Monitoring ruminant emissions

Abstract

A system 100 for collecting emissions data for a group of ruminants 200 is provided. The system comprises a plurality of ruminant stalls 102 and a gas sensing apparatus 104. Each stall comprises a ruminant identification unit 112 and 5 a gas sampling output 120. The gas sensing apparatus comprises a sensor unit 124 comprising a gas sensor 126, a gas multiplexer 130, a pump 132 and a control unit 136 arranged to control the gas multiplexer based on information from the ruminant identification units so that the gas sensor measures gas concentrations in ruminant gas samples from every ruminant in the group.10 [Figure 1]

Description

[0001] 409.175065

[0002] Monitoring ruminant emissions

[0003] Technical Field

[0004] The present invention relates to systems and methods for monitoring gaseous emissions from a group of ruminants, such as cows.

[0005] Background

[0006] Ruminants such as cows belch frequently (e.g. every minute), releasing gases including methane. Methane is a harmful greenhouse gas and so it is desirable to monitor the levels of methane produced by this eructation process, e.g., to monitor the effectiveness of dietary or other interventions. It is also useful to be able to monitor other gases such as carbon dioxide.

[0007] Conventional approaches for measuring gaseous emissions from ruminants include sealing a ruminant within a respiration chamber and measuring gas concentrations in air flowing into and out of the chamber. Sealed hoods or ventilated masks can also be used in a similar way. However, all of these require some constraint or manipulation of the ruminant, which can be time consuming, labour intensive and uncomfortable for the animal.

[0008] Another approach is to integrate a gas sensor with an open station that entices animals to visit using a bait attractant. However, this approach typically produces only intermittent measurements and utilises relatively complex and costly equipment.

[0009] An improved approach may be desired.

[0010] Summary of the Invention

[0011] According to a first aspect of the present invention there is provided a system for collecting emissions data for a group of ruminants, the system comprising:

[0012] a plurality of ruminant stalls, wherein each stall is accessible to multiple ruminants of the group, and each stall comprises:

[0013] a ruminant identification unit arranged to identify a ruminant in the stall; anda gas sampling output from which a ruminant gas sample containing breath produced by a ruminant in the stall can be drawn;

[0014] a gas sensing apparatus comprising:

[0015] a sensor unit comprising a gas sensor arranged to measure a concentration of at least one gas in a gas sample;

[0016] a gas multiplexer comprising a plurality of inputs connected to the gas sampling outputs of the plurality of ruminant stalls and an output connected to the sensor unit, wherein the gas multiplexer is operable to connect one of the inputs to the output at a time;

[0017] a pump arranged to move a ruminant gas sample from a gas sampling output through the multiplexer to the sensor unit; and

[0018] a control unit arranged to control the gas multiplexer based on information from the ruminant identification units so that the gas sensor measures gas concentrations in ruminant gas samples from every ruminant in the group.

[0019] According to a second aspect of the present invention there is provided a method of collecting emissions data for a group of ruminants using a plurality of ruminant stalls, wherein each stall is accessible to multiple ruminants of the group and each stall comprises a gas sampling output, the method comprising:

[0020] a) identifying a ruminant in one of the stalls;

[0021] b) controlling a gas multiplexer to connect the gas sampling output of said one of the stalls to a sensor unit comprising a gas sensor;

[0022] c) moving a ruminant gas sample containing gas produced by said ruminant from said one of the stalls through the gas multiplexer to the sensor unit and measuring at least one gas concentration in the ruminant gas sample using the gas sensor; and

[0023] repeating steps a), b) and c) one or more times so as to measure gas concentrations in ruminant gas samples from every ruminant in the group.

[0024] Thus, it will be recognised by those skilled in the art that embodiments of the present invention can enable monitoring of ruminant emissions from a whole group of ruminants using only a single gas sensor, because the gas multiplexer can direct gas samples from each stall to the sensor unit required. This can reduce the cost and complexity of installing and maintaining the system.Moreover, ruminants regularly encounter stalls as part of a normal daily routine, e.g. feeding stalls, milking parlour stalls or milking robots. Thus because the gas sampling equipment is integrated with ruminant stall, it may be used to collect substantial volumes of emission data without needing to change the ruminants’ normal routine, e.g. to bring them to a dedicated sealed respiration chamber.

[0025] Thus, the present invention may enable thorough monitoring of the ruminants’ emissions, e.g. enabling detailed comparisons between emissions by different animals and / or at different times, without disrupting normal ruminant behaviour or requiring substantial additional labour.

