GB1604381A - Feedstuffs for animals - Google Patents

Description

(54) FEEDSTUFFS FOR ANIMALS (71) We, UNILEVER LIMITED, a British company, of Unilever House, Blackfriars, London, EC4, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to feedstuffs, and to the manufacture thereof, suitable for ingestion by small animals which require their diet to include granules having a maximum dimension falling within the range 300 to 2000 microns. In general these animals are aquatic, for example young fish, crustacea and mollusca, but in addition small birds such as newly hatched poultry can require feedstuffs comprising granules having sizes falling within this range.

No wholly satisfactory feedstuffs intended for young fish and other small aquatic animals are available commercially at present. Much work has been done on the nutritional requirements of various fish species, and in general the overall compositions of commercially available feedstuffs for such creatures are good. However, in terms of their compositional uniformities and of their physical properties there is much room for improvement. Conventionally, feedstuffs for fish are prepared by pelleting, crushing and screening a blend of ingredients. Such feedstuffs do not have good flow properties because the crushed pellets, usually referred to as crumbles or granules, have jagged edges, often have oily surfaces, and feature a wide range of sizes. Moreover, unless the individual ingredients of the feedstuff are milled very finely prior to pelleting, it is likely that the granules will not have a uniform composition because there is a tendency for the pellets to break down into the primary particles from which they were made. In the crushing operation there can be little or no control over the size range of the granules produced and thus much material has to be recycled, or is wasted, following screening. Many conventional feedstuffs for fish are deliberately formulated to include a substantial level of oil which the fish can use as an energy source. The presence of this oil, whether added to the formulation as free oil or inherently in fish meal upon which many feedstuffs are based, does nothing to enhance the flow properties of the resulting product. Due to their poor flow properties, conventional feedstuffs for fish do not readily lend themselves to the use of labour-saving automatic dispensing equipment at feeding sites. A marked lack of compositional uniformity can give rise to problems of poor health and inadequate growth in many members of a fish population reared in captivity on artificial feedstuffs.

Similar problems of poor flow and inadequate compositional uniformity can arise in poultry feedstuffs, even though such feedstuffs do not typically contain oil levels of the magnitude found in fish feedstuffs.

In British Patent Specification No. 1226799 there is described a method of manufacturing feedstuffs in the form of spherical granules having diameters in the range 1000 to 6000 microns by the steps of delivering a particulate ground food material onto a supporting surface of a rotating support element inclined to the horizontal plane at an angle in the range 30 to 50 degrees, and spraying a liquid (water, perhaps containing micro-additives or vitamins) onto the particulate material located on the surface of the support element so that the particulate material is subjected to granulation. The principal advantage claimed for the process as described is that it leads to greater compositional uniformity, and in particular that microadditives and vitamins are evenly distributed in the granulated feed.

It is undoubtedly true that the process as described in British Patent Specification No. 1226799 can lead to greater compositional uniformity than the conventional process already described above. However in the description in British Patent Specification No. 1226799 no mention is made of the flow problems associated with conventional feedstuffs and no claim is made that the granulated product made in accordance with the process described has flow properties superior to those of conventional fish or poultry feedstuffs. Further the process as described does not apparently provide granules having a diameter less than 1000 microns.

The granulation technique utilised in the process described in British Patent Specification No. 1226799 is an example of the procedure commonly referred to as pan granulation or disc pelletising. The essence of such a procedure is that a tumbling bed of finely divided substrate is sprayed with a liquid, and the continued tumbling motion of the moistened substrate particles causes the particles to agglomerate into granules. A typical pan granulator is a right cylindrical vessel open at one end and rotatable about the axis of the cylinder, which axis is generally held, during operation, at an angle of 20 to 40 to the horizontal such that the open end of the vessel is uppermost. The pan is charged with finely-divided particulate substrate, which forms a tumbling bed of powder when the pan is rotated. In a typical pan granulator the sneed of rotation of the pan can be varied, stepwise, from about 10 rpm to about 50 rpm. The pan can be fitted with internal baffles which affect the tumbling motion of the substrate.

Despite the undoubted advance in the art which the procedure described in British Patent Specification No. 1,226,799 represents, namely helping to solve the problem of composition uniformity found in the conventional foodstuffs, we have found that the simple concept of manufacturing a feedstuff in a moistened tumbling bed of substrate using water alone as the agglomerating liquid, to produce rounded granules, does not in itself solve the major problem of poor flow exhibited by the conventional feedstuffs This is particularly true for feedstuffs having granule sizes towards the lower end of the range to which the invention relates because such flow problems increase dramatically in inverse proportion to the size of the individual granules.

A further disadvantage associated with the use of water alone as the agglomerating liquid is that this can lead to wide size distributions in the granulated products so obtained, and in consequence poor yields of granules in the size ranges with which this invention is concerned, making the process less economic By the invention we are able to produce a granulated feedstuff, suitable for ingestion by small animals, which has flow properties superior to those associated with conventional feedstuffs of similar granule size made by crushing pellets.

The invention provides a process for the preparation of a feedstuff for small animals which require their diet to include granules having a maximum dimension in the range 300 to 2000 microns, in which process a bed of finely-divided essentially solid feedstuff ingredients, having a mean particle size (Rosin Rammler) not greater than 500 microns, is tumbled in a pan-granulator and the tumbling bed is granulated by spraying thereon an aqueous solution of a non-toxic polymeric material, the resulting granulated is dried to a moisture content of less than 15 by weight, and the granulated product is physically classified to ensure that it contains not more than 10% by weight of granules having a maximum dimension of less than 300 microns.

