The not-so-favorite things in forage
|By John Goeser|
The author is the director of nutrition research and innovation with Rock River Lab Inc, and adjunct assistant professor, University of Wisconsin-Madison’s Dairy Science Department.
The 2016 crop year was interesting from the East to West. Forage ash, some of which is soil contamination, and anti-nutrition factors (for example, mold, yeast, mycotoxins, and negative bacteria) appear to be of rising concern as producers begin to feed the year’s harvest.
Continued drought conditions in the West and an unexpected drought through much of the Northeast have led to unexpectedly high ash levels in forages. Corn silage ash contents have approached or exceeded 7 percent, where a typical average would be 3 to 4 percent of dry matter (DM). Fresh clipped alfalfa samples, in some cases, contained 10 to 12 percent ash without having been mowed, raked, merged, or handled. This has conjured up many questions among consultants.
Ash robs forage of energy value by diluting out other nutrients and contributing zero to feed value. Further, added ash can bring greater mold and yeast counts as these are soil-born organisms. The average ash content for U.S. hay and haylage has jumped by nearly an entire percentage unit over the past five years. Within the Midwest, this trend has been more substantial.
High mold counts
Soggy conditions in the Midwest through the corn silage and high-moisture corn harvest season brought added challenges in 2016. Prior to the wet fall start, plant pathologists were warning about stalk and ear rots showing up as early as June or July. For many, the wet harvest conditions along with heavier fungal pressure have contributed to the feed hygiene challenges mentioned above.
Mold counts for Midwestern corn and corn silage this year have trended around 100,000 colony forming units per gram (cfu/g), and corn silage samples trended from 10,000 up to 100,000 cfu/g at harvest, confirming greater mold prevalence. For interpretation purposes, at 100,000 cfu/g, we typically begin to consider this crop 10 percent deteriorated, and as counts reach 1,000,000, we consider the feed to be 100 percent deteriorated. From October to mid-November, nearly 20 percent of all samples analyzed for mold were beyond the 10 percent deterioration threshold.
Ash and field-born molds are largely a derivative of pre-ensiling or storing challenges. Storage issues may exist beyond growing and harvest conditions. These issues can also yield hygiene trials and may be important to consider when identifying the root of poor animal performance or feed-driven sickness.
In addition to these field-born issues, many producers are also experiencing bird, raccoon, and rodent concerns during feed storage and feedout. With rodent damage also comes potential bacterial infestation. Veterinary and forage analysis laboratories can help identify challenging enterobacteria (bad bacteria) loads in forage. With rodent damage to storage bags, bunkers, and piles, the problem is twofold. These animals can carry and harbor negative bacteria such as Salmonella spp. and inoculate the forage with these toxic bugs. Plus, rodent damage will also expose stable feed to oxygen, allowing yeast and mold to grow and exacerbating hygiene and stability challenges.
Rodent challenges and their effects on animal health are either more impactful or more prevalent in 2016 based on frequent, recent conversations with consultants and on-farm observations. At one dairy, for example, raccoons dug holes through both bunker silo covers and silage bags stored on gravel to access corn silage.
The dairy has partially controlled the problem with a low-lined electric fence around the bunker; however, one bag was substantially compromised. The hole in the bag allowed air to infiltrate and silage deteriorated. The dairy attempted to discard visibly deteriorated feed; however, when feeding this bag, dairy cattle performance dropped substantially. The feed hygiene challenge (mycotoxin, yeast, or bacteria) was not identified specifically, but the cows began to recover after moving to a new silage source.
On another example dairy, rats had infiltrated the feed center, creating holes in both alfalfa and corn silage bags. During feedout, dairy cattle began to show variable digestion, inconsistent manure, and several animals were lost as a result. In this case, the TMR was sampled and Clostridium perfringens was identified along with yeast, mold, and mycotoxins at concerning levels. To make matters worse, the high-moisture corn digestibility showcased poor quality due to low moisture levels (25 percent moisture). This likely led to excessive starch bypassing the rumen and created a favorable environment within the lower digestive tract for negative bacterial growth.
Healthy dairy cattle are constantly barraged with pathogens and can typically fight them off. However, when multiple insults are compounded, in this case mycotoxins and poor starch digestion, clinical signs begin to show up.
Ash content along with other negative microbial feed issues seem to be a growing challenge during these times when dairy margins are tight. Realize that not one of these anti-nutrition factors is going to be the sole cause of depressed performance or clinical symptoms, but rather they interact and combine to challenge cattle health. The trends outlined here, along with the two case studies, can help your farm proactively investigate such situations to avoid these diminishing outcomes.
If ash content is a concern for your farm, consult with your agronomist, equipment dealer, and nutritionist as to how to avoid soil contamination next year. If rodents or birds and bacterial challenges are a concern with your farm, work with pest control agents to eradicate or control the pests first. Next, consult with your nutrition and veterinary advisers as to what impact the harmful bacteria may be having, but only in the context of and along with other anti-nutritional factors that may also be acting as contributors.
This article appeared in the January 2017 issue of Hay & Forage Grower on page 19.
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