349 SUPEROVULATORY RESPONSE AND EMBRYO QUALITY RECOVERED FOLLOWING FLUSHING NGUNI HEIFERS AND COWS

Abstract

Most of the South African indigenous cattle breeds are facing genetic degradation due to unselective crossbreeding and irregular matings especially in small scale farming. The aims of the study were to compare superovulatory (SO) response, fertilization rate and to evaluate embryo quality recovered from superovulated Nguni stud cows and heifers. Nguni stud cows (n = 15) and heifers (n = 10) aged 4–6 and 2 years, respectively, were used as embryo donors for ex situ conservation. Nine days following heat observation for the first oestrus synchronisation protocol, superstimulation of donor cows and heifers were administered with a total of 350 mg of FSH (Follotropin-V^®, porcine pituitary glands extract) divided into 2 injections daily 12 h apart (6 a.m. and 6 p.m.) for 4.5 days on a decreasing dosage. Two injections of prostaglandin F_2α were administered on Day 3 and 4 of FSH injections. Semen was collected from 2 Nguni bulls (bull 1 and 2) and assessed by computer aided sperm analysis before artificial insemination (AI). The AI was conducted with fresh semen 3 times, 12 h apart, and the first AI was performed at the onset of oestrus. Semen from bull 1 was used to inseminate the cows, and bull 2 was used for heifers. Embryos were flushed 7 days after AI using a nonsurgical technique. Embryos were evaluated under stereo microscope and classified according to IETS standard codes (code 1, good and excellent; code 2, fair). Recovered embryos were then vitrified and stored for future use. Superovulatory response was measured by counting number of corpus lutea in each ovary. Data were analysed using 1-way ANOVA (SAS, 2003, SAS Institute Inc., Cary, NC, USA). There was no statistical difference between bull 1 (93.7%) and bull 2 (83.5%) on total sperm motility rate. Furthermore, no significant differences were recorded on fertilization rate between cows (67.5%) and heifers (53.5%). There was also no significant difference on the proportion of Nguni cows (40%) and heifers (40%) that responded to superovulation treatment. There was a significant difference on the ovary reaction (number of corpus lutea) of cows (11.3 ± 1.41) and heifers (4.0 ± 0.57). There were no significant differences recorded on the embryo quality recovered between Nguni cows (code 1, 2.5 ± 1.00; code 2, 1.3 ± 0.59) and heifers (code 1, 0.8 ± 0.41; code 2, 1.0 ± 0.36). However, cows had higher numbers of unfertilized ova than heifers (5.5 ± 1.05 and 1.8 ± 0.47, respectively) and degenerate embryos (3.7 ± 1.00 and 1.3 ± 0.39, respectively). Although superovulatory response of both Nguni cows and heifers was low, Nguni cows had higher ovarian response than heifers. Moreover, the quality of embryos recovered was similar for both Nguni cows and heifers.