1 had no protein supplement in the diet. The diets of G 2 and G 3 were supplemented correspondingly either with rapeseed meal or formaldehyde treated urea on the basis of the UDP (undegradable feed protein) requirements (G2) and the DCP requirements (G3) of the cows. Efficient protein degradabilities in the total diets during the comparison period varied from 77 to 85 % when the determinations were made with the nylon bag technique.The highest degradabilities were found for the diet of G 3 and the lowest for G 2. Significantly (P < 0.05, 0.01) the highest yields of FCM and milk protein were recorded for Group 2 (G2) in which the cows received protein supplementaccording to their UDP requirements. Using a factorial approach, conversion of protein absorbable in the small intestine to milk protein was calculated to be 66.5 ± 0.8 % when all the cows in three groups were taken into account. Introduction In ruminant feeding, the importance to feed the animal correctly in terms of protein Present address: Valio Finnish Co-operative Dairies’ Association, Research and Development Depart- ment, Kalevankatu 56, P.O. Box 176, SF-00181 HELSINKI 18, Finland requirements of rumen microbes and the ani- mal has, owing to increased knowledge in this field, become one of the most central points. Rumen microbes need a certain level of RDP in the diet for maximal protein synthesis and feed digestion. However, it is very important to feed e.g. a high yielding dairy cow correctly in situations, in which Index words: quality of feed protein, dairy cow 73 JOURNAL OF AGRICULTURAL SCIENCEIN FINLAND https://www.c-info.fi/en/info/?token=WZ-s8BjE3PIPrdvn.WOFdugMVFZ4m4-wg9xnGUg.bpWsfHgKLrCL7XHT50OoBy1_pMinM7xr1zQ4BvRQhySmMAT0hmtL0XohKz85go7cGCZftV2AsKiZSjM6USDa3fwL58TO1JsqPD1eDmF16qLc4x0UJK5iV956HcSkJ-Lv3i2FSETYXcvqzLOJ7dj8o2OhtZH4oJfC8mIIjcwypNjuqxh4eiBai_Ygn--uamRH0h-e4EO6DVZsMYJU-s1TTxKxsTDaC3WKZW2m5unr5CyjH8ryrBoxbfy-6uqHuVJ4Hldun6ceq-serd4-NTo4Sh0meBU the capasity of ruminal protein synthesis should be exceeded in order to meet protein requirement of the cow. The importance of use of relatively undegradable feed protein as a supplement has been illustrated by Kaufmann (1979). Attempts to develop systems to plan feed- ing of ruminants in terms of requirements of ruminally degradable (RDP) and undegrad- able protein (UDP) have been made by many scientists as reviewed by Black et al. (1982). The aim of this experiment was to study the use of one of these systems (ARC, Anon 1980) in planning of diet for high yielding dairy cows in particular feeding conditions. Basal diet of the cows was composed by feeds typical in the feeding of Finnish dairy cattle. As rapeseed meal is one of the most important protein concentrates in Finland, it was chosen to be used as a UDP-source in the experiment. Formaldehyde-treated urea (HCHO-urea) was used as a RDP-source (fed on the basis of digestible crude protein, DCP) because it was suggested to be a better NPN-source than an ordinary urea for high yielding dairy cows (Setälä and Syrjälä- Qvist 1982b). Experimental procedures Animals and diets Milk production trial was made with 21 Ayshire cows, which were taken for the trial in two blocks about 4 weeks after calving. The parturition was the second for all the cows. Each cow had an experimental period of 13 weeks including standardization period, 2 weeks adaptation period, 3 weeks comparison period, 8 weeks. The cows were fed individually twice a day and they received 2.0 kg hay/cow/d and grass silage according to calculated DM intake during the experiment. Hay was field- dried and baled and grass silage was un- wilted, preserved with Viher acid (20 % formaldehyde, 30 °7o acetic acid; chemical composition, see Table 1) using 5 1 pre- Table 1. Chemical composition and feeding value of the feeds in the experiment. Hay Grass Concentrate Rapeseed Soybean HCHO- silage' meal mealmix urea Dry matter, % 86.1 + 0.7 22.3 ± 0.7 % in dry matter Ash 8.0 ± 0.3 7.5 ± 0.2 Crude protein 11.1 ± 0.2 14.9 ± 0.4 Crude fibre 34.6 ± 0.4 32.1 ± 0.7 Ether extracts 2.6 + 0.1 6.3 + 0.3 N-free valuable 43.5 ± 0.6 38.6 + 1.2 nutrients g DCP/kg DM 71.1 ± 3.1 104.6 ± 