METHOD OF TREATING LIVESTOCK FEEDSTUFF AND A FAT COMPOSITION FOR USE IN FEEDSTUFF

Abstract: A method of treating a livestock feedstuff comprises coating the feedstuff, especially in the form of pellets, with a composition comprising a fat or oil and a lignosulphonate. Additives such as pigments, vitamins, flavourings and pharmaceuticals may be included in the composition. A composition suitable for use in animal feed is also disclosed, consisting essentially of a fat or oil and a lignosulphonate. The composition is suitably prepared by blending the fat or oil with the lignosulphonate and then heat treating the blend. The tendency of the fat or oil to oxidise is thereby suppressed.

Description: METHOD OF TREATING LIVESTOCK FEEDSTUFF AND A FAT COMPOSITION FOR USE IN FEEDSTUFF The present invention relates to the coating of animal feedstuffs, in particular feedstuffs in the form of pellets, and to a fat or oil composition suitable for such coating. Feedstuffs for livestock such as pigs, cattle, poultry and fish are conventionally based on cereal-type raw materials such as wheat, soya, maize and gluten. To increase the energy value of such feedstuffs it is necessary to add fat or oil to the raw material, and this is typically carried out by incorporating the fat or oil into the raw material at the batch mixing stage before the feedstuff is processed into its final form, most commonly as pellets. The amount of fat or oil which can be added to the raw material prior to pelleting is limited to a maximum of about 3% by weight, it being found that greater amounts tend to have a detrimental effect on the quality of the final pellets. In order to achieve levels above 3% it is possible to spray additional fat or oil onto the finished pellets, either directly as they emerge from the pelleting machine or after cooling. An absolute maximum of about 6% by weight may theoretically be added this way, but in practice it is limited to about 3%. The addition of any higher amounts to the pellet surface results in the fat/oil leaching away. This, in turn, causes product handling and physical quality problems and has a detrimental effect on the physical stability of the pellets, particularly over long periods. There is now provided, in accordance with the present invention, a method of treating a livestock feedstuff, which method comprises coating the feedstuff with a composition comprising a fat or oil and a lignosulphonate. The treatment enhances the quality of the feedstuff by allowing its physical stability to be maintained. It also has the advantage of increasing the amount of fat or oil which may be incorporated into the feedstuff. Preferably, the feedstuff which is coated is in the form of pellets. Pelleted feedstuffs typically range in diameter from 3mm to 12mm. The coating composition is prepared by blending the fat or oil with a lignosulphonate. The fat or oil may be any which is conventionally employed in feedstuffs, used either 'straight 1 or blended, for example palm FAD (fatty acid distillate), soya oil, tallow, refined vegetable oil, fish acid oil, animal lard or crude fish oil. - The fat or oil is suitably heated during the blending process, typically to a temperature of from 40*C to 100'C, for example from 45*C to 95*C, and preferably from 50*C to 92*C. A temperature of from 60*C to 90*C is particularly preferred. The lignosulphonate may be in liquid or powder form. When it is a liquid the coating composition with the fat or oil takes the form of an emulsion. When it is a powder, the coating composition comprises lignin particles suspended in the fat or oil. The liquid fat or oil and lignosulphonate may be pre-blended, in which case constant agitation of the two components is required. Alternatively, the two components may be proportioned, mixed and then applied on-line. Any lignosulphonate or other lignin based product may be used in accordance with the invention. Lignosulphonates are the principal components in the spent pulping liquor from wood pulping processes. They are also known as sulphite lignins. Various compounds of lignosulphonate may be formed, one example being calcium lignosulphonate. On an industrial scale calcium lignosulphonate is typically prepared by the Howard process, which involves adding calcium hydroxide to the spent pulping liquid in three stages. The first precipitate which forms is calcium sulphide, which is recycled to the pulping liquor. The second step separates an insoluble calcium lignosulphonate. The third stage precipitate, which consists of a small additional amount of lignosulphonate together with excess lime, is added to the lime of the first stage of a succeeding batch. Lignosulphonates of various bases may also be prepared by base exchange, or in the pulp digestion itself. A liquor of calcium lignosulphonate, for example, can