Transient Threshold Abundance of Haematobia irritans (Linnaeus, 1758) In Cattle Under Integrated Farming Systems

Abstract

Haematobia irritans is a hematophagous insect that affects the welfare of cattle reducing weight gain and it is present in most countries. The objective of this work was to determine the prevalence of flies, mainly H. irritans in 36 Red Angus calves under four farming ecosystems in Brazil, and to assess an individual threshold limit to treat for horn fly and to attain better animal welfare and farm sustainability. The animals (n = 9) were allocated in livestock (L), crop-livestock (CL), livestock-forestry (LF) and the full integration of crop-livestock-forestry (CLF) conditions. Adult flies were determined between systems on each animal at weekly intervals and in each environment by counting larvae and pupal stages that emerged from selected dung pads. Individual animals were treated for H. irritans infestation after reaching the transient threshold abundance (TTA) of > 100 flies. The data from 1008 evaluations showed that animals in the CLF had significantly (P < 0.05) more horn flies, than animals from the other systems. The level of infestation by horn flies was strongly influenced by the particular ecosystem (P < 0.002), and by the month of the year (P < 0.001). However, the difference in fly numbers did not influence the weight gain of the animals. We found four other genera of the Diptera order (Brontaea spp., Cyrtoneuropsis spp., Fannia spp. and Morellia spp.) that emerged from dung pads. The data suggests that it may be possible to perform evaluations in one animal at a time to control H. irritans with no impact to the performance of the animals when using a low TTA index of infestation. CLF was considered to be the richest environment, favoring fly populations. In our conditions, cattle and different fly species/genera may coexist using sustainable TTA management protocols at farm level in opposite to the concept of fly eradication or mass acaricidal treatment.