Greenfeed SOP

NOTE: This version of Section 20 has been approved by the working group's Chair. Please be aware that further revisions may occur before final review and approval by the Board and ICAR members per the Approval of Page Process.

Introduction

This document is the report obtained from the presentations, talks, chats and discussions of the Zoom meetings on 5^th December 2022 (Dairy) and 7^th December 2022 (Beef). In both meetings an introduction was made about the ICAR Feed&Gas Working Group, the objectives of the Working Group, including the revision of the guidelines (Section 20 - Recording Dairy Cattle Methane Emission for Genetic Evaluation) published two years ago. Moreover, the aim of the meeting was to share knowledge on GreenFeed operating procedure including tips, tricks and trouble-shooting data recording using the Greenfeed system. 50 to 60 people from 14 countries participated to both meetings.

Enteric methane (CH₄) production and carbon dioxide (CO₂) production can be measured non-invasively using a GreenFeed emission monitoring system (C-lock Inc. Rapid City, SD, USA). GreenFeed is an adapted feeding station that continuously measures both CH₄ and CO₂ concentration and the quantitative airflow in order to generate individual gaseous production. GreenFeed is equipped with a fan that pulls air from around the head of the cow with 30-40 L/s. The airflow is measured continuously by a hot-film anemometer that needs to be calibrated monthly. In the air collection pipe continuous subsamples are drawn to analyse the CH₄ and CO₂ concentration by nondispersive infrared sensors, which are automatically calibrated on a daily basis. Additionally, head positioning is registered by an infrared sensor. This sensor only determines the distance of the cow to the sensor, not what part of the cow causes this distance, could be the nose but also the ear for example. Temperature and radiofrequency identification tags specific to each cow for individual recognition are recorded as well. All variables are logged at a 1 s interval. GreenFeed measures continuously, even if there are no animals present, to correct for background emissions in the barn. The periods within a visit where the head position of the animal is correct are used for measuring gaseous emissions. Quantitative concentrations in g/d were calculated at a 1 s interval, which were then averaged per visit (minimum of 2 min).

Most of the information on this page refers to the ordinary version of the GreenFeed, most often used for dairy and beef cattle. There are two other versions, which are discussed separately, for small ruminants and for animals with large horns.

Equipment description

The correct placement of the GreenFeed unit inside the barn is crucial.

Indoor, it is advisable to place it on solid, non-slatted floor, in a location with good ventilation. Irregular ventilation or background emissions from manure may negatively affect the estimates of methane and carbon dioxide emissions.

Outdoor, the GreenFeed have to be located in a solid place (not in the mud), with a good phone (internet) connection and a good sunlight (if equipped with solar panel). The GreenFeed unit and the grazing site have to be nearby. The grazing area should not be so large as it could impact the number of visits. It may be appropriate to install an electric fence to protect the GreenFeed unit from animals’ damage, but also to avoid animals to enter by side of the GreenFeed; this was not always undertaken and warrants further investigation. A plastic and waterproof cover can be installed on the unit and a weather station on its top. Together with the GreenFeed, the trailer can also be purchased from C-Lock. This trailer is suitable for short distance moving and it is essential for placement in pasture (i.e. the trailer contains a spot where the unit can be attached, since it has to be standing solid to prevent it from getting damaged by cows, where the gas cylinders can stand and contain power supply (solar panel or batteries). If it is necessary to move the GreenFeed unit for longer distances it is essential to have a more solid trailer available and should be compatible with the legal requirements for road vehicles in the respective country.

All users agree that wooden side shieldings provided by C-Lock are not enough to contain the animal and to reduce the influence of other animals’ emissions. According to user experience to reduce influence of gaseous emissions from cows to the side, a good side shielding must be 0.80-0.90 m wide and adjustable, at least 2.5 m long, both indoor and outdoor.

Some advanced users have created a “L-port gate” (Picture 1) that closes behind the animal, so it cannot be pushed out of the unit by other cows. Cows that use this “L-port gate” are calmer (once they are used to it).

All users consider positive the ventilation noise of the GreenFeed fan. This ventilation noise is easily associated by the animals with the supply of feed, so the animals adapt more quickly.

As regards the feed to be used in GreenFeed, most users use a pellet feed with a diameter of less than 7 mm as suggested by C-Lock. Few users use feed blocks.

Picture 1. “L-port gate” on the GreenFeed alleyway of Wageningen Livestock Research at Research Facility De Marke.

