Epidemiología de las trichostrongylosis ovinas en el sur de la provincia de Corrientes

Se realizó un estudio epidemiológico de parasitosis gastrointestinales producidas por nematodes, sobre ovinos en el sur de la provincia de Corrientes. Resulta relevante por la importancia de la ovinicultura, por las condiciones propicias para presentaciones clínicas y por la escasa información sistemática. El entorno de resistencia a antiparasitarios exige fundamentos para desarrollar estrategias adecuadas. En este trabajo se evaluó la posibilidad de manejo, basado en datos epidemiológicos y vigilancia mensual. Se realizó un seguimiento longitudinal durante dos años, de cargas parasitarias en ovejas y corderas de recría, mantenidas sin tratamientos (salvo salvataje) dentro de una majada comercial. La evaluación fue mediante la necropsia mensual de dos animales de cada categoría, reflejando la carga acumulada por “pastoreo permanente”. Además, se estudiaron dos corderos “trazadores” que mostraron la infestación adquirida mensualmente. Pudo demostrarse, que las mayores cargas se acumulan en ovejas en el periparto durante el invierno, con predominio de Haemonchus contortus y Trichostrongylus colubriformis, determinando también cualitativa y cuantitativamente el perfil de las cargas globales del campo. El balance hídrico y el almacenaje total de agua en el suelo y su gran variación interanual (especialmente en otoño), explican las cargas parasitarias de H. contortus, que determinan en gran medida la demanda de tratamientos. Estos, a su vez condicionan la oportunidad de Trichostrongylus spp. y de otros parásitos de menor representación para construir cargas hacia el invierno. Las borregas, siguen un patrón de acumulación desde el otoño hasta la primavera, mostrando un perfil más heterogéneo en la composición específica. Las pérdidas productivas, resultan tan variables como la carga parasitaria, pudiendo presentarse en valores insignificantes como demuestra este trabajo. Una estrategia de control basada en datos epidemiológicos, seguimiento y registro mensual, permitiría detectarlas incluso cuando éstas fueran mínimas. Se destacan otros factores de pérdidas productivas (principalmente nutricionales) que suelen solaparse tras los trastornos de origen parasitario.

61 Oral Dosing Loline Alkaloid and Its Effects Against Mixed Infection of L4 Teladorsagia Circumcincta, and Trichostrongylus Colubriformis, and Adult Haemonchus Contortus

Loline, an alkaloid produced by Epichloë endophytes in pastoral grass species, is considered non-toxic with suggested antimicrobial and anthelmintic properties. In vivo metabolism of loline suggests ability to reach the abomasum or intestine, and anthelmintic benefit is indicated in vitro when parasites are in either a developmental stage close to the gastric mucus layers or adult stage consuming blood. Therefore, the objective of this project was to investigate the validation of using a loline seed extract as a natural anthelmintic in parasitized lambs. Sixteen Coopworth lambs were individually penned, offered ad-libitum lucerne pellets and water and randomly assigned to 3 treatment groups; CON; no treatment, or treatment with a Festuca pratensis seed extract with (LOL) or without loline (NIL). Lambs were orally infected with 20,0000 L3 Haemonchus contortus on day 0, and 10,000 L3 Teladorsagia circumcincta, and Trichostrongylus colubriformis on day 14. Parasites then matured to determine lolines efficacy on blood feeding adult Haemonchus contortus and L4 mucosal browsers Teladorsagia circumcincta, and Trichostrongylus colubriformis. Loline was orally dosed at 52.5 mg/kg LW starting on day 13, and every other day until slaughter for worm enumeration on day 28. Feed intake and refusals were recorded daily, and fecal samples were taken prior to infection, on loline dose days and at slaughter. Worm and fecal egg counts were transformed to log10 and all data were analyzed in Genstat (18th edition). Significance was declared at P < 0.05. Worm burdens of T. circumcincta (P = 0.96), T. colubriformis (P = 0.43), and H. contortus (P = 0.15) were not different between treatments. No treatment difference (P = 0.39) was observed in fecal egg counts, weight gain (P = 0.51), or feed intake (P = 0.18). Average growth efficiency (kg LWG/ kg DM intake) was 0.18 in CON which was less (P = 0.01) than LOL (0.24) or NIL (0.23). In conclusion, limited evidence supported an in vivo anti-parasitic effect of loline.

Performance of lambs under four levels of dietary supplementation and artificially mix-infected with Haemonchus contortus and Trichostrongylus colubriformis

The effect of four diets on the performance of Dorper lambs that were artificially mix-infected with 1000 infective larvae (L3) of Haemonchus contortus and 1000 L3 of Trichostrongylus colubriformis every three days for 12 weeks was evaluated. For each diet, one infected group (n = 7) and one control group (n = 4) were set up. The four diets contained the following proportions of hay (H) and concentrate (C): Diet 1 - 100%H; Diet 2 - 75%H:25%C; Diet 3 - 50%H:50%C; Diet 4 - 25%H:75. All the infected groups showed decreases in mean packed cell volume (PCV) and total plasma protein, especially the Diet 1-infected, which was also the group with the highest fecal egg count. The diets and infection had significant effects (P < 0.05) on daily body weight gain (DBWG), cold carcass weight and daily food consumption. The control and infected groups had mean DBWG (in kg), respectively, of 0.048 and 0.025 with Diet 1; 0.082 and 0.067 with Diet 2; 0.188 and 0.189 with Diet 3; and 0.303 and 0.221 with Diet 4. In conclusion, the infection affected the productive performance regardless of the diet; however, with increased metabolizable protein and energy, the risk of occurrence of anemia and hypoproteinemia diminished.

Trichostrongylus colubriformis affecting sheep phosphorus metabolism and precision feeding as a mitigating strategy

This review details the negative effects of Trichostrongylus colubriformis infection in sheep phosphorus metabolism and direct and indirect impacts from high excretion from susceptible animals, as well as the advantages offered by precision feeding as potential strategies to mitigate loss. In sheep infected with T. colubriformis there is a high reduction in P bioavailability, because of depression in the absorptive capacity of this mineral, affecting the absorption and recycling of P to the digestive tract, causing mineral deficiency. Therefore, precision feeding compiles animal genetics information, feeding type and grazing management to control animal feed intake and quantity and quality of manure produced. In this sense, the adoption of precision feeding can provide a better arrangement of the information, making sheep production more economically, socially and environmentally sustainable.