According to NSW DPI this can lead to a progressive and irreversible weakness in a sheep’s hind limbs. This gradually will progress to the forelimbs and eventually the weakness will prevent the animal from standing or accessing feed or water. The disease is only recorded in central NSW, and may take some moths to develop, so it’s one to consider if caltrop is dominating a pasture.
While this disease has been recorded in NSW among sheep flocks, it doesn’t appear to impact cattle.
Several other common weed species that pose risks for nitrate poisoning include Fat Hen; Variegated thistle and Blackberry.
Preventing Poisoning: The biggest risk is often associated with hungry stock accessing these weeds. This rapid consumption of the plant means the rumen microbes cannot quickly convert the high levels of nitrate to ammonia. Animals that are in week or low body condition are also less effective in converting nitrates and are more susceptible to poisoning.
The simplest message for producers is to avoid allowing hungry stock to access these weeds. This may mean fencing off areas that are dominated by these plants until other species have recovered. It also means continuing to maintain drought rations a little longer while pastures re grow. There is an added bonus with these rations. NSW DPI research highlights animals receiving carbohydrate-rich feeds can tolerate high nitrate and nitrite levels better than stock who are not fed. This is because energy from carbohydrates (grain) helps rumen microbes convert nitrite to ammonia.
Kikuyu Poisoning: While an uncommon issue, the last few years have seen a number of coastal and northern NSW producers lose cattle to Kikuyu poisoning. The reasons are not fully understood; however, some research suggests a fungus is associated with the plant and this may be a contributing factor.
Kikuyu poisoning damages the stomachs of cattle, resulting in a situation where fluid accumulates in the rumen, but can’t be absorbed into the blood stream. When this occurs cattle physically can’t drink as their rumen is at capacity. Cattle may try to drink however they are physically unable to take in any water. This leads to dehydration and eventual death.
The challenge with this disease is it’s almost impossible to determine if kikuyu is a risk as affected kikuyu does not look any different to safe kikuyu. However, experience on the north coast of NSW suggests affected kikuyu is likely to be less palatable to cattle and they will avoid it if alternative feed is available.
