IE940806A1 - A process for making pelletised animal feed - Google Patents

Abstract

A pelletised animal feed is prepared by grinding raw materials in a grinder (203), mixing the ground raw material in a mixer (301) and delivering the mixed material to a pressure cooker (303). The mixed material is cooked and then extruded and pelletised to form pellets which are delivered onto a top bed (403) of a dryer (401). An initial active drying operation is carried out by forcing hot air up through the top bed (403). The pellets are then dropped onto a lower intermediate bed (404) where they are retained for the drying time in a static drying operation before being dropped onto a bottom bed (405). A final active drying operation is carried out by forcing hot air up through the bottom bed (405) for the drying time and extracting the hot air from the dryer (401) above the bottom bed (405) and below the lower intermediate bed (404). The dried pellets are cooled in a cooler (407) and delivered to bulk storage bins (501). A pelletised animal feed produced by the above process is also disclosed. <Fig. 5>

Description

A process for making pelletised Animal Feed Introduction The present invention relates to a process for making pelletised animal feed often called extruded feed. For convenience the term pelletised -is mainly used in this specification. A primary requirement in the manufacture of pelletised animal feed is to ensure that there is accuracy and repeatability in the formulations. It is essential to provide formulations which give the animal the appropriate nutrients. Not alone will this vary from animal to animal, in the sense that, for example, a dog food has to be of a different formulation than a cat food, but there is a need for different formulations for the same type of animal, depending on the animal's condition and in many cases the time of the year. For example, pregnant animals require a different formulation of feed than younger or older animals. Pelletised feed is often used for domestic pets and various farm animals such as chickens, ducks, hens, etc. as well as an additive to other feeds.

A major problem in the production of pelletised animal feed is the need to utilise costly capital equipment as economically as possible, provide the best possible throughput of product and generally have the optimum operation and utilisation of equipment. One of the major costs in the production of pelletised animal feed is the running costs of the plant and in particular energy costs . Thus, there is a need to conserve energy by providing the most efficient way of carrying out any particular process. It will be appreciated that in a pelletising operation there is a considerable amount of heat used in the pressure cooking and drying operations which heat is then as it where lost in wraB2^p Iin I -ά·23η iP-loo j at drying and cooling OPEN TO PUBLJC INSPECTION UNDER SECTION 2β AND RULE 23 JNL. No.../.?.£&.......OF $/9/% operations. Drying and cooling is vital in such processes because the product has to be dried and cooled to prevent deterioration during storage thereby improving stability and increasing shelf life. Thus, the need for cooking at relatively high temperatures followed by rapid drying and cooling to ambient temperature means that energy requirements are relatively high and the need for heat recycling is essential. This has been long appreciated by those operating such plants, but in many instances has not been successfully achieved.

Finally, what is often forgotten is the obvious fact that animal feed and in particular pet food is purchased by humans and not by animals. In spite of attempts by the advertising profession to suggest that pets can discriminate between various forms of pet food, most owners of pets are well aware that this is not the case. Accordingly, most pet foods are bought by owners on the basis of the owners being persuaded that it is suitable, wholesome and nutritious. Since in general humans will not taste the pet food, the way in which it is judged is by its general appearance such as texture, smell, colour, etc. Accordingly, there is a need to ensure that the pet food is pelletised in a uniform fashion, that it does not have fines and dust in it, and generally has a pleasing feel and appearance. Even those rearing and feeding animals as part of a business who would pride themselves on a more professional approach to the choice of feed are not by any means immune to the fallacy of judging the pelletised feed by smell, feel and appearance generally.

It is an object of the invention to provides a process for making pelletised animal feed which suffers none of these disadvantages .

