This invention relates to forage production and may be used at factories processing non-edible waste of livestock farming products.

As a protein source for feeding poultry and livestock waste of keratin-containing stock is used, e.g., waste of poultry-processing industry; waste of poultry evisceration, such as feather, fluff, blood, heads, wings, giblets, etc.

Among waste of poultry evisceration almost 50% of proteins are contained in feather and fluff stock. Keratin is the main protein of feather. Apart from poultry feather, keratin is contained in horn and hoof stock of farm animals.

Keratin is highly stable to action of various agents, e.g., water, esters, alcohols, salt solutions, weak acids, to action of light, heating; it does not break up by enzymes contained in the digestive juices of human beings, animals and poultry, is not practically digestible, therefore methods of processing keratin-containing stock are aimed at transferring keratin from the non-digestible to a digestible form.

The commonly used methods of processing keratin-containing stock are subdivided into:

• hydrothermal treatment;
• acid, alkaline and enzymatic hydrolysis.

Hydrothermal methods of processing keratin-containing stock are known in the art. One should take into account that hydrolysis of keratin in an aqueous medium is most efficient at a temperature above 150°C ( Vestnik Selskokhozyaistvennoy Nauki, 1980, No. 12, p.119-121 ).

A method of processing feather-fluff stock at 185°C in special high-pressure vessels (0.8 - 1.0 MPa) until full dissolution is known in the art ( FR 2241257 ).

Such closed apparatus for batch operation are very expensive and relate to equipment subjected to boiler inspection. They are not of wide practical use.

A method of processing keratin-containing stock into animal forage is also known, which comprises hydrolysis of stock by water-heat treatment. Stock is comminuted before hydrolysis, hydrolysis is carried out at 120 - 140°C for 20 - 40 minutes with subsequent extrusion at a pressure ranging from 4.0 - 5.0 MPa for 15 - 30 seconds ( SU 1757580 ).

Disadvantages of the above methods are that: extrusion is possible only if the moisture content of stock does not exceed 35%, steam consumption during heat treatment is high, the processes are time-consuming and biological value of the obtained product is reduced greatly. Apart from this, the processes are long, since each treatment requires extra time, and time of treatment (ranging from 6 to 12 hours) results in thermal denaturation of proteins, destruction of amino acids and formation of cyclopentides that are unavailable for action of enzymes in the gastrointestinal tract of animals and poultry.

A method of producing a meat-meal is known that comprises alternative cycles of mechanical compression of stock with simultaneous comminution and heat treatment of stock and vacuumization ( SU 627810 ). But it is impossible to obtain a forage product from feather with this method, since it lacks a mechanism of feather fine comminution.

The closest method of feather processing is a method for producing a forage supplement from keratin-containing stock, which comprises heating and comminution of feedstock, sterilization and drying ( US 4203892 ). According to this method, feather is subjected to moisture-heat treatment at 180 - 240°C for 2 - 10 minutes and is quickly transferred to a low-pressure environment.

Feather hydrothermal hydrolysis and sterilization occurs.

However, this method also has disadvantages, in particular expensive equipment and high power consumption.

The objective of this invention is to simplify the technological process, reduce costs, improve the quality of a protein supplement and avoid using additional chemical agents.

The stated objective is achieved due to that the inventive method for producing a forage supplement from keratin-containing stock comprises heating and comminution of feedstock, sterilization and drying, where feedstock with an initial moisture content of 35 - 95% is used, then it is further compacted and heated in the channel of a mixer comminutor at continuous feeding, pressure ranging from 0.4 to 10.0 MPa and stock temperature ranging from 60 to 120°C; then stock is subjected to hydrothermal treatment at 150 - 250°C for 5 - 300 seconds with simultaneous fine comminution and abrasion, and then the processed stock is taken out into an atmospheric pressure area.

Further, the processes of fine comminution and water hydrolysis of keratin are combined and carried out in a thin layer with a thickness up to 20 millimeters.

The inventive method is carried out as follows.

Wet feather, after separation of excess water necessary for transportation of feather from a slaughter floor with the use of a screen separator (feather moisture content is about 50%), is fed to a header bin in various directions by screws.

Feather, captured by screws, is fed to the channel having a form generated by two or more crossing parallel cylinders.

The channel walls are heated by a heat-transfer agent. Water contained in feather boils in the near-wall layer. Vapor immediately runs through the feather thickness, condenses in the depth of the feather mass and, thus, transfers heat to the depth due to transfer of the latent heat of vaporization. Condensate comes back to the wall and evaporates again.

