Maataloustieteellinen Aikakauskirja Vol. 57: 139—146, 1985 Factors affecting in sacco degradation of dry matter and crude protein in grass silage JOUKO SETÄLÄ 1 , ALEM TESFA2 , AINO KAURAMAA 1 and ESKO POUTIAINEN 3 1 Valio Finnish Co-operative Dairies’ Association, Research and Development Department, Kalevankatu 56, P.O. Box 176, SF-00181 Helsinki, Finland 2 University of Helsinki, Department of Animal Husbandry, SF-00710 Helsinki, Finland 3 Agricultural Research Center, 31600 Jokioinen, Finland Abstract. The degradability of dry matter and crude protein was studied in 96 grass si- lages, which were collected from practical farms in different parts of Finland. The degradabi- lities were determined by the nylon bag technique in sheep on a grass silage and hay (50 : 50 on DM basis) -based diet. Among chemical components the N-freeextracts increased, and the crude fibre decreased the dry matter degradation in the rumen. The correlation between the end-products from silage fermentation and the dry matter degradability was generally negative. The level of the crude protein degradability was significantly increased when the crude protein content in the silage DM was increased. The amount of N03 in the silage DM had a similar effect. The rate of crude protein degradation was regulated mainly by the proteolysis in the silage, e.g. the amounts of NH, and especially water soluble N in the total N of silage. Crude fibre tended to protect crude protein against ruminal digestion. Introduction Grass is the most potential feed with reasonably high energy and protein contents, which can successfully be grown and harvest- ed for silage also in the northern countries. Factors affecting the energy and protein value of grass silage have intensively been studied in many countries. Some of the experimental results in Finland have shortly been reviewed by StiAi a (1984). The increase in the knowledge concerning the protein metabolism and requirements of a ruminant has drawn attention to the im- portance of the feed energy and protein de- gradability in the rumen. This regards also grass silage. The aim of thepresent study was to investigate factors affecting ruminal de- gradability of the dry matter and crude pro- tein of the silage. In order to receive the most realistic data, experimental material was col- lected from practical farms. 139 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=Ye_e5nvHQno0ZZUp.GrW2ytjxFlqcBzH1tB-lew.NA9DjMsp-x_9YaZpeiRReCp-dTZkzYIE3XbLBalLaOU6xXigpGnl3Rb9dGdtCmlvOIlStDEkfeIPM5dxl10sA6J7T8kH5ySa0SK-_WlmQwiLCPUa55O0me4p4mEEQRxYxMEDFtC_vwuK8cZPV8KLWwlLwyvJ69xx1tyeQn5Gudrj8p-mU0HaqSGR-xpUe3XA0EYv8YkCpE0m6Ba_Uwn2JhtXr9py4LMiiqTuI8xN_0o063ZG6Q Material and methods The material included 96 grass silage sam- ples which were collected from practical farms in 1981 in different parts of Finland. The si- lages were unwilted and preserved mainly with the AIV-solutions (Valio, Finnish Co-opera- tiveDairies’ Association), which contain either formic acid (80 %) and orthophosphoric acid (2 %) as AIV 11, or formic acid (27 %) and HCI (22 °/o) as AIV I. AIV II and AIV I were used in 76.5 % and 9.2 % of the silages, res- pectively. A formaldehyde containing additi- ve (Viher-solution, 55 °/o formalin, 30 % ace- tic acid, Farmos Group Ltd) was used in 14.3 % of the silages. The silage samples we- re immediately frozen on a farm and they were sent to the laboratory in insulated boxes. The DM content of the silage was calculated after drying at + 80 °C overnight. For chem- ical analyses the samples were dried in a vacuum at + 50 °C for 24 hours, and