CA2196760A1

CA2196760A1 - An enzyme feed additive and animal feed including it

Info

Publication number: CA2196760A1
Application number: CA002196760A
Authority: CA
Inventors: Michael Richard Bedford; Andrew John Morgan; Kathleen Clarkson; Hagan Klaus Schulze
Original assignee: Individual
Current assignee: Danisco UK Ltd; Danisco US Inc
Priority date: 1994-08-19
Filing date: 1995-08-17
Publication date: 1996-02-29
Also published as: FI970676A; GB9416841D0; AU3394495A; CN1159145A; WO1996005739A1; NZ292148A; FI970676A0; US5612055A; JPH10504716A; NO970745L; EP0704167A1; AU692596B2; NO970745D0

Abstract

An enzyme feed additive is provided comprising a xylanase, a protease, and optionally a .beta.-glucanase. The ratio of the units of xylanase activity per unit amount of the feed additive to the units of .beta.-glucanase activity per same unit amount of the feed additive is 1:0-0.25. Preferably, the xylanase is the low pI xylanase and/or the high pI xylanase obtained from Trichoderma longibrachiatum. Preferably, the protease is a mutant subtilisin comprising a substitution at the amino acid residue position equivalent to tyr+217 of Bacillus amyloliquefaciens, subtilisin with leucine.

Description

~V096/05739 P_ll~.-. . 11 ~ 21 9676~

AN ENZYME FEED ADDITIVE AND ANIMAL FEED INCLUDING IT

The present invention relates to an enzyme feed additive, and in particular to such an additive which can decrease the feed conversion ratio of a cereal-based animal feed.

T ~ ~v. ':5 in animal feeds to enable animals to digest them more efficiently are constantly being sought. One of the main rnnr~rn~ iS to improve the feed conversion ratio (FCR) of a feed without increasing its cost per unit weight. The FCR is the ratio of the amount of feed consumed relative to the weight gain of an animal. A low FCR indicates that a given amount of feed results in a growing animal gaining proportionately more weight. This means that the animal is able to utilise the feed more efficiently. One way in which the FCR of a feed can be improved is to increase its digestibility.

There are various constraints on the digestibility of the nutritional rn-rnn~n~c of a feed such as its starch, fat, protein and amino acid rnnt~n~fi. These constraints include:

(i) the viscosity of materials present in the animal~s gut. Such viscosity is due, at least in part, to soluble non-starch polysaccharides such as mixed-linked ~-glucans and arabinoxylans;

(ii) entrapment of nutrients within the cell walls of the feed, particularly those of the aleurone layer SUBSI ~TUTE SH.ET (RULE ~6~

W096/05739 2 1 9 6 7 6 0 . ~

in cereals. Such entrapment is caused by the high levels of non-starch polysaccharides in the cell walls of cereals which are relatively resistant to break-down by the animal's digestive system. This prevents the nutrients entrapped within the cells from being nutritionally available to the animal;
and (iii) a deficiency in endogenous enzyme activity, both of the animal and of the gut microbial population particularly in a young animal.

The above problems which interfere with digestibility are particularly noticeable in the case of cereal-based diets, such as those having a high wheat content.

Due to the problem of poor digestibility of nutrients from the ~eed, it i8 normally nece~Ly to formulate feeds to contain significant amounts of energy providing materials in order to meet the nutritional demands of animals. Such energy providing material~ conv~nt;n~ y include starch, fat, sugars, fibre etc The requirement o~ including these energy providing materials, or sources of such materials, in a feed adds a considerable extra cost which is disadvantageous from an economic view point.

In an attempt to solve the problem of poor digestibility of cereal-based feeds, it i8 known to include enzyme supplements such as ~-glucanases or xylanases in animal feeds. For example, W0 91/04673 discloses a feed additive for SUeSTiT~E S~ ETt~JLE~

~W096/OS739 2 ~ 9 6 7 6 0 1 ~11~ . "

alleviating ~ hsnrption syndrome in poultry which causes reduced digestion. The additive includes a cellulase and a xylanase. JP-A-60-75238 discloses a feed for domestic animals which cnnt~;nq an enzyme cocktail ;nr1tl~;ng protease-, cellulase-, amylase- and lipase-activities. This reference speculates that these various enzyme activities enable fel -~t;on microbes to grow and these become useful nutritional _ ~ntq of the feed.

Cellulases (i.e. the cellulase system) are enzyme compositions which hydrolyze cPl1n1nRe (~-1,4-D-glucan linkages) and/or derivatives thereof (e.g. phnqrhnric acid swollen cellulose) and give as primary products glucose, cP11nh;r,~e, r~l10n1;grsetrrh~rides, and the like. A cellulase system produced by a given miuLuUL~ ism is comprised of several different enzyme rl;tqc;f;r~t;nn~ ;rr~ ;nrJ those ;~Pnti~;ed as exo-r~1lrh;nhydrolases (EC 3.2.1.91) ("CBHN), endoglucanases (EC 3.2.1.4) ("EGn), and ~-glurosi~Aqes (EC
3.2.1.21) ("BG") (Schulein, M., 1988). Moreover, these classifications can be further separated into individual ~nt~. For example multiple CBH , ~nt~ and EG
~nt~ have been ;~ol~ted from a variety of bacterial and fungal sources such as the cP11~ Re enzyme complex of Trirhn~Pt~- longibrac~tiat~tt which consists of two exo-cellobiohydrolases, CBHI and CsHII, at least three pn~rg1llr~n~~es, EGI, EGII and EGIII, and at least one ~-glucosidase. The endoglucanases and exo-cellobiohydrolases are cr,nq;~Pred to act synergistically in the hydrolysis of cellulose to small cello-oligos~rrh~rides (mainly cellobiose), which are subsequently hydrolysed to glucose by SlJ8ST1~llTE SHEE~ IR~LE ~

W096~5739 2 1 9 6 7 6 0 P~ g~

the action of ~-glucosidase. In addition to hydrolyzing the ~-1,4 linkages in cellulose, endo-1,4-~-glucanase (EC
3.2.1.4) will also hydrolyze 1,4 linkages in ~-glucans also ~nnt~;ring 1,3-1inkages. The endoglucanases act on ;n~Prn~l linkages to produce cPll~hinse, glucose and cello-oligosaccharides. The exo-~Pl 1 ~h; ~ydrolases act on non-reducing ends of cellulose polymers to produce rPl l nhj 08e as the principal product.