Experimental protocols

The overall duration of the trial varies, from a minimum of 7 days up to a year, both indoor and outdoor, according to the purpose of the experimental trial. Feeding settings can vary dependent on the preferred feed gift and preferred number of measurements per day. There are two important principles that should be met: the time of a feeding period (and thus gaseous measurement) should be between 2 and 5 minutes (at least 2 minutes, preferably 3-4 minutes), and the number of visits per day should be between 2 and 8, and divided over the day. The number of cows that can visit multiplied by the number of visits per cow per day multiplied by the time per visit should never exceed 24 hours, but preferably not exceed 12 hours (which means occupation of the GreenFeed 50% of the time). In general, one GreenFeed is suitable to measure at maximum 40 to 50 cows and still get decent data. This also leaves the GreenFeed unoccupied for long enough to measure background concentrations, which are needed for calibration.

When more than 50 cows have tags that the GreenFeed can recognize, the system can be programmed to only drop feed for specifically selected cows. The other cows will lose interest and the cows you want to measure can use the GreenFeed enough to get useable data.

The wide variability of the experimental protocol variables can be summarized as follows for cows:

	INDOOR	OUTDOOR
DROP DISPENSE INTERVAL	10 - 60 seconds	10 - 30 seconds
MIN. TIME BETWEEN FEEDING PERIODS	7.200 - 21.600 seconds (2 - 6 hours)	3.600 - 14.400 seconds (1 - 4 hours)
MAX. DROPS PER FEEDING TIME	4 - 25	4 - 25
MAX. FEEDING PERIODS	4 - 12	4 - 12

For other species different protocols apply, below a few experimental protocols variables currently known:

DAFNE feeding protocols:

	Sheep	Buffalo
Number of drops per visit	8	8
Concentrates in gram per drop	7	37
Max amount of visits per day	3	5
Max amount of concentrates per day (g)	168	1480
Max amount of cup drops per day	24	40

Training and adaptation period

The overall duration of the training and adaptation period last from 7 to 20 days, both indoor and outdoor. Animals that are already used to feeding boxes in the barn are generally easier to train to use the GreenFeed. Because of that indoor adaptation is generally on the shorter end of this adaptation period. The outdoor animals are generally on the longer end of the adaptation period, as they are not used to being confined. For the outdoor GreenFeed it is suggested to keep the animals confined to a smaller lot with the GreenFeed, during adaptation, before being let out to the larger pasture, for faster adaptation.

For the entire adaptation period it is essential to locate the GreenFeed within the eyesight of the animals.

During training the “drop dispense interval” can be slightly adjusted, for example reduced to 10 seconds in first days of adaptation, then increased to 20 seconds and then it is possible to use the experimental protocol. Outdoor could be useful to provide a small amount of feed around the GreenFeed unit or near to the GreenFeed chute.

Using a camera installed on the top of the unit can be useful for training, so the user can drop feed when animals are near to the GreenFeed unit.

If using side shieldings, it is important to set the funnel at largest size and reduced regularly day by day up to the end of the training period and the start of the experimental trial.

In some cases, there might be animals that are more difficult to train. In this case it is good practice to guide them into the GreenFeed and evaluate their behaviour. If they are reluctant, it is advisable not to involve them in the experimental trial. Generally, 50% of the animals adapt autonomously, 25% of the animals need an intervention, and the remaining 25% are more reluctant. A good training and adaptation period provides for the success at least 70% of indoor animals and at least 50% of grazing animals.

Having non-users located beside users of machines has proven to be helpful when later training those non-users.

Spread concentrates in the chute or using salt licks may help entice animals to use the machine.

When based on grazing, it is important that the machine is moved to the edge of the fresh pasture once strip wire is moved – animals should not have to move far to reach the machine as this will impact number of visits.

Data analysis

GreenFeed devices produce a lot of data which can be very overwhelming to handle. In March 2025, a new technical note came out in JDS communications about a new open-source tool to simplify processing and data reporting from GreenFeed systems, making it easier to get flexible, useful, and impactful data. The package offers functions for downloading, processing, and reporting GreenFeed data and is freely available at the Comprehensive R Archive Network (CRAN; https://cran.r-project.org/web/packages/greenfeedr/) All functions of version 1.0.2 of the greenfeedr package are described in this article.

Problems faced and upgrades

Table reports all the problems faced including solution and possible home-made upgrades found by the several institutions.