[0026] Because each stall is accessible to multiple ruminants of the group, simply controlling the gas multiplexer to connect different stalls to the sensor unit (e.g. periodically) will not necessarily result in the measurement of samples from different ruminants with useful regularity. Although such an approach will eventually result in the collection of measurements from different ruminants, the random nature of the measurement timings cannot provide sufficient certainty for meaningful monitoring of the whole group of ruminants.

[0027] Therefore, the control unit controls the gas multiplexer based on information from the ruminant identification units, enabling much greater control over when emissions from different ruminants are measured.

[0028] To build up a useful collection of emissions data for each ruminant in the group, it may be desirable to regularly collect emissions data from each ruminant. In a set of embodiments, the control unit is arranged to control the gas multiplexer so that the sensor unit measures gas concentrations in ruminant gas samples from every ruminant in the group at at least a minimum target frequency (e.g. at least once every day, every 12 hours, every six hours, or every three hours), or for a minimum target duration (e.g. 5 minutes, 10 minutes, 20 minutes, 30 minutes) over a collection time window (e.g. three hours, six hours, twelve hours, one day).

[0029] Collecting emissions data with a desired regularity may require the control unit to decide which of several occupied stalls the sensor unit should be connected to, i.e. from which ruminant should the collection of emissions data be prioritised. Thecontrol unit may be arranged to control the gas multiplexer using a prioritisation algorithm that takes into account a time of a previous measurement for each ruminant and / or a duration of previous measurements for each ruminant (e.g. in total or over a given window such as a day). When the ruminant group size is small (e.g. less than ten animals), it may be relatively straightforward to obtain data with the desired regularity using relatively simple prioritisation algorithm. For instance, the control unit may be arranged to control the gas multiplexer so that the sensor unit measures a gas concentration for the ruminant having the oldest previous measurement or the least previous measurements. In some such embodiments, if a ruminant identification unit indicates that the currently-active stall (i.e. the stall to which the gas multiplexer currently connects the sensor unit) contains a ruminant whose emissions have been measured quite recently, and another stall contains a different ruminant whose emissions have not been measured for a long time, the control unit can change the active stall to measure emissions from the different ruminant.

[0030] However, in some cases, a more complex prioritisation algorithm may be used. In a set of embodiments, the control unit is arranged to determine a priority level of each ruminant in the group and to control the gas multiplexer based on said priority level (i.e. to prioritise collecting data for those ruminants with higher priority levels). The priority levels may be set according to the relative quantities of measurements collected for each ruminant (e.g. ruminants for whom measurements have been collected for a shorter duration have a higher priority for new collections than other ruminants).

[0031] In a set of embodiments, a ruminant may be classified as a high priority ruminant if a duration of previous measurements for said ruminant (e.g. in total or within a current collection window) is within a first quantile for the group of ruminants (e.g. the 5%, 10%, 15%, 20% or 25% of ruminants with the shortest collection of measurements). In some embodiments, the control unit may be arranged such that, in response to a ruminant identification unit identifying a high priority ruminant in a stall, the gas multiplexer is controlled to immediately connect the gas sampling output of said stall to the sensor unit. Changing the active stall immediately may interrupt a current measurement of another stall, but this potential loss of data may be acceptable to support the collection of emissions data for the high priorityruminant. However, in some embodiments, the control unit may be arranged to interrupt immediately only measurements of lower priority ruminants (e.g. medium or low priority ruminants) in response to detecting a high priority ruminant.

[0032] In a set of embodiments, a ruminant may be classified as a medium priority ruminant if a duration of previous measurements for said ruminant is within a second quantile for the group of ruminants (e.g. the 10%, 20%, 30%, 40% or 50% of ruminants with the shortest collection of measurements but who are not in the first quantile). In some embodiments, the control unit may be arranged such that, in response to a ruminant identification unit identifying a medium priority ruminant in a stall, the gas multiplexer is controlled to connect the gas sampling output of said stall to the sensor unit. This change of active stall may not happen immediately, but instead may be controlled to occur after a current measurement in another stall has been completed.

[0033] In a set of embodiments, a ruminant may be classified as a low priority ruminant if a duration of previous measurements for said ruminant is within an upper quantile (e.g. percentile) for the group of ruminants (e.g. in the highest 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%). The control unit may be arranged such that, in response to a ruminant identification unit identifying a low priority ruminant in a stall, the gas multiplexer is controlled to connect the gas sampling output of said stall to the sensor unit once all higher priority measurements have been completed.

