Harvesting and ensiling good alfalfa haylage can be challenging. The high protein and low carbohydrate content can lead to less than optimal fermentation if conditions aren't right.
Most dairies today are ensiling forage in bags or bunkers, which are more economical and practical than oxygen limiting upright silos, especially on larger dairies. But a recent study from the U.S. Dairy Forage Research Center shows that those big blue structures actually make better alfalfa haylage. So if you own a Harvestore, but you're filling your bunkers instead, you might want to reconsider.
The forage researchers conducted what I consider a very well designed study to look at the differences between storage systems. First cutting alfalfa was harvested over a two day period to produce re-growth of similar maturity. The second cutting was then used in the study. The alfalfa was chopped at a theoretical length of about 1.2 inches and no additives were used. The alfalfa used in the bag and bunker were chopped the first day of harvest and that used in the Harvestore chopped the next day, to achieve target dry matters of 30-40% and 45-55%, respectively. Drying conditions were good and no rainfall was recorded during harvest.
All haylage was good quality, averaging 22.4% protein, 32.7% ADF and 41.3% NDF. The dry matter percent of the bag, bunker and Harvestore haylages were 40.7%, 37.1% and 47.6%, respectively. Alfalfa ensiled in the Harvestore was significantly lower in ash, pH, ammonia-N, and acetate. It was significantly higher in lactate and non fiber carbohydrate (NFC) and had greater NDF digestibility than the bag or bunker haylage. These measurements indicate that the fermentation in the Harvestore was more effective, which resulted in better preservation of the protein and the energy in the haylage. The ammonia in the Harvestore haylage was half that of the bunker and bag levels. This indicates less protein breakdown during fermentation. Butyric acid was found in the bunker haylage, but not in the bag or Harvestore. Butyric acid can indicate clostridial fermentation.
The haylages were included in diets fed to 36 cows for 12 weeks with no differences in milk production or composition, although cows fed the Harvestore haylage ate significantly more dry matter. Bags and bunkers certainly have their advantages, but I think these fermentation results are significant enough to consider making full use of your Harvestore if you own one.
Reference: Broderick and Muck, Journal of Dairy Science, March 2009.
--Rick Lundquist is an independent nutrition and management consultant based in Duluth, Minn. You can contact him at firstname.lastname@example.org.
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