TECHNICAL FIELD

This invention relates to a method of altering the composition of animal waste, and devices and feed stock for use in the method. BACKGROUND ART

One of the major environmental issues surrounding intensive farming practices is the release of nitrogen containing compounds into the environment.

Nitrogen is an important component in pastures for the growth and health of plants and soil microorganisms. However, the decay of organic matter such as from plant and animal wastes adds nitrogen to the soil largely in organic forms which plants are unable to use. Microorganisms present in the soil have the ability to convert the organic forms of nitrogen to inorganic forms such as nitrate which can then be taken up by plant roots to generate new organic matter. This conversion of nitrogen is termed The Nitrogen Cycle. Organic and inorganic forms of nitrogen may also be added to the soil through the addition of fertilisers to pasture.

Nitrogen containing compounds are a significant component in animal waste, particularly urine. Intensive farming practices such as dairying release a large quantity of urine- derived nitrogen to the soil, largely in the form of urea. Large amounts of nitrogen are however lost from the soil through a number of mechanisms, affecting the productivity of pasture and leading to environmental concerns. Therefore, improved systems to reduce the conversion of nitrogen would be of benefit.

There are a number of different methods and devices known to administer compounds to prevent conversion of nitrogen compounds. These have a number of inherent problems or difficulties. Therefore, it would be an advantage to have methods, devices, and feed stocks which address those problems.

In addition, it is an object of the invention to optimise the amounts of compounds used to reduce or eliminate conversion of nitrogen compounds, while achieving a meaningful reduction in conversion of the nitrogen compounds.

Alternatively, it is an object of the invention to provide methods, devices and feed stocks which can account for different factors such as environmental conditions, land parameters, and/or differences in animal metabolism and gestation.

Alternatively, it is an object of the invention to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

There is provided a method for decreasing the conversion of nitrogen in animal waste involving the step of introducing internally to an animal a treatment substance, delivery devices configured to deliver internally to an animal a treatment substance, and feed stocks containing a treatment substance.

There is provided a delivery device for decreasing the conversion of nitrogen in animal waste, wherein the delivery device is configured to introduce DCD internally to an animal to achieve an excretion rate for the DCD in the animal's urine of at least substantially 7 kilograms per hectare.

There is provided a method of altering the composition of animal waste, the method including the step of introducing DCD internally to an animal such that animal waste acts as a carrier so that the DCD affects the conversion of nitrogen containing compounds once the waste has been excreted from the animal, wherein the DCD is introduced internally to the animal to achieve an excretion rate for the DCD in the animal's urine of at least substantially 7 kilograms per hectare. There is provided a feed stock for an animal, wherein the feed stock contains DCD at a concentration sufficient to achieve an excretion rate for the DCD of substantially 7 kilogram per hectare.

The invention described herein is an improvement to the method described in the Applicant's PCT Publication No. WO/2005/030247, the entire contents of which are incorporated herein by reference.

The term "animal waste" should be taken to mean any waste products excreted by the animal such as faeces and urine.

In embodiments of the invention the animal waste is urine. For ease of reference throughout this specification, the term "animal waste" will be referred to as urine.

However, this should not be seen as a limitation on the present invention in any way.

In embodiments of the invention the animal will be a farm animal and more preferably a dairy animal such as a cow. Once again, this should not be seen as a limitation as it is anticipated the present invention could be used on other intensively farmed animals such as beef cattle, sheep, goats and so forth, as well as other animal species, including humans.

The term "treatment substance" refers to any substance including at least one compound capable of directly or indirectly affecting the conversion of nitrogen containing compounds. In preferred embodiments of the present invention the treatment substance contains one or more active compounds such as a urease or nitrification inhibitor which affects the conversion of urea to ammonium, and ammonium to nitrate respectively. It is desirable to use inhibitors that can be used in small amounts, and which are nontoxic to the animal. The amount of inhibitor administered will be dependent upon a number of factors, including the choice of inhibitor, as well as the body weight of the animal. A number of urease inhibitors are known in the art which may find use in the present invention. For example, N-(n-butyl) thiophosphoric triamide (NBPT) is used

commercially under the trade name Agrotain™ and has been used with urea fertiliser to reduce ammonia volatilisation.