Organisms which produce or express cellulase enzyme complexes often also express xylanase activity. For example, two different xylanase enzymes have been j ~Pnt; f; Pd which are produced by T. longibrachiatum. The purification of these two different xylanases, one referred to as high pI xylanase ~having a pI of about 9.0) and the other referred to as low pI xylanase (having a pI of about 5.2), as well as the cloning and sequencing of the gene for each xylanase is described i~ detail in Wo s2/06209. Figure 16 of this dc t sets out the deduced amino acid sequences for both the low pI and high pI gene products. Example 22 also teaches how to create T. longib~achia~um strains which over-expres8 the low pI and high pI xylanase genes and which are unable to produce some or all of the non-xylanase cPllul~qe components normally associated with T. longibrachiatum such as CBHI, CBHII, EGI, EGII, EGIII and BG.

As - ;onP~ above, the use of cellulases and xylanases in animal feeds is known as is the use of proteases. It is found however that many naturally occurring sources of xylanase contain a significantly greater relative activity of SUBSI ITUTE S~ ,EEI i'r.ui~

~ 096/OS739 2 1 9 6 7 6 0 r~ 77 ~-glucanase. For example in natural strains of T.
long;hr~h;atum, the ratio of xylanase activity to ~-glucanase activity is of the order 1:5. Most surprisingly, it has been found that when a xylanase is included in a cereal-based diet at or around its optimum dosage level, the co-presence of enzymes possessing ~-glucanase activity increases the FCR of the feed which is of course disadvAntAg~ol-~. In view of this surprising finding, it is concluded that enzymes having ~-glucanase activity are not only nnn~c~A~ry in feeds supplemented with a xylanase, but their presence is in fact ~tr;~ntAl to the benefits obtained from the presence of the xylanase and/or protease.

In the description and claims which follow, reference is made to units of xylanase activity, units of protease activity, and units of ~-glucanase activity. These three activities as used in the present specification are measured by the following three assay methods.

~say M~th~d for Xylan~e A~tivity One unit of xylanase activity is the amount of enzyme which liberates one ~mol of r~n~; ng sugars (expressed as xylose equivalents) from the substrate in one minute under the conditions described.

SUB~IT~1~S:~E~~ ' w096~0s73g 2 1 9 6 7 6 0 ~g~nt ~ W/V) xylan substrate Add 10 ml of 0.5 M sodium hydroxide to 1.0 g of xylan (Fluka 95590). Mix for 30 minutes with a magnetic stirrer. Add about 40 ml of 0.05 M sodium acetate buffer, pH 5.3. Adjust pH to 5.3 with 1 M acetic acid. Fill to 100 ml with 0.05 M sodium acetate buffer, pH 5.3.
Substrate should be mixed all the time when used.

2. 1 M acetic acid Pipette 5.7 ml of glacial acetic acid into a volumetric flask and fill to loO ml with distilled water.

3. o os M sodium acetate buffer, pH 5.3 A. Di8801ve 4.1 g of sodium acetate in distilled water and fill to 1000 ml with distilled water.

B. Diasolve 3.0 g of glacial acetic acid in distilled water and fill to 1000 ml with distilled water.

Ad~ust the pH of solution A to pH 5.3 with solution B.

SUBSTITUTE Sh'EET (Rl1LF ~6 ~ 096l05739 2 1 9 6 7 6 0 ~ "

4. Dinitrosalicylic acid (DNS) reagent Suspend 20.0 g of 3,5-dinitrosalicylic acid in about 800 ml of distilled water. Add gradually 300 ml of sodium hydroxide solution (32.0 g NaOH in 300 ml of distilled water) while stirring rnnt;nllm1qly. Warm the suspension in a water bath (the temperature may not exceed +48~C) while stirring until the solution is clear. Add gradually 600 g of potassium sodium tartrate. Warm the solution (the temperature may not exceed +48~C) if needed until the solution is clear.

Fill to 2000 ml with distilled water and filter through a coarse sintered glass filter.

Store in a dark bottle at room temperature.
The Reagent is stable for a maximum of 6 months.

Procedure 1. E~zyme sample 1 ml of enzyme dilution (in 0.05 M sodium acetate buffer, pH 5.3) is equilibrated at +50~C. Add 1 ml of xylan substrate, stir and incubate at +50~C for exactly 30 minutes.
Add 3 ml of DNS-reagent, stir and boil the reaction mixture for exactly 'iUB~ SHE~ f~

_ _ . . . . , .. _ .. .. _ . ..

W096/0s739 2 1 9 67 60 ~ 777 ~

5 minutes. Cool the reaction mixture ina cold water bath to room temperature and measure the ~hRorh~n~P at 540 nm against distilled water.

2. Enzyme blank Incubate 1 ml of xylan substrate at +50~C for 30 minutes Add 3 ml of DNS-solution and stir. Add 1 ml of enzyme dilution (in 0.05 M
sodium acetate buffer, pH 5.3) and stir.
soil the mixture for exactly 5 minutes. Cool the reaction mixture in a cold water bath to room temperature and measure the absorbance at 540 nm against distilled water.

The ~hc~rh~n~e difference between the enzyme sample and enzyme blank should be 0.3-0.5.

3. Standard curve Prepare standard solutions from anhydrous xylose in 0.05 M sodium acetate buffer, p~
5.3. Xylose c~n~ntration in the standards should be 0.05-0.5 mg/ml. Pipette 1 ml of standard solution, 1 ml of xylan substrate and 3 ml of DNS-reagent into a test tube.
Stir and boil for exactly 5 minutes. Cool in a cold water bath to room temperature and measure the ~hc~rh~n~P at 540 nm against SU~StllllE S~ hU' E 26'!

- === =~ = = =

W096~S739 ~ 77 ~ 21 96760 standard blank. In the standard blank, xylose solution is replaced by 1 ml of 0.05 M

sodium acetate buffer, pH 5.3. Otherwise standard blank is treated like xylose - standard.

Plot xylose cnn~ntration as a function of Ah~nrhAnre New standard curve is ~Le~ d for every new DNS-reagent.

Calclllat;on The xylanase activity of the sample i8 calculated according to the following equation:

Activity(U/g) =(rA(x)-A(o~l x k + cO) x 1000 x MWxyl x t wherein:

A(X) = absorbance of the enzyme sample A(O) = AhSnrhAn~ of the enzyme blank k = the slope of the standard curve C = the intercept of xylose standard curve 1000 = factor, mmol -~ ~mol Df = dilution factor (ml/g) MWxyl = molecular weight of xylose =.

(150.13 mg/mmol) t = reaction time (30 minutes) S ~ E SHEET ;~UL~ 2~

W096/0s739 2 ~ 9 6 7 6 0 r ~

Assay Methnd for ~roteaqe A~tivity One unit of protease activity is the amount of enzyme which liberates from the substrate one microgram of phenolic compound (expressed as tyrosine equivalents) in one minute under the conditions described.

