Effect of intrauterine administration of gonadotropin releasing hormone with glycerol on serum LH concentrations in lactating dairy cows.
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<0.05) in IM than IU, IUG, and CON cows at hours 1, 1.5, 2, and 3. All cows ovulated within 48h in the IM (8/8) group followed by IU (6/9) and IUG (4/8) groups, and only two out of eight cows ovulated in the CON group. Although iu administration of GnRH in the IU and IUG groups resulted in lower serum concentrations of LH than IM cows, IU or IUG cows were able to ovulate within 48h after GnRH2 administration.
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Bas
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Maquivar
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Coutinho da Silva
Department of Animal Sciences, College of Food, Agricultural, and Environmental Sciences, The Ohio State University, Columbus, OH, USA.
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Day
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Daglio
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Harguindeguy
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA.
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Titler
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA. Electronic address: schuenemann.5@osu.edu.
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Schuenemann
D000818:Animals; D002417:Cattle / Q000097:blood; D003612:Dairying; D004333:Drug Administration Routes; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D005990:Glycerol / Q000008:administration & dosage*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007774:Lactation / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood*; D010060:Ovulation / Q000187:drug effects; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary; D011374:Progesterone / Q000097:blood; D014599:Uterus
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007986:Luteinizing Hormone; D005990:Glycerol
Dairy cattle; Intrauterine GnRH; LH; Ovulation