Acetohydroxamic acid has been used to control nitrogen metabolism in animals. Further, it should be understood that other substitutes or alternative urease inhibitors might also be used in the present invention.

In other preferred embodiments, nitrification inhibitors may also be used, alone or combination with urease inhibitors. For example, a nitrification inhibitor suitable is 3,4- dimethylpyrazole phosphate (DMPP), which has been shown to inhibit nitrification of fertiliser N when applied at relatively low rates and is non-toxic.

Another nitrification inhibitor which may find use is dicyandiamide (DCD).

The treatment substance may optionally also include one or more other beneficial compounds which function to improve or condition microorganisms already present in the soil, allowing them to better bind the excess nitrogen in urine excreted by animals. For example, tannins or other complex carbon sources can be used to enhance the immobilisation of nitrogen into soil organic nitrogen, for a more sustained release, a greater likelihood of overall plant recovery and reducing the high inorganic component prone to loss. For ease of reference only, the term "treatment substance" will now be referred to simply as a 'nitrogen process modifier'.

The term "nitrogen containing compound" should be taken to mean any compound which contains nitrogen as part of its chemical structure. In embodiments the nitrogen containing compounds include those found in urine, or produced during the conversion of urine such as urea, ammonium, ammonia and nitrate as well as nitrogen gases including nitrous oxides, and soluble organic forms.

In embodiments of the invention the animal waste is used as a carrier for the introduction of nitrogen process modifiers which affect the conversion of nitrogen containing compounds in the environment.

Delivering the nitrogen process modifiers to the environment via animal waste means no or little delay occurs in modifying the conversion of nitrogen containing compounds. Further, this ensures the nitrogen process modifiers are only delivered to the portion of pasture/soil on which the cow excretes waste such as by urinating and/or defecating, eliminating the need to apply the modifiers over a large area of pasture.

Further, introducing the nitrogen process modifiers internally to the animal eliminates the need for attaching devices to the exterior of the animal, which require regular maintenance to ensure they contain sufficient modifiers, have not been damaged, or have not become fouled or otherwise blocked. The nitrogen process modifiers (modifiers) of the present invention may be introduced to the animal by a number of mechanisms.

In embodiments of the invention the modifiers may be introduced to the animal through the digestive system of the animal. When delivering the modifiers via the digestive system, it is essential to ensure that modifiers maintain their activity and are not denatured or inactivated through the passage of the animal's digestive system.

In some embodiments, the modifiers may be encapsulated to provide protection against denaturation and subsequent absorption in the rumen or intestine.

For example, the delivery device may be in the form of a sustained slow release device administered orally to an animal such as a ruminal bolus or a bolus containing a rumen- stable delivery system which preferably includes an encapsulation system to deliver the modifiers post-ruminally. Such encapsulation systems are well known in the art, including but not limited to polymeric pH-dependent rumen-stable delivery systems, encapsulation by pH-sensitive polymeric coatings or other rumen-stable delivery systems such as heat or chemical treatment, low solubility analogues or lipid-based formulations. Wu S.H.W. and Papas A (1997 - Rumen-stable delivery systems. Advanced Drug Delivery Reviews 28: 323-334) describes a number of such delivery systems.

As understood by a person skilled in the art, a bolus is typically in the form of an elongate cylinder designed to slowly dissolve in the rumen of an animal.

One advantage of having sustained released devices is that the amount of modifiers released can be accurately known. This makes the treatment and the analysis of the effects of the treatment of the animal much more precise than previously.

The bolus will preferably be comprised of a solid matrix, coated with an impervious material having an opening through which the modifiers can be released, or a bio- erodeable coating which releases the modifiers as they are exposed. A wide variety of boluses and other delivery mechanisms are well known in the art and it is anticipated these technologies could readily be adapted by a skilled addressee for use in the present invention.