be made into ammonium lignosulphonate by the addition of ammonium sulphate. The calcium sulphate precipitate is removed before the lignosulphonate liquor is used or dried. Likewise, adding calcium hydroxide to ammonium lignosulphonate liquor liberates ammonia, leaving calcium lignosulphonate. Large amounts of sodium lignosulphonate may be prepared by similar methods. The sugars contained in lignosulphonate may be separated by various methods. Fermentation and yeast growth remove much of the sugars, whereas to produce specialised lignosulphonate products techniques such as ion exchange, ion exclusion, gel absorption, electrodialysis, ultra-filtration and reverse osmosis are used. Examples of lignosulphonates which may be used in accordance with the invention include calcium, ammonium and sodium lignosulphonate. A number of cations are in fact complexed by lignosulphonate, which may in turn be unfermented, or fermented, i.e. sugar reduced, lignosulphonate. A high sugar lignosulphonate liquid form, containing about 50% lignin solids, is one example of a suitable material. Calcium based lignosulphonates are particularly suitable, and these are preferably sugar reduced lignosulphonates although de-sugared lignosulphonate, i.e. lignosulphonate of which the sugar content has been chemically destroyed may also be used. The lignosulphonate is suitably used in any commercially available form, such as "Wafolin" supplied by Holmen Chemical Products. The fat or oil and lignosulphonate are blended in relative proportions of fat or oil and lignosulphonate which depend on the dimensions of the feedstuff, for example the pellet diameter, and on the amount of fat or oil which it is desired to add to the feedstuff. The weight ratio of fat or oil to lignosulphonate in compositions specifically for coating feedstuffs may range from 10:1 to 1:10, typically from 5:1 to 1:5 and preferably from 3:1 to 1:3. A weight ratio from 3:1 to 1:1, especially 1:1, is particularly suitable. The coating composition may include additional ingredients, for example selected from pigments, vitamins, flavourings and pharmaceutical agents. Such additives are typically introduced into the composition during the blending of the fat or oil and lignosulphonate. Flavouring agents may be particularly advantageous since they mask the taste of lignin, which may be unpalatable to certain livestock. The coating composition comprising fat or oil and lignosulphonate, optionally together with further additives, is typically sprayed onto the feedstuff to form a coating thereon. The feedstuff may be coated cold, or may be heated before the coating is applied. Feedstuff which is coated "cold" may have been taken from storage, in which case it is typically at ambient temperature. Alternatively, feedstuff pellets may be coated directly after emerging from the cooler, in which case they are generally at a temperature a few degrees above ambient. Feedstuff which is heated is typically coated at the temperature at which it emerges from the pellet press generally from 50'C to 80 β C, typically about 65'C. The coating composition itself may be at any convenient temperature when it is sprayed onto the feedstuff, for example any temperature from 15*C to 95*C, such as from 30*C to 80*C, or from 40 # C to 70*C. A temperature of 50*C is particularly suitable. The feedstuff, preferably in the form of pellets, is suitably subjected to a tumbling action whilst being sprayed. This maximises the efficiency of coating whilst also preventing the pellets from sticking together and causing the fines produced to stick to the pellets. When feedstuff pellets are sprayed immediately on leaving the die, all the pellets and fines produced are coated with the composition. A similar result is achieved if the pellets are sprayed when they emerge from the cooler and before sifting. In this case, however, fines and dust removed by the cooler fan will need to be returned to the container in which the coating takes place if no reprocessing of fines returns is required. The method of the invention gives rise to feedstuff pellets having an improved durability. The greatest durability is found to occur when the coating composition sprayed on to the pellets is such as to produce a weight increase due to lignin solids of about 2.7%, and the pellets are heated. The method of the invention also enables higher levels of fat or oil to be incorporated into livestock feedstuffs than has previously been possible. It is considered that overall fat or oil levels of up to 20% by weight may be achieved by the method of the invention. It appears that the fat or oil contained in the coating composition sprayed onto the feedstuff pellets separates out and is absorbed by the feedstuff. It is prevented from subsequently leaking out, for example during storage, by