Accordingly there is a provided a process for making pelletised animal feed comprising the steps of: delivering the raw material to a grinder; grinding the raw material; delivering the ground raw material to a pelletiser mixer; mixing the ground raw material; delivering the mixed material to a cooker; cooking the mixed material; extruding and pelletising the cooked material to form pellets; delivering the pellets onto a top bed of a dryer; carrying out an initial active drying operation by forcing hot air up through the top bed for a pre-set drying time; extracting the hot air from the dryer above the top bed; dropping the pellets onto a lower intermediate bed; retaining the pellets on the intermediate bed for the drying time in a static drying operation; dropping the pellets onto a bottom bed; carrying out a final active drying operation by forcing hot air up through the bottom bed for the drying time; extracting the hot air from the dryer above the bottom bed and below the intermediate bed; delivering the dried pellets to an air cooler; cooling the pellets; and delivering the dry pelletised animal feed to bulk storage bins.

Preferably the hot air is forced up through lower elongated slits into a bed, across within the bed and out of the bed through upper elongated slits, said upper elongated slits being offset from the lower elongated slits .

In one embodiment of the invention the hot air from each active drying operation is provided by mixing some of the wet hot air delivered out of the dryer with hot air from the cooler.

In a preferred embodiment of the invention, the ratio of recycled air from the dryer to that from the cooler is within the range 10:1 to 4:1.

In another embodiment an individual air heater is provided for each active drying operation.

In another embodiment the air extracted from the dryer and cooler is first delivered through a cyclone to extract entrained fines.

In a further embodiment the moisture content of ground raw material introduced into the cooker is within the range 9% to 15% by weight.

Hojo ζ-? Preferably the moisture content of ground raw material introduced into the cooker is 12% by weight.

In another embodiment the raw material on cooking has a moisture content within the range 25% to 40% by weight and a temperature within the range 125°C to 145°C and which on delivery out of the extruder moisture is flashed off so that the moisture content of the pellets is reduced by 4% to 10% by weight.

Preferably the raw material on cooking has a moisture content of 32% by weight and a temperature of 135°C and which on delivery out of the extruder moisture is flashed off so that the moisture content of the pellets is reduced by 8% by weight.

Ideally, there is performed the additional steps of: delivering a pre-determined volume of pelletised animal feed to a mixer from the bulk storage bins; weighing the feed in the mixer; weighing batches of feed liquid; adding the batches of feed liquid to the mixer until a predetermined weight is achieved; mixing the animal feed and oil to coat the feed; delivering the treated animal feed into a conditioning bin; holding the animal feed in the conditioning bin for a predetermined lay time; delivering the animal feed to a storage bin; and *940800 delivering the animal feed from the storage bin to a bagging and pelietising plant.

Preferably the feed liquid is heated within the range 45°C to 75°C prior to addition of the mixer.

Ideally the feed liquid is heated within the range 55°C to 60°C.

In another embodiment the invention provides a pelletised animal feed whenever produced by the process described above.

Detailed Description of the Invention The invention will be more clearly understood from the following description of a process according to the invention shown by of example only with reference to the accompanying drawings in which:Fig. 1 is a block diagram showing in outline the various portions of the plant; Fig. 2 is a diagrammatic view of the raw material storage equipment; Fig. 3 is a diagrammatic view of the plant used for the grinding operation; Fig. 4 is a diagrammatic view of the pelletising/ extrusion process equipment; Fig. 5 is a diagrammatic layout of the drying and cooling process plant; Fig. 6 is a perspective view of a portion of a top bed of a dryer used in the drying process; Fig. 7 is a perspective view of the bed illustrated in Fig. 6 in an open position; Fig. 8 is a diagrammatic view of bulk product storage equipment; Fig. 9 is a diagrammatic view of the packing and bagging equipment; and Fig. 10 is a detailed diagrammatic view of portion of the packing and bagging equipment.