the dried sample for the analyses was milled through a 1.0 mm o screen. Water soluble N was ana- lyzed after the fresh sample had been extracted in distilled water as described by Huida (1973). The chemical composition of the silages was analyzed by the standard methods. The silage pH and NH 3 were measured in the effluent pressed from the silage (Heikonen et al. 1979). The water soluble N (WSN) was ana- lyzed by the Kjeldahl method. The reducing sugars were determined according to Somogyi (1945) and the lactic acid and volatile fatty acids using enzymatic (Anon 1980) and gas chromatographic methods, respectively. The analyses of NG 3 were made by the ionselec- tive electrode. The degradabilities of dry matter (DM) and crude protein (CP) were determined by the ny- lon bag technique (Mehrez and orskov 1977) as explained by Setälä (1983). The tests were made with two sheep on a hay and grass silage diet (1:1 on DM basis). Fresh silage was chopped to the length of less than 0.5 cm, and 5 grams of silage dry matter was placed in each bag. Five bags were incubated in the rumen at the same time. There was a grass silage sample in four bags and a standard hay sam- ple in one bag. Only one replicate for silage/ incubationperiod was used and for each silage the incubation was performed during one day. Grass silage samples were incubated for 2,5, 18, and 24 hours. A standard hay sample was always incubated for 24 hours and the degra- dability of dry matter in the hay was used for controlling ruminal fermentations during the incubations. The degradability of dry matter without crude protein (N-free DM) was also calculated in order to exclude the effect of the crude pro- tein degradation on the DM degradability. The degradability of N-free DM was calcu- lated as follows: Degradability - x * gDMinc)]-[gDMre .-(0.01 X CP res % X gDMJ X 100 [gDMinc (0.01 X CPinc «Vo X gDMinc)] DM inc = amount of DM incubated (correspondingly CPinc) DM res = amount of DM left in the bag after incubation (correspondingly CP res) Results and discussion Chemical composition and quality of the silages The average quality data of the silages showed that the quality of the silages accord- ing to e.g. Heikonen et ai. (1979) was rela- tively good (Table 1). There were, however, great variations between silages if the contents of the reducing sugars and butyric acid are considered. The average crude protein content was lower and the crude fibre content higher 140 than the corresponding values in all the silages analyzed in Finland 1981. The correlations between different chemi- cal components (Table 2) should be regarded as quite typical of grass silages. A high ash content (soil contamination) increased the pH, NHj (deamination), and butyric acid in the si- lage. Moreover, high pH increased proteoly- sis, deamination (NH 3 , WSN) and butyrate fermentation. The latter was closely connected to the yields of propionic acid. If it is assumed that a low sugar content of the silage is a sign of a vigorous fermentation in the silo, it could be concluded that a vigorous fermentation in- creased proteolysis and deamination in the si- lages. Part of these processes could be ex- plained by a Clostridia fermentation (Ohshi- ma and McDonald 1978) but it must be em- phasized that lactic acid fermentation also cor- related negatively with the content of the re- ducing sugars in the present study. Comparison between the degradability of dry matter and crude protein The dry matter and crude protein in the si- lages degraded at different rates in the rumen Table 1. The average chemical composition