98 COMMERCIAL APPLICATION OF A NEW COW-SIDE LH ASSAY FOR DETERMINING OPTIMUM AI INTERVALS IN SUPEROVULATED BEEF DONORS IN THE USA: A PRELIMINARY STUDY

Abstract

Successful superovulation and embryo collection require donors to be managed for precise insemination intervals. At times, determinations of these intervals can become difficult because of oestrus detection subjectivity. The objective of this study was to determine the feasibility of performing a rapid cow-side LH assay (Predi′Bov^®, ReproPharm, Nouzilly, France) on superovulated donors with emphasis on determining how to use the results in a commercial program to time inseminations. This study was conducted at Ovagenix (Bryan, TX, USA) on 24 superovulated donors. On Day 0 cows received an intravaginal progesterone-releasing device (CIDR^®, Pfizer Animal Health, New York, NY, USA) and were administered 25 mg of progesterone and 2.5 mg of oestradiol 17β intramuscularly (IM, 2 mL). Superstimulation was induced using 150–300 mg of Folltropin-V^® (FSH, Bioniche Animal Health Inc., ON, Canada) administered with 7 injections at 12-h intervals in decreasing dosages (Day 4–7). On Day 6, two doses of Estrumate^® (equaling 1 mg, Intervet Inc., Merck Animal Health, Summit, NJ, USA) were given IM, concurrently with FSH injections 5 and 6 with CIDR removal on Day 7 (a.m.). HeatWatch^® transmitters (Cow Chips LLC, Denver, CO, USA) were applied to donors on Day 7 to determine onset of standing oestrus. Blood samples were collected in heparinized tubes via tail vein puncture starting at CIDR removal continuing every 6 h until a positive Predi′Bov^® test was acquired or 36 h after CIDR removal. Whole blood (0.5 mL^–1) was submitted to a proprietary 3-step procedure using a tube-stick applicator (40 min) to determine whether increased concentrations of LH were present. Stick applicators that turned blue were positive for increased concentrations of LH. Donors were artificially inseminated 12 and 24 h after a positive test, with specified sires, and embryos were nonsurgically collected 7 days after insemination. The Predi′Bov^® test determined 91.6% (22/24) of the LH peaks occurred within 12 to 24 h after CIDR removal; 45.8% (11/24) occurred at 18 h; and 4% (1/24) at 30 h. A total of 203 viable embryos (average 8.5/donor) was collected with 174 embryos (average 9.2 ± 4.7/donor) from donors that exhibited oestrus and produced a positive test (19/24; 79.2%) and 29 embryos (average 5.8 ± 6.3/donor) from donors exhibiting silent oestrus that produced a positive test (5/24; 20.8%). One donor exhibited oestrus and never produced a positive test, but contributed 8 viable embryos to the total. In conclusion, Predi′Bov^® cow-side usage could offer commercial utility when identifying oestrus is difficult or nonexistent. Increased detection of ovulation could help to identify optimal AI intervals, thereby increasing embryo production and limiting the use of expensive semen for desired donors.