¹Biology faculty, University of Belgrade, Botanical Garden, Belgrade, Serbia and MonteNegro
²Agriculture faculty, University of Belgrade, Belgrade Serbia and MonteNegro
³Institute for technology of nuclear and other mineral material, Belgrade, Serbia and MonteNegro

If doubt about possibilities for utilization of Pleurotus ostreatus mushroom spent subsrata in dairy cows feeding still exist, this article will definitely eliminate it. Namely, in this article presented results are obtained in the experiment which was created with goal to estimate the milk yield and composition, diet consumption and nutrient utilization The trial was conducted on 36 Holstein Frisian cows divided in three groups (K, I , II) during. Control group (K) received standard farm diet (alfalfa hay, corn silage silage, soybean meal, brewers grain, concentrate). Groups I and II received diet supplemented with 2 and 4 kg of spent substrata (20,59% DM) instead 1 and 2 kg of corn silage (41,39% DM) respectively. Group II had lower consumption (3.2 kg, or 18,40% of diet DM) of spent substrata than it was planned because of specific smell and taste. With increase of spent subsrata DM rate in the diet average milk yield declined (22,51: 21,67: 20,75 kg/day). Dry solids without fat, protein and lactose content in milk also declined, whereas milk fat was increased. Determined differences were not statistically significant (P>0,05). Dry matter intake of the diet per kg of milk was higher by 2,56 and 7,69% in experimental groups. The energy concentration in the diet was lowered with spent substrata supplementation, and NEL/kg of milk was increased. Protein consumption per kg of milk increased from 115 g/kg to 120 and 126 g/kg. Higher digestibility of spent substrata, comparing to initial material by 12.92 percent points, in digestive tract increased synthesis of volatile fatty acids which are the precursors for milk fat synthesis. Milk fat percentage in experimental groups was increased by 0,11 and 0,15 percent points.

Key words: mushroom, feeding, substrata, and cows, milk

INTRODUCTION

Cultivation of Pleurotus ostreatus mushroom is based on usage of lignocellulose materials. Those materials are used as a substrata for spawning with mycellia. Sawdust, parings, tree bark, seed husks and the other lignocellulose materials can be used. About 900 000 tons of the mushrooms of Pleurotus family and 2 300 000t of spent substrata is produced all over the world each year (Chang, 1993.). Spent substrata can be used as fertilizer. According to the results (mentioned by Bano et al. 1984; Kakkar et al., 1990; Platt et al, 1984.; Rajarathnam and Bano, 1989 and Adamovic et al., 1994.) spent substrata can be used for the nutrition of domestic animals. There is also a possibility of its usage in production of biogas, fertilizers, cardboard, compost for champignon production, sugar on the basis of cellulosic matter, monocellular proteins, materials for decolouring waste sulphate liquids, molasses pigments etc.

Chemical composition of substrata. In the process of preparing straw as a substrata for cultivation of Pleurotus ostreatus mushrooms, wetting, cooking and spawning of mycelia has to be done. Pasteurising eliminates moulds and spores which negatively affect production, weakens lignocellulose connections and increases the efficiency of mushroom enzyme systems activity. By the activity of, lakaze, cellulaze, celobiaze, hemicellulaze, ligninaze enzymes and others, the lignocellulose complex is decomposed into simpler organic compounds which mushrooms uses as nutritious substances. Thus the chemical composition of substrata changes in comparison with the initial material (Adamovic et al., 1994.). Spent substrata consists of the lignocellulose complex remains which are not decomposed, unused decomposed molecules and mushroom mycelia. Pleurotus ostreatus mycelia consists of a thick bundle of hypha. The major component of the cells' walls of the fungy at all, is chitine which is barely usable in domestic animals nutrition. The mycelia of Pleurotus ostreatus contains proteins of high biological value with the essential amino acids and the presence of the specific macro and micro elements (Flegg et al., 1985.). Well prepared and well-kept substrata does not contain the mycotoxins aflatoxin, ohratoxin, zearalenon, patulin, sterigmatocistine, penicillin acid and citrinine (Bano et al. 1984).

