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Paramphistomosis is a parasitic disease endemic in ruminants nearly worldwide. In the present study, an in vitro screening of the main anthelmintics used in Mexico was carried out to determine the mean lethal dose for rumen fluke eggs from cattle in a humid, warm region. Rumen flukes were obtained from cattle slaughtered in the states of Tabasco and Chiapas in Mexico. Eggs were collected using a 37-μm sieve and quantified. Then, an in vitro incubation study was performed: 100 eggs were placed into the wells of polystyrene microtiter plates. Anthelmintic products were tested on the eggs at concentrations ranging from 0.0015 to 3.0 mg/ml for rafoxanide, 0.0025 to 10.20 mg/ml for nitroxinil and 0.0015 to 3 mg/ml for closantel to determine the median lethal dose (LD50) and maximum lethal dose (LD99). A control group (water) was included in each plate. Three different species of rumen flukes (Calicophoron brothriophoron, Calicophoron clavula and Paramphistomum cervi) belonging to five isolates were identified. Nitroxinil had the highest efficacy against rumen fluke eggs, with an LD50 of 0.11 to 65 μg/ml, whereas rafoxanide showed the lowest efficacy with an LD50 ranging from 500 to 1713 μg/ml. Closantel showed high variability in the LD50 among the different analysed isolates (17 to 122 μg/ml). The evaluated flukicidal drugs presented differential efficacy against the development of rumen fluke eggs. The efficacy of the drugs will vary depending on the geographical area of origin of the animals.

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Livestock systems can contribute to food security by making use of available resources not suitable for human consumption such as Cucurbita argyrosperma Huber residue (CR). The aim of this pilot study was to evaluate preference and physicochemical characteristics of CR silages and their effect on milk production and milk composition from cows in a dual-purpose system in Campeche, Mexico. Three completely randomized experiments were performed. In experiment 1, physicochemical characteristics of four CR plus hay grass silages were evaluated: CR-77, CR-71, CR-65 and CR-59, containing 77%, 71%, 65% and 59% of CR, with 25%, 30%, 35% and 40% of estimated dry matter (DM), respectively. In experiment 2, silages intake preferences were determined in cattle. In experiment 3, the effect of CR silage or corn silage on milk production and milk composition of grazing cows in a dual-purpose system was evaluated. The results in experiment 1 showed that DM content differed between treatments (p < 0.05), ranging from 27.35% (CR-77) to 41.81% (CR-59) and estimated DM was similar to the actual values. pH and temperature were also different (p < 0.05). pH was different between CR-71 (4.01) and CR-59 (4.43), and temperature between CR-77 (28.87 °C) and CR-65 (29.5 °C). Crude protein (CP) was very low in all silages (<4%), particularly in CR-59 (2.8%) (p < 0.05), and neutral detergent fiber (NDF) was significantly (p < 0.05) higher with CR-65 and CR-59 (average: 79.6%) than CR-77 and CR-71 (average 75.1%). There were no differences in intake preference (experiment 2), milk production (average 3.7 L) or milk composition (average protein: 3.27%, fat: 2.26%, lactose: 5.23%, solids non-fat: 9.17%) (experiment 3) (p > 0.05), but differences in DM intake of silages in experiment 3 were observed (p < 0.05). Even with the limitations of this pilot study, it is feasible to produce silages with CR with a good fermentation process as a feeding alternative for cows in a dual-purpose system in Campeche, Mexico.