Referring initially to Fig. 1 there is shown in block diagrammatic form the various processes carried out and the flow of materials during the manufacture of pelletised animal feed according to the invention. There is also a reference in Fig. 1 at each process of the drawing or drawings in which a more detailed layout is contained. Thus, in accordance with the invention, there is a raw material storage operation, the equipment indicated generally by the reference numeral 100 from which the raw material is sent for a grinding operation with the plant, indicated generally by the reference numeral 200 and then to a mixer indicated generally by the reference numeral 250 where vitamins, mineral and hot liquids are added. The ground and mixed raw materials are then sent directly to a pelletising process in which the equipment is indicated generally by the reference numeral 300. Then the pelletised pet food is sent to a drying and cooling operation and the plant is indicated generally by the reference numeral 400, from which it is sent to bulk product storage, the equipment being indicated generally by the reference numeral 500, where it is either delivered directly into lorries for bulk feed or alternatively into 0 8 0 a pre-packing processing operation; the equipment for which is indicated generally by the reference number 600.

It has to be appreciated that the process according to the present invention is a process for the making of pelletised animal feed but that the same plant is also used in the production of many other types of animal feed. Those parts of the plant that are specific to the production of other types of animal feed are not illustrated in the drawings. However, some of the additional equipment that is required is also illustrated in the drawings. Thus, the fact that certain parts of the equipment are not described is because they may be used for other manufacturing processes. Also for ease of understanding, many portions of the plant have had to be separated on the drawings even though in practice they are in close physical proximity. Thus, for example, two conveyors which may feed directly from one onto the other can be shown physically separated on the drawings and merely connected by a line. Such lines may indicate in some instances the use of ducts, piping, etc. and in other instances may indicate simply that one unit feeds directly onto the other. However, since the description of all of these connections would not add anything to an understanding of the invention in general they have been ignored. It is important to note in considering the various drawings that in many instances material or indeed air and steam are often shown as if they were being discharged simply to atmosphere which is not necessarily correct, in most instances additional equipment is used, but again for ease of understanding it is not shown. In many instances in relation to the material it may be that initial start-up material has to be recycled and a batch is taken away in a bin and in other instances it may be because the material can be drawn off at that part of the plant for use in some other process. As would be expected, the air and steam is, in general, led off 94080( through ducts. However, to avoid unnecessary complications, they are merely shown as being removed from the plant.

Referring now to Fig. 2 there is illustrated the raw material storage equipment 100, which comprises fortyseven bulk storage bins 101, eighteen of which are shown, containing various raw ingredients such as wheat, maize, meat meal, fish meal, bone meal, etc.

There is provided two input hoppers 102 and 103 for raw material deliveries respectively feeding conveyors 104 and 105 which feed through a series of chutes 106, and various forms of diverter valve 107, a bin input conveyor 108 which in turn feeds through further valves 107 the bulk storage bin 101.

The material on the input conveyor 104 can be diverted to a magnetic chute 109 for removal of metal from raw material and a cleaner 110 which in turn feeds into the bin input conveyor 108. Similarly material from the input hopper 103 can be diverted to deliver material through another magnetic chute 109 to the bin input conveyor 108.

The bulk storage bins 101 are mounted above three weighers 110 which in turn feed an underhopper 111, delivering onto an output conveyor 112 which in turn feeds a grinding feed conveyor 113.

Referring now to Fig. 3, where the grinding operation plant 200 is illustrated, there is provided a pair of pregrind live bins 201 fed from the grinding feed conveyor 113. The pre-grind live bins 201 feed through feed trays 202 to grinding machines 203 which in turn feed hoppers 204 above conveyors 205, feeding further conveyors 206, 207, 208, 209 and 210. The conveyors 209 and 210 feed the pre-pelletising bins 211 and 212. Output conveyors 213 and 214 are mounted respectively beneath the prepelletising/ extrusion bins 211 and 212. The conveyor 213 feeds a pelletising input hopper 215 and the output conveyor 214 feeds a pelletising input hopper 216 which for clarity are also illustrated in Fig. 3. Numerous diverter valves 217 are used to control the flow of material in the grinding operation. Air filters 218 are mounted above the conveyors 205.