A particular embodiment of the invention is a pan-granulated feedstuff for small animals, comprising granules of which at least 80% by weight have a maximum dimension of at least 300 microns but not greater than 2000 microns, but with not more than 10% by weight of the granules having a maximum dimension of less than 300 microns, exhibiting consistently a Flow Performance rating of not worse than 2 as determined using the test procedure hereinafter described. Such a product can be produced easily using the process of the invention.

A further embodiment of the invention is an animal feedstuff in the form of granules of which at least 80% by weight have a maximum dimension of at least 300 microns but not greater than 2000 microns, but with not more than 10% by weight of the granules having a maximum dimension of less than 300 microns, the granules having been prepared by agglomerating finely-divided essentially solid feedstuff ingredients, wherein the feedstuff contains at least 5% by weight of oil and exhibits consistently a Flow Performance rating of not worse than 2 as determined using the test procedure hereinafter described. Such a product can also be produced easily using the process of the invention.

The use of a pan granulator in the granulation step leads to the production of granules that are predominantly spherical in form, in other words although it is unlikelv that many of the granules will be truly spherical, nonetheless few, if any, of them will have any significantly angular surfaces and thus at least the bulk of the granules will have a well-rounded cross-section in every dimension.

The process of the invention also leads to a substantially uniform composition in the individual granules. When a feedstuff comprises small granules prepared from several ingredients, it is clearly unrealistic to expect that every single granule will contain every ingredient, and especially every ingredient in the proportions in which such ingredients occur in the feedstuff as a whole. Nevertheless, it is possible to use the invention to prepare a feedstuff in which at least 50% by weight of the granules individually contain each major ingredient of the formulation. Thus at least 50% by weight of the granules individually represent a "mouthful" of feed which is not totally unbalanced. Preferably at least 70% and ideally at least 90%, by weight of the granules individually meet this requirement. In view of the problem experienced with conventional feedstuffs that the flow properties deteriorate as the mean granule size is decreased, it is significant that the invention can still provide feedstuffs having good flow properties where at least 80% by weight of the granules have a maximum dimension not greater than 1400 microns, and even where at least 80% by weight of the granules have a maximum dimension not greater than 1000 microns. An imnortant embodiment of the invention is a feedstuff comprising granules of substantiallv uniform composition which contains no granules having a maximum dimension of 1000 microns or above, and not more than 10%, preferably not more than 5%, by weight cf granules having a maximum dimension of less than 300 microns, and which has a Flow Performance of not worse than 2.

By providing feedstuffs having enhanced flow properties the invention is particularly beneficial in the context of feedstuffs, usually intended for fish, which contain at least 5%, and particularly at least 10%, by weight of oil. Some or all of this oil can be present due to the use of oil-containing fish meal as a constituent of the feedstuff. An important embodiment of the invention is a feedstuff comprising at least 30%, and preferably at least 50%, by weight of fish meal. Where the fish meal contains 5%, or more, by weight of oil, the invention still results in a granular product having excellent flow properties.

It will be appreciated that in order to fabricate a granule of substantially uniform composition and small diameter, the particle size to which the individual solid components of the substrate should be subdivided needs to be very much smaller. Ideally, the individual components of the substrate should be used at an average particle size not exceeding 35% of the mean granule size required in the feedstuff. When the individual components of the substrate cannot be purchased ready-milled to an appropriate particle size, they should be milled prior to use. Commercially available fine milling equipment, such as a swing hammer mill, is quite suitable for this operation. Preferably the mean particle size (Rosin-Rammler) of the ingredients in the tumbling bed is not greater than 300 microns. It is also preferred that the mean particle size of the ingredients is not less than 100 microns. A sa general rule, it is also desirable that the particle size spread (Rosin-Rammler) of any ingredient which comprises at least 30% by weight of the tumbling bed is not less than 0.9, preferably not less than 1.0 an ideally not less than 1.2. This careful control of the particle size of the major ingredients of the tumbling bed plays an important role in ensuring good flow properties in the granulated product. Rosin-Rammler particle analysis is a standard technique, and a good introduction can be found in Journal of the Institute of Fuel, October 1933, pages 29-36. The constant "n" referred to in this journal article corresponds to the particle size spread" as used in this specification.

It should be recognised that not all particulate materials fit the theories upon which the Rosin-Rammler analysis is based, but we have found that in the context of the invention the conventional ingredients used in feedstuffs for fish and poultry generally behave in a manner which accords very well with Rosin-Rammler theory, and thus in this context the application of Rosin-Rammler principles provides a practical guide.

The non-toxic polymeric material which is applied to the tumbling bed via the sprayed aqueous solution is a key feature of the invention, as we have found that it plays a major role in the production of good yields of small granules within the size range required. Edible gums of animal or vegetable origin can be used, but the nontoxic polymeric materials can also be, for example, proteins which would not usually be regarded as gums: casein is a good example. Preferred gums are gelatins, and edible water-soluble polysaccharides such as alginates, particularly sodium alginates, but other gums such as guar gum, locust bean gum and gum arabic can be used.

Alternatives are: starches and degraded starches such as dextrins, and substituted celluloses such as carboxyalkyl celluloses, e.g. sodium carboxymethyl celluloses, and alkvl celluloses e.g. methylethyl celluloses and methylhydroxyethyl celluloses. Watersoluble synthetic polymers, such as polyacrylamides, polyacrylates, polyvinylalcohol and polyvinylpropylene can also be used. It will be appreciated that all of these commercially available polymeric materials can be obtained in a range of molecular weights, and that their aqueous solutions can have very different viscosities. Hence it is not possible to give definitive concentration ranges in which these materials should be present in the aqueous solution used to agglomerate a feedstuff of the invention.

