Anyone who’s fed corn silage or haylage knows that heat kills feed quality. But the extent of the losses can surprise even the most veteran dairy producer, says Brian Perkins, a dairy technical services specialist with Diamond V.
According to University of Wisconsin research, a 30°F rise in feed temperature can cost 13 megacalories of energy, or 40 lb. of milk per ton of silage. If you have a temperature rise at ensiling and a second spike at feed-out, the potential loss is 80 lb. of milk per ton. At $15/cwt. milk, that’s a loss of $12, or a third of the value of $35/ton silage. The losses come in sugars and starches in corn silage.
If your silage heats, you can also have problems with palatability and mycotoxins, with a potential milk loss of 3 lb., 4 lb. or 5 lb./cow/day, Perkins says.
Alfalfa haylage protein also degrades with heating. At 110°F for 30 days, protein digestibility degrades less than 5 percentage units. But if temperatures reach 135°F for 30 days, digestibility degrades 20 percentage units. And losses double if temperatures reach 165°F, Perkins says.
Use of infrared cameras can help pinpoint problems:
- Initial silo fill and packing is critical. Use of the camera at feed-out can tell you if you achieved proper densities across the entire pile. Most often, you’ll find higher temperatures at the sides and top, where packing is often inadequate.
- Using the camera at feed-out can also tell you if bunker face management is correct. Feeders often knock silage down off the face of bunkers once per day, letting it accumulate in piles on the feed pad to speed up total mixed ration mixing. Those piles, however, can heat quickly as they’re exposed to oxygen.
“I was blown away by the number of 115°F temps we were getting in piles knocked down for next day feeding,” Perkins says.
Perkins took samples of the feed and tested for pH, mold, yeast and Bacillus organisms. All four jumped dramatically when feed samples were left overnight on the floor of the bunker (see table). And this occurred in Vermont in November.
A better approach, Perkins says, is to knock down silage the day of feeding, reducing the time that feed is exposed to air. He also recommends removing at least 12" of silage in summer and 6" in winter.
- Silage stored in bags tends to cool faster because there is less thermal mass. But infrared cameras can be used to detect hot spots, often caused by holes. “The infrared pictures show that pinpricks in bags will cause heating to a diameter of 12",” Perkins says.
- If you’re buying hay, the infrared camera can be used to scan bales to see if excess heating has occurred during storage or transport. “Damage to hay quality starts at about 120°F, and fire danger increases rapidly above about 140°F,” Perkins says. If heat damage is occurring, loads can be rejected for being out of condition.
- June/July 2008