Target selective treatment based on liveweight gain as nematode control strategy in Morada Nova lamb

Abstract

The research team of the present proposal carried out the FAPESP project "Genetic characterization and immune responses associated with the phenotype of parasitic resistance in the Morada Nova sheep flock" (2017/01626-1). It is now expected to advance in the knowledge generated by the evaluation of the 287 lambs and 123 matrices of the aforementioned project so that applicable technologies can be made available for the selective control of gastrointestinal nematodes (GIN) of small ruminants using as model the Morada Nova breed. It is intended to measure the impact of infection by GIN on the growth curve of the animals, in order to develop a model of deworming of the animals by means of selective treatment (TST), using the daily weight gain as indicator (Happy FactorTM). This strategy seems to be more adequate than the egg count per gram of feces (EPG), or even the FAMACHA© method, since Morada Nova lambs with high parasitic load remained with elevated hematocrit. Thus, in the future, the Happy FactorTM could be evaluated, because by means of this practice we can detect the most infected animals, optimize their weight gain and reduce the contamination of pasture by GIN, maintaining representative refuge and minimizing the selection of alleles of resistance. In addition, we intend to identify molecular markers associated with parasite resistance after genotyping of sheep on high density chip (GWAS), as well as to evaluate the main differentially expressed genes (RNAseq) between parasite infection extremes, to identify and select resistant animals. The future validation and availability of a TST would reduce costs with anthelmintics, drug residues in meat, dissemination of genes that confer resistance to anthelmintics, with consequent increase in their time of use. Thus, through the provision of practical and reliable parasitic control tools, the Morada Nova production in the state of São Paulo would be encouraged. (AU)