At one extreme, of course, the viscosity of the aqueous solution should not be so high that it is impossible to spray it under practical operating conditions. The minimum concentration, on the other hand, is dictated by the requirement that the polymer should be present in sufficient quantity to give rise to a discernible effect on the particle size distribution of the granulated product. It will be self-evident to any skilled reader than the setting up of a process in accordance with the invention will necessarily involve a number of trial runs, and this will include a check on the optimum concentrations at which the particular polymer chosen should be used. However, as a guide, we have found that for gelatins and casein the concentration in the aqueous solution will generally need to be at least 3%, and usually not more than 30%, by weight, and a typical operating range for these polymers will be 5-20% by weight For sodium alginate the concentration will generally be at least 0.1%, and usually not more than 2%, by weight, with an optimum range of typically 0.51.5%. For sodium carboxymethylcellulose the concentration will generally be in the range 0.15% by weight. By way of comparison, for the synthetic polymers, such as polyacrylamides, an optimum range can be 30-200 ppm, typically 50-100 ppm. Mixtures of more than one polymeric material can be used.

The volume of the aqueous solution applied to the tumbling bed will generally be in the range 15 to 40%, expressed by weight of the dry bed.

In general the aqueous solution can be applied to the tumbling bed at ambient temperature. However, for concentrated solutions of certain polymers, such as gelatin, which would set at ambient temperature, the solution should be maintained at a temperature above the gel point of the solution. For gelatin solutions, an operating temperature of about 60"C is ideal.

In addition to the non-toxic polymeric material, the aqueous solution that is applied to the substrate can contain one or more minor components of the feedstuff, such as vitamin or medicaments.

The aqueous solution is applied to the substrate in the form of a spray of very fine droplets. The aqueous solution should be fed at high pressure to a spray nozzle directed onto the tumbling bed of substrate particles. Different spray nozzles obtained from different manufacturers will probably need to be operated at different working pressures, and no specific advice can be given on this point. However, in general the working pressure will lie in the range 20 to 100 psi.

Typically, after the aqueous solution has been applied to the substrate and an adequate degree of granulation has been achieved, the water content of the granulated feedstuff will be of the order of 20 to 35% by weight Preferably the granulated feedstuff should be dried to a water content of not greater than 12%, ideally not greater than 10%, by weight, to inhibit the growth of moulds and other microorganisms during storage. Drying should be conducted under mild conditions, so that proteins and other delicate ingredients in the feedstuff are not unduly affected.

With this proviso, the techniques used for drying a.:e not critical.

The substrate in the tumbling bed can be any combination of the essentially solid materials normally incorporated in fish feeds or poultry feeds. These are described in detail below. In addition, any oily component can be present in the substrate if desired, provided that the overall liquid level in the substrate prior to granulation is not so high that the substrate will not form a freely-tumbling bed when placed in the rotating granulator.

In general, feedstuffs for fish are characterised by a high protein content and by a substantial proportion of the energy source being oil. A typical fish feed can comprise, by weight, at least about ^3%, preferably at least about 40% and generally not more than about 80%, protein; up to about 40% carbohydrate; up to about 20% oil; and a variety of minerals and vitamins together contributing up to about 15% of the fish feed. During the granulation, and especially during any subsequent drying operation, the temperature should be kept as low as possible to prevent undue denaturation of the protein content of the fish feed. Temperatures not exceeding about 600 C, and preferably not exceeding about 500 C, should be aimed for.

Suitable protein sources include: fish meals, of which the commonest in use are herring meal and anchovy meal; liver meal; oil seed meals, such as soya meal and cottonseed meal; single cell proteins and yeasts; blood meal; whey powder and skimmed milk powder; casein; gelatin; distillery by-products; and meat meal. A preferred substrate contains at least 40% by weight fish meal.

Carbohvdrates are generally present as cereals, such as: wheat germ meal, wheat bran and whole wheat meal; maize; barley; millet; oats; and rice.

The oils used are usually: vegetable oils such as corn oil, soya bean oil and groundnut oil; and fish oils such as herring oil, capelin oil and cod liver oil.

The usual mineral sources are bone meal, di-calcium phosphate and limestone.

Sodium chloride and cupric sulphate are also generally present. In addition, a wide range of vitamins should be present, such as vitamins A, B1 (thiamine), B2 (riboflavine), B2 (pantothenic acid), B12, C, D, E and K.

It will be appreciated that the individual ingredients which are blended together to make up a feedstuff are often themselves complex mixtures, and thus can contribute to more than one of the above ingredient categories. It has already been mentioned that fish meals can contain oil. A carbohydrate source such as a cereal can contribute significantly to the total protein content of the feedstuff. Most natural ingredients will contribute some trace elements and vitamins.

In general, poultry feeds are produced from the same broad classes of ingredients, except that the total oil levels will be lower, and greater quantities of carbohydrates such as milled grain will be used. In the manufacture of a feedstuff intended for poultrv, the principles of the invention will apply just as in the case of a feedstuff for fish.