5.8 f.u./kg DM 2 0.47 ± 0.04 0.73 ±O.ll MJ ME/kg DM 8.7 ± 0.1 9.3 ± 0.2 Degradability, %4 Organic matter 48.9 + 2.0 61.4 ± 2.3 Crude protein 63.1 + 1.8 79.6 ± 2.6 84.1 ± 0.5 89.0 ± 1.6 83.5 ± 1.3 99.3 5.3 ± 0.4 7.7 ± 0.2 6.0 ± 0.7 12.0 ± 0.2 36.8 ± 0.4 51.5 + 0.5 46.33 9.1 ± 0.3 15.2 ± 0.3 11.3 ± 0.9 3.9 ± 0.1 4.0 ± 0.1 1.9 ± 0.5 69.6 ± 0.5 36.3 ± 0.5 29.2 ± 1.6 91.2 ± 1.2301.6 ± 3.0463.8 + 4.3 1.08 ± 0.030.86 ± 0.071.09 ± 0.03 12.4 ± 0.110.5 ± 0.112.4 ± 0.1 77.3 ± 1.3 48.5 ± 1.5 86.8 ± 1.1 49.1 ± 2.5 60.0 60.0 100.0 pH 3.8, % in DM: soluble sugars 3.2, lactic acid 7.6, acetic acid 1.7, propionic acid 0.06 % in total N: NH3 -N 5.9, water soluble N 52.9 2 f.u. = feed unit 3 N-% 4 only one determination for soybean meal; for the others 8 determinations/feed 74 servative/1000 kg fodder. Feeding of the cows during different periods was performed as follows: Grass silage and hay were sampled every day during the standardization period. Daily samples were bulked into one sample/week. Standardization period Comparison period Group 1 Group 2 Group 3 Group 1 Group 2 Group 3 Hay, kg/cow/d 2.0 2.0 2.0 2.0 2.0 2.0 Grass silage 1 re- re- re- re- re- re- strict, strict. strict. strict. strict. strict. Concentrates, kg/kg 0.3 0.3 0.3 0.3 0.3 0.3 4 % milk 2 Soybean meal DCP> DCP' DCP' Rapeseed meal UDP4 HCHO-urea5 DCP' According to calculated DM intake (Salo et ai. 1982) Propionic acid preserved or dried (50 % : 50 %) mixture of barley and oats (1:1) 98 %, vitamin-mineral mixture 2.0 % (g/kg:Ca 175, P 80, Na 95, Mg 50, Se 0.01) 3 According to DCP requirements of the cows (calculations, see later in the text) 4 According to UDP requirements of the cows (calculations, see later in the text) 5 1.5 % HCHO, see Setälä and Syrjälä-Qvist (1982 a) During the standardization period the cows received soybean meal as a protein supplement according to their DCP require- ments. After this period, the cows were divided in three as equal as possible groups (7 cows/group) according to their milk yields and liveweight. The cows in Groups 2 and 3 were gradually accustomed to their new feeds, rapeseed meal or HCHO-urea, respec- tively. At the same time soybean was grad- ually withdrawn from the diet of the cows in Groups 1, 2 and 3. The cows were weighed at the beginning of each period, at the end of the experiment and every fourth week during the comparison period. Sampling and analyses Milk produced was weighed and recorded for each cow at every milking. A milk sample for each cow was taken from the milk of two days so that the sample was composed by proportional amounts of milk produced at each milking. Fat and protein contents of the samples were analyzed with the infrared analyzer (IRMA). Concentrates were sampled always while making the mixture. During the adaptation and comparison periods roughage and concentrates were sampled every second week so that the samples would represent the feeds which were going to be fed during the next 2 weeks. Samples of soybean meal were taken every day preparing the feeds for each cow during the standardization period. Rapeseed meal and HCHO-urea were sampled in a similar way as grain concentrates during the adaptation and comparison periods. Feed refusals were sampled every day, stored at + 4°C and bulked into one sample/cow/two weeks. DM contents of the samples were deter- mined in an oven at + 103—h 105°C and samples for feed analyses were dried in vacuum (except urea) oven at +5O°C. Be- cause of the loss of volatile substances in DM determination, DM content of the silages was corrected according to the volatile fatty acids in silage as described by Setälä et ai. (1979). Chemical composition of the feeds and feed refusals was analyzed according to the 75 standard methods. The quality of the grass silage (pH, sugars, lactic acid, NH 3 -N, VFA, water-soluble N) was determined as described by Setälä et al. (1979). Degradability of feed proteins in the rumen was determined during the compari- son period using the nylon bag technique. Feed samples, taken as described earlier in this chapter, were incubated in the rumen of a sheep receiving the same feeds which were given to the cows. The