Effect of tannins-rich plants to control gastrointestinal nematodes in Zebu cows grazing in a sub-tropical sylvopastoral system

Abstract

Two grazing systems were compared, one of a conventional sort limited to grass (GS) and the other a mixed sylvopastoral system (SGS), with respect to their effect on control of gastrointestinal parasitic nematodes. Sixty-two lactating crossbred Zebu cows (457 ± 25 kg bodyweight) were divided into in two groups of 31 each. The GS group was maintained 24 h daily without shade, grazing Cynodon or Brachiaria herbage, while the SGS cows had access to the above mentioned grasses and to a subtropical forest. All of the animals received 2.5 kg/d of a slowintake supplement containing urea. The measurements performed were: fecal parasite egg counts on eight occasions over 200d, identification of nematodes by growth of their larvae in culture, packed red blood cell volume (PCV), FARMACHA index value based on coloration of the conjunctiva mucosa, and body condition score (BCS). A greater number of eggs per gram of feces (EPGF) were found in GS cows than in those of SGS (p<0.05). In both systems the PCV remained within the normal range, but the FAMACHA© value was higher under SGS (p<0.05). The BCS of SGS and GS cows were 3.3 and 2.7 respectively (p<0.01). In GS data the following correlations (r) were obtained: negative, EPGF with PCV (-0.77), with BCS (-0.61) and with FAMACHA score (-0.41); and positive, BCS with FAMACHA value (0.62). In SGS data the highest and negative condition was that of PCV with FAMACHA© score (-0.32). The principal nematodes identified in culture for both systems were Oesophagostomum spp, Haemonchus contortus, Trichostrongylus and Cooperia spp. It was concluded that the mixed sylvopastoral system shows promise for controlling parasitic nematode infection in bovines to the benefit of animal health.