In other embodiments the modifiers may be introduced to the animal from a slow release device inserted into an animal's bladder by a farmer or veterinarian.

In an embodiment, the delivery device will comprise a solid, preformed stable matrix.

For example, the delivery device may be made of silicone matrix which is impregnated with the appropriate modifiers.

In one embodiment the introduction of the modifiers may occur by way of diffusion of those substances from the delivery device over a period of time.

The modifiers may alternatively be delivered through dissolution processes from the matrix or by the placement of appropriate modifiers within the inner core of the delivery device under various delivery systems. Such delivery systems are well known in the art.

In embodiments the delivery device may be bio-erodeable, obviating the necessity for the delivery device to subsequently be removed from the animal after treatment, which would require significant time and effort.

Other embodiments of the invention may utilise lipid-based delivery vehicles such as liposome-coated compositions, or other slow release matrices known in the art such as bio-erodeable wax coatings, synthetic polymers, cross-linked cellulosic compounds and so forth. For example, in some embodiments weakly acidic or basic co-monomers may be used which slowly release the modifiers during contact with urine.

The sustained release of the modifiers over time to an animal allows the modifiers to be excreted from the animal as a component of the urine, thus directly or indirectly affecting the conversion of urea to ammonium salts, or ammonium salts to nitrate by soil bacteria, or altering immobilisation/mineralization of these compounds to increase overall recovery by plants.

Other delivery mechanisms may also be used for the application of the modifiers to the animal. These may include incorporating the modifiers in animal feed, via a water trough or other water supply system, or by other traditional delivery mechanisms such as drenches or injections.

Other embodiments of the delivery device may utilise an electronic device as powered by an electrochemical cell, to provide sufficient modifiers over the treatment period. Such devices may be inserted into an animal's body cavity and be removed following the treatment period.

While such devices could be inserted into an animal's bladder, these will likely require surgical removal and thus considerable time and labour. Delivery devices may also be located in the rumen of an animal, which may remain in-situ or may be excreted after a period of time.

Methods and compositions for the sustained release of active agents into the bladder have previously before been described, particularly in the treatment of bladder cancer in humans. It is anticipated that a skilled addressee would readily be able to adapt these methods for use in the present invention. For example, in some embodiments there may be provided a mechanism which can be anchored to a device for later retrieval after the treatment period.

Such a mechanism may be a collapsible slow release membrane balloon. The balloon can be inserted into the bladder through a urethral catheter when in a collapsed form. The balloon can then be injected or infused via the catheter with modifiers. Once the substances have been delivered to the bladder, the balloon can then be withdrawn in its collapsed form through the urethra.

The balloon may deliver the substances through for example, dissolution and therefore will collapse naturally. In other embodiments, the balloon may be punctured to collapse it before it is withdrawn through the urethra.

To enable accurate placement of the collapsible balloon within the bladder, the delivery device may be used to act as an anchor for the balloon component of the delivery device, or alternatively the balloon may effectively "float" in the bladder. One example of such a device is described by US 6,171 ,298. Other compositions are known in the art such as those described in US 6,524,608.

These compositions have a specific gravity lower than urine, and therefore when infused or inserted into the bladder effectively float, ensuring that they are not expelled along with the urine. Instead, the composition is slowly bio-eroded to provide the sustained release of drugs. It is anticipated that the use of nitrogen process modifiers will be most effective over a seasonal time period such as from mid-autumn to late-winter, an extended period of approximately three to four months. This is due to nitrogen being prone to loss by processes such as leaching and/or denitrification/nitrous oxide emission. As such it may be desirable to have a composition or delivery device that slowly releases modifiers over this time period.

However, this should not be seen as a limitation for in other embodiments the modifiers may be delivered over a shorter time period, with a number of treatments administered to the animal as required. According to another aspect of the invention there is provided the use of a treatment substance in the manufacture of a delivery device substantially as described above for delivering said treatment substance to an animal to directly or indirectly affect the conversion of nitrogen containing compounds in animal waste, once the waste is excreted from the animal.