[0034] The control unit may be arranged such that, if multiple ruminants of the same priority level are detected by the ruminant identification units (e.g. high priority, medium priority or low priority), the gas multiplexer is controlled to connect to the sensor unit the gas sampling output of a stall containing the ruminant that was earliest to arrive.

[0035] The sensor unit may itself record the measurements for different ruminants and / or the sensor unit may provide the data to a different device. In a set of embodiments, the system comprises a logging device arranged to store emissions data for different ruminants. The logging device may be comprised by the control unit.Each ruminant stall may be accessible to all ruminants of the group. For instance, all stall may be open and located in a common area that can be accessed by all ruminants of the group. However, in some embodiments, not all of the stalls may be accessible by all ruminants of the group. This may be achieved by physically separating the stalls between two or more areas accessible to different parts of the group of ruminants, and / or by controlling access to individual stalls. In a set of embodiments, at least one of the stalls comprises a gate that is operable to grant or deny access to a ruminant based on information from the ruminant identification unit of said stall.

[0036] In a set of embodiments, one or more of the stalls comprises a feeding stall.

[0037] Ruminants typically spend long periods of time eating each day, and so using feeding stalls can facilitate the gathering of large quantities of emission measurements. A feeding stall may comprise a feeding manger from which the ruminant can eat when in the stall. In some such embodiments, the gas sampling output of a feeding stall may lead from the feeding manger.

[0038] A feeding manger may comprise any suitable manger known in the art perse. A feeding manger may comprise a trough part with an open top through which the ruminant accesses feed. A feeding manger may comprise a lid that partially covers the open top whilst leaving an open access hole though which a ruminant can access feed. The lid may cover at least 50% of the surface area of the top of the manger, at least 70% of the surface area or at least 90% of the surface area. A feeding manger (having a trough part or otherwise and featuring a lid or otherwise) may as a whole be enclosed over at least 70% of its external surface area, at least 80% of its external surface area, at least 90% of its external surface area or at least 95% of its external surface area. Enclosing the manger more completely may increase the accuracy of emissions measurements, e.g. because there is reduced loss / dilution of ruminant breath.

[0039] The feeding manger(s) may be arranged to hold any suitable feed known in the art perse, such as silage or roughage. The feeding manger(s) may be arranged to hold at least 20 kg of feed, at least 50 kg of feed or at least 200 kg of feed. The feeding mangers may have a volume of at least 0.1 m3, at least 0.2 m3or at least 0.3 m3.In a set of embodiments, one or more (e.g. all) of the feeding stalls comprises a feed intake measurement device. The feed intake measurement device may comprise a weighing device arranged to weigh the feeding manger. The feed intake measurement device may be arranged to use weight measurements from the weighing device to determine feed intake by ruminants. Feed intake information may be combined with the information from a corresponding ruminant identification unit to enable the feed intake of specific ruminants to be monitored. This may be usefully analysed alongside the emissions data.

[0040] In a set of embodiments, one or more of the stalls comprises a milking stall (e.g. of a milking parlour). In a set of embodiments, additionally or alternatively one or more of the stalls comprises a milking robot.

[0041] In a set of embodiments, one or more (e.g. all) of the stalls comprises a fan arranged to extract air from the stall. The fan may extract air through an exhaust pipe (e.g. in a wall of the stall or part of the stall such as a feeding manger). The fan may be arranged to generate a negative pressure environment within the stall or within part of the stall (e.g. a feeding manger), mitigating losses of ruminant breath that could lower measurement accuracy. In such embodiments, the gas sampling output may be located adjacent an exhaust path of the fan (e.g. adjacent an exhaust pipe) or extend from an exhaust path of the fan (e.g. comprising an opening in an exhaust pipe).

[0042] In a set of embodiments, the fan may be arranged to maintain a constant extraction airflow from the stall or the part of the stall. Alternatively, the fan may be arranged to maintain a constant pressure difference between the interior and exterior of the stall or the part of the stall.

[0043] In a set of embodiments, one or more (e.g. all) of the ruminant identification units comprises a radio-frequency identification (RFID) reader device. An RFID reader device may be operable to identify a ruminant by reading an RFID chip carried by the ruminant (e.g. embedded in an ear tag or a collar). Additionally or alternatively, one or more ruminant identification units may utilise other identification technology.For instance, one or more ruminant identification units may comprise an imaging device operable to identify a ruminant by image-recognition distinguishing features in an image, or a machine-readable code reader arranged to identify a ruminant by reading a code carried by the ruminant (e.g. on an ear tag or collar).