In comparison to straw the amount of raw fibres in spent substrata is smaller for 10,56 percent points expressed on 100% DM (Adamovic et al, 1994.). According to Kakkar et al., (1990) the amount of the raw fibres in substrata has decreased in comparison to straw from 41,84% to 33,20%, the amount of NDF (neutral detergent fibre) from 76,10% to 66,35%, ADF (acid detergent fibre) from 47,08% to 46,77%, hemicellulose from 29,03% to 19,98%, cellulose from 35,27% to 32,51% and lignin from 5,85% to 5,10%. The amount of raw substrata proteins has increased from 3,06% to 3,94% in comparison to straw which is in accordance with the results reached by Milenkovic (1993) and Adamovic et al., (1994). The chemical composition changes are also caused by the conditions of cultivation , number of gatherings and the length of compost exploitation. The content of the raw proteins increases until the 60th day of incubation, then decreases until the 120th day (Adamovic et al., 1998). The fat content decreases constantly. The NDF content decreases from 824 to 485g kg, ¹ADF from 561 to 412 g kg, ²hemicellulose and cellulose, but as far as lignin is concerned that is not so obvious. On the contrary, the content of dry matter and ashes increases.

¹ Fibres determined by neutral detergent method according to Van Soest and coll. (1991)

² Fibres determined by acid detergent method according to Van Soest and coll. (1991)

The use of the substrata in cattle nutrition. After finalization of the mushroom flushing gathering spent substrata can be used in nutrition of ruminants thanks to the constitution of their digestive system. Micro-organisms decompose cellulose and hemicelluloses with their enzymes, and the final products are evaporable fatty acids (acetic acid, propionic acid and butter acid). Lignin is feebly digestible. The share of lignin in cell wall increases by the plants ripening, the lignin molecules connect with the molecules of carbo-hydrates and they decreases their digestibility. About he 30 - 50% of cellulose and hemicelluloses decompose in the tripe (Grubic and Adamovic, 2003). Cows provide about 70% of needed energy from the evaporable fatty acids (EFA). EFA appeared in tripe represent the source of energy for keeping and increasing muscles, for milk production, and provide the energy for milk proteins synthesis and represent the precursors for lactose and lactic fats synthesis.

The possibility of the substrata usage in nutrition of domestic animals was studied by Kaneshiro (1977), Bano et al. (1984), Kakkar et al. (1990), Platt et.al. (1984), Rajarathnam and Bano (1989), Zadrazil (1993), Adamovic et al. (1994 i 1996). Adamovic et al (1996) studied the possibilities of the exploitation of insufficiently used compost of the Pleurotus ostreatus mushrooms in nutrition of the bullocks in the second fattening phase. The average daily increase of the bullocks fed with meals with the share of spent compost of 0; 10 and 17% in DM meals was significantly smaller for 13,75% (P<0,01) only between the first and the second treatment. The presence of substrata has decreased the nutritive value of the meals and decreased the usage of DM in kg of increase. The bullocks have consummated the substrata mixed with silage or concentrate mixture well, while the consummation of the substrata itself was a little bit more lesser. The biochemical parameters of the blood serum were within the physiological values, except Ca and P in the group of bullocks which has been given the meals with the biggest amount of substrata (Adamovic et al, 1996). According to the resurch results it has been concluded that substrata could be used in reproduction of breeding bullocks which should accomplish smaller daily growth (600 - 800 g/per day).

It is recommended that compost should participate in a meal to 20% of dry matter of a meal. Kakkar et al. (1990) have come to the similar conclusions regarding to which there comes to the more significant decrease of the growth by increasing the compost share in a meal. The possibility of substrata silaging. Spent Pleurotus ostreatus substrata has a specific taste and smell and the cattle consummate it less if it is served alone. The consummation is better if it is mixed with some more tasteful nutriments (for example with silage, mixture of concentrates). The way to increase its taste is silaging. Silaging gives the substrata some better organoleptic qualities and increases the consuming of substrata. Spent substrata has sufficient humidity to be silaged. On the other hand, exploited substrata does not contain enough easily soluble carbo-hydrates, so the silaging must include nutriment which has enough carbo-hydrates (plant or grits). That way microorganismes are supplied with enough sugar, which when decomposed gives lactic acid, which is the main preserving agent and is the bearer of taste and smell (Adamovic et al, 1999). Kakkar et al (1990) and Adamovic et al (1998) consider that the share of spent compost in corn silage should be between 20% and 30%, while the amount of consummating of silage is not decreasing. The taste of silage could be improved by adding evaporated whey and molasses during silaging.