There is provided a formulation for introduction to an animal to alter the composition of animal waste, wherein the formulation includes a treatment substance for directly or indirectly affecting the conversion of nitrogen containing compounds in animal waste, and material to ensure the conversion is affected once the animal waste is excreted from the animal.

The term "material" should be taken to mean any material which ensures that the conversion of the nitrogen containing compounds is affected once the animal waste is excreted from the animal and may include biodegradable and/or bio-erodeable matrices known in the art, such as lipid-based coatings, wax coatings, polymer matrices.

As material breaks down in the environment, the modifiers are released and slow or alter the conversion of nitrogen containing compounds in the soil.

The function of the treatment substance (modifier) includes slowing the rate of transformation of urea to nitrate, through the inhibition of ureases produced by bacteria in the soil, by slowing the nitrification of ammonium to nitrate, and enhancing the immobilisation of inorganic nitrogen into soil organic forms. Throughout the present specification reference to the term "effective amount", should be understood as meaning an amount of the nitrogen process modifier administered to the animal so that the nitrogen process modifier will reduce the conversion of nitrogen containing compounds in animal waste, once the animal waste is excreted. In an embodiment, the invention includes the step of calculating the effective amount according to a desired "excretion rate", being the amount of nitrogen process modifier that is to be excreted.

In an embodiment, the excretion rate may be calculated and/or determined according to characteristics of the land onto which the animal waste is to be excreted. For instance, the excretion rate may be higher when the land is of a coarse-textured free draining soil type, or may be exposed to high levels of rain fall. This higher excretion rate is to compensate for removal of the nitrogen process modifier(s) from the land onto which they are excreted which may occur via natural processes.

In an embodiment, the excretion rate may be referenced as a desired mass of nitrogen process modifier per area of land onto which the animal waste is excreted e.g. kilograms of nitrogen process modifier per hectare (kg/ha). This approach may be beneficial as it assists in implementing the method in such a way that the nitrogen process modifiers are excreted onto the land at a rate which will affect the conversion of nitrogen containing compounds. It also compensates for daily variations in volume of animal urine excreted and/or daily fluid intake variations. However, the foregoing should not be seen as limiting on the scope of the present invention. It is also envisaged that the excretion rate may be referenced in other ways such as a concentration in urine (g/L).

It should be understood that natural variations may occur in the amount of a nitrogen process modifier excreted in an amount of animal waste. Therefore, it should be understood that all of an animal's individual void incidents (such as urine patches) may not contain a nitrogen process modifier(s) at the desired excretion rate.

In light of the foregoing, in embodiments of the invention a dosage rate may be selected to ensure that a minimum proportion, alpha, of excreted waste exceeds the desired excretion rate. For instance, an alpha value of 90% may be selected. In these, the dosage rate is selected to ensure that 90% of all animal waste contains a nitrogen process modifier(s) at or above the desired excretion rate.

Accordingly, the excretion rate of the nitrogen process modifier may be referenced as being an amount of the modifier contained in a percentage of the animal's total waste. For instance, the excretion rate may be the average rate of nitrogen process modifier contained in at least 90% of the animals' urine patches produced in a given time.

In embodiments, the invention includes the step of calculating the excretion rate based on factors such as soil type, temperature, time of year, and rain fall or drainage parameters, and/or the area on which an animal may urinate over a time period such as daily. However, the foregoing should not be seen as limiting on the scope of the present invention. It is also envisaged that the excretion rate may be calculated by a combination of the above parameters, or including additional parameters. As a result, the foregoing should not be seen as limiting on the scope of the present invention.

In an embodiment of the invention, the excretion rate of the nitrogen process modifier DCD within a urine patch may be at least substantially seven kilograms per hectare (7 kg/ha).

