Dairy Cow Manure Visual Evaluation for Ration Adjustment
Evaluating a dairy cow's output can provide you with valuable input for optimizing feed efficiency and animal health. Her manure can indicate the condition of her rumen and intestine to help identify potential problems.
Regularly taking just a few minutes to look at your cows' manure can unearth clues about whether they are eating properly. Manure texture, colour and content can provide key information.
Manure from lactating cows normally has a porridge-like consistency and forms a dome-shaped pile of 2.5 to five centimetres high when freshly dropped. Whether loose or firm, texture should be consistent throughout a group of cows receiving a similar ration. If you observe discrepancies, this could mean some cows are able to sort their feed.
Manure consistency can range from very liquid like pea soup to very firm horse-like droppings. Linked to water and fibre content, manure consistency is influenced by factors such as feed moisture content, feed type and passage rate (the amount of time feed remains in the animal).
Cows with liquid or runny manure may have too much protein, high levels of rumen degradable protein or starch in their rations. A lack of effective fibre, excess salt or mineral imbalance could also cause it.
When extensive hind gut fermentation of carbohydrates takes place, increased acid production can lead to runny manure. In this case, fine gas bubbles can give the manure a foamy appearance. Investigate it promptly since it may be a sign of rumen acidosis-when rumen pH becomes too acidic.
Cows grazing on lush pasture can also produce runny manure with a distinctive dark green colour. Non-nutritional causes of loose manure include heat stress, poisoning, infection and parasites.
If the manure consistency is thick or even firm, like horse droppings, it could indicate too little protein or starch in the ration or a very fibre-rich ration. Dehydration can also lead to firm manure.
Factors such as feed type, passage rate, health disorders and so forth can influence manure colour.
Depending on the forage type a cow consumes, its manure colour can vary from dark green from fresh forages and pasture to brown from dry hay. A total mixed ration with a substantial concentrate level can turn manure a yellow-olive colour.
A group of cows getting a similar ration should have a uniform manure colour. If one animal's manure colour significantly differs from the rest of the group, investigate further.
The most interesting aspect of manure evaluation from both a nutritionist and producer perspective is content. What ends up in the manure is technically considered indigestible material.
Sometimes though, because of various factors, a cow might not digest feed ingredients that she could have digested. Potentially digestible material that ends up in manure might suggest problems with rumen function, feed processing or feeding management.
When undigested feed is not converted to milk, your production cost increases. Grain should not show up in the manure-especially when grain prices are high.
Rumination and digestion by microbes in the rumen break down fibre and feed particle size. When a cow does not eat enough fibre to maintain rumination and rumen function, digestibility is reduced. Feed can pass out of her rumen more quickly and in larger particles than it should.
High-producing cows eat more feed and rumen contents pass through their digestive tracts more quickly. More undigested feed may show up in their manure. However, you can manage the ration to minimize this.
Managing concentrate and forage particle size can greatly improve feed overall digestibility. A particle separator can be useful to sift the ration and evaluate whether the ration has optimal particle size.
Under optimal conditions, the rumen ferments most of the feed, and less passes to the small intestine for digestion or the cecum and large intestine, together known as the hindgut, for fermentation. When the rumen is working poorly, more potentially fermentable feed escapes rumen fermentation and the amount fermented in the hindgut can increase.
Increased hindgut fermentation generates more gas and acid production that can change manure's consistency and appearance. The hindgut is not as buffered and cannot handle the acidity as well as the rumen can. Excessive hindgut fermentation can cause diarrhea and foamy manure.
An effective way to evaluate manure content is washing it down with water through a screen or a kitchen sieve (see sidebar). This simple process lets you quickly find out whether feed processing and digestion is optimal.
What you might see and learn could surprise you. Your herd nutritionist can help you adjust the ration if needed to ensure a healthy, efficient and productive herd.
References: Effect of varying total mixed ration particle size on rumen digesta and fecal particle size and digestibility in lactating dairy cows. D. D. Maulfair, M. Fustini and A. J. Heinrichs; J. Dairy Sci. 94 :3527-3536; Evaluating Rations. Mary Beth Hal, University of Florida. 6th Western Dairy Management Conference proceedings. 2003; p 35-41; Troubleshooting Nutritional Programs. Michael Hutjens. 2000 Kentucky Ruminant Nutrition Conference proceedings p15-27.
SIDEBAR: Washing manure
The manure washing procedure is quite simple. Collect a representative manure sample in a container and thoroughly mix it. Place a cup of the mix in the sieve and wash it with a stream of water through the screen to remove digested material.
Once the water runs clear, check the remaining material. Look for feed particles, pieces of grain containing starch or whole hard grains. Sometimes, careful observation is required since grain hulls can be confused with undigested grain. Make sure by opening hulls to see if starch is still present.
Evaluate fibre particle size as well. Ideally, few feed particles in the manure should be more than 1.25 cm, or half an inch long.
There should be little, if any, recognizable feed present. Presence of long particles or undigested material can indicate cows are not ruminating properly, are sorting feed, receiving too much grain in one meal or lacking effective, or long, fibre.
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