Goats are more resistant to the negative impacts of oak than other species of livestock but there are surprisingly few studies on the subject in relation to goats specifically, and those studies reach varying conclusions. Often, oak is found on both “safe” and “toxic” forage lists. Asking goat owners to weigh in on oak yields similarly inconclusive results. First, why can oaks be toxic? Primarily, a reddish-brown acid called tannin is the culprit.
Tannins give oaks their bitter flavor, and tannins in the bark help protect the tree from bacteria and fungi. In acorns, it keeps the young nuts safe from consumption (generally) until they are mature (2). Tannins (and other compounds) cause toxicity by binding with proteins and making them “inaccessible to rumen degradation.” (1) Simply put, excess tannins can negatively impact both the gastrointestinal tract and the renal system. Toxicity can be acute – the animal ingesting a large amount of oak leaves, twigs, or acorns in a short time – or chronic. Chronic toxicity is most likely to occur when goats consume enough oak to account for around 50% of their daily dry matter intake for a minimum of two weeks (3). The tannin content and thus toxicity of oak depends on several factors, including species, climate, and season. Green acorns and young buds contain more tannin than mature or old acorns or fallen leaves. Species of white oak typically have the lowest tannin concentrations while species of black oak or pin oak have the highest. Temperature and moisture affects both tannin concentration and composition – there can be many different types of tannins – read more about that on sources six and ten. One study found higher tannin concentrations in warm, dry conditions (6). It has long been a custom to soak acorns in water (called cold leaching) to rid them of the bitter flavor caused by tannins before using them for human consumption so it stands to reason wet conditions could result in lower tannin concentrations in oaks. Other tannin-containing plants include: witch hazel, sericea lespedeza, persimmons, willows, sumac, maples, cranberries, birdsfoot trefoil, and sorghum (1, 6). Even white clover flowers can produce tannins (7). Photos left to right - Domino eating sericea lespedeza (note the small white flowers on this mature plant late in the season - this is a "native" woody stemmed variety) Layla eating sumac. Rhea stretching to reach oak leaves.
Generally, goats do tolerate tannins much better than other ruminants or horses, but why? One surprising reason – spit. Studies have shown goats can develop tannin-binding salivary proteins though more research is needed to fully understand this (8).
As stated earlier, it is easy to find studies concluding oak is toxic and studies concluding oak is not toxic but the major deciding factor seems to be quantity. If a goat does have access to too much oak either in a short period of time or over a longer span, what symptoms should you look for? First, if the goat is foraging, observe. Does the goat have access to a lot of oak? Has a limb or tree fallen? Does it seem like the goat only wants to eat oak – especially fallen acorns? Many breeders observe animals becoming addicted to acorns in the fall and eating little else.
Early symptoms of oak toxicity can include: depression, anorexia, abdominal pain, constipation followed by diarrhea, an abnormal amount of discharge from the eyes, nose, and mouth, and a gaunt appearance. Later or in the case of acute toxicity, symptoms can include renal distress which might be bloody urine, frequent urination, and then decreased urine output in the case of renal failure, excessive thirst, and other symptoms like anemia, brisket edema, or even complete rumen stasis (11). Note that these are possible known symptoms – a goat may not present all or even most of these.
Again, because the symptoms of oak toxicity are similar to a host of other problems, correct diagnosis will rely heavily on observation. Unfortunately, symptoms of oak toxicity can be VERY persistent – lasting 2 to 4 weeks after initial onset, according to Goat Vet Corner.
Treatment is primarily supportive care. First, the animal must be barred from any oak sources. If
caught early enough, especially in the case of acute toxicity, activated charcoal can limit the negative consequences. Goat Medicine suggests “oral purgatives, including mineral oil and/or magnesium sulfate” in the case of known acute toxicity but cautions intravenous fluids “might be required to correct dehydration and acidosis” with this extreme treatment course (pg 562).
It is important to keep the animal hydrated, especially if it is experiencing diarrhea or urinating frequently. Offer fresh, clean water for certain and consider offering or even drenching the animal with an electrolyte solution. If anorexic, the animal must be encouraged to eat dry roughage like hay or non-tannin-
containing browse. In the case of rumen stasis or distress, a “cud tea” from a healthy goat is a wonderful way to kickstart the rumen and repopulate good gut bacteria – see sidebar. Commercial probiotics are typically only helpful with mild upset, and even then their usefulness is questioned among veterinarians. While it isn’t common, oak toxicity in goats is possible. Moderation is key to decreasing the chances of toxicity.