Referring to Fig. 4 where the pelletising equipment 300 is illustrated a pair of mixers 301 each connected by a feeder 302 to a pressure cooker 303 which in turns forms the input for an extruder 304 and an eight blade cutter 305 which in combination form a pelletising plant. Each extruder 304 is of a conventional construction having an end plate perforated with a number of holes through which extrudate is forced. Sometimes as mentioned above such a construction of equipment is called an extruder plant rather than a pelletiser which is the terra used in this specification. Each extruder 304 delivers pelletised feed onto drying input conveyors 306 which feed a dryer input cyclone 307 which again for simplicity is illustrated in both Figs. 4 and 5. Diverter valves 308 are provided which allow flexibility in use of the pelletising equipment 300.

The drying and cooling plant 400 is illustrated in Fig. 5 and includes a dryer, indicated generally by the reference number 401, having an input hopper 402 fed from the dryer input cyclone 307. The dryer 401 includes three pellet support beds namely a top bed 403, (the construction of which is described blow with reference to Figs. 6 and 7) a lower intermediate bed 404 and a bottom bed 405.

The dryer 401 is provided with an output conveyor 406 which in turn feeds a cooler 407 mounted above a bulk delivery conveyor 408 (which is also illustrated for clarity in Fig. 8). The cooler 407 is a conventional air cooler drawing in ambient air which is mixed with the dried hot pellets from the dryer 401. A pair of air heaters 410 and 411 feed the dryer 401 below the top bed 403 and the bottom bed 405, respectively. In turn the hot air is fed from above the top bed 403 and the bottom bed 405 to cyclones 412 and 413, respectively. The cyclones 412 and 413 are exhausted by a recirculation fan 414 into an air mixer unit 415. The air mixer unit is also fed from the cooler 407 via a further cyclone 416 by a cooling fan 417.

Referring now to Figs. 6 and 7 portion of the top bed 403 is illustrated in more detail. The top bed 403 is formed by a number of spaced apart side by side slats 420. Each slat 420 is of stepped construction, comprising a flat upper deck 421 and a flat lower deck 422 projecting on opposite sides of a central connecting rib 423. Each rib 423 is mounted in the dryer 401 by an axle 424. Each axle 424 is, in turn, rigidly connected to one end of a lever arm 425, an opposite end of the lever arm 425 being pivotally connected to an actuator bar 426 which is operated by a ram 427.

Each upper deck 421 and each lower deck 422 is spaced apart from each adjacent upper deck 421 and lower deck 422 respectively forming a number of parallel upper slits 428 and parallel lower slits 429 in the bed 403 which slits are horizontally offset.

The three beds in the dryer are of identical construction. The slats of the top bed and intermediate bed are parallel and the slats of the bottom bed are at right angles to the other slats.

Referring to Fig. 8, there is illustrated the bulk product storage equipment 500 which comprises a plurality of finished product bulk storage bins 501 fed from the bulk delivery conveyor 408 through further conveyors 502 and 503 and a screen 504. The bulk storage bins 501 feed a pellet output conveyor 505 which feeds a bagging plant input conveyor 506. (For clarity this is also illustrated in Fig. 9). Again diverter valves 507 are used to control the flow of material.

Referring to Fig. 9 which illustrates the pre-packing equipment 600 in which there is provided a pair of pellet storage bins 601, fed through a screen 602 and cyclone 603 by the bagging plant input conveyor 506. The pellet storage bins 601 in turn feed a mixer 604. The mixer 604 also has a gravity input from a liquid mixer line 605. The mixer 604 delivers into a conditioning chamber 607 mounted above a feeder conveyor 608 for packing bins 609. The mixer 604 is mounted on load cells, not shown. Packing bins 609 in turn feed weighers 610 mounted above a bagging plant 611 (diagrammatically illustrated by a sketch of a bag) which in turn feeds a palletiser, not shown, via a conveyor 612.