Reagents 1_ 0.6% (w/v) casein substrate Weigh 0.6 g of dry ~ammarsten Casein (Merck 22~2) into a 200 ml beaker. Moisten with a small amount (about 5 ml) of distilled water.
When casein i6 thoroughly moistened add 20 ml of 0.2 M ~;80~; hydrogen rh~sph~te solution. Warm the mixture at +60~C with stirring until casein dissolves and an opal solution is obtained. Add 60 ml of distilled water and if needed 1-2 drops of octyl alcohol (anti-foam agent; similar products can be used). After cooling to room temperature, adjust the pH to 7.5 with 0.5 M
sodium hydroxide and 1 M lactic acid.
Transfer solution into a volumeric flask and fill to 100 ml with distilled water.

Substrate solution is usable for one week if stored in a cold room.

SUB~Ir~T SH~(RU' W096~5739 2 19 6 7 6 0 r ~l,~ , 1 2. 0.2 M Na2HPO4 solution Dissolve 17.80 g of ~;~o~ m hydluy~ll phosphate dihydrate in distilled water and fill to 500 ml with distilled water.

3. 0.02 M NaCl solution Dissolve 1.168 g of sodium chloride in distilled water and fill to 1000 ml with distilled water.

4. Precipitation reagent (TCA) Dissolve 18.80 g of trichloroacetic acid (CCl3COOH), 18.10 g of anhydrous sodium acetate (CH3COONa) and 18.80 g of acetic acid (CH3COOH) in distilled water and fill to 1000 ml with distilled water.

5. Phenol reagent Mix one (1) part of Folin-Ciocalteau phenol reagent with one (1) part of distilled water just prior to the assay.
.

6. 0.55 M Na2CO3 solution Dissolve 58.295 g of disodium carbonate in Sl~BSll~Ul~ SH-ET (~UL~

W096/05739 2 1 96760 ~ " ~

distilled water and fill to 1000 ml with distilled water.

Procedure 1 Enzyme sample Equilibrate 1 ml of enzyme dilution (in 0.02 M NaCl solution) at + 40~C (for about 5 minutes). Add 5 ml of equilibrated casein substrate, stir and incubate at + 40~C for exactly 30 minutes. Add 5 ml of precipitation reagent and stir. Incubate at + 40~C for exactly 30 minutes and filter immediately with filter paper (Whatman 1 or Macherey Nagel 640 we).

Pipette 2 ml of fi7tr~te, 5 ml of 0.55 M
Na2C03 solution and 1 ml of phenol reagent.
stir and incubate at +40~C ~or 30 minutes.
Cool to room temperature and measure the absorbance at 660 nm against distilled water.

2. Enzyme blank Equilibrate 1 ml of enzyme dilution (in 0.02 M NaCl solution) at +40~C (for about 5 minutes). Add 5 ml of precipitation reagent, stir and incubate at +40~C for exactly 30 minutes. Add 5 ml of casein substrate, ~tir and incubate at +40~C for exactly 30 minutes.

S~ i"~ SUEE !~ LE ~6t ;

-~W096l05739 2 1 9 6 7 6 0 I~ 5 ll Filter 1 -'1at~ly with filter paper (Whatman 1 or Macherey Nagel 640 we).

Treat the filtrate as the enzyme sample.

The ~h9nrh~nn~ difference between the enzyme sample and the enzyme blank should be 0.2-0.5.

3. Standard curve Prepare a tyrosine stock solution by weighing 10 mg of L-tyrosine into a volumetric flask, dissolve in 0.02 M NaC1 solution and fill to 100 ml with 0.02 M Nacl solution.

Prepare dilutions from tyrosine stock solution in 0.02 M NaCl solution as follows:

1:50 = 2 ~g/ml 1:20 = 5 ~g/ml 1:10 = 10 ~g/ml 1:5 = 20 ~g/ml 1:3 e 33 ~g/ml 1:2 = 50 ~g/ml Pipette 2 ml of each tyrocine dilution, 5 ml of 0.55 M Na2C03 solution and 1 ml of phenol reagent. Stir and incubate at +40~C for 30 minutes. Cool to room temperature and S~BSTlTl~'TE Sr:EE- ~ll' E

. .. . . .

W096105739 2 1 9 6 7 6 ~ 7~

l~L , measure the ~hSnrh~nre at 660 nm against distilled water.

Plot tyrosine Conr~ntratiorL 2S a function of ~h~nrh~nre.

~alculation The protease activity of the sample is calculated according to the following rr~ t;nn Activity (U/g) = rA(X) - A(o)l x k x F x Df t wherein:

A(X) = ~h~nrh~nce of the enzyme sample A(O) = ~hcrrh~nre of the enzyme blank k = the slope oi the standard curve F = reaction ~ tirn factor (= 11) Df = dilution ~actor (ml/g) t = reaction time (30 minutes) ARS~Y M~t~nd for ~-Glur~n~e Activity One unit of ~-glucanase activity is the amount of enzyme which liberateg one ~mol of rr~llr;nr~ sugars (expressed as glucose equivalents) from the substrate in one minute under the conditions described.

~nnnEs~ E~(ril:LE2~i ~W096/05739 2 ~ 9 6 760 i~ 77 Reagents 1. 1.0% (w/v) ~-glucan substrate Moisten 1.0 g of mixed-linked ~-(1,3)(1,4)-glucan (siocon Biochemicals Ltd.) with 10 ml of ethanol. Add about 80 ml of distilled water and warm up to boil. ~nt; nnP boiling with vigorous stirring until ~-glucan is dissolved and a turbid solution is obtained.
Cool the turbid solution to room temperature c~nt;n~nusly stirring and adjust the ~-glucan r~nr~ntration to 1.0~ (w/w) by adding distilled water. Filter through a glass fibre filter paper.

The substrate can be used ; ~;~t~ly, The substrate i5 usable for two days if stored in a cold room.

2. 0.1 M sodium acetate buffer, pH 5.0 A. Dissolve 8.2 g of anhydrous sodium acetate in distilled water and fill to 1000 ml with distilled water.

B. Dissolve 6.0 g of glacial acetic acid in distilled water and fill to loO0 ml with distilled water.

S~BS~iTlJTE SHEET ,~ LE ''6 W096~5739 2 1 9 6 7 6 0 r~

Ad~ust the pH of solution A to 5.0 with solution B.

3. Dinitrosalicylic acid (DNS) reagent Suspend 20.0 g of 3,S-dinitrosalicylic acid in about 800 ml of distilled water. Add gradually 300 ml of sodium hydroxide solution (32.0 g of NaOH in 300 ml of distilled water) while stirring ~nt;nnously. Warm the suspension in a water bath (the temperature may not exceed +48~C) while stirring until the solution is clear. Add grA~31lA13y 600 g of potassium sodium tartrate. Warm the solution ~the temperature may not exceed +48~C) if needed until solution is clear.