of the si- lages in the present study and in Finland 1981. Present study In Finland x s.d. 1981 N 96 19596 Dry matter, % 20.3 2.6 21.5 g/kg DM Ash 78 27 Crude protein 149 28 156 Crude fibre 290 28 277 Reducing sugars 51 51 N-free extracts' 482 40 g/kg Lactic acid 10 5 Lactic +acetic acids 18 6 Butyric acid 0.5 1.3 Propionic acid 0.05 0.03 pH 3.9 0.3 3.9 2 WSN, % in total N 49.3 12.2 NH3 , g/1 pressed juice 0.4 0.3 0.4 2 NOj, g/1 pressed juice 0.5 0.3 N-free extracts = 100 (Ash- % + Crude protein-% + Crude fibre-%) 2 N = 13037 Table 2. Correlations between the chemical components of the silages (n = 96). CF = crude fibre, CP = crude protein, Nfe = N-free extracts, WSN = water soluble N DM Ash CF CP Nfe Sugars pH NH, NQ 3 Lactic Butyric Lactic + Pro- Acetic pionic DM Ash 0.070 CF —0.221» —0.219» CP —0.257» 0.006 —0.220* Nfe 0.293»* —0.500*»» —0.394*»» —0.557»»» Sugars 0.300** —0.179 —0.433»»» —0.254* 0.598»»* pH —0.034 0.241* 0.157 0.376*»» —0.535»»» —0.196 NH 3 —0.070 0.300» 0.183 0.376*»» —0.587»»* —0.416»»* 0.703*»* N0 3 0.122 0.150 —0.155 0.365*»* —0.253* —0.021 —0.007 0.084 Lactic -0.023 0.157 0.133 -0.169 -0.068 —0.417*»» -0.334»»* 0.006 -0.036 Butyric 0.147 0.407»*» 0.010 0.183 —0.401*»» —0.201* 0.632»*» 0.760»»* 0.133 —0.134 Läctic -f- • Acetic 0.045 0.186 0.224* -0.109 -0.195 -0.436»»» 0.064 0.341»»» -0.063 0.552»»» 0.167 Propionic -0.102 -0.044 0.112 0.184 -0.176 -0.115 0.258* 0.450»»* -0.008 -0.002 0.448**» 0.284» WSN -0.045 0.007 0.078 0.056 -0.100 0.007 0.172 o.4oß*** 0.208» -0.028 0.300* 0.020 0.061 • P <0.05, *• P < 0,01, *»* P < 0.001 141 (Table 3, Fig. 1). Especially during the first five hours the difference was very clear. The degradabilities for DM varied from 10 to 42 °7o and for crude protein from 15 to 75 °7o, respectively (Fig. 1). The variation in the crude protein degradability was much more exten- Table 3. Degradability-% of silage DM, N-free DM, and crude protein in sacco (96 silages). sive than the variation in the DM degradabi- lity. This can have a great effect on the utili- zation of ruminally degradable silage N. If it is assumed that the organic matter of silage is fermented at a similar rate as the silage DM, and the degradability of DM and crude pro- Fig. I. Comparison between the DM and crude protein degradabilities (from 2to 24 hours) of the silages. Incubation Dry matter N-free DM Crude protein period hours “I ~ I “ ~~ T~x s.d. x s.d. x s.d. 2 29.3 5.6 22.3 5.6 46.5 11.3 5 35.6 5.7 27.4 5.8 52.5 10.4 18 57.6 7.0 45.9 5.9 77.1 6.1 24 64.4 7.1 51.7 5.8 79.5 5.1 142 tein are correspondingly 42 °/o and 75 %, the ratio of the ruminally degradable N (RDN) and fermentable organic matter (OMF) would be 4.6 g RDN/100 g OMF in the present ma- terial. If it is assumed that the efficiency of the utilization of RDN for microbial protein synthesis is 100 %, this value is almost twice as great as suggested for an appropriate value according to the average microbial protein synthesis (2.5 g microbial N/100 g OMF) in grass silage -based diets (Miller 1982, Tho- mas 1982). Factors affecting the degradability of dry matter The most important factors affecting the DM and N-free DM degradability were the contents of the crude fibre and N-free extracts in the silage DM (Table 4). The N-free extracts include hemicellulose and sugars which can more rapidly and easily be degraded in the ru- men than cellulose fraction in crude fibre. On the other hand, crude fibre including cellulose and lignin seemed to protect the silage DM against ruminal digestion. Regarding the correlations it must be em- phasized, that although they were