| Sumario: | The study was conducted to evaluate and compare the effect of single and double dose prostaglandin on estrus response and conception of crossbred (Holstein Friesian x Zebu) and local (Zebu) cattle in Eastern zone of Tigray, Ethiopia. The study also evaluated and compared efficiency of AI technicians to detect cuprous luteum through rectal palpation and reproductive status by progesterone level determination in milk using Rapid Progesterone Heat Detection Test (RPHDT). A total of 240 crossbred postpartum (>60 days) cows and heifers were assigned for single (group 1, n=120) and double (group 2, n=120) dose PGF2α protocols. Estrus response and conception rate was compared between protocols, breeds and parity. Reproductive stage of animals was confirmed prior to estrus synchronization and efficiency of AI technicians on detection of CL through rectal palpation assessed using RPHDT. Among cows/heifers synchronized using both PGF2α protocols, 87.2% (157/180) were detected in estrus on visual observation and rectal palpation. Overall conception rate among animals in heat was 62.7% (96/153). Out of the 120 cows/heifers synchronized using single dose PGF2α injection, 84.2% were detected in estrus with a conception rate of 59.6% (59/99). The overall estrus response rate of crossbred and local cattle was 84.2% and 93.3% in group 1 and group 2, respectively. No significant difference was found in estrus response between breeds in both groups. Conception rates in crossbred and local cattle in group 1 were 58.5% (31/53) and 60.9% (28/46), respectively. Whereas, the conception rates in local and crossbreds in group 2 were 63% (17/27) and 74% (20/27), respectively. No significant difference was found in conception rate between breeds in both treatment groups. The conception rates of cows and heifers in group 2 which were inseminated after heat detection and fixed time insemination were 68.5% (37/54) and 48.9% (23/47), respectively. The conception rate of cattle inseminated at detected heat was significantly higher (P<0.05) than those inseminated at fixed time. Among 90 animals milk progesterone level was determined using RPHDT prior to synchronization, 57% had high progesterone level, while 43% low progesterone. On average, one technician misclassified 4.6 cows out of 10 cows presented for corpus luteum detection through rectal palpation. In conclusion, the overall estrus response and conception rate in the study area was high. Single dose PGF2α protocol is recommended for estrus synchronization in cattle in the region as well as the country, as it is comparatively cost effective, has less number of visits to farms and less laborious. RPHDT can assist rectal palpation to evaluate reproductive stage of animals, hence provide proper breeding management. Refreshment trainings should be given to AI technicians on rectal palpation to improve detection of CL and subsequently improve reproductive performance of cattle in the region.
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