384 EFFECTS OF CONDITION SCORE ON OVARIAN RESPONSE AND TRANSFERABLE EMBRYOS IN SUPERSTIMULATED COWS IN ARGENTINA

Abstract

The success of an embryo transfer program is influenced by ovarian response, number of ovulations, fertilization, and embryo viability (Armstrong 1993). It has been observed that over-conditioned, overweight donor females tend to produce fewer viable embryos per collection (Stroud and Hasler 2006 Theriogenology 65, 65–76). The condition score is one of the many intrinsic factors that affects cow reproduction. A retrospective analysis was done to compare the ovarian response, number of ovulations, fertilization, and total transferable embryos recovered of cows with different condition scores in Argentina. This research was carried out using different breed donors (n = 640; 82% Angus; 18% other) during the last 4 years in Buenos Aires province, Argentina. Donors at random stages of follicular wave with CL received an intravaginal progesterone device (DIB; Syntex, Buenos Aires, Argentina), 2 mg of estradiol benzoate, and 50 mg of progesterone (Syntex, Buenos Aires, Argentina) IM on the same day. On Day 4 after DIB insertion, superestimulatory treatment was initiated on a decreasing dose regimen of FSH (Pluset^®; Callier, São Paulo, Brazil, or Folltropin^®; Bioniche Animal Health, Inc., Belleville, Ontario, Canada) as IM injections every 12 h during 4 days. On Day 6, DIBs were removed, and cows received a double dose of 2 mL of cloprostenol within 12 h. At heat detection, all donors received a dose of 2 mL of GnRH (Dalmarelin; Von Franken, Buenos Aires, Argentina) by IM injection and were inseminated 12 and 24 h thereafter. Seven days later, embryo collection was performed and ovarian response was evaluated as number of CL + anovulatory follicles by transrectal ultrasound using a 7.5-MHz transducer (Pie Medical, Maastricht, The Netherlands). The condition score was determined at this time using a 1 to 5 scale. Embryos recovered were evaluated and classified according to the IETS manual. Kruskal–Wallis test was used to compare variables among score groups, and results are shown in Table 1. Ovarian response as the number of CL and anovulatory follicles was significantly different (P = 0.0001) among groups. There is a negative correlation (−0.2194) between condition score and ovarian response. At higher condition scores, ovarian response decreased. There is a significant difference (P = 0.0001) for the number of ovulations and total number of fertilized ova among groups. Finally, the total number of transferable embryos was no different for either score; however, there is a trend toward decrease when the condition score is higher. In conclusion, these results indicate that using donors with condition scores of 2 to 3 improves the results of a superstimulatory treatment. Controlling donors' condition score by nutrition management gives us the possibility to produce more embryos per donor treatment.

Table 1.  Condition score, ovarian response, fertilization, and transferable embryos in donor cows in Argentina