After granulation of the feedstuff, and drying as required to reduce its water content to less than 15% by weight, it will usually be necessary to physically classify the granulated product to remove any significant quantities of undersize or oversize granules. In some instances it will be appropriate to divide the product into distinct size fractions, particularly where feedstuffs for fish are concerned. For example, feedstuffs for young fish such as salmon and trout can be obtained by fractionating a grandulated product of the invention into a "small" fraction wherein at least 80% by weight of the granules have a maximum dimension in the range 300 to 850 microns, and a "large" fraction suitable for slightly older fish wherein at least 80% by weight of the granules have a maximum dimension in the range 850 to 1400 or 1700 microns.

A particularly useful embodiment of the invention is a feedstuff for fish, especially young salmon and trout, comprising rounded granules of substantially uniform composition, at least 95% by weight of which have a maximum dimension of at least 355 microns but not greater than 850 microns but wherein none have a maximum dimension in excess of 850 microns, the feedstuff having a Flow Performance rating of not worse than 2 as determined using the flow test described herein. The figures of 300, 355, 850, 1400 and 1700 microns come from Standard Sieve sizes, which we have used for classifying our feedstuffs. 850 microns is a convenient cut-off between the fractions, but the next lower sieve (710 microns) can be employed instead. It should be pointed out also that the manner in which the sieving is performed can affect the results obtained, and all particle sizes expressed in this specification relate to sizes as determined using Standard Sieves in the manner laid down in British Standard 1796 of 1952. Commercial sieving operations can lead to errors of up to 5% at least in the apparent sizes recorded.

Flow Performance Test.

Automatic dispensers for fish feeds generally incorporate a storage container out of which small quantities of the feed can flow under gravity when the dispenser is actuated. If the feed has a poor flow performance, this shows uo because the feed tends to flow erratically through the container outlet, or to "bridge" and block the outlet completely. A typical fish feed dispenser incorporates a funnel-shaped container, closable at or near the lower (outlet) end by means of a slidable door which is moved wholly or partially out of the way when release of feed from the container is required. After leaving the funnel, the feed can be distributed by a variety of physical methods: the current problem of poor flow manifests itself before the feed has left the funnel.

A test rig to quantitatively assess the Flow Performance or a fish feed can be set up on similar principles, and is illustrated in the accompanying drawings, of which Figure 1 represents a cross-sectional elevation of a complete test rig, and Figure 2 represents a lateral cross-section taken on the line A-A of Figure 1. The test rig comprises a conventional polyethylene laboratory filter funnel 1, having a maximum diameter of 20 cm and a cone angle of 60 , and with the spout 2 cut away 4 cm below the bottom of the cone 3. Funnel 1 is held by means of a standard laboratory clamp represented by 4 such that the axis 5 of the funnel is vertical and the spout 2 is pointing downwards. The spout 2 is closed with a horizontally-slidable door 6. The construction and location of door 6 is shown in Figure 2. Door 6 is elongate and has a width slightly less than that of the outside diameter of spout 2.

Spout 2 is perforated by two narrow opposing horizontal slots 7 and 8, each just sufficiently large to accommodate the width of door 6. Hence two thin webs, 9 and 10, are left in the spout 2, separating the slots 7 and 8 and linking spout 2 above and below the slots. Door 6 is perforated by a circular hole 11 of diameter slightly less than the inside diameter of spout 2. Door 6 is supported in slots 7 and 8, and longitudinal movement of the door (along line A-A) can bring hole 11 within or without spout 2, so opening or closing the passage through the spout. In the actual test rig used in the following Examples, the dimensions associated with the door were as follows: door 38 mm X 18 mm, hole diameter 13 mm, spout internal diameter 15 mm, spout extemal diameter 23 mm.

A quantity of the granulated feedstuff, sufficient to half-fill the funnel, is loaded into the funnel while the door is maintained closed. The door is opened, and the ability (or otherwise) of the fish feed to flow out under gravity through the spout of the funnel is observed.

Relative Flow Performances of different feedstuffs can be assessed by simply classifying the Flow Performance according to the following scale, discharge of the funnel being aided as necessary by tapping the base of the funnel cone using a lightweight hand-held implement such as small laboratory spatula.

Flow Performance Rating Free and unaided discharge 1 Discharges completely with only one tap required 2 Erratic discharge: several taps required 3 No unaided discharge: constant tapping required 4 No discharge at all 5 In practice this test procedure is accurate and reproduceable, even though it may not seem so when described on paper. The initial quantity of material in the funnel is sufficient to overcome any variation introduced by the operator through the relative force applied when tapping the funnel. Any tendency for the feedstuffs under test to block the funnel outlet should manifest itself long before the funnel has emptied.

The test should, of course, be carried out in a fair manner, using a clean dry funnel and ensuring that the feedstuffs being tested do not have excessive moisture contents.

As an indication of the meaning of these flow ratings, conventional fish feeds having granules in the 300-2000 micron range and made by crushing pellets will exhibit a Flow Performance of no better than 3, and more usually 4-5, when subjected to the above test.

The following Examples illustrate the manufacture of granulated feedstuffs in accordance with the invention.

Example 1.

A substrate was prepared from the following ingredients: Ingredient % by weight Fish meal (oil content 9%) 68 Skimmed milk powder 13 Vitamin/mineral mixture 10 Edible oils 9 The fish meal had been milled using a Mikropul Bantam swing hammer mill to a mean particle size of 140 microns and a particle size spread of 1.72 (Rosin Rammler), a sieve analysis of the milled fish meal giving the following figures: Particle size (microns) % by weight of sample > --500 300-500 4 150-300 25 75-150 42 45-75 25 I < 45 4 The vitamin-mineral mixture was milled using the same apparatus. The skimmed milk powder was purchased commercially and used unmilled as it was sufficiently fine already.

