| Sumario: |
We Report in this paper on the in vivo resistance of bovine animals to the venom of the elapid Micrttrus nigrocinctas, the most prevalent coral snake in Costa Rica (TAYLOR et al., 1974). Apreliminary report has been published elsewhere (Bolaños et al., 1973).
The following six types of experiments were performed: (1) four Red Polled XBrahman cows (350-380 kg) were each bitten once by different specimens of M. nigrocinctus, measuring 0.80-1.0 m in length. The bites were, respectively, on the ventral surface of the tongue, dorsal surface of the tongue, nostrils and one teat. In each case we saw the fang marks and the contraction of the snakes venom glands. The fact that the snakes had not been milked and that they held on during the bite for a considerable length of time assured us that venoms had been injected. (2) Solutions of dried venom from the Instituto Clodomiro Picado, having a mouse LD se of 0.39 mg per kg body weight (Bolaños, 1972) were injected into the same cows 6 days after the previous experiment. Three of the animals were given 5, 10 and 20 mg of venom intravenously, and the fourth was given 5 mg subcutaneously into the ventral portion of the tongue. (3) Ten mg of the venom was injected into two Holstein calves (40 kg each). One cow received the venom intravenously and the other subcutaneously, in the ventral surface of the tongue. (4) Fifteen mg of the venom were injected intramuscularly in the neck of four Angus XJersey cows, average weight 235 kg.
(5) One horse weighing 250 kg was injected intramuscularly with 20 mg of the venom and served as a control. (6) Neutralization tests were performed on serum samples from the cows obtained prior to each venom injection or bite (Bolaños et al., 1974).
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