How to Make High-Quality Grass Silage
Grass silage is pickled pasture, preserved through the conversion of its sugars into lactic acid by bacteria.
On average the cows fed high-quality silage produced 0.22kgMS/cow/day more than cows fed low-quality pasture silage. At a $5.50 milksolids payout this equates to an increased return of $1.21/cow/day for the high-quality silage. The additional return from feeding high-quality silage to a 300-cow herd for 30 days would be $10,890.
The principles of making high quality pasture silage can be summarised in the following steps:
Harvest at the correct time. The feed value of the ryegrass plant drops rapidly as it enters its reproductive phase. Harvest pasture silage no later than 35-40 days after the last grazing or when a maximum of 10% of the ryegrass seed heads have emerged.
Wilt to at least 28% drymatter. Wilting concentrates the plant sugars and reduces the risk of nutrients being lost from the silage stack as leachate.
Make sure there is no soil in the silage. Soil reduces the feed value of silage. To keep it out of your silage, harvest during dry weather, ensure the cutter bar does not skim the ground, and watch that the stack tractor does not carry soil on its tyres.
For pit silage, chop to 5-7cm. Chopping allows for good consolidation, reducing storage and feed-out losses. It also releases plant sugars which are converted to acid by fermentation bacteria.
Add a quality silage inoculant at harvest time. Pasture silage has a high buffering capacity which means a lot of acid must be produced to drop the pH, however it has a limited amount of sugar for acid-producing bacteria to ferment. Quality silage inoculants contain the right strains of lactic acid-producing bacteria to ensure the sugar in pasture is efficiently converted to acid. They can help to reduce fermentation losses while at the same time improving silage quality.
A recent inoculant performance study1 compared the performance of five commercially available silage inoculants (and an untreated control) applied to six different New Zealand pasture samples.
Pioneer brand 1174 gave a faster pH drop when compared to the untreated control. Other inoculant brands did not differ from the untreated control.
1174 inoculated silage had the best fermentation acid profile (more lactic and less acetic acid) and lower ammonia nitrogen levels indicating that less protein had broken down into forms animals cannot use.
While this study shows that inoculants can effectively improve silage quality, it is important to recognise that some products had no positive impact on pasture silage fermentation quality.
The authors concluded that farmers should look for two things when selecting inoculants: published trials conducted according to scientific protocols, and guaranteed bacterial counts on their labels.
1Kleinmans et al, 2011. ‘Using silage inoculants to improve the quality of pasture and maize silage in New Zealand’. Proceedings of the New Zealand Grassland Association
73:75-80.