Simultaneously with heating the screws abrade feather, comminute and compact it gradually. When feather is heated, its mechanical strength is reduced significantly, this makes its comminution easier.

Feather is compacted by changing (reducing) the screw capacity. In order to obtain a reliable lock in the channel it is necessary to reduce the screw capacity, as compared to their capacity in the header bin, 6-8 times.

Apart from this, in the area of maximum pressure shafts are provided with screws with opposite direction of threads, i.e. with screws acting in the opposite direction.

The channel area, where maximum compaction of feather takes place, is determined in such a way that the feather temperature in this area would not be higher than 60 - 120°C.

Obtaining a lock enables to increase the temperature of feather, comminute it, raise the pressure further. Apart from this, the screws perform the transportation function, namely move feather (stock) within the channel, at preset parameters: temperature 150 - 250°C, pressure 0.4 MPa - 10.0 MPa. Prior to exiting the channel the stock should be contained in the channel with preset parameters at least for 5 - 300 seconds, because this corresponds to the reaction time of feather hydrolysis. If the parameters of temperature, pressure and time are decreased or increased, the technical effect cannot be achieved.

In order to improve heating, the screw in the final section of the plant is made with hollow threads within which a heated heat-transfer agent flows.

The three sections of the plant enable to separate the functions, simplify the design and the production technology.

The first section is the gripping bin with screws carrying out preliminary comminution and preliminary heating.

The second section is for further heating, compaction for obtaining a reliable lock, and for more uniform comminution of feather.

The third section is for comminution of feather, its heating and maintenance of a preset time of high-temperature water hydrolysis.

The three sections are made as similar channels having the form generated by two or more crossing parallel cylinders, within which screws rotate. In the first section the screws rotate in opposite directions, in the second and the third sections the screws rotate in one direction.

In the end of the third section a valve is located - a device enabling to take out processed feather from the area of high pressure and temperature to the receiving container with the atmospheric pressure. This device is a displacement pump which prevents liquid from boiling in the channel and, thus, prevents temperature from rising.

After processing a friable, finely comminuted fraction (powder) is obtained, which may be used for feeding poultry and animals without additional drying.

Without simultaneous heating, the comminuting power was 90 kW. If heating jackets are installed in the working area and stock is heated to 100°C, the comminution process was carried out with the power consumption of 7 kW, and if stock was heated to 180°C the power consumed by the engine was reduced 13-15 times.

The results of the sterilizing effect are shown in Table 1. No. Type of stock, heating time, sec Total seeding, 1·10⁶ CFU/g Temperature, °C 100 110 120 130 140 150 160 Feather-fluff waste 1 0 17,300 2 10 11,500 5,300 910 6.3 0.3 0.1 0.01 3 20 6,800 1,150 0.1 0.05 0.01 0.001 0.001 4 30 780 210 0.03 0.01 0.001 - - 5 40 3.5 1.7 0.01 0.001 - - - 6 50 0.9 0.1 - - - - - 7 60 0.1 0.01 - - - - -

It can be seen from the Table that industrial sterility of poultry evisceration waste can be achieved at 140 - 160°C after heating for 10 - 20 seconds.

Short-time treatment at 150 - 180°C does not impair the fat quality and ensures full preservation of essential amino acids. Most sensitive to heat treatment is lysine.

Therefore, the parameter of available lysine content was chosen as a test for thermal stability of proteins from evisceration waste after high-temperature short-time treatment.

Table 2 shows the study results on influence of high-temperature heating (160 - 180°C) time on available lysine content in a feather paste-like slurry. No. Specimen designation Heating time, sec Available lysine content, % 1 Feather specimen 1 0 100 2 Feather specimen 2 180 80.0 3 Feather specimen 3 300 63.8 4 Feather specimen 4 420 42.2 5 Feather specimen 5 1,200 36.8

According to literature sources, reduction of heating time to less than 5 minutes increases the available lysine content to 80% of the initial value.

The study results on digestibility of the final product versus heating temperature are shown in Table 3. No. Specimen designation Heating temperature, °C In vitro digestibility, % 1 Feather specimen 1 130 23/1 2 Feather specimen 2 150 35/5 3 Feather specimen 3 170 73.8 4 Feather specimen 4 190 80.2 5 Feather specimen 5 210 80.8

The study results on vapor pressures in the working area are shown in Table 4. No. Specimen designation Vapor pressure in the working area, MPa In vitro digestibility, % 1 Feather specimen 1 0.3 23.1 2 Feather specimen 2 0.5 62.2 3 Feather specimen 3 0.7 73.8 4 Feather specimen 4 1.0 79.0 5 Feather specimen 5 1.6 80.3 6 Feather specimen 6 3.0 81.1

Optimal parameters of the feather product after hydrothermal treatment (in vitro digestibility 80/3%) were obtained at heating temperature 180°C, pressure 1.6 MPa and processing time 90 seconds.

