trabalho completo - 52ª Reunião Anual da Sociedade Brasileira de

52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Avaliação de bovinos da raça Senepol quanto à infestação por Rhipicephalus microplus e Dermatobia hominis
Vânia Mirele Ferreira Carrijo1, Glayk Humberto Vilela Barbosa1, Cecília José Veríssimo2, Lenira El Faro
Zadra3, Anibal Eugênio Vercesi Filho2, Cláudia Cristina Paro de Paz3
1
Programa de Pós-Graduação em Produção Animal Sustentável, Instituto de Zootecnia.
Instituto de Zootecnia, Nova Odessa-SP.
3
Instituto de Zootecnia - Centro APTA Bovinos de Corte, Sertãozinho-SP.e-mail: [email protected]
2
Resumo: O objetivo do presente trabalho foi avaliar os efeitos ambientais que interferem na infestação natural de
bovinos taurinos da raça Senepol com o carrapato Rhipicephalus microplus e o berne, Dermatobia hominis,
associando o nível de infestação com a perda de peso. Foram realizadas as contagens de fêmeas do carrapato R.
microplus com tamanho médio de 4 mm e dos nódulos contendo a forma larval de D. hominis (berne) em um
rebanho localizado no município de Cássia, MG. Na coleta de dados, foram considerados 2 períodos para a
mensuração (primavera e verão). As contagens de carrapatos e bernes foram realizadas nos machos e fêmeas, a
partir de 13 meses de idade, para os grupos genéticos PO (puro de origem) e PC2 (1/16 zebu). O peso dos animais
também foi mensurado. Para as análises das contagens foram utilizados modelos lineares generalizados,
empregando-se funções logarítmicas. Para a contagem de carrapatos, considerou-se a distribuição de Poisson e, para
a contagem de bernes, considerou-se a distribuição Binomial negativa. As características em estudo foram
analisadas pelo método do qui-quadrado, utilizando-se o procedimento GENMOD do programa SAS 9.2. O grau
de infestação natural por carrapato e berne variou entre as estações, pastagens e grupos genéticos estudados.
Animais oriundos do cruzamento absorvente de raças zebuínas com Senepol (PC2) são menos infestados que
animais Senepol PO, que, por sua vez, sendo mais suscetíveis ao carrapato, perdem mais peso.
Palavras–chave: adaptação, berne, carrapato, ectoparasitos, resistência
Evaluation of infestation of Senepol cattle with Rhipicephalus microplus and Dermatobia hominis1
Abstract: The objective of this study was to evaluate the environmental effects that interfere with the natural
infestation of taurine Senepol cattle with the tick Rhipicephalus microplus and the botfly Dermatobia hominis,
associating infestation levels with weight loss. Rhipicephalus microplus females with an average size of 4 mm and
nodules containing the larval form of D. hominis were counted in a herd from the town of Cássia, MG. The data
were collected during two seasons: spring and summer. Ticks and botflies were counted on males and females of
purebred and PC2 (1/16 Zebu) genetic groups after 13 months of age. The weight of the animals was also measured.
Generalized linear models employing logarithmic functions were used for the analysis of tick and botfly counts
considering Poisson and negative binomial distributions, respectively. The traits were analyzed by the chi-squared
method using the GENMOD procedure of the SAS 9.2 program. The level of natural infestation with ticks and
botflies differed between seasons, pastures, and genetic groups. Animals originating from the crossing of Zebu
breeds with Senepol (PC2) animals are less infested than purebred Senepol animals. Since the latter are more
susceptible to ticks, they lose more weight.
Keywords: adaptation, botfly, ectoparasites, resistance, tick
Introduction
Among environmental factors that affect animal production, ectoparasites such as the tick Rhipicephalus
microplus and the botfly Dermatobia hominis are particularly detrimental to the performance of cattle as a result of
their predatory, mechanical, toxic and disease-transmitting activities (FRAGA et al., 2003; BARBOSA et al., 2002).
According to Grisi et al. (2014), in Brazil, the economic losses for cattle producers due to tick and botfly infestation
reach 3,236.35 and 383.48 million dollars per year, respectively.
The limitations of currently available control methods indicate the need to offer breeders new alternatives
which, however, do not increase production costs. Genetic resistance of cattle to ectoparasites, which is based on
the selection of animals of the same breed proven resistant and the crossing between resistant and susceptible, but
high-producing, breeds, meets these requirements and may be the main factor influencing the cost of parasite
control because of its low cost and permanent benefits (BIEGELMEYER et al., 2012).
The objective of the present study was to evaluate the environmental effects that interfere with the natural
infestation of taurine Senepol cattle with the tick R. microplus and with the larval form of D. hominis, associating
infestation levels with weight loss.
