Simulation of infestation risk of cattle by gastro-intestinal trichostrongylids in a tropical humid climate.
The population dynamics of trichostrongylid third stage larvae (L3) around bovine dung were fitted with non-linear models (marginal law) in tropical humid climate in different climatic situations. These marginal models were combined with the survival duration of pats, the weight of cows, the number of pats per cow and per day, the stocking rate and the herbage mass availability, taking into account the patchy grazing behaviour of cattle in order to estimate infestation probability of cattle by third stage larvae. The infestation risk was computed for different ages of herbage regrowth and grazing times in rotational grazing systems. The infestation risk was found to range between 0 to 1400 L3 per kg of dry matter of grass and per day depending on the marginal law. The grazing time, the age of herbage regrowth and the forage availability were the main factors of variation of the infestation risk.