feeding level and the proportions of feeds in the diet were also the same as in the diets of the cows. The incuba- tion procedure followed in the study has been described in details by Setälä (1983 a). Values for efficient protein degradabilities were obtained for each period of two weeks and the feeding of the cows was planned ac- cording to these results. Our unpublished results with urease en- zyme in vitro showed that HCHO-urea seemed to be completely degradable in the rumen. Feeding of the cows was calculated and adjusted at the beginning of each week. Calculations and statistical procedures The energy and digestible crude protein required for maintenance and production were calculated as described by Setälä and Syrjälä-Qvist (1982 b). Maintenance re- quirements for energy and protein were 4.0 f.f.u. per 500 kg liveweight and 75 g DCP per maintenance f.f.u. (Breirem 1969). The energy requirement for liveweight change was 2 f.f.u./kg liveweight change. Energy and protein requirements for milk produc- tion were 0.4 f.u./kg FCM and 57 g DCP/kg FCM, respectively. The amount of the degradable (RDP) and the undegradable feed protein (UDP) in the feeds was evaluated so that the effect of the feeding level (changes in outflow rates) was taken into account (see Setälä 1983 a). The RDP and UDP intake of the cows was calcu- lated using these values. The UDP require- ment of the cows was calculated according to the ARC system (Anon 1980). However, the microbial protein synthesis was adjusted for the grass silage diet, and the value used for the efficiency of the synthesis was 25 g N/kg OMAppFR (organic matter apparently fer- mented in the rumen) (Muhlbach & Kauf- mann 1979, Armstrong 1980). Although in the ARC system the absorption of the pro- tein in the small intestine is given as an apparent absorption, in the calculations metabolic nitrogen excretion was taken into account as a requirement according to Bur- roughs et al. (1975). On the basis of UDP deficiency the diet of the cows in Group 2 was supplemented with rapeseed meal. Recalculations for the standardization peri- od were based on the first determinations of degradability made from feeds for the com- parison period. The yield data were tested by two-way analysis of covariance, where the regression variable was the yield of the standardization period and the treatments were used as factors. The differences between treatment means were tested by the Tukey test (Steel and Torrie 1960). Results and discussion Feed intake and milk yield During the comparison period the average relationship (calculated on DM basis) be- tween concentrates and forage was 51.6 : 48.4 in the experiment (Table 2). The cor- responding values for Groups 1,2 and 3 were 51.9 : 48.1, 53.4 : 46.6 and 49.6 : 50.4, respectively. The cows did not eat willingly the feeds, especially concentrates and silage, and re- fusals were left in all three groups through- out the experiment. Low palatability of grass silage was caused by relatively high bulki- ness, especially at the beginning of the trial. However, reasons for poor palatability of concentrates remained unclear, although results of this kind were also reported by Lindell (1982), when the cows were fed in a 76 Table 2. Average feed consumption of the cows during the standardization and comparison period (G = group, RSM = rapeseed meal, SBM = soybean meal) DM intake/cow/day Hay Grass Concen- RSM SBM HCHO- Total silage trate urea mix Standardization period G 1, DCP/SBM 1.3 4.4 7.1 0.7 13.5 G 2, DCP/SBM 1.3 4.9 6.5 0.6 13.3 G 3, DCP/SBM 1.1 5.7 8.0 0.8 15.7 Comparison period 9—12 weeks from calving G 1, no supplement 1.3 5.2 7.4 13.9 G 2, UDP/RSM 1.3 5.8 7.8 0.7 15.6 G 3, DCP/HCHO-urea 1.2 5.7 7.0 0.14 14.0 13—16 weeks from calving G 1, no supplement 1.3 5.4 7.0 13.7 G 2, UDP/RSM 1.3 6.0 7.6 0.4 15.3 G 3, DCP/HCHO-urea 1.4 5.2 6.0 0.096 12.8 Table 3. Average daily milk, fat, and protein yields, and the composition of the milk of the cows in the experiment (G, RSM, SBM, see Table 2) kg/cow/d % in milk Milk FCM Fat Protein Fat Protein Standardization period G 1, DCP/SBM 25.6 27.6 1.16 0.73 4.53 2.87 G 2, DCP/SBM 24.8 28.4 1.23 