significant (df 94), they accounted only for a very small proportion of the variance. However, the negative correlations between the degradabi- lity of N-free DM and pH (and NH 3 ) or the degradability of DM and lactic + acetic acids might indicate that the highest degradability of DM is obtained when the silage is well pre- served without vigorous fermentation and made from a relatively young grass having a low crude fibre content in DM. A decrease in the organic matter degradability in an inten- sively fermented silage was also demonstrated by Cation et al. (1982). The content of crude protein in the DM af- fected significantly the ruminal degradation rate and level of N-free DM and DM, because crude protein was rapidly and to a great ex- tent degraded in the rumen (see Table 3). Table 4. Correlations between the chemical components of the silages and the degradability-% of DM, N-free DM and crude protein. CF, CP, Nfe, WSN, see Table 2. DM Ash CF CP Nfe Sugars pH NH 3 NO, Lactic Butyric Lactic + Pro- WSN Acetic pionic DM-dg 2 hr 0.101 —0.130 —o.379*** 0.030 0.328** 0.527*** —0.095 —0.156 0.001 —0.190 —O.lll —0.247* —0.077 —0.002 5 hr 0.100 0.008 —o.39o*** —0.055 0.314** 0.370*** —O.OBl —0.078 0.028 —0.054 0.019 —0.125 —0.063 0.167 18 hr —0.094 —O.OOl —o.s23*** 0.383*** 0.106 0.154 —0.056 —0.105 0.043 —0.050 —0.006 —0.202* —0.055 —0.051 24 h —0.078 —0.026 —o.43B*** 0.409*** 0.031 0.217* —0.003 —O.lOB 0.208* —O.lBO 0.014 —o.334*** —0.041 —0.087 N-free DM-dg 2 hr 0.199 —0.214 —o.34o*** —0.294** 0.527*** 0.571*** —0.238** —0.319** —0.125 —0.114 —0.196 —O.lBB —0.151 —0.140 5 hi 0.219* 0.014 —o.3so*** —o.376*** o.sll*** 0.432**» —0.212* —0.246* —0.099 0.018 —0.074 —O.OBO —0.132 0.017 18 hr 0.053 —0.020 —o.4Bl*** —0.019 0.375*** 0.297** —0.211* —0.276** —0.091 0.026 —0.077 —0.174 —0.140 —0.126 24 hr 0.100 —0.098 —o.364*** —O.OlB 0.337*** 0.296** —0.269** —o.37B*** 0.087 —0.068 —0.176 —o.262*** —0.120 —0.200* CP-dg 2hr —0.138 —0.036 0.060 0.245* —0.194 0.050 0.146 0.220* 0.141 —0.085 0.123 —0.105 0.094 0.428*** 5 hr —0.185 —0.054 0.096 0.193 —0.174 0.010 0.095 0.270* 0.133 —0.079 0.148 —0.057 0.075 0.521*** 18 hr —0.232* 0.011 —0.264** 0.506*** —0.176 —0.040 0.043 0.083 0.133 —0.090 0.033 —0.051 0.068 0.201* 24 hr —0.056 —0.083 —0.313** 0.595*** —0.154 —0.002 0.046 0.104 0.325** —O.OBB 0.018 —0.044 0.108 0.185 * P <0.05, ** P < 0.01, **» P < 0.001 143 144 Factors affecting the degradability of crude protein The crude protein content affected also clearly the degradation of crude protein. The effect was especially clear if the level of the degradability (after 18—24 hours) was con- sidered (also Pekkarinen et al. 1983). As similar results were obtained with the N0 3 content of the silages it could be suggested that the crude protein content of the silages on the farm was increased by N-fertilization which increases the level of the crude protein degra- dability (Pekkarinen et al. 1983). It seems obvious that, regarding protein degradabili- ty, more attention and research should be paid to the use of N-fertilizers for grass. However, the rate of the degradation was significantly dependent on the proportions of the NH 3 and especially WSN in silage (see Table 5), e.g. on the extent of proteolysis and hence on the quality of silage (also Brett et al. 1981, Catton et al. 1982). It is known that Clostridia (butyrate fermentation) cause an extensive proteolysis (deamination and de- carboxylation) in the silage (Ohshima and McDonald 1978). However, proteolysis can also be caused by heterofermentative lactic acid bacteria, and although this may take place