Adviser warns against three silage inoculant claims

An independent silage specialist has sparked industry debate by raising concern over information given to farmers about silage additives, which he claims are ruining forages.

Dr Dave Davies of Silage Solutions has voiced frustration at what he says are three blunders adding to feed costs caused by clamp losses every year.

“A farmer does not necessarily know how much better a silage could have fed and how much milk from forage has fallen,” he says.

See also: Advice on sampling fresh grass for this season’s silage

“The challenge is there are many variables in forage production and very little control and comparison.”

Dave claims the three main errors are:

1. Overuse of additives containing heterofermentative (HE) bacteria
2. Believing silage can be treated to help manage ketosis
3. Telling farmers that lactic acid in silage is bad for cows.

Industry response

Dave has toured his message across the UK and mainland Europe, meeting criticism from some vendors of HE and homofermentative/heterofermentative (HO/HE) products who have told Farmers Weekly their product claims are backed up by data.

Some suppliers maintain that HO/HE inoculants are suitable for use in grass silages as low as 25% dry matter (DM), clashing with Dave’s recommendation of 30% DM (see “Points of contention in detail”).

Two sales teams say the losses suffered through fermentation at feed-out and at the clamp face are worth insuring against with a HO/HE additive.

Dave maintains that, in many situations, good consolidation, tight sealing, and good management of the clamp face at feed-out can minimise aerobic spoilage, negating the need for HO/HE or HE inoculants.

Points of contention in detail

1. Use of additives in wetter silage

Silage expert Dr Dave Davies says one of the key distinctions to draw is whether a silage additive contains homofermentative (HO) or heterofermentative (HE) bacteria (see “What’s in your silage inoculant?”).

He claims HE additives are not suitable for silages below 30% dry matter (DM) and HO inoculants should only be used for these.

He also points out that the UK’s temperate climate offers a different challenge for inoculants that have been developed in mainland Europe and North America. Therefore, trial data from abroad have limited relevance here.

DM data from Wageningen University shows silage in most European countries averages 34-40% DM. In the UK, average DM is 32%, he says.

Dry matter matters 

The extra water in lower DM silage dilutes acids produced by bacteria in the forage, says Dave.

This means it takes longer for the acid to preserve the forage, leading to more sugar and protein degradation.

He explains that lactic acid produced by HO inoculants is seven times stronger than acetic acid and achieves a relatively fast fermentation.

He adds that HO additives formulated with additions such as potassium sorbate or sodium benzoate will work without the risks associated with an HE inoculant, of slow fermentation, acetic acid production and more DM losses. 

2. Role of HE additives in managing ketosis

Another mistake made when buying HE additives is thinking they will create extra energy for the cow, solving negative energy balance and ketosis issues, Dave claims.

“This goes against basic laws of thermodynamics,” he says.

“Energy cannot be created or destroyed. The energy created in propylene glycol form [produced as a by-product of HE fermentation] is far outweighed by the loss in energy overall, so there is less feed value in the clamp.

Research by Limin Kung Junior, animal sciences professor at the University of Delaware, and Richard E Muck, professor in forage preservation at the University of Wisconsin-Madison, found in a 25kg DM ration, with 50% forage, a silage with 1% propylene glycol would provide 125g propylene glycol to the cow. 

Dave points out this is much lower than the 250-400g bolus treatment of propylene glycol that is commonly recommended for ketosis.

3. Role of lactic acid

Dave says he is alarmed some people are saying that lactic acid is bad for cows when it is an essential acid in preserving forage in silage clamps.

Lactic acid reduces enterobacteria and clostridia, which is essential in wet silages, where aerobic spoilage is much less of an issue.

Current industry guidelines are that the ratio of lactic acid to acetic acid after fermentation should be at least 3:1, and 5:1 is even better.

The issue with using HE bacteria in wet silages and the extra acetic acid they produce (often 40-60% more) is that they can reduce silage DM by 4-5%, according to research calculations, he adds.

This decreases intake potential and leads to higher feed costs because less milk is produced from forage.

Lower intake

An Animal Feed Science and Technology research paper found that every 1g/kg DM increase in acetic acid above 17.3g/kg reduced DM intake by 0.48kg/day in a 600kg cow.

Dave says he has seen farms with maize silage treated by HE products ruined by acetic acid.

The fermentation on Farm 1 (see “Farm silage comparison”) that used an HO/HE inoculant resulted in an acetic acid level so high it would halve DM intakes because of reduced palatability.

By comparison, Farm 2 used an HO additive and produced a better silage, despite it being wetter.