The particulate substrate was prepared by blending the above ingredients in a standard Hobart (Registered Trade Mark) powder mixer.

The substrate was then granulated in a 75 cm diameter pan granulator. 25 kg of the substrate was tumbled in the pan, held at 30 to the horizontal and rotated at about 20 rpm, and 8 litres of an aqueous solution, containing 18% by weight gelatin (120 Bloom grade ex Croda) and maintained at 60eC, was sprayed onto the substrate via a Delavan-Watson WG 2006 cone nozzle at a working pressure of 60 psi.

After granulation and discharge from the pan, the resulting product was dried at 50"C for 19 hours in a tray oven, its final water content being about 10% by weight.

The dried product was sieved to yield the following fractions:

After granulation and discharge from the pan, the resulting product was dried in a tray oven at 500C for 1 hour, the final water content being about 10% by weight.

The dried fish feed was sieved to yield the following fractions: Particle size (microns) % by weight of product > 2000 1 2000-1400 24 710-1400 45 355-710 25 1 < 355 5 Even the "small" particle size fraction (355-710 microns) exhibited a rating of 1 when subject to the Flow Performance test.

Example 3.

A substrate was prepared from the following ingredients: Ingredient % by weight Fish meal (oil content 7.2%) 68 Vitamin/mineral mixture 10 Skimmed milk powder 13 Edible oils 9 The fish meal and the vitamin/mineral mixture were made into a pre-mix, and milled by being passed twice through a Christy-Norris swing hammer mill (Type B/7/2), which gave the pre-mix a mean particle size of 300 microns and a particle size spread of 2.3 (Rosin-Rammler). The milk powder and the edible oils were then blended with the milled pre-mix using a standard Hobart powder mixer.

5 kg of the substrate was loaded into a 50 cm diameter pan granulator, and granulated and dried using the processing conditions of Example 2 with the exception that in place of the aqueous gelatin solution, 1.8 litres of an aqueous solution containing 80 ppm polyacrylamide (F50 ex Crosfields, having a MW of 13 X 105 and 20% anionic character) at ambient temperature (approximately 20or) was used.

The dried granulated product had the following sieve analysis: Granule size (microns) % by weight of product > 2000 9.0 1700-2000 13.1 850-1700 41.7 355- 850 36.2 , < 355 The 355-850 micron fraction exhibited a rating of 2 in the Flow Performance test. The 850-1700 micron and 1700--2000 micron fractions had ratings of 1.

Example 4.

The process of Example 3 was repeated, using a further 5 kg of the same substrate and the same granulation and drying conditions, but on this occasion the aqueous solution contained 1.5% by weight sodium alginate (Manutex RS-Registered Trade Mark-a readily soluble technical grade ex Alginate Industries). The dried granulated product had the following sieve analysis: Granule size (microns) % by weight of product > 2000 5.0 1700--2000 15.5 850-1700 54.0 355- 850 24.7 < 355 0.8 The 355-850 micron fraction had a rating of 2 in the Flow Performance test, and the larger size fractions a rating of 1.

Example 5.

A further 5 kg of the substrate of Example 3 was granulated and dried under the same conditions, but using an aqueous solution containing 1C./. by weight of a high purity food grade sodium alginate (Manucol KMF-Registered Trade Marker Aiginate Industries). On this occasion the dried granulated product had a sieve analysis as follows: Granule size (microns) % by weight of product > 2000 6.0 1700--2000 13.0 850-1700 45.8 355-850 34.9 1 < 355 0.3 Example 6.

Each fraction in the 355-2000 micron range had a rating of 1 in the Flow Performance test.

A substrate identical in composition and particle size to that used in Example 1 was converted into a granulated feedstuff under the following processing conditions.

5 kg of the substrate was placed in a 50 cm diameter pan granulator and tumbled while the pan was held at about 300 to the horizontal and rotated at about 20 rpm. The substrate was sprayed with 1.8 litres of an aqueous solution containing 5% by weight gelatin (120 Bloom grade ex Croda) maintained at 600 C, using a Delavan-Watson WG 356 cone nozzle at a working pressure of 40 psi. The granulated product was dried in a tray oven at 500C to a water content of about 10% by weight, and was sieved to yield the following fractions: Granule size (microns) % by weight of product > 2000 0.4 200191400 8.5 850-1400 18.9 355- 850 n.2 1 < 355 The 355-850 micron fraction exhibited a rating of 1 when subjected to the Flow Performance test.

Example 7.

A substrate was prepared having the following composition: Ingredient % by weight Fish meal (oil content 4.2%) 68 Vitamin/mineral mixture 10 Skimmed milk powder 13 Edible oils 9 The fish meal and the vitamin/mineral mixture were both milled by being passed twice through a Christy-Norris swing hammer mill (Type B/7/2), and the milled fish meal had a mean particle size of 290 microns and a particle size spread of 2.6 (Rosin-Rammler). The substrate ingredients were blended in a standard Hobart (Registered Trade Mark) powder mixer.

5 kg of this substrate was granulated using a procedure exactly analogous to that of Example 6. The dried granulated product had the following sieve analysis: Granule size (microns) % by weight of product > 2000 6.0 1400-2000 17.5 850--1400 21.4 355- 850 58.1 ! < l 355 3.0 The 355-850 micron fraction exhibited a rating of 2 when subjected to the Flow Performance test, the larger granulate size fractions having ratings of 1.

Example 8.