to a limited extend (McDonald 1982), silage which is almost continuously fermented cannot therefore be regarded as a good silage. Moreover, the degradability of silage energy (DM, organic matter) is decreased in an in- tensively fermented silage. Crude fibre tended to protect crude protein against digestive processes in the rumen. However, although this is most obviously true, it must be pointed out that while grass matures, the crude fibre content increases and the crude protein content decreases, and this interaction may affect correlation. Moreover, because the ADF-fraction was not deter- mined, it is difficult to say how much ADF- bound and hence poorly degradable nitrogen was included in the crude fibre fraction. One can only speculate that the proportion of ADF-N was low because there were not many vigorously fermented silages which may con- tain larger amounts of ADF-N (Goering et al. 1972, 1973). Table 5. Degradability-% of DM, N-free DM, and crude protein in silages with different WSN contents (WSN = water soluble nitrogen). Incubation WSN, % in silage total N p! nod 0—39.9 40.0—59.9 60.0—100.0nrs x s.d. x s.d. x s.d. DM 2 29.8 4.6 29.9 6.1 28.5 4.6 5 35.7 4.9 35.4 6.2 37.3 4.5 18 59.8 4.2 57.5 6.8 58.7 8.3 24 66.1 4.9 64.3 7.5 64.7 7.0 N-free DM 2 23.4 5.6 23.2 5.7 20.4 4.3 5 28.6 5.2 27.8 6.3 28.2 4.6 18 48.2 3.4 46.0 5.9 46.3 5.6 24 54.0 3.7 51.6 6.3 51.5 4.6 Crude proteinl 2 41.7 13.3 45.7 10.4 52.5 10.1 5 46.5 14.1 51.9 8.8 59.3 7.1 18 76.2 7.5 77.0 5.6 79.0 6.8 24 79.3 5.2 79.3 4.5 81.1 6.1 N 19 55 17 1 WSN 0—39.9 :y = 34.07x02695 WSN 40.0 59.9 : y = 39.76x02207 WSN 60.0—100.0 : y = 47.59X01730 (y = crude protein degradation, %, x = incubation period, hrs) In 3 silages the crude protein degradability vigorous and long-term fermentations lead to was less than 20 % after 2 hours’ incubation (see Fig. 1). Any clear explanation for this was not found, as for instance the chemical com- position or the quality of these silages did not clearly differ. It is possible that there was an especially strong attack by rumen microbes on feed particles in the bag and in spite of care- ful washings some microbial material had re- mained in the bag thus contributing to the amount of nitrogen in the residue of silage. This would cause »lower disappearance» of crude protein from the bag during the incu- bations. To conclude, our results indicate that a decreased ruminal degradation (fermenta- tion) of the silage dry matter while the degra- dability of the crude protein was increased. This was most evident when the degradabili- ties in the rumen with the first hours after feeding were considered. Regarding the crude protein degradability, it was not possible to calculate the most appropriate crude protein content of the si- lage on the basis of the present data. How- ever, it seems relevant to pay attention to the N-fertilization of grass. The maturity of the grass and its importance in this connection should also be considered. References Anon 1980. Methods of Enzymatic Food Analysis. Boehringer, Mannheim GmbH. Brett, P.A., Dowson, S. & Armstrong, D.G. 1981. In sacco degradability of nitrogen in silages made with various additives. Sixth Silage Conf. at Edinburgh, ed. Harkess, R.D. & Castle, M.E., p. 21—22. Catton, R., Chamberlain, A.G., Paine, Christine A. & Crawshaw, R. 1982. In sacco degradability charac- teristics of two contrasting grass silages. Forage in ru- minant animal productioned. Thomson, D.J., Beever, D.E. & Gunn, R.G. An occasional pubi. of the British Soc. of Anim. Prod., p. 175—176. Goering H.K., Gordon C.H., Hemken R.W., Waldo