In an embodiment, the excretion rate may be less than a maximum concentration of DCD, being the maximum concentration of DCD which provides a quantifiable effect on conversion of nitrogen containing compounds in animal waste. The maximum excretion rate may be determined according to parameters of the location in which the invention is to be used and therefore take into account local factors. In addition, the maximum excretion rate may take into account natural variations in concentration of DCD excreted. In an embodiment of the invention, the excretion rate of DCD within a urine patch may be less than substantially 30 kilograms per hectare (30 kg/ha). This may be particularly beneficial for reducing conversion of nitrogen containing compounds in areas having coarse and/or free draining soils, or which are exposed to significant rainfall.

Alternatively, the excretion rate of DCD within a urine patch may be less than or substantially 15 kilograms per hectare (15kg/ha), or more preferably the excretion rate of DCD within a urine patch may be substantially ten kilograms per hectare (10kg/ha) which should be sufficient to achieve an effective reduction in conversion of nitrogen containing compounds in animal waste in the majority of situations.

The inventors have identified that having an excretion rate for the nitrogen process modifier DCD in the range of substantially 7kg/ha to 10kg/ha may be particularly beneficial for certain situations. For instance, having an excretion rate of DCD of less than 7kg/ha may likely result in concentrations of the DCD less than that necessary to achieve an effective reduction in conversion of ammonium to nitrate in the majority of situations. That in turn, would mean that there is nil or little benefit through use of the present invention.

In addition, having an excretion rate in excess of substantially 10kg/ha may provide little to no discernable reduction in conversion of nitrogen containing compounds compared to an excretion rate of substantially 10kg/ha for the majority of situations. As a result, ensuring that the excretion rate does not exceed substantially 10kg/ha may assist to reduce wastage of DCD for the majority of land types in which inhibiting loss of nitrogen containing compounds may be beneficial. This range therefore would provide potentially the most efficient use of DCD.

However, the foregoing should not be seen as limiting on the scope of the invention. It is also envisaged that the excretion rate may fall outside of the ranges identified herein if circumstances dictate. For instance, an excretion rate of up to 30kg/ha may be useful where animal urine is to be excreted onto a coarse and free draining soil type.

The amount of nitrogen process modifier administered to an animal to achieve a desired excretion rate would vary according to a number of factors. For instance, the nitrogen process modifier DCD administered to cattle such as beef or dairy appears to be excreted in urine at approximately 61-81 % efficiency. That is, 61-81 % of the nitrogen process modifier DCD administered to cattle is excreted in the animal's urine.

The nitrogen process modifier DCD administered to sheep appears to be transferred to the animal's urine with a slightly higher efficiency of approximately 86%. As a result, the present invention may include the step of determining a dosage rate, being the amount of nitrogen process modifier that must be administered to an animal to achieve a desired excretion rate.

In an embodiment, the dosage rate may be calculated according to the formula: Dr= x A x 1000 ÷ (X x V) where E ^r =DCD excretion rate in a urine patch (kg/ha)

A = area of urine patches/animal/day (ha/day) D ^r = dosage rate (grams/animal/day) X = a reflection of the efficiency of excretion. For instance, X may be calculated as amount excreted in urine ÷ amount administered

V = adjustment for the variable rate across individual urine patches to ensure that a desired percentage of urine patches meet or exceed the desired dosage rate. For instance, in preferred embodiments, V is the ratio of the (1 -alpha) percentile to the mean of the distribution of DCD concentrations.

In embodiments, V is preferably 90%. However, alternative values for V may be selected, for instance according to a desired excretion rate and factors such as an animal's metabolism or chosen dosage regime (time). In addition, V may have other values such as being 80%, 95%, and/or 99%.

The area of urine patches and number of deposits an animal makes will vary according to a number of parameters. For instance, fluid intake can vary, different animals may move while urinating etc. The inventors believe that A will vary according to a distribution curve affected by various factors. Applying the dosage rate formula, to achieve a target excretion rate (E ^r ) of 10 kg/ha, and A of 0.00036 ha/day (12 urinations/animal/day x 0.3 m ² /urination x 0.0001 ha/m ² ) and X of 0.8, the dosage rate (D ^r ) is 4.5 g/animal/day

However, this represents the average E ^r value. This does not account for variations in the excretion rate, which the inventors understand will vary according to a Gamma Distribution.

