Effect of Heat stree on embryo productrion, Quality and Embryo transfer in Sistan Cattle.

The objectives of this study was a) to investigate the effect of season (summer vs winter) on superovulatory responses with varying amounts of FSH in Sistani cows and b) to compare the pregnancy rates achieved by transferring embryos collected and frozen in two seasons (summer and winter). In the first series of experiments, cyclic cows (n=16), in each season of summer and winter, with sound reproductive status, were assigned randomly to three treatment groups and received the total doses of 120 (n=5), 160 (n=6) and 200 (n=5) mg Folltropin-V, given twice daily over 4 days in a decreasing fashion. Estrous cycles were synchronized with two prostaglandin F2¦ء injections, 14 days apart. From Day 5 after ensuing cycle, daily ovarian ultrasonography was conducted to determine the commencement of the second follicular wave, when the superovulation was initiated. Relative humidity, environmental and rectal temperatures were measured at 0800, 1400 and 2000 h for 3 days before and 2 days after the superovulatory estrus. Females were inseminated at the time of standing heat and 12 hour later. Non-surgical embryo recovery was performed on Day 7 after standing estrus. Superovulatory responses were estimated as total number of CL and unovulated follicles (،ف10 mm) estimated by ultrasonography, and total numbers of ova/embryo, transferable and non-transferable embryos. Effects of season, dose of FSH and time of estrous expression and their interactions on the superovulatory response were also examined. There was no association between rectal and environmental temperatures in summerwhereas, in the winter season a positive correlation was detected between rectal and environmental temperatures (r=0.375P0.01). There was a significant rectal temperature fluctuation throughout the day (0800 h: 38.2،ہ0.05،مC1400 h: 38.7،ہ0.04،مC2000 h: 38.5،ہ0.04،مCP0.01) in winter that did not occur during summer (0800 h: 38.8 ،ہ 0.05 ،مC1400 h: 38.8 ،ہ 0.04 ،مC2000 h: 38.8 ،ہ 0.05 ،مCP0.05). The number of CL was influenced by the interaction of FSH doses and time of estrus expression (P0.001). The greatest number of CL was achieved at 2000 h for the 120 mg FSH (12،ہ1.35 CL), 1400 h for the 160 mg FSH (13،ہ1.35 CL) and 0800 h for the 200 mg FSH (12.2،ہ0.87 CL). There was also an interaction between FSH doses and the time of estrous expression on number of ova/embryos (P0.01). The dose of 200 mg FSH induced the greatest ova/embryo response at 0800 h (12.2،ہ1.46)whereas, the response was greatest at 1400 h for the 120 mg FSH dose (10.5،ہ1.97). In the second experiment, pregnancy rates of Sistani cows following transfer of frozen-thawed embryos recovered during summer and winter was investigated. During spring, summer and winter seasons, Sistani donor cows, with normal reproductive status, were superovulated and embryos were recovered non-surgically on Day 7 after superovulatory estrus. Grade A Blastocyst embryos were selected and either transferred fresh (spring) or frozen (summer and winter). Recovered embryos during summer and winter were exposed to glycerol (5 min at 5% followed by 10-15 min at 10% glycerol) and frozen using conventional method (slow cooling rates). During spring season, Sistani recipient females (n=70) were synchronized using two consecutive injections of prostaglandin, 14 days apart. On Day 7 after ensuing cycle, the females were assigned into three groups to receive single embryo, either fresh (n=14controlrecovered embryos in spring) or frozen blastocyst recovered and frozen in summer (n=27) or winter (n=29). Following thawing (15 sec in air followed by 15 sec in 35،مC water) and step-wise dilution (6, 3 and 0% glycerol in association with 10% sucrose), the embryos were transferred non-surgically. Pregnancies were diagnosed by ultrasound examination, 30 days after embryo transfer. Pregnancy rates were analyzed using Chi-Square test of SAS. Pregnancy rates of Sistani cows following transfer of fresh embryos (64.3%) were higher than those that received frozen-thawed embryos (17.86%P0.05). There was not any significant difference between pregnancy rates of recipients received embryos frozen in summer (18.5%) or winter (17.2%P0.05). In conclusion, season (summer or winter), different doses of Folltropin-V (120, 160, 200 mg NIH) and the time of estrous expression (0800, 1400 and 2000h) did not affect the ultimate number of transferable embryos (3.1،ہ0.58) in Sistani cattle. Pregnancy rates of frozen-thawed embryos were not influenced by season of the year (summer or winter) in which the embryos were recovered in Sistani cows.