D.R., Van Soest, P.J. & Smith, L.W. 1972. Analytical estimates of nitrogen digestibility in heat damaged forages. J. Dairy Sci 55: 1275—1280. —, Van Soest, P.J. & Hemken, R.W. 1973. Relative sus- ceptibility of forages to heat damage as affected by moisture, temperature and pH, J. Dairy Sci. 56; 137 143. Heikonen M, Moisio, T. & Kreula, M. 1979. Assessment of the qualityof AIV silage. Valio laboratory pubi. 4: 30—56. Huida, L. 1973. Quantitative determination of volatile fatty acids from rumen samples and silage by gas-liquid chromatography. J. Scient. Agric. Soc. Finl. 45: 483 488, Mfhrez, A.Z. and Orskov, E.R. 1977. A study of the artificial fibre bag technique for determining the diges- tibility of feeds in the rumen. J. Agric. Sci., Camb. 88: 645—650. McDonald, P. 1982. The effect of conservation pro- cesses on the nitrogenous components of forages. Forage protein in ruminant animal production, ed. Thomson, D.J., Beever, D.E. & Gunn, R.G. An occa- sional pubi. of the British Soc. of Anim. Prod., p. 41—49. Miller, E.L. 1982. The nitrogen needs of ruminants. Forage protein in ruminant animal production, ed. Thomson, D.J., Beever, D.E & Gunn, R.G. An occa- sional pubi. of the British Soc. of Anim, Prod., p. 79—87. Ohshima, M. & McDonald, P. 1978. A review of the changes in nitrogenous compounds of herbage during ensilage. J. Sci. Fd. Agric. 29: 497—505. Pekkarinen, E., Syrjälä-Qvist, L. & Setälä, J. 1983. Klöver/timotejförhällandets och timotejs kvävegödsel- mängdens inverkan pä proteinet i ensilage. 17. NJF- mötet i Helsingfors, in press. Setälä, J. 1983. The nylon bag technique in the deter- mination of ruminal feed protein degradation. J. Scient. Agric. Soc. Finl. 55: I—7B. 1984. Preparation of grass silage in Finland and its feeding to dairy cows. Mötet i Uppsala av »Ensilerings- former samt värderingsnormer i ensileringsförsök», 2. 4. 1984, 16 p. Somogyi, M. 1945. A new reagent for the determination of sugars. J. Biol. Chem. 160: 61—68. Thomas, P.C. 1982. Utilization of conserved forages. Forage protein in ruminant animal production, ed. Thomson, D.J., Beever, D.E. & Gunn, R.G. An occa- sional pubi. of the British Soc. of Anim. Prod., p. 67—76. Ms received February 28, 1985 145 SELOSTUS Säilörehun kuiva-aineen ja raakavalkuaisen in sacco -hajoavuuteen vaikuttavat tekijät Jouko Setälä 1 , Alem Tesfa 2 , Aino Kauramaa' ja Esko Poutiainen3 1 Valion tutkimus- ja tuotekehittelyosasto, Kalevankatu 56 B, PL 176, 00181 Helsinki 2 Helsingin yliopisto, Kotieläinlieleen laitos, 00710 Helsinki 3 Maatalouden tutkimuskeskus, 31600 Jokioinen Tutkimuksessa käytetyt 96 säilörehua kerättiin suoraan maatiloilta eri puolilta Suomea. Näytteet kuljetettiin ja varastoitiin pakastettuina. Kuiva-aineen ja raakaval- kuaisen pötsihajoavuus määritettiin nailonpussi-menetel- mällä käyttämällä koe-eläiminä kahta pötsifistelöityä lam- masta, jotka olivat säilörehu-heinä-ruokinnalla (50 : 50 kuiva-aineen perusteella). Säilörehussa olevat typettömät uuteaineet lisäsivät ja raakakuitu vähensi kuiva-aineen hajoavuuttapötsissä kor- relaatioanalyysien mukaan arvioituna. Yleisesti tarkas- teltuna säilörehun käymistuotteiden korrelaatio kuiva- aineen hajoavuuteen oli negatiivinen. Säilörehun raakavalkuais- ja NOj-sisältö korreloita- vat positiivisesti raakavalkuaisen hajoamisasteeseen pöt- sissä. Säilörehussa tapahtunut proteolyysi (NH 3-, liukoi- sen typen määrä) lisäsi puolestaan raakavalkuaisen ha- joamisnopeutta.Rehun raakakuitupitoisuuden ja raaka- valkuaisen hajoavuuden välisen negatiivisenkorrelaation perusteella raakakuidulla oli hajoavuutta vähentävä vai- kutus. 146