Clamping down on poor silage
Author: Alex Walters BVSc MBIAC Cert AVP (CATTLE) MRCVS
Since the 19th century grass silage has become a valuable forage in the nutritional management of most dairy, beef and sheep production systems in the UK. The majority of producers share a common goal during silage making, being to achieve an effectively cut, stored and fed forage. Therefore, targeting optimal nutritional value coupled with high palatability.
However, life doesn’t always go to plan, whether uncooperative contributions from ‘mother nature’ or even minor management failures, problems can often become exacerbated rapidly with costly consequences. Whether producing clamp or baled silage the principals of fermentation remain essentially the same, to preserve grass in lactic acid produced by bacteria within the crop supported by an anaerobic (‘without air’) environment.
There are no prizes for identifying poorly made silage, whereby the variety of unpleasant odours can be appreciated from some distance, often topped off with some mould! Poorly made silage frequently provides opportunities for pathogens to jump on the band wagon and compromise health, reduce production and even be fatal.
Listeriosis, caused by the bacteria Listeria monocytogenes, can be present in silage as a result of soil or faecal contamination. These organisms often survive due to the presence of oxygen getting into the clamp/bale and clinical signs are identifiable 10 days after feeding poorly ensiled silage. These can include depression, inappetence, salivation, facial paralysis, neurological signs e.g. circling. It is also a known cause of both stillbirths/abortion in ruminants and humans (zoonotic). Avoid feeding spoiled/mouldy silage as aggressive antibiotic therapy is often required in clinical cases in which the prognosis can be poor.
A common and frustrating problem in cattle fed baled silage/haylage from ring-feeders is Bovine Iritis or ‘Silage Eye’, particularly where they tend to burrow their heads. The first signs are of clear ‘tear-like’ fluid emerging from the affected eye with a progression to blinking then a closed eyelid, the surface of the eye demonstrating a bluish white discolouration which may begin to ‘bulge’ from the surface. Listeria monocytogenes is also responsible for this disease and the same advice applies!
Botulism is an uncommon disease associated with consumption of a toxin produced by the bacteria Clostridium botulinum, this can be found in silage clamps as a result of cadavers i.e. dead birds in clamps or from pastures treated with poultry litter then used for silage. However, the clinical picture can be severe with a range from muscle weakness and neurological signs to sudden death. So, remember to clear away any ‘roadkill’ from the clamps!
The scientific evidence available for the implication of Mycotoxins such as Aflatoxin, can be contradictory. These are substances produced by moulds which can have harmful effects in ruminants including reduced voluntary food intake (VFI), reproductive disorders such as embryonic loss/abortion, and decreased production amongst other issues. Diagnosis can be complex and mycotoxin binders are available commercially.
Silage clamps still remain a key player in the ‘rehoming strategy’ for the tyre industry and are consequently responsible for cases of ‘Hardware disease’ when ingested wire/metal becomes lodged in the reticulum. Since some units have been administering magnets to cows together with those fitted inside mixer wagons, these cases have subsided comparatively to previous years.
Don’t forget that silage analysis is a fundamental cost effective tool in ration formulation, estimations of Dry Matter (DM), Energy and Protein content together with D-value amongst other parameters can be critical. So, when you are having the time of your life this year sheeting up the clamp or stacking wrapped bales, be safe in the knowledge that doing a proper job may save you time, money and optimise animal health in a few months’ time!
- 20th May 2016