the lignosulphonate "skin" which forms around each of the pellets. This skin, or shell, of lignin serves as a protective outer layer for the pellets. Further advantages of the method of invention are that it minimises the need for reprocessing 'fines returns*, which significantly reduces the costs of pellet production (by 5 to 10%) . Also, additional ingredients such as flavourings, pigments and pharmaceutical agents, which may be destroyed by the heat and mechanical treatment involved in pelleting, can be incorporated into feedstuff pellets after the pelleting process, by inclusion in the coating composition of fat/oil and lignosulphonate sprayed onto the finished pellet surface. A further, problem, associated with animal feedstuffs, is the tendency of the fats or oils used in them to become oxidised, and therefore to turn rancid. This is a commonly encountered problem. It means that the products containing fats or oils may deteriorate prematurely, which is both inconvenient and uneconomical because of the limited shelf-life which the products consequently possess. It has now surprisingly been found that the oxidation of fats or oils may be suppressed by the addition thereto of a lignosulphonate. Accordingly the present invention further provides a composition consisting essentially of a fat or oil and a lignosulphonate. As used herein, the term "consists essentially of" means that the composition contains fat or oil and lignosulphonate, with small amounts of other ingredients present only to the extent that they do not have any substantial effect on the properties of the composition. It embraces the use of fats/oils and lignosulphonates in their commercially available forms. The composition may comprise any fat or oil which it is desired to stabilise against oxidation. In particular the fat or oil may be any which is conventionally employed in animal feedstuffs, for example animal lard. The lignosulphonate may be any lignosulphonate as hereinbefore described. The composition of the invention comprises the components in any weight ratio, for example, a weight ratio of fat or oil to lignosulphonate of from 99:1 to 1:99, from 90:10 to 10:90, of from 70:30 to 30:70. Preferably, a 50:50 ratio is used. The composition of the invention may be prepared by blending together the fat or oil and the lignosulphonate. The invention therefore further provides a method of reducing the tendency of a fat or oil to oxidise, which comprises forming a blend of the fat or oil and a lignosulphonate and then heat treating the blend. Heat treatment is typically carried out by spreading the composition onto a planar substrate, for example a sheet of metal (e.g. aluminium) foil, and placing this under a grill until the mixture is of a crusty consistency. This may take from 1 to 5 minutes, typically 2 minutes, and is suitably carried out under the grill of a gas oven. The composition is spread fairly thinly onto the substrate, suitably at a thickness which is no greater than 2 mm, for example 1 mm. It is usually necessary to maintain a distance of at least 15 cm (6 inches) between the composition and the flames of the grill in order to avoid ignition. Following grilling, the composition is conveniently broken up and stored in bags to await use. Although not limited in its application, the composition of the invention may be used as a pre ix in animal feedstuffs, when it can yield a feed having improved shelf-life because oxidation of the fat/oil is reduced. It may also be used in the method of the present invention to coat pellets of animal feed. Animal feed-stuff may be prepared by combining meal such as wheat, soya, maize or gluten, with the composition of the invention, which has optionally been heat treated and, if desired, pelletising the resulting mixture. The mixture prepared in pellet form is particularly preferred. In a standard method used to prepare such feedstuffs, the feed raw materials such as wheat, soya, maize or gluten are stored in silos above a weigher, next to which there is a hopper for additives such as minerals, vitamins and pellet binder. A batch comprising feed raw materials and additives is blended in the weigher and then routed to a grinding plant for maceration into what is termed "mixed meal". The mixed meal proceeds to a batch mixer where liquid additives such as water, fat and molasses are introduced. The composition of the invention may therefore conveniently be added at this stage. Steam and molasses can be added subsequently, and the composition is then pelleted if desired. From the point of view of transportation, delivery and distribution to animals, it is most convenient if the feedstuff is provided in pelletised form. However, the addition of the fat or oil to the meal prior to pelleting has been shown sometimes to give rise to pellets of unsatisfactory