Nitrate Poisoning in Dairy Cattle

Recently we’ve had two farms lose cows to nitrate poisoning. On one farm, we were able to intervene and provide help to cows showing clinical signs. Both farms were grazing annual pastures. Keep reading for some helpful information on how to prevent nitrate poisoning on your farm and what to do if you suspect it.

What is it?

Nitrate poisoning occurs when cows eat pasture or crops with high nitrate levels. This reduces the blood’s ability to carry oxygen and can cause sudden deaths, reduced production, or abortion.

High-risk situations

Risk increases with:

• Heavy nitrogen fertiliser use

• Cloudy weather

• Drought or frosted pasture (‘stressed pasture’)

• Hungry cows entering fresh breaks

• Rapidly growing annual grasses (e.g. Tama ryegrass, oats)

High-risk feeds:

• Annual ryegrass

• Cereals

• Brassicas

• Maize regrowth

• Lush pasture

Signs to watch for

Mild/subclinical:

• Reduced production

• Reduced appetite

• Faster breathing

• Fertility issues or abortions

Severe:

• Rapid breathing

• Weakness or staggering

• Tremors

• Chocolate-brown blood

• Collapse or sudden death

What to do

1. Contact your veterinarian immediately

2. Remove cows from suspect feed

3. Feed hay or silage

4. Minimise stress

Treatment

·         IV methylene blue administered by a veterinarian

Prevention

• Never put hungry cows onto risky pasture

• Feed fibre before grazing

• Introduce crops gradually

• Graze risky pasture in the afternoon

• Consider feed testing after heavy N fertiliser use

Important reminder

Low-level nitrate exposure may reduce:

• Conception rates

• Embryo survival

• Milk production

without causing obvious sickness.

We have recently tested pastures with high levels of nitrate around Matamata. If you would like some testing done or if you have any further questions. Please do not hesitate to contact the clinic.