0.70 4.99 2.83 G 3, DCP/SBM 26.7 27.3 1.21 0.78 4.47 2.93 Comparison period 9—12 weeks from calving G 1, no supplement 22.8' 24.3" I.ol' 0.67' 4.40 2.96 G 2, UDP/RSM 25.2" 26.4"' 1.09 c 0.77d 4.36 3.08 G 3, DCP/HCHO-urea 21.8' 22.4" 0.91" 0.65' 4.21 3.04 13—16 weeks from calving G 1, no supplement 20.6' 22.4»' 0.94' 0.623 ' 4.55 3.03 G 2, UDP/RSM 23.4"" 25.3 b' 1.06' 0.74" 4.56 3.19 G 3, DCP/HCHO-urea 18.4M 19.4" 0.80" 0.57 b' 4.40 3.18 , P < 0.05, means between groups differed significantly , P < 0.01, means between groups differed significantly restrictive way. Waldern (1973) also sug- gested that rapeseed meal might be less pala- table than soybean meal, but problems in palatability have not been observed with acid-preserved grains (Pohjanheimo and Ettala 1971) or HCHO-urea (Setälä and Syrjälä-Qvist 1982 b). The experiment did not start until 4 weeks after calvings of the cows, but the average yields of FCM were relatively high being 28—30 kg FCM/cow/day at thebeginning of the standardization period. Cows in Group 2 produced significantly (P < 0.05, 0.01) more FCM than cows in Groups 1 or 3 (Table 3). Moreover, yield of protein (P < 0.01) was also significantly 77 higher in Group 2, although there were not significant differences in milk fat-°/o or protein -% between groups. The poorest yields were reported for Group 3 receiving HCHO-urea as a supple- ment of the basal diet. According to Setälä and Syrjälä-Qvist (1982 b) HCHO-urea gave higher milk yields than an ordinary urea especially when cows produced more than 15 kg FCM/day. Moreover, they also sug- gested (Setälä and Syrjälä-Qvist 1982 a) that HCHO-urea could successfully be used as a supplement even in diets having crude protein content up to 15—16 % in DM e.g. in the feeding of high-producing dairy cows fed on the basis of DCP. However, the yield data of Group 3 cannot directly be compared with the data of the other groups. In Group 3, 6 of the seven cows suffered from a severe mastitis during the experiment. In Groups 1 and 2 mastitis was observed in 2 and 1 cows, respectively. High mastitis frequency in Group 3 was not caused by feeding. Relatively high cell counts were found afterwards in the milk of the cows in this group already in the standardiza- tion period. However, coincidentally most of the cows in Group 3 had mastitis although they were divided in groups on the basis of other factors. The cows received less energy and protein (Table 4) than they required according to cal- culated standards and this was mainly caused by the low palatability of concentrates. Based on feed units the cows received energy if expressed as per cent of the requirement as follows: Standardization period, Group 1, 2 and 3, 81, 76 and 90; Comparison period, Groups 1,2 and 3, 92, 96 and 95 respectively. The corresponding weight losses as an average in grams/cow/day were -1071, -990 and -702 for the standardization period; -28, -237 and -330 for the comparison period. If the amount of mobilized body energy (weight loss) is increased the need of ab- sorbed protein in the tissues is also increased so that a balance between energy and protein is obtained in the tissues. orskov et al. (1981) suggested that in the situations of energy undernutrition the UDP supplemen- tation is advisable. According to Lee et al. (1974), Oldham et al. (1982) and Tyrrell et al. (1982) UDP-supplementation of the diet causes an increased tissue catabolism due to increased secretion of growth hor- mone. However, in the case of severe under- nutrition UDP-supplementation could lead the cow to ketosis (Webster et al. 1982). Oldham et al. (1979) reported an increase in the yields of milk, fat and protein when Table 4. Average intake of digestible crude protein, ruminally degradable or undegradable protein in ratio to the requirements of the cows (G = group) Standardization period Comparison period 9—12 weeks 13—16 weeks G 1 G 2 G3 G 1 G 2 G3 G 1 G 2 G3 g DCP/kg FCM 45.0 41.1 51.7 41.2 47.9 56.4 74 83 95 46.1 49.8 56.9 % of requirement 79 73 88 81 86 96 1531 1750 1706RDP intake, g/d 1481 1456 1731 1456 1694 1887 133 144 174 319 512 369 % of requirement 132 127 150 134 141 162 325 