The article by K. L. Blaxter and J. L. Clapperton from the Hannah Dairy Research Institute in Ayr, Scotland, focuses on predicting methane production by ruminants. The authors use closed-circuit respiration equipment to measure methane production over 24-hour periods in sheep and cattle. They analyze the data from over 2500 determinations to understand the factors affecting methane production, including the type and amount of diet, the feeding level, and individual differences among animals. Key findings include: 1. **Analytical Accuracy**: The method used to measure methane production had a standard deviation of ±0.08% for a 4-day period, with a total instrumental and analytical error of less than ±3%. 2. **Day-to-Day Variation**: Methane production showed a small but statistically significant decrease on the first day of confinement, followed by a day-to-day variation of ±7.2%. 3. **Long-Term Variation**: Over longer periods (26-46 days), some sheep showed a slight increase in methane production, possibly due to a slow adjustment of their gut flora. 4. **Individual Differences**: There were significant differences in methane production among individual sheep, even when fed the same diet. 5. **Effect of Diet**: Methane production increased with the apparent digestibility of the diet, but the increase was less pronounced with high-quality feeds. 6. **Feeding Level**: Doubling the feeding level depressed methane production more with high-quality feeds compared to low-quality feeds. The authors conclude that methane production is influenced by both the diet's digestibility and the feeding level, with higher digestibility leading to greater methane production per unit of feed consumed. They provide regression equations to predict methane production based on these factors, with an error margin of approximately ±8% of the mean amount of methane produced.The article by K. L. Blaxter and J. L. Clapperton from the Hannah Dairy Research Institute in Ayr, Scotland, focuses on predicting methane production by ruminants. The authors use closed-circuit respiration equipment to measure methane production over 24-hour periods in sheep and cattle. They analyze the data from over 2500 determinations to understand the factors affecting methane production, including the type and amount of diet, the feeding level, and individual differences among animals. Key findings include: 1. **Analytical Accuracy**: The method used to measure methane production had a standard deviation of ±0.08% for a 4-day period, with a total instrumental and analytical error of less than ±3%. 2. **Day-to-Day Variation**: Methane production showed a small but statistically significant decrease on the first day of confinement, followed by a day-to-day variation of ±7.2%. 3. **Long-Term Variation**: Over longer periods (26-46 days), some sheep showed a slight increase in methane production, possibly due to a slow adjustment of their gut flora. 4. **Individual Differences**: There were significant differences in methane production among individual sheep, even when fed the same diet. 5. **Effect of Diet**: Methane production increased with the apparent digestibility of the diet, but the increase was less pronounced with high-quality feeds. 6. **Feeding Level**: Doubling the feeding level depressed methane production more with high-quality feeds compared to low-quality feeds. The authors conclude that methane production is influenced by both the diet's digestibility and the feeding level, with higher digestibility leading to greater methane production per unit of feed consumed. They provide regression equations to predict methane production based on these factors, with an error margin of approximately ±8% of the mean amount of methane produced.