Protein & Nitrogen
in Pasture Grass
Grass sprouting after drought breaking rain
Certain fertilisers will make the clover power ahead.
The grass above was fertilised with Nutrigro. Compare that to the grass below, from the same farm which received no fertiliser and has a range of great grasses...
In the two photographs above, the clover was sprayed out in spring with a broad leaf spray. As you see in the photo taken a couple of months later, the grasses have powered ahead unhindered by clover.
Once this grass seeds and hardens off, it will be perfect for the horses to graze.
At certain times of the year (Spring & Autumn) and under certain climatic conditions (consecutive cloudy days, frosts or after a drought-breaking rain) Crude Protein levels in pasture can increase to levels which cause problems for horses.
Ingestion of excess nitrogen is a contributor to “Grass-Affected” syndrome along with other aspects we are aware of including potassium and sugar levels.
• All Forage and Feed Analyses will include a CP (Crude Protein) reading. Crude Protein in plants is comprised of both ‘true protein’ and ‘spare nitrogen’ or Non-Protein Nitrogen (known as NPN).
• ‘True protein’ is made up of long chains of amino acids all strung together. Nitrogen is required for protein synthesis. Grasses and legumes and certain other broadleaf plants will take up more nitrogen than they need when it is readily available to them.
• In Autumn and Spring, and under conditions mentioned above, CP levels can exceed 20 and even 30%, we have analyzed pasture where horses ran into trouble (laminitis and repeated bouts of colic) with CP levels of 36%!
• When horses consume more than their requirement of nitrogen or protein they will drink more water and urinate more. The urine will be ‘strong’ with a smell of ammonia which can be a problem if the horse is kept in a confined space. Or it may ‘burn’ the grass and leave brown patches in the pasture.
• Nitrogen in the form of Nitrates from plants can have the effect of ‘robbing’ the horse of precious calcium and magnesium, especially when there is a lack of sodium, (just one of the reasons to add salt to your horse’s feed).
• The CP concentration of legumes (Clover & Lucerne) is averagely much higher than grasses. There are other plants which are known ‘Nitrate Accumulators’ - to the point farmers are using them to reduce nitrogen leaching, more coming up on this subject.
• Cattle can utilise the excess NPN in the rumen and build it into true protein but horses cannot.
When CP readings are very high (as after drought-breaking rains or in spring and Autumn) nitrogen can significantly contribute to metabolic problems and be toxic to them. This is one of the reasons that it is difficult for horses to successfully share grazing that is meant for cattle. Their digestive systems are completely different.
• Horses, by choice, avoid consuming grass growing on high nitrogen areas (like where they drop their manure).
• Frequent harrowing of manure has the effect of spreading the nitrogen more evenly and turning it from ‘slow release’ into ‘rapid release’ nitrogen for uptake by the grass. Not saying you should never harrow but a lot of people do it often to keep things looking tidy. Think about whether it is appropriate in your particular grazing situation.
• Urea is another form of NPN. It is not a good idea to fertilise your horse pastures with it (or anything like it: chicken manure, poulfert or NPK).
• Generally speaking the younger and greener the grass the higher in nitrogen it is likely to be. Grass that sprouts after a drought-breaking rain is very potent in both potassium and nitrogen. More mature grass which has slowed down or finished growing tends to look yellower and is proportionately lower in nitrogen.
Merlot and Zephyr out on their perfectly mature summer grass. This grass has zero concerns for grazing.