According to Gram Research analysis, high-efficiency lambs produced 15.2% less methane per kilogram of feed consumed compared to low-efficiency lambs in a study of 40 animals, though this difference wasn’t statistically significant. The research shows that feed efficiency and methane emissions may be related, but the connection is weaker than expected, and efficiency classifications can change as lambs grow older.
Researchers studied 40 lambs to see if some animals use their food more efficiently than others and whether this affects how much methane gas they produce. They divided the lambs into three groups based on how well they converted feed into body weight. While the most efficient lambs produced about 15% less methane per unit of food eaten, the differences weren’t large enough to be statistically significant. The study suggests that measuring feed efficiency in young animals may be tricky because results can change as the animals grow.
Key Statistics
A 2026 study of 40 Santa Inês lambs found that high-efficiency animals emitted 15.2% less methane per kilogram of dry matter intake compared to low-efficiency lambs, though the difference was not statistically significant.
Research published in Tropical Animal Health and Production showed no significant differences in ruminal fermentation parameters or stomach microorganism populations between feed-efficient and inefficient lambs fed the same diet.
A 2026 analysis of feed efficiency classifications in lambs revealed that residual feed intake and residual income growth measurements may not be consistent across different life stages, limiting their reliability for long-term breeding decisions.
The Quick Take
- What they studied: Whether lambs that use their food more efficiently produce less methane gas, and how their stomach fermentation differs from less efficient animals
- Who participated: Forty young male Santa Inês lambs (a breed common in tropical regions) divided into three groups based on how efficiently they converted feed into weight gain
- Key finding: High-efficiency lambs produced 15.2% less methane per kilogram of food eaten compared to low-efficiency lambs, though this difference wasn’t statistically significant. No major differences were found in stomach fermentation between groups
- What it means for you: If you raise sheep, selecting for feed efficiency might slightly reduce environmental impact, but the effect is modest. The study suggests that measuring efficiency in young animals may not be reliable across different growth stages
The Research Details
Scientists divided 40 young male lambs into three groups based on two measurements: residual feed intake (how much extra food an animal eats beyond what’s needed for growth) and residual income growth (how much weight they gain beyond expected). The low-efficiency group ate more than needed and gained less weight. The high-efficiency group ate only what they needed and gained more weight. The medium group fell in between.
The lambs were fed the same diet in two separate phases while living in individual chambers that could measure the methane gas they produced. Researchers collected samples of fluid from each lamb’s stomach to analyze how food was being broken down and counted the tiny organisms living in their stomachs that help with digestion.
They used statistical methods that could track changes in each animal over time, comparing how the three groups differed in their feeding patterns, weight gain, methane production, and stomach chemistry.
This research approach is important because it tries to understand whether animals that naturally waste less food also produce less environmental pollution. If feed efficiency and lower methane emissions go together, farmers could breed for both traits at once. However, measuring these traits accurately in young animals is challenging because they change as animals grow
The study was well-designed with controlled feeding conditions and direct methane measurements in individual chambers, which is more accurate than estimates. However, the lack of significant differences in most measurements suggests the study may have been underpowered or that the diet used was too uniform to reveal differences between groups. The authors acknowledge that feed efficiency classifications may not be stable across different life stages, which limits how useful these results are for long-term breeding decisions
What the Results Show
The most striking finding was that high-efficiency lambs numerically produced 15.2% less methane per kilogram of dry matter intake compared to low-efficiency lambs. However, this difference was not statistically significant (P > 0.05), meaning it could have occurred by chance.
No significant differences were found between the three efficiency groups in dry matter intake (how much food they ate), body weight, or total methane emissions. This was surprising because researchers expected more efficient animals to show different patterns.
When scientists examined the stomach fermentation parameters—the chemical processes breaking down food in the stomach—they found no meaningful differences between groups. The number and types of tiny organisms living in the stomach were also similar across all three groups. This suggests that the lambs’ stomachs were working similarly despite their different feed efficiency levels.