Referring to Fig. 10 there is illustrated a main oil storage tank 613 feeding a main oil day tank 614, provided with a water heater 615, which in turns feeds via a pump 616 a main oil holding tank 617, mounted on load cells 618. Similarly, there is provided a fat day tank 620 feeding a fat holding tank 621 via a pump 622. The fat holding tank 621 is again mounted on load cells 623 and the fat day tank has a heater 624. There is further provided an additional fat day tank 630 also provided with a heater 631, feeding, via a pump 632, an additional fat holding tank 633 again mounted on load cells 634. The three holding tanks 617, 621 and 633 all feed the mixer 604 from above via a liquid mixer line 605.

The operation of the plant, though the various steps of the process has already been described, in broad outline, with reference to Fig. 1, is now described in more detail with reference individually to each of Figs. 2 to 10 inclusive.

In operation and referring to Fig. 2 raw material is delivered into one of the input hoppers 102 or 103 and then either directly or via the magnetic chutes 109 to the bin input conveyor 108 and then into the storage bins 101. As required, the weight of raw material needed for a particular formulation of animal feed is delivered out of each bin 101 into one of the weighers 110, then into the under hopper 111 and onto the output conveyor 112 where it is delivered onto the grinding feed conveyor 113.

Now referring to Fig. 3 the ground raw material is delivered into one of the pre-grind bins 201 from which it is fed into the mixers 203 and hence via the hoppers 204 and conveyors 205, 206, 207, 208 to the conveyor 209. The conveyor 210 is fed from the conveyor 209. The ground raw material is fed from the conveyors 209 and 210 directly to the pre-pelletising bins 211 and 212, respectively. The pre-pelletising 211, 212 deliver via the conveyors 213, 214 to the pelletising input hoppers 215 and 216.

Referring to Fig. 4, the pelletising process is illustrated. The pelletising input hoppers 215 and 216 feed the mixers 301 and 302 where the raw material is mixed prior to being delivered by the feeders 302 to the cookers 303. This is a pressure cooking operation.

The moisture content of the ground raw material when added to the pressure cookers 303 is about 12%. During the pressure cooking, steam is added at up to 181bs/square inch and water is added at 4lbs/minute.

When the material is cooked it is delivered to the extruders 304 where conventional extruding and pelletising is performed. Each cutter 305 operates at 4000 rpm producing 32,000 cuts per hole per minute. The hot pellets leave the extruders 304 at 135°C and 32% moisture. Almost immediately 8% moisture is flashed off the pellets. The majority of this moisture is removed from the surface of the pellets, thus drying the surface of the pellets and preventing the pellets sticking together. The hot pellets are then delivered onto the drying input conveyor 306 at 98°C and 24% moisture.

Referring now to Fig. 5 the drying and cooling operation 400 is illustrated. The hot and wet pellets are delivered from the dryer input cyclone 307 into the dryer 401 via the input hopper 402. The pellets rest on the top bed 403, the operation of which is described in more detail below. Hot air, at approximately 120°C, is delivered by the air heater 410 below the top bed 403. As the hot air is delivered up through the hot pellets it dries the pellets. The air is at substantially dew point as it is delivered out the dryer to the cyclone 412. The wet hot air is then driven by the recirculation fan 414 from the cyclone 412 into the air mixer unit 415. After a pre-set drying time the top bed 403 is opened and the hot pellets fall onto the intermediate bed 404 where they remain for the same length of time i.e. the drying time, being dried statically, without air being pushed directly through them. There will be some flow of air through the intermediate bed 404, however, the main purpose of the intermediate bed 404 is to allow moisture migrate from the still wet centre of the pellets to its outer dried surface. The intermediate bed 404 is then opened and the hot pellets fall down onto the bottom bed 405 where air is delivered for the drying time from the air heater 411 below the bottom bed 405 at approximately 90°C for further drying. The bottom bed 405 is exhausted by the cyclone 413 and recirculation fan 414 to the air mixer unit 415. It will be appreciated that at all times there will be one load, except obviously at starting and stopping the plant, on each of the beds 403, 404 and 405. The dried pellets are then delivered along an output conveyor 406 into the cooler 407, the hot air from the cooler 407 is delivered into the cyclone 416 and then by the cooling fan 417 into the air mixer unit 415. A certain amount of the air in the air mixer unit 415 is exhausted out of it. Thus, in the air mixer unit 415, there is extremely hot air at a temperature of approximately 120°C and at a relatively high humidity, if not dew point, as delivered from the recirculation fan, while warm dry air at a temperature of 40°C from the cooler 407 is mixed with it. This mixture is then delivered to the air heaters 410 and 411 respectively. This arrangement results in a significant saving in energy costs, by mixing the hot air from the cooler 407 with saturated air in the air mixer 415. This heats the air in the air mixer 415 thus increasing the moisture holding capacity of the air.