[0044] As explained above, embodiments of the present invention can facilitate the gathering of emissions data from a group of ruminants using a plurality of stalls which share a common gas sensing apparatus. In a set of embodiments, the system comprises at least five stalls, at least seven stalls or at least ten stalls. In a set of embodiments, the system may be suitable for collecting emissions from a group containing ten ruminants or more, twenty ruminants or more or forty ruminants or more.

[0045] When measurements are being taken by the sensor unit, gas from the gas sampling output may be moved continuously to the sensor unit, i.e. a series of successive ruminant gas samples may be moved to the sensor unit. The sensor unit may collect numerous concentration measurements during this process. A single concentration measurement (i.e. producing a single concentration data point) may comprise an average of sensor readings across a measurement duration (e.g. two seconds, five seconds or fifteen seconds). As explained above, in some situations when a high priority ruminant is detected, a measurement may be interrupted (e.g. before this measurement duration is complete). The sensor unit may delay the start of measuring for (or discard readings taken in) a flushing time (e.g. 10 seconds, 20 seconds or 1 minute) after the sensor unit is connected to the relevant stall. This may ensure that gas samples from previous measurements have left the system.

[0046] In a set of embodiments, the gas sensor comprises a non-dispersive infrared detection (NDIR) sensor.

[0047] The gas sensor may be arranged to measure a methane concentration in a gas sample, i.e. the gas sensor may comprise a methane sensor. The gas sensor may be arranged to measure a carbon dioxide concentration in a gas sample, i.e. the gas sensor may comprise a carbon dioxide sensor.The emissions data collected by the system may consist of measurements of only one gas (e.g. methane). However, in some embodiments, it may be useful to monitor multiple gases in ruminant emissions (e.g. methane and CO2).

[0048] In a set of embodiments, the gas sensor may be arranged to measure the concentrations of several different gases in the same sample (e.g. methane and CO2). For instance, the gas sensor may comprise a tunable IR sensor that can be tuned to scan for a wide variety of gases in the same sample.

[0049] Additionally or alternatively, in a set of embodiments, the sensor unit comprises a plurality of gas sensors arranged to measure concentrations of a corresponding plurality of gases in a ruminant gas sample. For instance, the sensor unit may comprise a methane sensor and a (separate) CO2 sensor.

[0050] Said gas sensors may operate simultaneously (i.e. taking readings of the same samples).

[0051] The gas multiplexer may comprise any suitable gas control hardware known in the art perse. In a set of embodiments, the gas multiplexer comprises one or more electrovalves (e.g. solenoid valves).

[0052] The system may comprise one or more filters to filter the ruminant gas samples before they are measured by the sensor unit. For instance, the system may comprise one or more anti-condensation filters, small paper filters or microparticle filters. One or more filters may be provided for each stall (e.g. adjacent or near to the gas sampling outputs), and / or one or more filters may be provided for the sensor unit itself.

[0053] Because only one gas sensing apparatus is shared between the plurality of stalls, it may have parts which are physically distant from one or more of the stalls. The gas sampling outputs of one or more stalls may be connected to the gas multiplexer by flexible or rigid tubing.

[0054] In a set of embodiments, the gas sensing apparatus comprises a heating subsystem arranged to heat gas samples moving from the gas sampling outputthrough the multiplexer to the sensor unit. This may mitigate the occurrence of water condensation at low temperatures. The heating subsystem may comprise one or more heaters, e.g. arranged to provide heat to tubing connecting the gas sampling outputs to the gas multiplexer. The gas sensing apparatus may comprise one or more temperature and / or humidity sensors arranged to sense a temperature and / or humidity of a gas sample and / or an ambient environment. The gas sensing apparatus may be arranged to control the heating subsystem based on said temperature and / or humidity.

