Miíases Umbilicais em Bezerros Nelore Recém-Nascidos: Predisposição de Dois Cruzamentos Raciais Criados no Sistema de Manejo Voisin no Rio de Janeiro e Avaliação de Medidas Profiláticas em Criação Extensiva no Pantanal Sul-Mato-Grossense. / Umbilical Myiasis in Nelore Newborn Calves: Predisposition of Two Racial Crossings Raised in a Voisin System in Rio de Janeiro and Evaluation of Prophylactic Measures in Extensive Cattle Raising in the Pantanal Sul-Mato-Grossense.

Marcus Sandes Pires

The research was done in two distinct properties of beef cattle raising. The first part of the experiment was executed in Santo Antônio Farm, located in Miguel Pereira city, Rio de Janeiro State, with the objective of evaluating the susceptibility and the prevalence of umbilical myiasis in the newborn calves, resultant of the crossings between Brahma pure breed bulls and 5/8 Canchim cows x 3/8 Nelore and the crossings between Nelore pure breed bulls and 5/8 Canchim/Nelore cows x 3/8 Nelore. A descriptive study with observation of the prevalence of umbilical myiasis was carried out after calves birth, in accordance with the racial origins and gender of these animals, from august to november 2006. Each matrices group, composed of 130 females, among cows, heifers, and 10 bulls of same racial origin (Nelore and Brahman), placed in 40 poles, having each one of these, two to three hectares, using the Voisin rotation system. The animals remained approximately 24 hours in each pole, after that, they had to avoid the pasture for one month. the second part of the experiment was carried out in Alegria Farm, located in Corumbá city, State of Mato Grosso do Sul, with the objective of evaluating the efficacy of medicines, to do so, were used four separated pastures of 850 hectares, containing 350 cows, approximately, and the newborn calves of these groups, were treated with the medication chosen for each of the separated pastures. The medicines used were: doramectin 200 μg/kg l.w., ivermectin 200 μg/kg l.w., ivermectin long action 200 μg/kg l.w., all, subcutaneously injected and solution of DDVP (2.2-dichlor-vinyl-dimethyl-phosphat or dichlorvos) plus triclorfon, with topic application in the umbilical area. After the elective application of the medicines in each group, it was possible to detect the prevalence of umbilical myiasis in the animals. The monitoring of the calves in the two properties was done until one month after the birth, for new evaluation of possible occurrences of umbilical myiasis. In the first part of the experiment, from 152 newborn calves41,33% of umbilical myiasis, and 77, derived from the crossing between Brahman x 5/8 Canchim/Nelore, 75 were derived from the crossing between Nelore x 5/8 Canchim/Nelore with a prevalence of 54,55%, of umbilical myiasis, not being evidenced significant difference (p>0.05). From the total of umbilical myiasis observed, 52,02% occurred in male and 47,95% in females. In the second experimental part, from 613 calves preventively treated, 24 cases of umbilical myiasis were detected, mostly in the period of heavier rains and higher temperatures. There was a significant difference (p<0.05) in the use of doramectin, ivermectin, and ivermectin long action, subcutaneously application in relation to the topic solution of DDVP + triclorfon like preventive medication to the umbilical myiasi. There was no statistical difference (p>0.05) among the avermectins used in the study, in the prevention of umbilical myiasis.

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