Abstract
The objective of this study was to determine the effect of post AI administration of exogenous progesterone (P4) or a prostaglandin F2α (PGF2α) synthesis inhibitor agent on serum P4 concentrations and pregnancy per AI (P/AI) in lactating dairy cows. Eighty lactating cows were randomly allocated to one of four treatment groups: 1) CON (control), received 5 mL of saline solution on d 6 and 14 post AI; 2) IP4 (injection of P 4), received 125 mg of P4 im on d 6 and 14 post AI; 3) CIDR, received a controlled internal drug release insert containing 1.38g of P4 from d 6 to 20 post AI; and 4) FM (Flunixin Meglumine), received 0.625 g of Flunixin Meglumine, a nonsteroidal anti-inflammatory drug, twice daily on d 15 and 19 post AI. Blood samples were taken on d 0, 6, 14, 17 and 20 post AI to determine P4 concentrations. Transrectal palpation was performed between 40 and 45 d post AI to determine pregnancy status. All treatment groups (i.e. IP4, CIDR and FM) resulted in greater serum P4 concentration on d 17 and 20 post AI compared to CON (P < 0.05). Cows given a CIDR insert had greater concentrations of P 4 on d 17 and 20 than IP4 and FM cows (P < 0.05). However, no significant difference was found between IP4 and FM groups for serum P4 concentrations. The P/AI was greater (P < 0.05) in CIDR-treated cows (55%, 11/20) than CON (25%, 5/20), and intermediate in IP4 (40%, 8/20) and FM (35%, 7/20) cows. In summary, treatment with exogenous P4 (i.e. CIDR and IP4) or FM increased serum P4 concentrations in lactating dairy cows. However, results suggest that only CIDR administration would improve P/AI.
Highlights
Embryonic development and establishment of pregnancy in cattle depends upon progesterone (P4) secretion by the corpus luteum (CL; Santos et al, 2004; Leroy et al, 2008; Motavalli et al, 2017)
Cows in the IP4, CIDR and Flunixin Meglumine (FM) groups tended to have greater (P = 0.06) serum P4 concentration at d 14 post AI and had greater (P < 0.01) serum P4 concentration at d 17 and 20 post AI compared to cows in the CON group
There was no significant difference for serum P4 concentration between IP4 and FM during the entire study
Summary
Embryonic development and establishment of pregnancy in cattle depends upon progesterone (P4) secretion by the corpus luteum (CL; Santos et al, 2004; Leroy et al, 2008; Motavalli et al, 2017). Various studies have evaluated the effect of supplementation with exogenous P4 during metestrus or early diestrus on fertility of dairy cows, but results have been inconsistent (Larson et al, 2007; Arndt et al, 2009; Friedman et al, 2012; Colazo et al, 2013) In this regard, the efficacy of P4 supplementation post-AI on pregnancy success was recently evaluated in a meta-analysis including 84 treatments involving data from 19,040 cows (Yan et al, 2016). Other studies have attempted to extend the life-span of the CL with the administration of agents that inhibit the synthesis or release of PGF2α to enhance pregnancy in cattle (Elli et al, 2001; Geary et al, 2010). Anderson et al (1986) reported that FM could potentially extend the life-span of the CL in lactating dairy cows, there is a Barkhori-Mehni et al Exogenous Progesterone After AI on Cattle P/AI
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