Rayner Reckons

Mar 19

Know the risks of Nitrate & Prussic Acid in your feed

Posted on Tuesday, March 19, 2019

Feeding stock is a task that requires some prior preparation.  While most feeds can be provided to ruminants, it doesn’t mean that you can feed them without following a few simple rules.  

 

The rumen is a living environment, which hosts the micro-flora, fungi and other organisms that actually work to break feed down so that it can be absorbed and used by the animal.  Sudden changes in feed type, lack or roughage and reduced water intake can all create a situation where the environment of the rumen becomes unhealthy to the micro-flora and results in digestive upsets and illness.

 

Mostly the rumen remains fairly stable as livestock select diets that allow the rumen micro-flora to thrive and do their job of breaking down material for absorption and digestion.  Problems start to arise when diets and rations are offered that create unhealthy rumen environments. 

 

As mentioned before common issues are changes in feed types, particularly to including grains that have high levels of starch.  It also occurs when fibre is lacking or if rations are less than the animal requires and as it becomes hungrier it eats plants that may contain toxins that can result in illness or death.

 

Poisoning is a risk that many producers have had to consider this year. Common issues have been weeds that have been eaten as hungry stock eat whatever they can chew.  It also has been an issue as new weeds arrive in drought feeds. Stock may consume plants that are poisonous simply because they have never seen them before.  

 

However the biggest issue has been with sorghum crops that have been grazed or cut for fodder.  The cause has been either from Nitrate poisoning or from Prussic Acid.  

 

What is Nitrate Poisoning?

 

Nitrogen is needs by plants for growth.  They absorb nitrogen through the soil and root system.  Young plants and leaves have high levels of nitrates as they are growing. However when plants are stressed or not growing at a rate that allows the nitrogen to be used, the plant stores this as nitrate.  Some plants are more prone than others to do this (they are known as ‘nitrate accumulators’), but most plants will accumulate nitrates to some degree if stressed.

 

The issue for livestock is that when the material is eaten that Nitrate is converted to nitrite.  This chemical change allows the nitrite to be quickly absorbed from digested feed into the blood system where it attaches to hemoglobin.  These nitrites replace oxygen cells in the blood and cause rapid impacts on the animal.  

 

Within 15-20 minutes symptoms like staggering, difficulty breathing, spasms and foaming at the mouth start to occur. Many affected animals will lie down while some may thrash about.  I’ve had it described to me that the cattle looked drunk.  

 

Its mainly sheep and cattle impacted in this way.  Horses and pigs are less affected by nitrate because they don’t convert it to nitrite. If levels are high though, the nitrate can damage the lining of their gut.

 

According to a number of sources, most of the species commonly grazed in Australia can cause nitrate poisoning if stressed.  These are species that include oats, sorghum, maize, sudan grass, Johnson grass, canola, lucerne, kikuyu, turnip and sugar beet tops, soybean, wheat, barley and a range of weeds.

 

It’s essential that you consider feed testing any fodder that you purchase to see what level of nitrate is in the feed.  Ask a few questions from the vendor?  Was it treated with a big application of fertilizer or manure?  Was it stressed before bailing?  These questions can help you decide if it is suitable to feed to livestock

 

Prussic Acid

 

Prussic acid is a major concern for producers who graze or rely on sorghum varieties for fodder.  It is present in most sorghum, although some varieties will have lower levels.   

 

At a chemical level within the plant, prussic acids exist as a non-poisonous chemical called Dhurrin.  This chemical can react with another plant-based material known as Emulsion.  Under the right conditions, these two materials will react and create Prussic Acid.  It’s also known as Hydrocyanic Acid.  In simplest terms this is Cyanide Poisoning!

 

Damage to the pant through mechanical impact, environmental stress, trampling and even insect damage results in the mixing of these materials and the release of Cyanide.  

While sometimes this can evaporate from the plant, it doesn’t all disappear.  It also means that further damage, such as harvesting, or grazing will result in more Cyanide being released. 

 

The concern with Prussic Acid is its high level of toxicity.  Feed Central suggests that amounts greater than 0.1 percent (1000 ppm or mg/kg) of plant dry matter is considered highly dangerous. Some levels from the Washington State University place that level even lower at 750 ppm.

 

The effect on animals is very similar to that of nitrate poisoning. The acid is readily absorbed into the bloodstream and it then attaches to the hemoglobin and displaces oxygen.  

 

Since many producers look to graze or use sorghum forage there are some basic considerations to be factored into the decision making process.  Remember that: 

  • Leaf blades normally contain higher levels than leaf sheaths or stems
  • Younger (upper) leaves have more prussic acid than older leaves
  • Tillers and branches (“suckers”) have the highest levels, because they are more leaf than stalk

 

Most sorghum should be grazed when they are more mature.  Often this is over 3ft in height.  As plants mature, there are more stalks than leaves in the overall plant causing prussic acid content in the plant as a whole to decrease.