Further studies were conducted on the above specimen.

The study results on chain-length distribution show that after high-temperature short-time treatment protein compounds are affected by hydrolysis processes to a significantly greater degree than after hydrothermal treatment according to the commonly used technology.

Specimens of a feeding meal and a hydrolyzed feather powder, which were produced according to the common technology, were taken as control specimens.

The results are shown on Illustration 1.

1. 1) Feeding meal according to GOST 17536-82
2. 2) Protein supplement from technical waste
3. 3) Hydrolyzed feather powder according to GOST 17537-82
4. 4) Protein supplement produced from feather by the inventive method.

Illustration 1. Comparative study of molecular weights of poultry evisceration waste hydrolysis products after high-temperature short-time treatment

The obtained data are correlated with biological assessment results and results published by US companies Wenger and Insta Pro.

After high-temperature short-time treatment of feather it is recommended to conduct additional enzymatic treatment.

In such a case digestibility of the feather protein supplement increases to 92 -96%.

Studies were conducted on determining relative biological value with a microbiological method; the results are shown in Table 5. No. Specimen designation In vitro digestibility, % Number of infusoria in 1 mL*10⁴ RBL, % vs. casein 1 Casein (control) - 27.0 - 2 Feather powder according to GOST 17536-82 28.0 12.8 46.3 3 Feather protein supplement (experiment) 80.5 24.8 92.0

The study results on tetrachimena piriformis show that relative biological value (RBV) of the feather protein supplement (experiment) is 2 times higher than that of a traditional meal according to GOST 17536-82.

Studies were conducted on determining biological values of protein forage supplements for growing rats (Table 6).

Rats from control groups were fed with hydrolyzed feather powder (Group 4) produced according to the traditional technology.

Rats from experimental groups were fed with the feather protein supplement (Group 5) produced with high-temperature short-time treatment (HTST). Groups by product Consumed, g/head Weight gain, g NPR NPU, % Forage Protein Casein 97.01 11.58 38.66 3.62 59.38 Feather powder according to GOST 17536 (control) 53.08 5.59 4.86 1.45 25.76 Feather protein supplement HTST* (experiment) 63.87 7.30 17.16 2.80 46.73

Net protein ratio (NPR) and net protein usage (NPU) of the feather protein supplement in the experimental group were 2.80 and 46.73%. For the control group these indices were 1.45 and 25.76%. The results show that high-temperature short-time treatment enables to produce forage products from poultry evisceration waste, which biological values are almost 2 times higher (according to NPR and NPU) than for products made according to the traditional technology.

Results of feeding broilers with the protein supplement are shown in Table 7. No. Indices Control group Experimental group 1 (dry supplement) Experimental group 2 (paste-like supplement) 1 Live weight at the day age, grams 41.5 41.6 41.7 2 Live weight at the age of 49 days, grams 2,117 2,243 2,160 3 Average daily weight gain, grams 42.3 44.9 44.9 4 Forage consumption per 1 kg of live weight gain, kg 2.43 2.31 2.17 5 Forage consumption per head, kg 5.04 5.08 4.77 6 Fish flour consumption per head during fattening period, grams 231.7 57.6 75.6 7 Meat-bone flour consumption per head during fattening period, grams 133.9 - - 8 Feather protein supplement consumption per head during fattening period, grams - 172.4 236.3 9 Fish flour savings per head during fattening period, grams 174.1 156.1 10 Meat-bone flour savings per head during fattening period, grams 133.9 133.9 11 Cost reduction per 1 ton of meat owing to saved fish flour and meat-bone flour, in US dollars 90.0 82.8 12 Additionally produced meat after feeding 1 ton of dry feather protein supplement, kg 438.0 695.0 13 Quantity of possibly replaced fish flour by feeding 1 ton of feather protein supplement, ton 1.0 0.7

Thus, the implementation of the inventive method will enable:

• improve the use of internal resources at poultry factories (due to two-fold increase in protein digestibility);
• add feather keratin to the field of feeding;
• reduce the need in fish flour;
• improve the sanitary condition of animal-origin forages;
• reduce the process time and energy costs;
• improve ecological safety in shops engaged in poultry evisceration waste disposal.

This invention is industrially applicable and may be most successfully used at factories processing non-edible waste of livestock farming products. The inventive method may be implemented on any known equipment and does not require special tooling.