Evaluating a Cow's Manure Output Can Provide You With Valuable Input!

Simple manure observations can tell a lot about rumen function and ration digestion. Taking a few minute on a regular basis to look at the manure excreted by your cows can help in identifying potential problems. There are three aspects of manure that can be considered: colour, texture and content.

Manure Colour

The colour of the manure can be influenced by factors such as type of feed, passage rate (the amount of time the feed remains in the animal), health disorders and so on. Depending on the type of forage, the colour can vary from dark green (fresh forages and pasture) to brown (dry hay).

A total mixed ration with a substantial level of concentrates can turn the manure to a yellow-olive colour. Amongst a group of cows receiving a similar ration, manure colour should be uniform between animals. If the manure colour from one particular animal is significantly different than the rest of the group, further investigation is suggested.

Manure Texture

The texture of the manure can provide key information as well. Manure consistency is linked to water and fibre content and is influenced by factors such as feed moisture content, type of feed and rate of passage. Under normal conditions, manure from lactating cows should have a porridge-like consistency and forms a dome-shaped pile of 2.5-5 cm high when freshly dropped. Nevertheless, many factors will affect the consistency of manure which can range from very liquid (like pea soup) to very firm (horse like).

Cows with liquid or runny manure may have too much protein, high levels of rumen degradable protein or starch in their ration. It may also be caused by a lack of effective fibre, excess salt or mineral imbalance. When extensive hind gut fermentation of carbohydrates takes place, the increased acid production can lead to runny manure. In this case, fine gas bubbles can give a foamy appearance to the manure. Foamy manure should be investigated promptly as it can be a sign of rumen acidosis (when rumen pH becomes too acidic). Cows grazing on lush pasture can produce runny manure as well with distinctive colour. Loose manure may have non nutritional origins such as heat stress, poisoning, infection and parasites.

If the manure consistency is thick or even firm, like horse droppings, this could be an indication of too little protein or starch in their ration or a very fibre rich ration. Dehydration could also lead to firm manure. Manure content

Technically, what ends up in the manure is considered non digestible. Sometimes though, some of the material could have been digested but was not because of various factors. Potentially digestible material that ends up in the manure might suggests problems with rumen function, feed processing, or feeding management. This undigested feed never had a chance to be converted to milk, and so costs of production are increased. Grains 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. If the cow does not eat enough fibre to maintain rumination and rumen function, feed can pass out of the rumen more quickly and in larger particles than it should; if this happens, digestibility can be reduced. High producing cows do eat more and rumen contents pass down the digestive tract more quickly, so more undigested feed may show up in the manure. The ration can be managed to minimise this though.

Under optimal conditions, most feeds are fermented in the rumen and less passes to be digested in the small intestine or fermented in the hindgut (cecum and large intestine). When the rumen is not working well, more undigested feed escapes rumen fermentation and the amount of feed fermented in the hindgut can increase. Increased hindgut fermentation generates an increase in gas and acid production that can change the consistency and appearance of manure. Excessive hindgut fermentation can cause diarrhea and foamy manure. The hindgut is not as buffered and can't handle the acidity as well as the rumen can.

Washing Manure

An effective way to evaluate the content of manure is to wash it down with water. Washing manure through a screen or a kitchen sieve (dedicated for this purpose!) allows one to quickly find if feed processing and digestion is optimal. The procedure is quite simple. A representative sample of manure is collected in a container and thoroughly mixed. A cup of the mix is then place in the sieve (Figure 1) and washed with a stream of water through the screen to remove the digested material. Once the water runs clear, observe the remaining material. Look for feed particles, pieces of grain containing starch or whole hard grains. Fibre particle size should be evaluated as well (Figure 2).
Figure 1: Mixed manure sample placed in a sieve for washing and inspection.

Figure 1: Mixed manure sample placed in a sieve for washing and inspection.

Figure 2: Evaluating fibre particle size in manure sample.

Figure 2: Evaluating fibre particle size in manure sample.

Ideally, few feed particles in the manure should be more than 1.25 cm (0.5 inches) long. There should be little, if any, recognizable feed present. Presence of long particles or undigested material can be an indication that cows are sorting feed, receive too much grain in one meal or lack effective (long) fibre.

Manure is more than a source of nutrient for your fields. It can be used as an indicator of feed efficiency and animal health. Next time you are with your herd, take a few minutes to observe your cow's manure and wash some down in a sieve. You could be surprised of you will see and learn. Your herd nutritionist can help you make some adjustments to the cow ration in order for your animals to be healthy, efficient and productive.

For more information:
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