C-Lock’s GreenFeed system, referenced in more than 800 peer-reviewed publications, is helping researchers move past simple intake numbers to measure the metabolic efficiency of individual cattle — the truest signal of how much feed actually becomes growth.
For nearly two decades, C-Lock Inc.’s GreenFeed system has set the scientific standard for measuring what individual cattle emit. Referenced in more than 800 peer-reviewed publications and validated against respiration chambers at correlations above 0.95, GreenFeed is trusted by researchers, producers, and sustainability leaders in 48 countries. Now that same measurement foundation is opening a more ambitious question, one that reaches past intake and toward biology itself: not simply how much an animal eats, but how efficiently its body turns that feed into growth. This is metabolic efficiency, and it may be the purest measure of animal performance available.
Why isn’t feed intake enough?
Feed accounts for up to 70% of the cost of raising livestock, so the industry has chased efficiency for decades. Traditional metrics, such as feed conversion ratio and residual feed intake, compare how much an animal eats against how much it grows. These are genuinely useful. Residual feed intake, in particular, has helped identify animals that consume less than expected for their size and level of production, and selecting for it has delivered real economic returns.
But intake-based metrics describe the outcome of efficiency without explaining its cause. They tell you an animal ate less than its peers, yet they cannot tell you why. Two animals can eat the same ration and gain the same weight, while one runs a far more economical metabolism underneath. One may lose more energy as heat, or as methane, or spend more of its intake simply maintaining itself rather than building product. Intake alone cannot separate these animals. To find the truly efficient animal, you have to look inside the engine, not just measure the fuel going in.
What is metabolic efficiency?
Metabolic efficiency describes how effectively an animal partitions the energy it consumes. Every mouthful of feed follows one of three paths. It is converted into product, such as muscle, milk, or body condition. It is spent on maintenance and given off as heat. Or it is lost entirely, and some of that loss leaves the animal as methane – feed energy that would otherwise support growth and instead escapes to the atmosphere as a greenhouse gas.
An animal that channels more of its feed energy into growth, and less into maintenance, heat, and methane, is metabolically efficient in the fullest sense of the word. The most efficient animal is therefore not the one that simply eats the least. It is the one whose body extracts and directs the most usable energy from every kilogram of feed. Measuring that balance directly, rather than inferring it from intake, is the goal, and it is what makes metabolic efficiency such a pure and powerful signal.
How do you measure metabolism without a chamber?
The challenge has always been access. How can you measure something as internal as metabolism without confining an animal in a sealed laboratory? The answer lies in the gases the animal exhales.
GreenFeed captures methane, carbon dioxide, oxygen, and hydrogen from individual animals during short, voluntary visits to a feeding station. Together, these gases form a metabolic stat sheet. Oxygen consumption and carbon dioxide production are the foundation of indirect calorimetry, the same principle laboratories use to estimate heat production and energy expenditure. The ratio between them, known as the respiratory quotient, indicates whether an animal is drawing its energy mainly from carbohydrates or from fat. Hydrogen reflects the dynamics of rumen fermentation — the microbial process at the heart of how a ruminant digests. Methane quantifies the feed energy lost to the atmosphere. Read together, these four gases reveal how an animal is actually processing its feed, moment by moment.
This is the breakthrough. GreenFeed brings calorimetry-grade gas measurement out of the sealed chamber and into the pasture and the parlour, where animals behave naturally and where efficiency actually matters. Because the animal is never restrained or removed from its environment, the measurement reflects real biology under real conditions.
Measuring the whole animal
Gases tell one side of the story. C-Lock’s advantage is measuring the entire equation on a single validated platform. While GreenFeed records what an animal emits and how its metabolism is working, C-Lock’s SmartLine products record the rest. SmartFeed measures exactly how much each animal eats, down to the individual level. SmartScale tracks weight and growth over time.
Streamed together into the SmartLine Dashboard, intake, gas exchange, and growth combine into one continuous, individual-animal picture. For the first time, producers and researchers can compare what an animal takes in, how its body processes that energy, and how much of it becomes product, all from the same source and all comparable across animals, studies, and geographies. That is the complete efficiency equation, measured rather than modelled.
Why the most metabolically efficient animals matter
Finding the most metabolically efficient animals carries compounding value. Within a herd, these animals produce more from less feed, lowering cost and shrinking environmental footprint at the same time. In breeding programmes, metabolic efficiency is a heritable target. Once it is selected for, the benefit sticks, generation after generation, a durable genetic advantage that feed additives and diet changes cannot deliver on their own. And because GreenFeed data is standardised and comparable, the same measurements support genetic evaluation, sustainability reporting, and peer-reviewed research with equal confidence.
The livestock sector is under growing pressure to produce more while emitting less. Simple intake numbers were never going to answer that challenge alone. By measuring the metabolic efficiency of individual animals, and by grounding that measurement in technology already referenced in more than 800 peer-reviewed studies, C-Lock is giving the industry its purest signal yet of what makes an animal truly efficient. The most efficient animal can finally be found, not by watching what it eats, but by measuring what its body does with it.
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