The present invention refers to a novel animal feed additive effective as preservative, said feed additive comprises as active ingredients propionic acid, glyceryl propionates and optionally a minor amount of an alkali metal salt. In a further aspect the present invention refers to a method of producing said animal feed additive and in yet a further aspect to the use thereof as mould inhibitor in animal feedstuffs.

Due to steady changes in the ecology resulting from the introduction of more intensive methods of farming, and increasing use of chemicals which alter the microbial populations of soils and plants, the growth of toxin producing and infectious moulds in both human foods and animal feedstuffs has during recent years become a matter of increasing concern from the view point of both animal and human welfare. Considerable research has been devoted to the development of methods for inhibiting mould growth which typically are activated directly in proportion to the moisture content of the feedstuff, that is the greater the moisture content, the greater the hazard of mould growth.

Propionic acid is today widely used as an effective and well proven preservative in animal feedstuffs. However, propionic acid is, as being corrosive to skin and metals and having a flash point of less than 55°C, classified to be labelled as corrosive and flammable according to for instance ADR transport regulations, thus limiting the possibility for end-users to store and transport the material. An established way to avoid this classification is to, at least partly, neutralise the acid by addition of for instance an alkaline compound, such as ammonia, and/or by addition of vapour pressure depressants. The process require costly installations for handling the alkaline material.

It has now quite unexpectedly been found that a mixture of glyceryl propionates and propionic acid exhibits properties making said classification redundant, while preservative properties, such as mould inhibition, are essentially the same as for pure propionic acid. The present invention accordingly provides a feed additive that is substantially non-corrosive and has a volatility and a flash point being outside necessary transport classifications. The novel animal feed additive comprises 30-80%, such as 40-60% or 35-65%, by weight of propionic acid, 20-70%), such 30-50%) or 35-55%, by weight of glyceryl propionates, less than 4%>, such as less than 2% such as 0.5-1%, by weight of glycerol, and optionally 1-10%, such as l-5% ₀ , by weight of an alkali metal salt, preferably a formate, such as potassium or sodium formate balance to 100% by weight being water, such as reaction water and water emanating from the water content of used raw materials. Said glyceryl propionates are present as a mixture of mono, di and tripropionates in a ratio of 10-30% by weight of glyceryl monopropionate, 40-70%) by weight of glyceryl dipropionate and 10-30% by weight of glyceryl tripropionate, balance being 100% by weight

In a further aspect the present invention provides a method of producing said animal feed additive by subjecting a mixture comprising 70-90 % by weight of propionic acid and 10-30 % by weight of glycerol to reaction at a temperature of 50-70°C until a reaction equilibrium is obtained. Said reaction is optionally performed in presence of an acidic catalyst, such as sulphuric acid, in an amount of for instance 0.05-0.5 % by weight calculated on total amount of reactants. Said method may also optionally comprise the step of diluting yielded reaction mixture with an additional amount of propionic acid to obtain a composition comprising propionic acid and glyceryl propionates in amounts as previously disclosed, and/or the step of admixing a said alkali metal salt. Used acidic catalyst is suitably neutralised by addition of a stoechiometric amount of an alkaline compound, such as ammonium hydroxide and/or an alkali metal hydroxide. The reaction mixture or composition thus obtained is suitably used as mould inhibiting additive in animal feedstuffs.

The animal feed additive according to embodiments of the present invention can, of course, be diluted to any suitable concentration of active components by addition of for instance water, formic acid, propionic acid, butyric acid and/or other mould inhibiting compounds. The feed additive can, of course, also be supplemented by addition of other feed additives, preservatives, nutrients and pharmaceutical preparations, such as compatible antibiotics and vitamins.

The following preferred specific embodiments are to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever. In the following, Examples 1-3 refer to preparation of animal feed additives according to embodiments of the present invention and Examples 4-7 to evaluation of yielded products in comparison with commercially available propionic acid based feed additives. Evaluation results are given in enclosed Tables 1-3.