Referring now to Fig. 6 it can be seen that pellets will rest on the upper decks 421 and a certain amount of pellets will fall through the upper slits 428 onto the lower decks 422. Because of the configuration of the slats 420 the angel of repose of the pellets is such that they will not flow through the lower slits 429.

During the drying operation a small quantity of pellets will rest on each lower deck 422 and within the upper slit 428. The hot air is delivered up through each lower slit 429 above and across the lower deck 422 into the pellets on the lower deck 422 and through the upper slits 428 and the main body of pellets resting on the upper decks 421.

The top bed 403 is opened by moving the ram 427 in the direction of the arrow X. This causes the lever arms 425 940806 1 to pivot each slat 420 into the position illustrated in Fig. 7. In this position the ram 427 is operated to reciprocate the actuator bar 426 and agitate the pellets facilitating their discharge.

The dried and cooled pellets are then delivered out of the cooler 407 onto the bulk delivery conveyor 408.

Referring now to Fig. 8, it will be seen that the cooled pellets are delivered by the conveyor 408, screen 504 and conveyors 502 and 503 into the bulk storage bins 501. The pelleted pet food can then be delivered directly by the pellet output conveyor 505 to the bagging plant input conveyor 506.

Referring now to Fig. 9 where the pre-packing processing is illustrated the bagging plant input conveyor 506 feeds via the cyclone 603 and screen 602 the pellet storage bins 601. The pellets are delivered from the pellet storage bins 601 to the mixer 604 into which is also introduced metered quantities of feed liquid from the liquid mixer line 605. The term feed liquid as used in this specification includes any suitable additive in liquid form namely oils and fats (heated to liquify) and any suitable additive in a liquid state. The pellets are delivered into the bin 601 until the correct volume of feed is in the bin 601, as indicated by the level sensor. It should be appreciated that if the mixer 604 is to operate at optimum efficiency the correct volume of feed must be introduced each time. It is incorrect to just weigh a batch of pellets and feed liquid as the bulk density of a batch of feed pellets can vary significantly. The pellets are then weighed in the mixer 604. The weight of feed liquid required is calculated by the control equipment and the correct weight of feed liquid is added to the mixer 604 from the liquid mixer line 605. The feed liquid is usually at about 55°C prior to addition to the mixer 604. After suitable mixing, usually between 15 and 25 seconds depending on bulk density the pellets are delivered into the conditioning chamber 607 and are held for sufficient time and then delivered by the feeder conveyor 608 into one of the packing bins 609 from which they are delivered through the weighers 610 into the bagging plant 611 onto the conveyor 612 and into a palletiser.

It will be noted that in the above process the mixer 604 is charged with a pre-determined volume of pellets. We have found that using volume controlled batches rather than weight controlled batches greatly improved the texture of the final feed and its consistency. While it was appreciated that mixers usually operate best within clearly defined volumetric limits the improvement in product by operating within these limits and indeed closely to, an optimum volume was surprising. At the same time to get the correct quantity of liquid feed into the mixer quick enough it was found that metering values were not accurate enough and thus again weighing of the liquid feed mixer tank is carried out. Thus there is a unique combination of metering by weight and by volume.