425 312UDP intake, g/d1 644 575 706 % of requirement 87 81 105 75 81 76 13.5 14.2 15.8 58 80 69 12.7 14.1 16.1% crude protein in 15.7 15.3 15.5 DM of total diet % RDP in total protein 69.7 71.7 71.0 82.0 76.8 83.6 82.5 80.4 84.5 RDP = nominally degradable protein (N x 6.25) UDP = nominally undegradable protein (N x 6.25) changes in liveweight were taken into account as in ANON (1980) 78 urea was substituted in the diet by fish meal. The highest yields of milk and protein were obtained when the ratio of RDP;UDP was between I.B2t5. In the present study the average ratio of RDP:UDP was 3.8 ± 0.4. Castle et al. (1983) found an increase in milk yield and in protein content of milk when silage diets were supplemented with va- rious levels of protein concentrates. Howev- er, Oldham et al. (1982) did not notice changes in milk composition of the cows, when formaldehyde treated and untreated protein concentrates were compared in the diet. According to Forster et al. (1983) the effect of UDP supplement on milk composi- tion is dependent on energy status of the cows. When cows were fed in a restricted way with hay-corn silage based diets, UDP supplementation increased milk production, decreased protein-% in milk and had no ef- fect on fat or lactose per cent in milk. When protein amount in the total diet was reduced using protected protein on similar energy level, changes in milk composition of the cows were not observed (Kaufmann et ai. 1982). Protein metabolism of the cows The cows managed well with relatively low crude protein levels in the total diet during the comparison period. These results agree with the factorial calculations of Setälä (1983 b) when the feeding of the cows was planned on the basis of UDP requirements. Because the cows did not eat all the amount of the feeds, they did receive less UDP than they would have required. Intake of RDP was higher than requirements and this was mainly caused by the high degrada- bility of silage protein. Therefore the degra- dability of crude protein in the total diets was relatively high, varying from 70 to 85 %. In the present study microbial protein synthesis was evaluated to be 25 g N/kg OMAppFR. The efficiency of synthesis was assumed to be the same in all diets although according to Armstrong (1980) and MeAllan and Smith (1983) the efficiency of synthesis might be improved in roughage based diets by protein supplementation. The value chosen for microbial protein synthesis ap- peared to be slightly higher or lower than suggested in the recent reviews of Thomas (1982) or Miller (1982), respectively. According to calculations microbial pro- tein covered about 63, or 75 % of the total amount of absorbable protein in the stan- dardization period or in the comparison period, respectively (Table 5). Similar re- Table 5. Nitrogen utilization of the cows Standardization Comparison period penod 9—12 weeks 13—16 weeks Gl G 2 G 3 Gl G 2 G 3 Gl G 2 G 3 Protein for the cow microbial, g/d* 1040 1011 1200 1115 1236 1110 1131 1255 1033 UDP, g/d 644 575 706 319 512 369 325 425 312 total, g/d 1684 1586 1906 1434 1748 1479 1456 1680 1345 absorbed 1179 1110 1334 1003 1223 1035 1019 1176 941 protein, g/d** Absorbed protein/ 0.66 0.67 0.62 0.72 0.67 0.67 0.65 0.67 0.65 milk protein*** * Amino-N 80 % in total microbial N; synthesis calculated on the basis of OM apparently fermented in the rumen ** Absorbtion 70 % *** Maintenance requirements are taken into account. 79 suits have been reported by Overend and Armstrong (1982) and Merchen and Satter (1983) although the proportion of microbial protein in the total protein in small intestine may vary if the amount of concentrates in the diet is changed (Teller et al. 1979). Utilization of absorbed protein into milk protein was not much different in different diets, the average value for utilization being 66.5 ± 0.8 °/o. In spite of higher milk yield of the cows, there were not great differences in utilization of absorbed protein when the standardiza- tion period is compared with the comparison period. Besides of differences in milk yield and protein feeding (DCP-UDP), there were also different protein sources in the diets of