Experiences with Oak Toxicity in Kinder Goats
In the fall of 2019, two of my 8 month old Kinder doelings here at Hefty Goat Holler Farm had me stumped. The shiniest, fattest doeling and her equally healthy-looking but slightly taller sister had developed patty-poops for no discernible reason. Multiple fecals showed either very few parasite eggs or none, no coccidi oocysts. The other goats in the herd were fine. But it was fall and the acorns had started dropping. The goats were vacuuming them up. Our property has an abundance of oaks. About 12 acres is woods. Literally every pasture and field on our 30+ acres has at least a few oaks. After reading more on oak toxicity, I decided to remove them from any acorn source, which meant a dry lot. Initially, they had the patty-poops but still ate well. The heavier doeling was the worst – looser fecals and for about two days, she had no appetite. Both lost weight. During this time, I offered supportive care, tempting them with safe things to eat, and administered probiotics and electrolytes. I kept the pair up almost the entire month of October – about four weeks after the symptoms started, they abruptly stopped. Interestingly, their full sister Caroline did exactly the same thing the following year. This time, I was leery of acorn season and immediately penned this doeling up (with her best buddy Baby) when I suspected she’d ate too many. I tried to rule out other issues (again, no other apparent causes) and offered supportive care. She had diarrhea, was squatting but not urinating, drinking copious amounts of water (and slurping down her electrolytes) and eventually went off feed and had to be enticed to eat her hay and safe leaves. A typical protocol is to remove or limit grain when a rumen is upset, as it isn’t particularly easy to digest. I decided to remove it because her diarrhea was so severe. I clipped the hair on her rump and around her tail to keep her as clean as I could, wiping her rear end and legs down often but trying not to irritate her skin. My usually-rambunctious, silly Caroline felt miserable, and I was seriously concerned for her. To make matters, worse, she and Baby escaped the dry-lot pen for a few hours while I was gone and bee-lined for the large white oak tree in the yard. I feel like that set back her recovery but I did administer activated charcoal that day. She displayed some sort of symptoms, mainly diarrhea of varying degrees, for nearly a month. I actually wrote down “better poop!” in my planner when she hit about the four week mark and her diarrhea suddenly began firming up.
But when a goat’s rumen has been upset for so long, they must be reintroduced to their previous or new diet gradually. It was a slow process. A few times I messed up and let Caroline and Baby out into the yard for too long (I chose the yard because no goats had been grazing it and so it should have had a minimal parasite burden – remember that parasites are opportunistic and love to take advantage of a depressed immune system!) and her poops got loose again. Not as bad as before, thankfully. It was a week before I could let them graze about half the day. I gradually reintroduced grain, just a few bites at a time. It took a month to get back up to about half a pound each.
Before this ordeal, Caroline was my biggest Kinder doeling. She lost 12 pounds in a month – that is a lot of weight for a goat less than a year old. She went from excellent condition to downright boney. Thankfully, it didn’t take her too long to gain back weight. Today Caroline is my biggest, chunkiest 18 month old, and I am incredibly thankful to see her and her older sisters not only well but thriving.
I didn't get a picture at her thinnest, but there is Caroline on the left after she began recovering. Then later with her best buddy Baby, in excellent health.
Some things I wonder about after the past two years – is there a genetic component to succumbing to oak toxicity? Or any toxicity for that matter? It is proven young kids are more likely to experience negative effects from the tannins in sericea lespedeza so doesn’t it stand to reason young stock would be more likely to experience oak toxicity too? I don’t know the answers to those questions but I hope someone will do the research one day. Raising goats certainly raises a lot of questions!
Sources:
2. Ramos Jorge Tseu, Flavio Perna Junior, Roberta Ferreira Carvalho, Guilherme Acácio Sene, Cristiane Barbosa Tropaldi, Alice Helena Peres & Paulo Henrique Mazza Rodrigues (2020) Effect of tannins and monensin on feeding behaviour, feed intake, digestive parameters and microbial efficiency of nellore cows, Italian Journal of Animal Science, 19:1, 262-273, DOI: 10.1080/1828051X.2020.1729667
3. Goat Vet Corner
4. Jerónimo Eliana, Pinheiro Cristina, Lamy Elsa, Dentinho Maria Teresa, Sales-Baptista Elvira, Lopes Orlando, and Capela e Silva Fernando.
TANNINS IN RUMINANT NUTRITION: IMPACT ON ANIMAL PERFORMANCE AND QUALITY OF EDIBLE PRODUCTS.
5. P. Frutos, G. Hervás, F. J. Giráldez and A. R. Mantecón .Tannins and ruminant nutrition. Spanish Journal of Agricultural Research (2004) 2 (2), 191-202 Review.
8. https://poisonousplants.ansci.cornell.edu/toxicagents/tannin.html