Therefore the dosage rate may be increased to ensure that at least 90% of all urine patches contain DCD at or above the desired excretion rate. For example, the formula described herein may be adjusted to include the factor V, being a variable rate factor to ensure that a desired percentage of all urine patches are at or above the desired excretion rate. Research by the inventors indicated a value for V of substantially 0.3 can achieve 90% of urine patches containing DCD at or above the desired excretion rate in dairy cows. The value of V may vary according to factors such as animal metabolism, dosage profile (amount DCD per dose and doses per day), water intake, number of urine patches per day etc. Accordingly, the discussion of a specific value for V should not be seen as limiting on the scope of the present invention.

The value of V can be calculated from data on an animal's urine and DCD concentration therein. For instance, a population of animals may be administered DCD at different rates. The concentration of DCD in the animals' urine patches can be measured and a distribution curve developed indicating the frequency of concentration in a urine patch. From this information, the probability of a given urine patch exceeding the DCD excretion rate can be determined. The inventors have found that to ensure that 90% of urine patches have an excretion rate of more than 7 kg/ha DCD requires a dosage rate of substantially 10 g/animal/day.

In embodiments the dosage rate may be:

• Between 10-45 grams of DCD per animal per day (g/animal/day) for cattle (cows), and preferably substantially at least 10 g/animal/day. · Between 2 - 5 grams DCD per animal per day (g/animal/day) for sheep, and more preferably substantially at least 3 g/animal/day.

The inventors have identified that these dosage rates are likely to ensure that the DCD excretion rate in 90% of urine patches is between 7 kg/ha and 30 kg/ha, and more preferably 10 kg/ha. Accordingly, the dosage rates identified herein are likely to ensure that the nitrogen process modifiers are excreted onto land at a concentration that may be optimum for inhibiting conversion of nitrogen containing compounds. In contrast a rate of DCD of approximately 5 kg/ha may be relatively ineffective. Likewise, it is suggested that application of DCD to land (in most soils and rainfall below about 500 mm/year) at rates in excess of 10 kg/ha provides negligible improvements in preventing conversion of nitrogen containing compounds in animal waster as compared to an application rate of 10 kg/ha. As a result, the identified rates discussed herein provide a solution not provided by the excretion rates outside of the nominated ranges. In an embodiment, the invention may involve administering the nitrogen process modifier(s) to an animal at a first dosage rate for a period of time and subsequently administering it to the animal for a second period of time These will be referred top as the first dosage rate and the second dosage rate.

The first dosage rate and the second dosage rate are preferably different to each other, with the first dosage rate being higher than the second dosage rate.

In embodiments, the first dosage rate is administered during a period immediately prior to, or at the beginning of, a period when conversion and/or degradation of nitrogen containing compounds is likely to occur in soil. For instance, the first dosage rate (which is higher than the second dosage rate) may be administered during may be administered to the animal during the period of early autumn to late autumn. Subsequently, the nitrogen process modifier may be administered to the animal at the second dosage rate.

This approach may be beneficial in ensuring a sufficient amount of the inhibitor is present in excreted urine and is likely to persist in the soil after excretion of the urine, and is available to reduce or prevent conversion of nitrogen containing compounds throughout the main period of risk of nitrogen loss. Inhibiting or modifying the conversion of nitrogen containing compounds allows more time for the nitrogen excreted in animal waste to be absorbed by plants, before being lost by soil processes such as leaching from the soil as nitrate. This will not only improve plant recovery of urine nitrogen, but also reduce the level of nitrates entering

groundwater and affecting both water quality and drinking water supplies.

It will also likely reduce the levels of nitrous oxide released to the environment and thus reducing levels of greenhouse gases emitted from intensive farming operations.

Having a delivery device which bio-erodes in the bladder allows only a certain amount of modifier to be released at any one time, dependent on the volume of urine excreted by the animal and as such reduces the wastage of modifiers.

Embodiments of the invention encompass a range of different mechanisms by which nitrogen process modifiers could be administered to animals to achieve their

incorporation and excretion in excreted waste, particularly urine.

