While most of the state remains drought affected, a few fortunate areas, including much of the Central Tablelands, have had a run of storms and so now have (or had) green feed.
As always, summer storms are a mixed blessing, filling dams (sometimes with rubbish) and boosting summer active pastures and crops, but creating a few animal health problems.
A producer called me several weeks ago because he had lambs on a crop of grazing brassica with swollen ears and eyes.
Fortunately, the photosensitisation seen in lambs on grazing brassica is not associated with liver disease.
This means that the lambs will recover if they are removed from the crop.
However, a crop of grazing brassica, valuable any time, is especially treasured this year so the manager and I decided to try drafting off the few affected lambs and running them in a shady alternate paddock, but leave the unaffected remainder on the crop. This has worked well with no further cases.
Agronomists advise that brassica crops should not be grazed until they are mature (normally about 10 weeks after sowing, although I understand this does vary with background plant genetics).
This reduces the risk of photosensitisation.
Another producer called a couple of weeks ago because he had lambs, but not the accompanying ewes, with swollen sunburned ears on a paddock with flowering St John’s wort.
Again, we know that St John’s wort causes pale and thin skinned stock to be sensitive to sunlight (which is part of the reason why lambs are affected before ewes) without liver disease.
The producer removed the mob from the paddock and we discussed the challenges of St John’s wort control.
Unfortunately, practices such as rotational grazing that favour deep rooted perennials also favour St John’s wort.
The lambs recovered in a shady paddock after several days.
I have also had numerous discussions with producers reporting sick and dying sheep with swollen ears and sunburned faces.
Some of these have been grazing brassica crops and some have been on pastures dominated by summer grasses.
As mentioned, veterinarians find that lambs don’t die on paddocks of brassicas (or St John’s wort) unless they become severely sunburned.
It is another plant that is causing the deaths, both in summer grass pastures and brassica crops. On the Central Tablelands the culprit is usually sweet panic (Panicum gilvum).
In other areas the main toxic plant is either witch grass (Panicum capillare), hairy panic (Panicum effusum) or the summer weed cathead (Tribulus terrestris).
As this problem is seasonal, sweet panic, which looks like just another summer grass, can catch unaware producers.
Others know only too well from bitter experience that all of these plants can cause major mortalities in sheep.
Of interest, several producers have then grazed steers on sweet panic dominant pastures with no ill effects and good growth rates.
Many of the panic grasses are capable of causing photosensitisation.
White French millet, grown for seed has occasionally, inadvertently, been grazed with serious consequences but this has not occurred recently to the best of my knowledge.