A further 5 kg of the substrate as used in Example 7 was granulated and dried using the procedure of Example 6, with the exception that in place of the gelatin solution 1.8 litres of an aqueous solution containing 1% by weight sodium carboxymethyl cellulose (Courlose* F350 ex Courtaulds) maintained at 600C was used.

The dried granulated product had the following sieve analysis: * Registered Trade Mark.

Granule size (microns) % by weight of product > 2000 1.0 1400-2000 9.1 850--1400 32.4 355- 850 55.3 l 350 2.2 The 355-850 micron fraction was given a rating of 2 in the Flow Performance test, with the larger fractions each a rating of 1.

Examples 9 and 10.

Two 5 kg samples of the substrate as used in Example 1 were each granulated in a 50 cm diameter pan granulator held at 300 to the horizontal and rotated at about 20 rpm. The agglomerating solution used in each case was 2 litres of an aqueous solution containing 5% by weight casein at ambient temperature. In each case the working pressure was 40 psi, but the procedures differed in that in Example 9 a Delavan-Watson WG 356 nozzle was used, and in Example 10 the nozzle was a Dplavan-Watson WG 606. After granulation, the product in each case was dried at 500C for 1 hour. The following sieve analyses of the two products obtained illustrate the fact that the granule size distribution of the product can be varied by choosing different nozzle specifications: % by weight of product Granule size (microns) Example 9 Example 10 > 1400 9.5 4.5 850--1400 5.7 11.2 500- 850 20.0 50.4 355- 500 58.1 25.5 t < 355 6.7 8.4 In both Examples, the combined 355-850 microns fraction had a rating of 1 in the Flow Performance test Example 11.

All of the preceding Examples were performed using a "batch" process, but the invention can be put into practice equally effectively using a "continuous" style of operation, as this Example illustrates.

A 30 kg stock of substrate, identical in every respect to that used in Example 1, was prepared, together with 10 litres of an aqueous solution containing 10/0, by weight of sodium alginate (Alginate KMF) for use as the agglomerating liquid. A 50 cm diameter pan granulator, set at an angle of 30 to the horizontal and to run at 20 rpm, was fitted with a standard automatic substrate feeder. The spray head was fitted with a Delavon-Watson WG 606 nozzle, to which the alginate solution could be fed at a working pressure of 60 psi. The nozzle was directed towards the back of the pan from the "5 o'clock" position relative to the rim of the pan.

An initial substrate charge of 5 kg was loaded into the rotating pan. From experience it was known that 1.8 litres of this particular agglomerating solution would yield a good granulated product from 5 kg of substrate under these conditions, so this amount of solution was sprayed onto the tumbling bed initially. When granulation of the initial charge was seen to be taking place satisfactorily, the substrate feeder and spray head we set running continuously, the rate of addition of substrate to the pan being adjusted to match the rate of addition of solution, i.e. about 5 kg per 1.8 litres. The granulated product discharged over the front of the pan, and was removed to a drying oven at 50"C. After about 20 minutes of continuous operation, all of the solution had been expended, and addition of substrate was stopped. The amount of substrate used up was 27.5 kg.

A random sample of the granulated dried product was sieved, yielding the following fractions: Granule size (microns) % by weight of product > 2000 1400-2000 24.6 850-1400 42.0 355-- 850 31.4 1 < 355 2.0 The absence of any granules above 2000 microns illustrates a characteristic of continuous operation: it results in a product having a narrower particle size spread and a reduced proportion of oversize granules. During continuous operation, large granules come to the front of the pan and discharge, so the granulator is in effect self-classifying and there is less tendency for a build-up of unduly large particles to occur, whereas such a build-up can occur in a batch operation where the granulated product is retained in the pan.

Each major fraction of the granulated product was given a rating of 1 in the Flow Performance test.

Example 12.

The continuous process of Example 11 was repeated, with the exceptions that the aqueous solution used was a 5 /O by weight gelatin (120 Bloom grade ex Croda) solution, held at 60"C and fed at 40 psi to the tumbling bed at a rate of 1.9 litres per 5 kg of substrate. The dried granulated product had the following sieve analysis: Granule size (microns) % by weight of product > 2000 1400-2000 12 850-1400 24 355- 850 60 l < l 355 4 The absence of any granules above 2000 microns is again a feature. Each of the major fractions had a rating of 1 in the Flow Performance test.

Example 13.

This Example demonstrates the technical advantages of the invention compared with a process analogous to that described in British Patent Specification No. 1,226,799 wherein water alone is used as the agglomerating liquid.

A substrate was prepared by firstly blending 2 parts by weight fish meal having an oil content of 10.3% by weight with 1 part by weight of fish meal having an oil content of 3.9 /, by weight, milling the fish meal blend in a Christy-Norris swing hammer mill (Type B/7/2) to a mean particle size of 300 microns and a particle size range of 1.5 (Rosin-Rammler) and then using the milled fish meal blend in a substrate formulation as in the previous Examples, namely: Ingredient % by weight Fish meal blend 68 Vitamin/mineral mixture 10 Skimmed milk powder 13 Edible oils 9 Two 5 kg batches of the substrate were granulated as follows: In the first granulation, the substrate was placed in a 50 cm diameter pan granulator, set at an angle of 300 to the horizontal and rotating at about 20 rpm, and sprayed with 1.6 litres of an aqueous solution containing 15% by weight gelatin (120 Bloom grade ex Croda) maintained at 60"C, via a Delavan-Watson WG 606 nozzle at a working pressure of 60 psi. The granulated product was dried in a tray oven at 500C to a water content of about 12% by weight.