Further advantages from this approach include; 1. Targeting the major source of nitrogen loss from pastoral systems (i.e. urine- nitrogen), thereby reducing the amounts needed relative to that for broadcast application over the whole land area

2. Intimate mixing in urine on deposition to soil. This ensures better contact with the urine and more effective modification of nitrogen processes. 3. Most effective timing of deposition, with return in the urine as it is excreted.

Additionally, the period of administration to animals can be targeted for greatest reduction in nitrogen losses e.g. from mid-autumn to mid- or late-winter for decreased nitrate leaching. 4. Ability to be administered by the farmer/manager rather than needing a contractor.

5. Potential for a single administration using a slow-release mechanism (e.g. rumen bolus) to achieve effective modification of nitrogen processes over the period of greatest risk of nitrogen losses.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 is a flow chart showing steps in a representative method according to the present invention;

Figures 2A is a plot of Frequency (% of urine patches) versus DCD concentration in a urine patch (kg/ha) for dairy heifers administered DCD at a rate of 12 g DCD per day; Figures 2B is a plot of Frequency (% of urine patches) versus DCD concentration in a urine patch (kg/ha) for dairy heifers administered DCD at a rate of 24 g DCD per day;

Figures 2c is a plot of Frequency (% of urine patches) versus DCD concentration in a urine patch (kg/ha) for dairy heifers administered DCD at a rate of 36 g DCD per day; DETAILED DESCRIPTION OF THE INVENTION

Representative delivery device

One embodiment of a delivery device according to the invention consists of a bolus administered orally to grazing animals with targeted delivery to the animal waste, and urine in particular. In embodiments the bolus is in the form of a slow release bolus which is inserted into the rumen and which releases nitrogen transformation modifiers over a sustained period of up to four months. The bolus may additionally include a rumen- stable delivery system to deliver the modifiers post-ruminally.

A generic composition of the bolus is as follows, i) a core comprising a substantially homogeneous mixture of: a) a water insoluble physiologically acceptable binder comprising wax, fat, oil, fatty acid, fatty acid ester, fatty acid amide, fatty acid alcohol or the like organic compound having a melting point above 50°C; b) a physiologically acceptable solubilising agent, such as polyethylene glycol stearate or the sodium salt of a long-chain fatty acid, c) at least one nitrogen transformation modifier, d) where required, a physiologically acceptable inert densifier of sufficient density and in sufficient quantities to give the bolus a minimum density of 1.5g/cm ³ ; and ii) a coating of a physiologically acceptable material over substantially all of the surface of the core but leaving exposed a core portion whereby in use liquid in the rumen will dissolve said core allowing release of the nitrogen transformation modifier into the rumen.

One embodiment of the bolus may include a nitrogen transformation modifier in the form of nitrification inhibitor such as DMPP or DCD up to 100g with a binding agent such as glycerol monostearate. The size of the bolus and the amount of modifier required will be dependent on a number of factors, including the identity and concentration of the inhibitor the body weight of the animal and the desired length of treatment. Such factors would be readily discernable to an addressee familiar with preparation of boluses and with direction to achieve the dosage and excretion rates (as are discussed below). In another embodiment of the invention the nitrogen process modifiers may be delivered from a slow release composition inserted into the bladder of animals. In these embodiments, a nitrogen inhibitor such as DMPP or DCD is incorporated with a minimal amount of a suitable carrier into a structure such as a flexible filamentous extrusion which is inserted into the bladder using a catheter. To retain the composition in the bladder, the composition has a specific gravity less than or equal to that of urine, which is normally about 1.005gm/ml to 1.033gm/ml at 25°C. This allows the delivery device to be neutrally buoyant or float in the urine of the bladder minimising the blockage of the urethra.

The composition could contain multiple constituents, a nitrification inhibitor such as DMPP, a urease inhibitor such as NBPT and/or an N-transformation modifier such as a tannin. Method of Use

Referring now to Figure 1 , which is a flow chart showing the steps in a representative method according to one aspect of the present invention. In general principles, the method administers internally to an animal an effective amount of a nitrogen process modifier such as DCD. The nitrogen process modifier is subsequently excreted by the animal in its waste onto land. The nitrogen process modifier is then able to affect the conversion of nitrogen containing compounds in the animal waste.

