While smoke-damaged hay loses some of its green color and may appear light yellow, the discoloration should not be the primary concern for buyers or dairy farmers feeding the hay, according to University of California – Davis extension dairy nutrition and forage specialists.
“Hay color really has a tenuous relationship with quality,” said Daniel Putnam, UC-Davis extension agronomist and forage specialist. “Other things [leaf-stem ratio, fiber content, weeds, digestibility and physical condition] are much more important.”
When it comes to hay quality, discoloration can be deceiving.
In studies at UC-Davis, hay discoloration caused by extreme sun bleaching had no impact on standard hay test variables, such as total digestible nutrients (TDN), relative feed value (RFV), relative feed quality (RFQ), crude protein (CP), acid detergent fiber (ADF) or neutral detergent fiber (NDF). Yellowing of alfalfa on the top of windrows is very common, resulting in a mix between yellow and green colored hay in normal alfalfa bales, but does not have a significant effect on normal quality indicators.
In contrast, discoloration due to moisture caused by light rain or heavy dew can leach out carbohydrates and protein, creating hay with reduced nutritional quality. Discoloration due to excess moisture during baling and subsequent mold or excess heating is also a real problem.
“But for smoke damage, the concern is much more the deposits of ash, raising overall ash levels in the hay,” said Peter Robinson, extension dairy nutrition and management specialist. “As ash does not contribute to the energy value of the crop, every percentage increase in ash content results in a decrease in something else of nutritional value, such as protein or carbohydrates.”
Smoke may also affect hay flavor, resulting is decreased cow intakes.
“Unlike hay color, animals do react to olfactory signals, and this might be an issue for palatability and acceptance for some animals,” Putnam said.
Cow rejection of smoke-damaged hay will be a bigger problem when feeding whole bales, while feeding hay in total mixed rations (TMRs) is less likely to be a problem, Robinson added. 
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Dave Natzke
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