PROBLEM	SOLUTION	SUGGESTIONS/UPGRADES
Feed clogging in the bin	Unclog the feed bin and try a more solid pellet. Prevent the feed bin from moist.	Extra molasses in feed pellet.
Motor problem	Replaced using C-Lock spare parts and assistance.
Airflow problems	Replaced using C-Lock spare parts and assistance.
Connectivity problem	Replaced using C-Lock spare parts and assistance.	In alternative, purchase an external Wi-Fi router or SIM-card router.
Power supply problem	Replaced using C-Lock spare parts and assistance.
Batteries under solar panel are getting low and smart solar controllers decide battery is too flat.	Moving from lead acid to lithium iron phosphate (LiFePO4) batteries has largely eliminated the problem. This is because LiFePO4 give a constant output voltage.	RFID identification problems
RFID identification problems	Caused by either low power supply (check and replace power supply if needed) or antenna problems (follow instructions from C-lock to find the cause and replace if needed).
Leaky CO2 cylinder and lower CO2 release	Replaced CO2 cylinder by C-Lock.	Make sure to never hold the CO2 tool upside down when attached to a CO2 cylinder.
Concentration sensor	Replaced using C-Lock spare parts and assistance.
Shipping time and shipping issues in some parts of the world (e.g., Europe and Oceania)		List of “must have spare parts” to create a personal warehouse. European or Oceanian dealer?
Feed bin brush chewed by a rodent	Tack on feed bin chute.	Internal component more sealed.

Despite the various problems encountered, all users consider the assistance provided by the C-Lock very good (video tutorials, operating instructions...). E-mail reply is quickly (few hours considering time zone).

It is recommended to keep spare parts in stock.

Small ruminants

The adapted GreenFeed for small ruminants has a lower flow, at 15L/min and thereby has a lower detection limit.

Protocol at INRAE for Meat Sheep

Below you find a protocol used at INRAE, France, for measuring methane emissions in meat sheep:

CH₄ and CO₂ emissions are recorded with two Sheep GreenFeed devices manufactured by the C-Lock company (US) (Rozier et al., 2021)  

One device is installed per pen of 30-40 individuals. A drop (small amount of concentrate) is delivered by the device in order to attract animals. To be valid, a visit of animal must last at least 2 minutes. To optimize the number of efficient visits and considering that we don’t want too much concentrate to be delivered by GreenFeed devices, we set the following parameters: a given day is divided in 4 periods of 6 hours each. During each period, each animal can get a maximum of 6 drops of concentrate, these drops being delivered with an interval of 30 seconds. Animals can visit the device even if they can’t get any drop, and if this visit lasts more than 2 minutes, GHG are recorded.

Similarly to the phenotyping of feed intake, animals are accustomed to the pen and the device during a minimum of 2 weeks, and the control lasts 6 weeks after the adaptation period. During this period of control, animals are fed as usual. Feed intakes can be recorded over the same period, but it must be reminded that the concentrate delivered by the Sheep GreenFeed devices to a given animal can be eaten by another one. This can bias daily feed intake calculation.

During the control period, animals are weighed on a weekly basis, mainly for the computation of different GHG traits.

With Sheep GreenFeed, raw data are not available: GHG emissions, expressed in gram per day can be downloaded from the C-Lock website, with one value per visit. For Sheep GreenFeed, animals may visit the device whenever they want, and several times a day. However, the production of methane is not constant over 24 hours. Therefore, GHG emissions have to be corrected for the moment of the visit. This moment can be either the hour of the day (24 levels) or the period (from 4 to 6 periods can be defined, depending on how often animals are fed during the day). Individual emission rates are obtained with a repeatability model:

CH₄ = µ + Pen + Day + Animal + Hour + Ɛ  

The animal emission rates are the animal LSMeans estimates from this model. Individual CO₂ estimates are obtained by applying the same repeatability model on CO₂.

Horned animals

The adapted GreenFeed for cattle and other ruminants with large horns is mostly used in Africa and for Bison.

Questions and answers

Q1. What’s the pasture size?

A1. Cows graze grass which is about 1.500 kg DM/ha, or 9 cm in height.

A2. Usually, 40 cows we allocate 0.48 ha for 24 hours.

Q2. How do you move your GreenFeed unit?

A1. We take chimneys off and load them into a truck.

A2. A trailer as the C-Lock one is fine for short moving between pastures.

Q3. How often do you change air filters?

A1. Once per week in more than enough (about 20 animals per GreenFeed unit)

A2. Every 3 days (more than 25 animals per GreenFeed unit)

A3. Every 14 days (less than 10 animals per GreenFeed Unit)

A4. When the airflow is below 27 L/s (advised by GreenFeed Email Alerts & Reminders)

Q4. Do you use C-Lock final data or preliminary data?

A1. Final data reviewed, corrected for calibrations and outliers by C-Lock.

A2. Final data. Between C-Lock final data and preliminary data there is a difference of about 5%.