Parasitism in Angus x Nellore heifers in a silvopastoral system.

The influence of shade in the silvopastoral system on the performance and degree of parasitism by endo- and ectoparasites in Angus x Nellore heifers was assessed. The experiment was conducted with 72 heifers, with an initial mean weight of 276 ± 5.67 kg and 9 months of age, in a total area of 25 ha, divided into 12 paddocks, with three treatments and four replicates. The experimental design was a randomized complete block design, to evaluate the conventional grazing system (CGS) without shade and silvopastoral systems with simple line (SPS1) or triple lines (SPS3) of eucalyptus. The evaluations were carried out every 28 days, from June 2017 to April 2018. During the trial, the number of eggs per gram of feces (EPG) presented a gradual increase in the three systems. Differences (P < 0.05) in the variables analyzed were recorded only in two occasions: the CGS group EPG mean ± standard error (1269 ± 105) was higher than the SPS1 group mean (402 ± 129 EPG) in March, and tick average of the CGS group (13 ± 2.7) was lower than the SPS3 (32 ± 5.3) in October. There were no significant differences (P ≥ 0.05) between groups in relation to horn fly counts, the numbers of infective nematode larvae on pasture, hematological variables, and weight gain. It was concluded that in comparison with the CGS system, the shading in the SPS1 and SPS3 systems did not have any major influence on the degree of parasitism or in the performance of the heifers.