RESUMO
Manual and ultrasonic evaluation of the the reproductive organs of 62 dairy cows and heifers belonging to smallholder farms was conducted. The objective was to assess the efficiency of visual estrus detection method in the dairy animals that were presented for artificial insemination. Data were collected on reproductive status, body condition, estrus signs, and findings of rectal examination. Thirty-three animals were inseminated after ultrasonic evaluation while 29 animals were inseminated after manual evaluation through rectal palpation. Pregnancy diagnosis was performed using ultrasound 30 days post insemination. The most frequently observed estrus signs by the dairy owners were mucus discharge (83.9%) and mounting (67.7%) while the most frequently confirmed physical signs of estrus by rectal examination were cervical opening (88.7%), and uterine turgidity (82.3%). The overall mean (±SD) diameter of the largest follicle was 12.9 ± 3.4 mm with an average number of 3.5 follicles per ovary. The overall pregnancy rate was 29%. Evaluation of post-insemination records showed a significant difference (P < 0.05) in the diameter of largest follicle between the pregnant (14.7 mm) and non-pregnant (12.1 mm) animals. The mean (±SD) time interval between the first observed estrus sign to service were 10.5 ± 7.0 hrs and 14.5 ± 10.0 hrs for pregnant and non-pregnant, respectively. The low pregnancy rate, delayed time of insemination, and the difference in the size of dominant follicle indicate the incompatibility between visual estrus detection and optimal time of insemination. This confirms the significance of improving estrus detection and the need for combining estrus signs with pre-service evaluation of the reproductive organs either manually or using ultrasound.