MATTERIAL AND METHODS

The experiment was done on the 36 cows of European black and white cattle type with participation of holstein-frizian genes, divided into three groups (K, I and II), with 12 head of cattle in each group. The groups where mutually equalized according to number of lactations, lactation faze, amount of milk and body mass. The cows were in the first half of lactation approximately 52 days. The experiment has lasted for 45 days. The preparation time has lasted for 7 days, and experimental 38 days. The control group has been fed with the standard meal used on the farm. In the meal of experimental groups 1kg i.e. 2kg of corn plant silage have been replaced with 2kg i.e. 4kg of spent substrata. The content of nutriment is given in the Table 1.

The substrata was packed in nylon sacks of 8kg. The other nutriments (hay of lucerne, plant corn and cob silage, soybean meal, brewery spent grain and concentrated feed) where given to cows in approximately equal amounts in all three groups (Table 2).

The composition of the concentrate was given in the Table 3. The amount of the consummated food has been established on a daily basis. The normative NRC (1989) were used in the meal composing for the cows in the first half of the lactation period.

The control of cow milking capacity was done in the beginning of experiment, and then on the 14th, the 28th and the 38th day. The milk samples were taken from each cow, on the day of milk control, and the content of DM, fats, proteins and lactose has been determined.

Chemical analyses of nutrients were done based on the standard (AOAC - Association of Official Analytical Chemists, 1984) methods. The amount of macro elements in the nutrients was determined according to Rowe`s method with atomical absorptive spectrophotometer, Varian, 635 D. The composition of milk was determined with Milko-Scan 104/SN apparatus.

Digestibility was determinated with Tilly's and Terry's method (1963) In vitro. The nutrients ground on 1 mm diameter sieve have been put in the solution of the tripe's content. The tripe's content was taken from the three head of cattle and filtered through the gauze. The food incubation in the tripe`s content lasted 48 hours on 39�C. After that phase the sample was centrifugated, the liquid fraction was removed and then the incubation was done in the pepsin sour solution lasting 48 hours on 39�C. The undigested fraction of nutriment was separated with filters, and then was dried in drier. The established difference in the mass of dry matter before and after incubation was put in relation with the mass of dry matter before incubation, and thus the digestibility of the dry matter was established (%). The results were statistically processed by the variance analysis (Seducer and Cochran, 1982).

THE RESULTS AND THE DISCUSSION

The food consuming. The cows from the group I consumated 2kg of spent substrata which was determined by the experiment`s plan, instead of 1 kg of silage, which was 11,54% DM of meal. It was provided by the experiment`s that the group II should be given 4kg of spent compost in a meal instead of 2kg of silage. But this group of cows consumated 3,2 kg of spent compost, i.e. 18,40% DM meals. The cause of lesser consuming of compost was the specific taste of spent substrata. These results are in accordance with the results of Adamovic et al. (1996) who established that the bullocks in the second phase of fattening can consume up to 17% of dry matter of a meal which originate from substrata, but that leads to decreasing of growth and efficiency of the meal usage. Kakkar et al., (1990) mentioned that the spent substrata consumation would be better with the fattened bullocks which were given the substrata in combination with the nutrients of better taste and smell. The chemical composition and nutritive value of the used meals is given in the Table 4.

Production of milk and its composition. The amount of raw milk decreased with the increase of participation of dry matter in Pleurotus ostreatus spent subsrata in dry matter of a meal (Table 5). Group K had the milking capacity of 22,51 kg per day. Group I in which 1kg of corn plant silage was replaced with 2 kg of spent compost had milking compacity 21,67 kg per day, which is 0,84 kg or 3,73% less than the control group. Group II attained the smallest milking capacity (20,75 kg per day), which is 1,76 kg or 7,82% less than the control group. The established difference between the groups wasn't statistically significant (P>0,05). The same trend was established in milk corrected to 4% of milk fat. The distinction between the experimental groups and the control was 0,42 kg (2,00%) i.e. 1,17 kg (3,57%). The content of dry matter without fat, proteins and lactose in milk decreased with increasing the share of compost in a meal, while the fat amount increased.

