Dairy--Feeds and Commodities

DAIRY PROBLEMS WITH FEEDSTUFFS AND NITRATE

As sure as we have a drought we have problems with feedstuffs containing nitrate. Nitrate is the principal precursor to plant protein. Normally, nitrate moves rapidly from the soil up the plant and is converted into plant protein. Under certain conditions, the conversion of nitrate to protein is slowed down or stopped and the nitrate accumulates in the forage. High nitrate levels are a result of stress on the plant due to the drought.

The most dangerous situation occurs with drought-stricken forage for a period of 3-5 days following a recovery rain. Once moisture becomes available, plants rapidly take up nitrates which have accumulated in the soil.

Nitrates can accumulate in almost all of the commonly used forages. Drought stricken corn, sorghum, sudan and sorghum-sudan hybrids present the most problems.

Dairy producers and other cattle producers are alerted to keep this type forage away from cattle. Grazing and green chop feeding are the most dangerous ways to feed high nitrate material. The same crop generally is not as dangerous if fed as silage. In silage making, as much as 60 percent of the nitrogen may be lost during the fermentation period.

Feeding forages with high levels of nitrates can result in lowered milk production, lowered fertility and possible death. How much an animal is hurt, depends on the amount of nitrate ingested.

Level of Nitrate-Nitrogen
on Dry Matter Basis	    Comments

0.0 - 0.10% (0.0 to 1,000 ppm)	This level is considered safe 							
				to feed under all conditions.

0.1 - 0.15% (1000 to 1500 ppm)	This level should be safe to feed to 						
				non-pregnant animals.  Limit to 50% 						
				of the total ration in pregnant animals 						
				(On a dry matter basis).

0.15 - 0.20% (1500 to 2000 ppm)	Limit to 50% of the total dry matter in 						
				the ration.

0.20 - 0.35% (2000 to 3500 ppm)	Limit to 35-40% of the total dry matter 						
				in the ration. Should not be used in 						
				pregnant cows.

0.35 - 0.40% (3500 to 4000 ppm)	Limit to 25% of the total dry matter in 						
				ration. Do not feed to pregnant cows.

The S.C. Department of Agriculture reports nitrates as nitrates so that a conversion factor of 4.4 would have to be used to divide by to get a nitrate-nitrogen reading. Other labs might report as sodium or potassium nitrate so that the following conversion table can be used.

Form of Nitrogen		Conversion Factor
Nitrate-nitrogen (NO3-N)		1
Nitrate (NO2)				3.3
Nitrate (NO3)				4.4
Sodium nitrate (NaNO3)			6.1
Potassium nitrate (KNO3)		7.2

The following tips should be considered when feeding suspect forages:

• Check nitrate level before feeding.

• Don't feed drought-stricken forages for 3-5 days after a recovery rain.

• Don't graze suspect forage.

• Don't cut drought-stricken forages that contain high nitrate levels for hay. The nitrate content in cured hay is stable. Very little leaches out of the hay.

• The best method to feed forages that have been grown under drought conditions where nitrates are suspect is to harvest as wet silage letting the feed harvested go through a complete fermentation process. Anaerobic bacteria can reduce the nitrate level as much as 50-60 percent. A minimum fermentation of at least 21 days is needed before feeding any of the feed. Also, it should be beneficial to use a silage additive to aid in the fermentation process, due to the low carbohydrate content in the forage. Test all suspect silage for nitrates prior to feeding.

• Dilute suspect high-nitrate feeds with feed known to contain low levels.

• Feed balanced rations. High energy rations favor nitrate use by rumen microbes.

• Don't allow hungry animals free access to suspect forage.

• Cut suspect forage at higher than usual heights to avoid possible higher nitrate-containing portions of the stalk.

• Consult a veterinarian promptly when suspected cases of nitrate poisoning are found.