Example 1

70 kg of propionic acid, 30 kg of glycerol and 200 g of sulphuric acid, as catalyst, were mixed and heated to 60°C in a reaction vessel. A reaction equilibrium was reached after 8 hrs. and yielded reaction mixture was cooled to room temperature and, a to said sulphuric acid stoechiometric amount of, ammonium hydroxide was added.

Yielded reaction mixture exhibited following composition: Propionic acid 61.3 % by weight

Glyceryl monopropionate 6.2 % by weight

Glyceryl dipropionate 15.7 % by weight

Glyceryl tripropionate 7.3 % by weight

Glycerol 0.5 % by weight

Example 2

Example 1 was repeated with the difference that 2% by weight of sodium formate finally was admixed into yielded reaction mixture.

Example 3

Example 1 was repeated with the difference that 3% by weight of sodium formate finally was admixed into yielded reaction mixture.

Example 4

The product obtained in Example 1 was sprayed, at application rates equivalent to 35, 46 and 59% of recommended application rates* for aerobic preservation of moist grain with propionic acid, onto barley having a moisture content of 34% and the sprayed grain samples were stored in glass jars simulating normal storage conditions for grain preservation. The product of Example 1 was compared with pure propionic acid and Lupro-Grain ^® (BASF, Germany) dosed in relation to propionic acid content. The treated samples were stored in glass jars simulating normal storage conditions for grain preservation at 18-22°C. Growth of mould was observed weekly and noted. The tests were performed by Swedish University of Agricultural Sciences and assessed with the following scoring system.

0 = no visible mould growth

1 = 1-3 small mould colonies visible

2 = visible mould growth on < 10% of the surface

3 = visible mould growth on 10-30%) of the surface

4 = visible mould growth on 30-50% of the surface

5 = visible mould growth on >50% of the surface and is given in Table 1 as average value for 15 samples/product. * Recommended application rate were calculated as follows:

Recommended application rate (ml/kg moist grain) = (moisture content x 0.375) - 1.125 Ekstrom, N., Thyselius, L. Johansson, S. & Thomke, S., 1973, Syrabehandling av spannmal. Dosering, fodervarde, ekonomi (Acid Treatment of Grain. Application, Nutrative Quality and Economy), JTI-meddelande #352, JTI (www.jti.se), Uppsala, Sweden (in Swedish with English summary).

Example 5

30 g of the product obtained in Example 2 was weighed into an open 100 ml beaker and stored for 65 days at room temperature. Remaining sample in calculated as percent by weight was determined by weighing at intervals. A comparative sample of Lupro-Grain ^® were tested under the same conditions. The result is given in Table 2.

Example 6

Corrosion of steel panels was evaluated for products according to Example 1 , 2 and 3. The corrosion test was performed according to UN Test Methods Part ΓΠ Section 37. The result, as weight loss of the steel panels expressed as percent by weight and intrusion depth as μπι, is given in Table 3.

Example 7

Skin Irritation tests were performed according to OECD Guideline No 404, "Acute Dermal Irritation/Corrosion", April 2002, and evaluated according to Commission Directive 2001/59/EC. The result of tests using the product obtained in Example 1 gave that said product is classified as non-irritant to the skin.

Table 1

Appl. rate 35 % Appl. rate 46 % Appl. rate 59 %

PA LG Ex. 1 PA LG Ex. 1 PA LG Ex. 1

28 days 1.3 3.8 1.8 0 0 0 0 0 0

56 days 4.0 5.0 4.5 1.0 1.8 0.3 0 0 0

84 days 5.0 5.0 5.0 2.5 2.8 0.3 0 0 0

112 days 5.0 5.0 5.0 4.3 4.3 0.3 0 0 0

PA = Propionic acid

LG = Lupro-Grain ^®

Ex. 1 = Product of Example 1

Table 2

Table 3

Weight loss, % w/w Intrusion depth, μιη

Example 1 - Panel 1 1.76

Example 1 - Panel 2 2.50 250

Example 1 - Panel 3 3.84

Example 2 - Panel 1 1.64

Example 2 - Panel 2 1.64 80

Example 2 - Panel 3 0.64

Example 3 - Panel 1 1.49

Example 3 - Panel 2 1.45 < 50

Example 3 - Panel 3 0.37