The effect of the control of endo- and ectoparasites on weight gains in crossbred cattle (Bos taurus taurus x Bos taurus indicus) in the central region of Brazil.

Endo- and ectoparasite infections are among the most important causes of disease and production losses in beef cattle in tropical and subtropical regions. Nevertheless, most treatments are given without epidemiological information and without evaluating their effect on the development of the animals. In this work we present the results of a study of the effect of treatments against endo- and ectoparasites in crossbred steers, during three cycles of field trials in the Brazilian Cerrado region. Three anthelmintic treatments during the winter and three acaricidal treatments during the spring/summer provided significant additional weight gain in three and two experimental trials, respectively. In the trials, steers treated for gastrointestinal nematodes gained a mean of 33 kg more and those treated for ectoparasites had additional mean weight gains of 13 kg compared with non-treated steers.

Effect of stocking rates and anthelminthic treatments on weight gains in weaned Nellore cattle on improved pasture in the Brazilian cerrado.

The results are presented of 6 years of field trials with weaned Nellore cattle on improved pasture in the midwest of Brazil, using 2 stocking rates and 4 anthelminthic treatment regimes. The most profitable regime included treatments in May, June and September, which yielded an additional 41 and 42 kg of liveweight on the 2 stocking rates. No significant additional gains were obtained by treating during the rainy season, or by treating animals more than 24 months of age. The higher stocking rate (1.8 AU/ha) proved excessive on the improved pasture which deteriorated during the 6 year experimental period, yielding suboptimal liveweight gains.

Efficacy of doramectin against field nematode infections of cattle in Latin America.

Two studies were conducted, one in Argentina and one in Brazil, to evaluate the therapeutic efficacy of doramectin administered subcutaneously at a dose rate of 200 micrograms kg-1 (1 ml per 50 kg) to cattle harboring mixed field infections of gastrointestinal nematodes. In each trial, 20 heifers were randomly allocated to a control or treated group of ten animals each, on the basis of fecal egg counts. Animals in the treated and control groups received an injection of doramectin or saline in the lateral midline of the neck. From 14 to 18 days post-treatment an equal number of animals from each group were slaughtered every day and the worm burdens of doramectin-treated animals were compared with those of non-treated controls. The efficacy of doramectin was at least 99.9% against adult stages of Ostertagia ostertagi, Haemonchus placei, Haemonchus contortus, Haemonchus similis, Trichostrongylus axei, Cooperia pectinata, Cooperia spatulata, Cooperia surnabada (Cooperia mcmasteri), Oesophagostomum radiatum and Dictyocaulus viviparus. Efficacy against Nematodirus helvetianus was 97.9% while efficacy against Trichuris discolor was 92.3%. Activity against inhibited larval forms of Ostertagia ostertagi, H. placei, Oesophagostomum radiatum, and Trichostrongylus axei, was at least 99.9%.

Programa de controle estratégico da verminose em gado de corte no Brasil / A programme for the strategic control of helminths on beef cattle in Brazil

A importância da verminose, como fator negativo para o desempenho da bovinocultura de corte, é reconhecida atualmente. Apesar do grande número de anti-helmínticos existentes no mercado, verificam-se ainda resultados decepcionantes. A finalidade deste trabalho é apresentar um modelo para elaboraçäo de um programa nacional de tratamentos estratégicos, baseado em dados epidemiológicos dos helmintos e análise das diferentes condiçöes climáticas do Brasil

Helminth parasites of beef cattle in the cerrado region of Brazil.

The results are presented of a ten-year research programme on the helminth parasites of beef cattle raised in the extensive cerrado region of central-east Brazil. The most important helminths are Cooperia spp., Haemonchus spp. (80% H. similis), Trichostrongylus spp. and Oesophagostomum radiatum. Both production and infection are dominated by the alternation of rainy and dry seasons. Attempts to develop and implement control measures and their limitations are discussed.