[0055] The applicant has recognised that effective emissions monitoring of ruminants may be achieved using only small samples of the ruminant’s breath. The gas sampling output may support a relatively small amount of airflow from the stall. For instance, in embodiments featuring a fan that extracts air from the stall or part of the stall, only a small portion of this extracted air may be diverted through the gas sampling output for sensing. One or more (e.g. all) of the gas sampling outputs may comprise an aperture with a diameter of 3 cm or less, 2 cm or less or 1 cm or less (e.g. approximately 6 mm). The gas sampling output may extend from a side wall, a bottom wall or a top wall (e.g. a lid) of the stall or part of the stall (e.g. a feeding manger). Taking a relatively small fraction of gas to the sensor unit though a small sampling output may allow the use of a less powerful pump, smaller tubing and / or smaller filters. For instance, in a set of embodiments, the gas sampling output of one or more stalls is connected to the gas multiplexer by tubing having an inner diameter of 3 cm or less, 2 cm or less or 1 cm or less (e.g. approximately 6 mm).

[0056] The pump may be arranged to move the gas ruminant gas sample from the gas sampling output through the multiplexer to the sensor unit by any mixture of drawing (pulling) and pushing gas - i.e. the pump may be located at any suitable location within the gas sensing apparatus. The pump may comprise an air diaphragm pump. The pump may have a pumping capacity of less than 20 litres / minute, less than 10 litres / minute or less than 5 litres / minute.

[0057] In a set of embodiments, the gas sensing apparatus is arranged to collect one or more background gas concentration measurements (e.g. of methane or CO2). In relevant embodiments, the gas sensing apparatus may be arranged to collect background measurements of a plurality of gases (e.g. methane and carbondioxide). Background measurements may be useful for analysing the ruminant emissions data (e.g. determining a ruminant contribution to a gas concentration in ruminant gas samples). In a set of embodiments, the emissions data collected by the control unit is corrected using one or more background measurements.

[0058] Collecting background concentration measurements of one or more gases may comprise controlling the gas multiplexer to connect the sensor unit to a background sampling location, using the pump to move a background gas sample from said sampling location through the multiplexer to the sensor unit; and the sensor unit measuring a gas concentration (e.g. of methane, CO2 and / or one or more other gases) for the background gas sample. The background sampling location may comprise the gas sampling output of a vacant stalls, or a background gas sampling location that is separate to the stalls.

[0059] In a set of embodiments, the gas sensing apparatus is arranged to perform a calibration process. The calibration process may comprise a zero-point calibration, in which the gas multiplexer is controlled to connect the sensor unit to a supply of inert gas (e.g. nitrogen) to allow the sensor unit to establish an accurate zero-point of a target gas (e.g. methane or carbon dioxide). Additionally or alternatively, the calibration process may comprise a target gas calibration process in which the gas multiplexer is controlled to connect the sensor unit to a supply of one or more target gases at a known concentration to calibrate the gas sensor of the sensor unit. The gas sensing apparatus may accordingly comprise a supply of an inert gas and / or a supply of one or more target gases (e.g. methane and / or carbon dioxide).

[0060] Embodiments of the present invention may be operable for monitoring the emissions of all types of ruminant including cows, sheep or goats.

[0061] Features of any aspect or embodiment described herein may, wherever appropriate, be applied to any other aspect or embodiment described herein.

[0062] Where reference is made to different embodiments, it should be understood that these are not necessarily distinct but may overlap.

[0063] Brief Description of the DrawingsOne or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

[0064] Figure 1 is a schematic diagram of system for collecting emissions data for a group of ruminants according to an example of the present invention;

[0065] Figure 2 is a schematic diagram of a feeding station of the system; and Figure 3 is a flow diagram illustrating a prioritisation algorithm that may be used by embodiments of the present invention.

[0066] Detailed Description of the Drawings

[0067] Figure 1 shows a system 100 for monitoring emissions from a group of ruminants such as cows. The system 100 comprises a plurality of ruminant feeding stalls 102 and a gas sensing apparatus 104. Figure 1 shows five ruminant feeding stalls 102, but in other examples there may be more or fewer feeding stalls 102. In other examples, other types of stall may be used in addition or alternatively to feeding stalls (e.g. milking robots or milking stalls in a milking parlour).

[0068] One of the feeding stations 102 is shown in more detail in Figure 2. It comprises a feeding manger 106, a ruminant identification unit 108, a fan 110, a feed intake measurement device 112 and a gate 114.

[0069] The feeding manger 106 has a trough part for holding feed and a lid 116 that covers and thus partially encloses the trough part, leaving only a relatively small access hole 118 through which a ruminant 200 can access the feed.

