52- Effect of antiparasitic treatment on the development of mammary gland parenchyma in Holstein heifers

PERRI, AF; LICOFF, N; MEJIA, ME; FORMIA, N; ORNSTEIN, A; BECU-VILLALOBOS, D; ORTEGA, H.; DALLARD, B.; LACAU-MENGIDO, IM

Buenos Aires, Argentina

Jornada; XII Jornadas de la Sociedad Argentina de Biología; 2010

Nematode gastrointestinal parasites are known to delay growth and puberty onset in grazing cattle and to decrease serum IGF-I levels. As IGF-1 is involved in mammary growth and differentiation in prepubertal heifers we wished to investigate if nematode burden may impair normal mammary development. To this end 40 female Holstein calves were randomly assigned, at birth, to an untreated control group (C) or to the treated group (T) which received monthly, from birth onward, the following drugs: ivermectin (0.63 mg/Kg), fenbendazol (7.5 mg/Kg) and/or levamisol (10 mg/Kg). At 20, 30, 40 and 70 weeks of age blood and fecal samples were taken for serum IGF-I determination by RIA and nematode egg counting (EPG) in feces, and mammary biopsies were taken to 6 heifers in each group for histological and immunohistochemical studies.  IGF-I increased with age (P =0.003) and was higher in T calves (P=0.042), whereas C calves had always higher EPG (P =0.020). Mammary parenchyma was embedded in fat pad, conforming ductal developing structures of epithelial cells, more organized as aged. Mammary samples from T heifers had higher ratio of parenchyma/total area (P= 0.036), PCNA  index (P= 0.037) and expression of  estradiol-receptor alpha (P =0.006), compared with C heifers.  These results indicate that lowering parasite burden induces a higher mammary parenchymal development and cell proliferation, as well as a higher density of parenchymal E2 receptors in heifers