What's the scoop on evaluating manure?
There are many ways to evaluate whether your feeding program is on track. These include milk production, milk components, metabolic disorders, cud chewing, and particle size of feed fed and refusals. One other monitor is evaluation of manure. It’s a dirty job, but somebody needs to do it. Manure evaluation is not a precise science, but used along with other measures it can help confirm other observations and determine how well cows are digesting their ration.
Every day when walking through the pens, manure should be observed. Here are some observations to look for:
- Is the consistency the same throughout the group? Normally you would expect porridge-like consistency that forms a patty 1-2 inches high. Loose manure can be caused by low fiber diets, high protein feeding and possibly feeding diets high in salt and buffers. If more that 5-10% of the cows are dissimilar from the others, it may be a sign cows are sorting their feed. This is particularly true if some cows have stiff manure and others have loose manure. If all cows suddenly become loose, it may be a ration change, winter dysentery or other disease. If it continues, alert your nutritionist and veterinarian to determine a possible cause.
- Are there cow pies that are foamy or contains bubbles? Foamy and bubbly manure is caused by hindgut fermentation. Large amounts of grain are leaving the rumen undigested and is fermenting in the hindgut. This is one sign of acidosis. If it is an entire pen, contact your nutritionist immediately. If it is different cows everyday, it may be mixed feed, cow sorting the ration or rations that are on the edge of too much grain.
- How much corn is in the manure? Is there more or less corn than in previous days? Is the amount of grain similar from cow to cow? It is normal to have some grain coming through high producing cows, but if it is excessive, try and determine the source (corn silage or corn grain). If it is from corn grain, the problem may be solved by processing the corn finer. If it is from corn silage, there is not a lot that can be done, short of rolling the corn silage. However, your nutritionist can adjust the diet realizing that the corn silage does not contain as much energy if a large amount of corn is passing through the cow.
It would also be a good idea to periodically wash the manure through a sieve or strainer. Collect at least 5 representative samples from the group of animals. If you see a significant number of abnormal feces, take a sample and wash those also. Using a hose, gently wash the sample until the water runs clear. Here is what to look for in the washed manure samples:
- Are there many fiber particles longer than ½ inch in length? You will find a few long particles, but they should be a small percent of the total. Long fiber particles are an indication of poorly digested forages. It may be caused by very poor quality forages, poor rumen mat formation and/or poor rumination. This can be a sign of low rumen pH and cows that are borderline acidosis.
- Are there signs of recognizable undigested feed? This would include cottonseed with lint still on, large numbers of seeds such as cottonseed and soybeans, and/or large amounts of small undigested grain particles. In a well functioning rumen, these feedstuffs should get trapped in the rumen mat for digestion. Undigested feedstuffs in manure may be a sign of poor rumen mat formation and digestion.
- Is there presence of mucin casts in the manure? Mucin casts looks like pieces of intestine that are shed in the manure. Mucin casts is the cow’s response to excess hindgut fermentation or other injury to the gut. This results in a sloughing of the surface cells of the intestine. If the injury is severe enough, the intestine secretes mucus to protect the injury. Again, this can be a sign of acidosis.
Manure evaluation is just another tool you can use to get a sense of how cows and their rations are interacting. Combining this information with cow health and performance can give you a better indication of how your rations are performing, and help you to fine tune rations and feeding management to increase profitability.
Published in Dairy Star December 24, 2005