[0070] The ruminant identification unit 108 is an RFID reader, that detects and reads an RFID chip 202 carried by the ruminant 200 (e.g. contained in an ear tag or a neck transponder) to identify the ruminant 200 as it approaches the feeding station 102.

[0071] The feed intake measurement device 112 weighs the manger 106 to monitor how much feed has been eaten by the ruminant 200. This information can be combined with the identity of the ruminant 200 determined by the ruminant identification unit 108 to monitor individual ruminant feed intake over time.

[0072] The fan 110 extracts air from the manger 106 through an exhaust pipe. The exhaust pipe features a gas sampling output 120 from which a gas sample can bedrawn. The gas sampling output 120 is connected to tubing 122 that leads to the gas sensing apparatus 104 as shown in Figure 1, optionally via one or more filters (not shown).

[0073] The gas sensing apparatus 104 comprises a gas sensor unit 124 comprising a methane sensor 126 and a carbon dioxide sensor 128. The sensors 126, 128 may comprise non-dispersive infrared detection (NDIR) sensors, although this is not essential. In some examples, a single tunable NDIR sensor may be used to measure methane and carbon dioxide. The gas sensing apparatus 104 also comprises a gas multiplexer 130, a pump 132, a calibration unit 134 and a control unit 136.

[0074] The gas multiplexer 130 has a plurality of inputs and one output. Each gas sampling output 120 is connected to a respective input of the gas multiplexer 130 via the tubing 122. The calibration unit 134 comprises a supply of nitrogen, a supply of methane and a supply of CO2. The gas supplies may comprise pressurised tanks. Each supply is connected to a respective input of the gas multiplexer 130. The output of the gas multiplexer 130 is connected to the gas sensor unit 124 via the pump 132.

[0075] The gas multiplexer 130 is operable to connect one of its inputs to the output at a time. The gas multiplexer 130 is controlled by the control unit 136. Depending on the setting of the gas multiplexer 130, the pump 132 moves gas from one of the gas sampling outputs 120 or the calibration unit 134, through the gas multiplexer 130 to the sensor unit 124. The pump 132 is located between the multiplexer 130 and the sensor unit 124 and so it will be recognised that in this example the pump 132 draws gas from the sampling output 120 or the calibration unit 134 through the gas multiplexer 130 and then pushes said gas to the sensor unit 124. In other examples the pump 132 may be positioned differently within the system whilst still achieving the same overall movement of gas.

[0076] The operation of the system 100 to monitor the emissions of a group of ruminants will now be described with additional reference to the flow diagram of Figure 3.Each feeding station 102 of the system is physically accessible to all of the ruminants of the group. Over the course of a typical day, each of the ruminants 200 will visit at least one feeding station 102 to eat feed such as silage from the mangers 106.

[0077] When a ruminant 200 approaches a feeding station 102, the identification unit 108 identifies the ruminant from information stored on the RFID chip 202. In some examples, the identification unit 108 may be used in conjunction with the gate 114 to restrict access to the manger 106 to only certain ruminants 200 of the group.

[0078] The identification units 108 send this identification information to the control unit 136. Thus, at any given time the control unit 136 has information on which feeding stations 102 are in use and by which ruminants.

[0079] Once the ruminant 200 has entered the feeding station 102, it places its head into the manger 106 and begins to eat. As the ruminant 200 eats, it will continuously belch, producing gaseous emissions.

[0080] The fan 110 draws air out of the partially-enclosed manger 106 at a fixed rate. This produces a negative-pressure environment within the manger 106 which ensures that the gaseous emissions from the ruminant’s eruptions do not escape back through the hole 118.

[0081] To obtain measurements of methane and carbon dioxide emissions from a ruminant 200 as it eats, the control unit 136 controls the gas multiplexer 130 to connect the feeding manger 106 to the sensor unit 124. The pump 132 draws a ruminant gas sample, which contains the gas from the ruminant’s breath, from the gas sampling output 120 through the gas multiplexer 130 to the sensor unit 124. The sensor unit 124 measures the concentration of methane and carbon dioxide in the gas sample and outputs this to the control unit 136 where it is recorded.

[0082] This arrangement enables emissions data from one ruminant 200 to be collected at a time. To collect emissions data for the whole group, the gas multiplexer 130 is controlled to change the feeding station 102 whose emissions are being monitored in response to information from the identification unit 108. Because ruminants 200typically spend several hours per day at a feeding station 102, a single sensor unit 124 can be used to collect emissions data for all ruminants 200 with reasonably high regularity.