these two periods. Although it was suggested by Varvikko et ai. (1983) that amino acid profile in undegradable protein could be more easily changed by rumen fermentations in rapeseed meal than in soybean meal, this was not supported at least in the present study when protein utilization for the stan- dardization period was obtained with recal- culations. Oldham (1978) suggested that absorbed protein was utilized with an efficiency of 65—85 °7o for protein production, leaving 15—35 °7o of amino acids to serve as precur- sors for other purposes, for instance in glu- coneogenesis. Efficiency tended to increase with higher energy supply (see also Rulquin 1982), which could explain the difference in utilization of protein between Group 3 (Stan- dardization period) and Group 1 (Compari- son period). Based on the other experimental approach than in the previous study, Oldham (1979) suggested the value of 67—72 °7o for protein utilization. In the review of Broster and Oldham (1981) they suggested that in most situations the value of 70 °7o could De used for both feed and microbial protein when apparent ab- sorption is calculated. However, Storm and ORSKOV (1982) reported that the efficiency of utilization of absorbed amino acid N from microbial protein might be about 80 %, e.g. higher than used in the present study ac- cording to ARC-system. On the other hand, Broster and Oldham (1981) also concluded that the protein requirement for the cow pro- ducing 25—30 kg milk/day is 14.0—14.5 °/o crude protein in DM of the total diet which is in agreement with the results in the present trial. In situations, in which undernutrition of energy and protein are used, there are generally problems in the fertility of the cows. In the present study these problems were not observed. There were before the ex- periment 1.57, 1.60 and 1.40 services/ conception for the cows in Groups 1, 2 and 3, whereas during the experiment 1.30, 1.80 and 1.50 services, respectively. However, it must be pointed out that the present study lasted only for 13 weeks which might be too short period for such observations. In conclusions, it is possible to feed the dairy cow according to the requirements of different protein fractions, e.g. RDP and UDP. If fed in this way, crude protein level in the diet is lower compared to the diet planned on the basis of DCP. 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Ms received March 20, 1984 SELOSTUS Korkeatuottoisten lypsylehmien ruokinta pötsissä hajoamattoman rehuvalkuaisen mukaan nurmisäilörehuun perustuvalla ruokinnalla Jouko Setälä1 , Liisa Syrjälä-Qvist, Esko Poutiainen, Mikko Tuori ja Ulla Riipinen Helsingin yliopisto, Kotieläintieteen laitos, 00710 Helsinki 71 Tutkimus suoritettiin 21 Ayrshire-lehmällä, jotka tuli- vat kokeeseen keskimäärin 4 viikkoa poikimisen jäl- keen. Kokeen kestoaika oli 13 viikkoa, josta 2 viikkoa oli vakiointikautta ja 3 sekä 8 viikkoa vastaavasti siirto- ja vertailukautta. Lehmät saivat perusväkirehuseosta (kuivattua tai pro- pionihapolla säilöttyä ohraa tai kauraa sekä kivennäis- seosta) 0,3 kg/4%-maitokilo sekä 2,0 kiloa heinää/ lehmä/d. Säilörehua lehmille annettiin lasketun syönti- kyvyn mukaan. Vakiointikaudella lehmien ruokintaa täydennettiin tarvittaessa soijarouheella ja täydennys- tarve arvioitiin lehmien sulavan raakavalkuaistarpeen 1 Valion tutkimus- ja tuotekehittelyosasto, Kalevankatu 56 B, 00180 Helsinki 18 perusteella. Vakiointikauden jälkeen lehmät jaettiin kol- meen (Rl, R2, R3) seitsemän lehmän ryhmään, joista Rl ei saanut vertailukaudella valkuaistäydennystä, mut- ta R2:n jaR3:n ruokintaa täydennettiinvastaavasti ryp- sirouheella tai formaldehydiurealla. Valkuaistäyden- nyksen tarve R2:lle laskettiin lehmien pötsissä hajoa- mattoman rehuproteiinin tarpeen mukaan ja R3:lle sula- van raakavalkuaistarpeen mukaan. Ryhmän 2 lehmien 4%-maitotuotos ja valkuaistuotos olivat merkitsevästi (P < 0,05, 0,01) suurimmat vertai- lukauden aikana. Faktoriaalista laskentatekniikkaa käyttäen lehmien ohutsuolesta imeytyvän proteiinin hy- väksikäyttö maidon proteiinin muodostukseen oli 66,5 ± 0,8 %. Eri ruokintojen välillä ei tässä suhteessa ollut selviä eroja. 82