Researchers wanted to find a way to reduce the stinky ammonia smell from cow manure while keeping milk production healthy. They tested different diets on dairy cows, including one that made the manure less acidic and two versions with added supplements. The good news: they found a way to cut ammonia emissions by 18% using a special diet. Even better, when they added certain supplements to this diet, the cows still produced plenty of milk and milk fat, just like they normally would. This could help dairy farms reduce bad smells while keeping their milk production strong.
The Quick Take
- What they studied: Can changing what we feed cows reduce the ammonia smell from their manure without making them produce less milk?
- Who participated: 16 adult dairy cows (Holstein breed) that were in the middle of their milk-producing cycle. The study lasted about 3 weeks per diet test.
- Key finding: A special low-mineral diet reduced ammonia emissions by 18% compared to regular feed. When researchers added palmitic acid or a methionine supplement to this diet, cows produced normal amounts of milk and milk fat again.
- What it means for you: If you live near a dairy farm, this research suggests farms may be able to reduce unpleasant manure odors while still producing plenty of milk. However, this is early-stage research, and farms would need to test if this works in real-world conditions.
The Research Details
Scientists used a study design called a Latin square, which is like a puzzle where each cow tries each diet in a different order. This helps researchers see if the diet itself causes changes, not just differences between cows. Sixteen cows were divided into groups, and each group ate four different diets over time. Each diet lasted 3 weeks—the first 2 weeks let the cows adjust, and the last week was when scientists collected samples.
The researchers collected cow manure and measured how much ammonia gas came from it using special chambers that captured and measured the gas over 7 days. They also tracked how much the cows ate, how much milk they produced, and tested their blood and urine to understand what was happening inside their bodies.
The four diets tested were: a normal control diet, a low-mineral diet (which makes urine more acidic), the low-mineral diet with added palmitic acid (a type of fat), and the low-mineral diet with a methionine supplement (an amino acid that helps with milk production).
This study design is strong because each cow serves as its own comparison. By having cows eat different diets at different times, scientists can see the real effect of each diet without worrying that some cows are naturally different from others. Testing the manure directly in chambers gives accurate measurements of ammonia, which is more reliable than just guessing based on diet composition.
This is a well-designed study published in a respected dairy science journal. The sample size of 16 cows is reasonable for this type of research. The study carefully measured multiple outcomes (feed intake, milk production, blood chemistry, ammonia emissions) which strengthens the findings. However, the study only lasted 3 weeks per diet, so we don’t know if these effects would continue long-term. Also, all cows were the same breed and age group, so results might differ with other types of cows.
What the Results Show
The main finding was that the low-mineral diet successfully reduced ammonia emissions by 18% (from 89.1 grams to 73.2 grams per cow). This happened because the special diet made the cows’ urine more acidic, which prevented ammonia from forming in the manure.
However, there was a trade-off: cows eating the low-mineral diet ate about 1 kilogram less food per day and produced about 1.8 kilograms less milk per day compared to the control diet. This is a problem because dairy farmers need their cows to produce milk.
The exciting part came when researchers added supplements. When they added palmitic acid or a methionine supplement to the low-mineral diet, the cows produced normal amounts of milk fat again—almost matching the control group. The cows still ate slightly less food, but their milk production improved significantly.
Blood tests showed that the low-mineral diet caused the cows’ blood to become slightly more acidic, which is expected and appears to be what caused the ammonia reduction. Adding the supplements didn’t change this effect but helped protect milk production.
Milk protein production was lower with the low-mineral diet (1.22 kg/day vs. 1.27 kg/day), but this difference was small. Interestingly, the low-mineral diet increased the amount of urea in the cows’ blood and urine, suggesting their bodies were processing protein differently. The supplements didn’t fully restore protein production to normal levels. The composition of fats in the milk changed slightly with the palmitic acid supplement, which is expected since that’s a type of fat.
This research builds on earlier work showing that low-mineral diets could reduce ammonia. The new contribution is showing that supplements can help prevent the negative effects on milk production. Previous studies had shown that low-mineral diets hurt milk production, which limited their usefulness on real farms. This study suggests a practical solution by combining the low-mineral diet with specific supplements.
The study only lasted 3 weeks per diet, so we don’t know if cows would stay healthy long-term on these diets or if the effects would continue. Only 16 cows were tested, and they were all the same breed and age, so results might be different for other types of dairy cows. The study was done in a controlled laboratory setting, not on a real farm, so we don’t know how well this would work in actual farming conditions. The researchers didn’t test whether the supplements alone (without the low-mineral diet) could reduce ammonia, so we can’t be sure the supplements are necessary.
The Bottom Line
For dairy farmers: This research suggests that feeding cows a low-mineral diet supplemented with palmitic acid or methionine may reduce manure ammonia by about 18% while maintaining milk production. However, this is preliminary research from a controlled study. Before making changes, farmers should consult with their veterinarian and nutritionist, and consider testing this approach on a small scale first. Confidence level: Moderate—the science is sound, but real-world results may vary.
Dairy farmers concerned about manure odor and environmental impact should pay attention to this research. Communities near dairy farms may also benefit from reduced ammonia emissions. This is less relevant for people who don’t work with livestock. Cows with existing health issues might not be good candidates for diet changes without veterinary guidance.
Based on this study, ammonia reduction would likely happen within days of starting the new diet (since urine pH changed quickly). However, the full effects on milk production took the entire 3-week study period to stabilize. On a real farm, it might take 2-4 weeks to see consistent results.
Want to Apply This Research?
- If you manage a dairy farm, track daily milk production (in kilograms), feed intake (in kilograms), and estimate manure odor on a scale of 1-10 before and after implementing dietary changes. Record these weekly to see if production stays stable while odor decreases.
- Work with a dairy nutritionist to gradually transition cows to a low-mineral diet supplemented with palmitic acid or methionine over 2-3 weeks. Monitor milk production daily and adjust if production drops more than 5%. Keep detailed records of feed costs versus any savings from reduced odor complaints.
- Establish a baseline of current ammonia odor levels and milk production for 2-4 weeks. Then implement the dietary change and track the same metrics for 8-12 weeks. Compare the two periods to see if ammonia reduction occurs without harming production. Consider having a professional measure ammonia levels if possible.
This research is preliminary and was conducted in a controlled laboratory setting with a small number of cows. Results may not apply to all dairy farms or cow types. Before making any changes to cow diets, consult with a veterinarian and dairy nutritionist. This information is for educational purposes and should not replace professional agricultural or veterinary advice. Individual results may vary based on farm conditions, cow breed, and management practices.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.