[0083] To ensure that the emissions data is collected relatively evenly across the group of ruminants 200, the control unit 136 selects which feeding manger 106 to connect to the sensor unit 124 (i.e. which ruminant 200 to monitor the emissions of) at any given time according to a ruminant prioritisation algorithm that is illustrated in Figure 3.

[0084] The prioritisation algorithm begins in step 300 by identifying (using data from the identification units 108) any ruminants 200 that are currently in feeding stations 102. These may be newly-arrived ruminants 200 or ruminants 200 that have been in the feeding station 102 for some time.

[0085] In step 302, the control unit 136 determines whether all feeding stations 102 are currently vacant (i.e. if there are no ruminants 200 currently feeding). If this is the case, in step 304 the control unit 136 may control the system 100 to take background readings. This may comprise controlling the gas multiplexer 130 to connect the sensor unit 124 to a gas sampling output 120 of a vacant feeding station 102, using the pump 132 to draw a gas sample from this station 102 and using the sensor unit 124 to measure background methane and carbon dioxide concentrations in the gas sample. In some examples, general background readings may be taken by controlling the gas multiplexer 130 and pump 132 to draw a gas sample to the sensor unit 124 from a separate background gas sampling location (not shown).

[0086] Additionally or alternatively, in step 304 the system 100 may perform a calibration process using the calibration unit 134 to mitigate measurement errors in future readings.

[0087] The calibration process may comprise a zero-point calibration, in which the gas multiplexer 130 is controlled to connect the sensor unit 124 to the nitrogen supply of the calibration unit 134. The pump 132 draws pure nitrogen to the sensor unit 124 and allows the sensor unit 124 to establish an accurate zero-point of methane andcarbon dioxide. Additionally or alternatively, the calibration process may comprise a methane and / or carbon dioxide calibration process in which the gas multiplexer 130 and pump 132 are controlled to draw a gas sample that has a known level of methane and / or carbon dioxide, from the methane and / or carbon dioxide supplies of the calibration unit 134. This sample is then measured by the sensor unit 124 and the known level(s) used to calibrate the sensor unit 124.

[0088] It will be understood that background readings or one or both of these calibration processes may also or alternatively be performed at separate dedicated times (i.e. when the prioritisation algorithm is not running).

[0089] If not all of the feeding stations 102 are vacant, the control unit 136 determines in step 306 whether only one feeding station 102 is in use. If this is the case, in step 308, the control unit 136 controls the gas multiplexer 130 and pump 132 to draw gas samples from the feeding station 102 that is in use to the sensor unit 124. The control unit 136 identifies the ruminant in the active feeding station 102 using data from the identification unit 108. The sensor unit 124 measures methane and carbon dioxide concentration levels in the gas samples and the control unit 136 records these in logs for the relevant ruminant.

[0090] If more than one feeding station 102 is in use, the control unit 136 identifies using data from the identification unit 108 all of the ruminants 200 that are currently in feeding stations 102. In step 310, the control unit assesses whether any of these ruminants 200 are “high priority” ruminants. In this example, a high priority ruminant is one for which the total duration of emissions data that has been previously collected is within the lowest 10% of the group of ruminants (i.e. the high priority ruminants are the 10% of ruminants with the shortest total emissions duration).

[0091] If a high priority ruminant 200 is currently in feeding station 102 and its emissions are not currently being measured, the control unit 136 in step 312 controls the gas multiplexer 130 to immediately connect the gas sampling output of the feeding station 102 containing the high priority ruminant 200 to the sensor unit 124 and the pump 132 begins to draw gas samples for this ruminant 200 to the sensor unit 124. The sensor unit 124 measures methane and carbon dioxide concentration levels in the gas samples and the control unit 136 records these in logs for the relevantruminant. If multiple high priority ruminants 200 are identified in step 310, the high priority ruminant that arrived earliest at a feeding station 102 will be prioritised. As measurements are taken and recorded, a high priority ruminant 200 may transition to a lower priority ruminant 200.

[0092] If a high priority ruminant 200 is not present in any feeding station 102, the control unit 136 assesses in step 314 whether any of the ruminants 200 are “medium priority” ruminants. In this example, a medium priority ruminant is one for which the total duration of emissions data that has been previously collected is within the lowest 10-30% of the group of ruminants (i.e. the medium priority ruminants are the 30% of ruminants with the shortest total emissions duration which are not high priority ruminants). The remaining ruminants (i.e. the top 70%) are “low priority” ruminants.

