Synthetic pesticides and herbicides pose a number of problems, so raw milk farms are advised to minimize their exposure for soils, crops, water, feeds, and livestock. While there are numerous synthetic pesticides and herbicides of concern used in conventional agriculture, glyphosate-based herbicides (often sold under the brand name Roundup) are by far the most widely used. Glyphosate residues are slow to degrade and can accumulate in the soil, manure, water, and feed.
Common Feed Sources of Glyphosate on the Farm
Cows and goats should ideally obtain most of their feed from pasture during the growing season. When purchasing feed, beware that alfalfa, corn, wheat, canola, and soybean are crops most likely to be engineered to tolerate glyphosate herbicide. Because of these and other genetically-engineered (GMO) crops, global usage of glyphosate has proliferated to billions of pounds annually[i]. Besides use on herbicide-tolerant crops, glyphosate is also often sprayed on many small grains and other crops as a desiccant applied shortly before harvest. When sprayed on wheat, oats, legumes, sugar cane, and barley, glyphosate residues will then be present in the grain and other plant parts.[ii]
Harms of Glyphosate Exposure
Livestock exposed to glyphosate in feed or as bedding are more likely to have serious animal health disorders causing loss of production.[iii] Glyphosate is a strong mineral chelator that binds tightly to essential minerals to render them non-functional physiologically. Exposure of crops and livestock to glyphosate can intensify mineral deficiencies of Ca, Cu, Co, Fe, Mg, Mn, Ni, and Zn.
Besides interfering with mineral nutrition, glyphosate has antibiotic properties that disrupt the gut microbiome. An in-vitro study looking at potential impacts of glyphosate found that some pathogenic bacteria such as Salmonella and Clostridium botulinum are “highly resistant to glyphosate. However, most of beneficial bacteria as Enterococcus faecalis, Enterococcus faecium, Bacillus badius, Bifidobacterium adolescentis and Lactobacillus spp. were found to be moderate to highly susceptible.”[iv] This raises concerns about the potential for glyphosate to kill beneficial microorganisms while allowing pathogenic bacteria to proliferate.
Weeds Can Be Beneficial in Pastures
On the farm, pasture and forage feed sources for ruminants can be produced without pesticides through intentional management practices. Beneficial pastures are composed of a mix of diverse species including nitrogen-fixing legumes. Pastures and hay fields do not need to be perfectly weed-free for feeding livestock. In fact, some “weed” species are palatable and can serve as acceptable feed. In general, weeds can be controlled by good rotational grazing management and by sometimes clipping pastures immediately after grazing. Beware that a few weed types, such as pokeweed, hemlock, and nightshade, are poisonous.
Other Potential Sources of Glyphosate on the Farm
It is not enough to just avoid using glyphosate and synthetic pesticides on your own farm. To minimize exposure to glyphosate, dairy farmers need to be aware of potential sources such as well water, imported feeds, bedding materials, drift from neighboring farms, and soil fertility inputs. Ideally, feeds and bedding materials for the dairy herd should be produced on-farm. Feeds and bedding materials obtained from common commercial sources are generally suspect for glyphosate contamination.[ii]
Grain Supplementation Can Be Important for Dairy Herds
Although milk can be produced from entirely grass-fed animals through high quality forages, it can be challenging to supply enough energy to dairy animals without feeding some grain in order to maintain good health and body condition. For small dairy farms, it may be more economical to purchase grains rather than becoming grain producers. Feed sources that commonly have glyphosate residue include alfalfa, canola, corn grain or silage, soybean, wheat, oats, barley, sugar beets, cottonseed meal, sugar cane, molasses, and distillers grain.
Purchasing pesticide-free, non-GMO, and/or certified organic feeds is one approach to minimizing exposure to pesticides and genetically engineered feed crops. Certified organic feeds are typically more expensive; however, farmers can search for feed sources from reputable producers who farm with ecological practices, even if they are not certified organic. Questionable feeds and materials can be tested for the presence of glyphosate, such as with the testing supplies available from Health Research Institute in Fairfield, Iowa.
Reducing Glyphosate Exposure on the Farm
It is recommended for farmers to look holistically at all aspects of their environment for ways to reduce exposure to glyphosate and pesticides. Bedding materials such as soybean hulls and straw from small grain crops may also be contaminated with glyphosate or pesticides. Additionally, poultry and other livestock manures, such as those imported from conventional farms to build soil fertility, often contain glyphosate residues.[v]
Raw milk customers often ask raw milk dairy farmers pointed questions about production practices. Many customers are discriminating in food quality and purposely seek out farms that avoid the use of GMO’s and free of pesticides and herbicides. Fortunately for dairies, pasture and forages can be relatively easy to manage without the use of synthetic pesticides or herbicides. Farms that implement good production practices can answer such customer questions directly. They can honestly report on how they use ecological farming practices to manage pests without using synthetic pesticides.
References
[i] Wilson, C.L. and D.M. Huber. (Ed.) 2021. Synthetic Pesticide Use in Africa, Impact on People, Animals, and the Environment. Chapter 2: Glyphosate’s Impact on Humans, Animals, and the Environment. CRC Press, Taylor & Francis Group. Boca Raton, London, New York. 2021 https://www.taylorfrancis.com/books/edit/10.1201/9781003007036/synthetic-pesticide-use-africa-charles-wilson-huber
[ii] Jingwen Xu, Shayna Smith, Gordon Smith, Weiqun Wang, Yonghui Li. Glyphosate contamination in grains and foods: An overview. Food Control, Volume 106 (2019) https://www.sciencedirect.com/science/article/abs/pii/S0956713519302919
[iii] Wilson, C.L. and D.M. Huber. (Ed.) 2021. Synthetic Pesticide Use in Africa, Impact on People, Animals, and the Environment. Chapter 8: Animal Health Issues with Increased Risk from Exposure to Glyphosate-Based Herbicides. Chapter 9: Agricultural Pesticides Threats to Animal Production and Sustainability. CRC Press, Taylor & Francis Group. Boca Raton, London, New York. https://www.taylorfrancis.com/books/edit/10.1201/9781003007036/synthetic-pesticide-use-africa-charles-wilson-huber
[iv] Shehata AA, Schrödl W, Aldin AA, Hafez HM, Krüger M. The effect of glyphosate on potential pathogens and beneficial members of poultry microbiota in vitro. Curr Microbiol. 2013 Apr;66(4):350-8. doi: 10.1007/s00284-012-0277-2. Epub 2012 Dec 9. PMID: 23224412. https://pubmed.ncbi.nlm.nih.gov/23224412/
[v] Harle, D., McNeill, M. J., Huber, D. M., Maney, M., Cano, R. J., & Carlin, M. (2024). Saga of Soggy Sauerkraut. HortScience, 59(11), 1618–1628. https://doi.org/10.21273/HORTSCI18041-24