Abstract
Lutalyse HighCon (dinoprost tromethamine; Zoetis) has been approved for use both intramuscularly and subcutaneously in lactating dairy cows, although the effect of route of administration on circulating 13,14-dihydro-15-keto-prostaglandin F2α (PGFM), the metabolite of PGF2α, has not been evaluated. Multiparous, lactating Holstein cows were submitted to an Ovsynch protocol in which the last GnRH treatment (G2) was designated as d 0. Cows were fitted with indwelling jugular catheters on d 6 and administered 25 mg of dinoprost tromethamine (2 mL of Lutalyse HighCon) on d 7 either subcutaneously in the neck (SC; n = 6) or intramuscularly in the semitendinosus muscle (IM; n = 6). Blood samples were collected every 15 min after treatment for 1.75 h, then every 2 h for 48 h, and at 60 and 72 h, with the last time point corresponding to when cows would have received timed AI at 72 h within an Ovsynch protocol. Circulating PGFM concentrations were greater for SC than for IM cows from 15 to 90 min after treatment, which resulted in a greater area under the PGFM curve during the first 90 min after treatment (means ± SEM; 1,664 ± 129 pg·h/mL vs. 1,146 ± 177 pg·h/mL for SC vs. IM cows, respectively). This resulted in complete luteolysis in all but one cow in the SC treatment at 56 h, when GnRH would have been administered if dinoprost tromethamine had been administered as part of an Ovsynch protocol for timed AI. For cows that underwent complete luteal regression, circulating P4 did not differ between treatments at any time point. Thus, although SC cows had increased circulating PGFM 15 to 90 min after treatment, there was no difference in circulating P4 during induced luteolysis based on route of dinoprost tromethamine administration.
Highlights
Our objective was to determine the effect of route of administration of dinoprost tromethamine 7 d after treatment with GnRH on circulating 13,14-dihydro-15-keto-prostaglandin F2α (PGFM) and progesterone (P4) concentrations in lactating dairy cows
Cows were fitted with indwelling jugular catheters on d 6 and administered 25 mg of dinoprost tromethamine (2 mL of Lutalyse HighCon) on d 7 either subcutaneously in the neck (SC; n = 6) or intramuscularly in the semitendinosus muscle (IM; n = 6)
Circulating PGFM concentrations were greater for SC than for IM cows from 15 to 90 min after treatment, which resulted in a greater area under the PGFM curve during the first 90 min after treatment
Summary
Our objective was to determine the effect of route of administration of dinoprost tromethamine 7 d after treatment with GnRH on circulating 13,14-dihydro-15-keto-prostaglandin F2α (PGFM) and progesterone (P4) concentrations in lactating dairy cows. Multiparous Holstein cows fitted with indwelling jugular catheters were randomized 7 d after the last GnRH of an Ovsynch protocol (G2, d 0) to receive 25 mg of dinoprost tromethamine either intramuscularly (IM) or subcutaneously (SC). The SC cows had greater circulating PGFM concentrations 15 to 90 min after treatment than the IM cows; circulating P4 concentrations during induced luteolysis did not differ at any time based on route of administration
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