Fill to 2000 ~1 with distilled water and filter through a coarse sintered glass ~ilter.

Store in a dark bottle at room temperature.
The reagent is stable for a maximum of 6 months.

Procedure 1. Enzyme sample Equilibrate 1 ml of enzyme dilution (in 0.1 M
sodium acetate buffer, pH 5.0) at +30~C. Add 1 ml of ~-glucan substrate, stir and ; n~llhat~

St~BSrlrlJTE SH~L~ LViE

~W096/05739 2 1 9 6 7 6 0 r~

at +30~C for exactly 10 minutes. Add 3 ml of DNS-reagent, stir and boil the reaction mixture for exactly 5 minutes. Cool the reaction mixture in a cold water bath to room temperature and measure the ~h~nrh~nre at 540 nm against distilled water.

2. Enzyme blank Tn~llhate 1 ml of ~-glucan substrate at +30~C
for 10 minutes. Add 3 ml of DNS-solution and stir. Add 1 ml of enzyme dilution (in 0.1 M
sodium acetate buffer, pH 5.0) and stir.
Boil the mixture for exactly 5 minutes. Cool the reaction mixture in cold water bath to room temperature and measure the absuLbance at 540 nm against distilled water.

The absorbance difference between the enzyme sample and the enzyme blank should be 0.3-0.5.

3. Standard curve Prepare standard solutions from anhydrous glucose in distilled water. Glucose concentration in the standards should be 0.1-0.6 mg/ml. Pipette 1 ml of glucose standard aolution, 1 ml of distilled water and 3 ml of DNS-reagent into a test tube. Stir and boil s~es~TurE SHEET (~U.E 261 Wt~96l05739 2 ~ 9 6 7 6 ~ /~ . " ~

for exactly 5 minutes. Cool in a cold water bath to room temperature and measure the absorbance at s40 nm against standard blank.
In the standard blank, glucose solution is replaced by 1 ml of distilled water.
Otherwise standard blank is treated like glucose standard.

Plot glucose cnn~ntration as a function of Alsl~b~ e New standard curve is prepared for every new 3NS-reagent.

~alculation The ~-glucanase activity of the sample is calculated according to the following equation:

Activity(U/g) =(rAtXl-AtO~l x k + C.) x 1000 x D~
M~tglU X t wherein:

A(X) = AhS~rhAn~e of the enzyme sample A(O) = absorbance of the enzyme blank k = the slope of the standard curve t_ = the intercept of glucose standard curve 1000 = factor, mmol -> ~mol Df = ~ilut;~n factor (ml/g) S[I~ST!~TE SH EI ~RU' E ~6') 2 1 q6760 ~0 9610S739 MWglu = molecular weight of glucose (180.16 mg/mmol) t = reaction time ~10 minutes) Based upon the above considerations, it is an object of the present invention to provide an enzyme feed additive for improving the FCR and/or increasing the digestibility of a cereal-based feed.

Accordingly, the present invention provides an enzyme feed additive comprising:

~i) a xylanase;

~ii) a protease; and optionally ~iii) a ~-glucanase wherein the ratio of the units of xylanase activity per g of the feed additive to the units of ~-glucanase activity per g of the feed additive is 1:0-0.25.

It has been found that the inclusion of the above enzyme feed additive in the diet of an animal enables the animal to digest the diet more efficiently. Thus, the addition of the additive to a feed increases the proportion of feed protein and energy which the animal can derive from the feed. This in turn improves the FCR of the feed making it more econom~cal in ~se.

SUESTITUTESHEET(RULE26) W096/05739 2 1 9 6 7 6 0 1 ~l/r r . / I ~

It i8 also possible to utilise this aspect of the present invention by modifying a conv~nt;nncl feed by reducing its energy, and/or protein, and/or amino acid content whilst simultcn~n--cly ~;nt~n;ng the same nutritional levels of energy, protein, and amino acids available to the animal.
This means that the amounts of costIy energy and protein supplements convPntinnclly included in an animal feed can be reduced as compared to conventional feeds. Energy 5nrrlPmPntc include fat. Protein supplements include fish-meal, meat-meal, soya-bean, rapeseed or canola. This results in a significant reduction in the cost per unit weight of the animal feed without decreasing its nutritional value.
Alternatively, or even additionally, the amounts of amino acid supplements can be reduced as ~ ~ --ed to conv~nt~n feeds which can also result in significant cost savings.

The en~yme feed additive according to the present invention can be prepared in a number of ways. For instance, it can be prepared simply by mixing different enzymes having the appropriate activities to produce an enzyme mix. This enzyme mix can be either mixed directly with a feed, or more conv~ntinnclly impregnated onto a cereal-based carrier material such as milled wheat, maize or soya flour. Such an impregnated carrier also constitutes an enzyme feed additive in accordance with the present invention.

As an alternative, a cereal-based carrier formed from e.g.
milled wheat or maize can be impregnated either simultaneougly or seqn~nt;clly with enzymes having the SUBS~nESH~(P.U!t2~

WO 96/05739 . ~, I 11 1 - I I
~ 219676~

~Lu~Liate activities. For example, a milled wheat carrier may be sprayed firstly with a xylanase, secondly with a protease, and optionally finally with a ~-gl~lc~nCce. The carrier material impregnated with these enzymes also constitutes an enzyme feed additive in accordance with the present invention.

The feed additive of the present invention may be mixed directly with the animal feed, or alternatively mixed with one or more other feed additives such as a vitamin feed additive, a mineral feed additive and an amino acid feed additive. The resulting feed additive including several different types of components can then be mixed in an iate amount with the feed.

The feed additive of the invention including the cereal-based carrier is normally mixed in amounts of 0.01-50 g per kilo of feed, more preferably 0.1-lO g/kilo and most preferably about 1 g/kilo.

An alternative way of preparing the enzyme feed additive of the present invention is to construct by recombinant DNA
technir~ues a microorganism which produces the desired enzymes in the desired relative amounts. This can be done for instance by increasing the copy number of the gene ~ncr,~;ng xylanase and/or by using a suitably strong promoter in front of the xylanase gene. Alternatively or additionally the mi~LuuLy~llism strain can be deleted for certain cellulase genes especially endoglucanases.