[0093] If a medium priority ruminant 200 is currently in a feeding station 102 and its emissions are not currently being measured, the control unit 136 in step 316 waits until a current gas sample measurement is complete (e.g. from feeding station containing a lower priority ruminant) and then controls the gas multiplexer 130 to connect the gas sampling output of the feeding station 102 containing the medium priority ruminant 200 to the sensor unit 124. The pump 132 begins to draw gas samples for this ruminant 200 to the sensor unit 124. The sensor unit 124 measures methane and carbon dioxide concentration levels in the gas samples and the control unit 136 records these in logs for the relevant ruminant. If multiple medium priority ruminants 200 are identified in step 310, the medium priority ruminant that arrived earliest at a feeding station 102 will be prioritised. As measurements are taken and recorded, a medium priority ruminant 200 may transition to being a lower priority ruminant 200.

[0094] If no high or medium priority ruminants 200 are present in the feeding station 102 (i.e. only low priority ruminants are present), then in step 318 the control unit 136 controls the gas multiplexer 130 to connect the sensor unit 124 to the gas sampling output of the feeding station 102 containing the ruminant 200 that arrived earliest at a feeding station 102.The methane and carbon dioxide concentrations measured by the sensor unit 124 are used to produce a log of emissions for each ruminant.

[0095] The prioritisation algorithm shown in Figure 3 is repeated continuously by the control unit 136. As ruminants 200 arrive at and leave feeding stations, the algorithm results in different feeding stations 102 being connected to the sensor unit 124 according to the relative priorities of their occupants, ensuring that emissions data is collected with acceptable regularity for all ruminants in the group.

[0096] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

Claims1. A system for collecting emissions data for a group of ruminants, the system comprising:a plurality of ruminant stalls, wherein each stall is accessible to multiple ruminants of the group, and each stall comprises:a ruminant identification unit arranged to identify a ruminant in the stall; and a gas sampling output from which a ruminant gas sample containing breath produced by a ruminant in the stall can be drawn;a gas sensing apparatus comprising:a sensor unit comprising a gas sensor arranged to measure a concentration of at least one gas in a gas sample;a gas multiplexer comprising a plurality of inputs connected to the gas sampling outputs of the plurality of ruminant stalls and an output connected to the sensor unit, wherein the gas multiplexer is operable to connect one of the inputs to the output at a time;a pump arranged to move a ruminant gas sample from a gas sampling output through the multiplexer to the sensor unit; anda control unit arranged to control the gas multiplexer based on information from the ruminant identification units so that the gas sensor measures gas concentrations in ruminant gas samples from every ruminant in the group.

2. The system of claim 1, wherein the control unit is arranged to control the gas multiplexer using a prioritisation algorithm that takes into account a time of a previous measurement for each ruminant and / or a duration of previous measurements for each ruminant.

3. The system of claim 1 or 2, wherein the control unit is arranged to determine a priority level of each ruminant in the group and to control the gas multiplexer based on said priority level.

4. The system of any preceding claim, wherein one or more of the stalls comprises a feeding stall comprising a feeding manger from which the ruminant can eat when in the stall.

5. The system of claim 4, wherein the feeding manger is enclosed over at least 70% of its external surface area.

6. The system of claim 4 or 5, wherein the feeding stall comprises a feed intake measurement device.

7. The system of any preceding claim, wherein one or more of the stalls comprises a fan arranged to extract air from the stall.

8. The system of any preceding claim, wherein the gas sensor comprises a methane sensor and / or a carbon dioxide sensor.

9. The system of any preceding claim, wherein the gas sensing apparatus comprises a heating subsystem arranged to heat gas samples moving from the gas sampling output through the multiplexer to the sensor unit.

10. A method of collecting emissions data for a group of ruminants using a plurality of ruminant stalls, wherein each stall is accessible to multiple ruminants of the group and each stall comprises a gas sampling output, the method comprising:a) identifying a ruminant in one of the stalls;b) controlling a gas multiplexer to connect the gas sampling output of said one of the stalls to a sensor unit comprising a gas sensor;c) moving a ruminant gas sample containing gas produced by said ruminant from said one of the stalls through the gas multiplexer to the sensor unit and measuring at least one gas concentration in the ruminant gas sample using the gas sensor; andrepeating steps a), b) and c) one or more times so as to measure gas concentrations in ruminant gas samples from every ruminant in the group.

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