The study revealed that using residual feed intake and residual income growth to classify animals may not be as reliable as hoped. These measurements appear to be sensitive to the animal’s age and life stage, meaning a lamb classified as ‘high efficiency’ at one age might not maintain that classification as it grows older. This finding is important for farmers considering selective breeding based on feed efficiency
Previous research in cattle and other ruminants has suggested that feed efficiency should correlate with lower methane emissions, but results have been mixed. This study adds to growing evidence that the relationship between efficiency and emissions may be weaker than expected, especially in young animals. The uniform diet used in this study may explain why differences weren’t more pronounced—other research using more varied diets has sometimes found stronger differences between efficiency groups
The study had several important limitations. First, the lack of significant differences in most measurements suggests the results may not be reliable for making practical decisions. Second, the uniform diet may have masked differences that would appear with more varied feeding. Third, the study only followed lambs through two phases of growth, so it’s unclear whether efficiency classifications would remain consistent as animals mature. Finally, the study focused only on male lambs of one breed, so results may not apply to females or other sheep breeds
The Bottom Line
Based on this research, feed efficiency alone is not a strong enough indicator for reducing methane emissions in lambs (low confidence). If you’re interested in breeding for feed efficiency, do so for economic reasons, but don’t expect major environmental benefits. Consider that efficiency classifications may change as animals grow, so evaluate them at the age most relevant to your operation (moderate confidence)
Sheep farmers interested in reducing feed costs should care about this research, as feed efficiency directly impacts profitability. Environmental advocates interested in reducing livestock methane emissions should note that selecting for feed efficiency alone may have limited impact. Researchers studying ruminant digestion should consider that stomach fermentation patterns may not explain efficiency differences
If you were to select breeding animals based on feed efficiency, you would likely see economic benefits within one generation (12-18 months for lambs). However, environmental benefits from reduced methane would be modest and might take multiple generations to accumulate if breeding is continued
Frequently Asked Questions
Do more efficient lambs produce less methane gas?
High-efficiency lambs produced 15.2% less methane per unit of feed in this study, but the difference wasn’t statistically significant. The relationship exists but appears weaker than previously expected, suggesting feed efficiency alone isn’t a reliable way to reduce methane emissions.
Can you predict which lambs will be efficient at different ages?
Not reliably. This research shows that feed efficiency classifications are sensitive to the animal’s life stage and may change as lambs grow. A lamb classified as efficient at one age might not maintain that status later, making long-term predictions difficult.
What causes differences in how efficiently lambs use food?
This study found no differences in stomach fermentation or digestive microorganisms between efficient and inefficient lambs, suggesting the causes of efficiency differences aren’t related to how their stomachs break down food. Other factors, possibly related to metabolism or activity levels, may explain the differences.
Should farmers breed sheep for feed efficiency?
Yes, for economic reasons—efficient animals cost less to feed and produce more weight gain. However, don’t expect major environmental benefits from reduced methane. Efficiency classifications may shift across growth stages, so evaluate animals at the age most relevant to your operation.
Why didn’t the study find bigger differences between efficient and inefficient lambs?
The uniform diet used in the study may have limited differences between groups. Previous research with more varied diets sometimes found stronger differences. Additionally, measuring efficiency in young animals may be unreliable since classifications can change as they mature.
Want to Apply This Research?
- Track feed intake and weight gain weekly for individual lambs, calculating the ratio of feed consumed to weight gained. Record this as ‘feed conversion ratio’ to identify your most efficient animals over time
- Use the app to set feeding targets based on your most efficient animals’ consumption patterns, then monitor whether other lambs can match those targets. Adjust rations if some animals consistently exceed efficient animals’ intake without proportional weight gain
- Monitor feed efficiency across multiple growth phases (young, growing, finishing) rather than relying on a single measurement. Track whether animals classified as efficient at one age maintain that status as they mature, helping you understand which animals are consistently efficient
This research is preliminary and based on a single study of 40 lambs. The findings were not statistically significant for most measurements, meaning they could have occurred by chance. Farmers should not make major breeding or management decisions based solely on this study. Consult with veterinarians and animal nutritionists before implementing changes based on feed efficiency classifications. Results may not apply to different sheep breeds, ages, sexes, or dietary conditions. This information is for educational purposes and should not replace professional agricultural advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.