The gastrointestinal nematodes (GIN), in domestic animals, especially in bovines are a very important factor that affects their productivity, because cattle production systems have intervened in the relationship between gastrointestinal parasites (PGI) and the host, breaking therefore the ecological balance between them. In many opportunities the development of parasitic populations have been favored or a parasitic population have been led to extinction, it has made that these populations express genes that would not express under normal conditions, favoring thus, resistance to medications that were made to their destruction. NGI are highly important in all cattle exploitations, but their inappropriate handling, mainly in the pharmacological aspect, has created vermifuge resistance by some parasitic populations. This article will determine the importance of the vermifuge resistance in cattle exploitations, as a factor of risk for the control of parasitic populations. The most important antihelmintic groups used in bovine are Benzimidazoles, Levamisol and Ivermectine and with these products resistance has been reported by parasitic populations such as in Haemochus contortus, Trichostrongylus. colubriformis, Ostertagia circumcicta, Ostertagia ostertagi. Different risk factors were classified in extrinsic (which don’t depend on the gastrointestinal parasite) and intrinsic (which depend directly on gastrointestinal parasites related with genetics) which occupy a great importance in the development of the vermifuge resistance.

This research was held from January to December 2004 at La Suiza; a buffalo ranch located in the Middle Magdalena River, Colombia. This work was part of a macro research project on the buffalo species, which also included physiological constants determination, hematology parameters evaluation, and eggs per gram elimination curves for gastrointestinal parasites. From a total of 4200 buffalos, 150 animals were randomly selected and divided into three age groups ( <12 months, 2-36 months and >36 months). A fecal sample from each animal was taken once per month for a period of 12 months, making the following parasitological tests; sediment-flotation, Baermann, Dennis and coprocultive. These procedures made it possible to determine the lack of presence of Dictiocaulus spp and Fasciola spp; and the presence of parasites like: nematodirus spp, cooperia spp, ostertagia spp, trichuris spp, oesofagostomum spp, bunostomum spp, trichostrongylus spp, strongyloides spp, eimeria spp, moniezia spp, toxacara spp and haemonchus spp in the buffalo population in La Suiza Ranch..

The present study was carried out in the region of Los Lagos in Chile. The purpose of this research was to determine the time of apparition and the morphologic characteristics of larvae L1, L2 and L3 of large and small strongyles of horses. 10 animals belonging to “Isla Teja” of the Universidad Austral de Chile campus were used. A sample of faeces was taken from these animals and the number of eggs per gram in faecal material was determined using the McMaster’s technique. After selecting the four samples with the highest counts, eggs were planted with temperature and humidity controlled in order to subsample every 24 hours for a period of 21 days. These sub-samples were analyzed by direct observation and Baerman’s technique, scoring macro and microscopically changes. It was possible to differentiate between larvae L1, L2 and L3 of large and small strongyles. Larvae L1, L2 and L3 of small strongyles appeared from days 2, 3 and 7 respectively.

This study was conducted with 171 animals from La Suiza Farm, located in the Municipality of Puerto Nare, Antioquia, in order to determine the physiological parameters and hematological values in water buffalos (Bubalus bubalis) from the Colombian Middle Magdalena. This population was selected and classified into different age groups as follows: under one year of age, 51 animals; one to three years of age: 56 animals, and over three years of age: 64 animals. Heart rate, breathing rate, pulse, capillary refill time, temperature and rumian movements were taken from the same animals once a month for 4 months. Likewise, blood was extracted from the jugular vein for hematologic analysis of hematocrit, total plasma protein, total serum protein and leukocyte count. Results: reference ranges of physiological and hematological parameters were found in water buffalos from La Suiza Farm in the Colombian Middle Magdalena.