durability. It is therefore also possible, instead of incorporating the composition of the invention into the batch mix prior to pelleting, to spray the composition consisting essentially of fat or oil and lignosulphonate onto the feedstuff pellets once these are formed in accordance with the method of the present invention described above. The keeping quality of the heat treated fat/oil and lignosulphonate composition can be assessed by measuring the free fatty acid content (as %-oleic acid) and the peroxide value of the fat/oil at fixed intervals. For this purpose the mixture may be broken up and stored in plastics bags under conditions of ambient light and temperature. Samples may then be taken out for measurement of the free fatty acid content and the peroxide value, using conventional techniques such as are exemplified in Comparative Example 1 which follows. Example 7 which follows describes such a process of testing; the results achieved may be compared with those reported in Comparative Example 2 which relate to samples of fat either without any additives or containing a conventional antioxidant. The invention will be further illustrated by the following Examples. Example 1: Coating of cold pellets Crude fish oil (300 g) was blended by hand stirring, whilst being heated to 50'C, with a high sugar lignosulphonate (300 g) in liquid form containing 50% solids. The resulting composition (60 g) , which was in the form of an emulsion, was applied by means of a hand-held liquid spray to sifted cold salmon pellets of 8 mm diameter (500 g) which were held in a container and tumbled by shaking the container. The coating formed on the pellets increased their weight as follows: weight increase: overall = 10.7% weight increase: due to added oil •= 5.35% weight increase: due to lignin solids = 2.67% Example 2: Coating of cold pellets The procedure of Example 1 was repeated, but with heating the crude fish oil to 92*C whilst it was being blended with the liquid lignosulphonate. The increase in'weight of the pellets due to the coating was found to be the same as in Example 1. Example 3: Coating of heated pellets The procedure of Example 1 was repeated, but this time the composition of fish oil and lignosulphonate was sprayed onto unsifted salmon pellets straight off the press at a temperature of about 65 * C. The increase in weight of the pellets due to the coating was found to be the same as in Example 1 Example 4: Coating of heated pellets Crude fish oil (300 g) was blended by hand stirring, whilst being heated to 92*C, with lignosulphonate (100 g) in powder form. The resulting composition was a mixture of lignin particles suspended in the fish oil, rather than being an emulsion. The composition was applied to sifted hot salmon pellets of 8 mm diameter (500 g) as described in Example 1. The coating which formed on the pellets increased their weight as follows: weight increase: overall — 10.7% weight increase: due to added oil = 8.0% weight increase: due to lignin solids = 2.7% Example 5: Coating of heated pellets Crude fish oil (300 g) was blended by hand stirring, whilst being heated to 92*C, with a high sugar lignosulphonate (150 g) in liquid form containing 50% solids. The resulting composition (60 g) , which was in the form of an emulsion, was applied as described in Example 1 to unsifted hot salmon pellets (8 mm diameter, 500 g) . The coating which formed on the pellets increased their weight as follows: weight increase: overall = 8.3% weight increase: due to added oil = 7.1% weight increase: due to lignin solids - 1.78% Example 6: Coating of heated pellets The process of Example 5 was repeated exactly as described. The observed increase in weight of the pellets due to the coating was as follows: weight increase: overall = 9.8% weight increase: due to added oil = 7.9% weight increase: due to lignin solids = 1.9% Comparative Example 1 (a) Method of determining peroxide value of fat or oil Reagents used: (i) 40 to 60% Petroleum Ether (ii) Solvent Mixture, 2:1 v/v glacial acetic acid: chloroform (stored in brown bottle) . (iii) 0.002 M Sodium Thiosulphate solution prepared fresh from O.I.M. standardised thiosulphate solution. (iv) Potassium Iodide. (v) Starch solution (1% w/v) dissolve lg soluble starch in 100 ml distilled water, warming gently with stirring to effect solution. Place a lOg sample of the fat/oil to be determined in a brown bottle, add approximately 60 ml petroleum ether, cap bottle and shake (on machine) for 20-30 minutes. Filter into a weighed oil flask. Evaporate off solvent with a water pump, blowing out the last traces of solvent vapour with nitrogen flow. Dry outside of flask and reweigh to obtain weight of oil. Add 20 ml of the solvent mixture, and approximately lg powdered potassium iodide and boil gently for 30 seconds. Cool rapidly