RECOVERY OF INFECTIVE LARVAE OF HAEMONCHUS SP. IN MARANDU GRASS AND ITS CORRELATION WITH THE MORPHOLOGICAL COMPONENTS OF THE PASTURE

Abstract

Gastrointestinal parasites are among the main challenges for small ruminant farming. As part of the cycle of these parasites undergoes in the environment, allowing small microclimate changes by pasture management could be an alternative to control parasites. This work was carried out to evaluate the survival of infective larvae of Haemonchus sp., in samples of Brachiaria brizantha cv. Marandu, and the influence of pasture morphological components in these findings. The experiment was carried out at a 800 m2 experimental area of Marandu grass, located at Capim Branco Experimental Farm, Uberlândia, Minas Gerais, Brazil. Twenty-eight sites of 10 cm and 35 cm grass height were marked to subsequent deposit of 5g of sheep feces, with mean 1,100 Strongylid egg per gram. Before grass contamination, feces were cultured in the laboratory for seven days, so that the eggs developed to third instar larvae (L3). The forage samples were obtained in triplicate for each treatment, with the aid of a square of 100 cm², which was placed around the site of fecal deposition. Grass sampling occurred on the days zero, 7, 14, 28, 42, 56 and 70 after contamination, in order to obtain and identify third instar larvae (L3). We evaluated the effect of time (10 and 35 cm) and the time post infection (7, 14, 28, 42, 56 and 70 days) in a 2x6 factor design by SAS GLM procedure. The average L3 found in the upper and lower strata of pasture was compared by a paired ttest. In addition, the morphological components of each grass plot were Sepearman correlated with the number of recovered L3. Only Haemonchus sp. L3 were found in significant amounts to provide statistical analysis. The amount of L3 was higher 7 and 14 days after contamination. After day 14, there was significant reduction in the number of L3 recovered (p <0.05), but they could be found until the 70th day after contamination. There was no difference in the number of L3 recovered in pasture with different heights, or between the upper and lower strata of grass (p> 0.05). The number of Haemonchus sp. L3 was positively correlated with the total wet weight of fodder, dry and wet mass of living and dead leaf, dry and wet mass of living and dead thatch and volume density of living leaf. These conditions must be taken into account when planning the grazing management of small ruminants in this kind of grass.