PRESERVING forage to provide winter feedstocks is critical for all livestock farmers and ensuring a high quality of preservation through growing, harvesting, ensiling and storage is important to maintain maximum nutrient quality and palatability but also to prevent effects on animal health, animal production and also human health through the food chain.

Spoilage organisms including clostridia species can be present from contamination in the field with soil, manure or small carcases.

Inadequate fermentation allows these bacteria to multiply and potentially produce toxins which cause severe disease and sometimes death.

Poor drying can also allow moulds to grow on hay and straw and the bales may appear visibly normal. Some species of fungi can grow in acidic conditions, including aspergillus species and many can produce harmful mycotoxins.

Silage spoilage often occurs during secondary fermentation when oxygen penetrates poor sheeting, punctured wrapping, messy clamp faces or stale feed.

Harmful organisms present in low numbers without oxygen are given an opportunity to replicate to dangerous levels when air is available.

The risks to animal health from spoiled forages are well documented, but continue to cause clinical disease.

Listeria monocytogenes is a soil bacterium which can contaminate silage causing ocular disease, meningitis and abortion.

Bacillus licheniformis, aspergillus and other fungal species are also commonly diagnosed as causes of abortion.

The photograph shows fungal plaques growing on the skin surface of an aborted calf examined this year.

Abortions may be sporadic and affect a small proportion of the herd or flock, but larger outbreaks of disease related to forage can occur.

A submission to SAC vet services investigated in the last year highlighted the devastating impact poorly preserved forage can have when five rotten calves were aborted close to or at full term in a small suckler herd.

There was a history of the cows being fed poor quality wholecrop silage.

The same species of fungus was cultured from inside one of the aborted calves and also from a feed sample.

A further calf born live from the group died and a fungal infection of the intestinal tract was also confirmed in that case.

Making perfectly preserved forages every time is extremely difficult but when there is spoilage ensure it is discarded and not used for feed or bedding, particularly for pregnant animals.

The costs associated with not doing so can be hefty