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Material and Methods
The data were collected from purebred and PC2 (1/16 Zebu breed) cattle belonging to a farm located in the
town of Cássia, MG. Counts of natural infestation with R. microplus females > 4 mm and nodules of D. hominis
larvae were obtained for the left side of males and females of the purebred and PC2 genetic groups after 13 months
of age. This value was multiplied by 2 to obtain the total number of ticks. During the experiment which comprised
the spring and summer seasons, data were collected on four occasions between November 2013 and January 2014,
for a total of 302 observations. The weight of the animals was also measured. All evaluations were performed at
least 30 days after the application of an injectable chemical acaricide containing 1% avermectin. Generalized linear
models employing logarithmic functions were used for the analysis of tick and botfly counts considering Poisson
and negative binomial distributions, respectively. The traits studied were analyzed by the chi-squared method using
the GENMOD procedure of the SAS 9.2 program. Analysis of variance was performed for animal weight using
linear models and the GLM procedure (SAS).
Results and Discussion
The estimated least squares means of the number of botflies and ticks in the experiment indicated a
significant effect of the genetic group (P<0.10), season of measurement (P<0.0001), and pasture (P<0.05) on tick
and botfly counts (Table 1).
Table 1. Estimated least squares means of the number of botflies and ticks in the experiment
Effect
Genetic group
Purebred
PC2
Sex
Female
Male
Season
Spring
Summer
Pasture
1
2
3
Botfly
Tick
N
113
185
1.4167 ±0.2987 A
0.6411 ±0.3726 B
281.3318 ±0.0942 A
186.4840 ±0.1753 B
209
89
1.1754 ±0.2904 A
0. 7727 ±0.3667 A
233.5685 ±0.0929 A
224.6188± 0.1473 A
87
211
0.4683 ±0.3864 A
1.9395 ±0.2673 B
198.1205 ±0.1352 A
264.8078 ±0.1007 B
20
69
209
0.6514 ±0.7053 A
0.5976 ±0.3447 A
2.2238 ±0.2007 B
90.3927 ±0.2377 A
346.2408 ±0.1517 B
383.9537 ±0.0931 B
Means in the same column followed by different uppercase letters differ significantly (P<0.05).
The present study demonstrated the effect of season of the year on the level of natural infestation of cattle
with ectoparasites, with the observation of increasing infestation with both botflies and ticks over the year. The
results also showed that the pasture on which the animals grazed influenced tick count. This finding can be
explained by the forage species used as pasture (Brachiaria decumbens) and by the fact that the pastures were
degraded and contained large numbers of invasive plants that favor the ascent of larvae on the host, since
fecundated tick females fall on the ground for oviposition after a blood meal (VERÍSSIMO, 2013).
Analysis of variance of weight as a function of botfly count for the sampling period showed significant
effects for genetic group (P<0.01), sex (P<0.01), and age (P<0.05). The effect of linear regression of weight on
botfly count did not influence animal weight during the period studied. Analysis of weight as a function of tick
count showed a significant effect (P<0.01) for genetic group and sex. The effect of age was not significant
(P>0.05). To evaluate the occurrence of weight loss as a function of tick infestation for each genetic group,
regression of the class of tick counts was nested within the genetic group class. The effect of regression within the
genetic group was highly significant (P<0.01). The linear regression coefficients estimated were -6.51 kg for
purebred animals and -3.08 kg for PC2 animals, indicating that purebred animals lost more weight. This finding
suggests higher resistance of the PC2 genetic group due to the greater presence of Zebu heritage and, consequently,
less infestation with ticks.
Conclusions
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Animals originating from the crossing of Zebu breeds with Senepol (PC2) animals are less infested than
purebred Senepol animals. Since the latter are more susceptible to ticks, they lose more weight. The results suggest
that the Association of Senepol Cattle Breeders should conduct further studies in different herds in order to
elucidate the differences in ectoparasite infestation observed between the different genetic groups, and to include
this important trait (tick resistance), which affects animal performance and health, in the selection process of the
breed in Brazil.
References
Barbosa, C. G.; Sanavria, A.; Barbosa, M. D. P. R. C. 2002. Fase parasitária e alterações clínicas em bovinos
infestados experimentalmente com larvas de Dermatobia hominis (Díptera: Cuterebridae). Parasitol. Latinoam.
57:15-20.
Biegelmeyer, P.; Nizoli, L. Q.; Cardoso, F. F.; Dionello, N. J. L. 2012. Aspectos da resistência de bovinos ao
carrapato Rhipicephalus (Boophilus) Microplus. Archivos de Zootecnia 61:1-11.
Fraga, A. B.; Alencar, M. M.; Figueiredo, L. A.; Razook, A. G.; Cyrillo, J. N. S. G. 2003. Análise de fatores
genéticos e ambientais que afetam a infestação de fêmeas bovinas da raça caracu por carrapato (Boophilus
microplus). Revista Brasileira de Zootecnia 32:1578-1586 Suplemento, 1.
Grisi, L.; Leite, R. C.; Martins, J. R. S.; Barros, A. T. M.; Andreotti, R.; Cancado, P. H. D.; León, A. A. P.; Pereira,
J. B.; Villela, H. S. L. 2014. Reassessment of the potential economic impact of cattle parasites in Brazil. Braz. J.
Vet. Parasitol. 23:150-156.
Veríssimo, C. J. 2013. Fatores que afetam a fase de vida livre de carrapatos. p. 2-17. In: Controle de carrapatos nas
pastagens. Veríssimo, C. J., ed. Instituto de Zootecnia, Nova Odessa.
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