Considerable care and attention is taken to obtaining the appropriate feed liquid as we have discovered that this contributes considerably to the texture of the final feed and somewhat surprisingly there have been reports from veterinary surgeons that the coat or exterior appearance of the animals have been improved by the use of feeds according to the invention. It has also been found that delivering the feed liquid at a temperature within the range 55°C to 70°C facilitates the mixing process.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

Claims (14)

1. A process for making pelletised animal feed comprising the steps of: delivering the raw material to a grinder; grinding the raw material; delivering the ground raw material to a pelletiser mixer; mixing the ground raw material; delivering the mixed material to a cooker; cooking the mixed material; extruding and pelletising the cooked material to form pellets; delivering the pellets onto a top bed of a dryer; carrying out an initial active drying operation by forcing hot air up through the top bed for a pre-set drying time; extracting the hot air from the dryer above the top bed; dropping the pellets onto a lower intermediate bed; retaining the pellets on the intermediate bed for the drying time in a static drying operation; 94 08 Ο 6 dropping the pellets onto a bottom bed; carrying out a final active drying operation by forcing hot air up through the bottom bed for the drying time; extracting the hot air from the dryer above the bottom bed and below the intermediate bed; delivering the dried pellets to an air cooler; cooling the pellets; and delivering the dry pelletised animal feed to bulk storage bins .

2. A process as claimed in claim 1 in which the hot air is forced up through lower elongated slits into a bed, across within the bed and out of the bed through upper elongated slits, said upper elongated slits being offset from the lower elongated slits.

3. 3. A process as claimed in claim 1 or 2 in which the hot air from each active drying operation is provided by mixing some of the wet hot air delivered out of the dryer with hot air from the cooler.

4. A process as claimed in claim 3 in which the ratio of recycled air from the dryer to that from the cooler is within the range 10:1 to 4:1.

5. A process as claimed in any preceding claim in which an individual air heater is provided for each active drying operation.

6. A process as claimed in any preceding claim in which the air extracted from the dryer and cooler is first delivered through a cyclone to extract entrained fines.

7. A process as claimed in any preceding claim in which the moisture content of ground raw material introduced into the cooker is within the range 9% to 15% by weight.

8. A process as claimed in claim 7 in which the moisture content of ground raw material introduced into the cooker is 12% by weight.

9. A process as claimed in any preceding claim in which the raw material on cooking has a moisture content within the range 25% to 40% by weight and a temperature within the range 125°C to 145°C and which on delivery out of the extruder moisture is flashed off so that the moisture content of the pellets is reduced by 4% to 10% by weight.

10. A process as claimed in claim 9 in which the raw material on cooking has a moisture content of 32% by weight and a temperature of 135°C and which on delivery out of the extruder moisture is flashed off so that the moisture content of the pellets is reduced by 8% by weight.

11. A process as claimed in any preceding claim in which there is performed the additional steps of: delivering a pre-determined volume of pelletised animal feed to a mixer from the bulk storage bins; weighing the feed in the mixer; weighing batches of feed liquid; adding the batches of feed liquid to the mixer until a predetermined weight is achieved; mixing the animal feed and oil to coat the feed; delivering the treated animal feed into a conditioning bin; holding the animal feed in the conditioning bin for a predetermined lay time; delivering the animal feed to a storage bin; and delivering the animal feed from the storage bin to a bagging and pelletising plant.

12. A process as claimed in claim 11 in which the feed liquid is heated within the range 45°C to 75°C prior to addition of the mixer.

13. A process as claimed in claim 7 in which the feed liquid is heated within the range 55°C to 60°C.

14. A process for making pelletised animal feed substantially as hereinbefore described with reference to the accompanying drawings.