 

With so much drought-affected crops its important to remember levels will be much higher as the pants are mostly leaves. Sorghum grown in drought may retain high levels of prussic acid, even if made into hay or silage.

 

My advice to all producers thinking about using or grazing sorghum is to get it tested first!  Know the levels before you feed it out.  There may be alternative uses to this feed. 


If you do have concerns, or you want some more advice, then get in touch with me. Asking questions can save you a lot of risk and the potential of stock losses.

Mar 01

How long will your stock water last?

Posted on Friday, March 01, 2019

The summer of 2019 has been another very hot and dry season.  Coming off one of the hottest years on record, with low rainfall, this summer has had a big impact on most agricultural programs.  

Perhaps the biggest challenge for graziers will be access to reliable stock water.  Of all the resources available to graziers, stock water is the most vital, and generally the most limiting. Water plays a role beyond ensuring survival.  The quality of water offered will impact on feed intake levels and can restrict livestock production if it is outside acceptable ranges.

So how much do your animals consume?  Daily consumption varies with the size of your animals, their production status.  Obviously a lactating animal will require more water than a dry animal.    The feed animals are consuming and weather conditions will also determine daily consumption levels.

As can be seen in this table, consumption for livestock is often higher than many people consider.  Dry cattle for example will require between 50 – 70 litres a day depending on their size. However, hot conditions will see that level of consumption increase significantly.  

Some research presented by Future Beef noted that rises of 10ºC (e.g. from 25ºC to 35ºC) can almost double daily consumption, particularly if there is high humidity as well. Its also important to recognize that lactating cows may have a 30% higher daily water intake than dry cows.

Water quality is a key factor in livestock intake.  There are several components to water quality.  

  • pH will impact on consumption and influence feed intake and rumen function.  Low pH (more acid) will impact on rumen acidosis levels and suppress feed intake. While higher pH levels (more alkaline) will cause rumen upset, diarrhoea and poor feed conversion.  
  • Salinity levels will also determine consumption levels. Salinity tests on water assess the sum of all mineral salts in water. Salinity can impact animal health as a result of their feed, temperature and humidity and the levels of salinity in the water itself
  • Algae, contaminants such as mud or debris from storm run off, and contamination from faeces are all issues that will restrict intake or cause health issues.

If you are concerned about the quality of the water your stock are accessing you can obtain water test kits from your State DPI or Agriculture Departments. (NSW DPI) (Western Australia) 

How much water is in your dam?

Part of any plan regarding water is to know how much you have stored.  Most people I speak with don’t really know how much they may have in a dam or in total, which can significantly add to the stress levels people feel.  

The easiest way to work through estimating a dam’s water amount requires:

  • a tape measure
  • some very strong twine (like plumbers line)
  • two heavy duty lead sinkers
  • a dozen (or more) fishing floats.

Firstly you need to attach the sinkers to the end of the line.  Then tie a slot every metre from the end of the line. Number each float with a large number suing a colour you can read easily.

Step 1:  Measure two sides of your dam (this allows you to work out your surface area in square metres)

Step 2:  Drag your sting across the deepest part of your dam and allow the floats to bring the line to vertical.

Step 3:  Read the number of the float holding the line vertically.

Step 4:  Multiply the surface area (From Step 1) by the depth you have just measured.  

Step 5:  To allow for the shape of your dam, multiply this figure by 0.4.  This will tell you the total volume of your dam.  

Step 6:  To convert this total to mega-litres, divide the number by 1000.  

Doing this exercise once a month will give you a fairly accurate stock take of water supply.  If you calculate how many animals you have, and how much they drink each day, you will soon determine your overall levels of consumption.  

Dividing this consumption by your total water supply will give you a time period for your current water supplies.

Effective plans need to have a time frame, and if your water supplies are the most limiting issue on farm, then it’s vital to have a time estimate.  This estimate gives you the chance to make new plans and be proactive in your management, rather than responding or reacting when your options are much more limited.

When you do these evaluations, you will quickly determine that trucking water to stock is a task that can't be done effectively. The shear demand of water, let alone time and access may make the exercise extremely difficult.  For many people trucking water is an impossibility when they realistically assess their livestock demand and the resources and time they have to meet the daily demand of livestock.  Early planning will help you weigh up your options and focus you on using your limited resources as well as you possibly can.

If you need help in making plans or you require some advice, please don’t hesitate to get in touch.  This is a key service I provide to producers and I’m happy to help where I can.


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