Performance of gastrointestinal nematode infestations of young cattle in silvopastoral systems

Mildrey Soca Pérez
Estación Experimental de Pastos y Forrajes Indio Hatuey, Central España Republicana 44280, Matanzas, Cuba

ABSTRACT
In order to determine the performance of gastrointestinal nematode infestations of young cattle in silvopastoral systems, a research was conducted in experimental areas of the EEPF “Indio Hatuey”, in the Matanzas province, Cuba, in which two systems were evaluated: A) Silvopastoral system and B) System without trees. The studies were carried out during a year, in the rainy and dry season, respectively, from July, 2000, to September, 2001. The research comprised three experiments: 1) Determination of the decomposition rate of the droppings of young cattle in silvopastoral systems; 2) Parasitological characterization of the droppings of young cattle under silvopastoral system conditions, 3) Seasonal performance of gastrointestinal nematode infestations of young cattle in silvopastoral systems. Six animals were used per treatment of the breed 5/8 Holstein x 3/8 Zebu, with an average age of six months and a mean weight of 80 kg at the beginning of the trial. When evaluating the parasitological dynamics of the droppings (experiments 1 and 2), it was observed that the silvopastoral system showed a rapid decomposition (P<0,001), which was higher than 95 % after 10 and 4 days of deposition for the dry and rainy seasons, respectively; while in the system without trees the decomposition was much slower in the dry season (42 %), and although in the rainy season this process was much faster, it was related to the fragmentation and dispersion of the droppings due to the rainfall and not to the burial of the fecal matter. The presence of trees was vital in the decomposition process, because in the silvopastoral system a significant increase was found (P<0,05) of the number of individuals/m2 (1 116 vs. 2 547) and of individuals per dung (14,51 vs. 32,94) (P<0,01), in the rainy and dry season, respectively, with regards to the system without trees; this edaphic fauna had an outstanding participation in the decomposition process of the droppings. Similar results were shown by the fecal egg count, which was 98 % and 100 % 168 and 96 hours after they were deposited for the rainy and dry seasons, respectively. Significant correlations (P<0,001) were found between the weight decrease of the droppings and the egg count, with a correlation coefficient r2=0,544 for the dry season and r2=0,837 in the rainy season. From the equations obtained with the different regression models, the linear one showed the highest adjustment for the experimental results in both seasons, although it was also adjusted to the equation √x. This performance was related to the presence of coprophagous coleopterans in the droppings, which was significantly higher (P<0,01) in the silvopastoral system with regards to the system without trees. In Experiment 3, related to the seasonal performance of this parasite infestations in the animals the presence of the genera Oesophagostomum and Haemonchus was found; the latter was the one with the highest annual incidence in both systems. The fecal egg count (epg) showed significant differences (P<0,01) from the second month of evaluation and in favor of the silvopastoral system, showing a more stable curve and with values below 1 000 epg. A similar performance was shown by the annual average of epg (520 vs. 1 412) and per season: dry (471 vs. 1 183) and rainy (596 vs. 1 814), which was significantly lower (P<0,001) for the silvopastoral system with regards to the system without trees. The nematode infestations in the silvopastoral systems maintained a well-defined seasonal performance, with the highest infestation in the months of highest rainfall. The stability and better performance of these parasite infestations in the silvopastoral system was closely related to the dry matter (DM) availability, pasture height and chemical composition of the herbaceous and tree stratum. The results obtained in all the experiments confirm the potential of these systems to contribute significantly to the decrease of the incidence of these nematode infestations in young cattle under the Cuban conditions.