The usage of nutritive meal matters. The usage of nutritive meal matters is shown in table 6. The consumation of dry matter per kilogram of raw milk increased with raising of the share of compost in a meal. Group I consumed 0,02 kg or 2,56%, and the group II consumed 0,06 kg or 7,69% of dry matter more than group K.

The usage of NEL per kg of raw milk increased in groups I and II in comparison with the group K for 0,20 MJ or 4,02% i.e. 0,43 MJ NEL or 8,63%.

Due to the smaller content of NEL in spent substrata than corn plant silage the meal concentration was decreased, and due to this also the efficiency of using it in the milk production decreased. That means that larger quantity of food is needed for getting the same quantity of milk. Because of that the optimal range of substrata using must be found for keeping the satisfactory milk production. The group I had for 0,02 MJ/kg, and the group II for 0,04 MJ/kg DM meals smaller concentration in comparison with the group K.

The usage of total proteins (TP) per kg raw milk increased in the groups I and II. The smallest usage of TP per kg of milk had the group K, and it was 115 g/kg of milk. The groups I and II had for 5 g or 4,35% i.e. 11 g or 9,75% bigger needs for TP for producing 1 kg of milk. The similar trend is in the needs of total proteins per 1 kg 4% MKM.

Inclusion of spent substrata in the meals for cows effected the decreasing of meal usage efficiency and its concentration, which had the bad effect on milking capacity .

Digestibility of compost. The composition of lignocellulose complex and in vitro digestibility of wheat straw and spent substrata of Pleurotus ostreatus is given in the Table 7.

The effect of Pleurotus ostreatus enzymes (cellulase, hemicellulase, celobiase, ligninase etc.) had the influance on lignocelullose complex decomposition, which caused its lower content in spent compost in comparison with wheat straw which was the base nutritive ground for the Pleurotus ostreatus mushrooms (table 7).

The content of NDF, ADF and ADL³ (acid detergent lignin) and cellulose in the compost was smaller for 24,21 ; 5,82 ; 0,33 and 12,45 percent points in comparison with the straw. The smallest difference was determined in the lignin content which confirms that lignin is the most difficult decomposed ingredient of lignocellulose complex of straw.

³ Lignin determined by acid detergent method according to Van Soust and coll. (1991)

The content of lignocellulose straw complex spent substrata shows the decreased digestibility of spent subsrata of Pleurotus ostreatus in comparison with straw.Substrata digestibility established by Tilley and Terry's method (1963) is bigger for 12,92 percent points. Decreased digestibility of lignocellulose complex of spent substrata caused a bigger usage of cellulose in cows` digestive tract and synthesis of evaporable fatty acids, first of all acetic acid, which is the precursor for lactic fat synthesis. That is proved by the results which show that the percent of lactic fat is decreased in the experimental groups for 0,11 and 0,15 percent points in comparison with the control group.

THE CONCLUSION

Including spent substrata of the Pleurotus ostreatus in nutrition of cows in lactation in amount od 2 kg (I) i.e. 3,2 kg (II) effected the decrease of daily production of row milk in 4% MKM. The amount of row milk was smaller for 0,84 and 1,76 kg or 4% MKM for 0,42 and 1,17 kg, respectively, in comparison with the control group. The established difference was not statistically significant (P>0,05). The content of dry matter without fat, proteins and lactosis decreased by increasing the share of substrata in a meal while the content of lactic acid increased. Consummation of spent substrata, due to its specific smell and taste, was limited. The maximum consumation of spent substrata was 3,2 kg/per day/ per head, or 18,40% DM meals. The usage of DM per kg of raw milk increased for 0,02 and 0,06 kg in comparison with the control group, and NEL for 0,20 and 0,43 MJ. Adding of spent substrata effected decreasing of meals concentration and efficiency of its utilization. The digestibility of dry matter of compost (43,54) in comparison to straw (30,62) was higher. Because of the specific taste and smell the efficiency of spent substrata Pleurotus ostreatus usage in nutrition of cows in lactation was higher if given in complete meals. The limited amount of used compost (up to 4 kg/per head daily) doesn't cause significant unfavourable consequenties in the production of milk and milk composition.

April 2006 final article by Milan Adamovic and Ivanka Milenkovic