~UBS~ IT~ S"EET (~ULE 26) 21 9676~ ~
W096io5739 I~

The enzyme feed additive provided by the present invention may also include other enzymes such as one or more of an a-amylase, a glucoamylase, a pectinase, a ~nnAn~Re, an ~-galactosidase, a phytase and a lipase. Enzymes having the desired activities may for instance be mixed with the xylanase and protease either before impregnating these on a cereal-based carrier or alternatively such enzymes may be impregnated simult~nPon~ly or se~lPr~ ly on such a cereal-based carrier. The carrier is then in turn mixed with a cereal-based ieed to prepare the final feed. It is also possible to formulate the enzyme feed additive as a solution of the individual enzyme activities and then mix this solution with a feed material pre-formed as pellets or as a mash.

It is also possible to include the enzyme feed additive in the animal's diet by incorporating it into a second (and different) feed or drinking water which the animal also has access to. Accordingly, it is not essential that the enzyme mix provided by t~e pre8ent i~vention is incorporated into the cereal-based feed itself, although such incorporation forms a particularly preferred aspect of the present invention.

The enzyme mix provided by the present invention includes a xylanase as an essential r~mronPn~. This xylanase can be ~h~;n~d from a bacterium such as Bacillus, Streptomyces, C108tridium, Th~rm~nnsprra, ~icrotetra-~pora, or ~uminococcus. However, it is more preferred that the xylanase is obtained from a fungus such as ~rirhr~Prr-, S~i5STlr~ HEFr l~!UL~ 26i ~ 096/OS739 2196760 r~ 1 5 ll Aspergillu6, Humicola or Neo~7 7 i~-ctix. It is particularly preferred that the xylanase i8 the low pI xylanase (pI=5.2) and/or the high pI xylanase (pI=9.0) obtained from Tri~h~Pr~- longibrachiatu~ obtainable by the method of Example 22 of W0 92/06209. It is particularly preferred that the xylanase is the high pI xylanase. Such a xylanase composition has a ratio of units of xylanase activity per unit amount to the units of ~-glucanase activity per same unit amount of about 1:0.005. The xylanase may be a mutant xylanase having an amino acid sequence not found in nature, such a sequence corresponding to that of a naturally occurring xylanase m~; f; Pd by inserting, deleting or r~pl~r; ng one or more amino acid residues in the naturally occurring xylanase.

It is readily understood by those skilled in the art of enzyme production that enzyme ~ ~-rit;onC such as those described herein can be prepared by several different methods. For example, an enzyme composition including a xylanase and possessing only a limited amount of ~-glucanase activity, can be produced by genetically PnginPpring a host organism expressing such xylanase such that undesired genes are deleted or r-'; f; ed to inactivate the gene or the expression product therefrom Additionally, the enzyme composition may be prepared by purification methods such as purifying a specifically desirable activity (xylanase) from a whole ~pllnl~qe complex. Suitable methods are described in W0 92/06209. Other purification methods which are described in US Patent 5,328,841 include purification using polyethylene glycol and the like. Likewise, such enzy~e compositions may ~1 }B~ ,',Ul ~ 2~

W096~S739 2 1 ~6760 ~ " ~

be prepared by fel ~t;nn optimization procedures whereby the ratio of enzyme component activities can be modified by variation of the pH, temperature, carbon source, or ~;n~tinnc of these, during the ferm~nt=tinn pLuceduLe~

According to a most preferred aspect of the present invention, the xylanase is from T. long;hrarh;~tum over-expressing high pI or low pI xylanase produced from a transformed host that is lacking one or more of functional endoglucanase I (EGI), flm~t;nn~l endoglucanase II (EGII), functional cellobiohydrolase I (CBHI) and fnn~tinn~l c~llnhinhydrolase II (CBHII). The preparation of such transformed hosts and the pr-n~n~t;nn of high and low pI
xylanases is described in W0 92/06209 r- -;nn~d above.

The xylanase which results from such a host has significantly lower levels of enzymes possessing i3(1,4)-glucanase activity compared to xylanases obtained from naturally occurring sources. By using such a host, an enzyme composition can be o~tained including cnly 0.005 units of ~-glucanase activity per unit amount compared to 1 unit of xylanase activity in the same unit amount. In a preferred aspect of this invention, the enzyme feed additive includes a ratio of xylanase activity to 3-glucanase activity of 1:0-0.01 and more preferably 1:0-0.005.

The ratio of the units of xylanase activity per g of the feed additive to the units of protease activity per g of the feed additive is pre~erably 1:0.001-1,000, more preferably 1:
0.01-100 and most preferably 1: 0.1-10.

s~5S~r~ H~t~ iL~2~' ~W096~,s739 2 19 6 7 6 0 r~rrs~l( "

The enzyme mix provided by the present invention also ~ includes a protease as an ~ss~nt;~l cnmrnn~nt. It is preferred that the protease is a subtilisin which can be derived from the genus R_i~i77~-q, such as the strains including but not limited to Bacillus a~yloli~uefaciers, Bacillus lentus, Bacillus liche~iforrris, Bacillus suotilis, or Bacillus alcalophilus.

Suitable proteases include but are not limited to the following commercially available proteases: Novo NEUTRASE
(TM) ( ~ially available from Novo Nordisk); PURAFECT
(TM) (commercially available from ~n~nnor Tnt~rni~t;nn~l, Inc); SAVINASE (TM) (commercially available from Novo Nordisk); MAXACAL (TM) (~ ially available from Gist-Brocades); DURAZYM (TM) (c --~ially available from Novo Nordisk); and MAXAPEM (TM) ( ~~oially available from Gist-Brocades).

The subtilisin may also be a mutant subtilisin having an amino acid sequence not found in nature, such a sequence corr~srnn~;ng to that of a naturally occurring subtilisin modified by inserting, deleting or r~rl;in;ng one or more amino acid residues in the n~tn~lly occurring subtilisin.
Suitable mutant subtil;c;n.q are described in EP-A-0130756 (corrPqpnnRi;ng to US-Re-34606) ~including ~ltat;nnq at position +155, +104, +222, +166,+33, +169, +18g, +217, +156, +152); EP-A-0251446; WO91/06637 etc. The most preferred subtilisin is a mutant subtilisin which comprises a substitution at the amino acid residue position equivalent to Sl~ "'F- ''r7' i r ri~

. _ _ _ _ _, _ _ _ _ . .. .. .. _ . . _ . .. . .. .

W096/05739 2 1 9 6 7 6 0 ~ 7 l l ~

tyr+217 of the subtilisin obtainable from .72~;ri 7 777,A
a77yloliqLefacie~G with leucine.

Methods of producing such mutant subtiliR;n-A are described in detail in the publications US-Re-34606 and FP-A-0251446.

