California dairy producers must utilize and maintain silage best management practices to ensure good-quality feed as well as to comply with air- and water-quality regulations.

That’s the message from Jennifer Heguy, University of California dairy farm advisor for Stanislaus and San Joaquin counties, and Noelia Silva-del-Rio, her Tulare County counterpart. Heguy presented feed management survey results – and how the silage-making process will be affected by new air and water regulations – at the California Alfalfa & Forage Symposium in December.

About 17% of dairy producers contacted in the two farm advisors’ three counties completed 120 surveys in 2009. Herds surveyed ranged from 160 lactating cows to 6,600, with a median herd size of 950 milking cows. Results showed that 85% of respondents stored silage in piles, and 75% stored it on concrete. A total of 54% said they used bacterial inoculants.

Top-layer spoilage ranged from less than 3” to 20”, with 25% of respondents reporting less than 3”. More than 50% of surveyed producers lost 3” to less than 6” of the top layer to spoilage.

“We had some reporting up to 20” of spoilage on a pile, and 60% of dairies reported that they pitched spoiled forage,” Heguy said.

About 42% of surveyed dairies said they removed the entire width of their silage faces daily, and 58% removed half or less each day.

“Dry matter was determined at least once a month on 52% of dairies. This task was usually delegated to an outside nutrition consultant (86.6% of the time). Twenty-five percent reported that they suspected mycotoxins in their silage in 2008 and, of those dairies, 70% discarded the moldy feed from the pile.”

Feed quality isn’t the only quality producers need to be concerned over. Air- and water-quality regulations, some of which were passed just a couple of months ago, will require additional management and documentation, Heguy said.

The Central Valley Regional Water Quality Control Board, Region 5, adopted waste discharge requirements for dairies located from the Oregon border to southern Kern County.

“All of the dairies in the region are regulated the same, no matter the size of the operation. No more than 1.4 times the amount of nitrogen removed in a field can be applied. And that’s on a crop-per-field-per-year basis. So, in order to comply with that 1.4 number, producers have to document the total weight of nutrients removed from fields where manure is applied.

“This is going to be tricky because dry matter varies greatly even within a field. There is a detailed protocol for sampling silage, but field observations show that it wasn’t really being followed, and that leaves the door open for both under- and over-estimations of what is being removed.”

Heguy and colleagues conducted a quick study to see if there were differences in calculating dry matter removal. They compared, on a corn silage field on each of three dairies, single sample, sequential composite samples (the average of every truckload within an hour) and interval samples (trucks sampled every hour or every 10 trucks throughout the day).

“We found that taking a single sample of forage to estimate dry matter removal of an entire field yielded results that varied greatly from the actual dry matter removed. On one of the cooperator dairies, using any one individual sample to estimate dry matter removal could underestimate harvested forage by 21.5% or overestimate forage removal by 20.4%.”

Sequential composites were less varied, and interval samples, the least varied, she said.

“We are hoping, with these results, to convince producers that they need to be more conscious when they are sampling their fields. Just taking one sample could be detrimental to the quality of the results reported.”

Air-quality regulations at issue were passed last October. The San Joaquin Valley Air Pollution Control District amended its Rule 4570 to include 500+-cow dairies and will affect 94% of dairies in its district, which spans from San Joaquin County to Kern County. That region accounts for 87% of California milk production, Heguy said.

The air district’s mitigation measures include that silage be covered within 72 hours of forage delivery; that silage density benchmarks be reached, depending on the kind of silage being put up; that silage is harvested at the correct moisture and theoretical length of chop; and that silage face exposure is managed.

Heguy hopes the surveys will show producers where they are in silage management – and where improvements can be made to ensure feed quality as well as to meet state regulations.