At step one, a nitrogen process or combination thereof is selected.

A desired excretion rate is then calculated. The excretion rate may vary according to various parameters such as:

1. Rain fall predicted for the land onto which animal waste is to be excreted.

2. Properties of the land such as soil type, porosity, an index reflecting drainage etc. At step two, a dosage rate is calculated according to the formula:

Dr=B x A x1000 ÷ (X x V) where

E ^r =DCD excretion rate in a urine patch (kg/ha) A = area of urine patches/animal/day (ha/day) D ^r = dosage rate (grams/animal/day)

X = a reflection of the efficiency of excretion. For instance, X may be calculated as amount excreted in urine ÷ amount administered V = adjustment for the variable rate across individual urine patches to ensure that a desired percentage of urine patches meet or exceed the desired dosage rate.

V may be determined based on data on DCD concentration in an animal's urine. For instance, Figures 2A- 2C each show the frequency of DCD concentrations in animal's urine for given dosage rates. The distributions can be used to determine a value for V which will ensure that a percentage of all urine patches contain DCD at a concentration above a desired excretion rate.

One method to determine V is to determine the distribution of the concentrations of DCD in urine. As in shown in Figures2 - 2C, a Gamma Distribution is fitted to the data. The 10 ^th percentile (where a 90% exceedance is required) is calculated and subsequently divided by the mean of the gamma distribution.

At step three, a treatment period may also be determined. The treatment period is the period of time that the nitrogen process modifiers are to be administered internally to the animal. The treatment period may be chosen so as to ensure that the nitrogen process modifiers are available to affect the conversion of nitrogen containing compounds in the animal waste during specific periods. For instance, nitrate leaching or nitrous oxide emissions are often highest during winter and early-spring. Therefore the treatment period for a nitrification inhibitor such as DCD to reduce these environmental losses would be between about mid-autumn and late-winter.

The treatment period may during the non-lactating period, or start of the drying off period, for a dairy animal such as a cow, sheep or goat. This may assist in ensuring that the animal's milk does not contain DCD residue which could make its way into the food chain. The treatment period may also include an end date, being the final date when DCD is to be administered to an animal. The end date may provide for sufficient time for DCD residues in the animal's milk to be eliminated (or at least below detectable or acceptable levels). This may be useful for reducing conversion of nitrogen containing compounds in waste from dairy animals.

At step four, the nitrogen process modifier is administered to the animal, such as using a delivery device, in a feed stock or via a water supply. For instance, silage, hay, or a processed feed pellet containing a nitrogen process modifier are feed to the animal. The feed stuff individually or collectively contains sufficient quantity of the nitrogen process modifier to achieve the dosage rate and therefore excretion rate calculated at step three.

The invention therefore also provides a feed stuff and/or water supply containing a nitrogen process modifier.

For cattle such as dairy or beef cows the dosage rate is in the range of 10-45 g/animal/day DCD, and preferably substantially at least 7 g/animal/day. For sheep the dosage rate is in the range of 2 to 5 g/animal/day DCD, and preferably substantially 3 g/animal/day.

The nitrogen process modifier passes through the animal and is excreted onto the land.

At step five the nitrogen process modifiers are able to affect the conversion of nitrogen containing compounds in the animal waste. No user action is required at this stage. Importantly, the dosage rates identified herein are sufficient to ensure that the nitrogen process modifiers are able to provide a useful reduction in the amount of losses of nitrogen from land. This is due to a desired number of urine patches containing sufficient quantities of the nitrogen process modifier to ensure that it is able to inhibit the nitrogen converting bacteria in a given area of soil. The process may be repeated so that nitrogen process modifiers are continuously administered to the animal over the treatment period.

In addition, the process may be repeated for multiple treatment periods, within a single multiple year period.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.