In the second granulation, the procedure used was identical except that in place of the gelatin solution, 1.6 litres of pure water at ambient temperature (about 20"C) were used.

The two dried products had the following sieve analyses: % by weight of product Granule size (microns) Example 13 Comparative > 2000 3.3 10.5 1400-2000 3.7 4.0 850--1400 33.3 17.9 333- 850 58.3 32.0 ! < 355 1.4 35.6 These sieve analyses indicate that the process of the invention produced a much higher yield of granules in the target ranges of 355--850 microns and 850--1400 microns. In the Comparative Example, there is an undesirably high proportion of oversize granules ( > 2000 microns) and an unacceptably high proportion of fines ( < 355 microns) which would have to be re-cycled, as this represents largely un-agglomerated material because the substrate mean particle size was about 300 microns. Thus the Comparative process is clearly inefficient and wasteful.

The advantages of the process of the invention were demonstrated even more dramatically when the two products were subjected to the Flow Performance test.

The 355--850 micron fraction of Example 13 was given a rating of 2, but that of the Comparative Example had a rating of only 4 and on this basis would have been almost useless in an automatic feeding device.

WHAT WE CLAIM IS: 1. A process for the preparation of a feedstuff for small animals which require their diet to include granules having a maximum dimension in the range 300 to 2000 microns, in which process a bed of finely-divided essentially solid feedstuff ingredients, having a mean particle size (Rosin Rammler) not greater than 500 microns, is tumbled in a pan granulator and the tumbling bed is granulated by spraying thereon an aqueous solution of a non-toxic polymeric material, the resulting granulated product is dried to a moisture content of less than 15% by weight, and the granulated product is physically classified to ensure that it contains not more than 10% by weight of granules having a maximum dimension of less than 300 microns.

2. A process according to Claim 1, wherein the mean particle size (Rosin Rammler) of the ingredients in the tumbling bed is not greater than 300 microns.

3. A process according to Claim 1 or Claim 2, wherein the mean particle size (Rosin Rammler) of the ingredients in the tumbling bed is at least 100 microns.

4. A process according to any one of Claims 1 to 3, wherein the particle size spread (Rosin Rammler) of any ingredient which comprises at least 30% by weight of the tumbling bed is not less than 0.9.

5. A process according to Claim 4, wherein the particle size spread (Rosin Rammler) is not less than 1.0.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (47)

**WARNING** start of CLMS field may overlap end of DESC **. particle size range of 1.5 (Rosin-Rammler) and then using the milled fish meal blend in a substrate formulation as in the previous Examples, namely: Ingredient % by weight Fish meal blend 68 Vitamin/mineral mixture 10 Skimmed milk powder 13 Edible oils 9 Two 5 kg batches of the substrate were granulated as follows: In the first granulation, the substrate was placed in a 50 cm diameter pan granulator, set at an angle of 300 to the horizontal and rotating at about 20 rpm, and sprayed with 1.6 litres of an aqueous solution containing 15% by weight gelatin (120 Bloom grade ex Croda) maintained at 60"C, via a Delavan-Watson WG 606 nozzle at a working pressure of 60 psi. The granulated product was dried in a tray oven at 500C to a water content of about 12% by weight. In the second granulation, the procedure used was identical except that in place of the gelatin solution, 1.6 litres of pure water at ambient temperature (about 20"C) were used. The two dried products had the following sieve analyses: % by weight of product Granule size (microns) Example 13 Comparative > 2000 3.3 10.5 1400-2000 3.7 4.0 850--1400 33.3 17.9 333- 850 58.3 32.0 ! < 355 1.4 35.6 These sieve analyses indicate that the process of the invention produced a much higher yield of granules in the target ranges of 355--850 microns and 850--1400 microns. In the Comparative Example, there is an undesirably high proportion of oversize granules ( > 2000 microns) and an unacceptably high proportion of fines ( < 355 microns) which would have to be re-cycled, as this represents largely un-agglomerated material because the substrate mean particle size was about 300 microns. Thus the Comparative process is clearly inefficient and wasteful. The advantages of the process of the invention were demonstrated even more dramatically when the two products were subjected to the Flow Performance test. The 355--850 micron fraction of Example 13 was given a rating of 2, but that of the Comparative Example had a rating of only 4 and on this basis would have been almost useless in an automatic feeding device. WHAT WE CLAIM IS:

1. A process for the preparation of a feedstuff for small animals which require their diet to include granules having a maximum dimension in the range 300 to 2000 microns, in which process a bed of finely-divided essentially solid feedstuff ingredients, having a mean particle size (Rosin Rammler) not greater than 500 microns, is tumbled in a pan granulator and the tumbling bed is granulated by spraying thereon an aqueous solution of a non-toxic polymeric material, the resulting granulated product is dried to a moisture content of less than 15% by weight, and the granulated product is physically classified to ensure that it contains not more than 10% by weight of granules having a maximum dimension of less than 300 microns.

2. A process according to Claim 1, wherein the mean particle size (Rosin Rammler) of the ingredients in the tumbling bed is not greater than 300 microns.

3. A process according to Claim 1 or Claim 2, wherein the mean particle size (Rosin Rammler) of the ingredients in the tumbling bed is at least 100 microns.

4. A process according to any one of Claims 1 to 3, wherein the particle size spread (Rosin Rammler) of any ingredient which comprises at least 30% by weight of the tumbling bed is not less than 0.9.

