Comparative study of the parasite load in two breeds of sheep in Mexico
Authors: Nieto Mariana Paz-Calderón , Aguilar Dulce María Carrasco , Hernández María del Pilar Mancera , Rivas Ricardo E. Caicedo 
Published: July 2024

Gastrointestinal parasites (GIP) produce great economic losses in livestock systems in Mexico, causing deficiencies in productive systems, mainly in food production; Gastrointestinal parasitosis constitutes a mechanism of loss, due to the high degrees of infestation experienced by these ruminants, which mainly causes anemia, liver and kidney damage, weight loss and large reproductive losses such as very prolonged postpartum anestrus. The prevalence of parasites in sheep is estimated between 63.4% to 90.2% prevalence, in a population of 8.9 million sheep in Mexico, distributed in different zoogeographic zones of the country. Based on the above, the objective of this study was to establish the foundations for the development of a breed or breeds of sheep resistant to gastrointestinal parasites (PGI). To achieve this objective, 183 sheep of the Criolla and Dorper breeds were randomly selected. These were under a grazing system and in addition, phenotypic characteristics were determined such as: body condition, FAMACHA, hematocrit (%). Fecal samples were taken from each animal and analyzed using sedimentation, flotation and direct coproparasitological tests, and the parasite load, eggs per gram of feces (HPG), was determined using the Mac Master chamber method (modified) by animal. To detect the damage caused by the different degrees of parasite infestation, tests were carried out on the metabolomics-metabolic profile of each animal depending on the type of parasite and total parasite load. The data obtained showed that the most prevalent GIP were: Strongyloides papillosus (38.15%), Trichostrongylus spp (32.91%), Haemonchus contortus (21.25%), Trichuris ovis (7.69), Oesophagostomun spp (2 .56%), Ascaris spp (1.56). and Fasciola hepatica (1.32%), this last parasite is not considered a gastrointestinal parasite, according to many authors, however, the laboratory does consider it. The values ​​of metabolites detected through the metabolic profile showed that the higher the parasite load-EGF, these metabolites fluctuated at low levels compared to clinically healthy animals (CHA) such as: glucose, PT, albumin, creatinine, while bilirubin tends to increase, the greater the parasite load-HPG, but this will also depend on the type of parasites that each animal presents; while the alkaline phosphatase enzyme tends to decrease when the EGF is higher. Hematocrit (%) values ​​decreased with respect to high parasite loads, mainly due to Haemochus contortus and Fasciola hepatica. In conclusion: GIP parasites play a significant role in the productive and reproductive development of these breeds of small ruminants, therefore, to produce sheep resistant to GIP it is necessary to detect which parasites are the most prevalent and which ones affect the metabolic activity of each animal or groups of sheep depending on their breed and diet, mainly, and that Creole sheep are more resistant to high GIP loads, they tend to lose weight, but not their reproductive capacity, finally their immune system has to control these loads of GPI, becoming animals with a high degree of resilience in relation to the Dorper breed.