Miraballes Cecilia, Sanchez Javier, Barros Antonio Thadeu M, Hitateguy Sebastian, Moreno Pablo, Saporiti Tatiana, Riet-Correa Franklin
National Institute of Agriculture Research (INIA), Tacuarembo, Casilla de Correo 78086, CP 45000, Uruguay; Veterinary Faculty, Republic University (UDELAR), Alberto Lasplaces 1620, CP 11600, Montevideo, Uruguay.
University of Prince Edwards Island, 550 University Ave, Charlottetown, PE C1A4P3, Canada.
Vet Parasitol. 2018 Aug 30;260:58-62. doi: 10.1016/j.vetpar.2018.08.012. Epub 2018 Aug 27.
The distribution of Hematobia irritans is not homogeneous in cattle populations. Generally, between 15% and 30% of bovines carry more than 50% of the flies, and higher infestations occur in bulls. In this study, the effect of treating the bulls with ear tags containing 40% diazinon on the infestation of flies on the herd during the breeding season was evaluated. Four groups of cattle were made, each containing one bull and 35 Braford cows. Groups 1 and 2 were on pastures in highlands. Groups 3 and 4 were on pastures in lowlands. At the beginning of the trial, each bull from Groups 1 and 3 was treated with an ear tag. Bulls from Groups 2 and 4 remained untreated. Weekly, for 10 weeks, horn flies were counted from each bull and 15 cows from each group. A repeated measures linear mixed model was used with cows as random effects. The number of horn flies in the treated groups was lower than that in the untreated group, suggesting that selective treatment of bulls could be an effective strategy to control horn flies on the herd. The number of flies was higher in the lowland than that in the highland groups, suggesting an effect of the environment on horn fly infestations. In addition, we estimated the cow level predictions from the model to estimate the cow effect on fly counts, and we compared those values with the observed weekly quartiles for each group. Fly-susceptible cows were defined as those for which the infestation of flies appeared in the upper quartile more than 50% of the weeks and in the lower quartile less than 20% of the weeks. In contrast, a fly-resistant cow was defined as one for which the fly counts appeared in the lower quartile more than 50% of the weeks and in the upper quartile less than 20% of the weeks. In all, 8.3% of the cows were susceptible and 15% were resistant. These results may be used to selectively treat bulls or to treat the bulls and the most susceptible cows during the breeding season.
血蝇在牛群中的分布并不均匀。一般来说，15%至30%的牛携带了超过50%的苍蝇，且公牛身上的寄生虫侵扰更为严重。在本研究中，评估了在繁殖季节给公牛佩戴含40%二嗪农的耳标对牛群苍蝇侵扰情况的影响。将牛分为四组，每组包含一头公牛和35头布拉福德母牛。第1组和第2组在高地牧场。第3组和第4组在低地牧场。试验开始时，第1组和第3组的每头公牛都佩戴了耳标。第2组和第4组的公牛未接受处理。在10周内，每周对每组的每头公牛和15头母牛身上的角蝇进行计数。采用重复测量线性混合模型，将母牛作为随机效应。处理组的角蝇数量低于未处理组，这表明选择性地处理公牛可能是控制牛群角蝇的有效策略。低地组的苍蝇数量高于高地组，这表明环境对角蝇侵扰有影响。此外，我们从模型中估计了母牛水平的预测值，以估计母牛对苍蝇计数的影响，并将这些值与每组观察到的每周四分位数进行比较。易受苍蝇影响的母牛定义为在超过50%的周中，苍蝇侵扰出现在上四分位数，而在不到20%的周中出现在下四分位数的母牛。相比之下，抗苍蝇的母牛定义为在超过50%的周中，苍蝇计数出现在下四分位数，而在不到20%的周中出现在上四分位数的母牛。总体而言，8.3%的母牛易受影响，15%的母牛具有抗性。这些结果可用于在繁殖季节选择性地处理公牛，或处理公牛和最易受影响的母牛。