5. A process according to Claim 4, wherein the particle size spread (Rosin Rammler) is not less than 1.0.

6. A process according to Claim 5, wherein the particle size spread (Rosin

Rammler) is not less than 1.2.

7. A process according to any one of Claims 1 to 6, wherein the quantity of solution sprayed onto the tumbling bed is from 15 to 40% by weight of the dry bed.

8. A process according to any one of Claims 1 to 7, wherein the polymeric material is an edible gum of animal or vegetable origin.

9. A process according to Claim 8, wherein the polymeric material is a gelatin.

10. A process according to Claim 9, wherein the aqueous solution sprayed onto the tumbling bed contains from 3 to 30% by weight of gelatin.

11. A process according to Claim 8, wherein the polymeric material is an alginate.

12. A process according to Claim 11, wherein the aqueous solution sprayed onto the tumbling bed contains from 0.1 to 2% by weight of alginate.

13. A process according to any one of Claims 1 to 7, wherein the polymeric material is casein.

14. A process according to Claim 13, wherein the aqueous solution sprayed onto the tumbling bed contains from 3 to 30% by weight of casein.

15. A process according to any one of Claims 1 to 7, wherein the polymeric material is a starch, a degraded starch or a substituted cellulose.

16. A process according to Claim 15, wherein the polymeric material is a sodium carboxymethyl cellulose.

17. A process according to Claim 16, wherein the aqueous solution sprayed onto the tumbling bed contains from 0.1 to 5% by weight of sodium carboxymethyl cellulose.

18. A process according to any one of Claims 1 to 7, wherein the polymeric material is a water-soluble synthetic polymer.

19. A process according to Claim 18, wherein the polymeric material is polyacrylamide.

20. A process according to Claim 19, wherein the aqueous solution sprayed onto the tumbling bed contains from 30 to 200 ppm of polyacrylamide.

21. A process according to any one of Claims 1 to 20, wherein the ingredients in the tumbling bed incorporate oil.

22. A process according to any one of Claims 1 to 20, wherein the ingredients in the tumbling bed include fish meal as a major ingredient.

23. A process according to Claim 22, wherein the fish meal contains at least 5% oil, expressed by weight of the fish meal.

24. A process according to any one of Claims 1 to 23, wherein the granulated product is dried to a water content of not greater than 12% by weight.

25. A process according to any one of Claims 1 to 24, wherein the granulated product is physically classified to remove therefrom any granules having a maximum dimension greater than 2000 microns.

26. A process according to Claim 25, wherein the physical classification removes all granules having a maximum dimension greater than 1400 microns.

27. A process according to Claim 26, wherein the physical classification removes all granules having a maximum dimension greater than 1000 microns.

28. A process according to any one of Claims 1 to 27 wherein the granulated product is physically classified to ensure that it contains not more than 5% by weight of granules having a maximum dimension less than 300 microns.

29. A process according to Claim 1, substantially as hereinbefore described with reference to either ExamPle 1 or Example 2.

30. A process according to Claim 1, substantially as hereinbefore described with reference to any one of Examples 3 to 13.

31. A granulated feedstuff prepared by a process according to any one of Claims 1 to 30.

32. A pan-granulated feedstuff for small animals, comprising granules at which at least 80% by weight have a maximum dimension of at least 300 microns but not greater than 2000 microns, but with not more than 10 / < , by weight of the granules having a maximum dimension of less than 300 microns, exhibiting consistently a Flow Performance rating of not worse than 2 as determined using the test procedure hereinbefore described.

33. A feedstuff according to Claim 32, comprising not more than 5 /c by weight of granules having a maximum dimension of less than 300 microns.

34. A feedstuff according to Claim 32 or Claim 33, comprising granules of which at least 80% by weight have a maximum dimension not greater than 1400 microns.

35. A feedstuff according to claim 34, comprising granules of which at least 80% by weight have a maximum dimension not greater than 1000 microns.

36. A feedstuff for fish according to any one of Claims 32 to 35.

37. A feedstuff according to any one of claims 32 to 36, containing at least 3% by weight of oil.

38. A feedstuff according to any one of Claims 32 to 36, containing at least 30% by weight of fish meal.

39. A feedstuff according to Claim 38, containing at least 50% by weight of fish meal.

40. A feedstuff according to Claim 38 or Claim 39, wherein the fish meal contains at least 5% oil, expressed by weight of the fish meal.

41. A feedstuff for young fish according to any one of Claims 32 to 40, wherein at least 80 /, by weight of the granules have a maximum dimension in the range 300 to 850 microns.

42. An animal feedstuff in the form of granules of which at least 80% by weight have a maximum dimension of at least 300 microns but not greater than 2000 microns, but with not more than 10% by weight of the granules having a maximum dimension of less than 300 microns, the granules having been prepared by agglomerating finely.

divided essentially solid feedstuff ingredients, wherein the feedstuff contains at least 3% by weight of oil and exhibits consistently a Flow Performance rating of not worse than 2 as determined using the test procedure hereinbefore described.

43. An animal feedstuff according to Claim 42, which contains at least 10% by weight of oil.

44. An animal feedstuff according to Claim 42 or Claim 43, which contains at least 30% by weight of fish meal.

45. An animal feedstuff according to Claim 44, which contains at least 50% by weight of fish meal.

46. An animal feedstuff according to any one of Claims 42 to 45, wherein at least 80% by weight of the granules have a maximum dimension of not greater than 1000 microns.

47. A feedstuff for fish according to any one of Claims 42 to 46.