Equine poisoning by coffee husk (Coffea arabica L.)

Six horses fed coast cross hay ad libitum were given access to coffee husks and excitability, restlessness, involuntary muscle tremors, chewing movements and constant tremors of the lips and tongue, excessive sweating and increased respiration and heart rates were the most evident clinical signs. Caffeine levels were measured in the plasma and urine of these horses on two occasions: immediately before the coffee husks were made available to the animals (T0) and at the time of the clinical presentation of intoxication, 56 h after the animals started to consume the husks (T56). The concentrations of caffeine in the plasma (p < 0.001) and urine (p < 0.001) of these animals were significantly greater at T56 than at T0.It was concluded that consumption of coffee husks was toxic to horses due to the high levels of caffeine present in their composition. Therefore, coffee husks pose a risk when used as bedding or as feed for horses.Brazil is the largest coffee producer in the world, and coffee grain processing generates a large amount of waste, given that close to 60% of the crude weight of the bean corresponds to the husk. The coffee (Coffea arabica) husk is rich in organic compounds and contains substances such as tannins, polyphenols and caffeine; the latter is often found in higher concentrations in the husk than in the bean [1]. Several studies have addressed reuse of the husks, especially as organic fertilizers, in tea production, caffeine extraction and the feeding of ruminants and pigs [2-6].Caffeine (C8H10N4O2) is a methylxanthine, which the most important effect is adenosine receptor antagonism [7]. Adenosine reduces spontaneous neuronal firing in multiple brain areas, and its presynaptic action inhibits neuronal release of acetylcholine, norepinephrine, dopamine, serotonin and gamma-aminobutyric acid; it produces sedation and has an anticonvulsant effect [8]. When caffeine binds to adenosine receptors, it prevents the inhibitory effects of adenosine [8], thereby