The protease which is ~nrlU~pd in the enzyme mix of the present invention should be free or relatively free of ~-glucanase activity. This is to ensure that the resulting enzyme feed additive prepared by mixing the protease with the xylanase as previously described has the low or nil level of desired ~-glur;inA~ie activity. This is less of a problem than with the xylanase , Ant of the feed additive because mi~LuoL~lisms which naturally produce proteases do not n~rARs7irily produce high levels of ~-glucana3es.

It is found that the , ';n,At;~n of the xylanase and the protease provided aG the enzyme feed additive of the present invention have complementary and synergistic efficacies in terms of their ability to aUgment each other's effects to provide the advantages obtainable by the present invention of reducing the FCR oi' cereal-based animal feeds.

As mentioned above, the enzyme mix provided by the present invention is preferably for use as a feed additive in the preparation of a cereal-based feed.

According to a further aspect of the invention, this cereal-based feed comprises at least 2S~ by weight, more preferably at least 35~ by weightl of wheat or maize or a combination of ~ULSTIll.rTl: SHEFI (RllLE 2~1 . , . . .. . _ .. . .. .. .. , .. .. . _ _ _ _ .

~ W096~5739 2 1 9 6 7 6 0 ~ nt~17 both of these cereals. The feed further comprises a xylanase in such an amount that the feed includes 100-100,000 units of xylanase activity per kg.; a protease in such an amount that the feed includes 100-100,000 units of protease activity per kg.; and optionally a ~-glucanase. The ratio of the units of xylanase activity per kg. of the feed to the units of ~-glucanase activity per kg. of the feed falls within the range 1:0-0.25.

Preferably, the amount of feed additive added to the feed is such that the resulting feed comprises respectively 1,000-10,000 units of both xylanase activity and protease activity per kg.

In a further aspect of the invention, a cereal-based feed is provided which comprises at least 25~ by weight of wheat and/or maize and lOO-100,000 units per kg. of a mutant subtilisin comprising a substitution at the amino acid residue position equivalent to tyr+217 of the subtilisin obtainable from Bacillus amyloliguefacie~s with leucine.

Cereal-based feeds according to the present invention are suitable for animals such as turkeys, geese, ducks, pigs, sheep and cows. The feeds though are particularly suitable for poultry and pigs, and in particular broiler chickens.

The present invention in a further aspect provides the use of a composition including the low pI xylanase andtor the high pI xylanase obtainable from Trirh~rm~ lon~ibrachiatum and optionally a ~-glucanase as a feed additive characterised in .S~ EFr ~1~ r ~

_ _ _ _ _ _ _ _ _ , . . .. . _ _ .

W096/05739 ~ 9 6 7 6 0 F~

that the ratio of the units of xylanase activity per g of the composition to the units of ~-glucanase activity per g of the composition is 1:0-0.25.

The above use of the composition as a feed additive produces a cereal-based feed having an ; ~ uv~d FCR. According to a further aspect ~of the present invention, such a feed comprises (i) at least 25~ by weight of wheat and/or maize;
and (ii) the high pI xylanase and/or the low pI xylanase obtainable from Trirh~rr' longibrac~iatum in such an amount that the feed ;nr~ 100-100,000 units of xylanase activity per kg.

The above use and cereal-based feed incorporating the high and/or low pI xylanase enables the animal to digest its feed more efficiently. Thus, the addition of such a xylanase r~n~;n;ng feed~additive to a feed increases the proportion of feed protein and energy which the animal can nutritionally derive from the feed. This in turn improves the FCR of the feed making it more economical in use. The ieed additive in~ ing such a xylanase can of course be produced in the same way as the feed additives previously described.

The present invention is further explained by way of the following Examples.

r le 1 Cobb male broiler chickens were fed with the wheat-based starter feed set out in Table 1 below up to 21 days of age.

SuB~~ !Es!~ 2G~

~ 096/05739 2 1 q 6 7 6 0 . ~ . "

Table 1 Ingredients C~nr~ntration (g/kg) Wheat 637.1 Soybean meal 300.0 Limestone 13.3 Dicalcium Phnsrh~te13.0 DL-Methionine 3.1 Arginine 1.2 L-Lysine ~Cl 1.3 Vitamin mix 1.0 Mineral mix 1.0 Corn Oil 35.0 Salt 4.0 Calculated Composition ME Kcal/kg 3004.0 CP ~ 22.8 Calcium ~ 0.87 Available Phosphorus0.40 th;~n;n~ 0.64 ~th; ~n; n~ + Cystine1.01 Lysine 1.29 The above starter diet of the chickens was supplemented by varying amounts of xylanase obtained from Trirh~rm~ viride and/or a ~-glucanase obtained from Trirhr~rr-longibrachiatum. The T. viride was a strain mutated and SlJBSTlrs~L SHi. ET (RULE 26~

W096/0s739 2 1 96760 ~ 777 ~

selected for relatively high xylanase activity such that it produces 55 units of ~-glucanase activity to l,OOo units of xylanase activity per unit amount. The chickens were divided into 24 separate groups with 30 birds in each group. The diets of the 24 groups were supplemented by one of the 'in~ti~nC cf o, 500, l,000, 2,000, 4,000 and 8,000 units/kg of xylanase; and 0, 250, 500 and 1,000 units/kg of ,B-glucanase.

The feed conversion ratio for each of these trials was r ht~inr~ and the values of this are set out in the following Table 2:
Table 2 ~-glucanase 0 250 500 l,000 Average (units/kg) added Xylanase (units/kg) 0 1.54 1.54 1.48 1.53 1.52 500 1.52 1.51 1.51 1.50 1.51 lO00 1.47 1.49 1.52 1.54 1.51 2000 1.45 1.48 1.51 1.49 1.48 4000 1.50 1.51 1.46 1.49 1.49 8000 1.55 1.58 1.54 1.51 1.55 It is evident from the data set out in the above Table 2, that the presence of ~-glucanase activity disadvantageously increases FCR values particularly, at the optimum xylanase level of around l,000 - 3,000 units/kg.

SUBSl ITU~ S~'EET ~Rl' E

~W096/05739 2 1 9 6 7 6 0 r-ll~9 l~777 From the results set out in the above Table 2, it is concluded that the units of xylanase activity present in the feed should be at lea~t four times greater than the units of ~-glucanase activity in order that an imp~uv~ in the FCR
value can be obtained. Preferably the units of xylanase activity should be at least 100 times greater than the units of ~-glucanase activity, and more preferably at least 1,ooo times greater.

