Use fertiliser to beat selenium deficiency
By Shirley Macmillan
WHERE LIVESTOCK need supplementary selenium this summer producers can use selenium fertilisers to boost forages, but are cautioned to improve soil management and help natural availability too.
Following the withdrawal of organic selenium forms in feedstuffs (see News, Apr 8), Yara says its grazing fertiliser 25:5:5, containing sodium selenate and a declared selenium level of 0.0012%, is another option.
“Sodium selenate is taken up by the plant and converted into seleno proteins which are an organically bound form of selenium that is good for the animal,” says Yara”s Mark Tucker.
Grass plants self regulate their uptake of selenium so won”t accumulate it to toxic levels. Monthly applications of the fertiliser apply less than 12g/ha of selenium in the whole growing season, he adds.
Trials using the Top Stock product have shown increased selenium levels on 11 out of 13 sites, with higher selenium levels in forage dry matter. “Pre-application levels averaged 0.071mg/kg DM of forage, whereas post-application they went up to 0.299mg/kg DM.”
In addition, a 104-cow UK dairy herd showed reductions in mastitis cases and better fertility following applications of selenium containing fertiliser to grassland, says Mr Tucker.
Recent Australian research has confirmed the huge effect selenium has on mastitis and cell counts, says Sussex-based vet Kate Burnby of Stock1st. “It also affects fertility, stillbirths and retained cleansing because it”s an antioxidant, mopping up free radicals and improving the immune system.”
Sub-clinical selenium problems decrease performance, immunity and fertility, extreme deficiencies result in white muscle disease. Miss Burnby suggests producers not only test stock to check selenium levels before supplementing diets, but also forages and soils.
“This can be done at any time, although for spring block calving herds it”s best in autumn prior to drying off; autumn calving herds can test now.”
The bonus of using selenium via fertiliser is that all classes of livestock can be supplemented as both grass and forage levels rise, she adds. “Otherwise it”s common to supplement adults via concentrate but not youngstock.”
While agreeing that selenium in fertiliser is beneficial, independent soil scientist Josephine Scamell warns that many selenium deficiencies are caused by lock-up rather than availability.
“South-west Scotland is naturally selenium deficient, but when ground is compacted, it creates anaerobic conditions causing selenium lock-up. Simple aeration and lime can help release it through natural recycling.”
She also points out the lack of flexibility when selenium is applied to soil. “Once down it can stay for 10 years. It”s safer offered in a feed which can be easily removed from the diet.”
* Boost grass and silage levels
* Needed for immunity
* Check soil and stock status