under a running tap, add 25 ml distilled water, swirl to mix thoroughly, add 1 ml starch solution and titrate with 0.002 M thiosulphate until the blue colour in the upper aqueous layer is discharged. Depending on the colour of the original oil, the upper layer may not go to colorless but may remain yellow brown. The peroxide value is then calculated as follows: Peroxide value = Titre - Blank ml N /500 thio/g oil, Wt. of oil equivalent to m.e. O /kilo 2 A blank on all reagents should be carried through at intervals and should be less than 0.10 ml of 0.002 M thiosulphat . Excessive light and heat should be avoided, especially after extraction and the determination should be completed as quickly as possible after the oil has been extracted. (b) Method of determining free fatty acid value of fat or oil Extract 5g of ground sample with petroleum ether according to Fertiliser and Feeding Stuffs regulations. Distill off the solvent to low bulk on a water bath and remove the remaining low bulk at room temperature using a stream of air or nitrogen. Place 50 ml isopropyl alcohol in a cylinder, add a few drops of phenolphthalein indicator (1% solution of phenolphthalein in isopropyl alcohol), and add 0.1 N sodium hydroxide until the alcohol is a pink colour (usually 2-3 drops required) . Add this neutralised alcohol to the oil residue in the flasks and bring to boiling. Titrate to a faint, permanent pink colour with 0.1 N sodium hydroxide. The free fatty acid value (FFA) is then determined as follows: FFA (as % oleic) = 2.82 x ml O.I.N. NaoH g sample [To obtain FFA as percentage of oil multiply the above figures by 100 .. % oil J It is necessary to prepare the 0.1 N NaoH afresh for each new batch of samples. EXAMPLE 7 A portion of refined lard was mixed with "Wafolin" (Registered Trade Mark) , a lignosulphonate binder, in a weight ratio of 50:50. The mixture obtained was spread onto aluminium foil to a depth of approximately 1 mm and placed under the grill of a domestic gas oven until it was of a crusty consistency. Grilling took place for approximately 2 minutes and it was necessary to keep the mixture at least 115 cm (6 inches) from the flame to avoid ignition. Before forming into a crusty material the mixture appeared to liquify. The mixture was then allowed to cool, broken up and stored in closed plastic bags in light at ambient temperatures (Sample A) . The above procedure was repeated, but using the lignosulphonate binder "Wafolin V". The resultant mixture was broken up and stored as described (Sample B) . It was found that prior to grilling, Sample B was drier than Sample A. During grilling Sample B appeared to bubble more violently then did Sample A. However, Sample B was less "friable" than Sample A. The keeping quality of the two samples was assessed at intervals, in terms of the amount of free fatty acid content (as %-oleic acid) and the peroxide value, using conventional techniques such as described in Comparative Example 1. The results are shown in Table 1. TAB Comparative Example 2 A portion of refined lard was heated gently and a standard antioxidant (such as EMBANOX-BMA from May and Baker) added thereto at 375 ppm. The mixture (Sample C) was allowed to cool and was then stored as described in Example 1. A portion of refined lard without additives (Sample D) was also stored as described in Example 1. The keeping quality of the two samples was assessed as described in Example l. The results are shown in Table 2.

Claims: CLAIMS 1. A method of treating a livestock feedstuff which comprises coating the feedstuff with a composition comprising a fat or oil and a lignosulphonate. 2. A method according to claim 1 wherein the feedstuff is in the form of pellets. 3. A method according to claim 1 wherein the weight ratio of fat or oil to lignosulphonate in the composition is from 10:1 to 1:10. 4. A methpd according to claim 1, wherein the fat or oil is crude fish oil. 5. A method according to claim 1, wherein the composition includes one or more additives selected from pigments, vitamins, flavouring agents and pharmaceutical agents. 6. A composition consisting essentially of a fat or oil and a lignosulphonate. 7. A composition according to claim 6 or a method according to claim 1 wherein the lignosulphonate is calcium 1ignosulphonate. 8. A method of reducing the tendency of a fat or oil to oxidise, which comprises forming a blend of the fat or oil and a lignosulphonate and then heat treating the blend. 9. An animal feedstuff comprising meal and a composition as claimed in claim 6 or a blend as prepared by the method claimed in claim 8. 10. A feedstuff according to claim 9 in the form of pellets.

Inventors: PAYNE JOHN DAVID, PAYNE, JOHN, DAVID
Applicants: LIGNOTECH UK LTD, LIGNOTECH (UK) LIMITED
Application year: 1991
Main classification: A23K1
IPC codes: A23K1