E le 2 Several groups of Ross 1 broiler chickens (mixed sex) were fed the starter and finisher diets set out in Table 3 below for days 0-21 and 22-42 of their life. Each of these groups included 90 birds.
Table 3 Ingredie~t (kg/t) Starter Finicher Wheat 612.2 668.9 Soyabean meal 48~ C.P. 318.8 240.9 Soya oil 32.6 55.4 Salt 3.03 3.01 DL methionine 2.01 0.4 Limestone 13.8 14.7 Dicalcium ph~sph~te 12.5 11.7 Vitamin/mineral 10.0 10.0 supplement SUBST~ E SHLrET ~RULE 2 W096~5739 2 1 9 6 7 6 0 ~ " ~

Calculated analysis(~) Starter Finisher Crude protein 23.0 20.0 Calcium 0.90 0 90 Total rhn.srhnrus 0.67 0.63 Available rhnsrhnrus 0.42 0.40 Fat 4.63 Ç.82 Fibre 2.58 2.46 Lysine 1.21 0.99 Methionine 0.54 0.33 Sodium 0.15 0.15 Potassium 0.92 0.78 Chloride 0.24 0.24 A control group of broiler chickens did not have their diets supplemented by any enzymes. A second group Z had their diets supplemented by 3,000 units/kg of high pI xylanase produced from a transformed strain of T. 7rn~ihr~rh;~tum lacking functional EGI, EGII, CBHI and CBHII as described in Wo 92/06209. Groups A, C, E had their diet supplemented with the same xylanase, and in addition by 2,000, 4,000 and 6,000 units/kg respectively of Novo Neutrase (TM) obtained from Novo Nordisk. Groups B, D and F had their diets supplemented with the same high pI xylanase, and in addition by 2,000, 4,000 and 6,000 units/kg respectively of a mutant subtilisin which is substituted at the amino acid residue position e~uivalent to tyr+217 of Bacilius amyloligue~aciens substilin with leucine as described in the US-Re.-34606. The results of these tests are set out in the foIlowing Table 4.

SUB~lr~ S~EF ! ~U'.~.2~

~ 096/05739 2 1 9 6 7 6 ~ r l,~ "

Table 4 Group Control Z A B C D E F
group Final Body 2.21 2.20 2.20 2.20 2.22 2.19 2.23 2.20 weight, kg Feed 93.1 94.5 94.6 92.4 93.2 92.2 94.2 92.7 Intake, g per bird per day FCR 1.85 1.85 1.85 1.82 1.85 1.82 1.82 1.82 (mortality adjusted) From the above data, it can be calculated that the average FCR when using the xylanase and the protease Novo Neutrase is 1.84. On the other, the average FCR when using the xylanase and the mutant subtilisin protease of the prese~t invention is 1.82. Each of the groups Z and A-F give rise to FCR
values which are either equal to or superior to that obtained from the control group.

Ex~le 3 Two groups of Ross 1 male broiler chickens were each fed the wheat-based starter feed set in Table 1 o~ Example 1 for days 0-7. The starter feed was not supplemented with any antibiotic, anticoccidial or any enzyme.

SU~snn~ESH.

W096l05739 2 1 9 6 7 6 0 . ~11~ . " ~

For days 7-21, each group was fed the basic wheat-based feed set out in the following Table 5 in the form of a mash:

Table 5 Ingredient Amount (wt.~) Soft wheat 65.5 Soybean meal 48% C.P.27.3 Soy oil 3.1 Salt 0.3 DL me~;~n1n~ 0.2 Limestone 1.4 Dicalcium phosphate1.2 Vitamin/mineral 1.0 S~rrl ~ ~

A firEt control group of the chickens did not have their diet supplemented by any enzymes. The above wheat-based feed fed to the second test group was snrrlpm~ntpd with enriched low pI xylanase obtained from a Tri~h~rr~ longibrachiatum strain lacking functional EGI, EGII, CBHI and CBHII as described in W0 92/06209. The xylanase inclusion level in the wheat diet was 184 units/kg. The control group had an average FCR of 2:.00. In contrast, the test group fed the feed ~nrP~' 'P~ with low pI xylanase had an FCR of 1.89.
Such a reduction in the FCR of the feed by addition of the xylanase indicates that the nutritional performance of the feed is improved.

SlJBSr!~E SHEET !~ULE 2 ~ 096~5739 21~6760 p~"~ "

E le 4 Six groups each cnn~in;ng 12 castrated male pigs of PIC
commercial yenu~y~e were respectively fed 8iX different diets ad libitum in pellet form to assess the effect of enriched high pI xylanase obtained by Tric~oderma longihr~hi~tum. At the start of the trial the pigs were all around 10 weeks of age. Thus, three basic feeds have a different maize/wheat ratio were fuL l~ted in accordance with the following Table 6 in which the amounts of the various ~c are expressed in terms kg/t of the feed.

Table 6 20~ Wheat 40~ Wheat 60~ Wheat diet diet diet Maize 424 224 19 Wheat 200 400 600 Wheat ~ l ingC 100 100 100 Soyabean meal 200 200 200 (44) Meat and bone 50 50 50 meal Canola oil - - 5 L-Lysine HCl 1.35 1.15 0.95 Vitamins ~ 25 25 25 Minerals Each diet was tested either as a control (without enzyme suppl: ~ ~tion), or supplemented with 6,270 units of xylanase per kg of feea. The xylanase tested is an enriched u~ L~ 2~

W096~5~9 21 96760 ~11~ . " ~

high pI xylanase obtained from a Tri~h~pr~- longibrachiatum strain lacking functional EGI, EGII, CBHI and CBHII as described in WO 92106209.
The results of these various tests are set in the following Table 7.
Table 7 Wheat(~) 20 40 60 Maize(~) 42 22 2 Control Feed Control Feed Control Feed feed plus feed plus feed plus xylanase xylanase xylanase Start 22.9 22.6 21.8 21.8 2~.6 23.4 Weight (kg) Finish Weight 75.0 82.7 78.7 82.2 78.8 82.8 (kg) 3aily 930 1073 1015 1076 974 1061 gain (g) Daily 2546 2773 2680 2638 2826 2942 feed intake (g) FCR 2.76 2.59 2.68 2.472.93 2.81 It will be seen from the results set out in Table 7 that the addition of the xylanase significantly improved daily live weight gain by an average of 9~ in f;r;~Pr pigs offered diets c~nt~;n;n5 60~ ~y weight of cereals formed from different proportions of maize and wheat. Overall, both feed intake and the FCR were gignificantly improved.

