Silage Advisory Centre

Keeping oxygen from entering baled silage is critical in preventing undesirable bacteria and mould to multiply up to levels that are potentially harmful to livestock.

“There are two simple ways to reduce oxygen penetration into silage bales,” says Rhun Fychan, research scientist at IBERS, Aberystwyth University, on behalf of the Silage Advisory Centre.  “That is increasing the number of layers of bale-wrap used and reducing wildlife damage on baled silage stacks.”

“Using six layers of silage wrap has been shown to reduce surface mould on bales. The higher ME and sugar values of the silage makes it cost effective and should reflect in improved livestock production.”

Additional layers of wrap also provide added protection against physical damage during bale production, transportation and storage. “A study conducted at IBERS looking at film damage when wrapping 2^ndcut bales directly on the field showed 8% of the 4 layered bales damaged from tipping the bales off the wrapper onto grass stubble, while less than 1% of the 6 layer bales were damaged,” says Rhun Fychan. “This stubble damage can cause the oxygen barrier that is so crucial for silage preservation to fail within seconds!”

Once stacked, the bales are still vulnerable to damage – especially by birds. Two IBERS studies have evaluated large, unprotected stacks of 2^ndcut bales.

Study 1 (233 silage bales stacked three layers high) – “When opened bales protected within the stack had 0.4% visible surface mould compared to 2.6% on exposed bales.  Much of this difference was due to wildlife damaging the bale-wrap allowing oxygen to enter. The protected bales also had much lower listeria counts than the exposed outer bales. Visible surface mould at these levels might not sound alarm bells, but accompanied with high listeria counts – they would, without doubt, be harmful to livestock.”

Study 2 (stack of 288 bales assessed for silage feeding quality) – “In this study, the exposed bales had far lower predicted ME compared to the protected bales (9.7 v 10.3 mj/kg DM), resulting in lower animal production values.

“Is it acceptable that the same grass at ensiling ends up capable of producing 1.8 litres of milk per day less depending on where it is stored in the stack?”

Source: IBERS, Aberystwyth University                     * NIR predictions

So, unless you have very large stacks of bales, your exposed bales always outnumber protected bales. With these potential risks to livestock health and production, the use of 6 layers of bale-wrap and a net to protect silage bales will always be cost-effective and result in better silage quality.