Effect of intrauterine administration of gonadotropin releasing hormone with glycerol on serum LH concentrations in lactating dairy cows

• Published in: Animal reproduction science 2014-02, Vol.145 (1-2), p.15-22
• Main Authors: Bas, S., Maquivar, M.G., Silva, M.A. Coutinho da, Day, M.L., Daglio, M.C., Harguindeguy, S., Titler, M., Schuenemann, G.M.
• Format: Article
• Language: English
• Subjects: Animals; Cattle - blood; Dairy cattle; Dairying; Drug Administration Routes; Estrus Synchronization - methods; Female; Glycerol - administration & dosage; Gonadotropin-Releasing Hormone - administration & dosage; Intrauterine GnRH; Lactation - blood; Luteinizing Hormone - blood; Ovulation; Ovulation - drug effects; Ovulation Induction - methods; Ovulation Induction - veterinary; Progesterone - blood; Uterus
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2013.12.017

The objectives of the study were to assess: (1) preovulatory serum LH concentrations and (2) synchrony of ovulation after im or iu administration of GnRH with or without the addition of glycerol. Cows were presynchronized with 2 injections of PGF2α given 14d apart (starting at 26±3DIM) followed by Ovsynch (OV; GnRH-7d-PGF2α-48h-GnRH) 12d later. At the time of the second GnRH of OV (GnRH2), cows were blocked by parity and randomly allocated to 1 of 4 treatments: (1) control (CON; n=8) received 2mL of sterile water im; (2) im (IM; n=8) received 100μg of GnRH im; (3) cows were infused with 200μg GnRH into the uterus (IU; n=9); and (4) iu administration of 200μg GnRH plus glycerol 7% v/v (IUG; n=8). Serum circulating progesterone concentrations at hour 0 did not differ (P>0.05) among groups. Concentrations of LH were greater (P