~ .n~SH~ UL~

~W096~5739 2 1 9 6 7 6 0 E1~AnU?1e 5 Four groups of Nicholas male turkey poults were fed the maize-based starter feed ~ ;h~ in Table 8 in the form of a mash up to 21 days of age.
Table 8 Ingredient Amount ~wt.~) Maize 36.65 Soybean meal (45.6~ CP) 55 4 Animal-vegetable fat 3.2 Dicalcium rhosphAte 2.3 Limestone 1.5 Mineral premix 0.3 Vitamin premix 0.3 Sodium chloride 0.15 DL meth; ~n; n~ O . 2 The first control group were fed the feed of Table 8 unsupplemented. The feeds of three other test groups were ~urpl~ -ntGd respectively with 2,000 units/kg, 4,000 units/kg and 6,000 units/kg of a mutant subtilisin substituted at the amino residue position equivalent to tyr+217 of the Bacillus amyloliguefaciens subtilisin with leucine as described in US-Re.-34606. The results of these tests are set out in the following Table 9.

SLI~;~uTE ~'~FE7 ~Flt~'.'' ?6) W096~S739 2 1 9 6 7 6 0 P~ 5 ~ ~

.

Table g Dietary Treatment 21-day Body Weight FCR
(gra~ns/poul t) Control Feed 570 1.39 Feed + 2000 U/kg 543 1.37 of protease Feed + 4000 U/kg 570 1.36 of protease Feed + 6000 U/kg 566 1.35 of protease From the above data, it can be seen that increasing contents of the protease when added to the feed has the b~n~f;~
result of reducing the FCR of the feed.

The e__ect demonstrated above of improving FCR values can be obtained when feeds prepared in accordance with the present invention are fed to animals such as geese, ducks, sheep and cows, as well as to chickens, turkeys and pigs.

su~s~r~ SHE~ ~ E~

Claims

Claims:

1. An enzyme feed additive comprising:

(i) a xylanase;

(ii) a protease; and optionally (iii) a .beta.-glucanase wherein the ratio of the units of xylanase activity per g of the feed additive to the units of .beta.-glucanase activity per g of the feed additive is 1:0-0.25.

2. An enzyme feed additive according to claim 1, wherein the xylanase is obtained from a bacterium.

3. An enzyme feed additive according to claim 2, wherein the bacterium is Bacillus, Streptomyces, Clostridium or Ruminococcus.

4. An enzyme feed additive according to claim 1, wherein the xylanase is obtained from a fungus.

5. An enzyme feed additive according to claim 4, wherein the fungus is Trichoderma, Aspergillus, Humicolas or Neocallimastix.

6. An enzyme feed additive according to claim 5, wherein the xylanase is the low pI xylanase and/or the high pI
xylanase obtainable from Trichoderma longibrachiatum.

7. An enzyme feed additive according to claim 6, which comprises the high pI xylanase.

8. An enzyme feed additive according to claim 1, wherein the xylanase is a mutant xylanase having an amino acid sequence not found in nature, such a sequence corresponding to that of a naturally occurring xylanase modified by inserting, deleting or replacing one or more amino acid residues in the naturally occurring xylanase.

9. An enzyme feed additive according to any preceding claim, wherein the protease is a subtilisin.

10. An enzyme feed additive according to claim 9, wherein the subtilisin is derived from the genus Bacillus.

11. An enzyme feed additive according to claim 10, wherein the subtilisin is derived from Bacillus amyloliquefaciens, Bacillus lentus, Bacillus licheniformis, Bacillus subtilis, or Bacillus alcalophilus.

12. An enzyme feed additive according to claim 9, wherein the subtilisin is a mutant subtilisin having an amino acid sequence not found in nature, such a sequence corresponding to that of a naturally occurring subtilisin modified by inserting, deleting or replacingone or more amino acid residues in the naturally occurring subtilisin.

13. An enzyme feed additive according to claim 12, wherein the mutant subtilisin comprises a substitution at the amino acid residue position equivalent to asn+155, tyr+104, met+222, gly+166, ser+33, gly+169, phe+189, tyr+217, glu+156, or ala+152 of Bacillus amyloliquefaciens substilisin with one of the other 19 naturally occurring amino acids.

14. An enzyme feed additive according to claim 13, wherein the mutant subtilisin comprises a substitution at the amino acid residue position equivalent to tyr+217 of Bacillus amyloliquefaciens subtilisin with leucine.

15. An enzyme feed additive according to any preceding claim, wherein the ratio of the units of xylanase activity to .beta.-glucanase activity is 1:0-0.01.

16. An enzyme feed additive according to claim 15, wherein the ratio of the units of xylanase activity to .beta.-glucanase activity is 1:0-0.005.

17. An enzyme feed additive according to any preceding claim, wherein the ratio of the units of xylanase activity per g of the feed additive to the units of protease activity per g of the feed additive is 1:0.001 -1,000

18. An enzyme feed additive according to any preceding claim, further comprising at least one of .alpha.-amylase, glucoamylase, pectinase, mannanase, .alpha.-galactosidase, phytase and lipase.

19. An enzyme feed additive according to any preceding claim, further comprising a carrier.

20. An enzyme feed additive according to claim 19, wherein the carrier is milled wheat, maize, soya or a by-product of any of these materials.

21. The use of an enzyme feed additive according to any preceding claim, for improving the feed conversion ratio and/or increasing the digestibility of a cereal-based feed.

22. A cereal-based feed comprising (i) at least 25% by weight of wheat and/or maize; (ii) a xylanase in such an amount that the feed includes 100-100,000 units of xylanase activity per kg.; (iii) a protease in such an amount that the feed includes 100-100,000 units of protease activity per kg.; and optionally (iv) a .beta.-glucanase; wherein the ratio of the units of xylanase activity per kg. of the feed to the units of .beta.-glucanase activity per kg. of the feed is 1:0-0.25.

23. A cereal-based feed according to claim 22, which comprises 1,000-10,000 units of xylanase activity per kg. and 1,000-10,000 units of protease activity per kg.

24. A cereal-based feed according to claim 22 or claim 23, comprising at least 35% by weight of wheat and/or maize.

25. A cereal-based feed comprising at least 25% by weight of wheat and/or maize and 100-100,000 units per kg. of a mutant subtilisin comprising a substitution at the amino acid residue position equivalent to tyr+217 of the subtilisin obtainable from Bacillus amyloliquefaciens with leucine.

26. A cereal-based feed comprising (i) at least 25% by weight of wheat and/or maize; and (ii) the high pI
xylanase and/or the low pI xylanase obtainable from Trichoderma longibrachiatum in such an amount that the feed includes 100-100,000 units of xylanase activity per kg.

27. Use of a cereal-based feed according to any of claims 22-26 as a poultry feed or as a pig feed.

28. Use of a composition including the low pI xylanase and/or the high pI xylanase obtainable from Trichoderma longibrachiatum and optionally a .beta.-glucanase as a feed additive, characterised in that the ratio of the units of xylanase activity per g of the composition to the units of .beta.-glucanase activity per g of the composition is 1:0-0.25.