Abstract #451

# 451
Effects of label-dose permethrin administration on reproductive function in superstimulated beef heifers.
Tyler M. Dohlman*1,2, Marianna M. Jahnke1, James K. West1, Patrick E. Phillips1, Patrick J. Gunn2, 1Veterinary and Diagnostic Production Animal Medicine, Iowa State University, Ames, IA, 2Department of Animal Science, Iowa State University, Ames, IA.

The objective was to study the effects of a commercial pyrethroid-based pour-on product, permethrin, on reproductive performance in superovulated beef heifers by assessing steroid biosynthesis and embryo quality. Nonpregnant, yearling beef heifers (n = 10; 417 ± 33 kg; 5.5 ± 0.2 BCS) were assigned by BW and breed to either 1) saline control (CON) or 2) permethrin pour-on administered at label dose (PYR). Superstimulation was achieved on all heifers utilizing a timed, 17-d, CIDR-based protocol with GnRH and PGF2a and decreasing total dosage of 240mg FSH administered twice daily for 4 d. Heifers were AI twice (at onset of estrus and 12 h later) by the same technician with frozen semen from single bull collection. To determine short and long-term effects of permethrin on embryo quality and steroid biosynthesis, superstimulation was initiated twice with collection of embryos occurring at 17 and 51 d post-treatment. Embryos were recovered 6.5 d after first AI via non-surgical flush and were evaluated by International Embryo Transfer Society standards. Blood was collected at standing estrus and d of embryo recovery. Estrogen (E2) and progesterone (P4) concentrations were analyzed via RIA. MIXED and GLIMMIX procedures of SAS were used to analyze continuous and categorical data, respectively. Heifer per flush was the experimental unit. Total embryos recovered did not differ due to treatment (P = 0.30), but did decrease in flush 2 compared with flush 1 (P = 0.02). Quality grade, total transferrable quality embryos (TQE), and overall flush success did not differ due to treatment (P = 0.16). However, TQE was decreased in flush 2 compared with flush 1 (P = 0.05). Total unfertilized oocytes was greater in CON (P = 0.04). The PYR heifers tended to have less total P4 (P = 0.15) and P4 per corpus luteum (P = 0.06) at recovery. E2 per ovulated follicle and E2 per total ovarian structure was greater in flush 2 (P = 0.03) but did not differ due to treatment (P = 0.23). In summary, these data indicate that permethrin administration at label dose in superstimulated beef heifers has a tendency to reduce P4, but embryo quality is not affected.

Key Words: permethrin, embryo, progesterone