Intrafollicular LH administration in dairy heifers treated with a GnRH agonist

The aim of this study was to evaluate the effect of intrafollicular treatment (IFT) with different doses of luteinising hormone. Experimental heifers were treated with a single deslorelin implant to desensitise gonadotroph cells of the pituitary gland. Thereafter, follicular development was stimulated by exogenous FSH treatment. Intrafollicular treatment with 10, 5, 1 and 0.01 μg LH was performed on one single follicle while other follicles remained untreated. Human chorionic gonadotrophine (2000 UI) was administered intravenously as a control. Ovulation and development of the corpus luteum occurred after all intrafollicular treatments with 10 and 5 μg LH. After IFT using 1 μg of LH 75% animals (3/4) ovulated. The dose of 0.01 μg was not followed by any ovulation whereas control treatments with hCG were followed by an ovulation of the majority of follicles present in the ovaries. In conclusion, IFT with different doses of LH (greater than 0.01 μg) is capable of inducing ovulation.