Usefulness of Rectal Palpation and Transrectal Ultrasonography in the Diagnosis of Gestation of the Zebu Cattle in the Humid Tropical in Costa Rica

The diagnostic efficacy of rectal palpation (RP) was compared to ecography (EG) in a natural mating program of Zebu cattle under Costa Rican tropical conditions. Grazing and lactating Bos indicus females, 98 each year (2005 and 2006) were divided in two groups, early (EP) and late (LP) postpartum. Two couples of bulls with proven reproductive ability were used in a rotation program. Each couple was with the cows for 21 day periods. At 23, 30, 37, 44, 51 and 60 days since the entry of the bulls, a transrectal EG was practiced to all cows; progesterone level was assessed by radioimmunoassay. At 35(th) day since the entry of the bulls, a RP by an expert veterinary practitioner was performed and repeated each week until 45 d after the last couple of bulls left. Sensitivity (Se), specificity (Sp) and predictive values (+PV and -PV) of the PR were determined using the EG as gold standard test; besides, these indicators were calculated to EG for each day of the pregnancy from the 20(th). The LP became pregnant earlier than EP. The average percentage of pregnancies for both years was 86.0%; in addition, the embryo mortality rate was 6.0%, there were not significant differences by year or postpartum group. RP at 30 days of pregnancy indicated a Se 94.0%, Sp 72.0%, +PV 93.2% and -PV 74.6%. The earlier day of higher diagnostic exactitude by EG was the 27(th) day (Se 93.2%, Sp 95.1%, +PV 95.1%). This study shows that the EG is a highly exact test to the early diagnosis of pregnancy (< 27 d) in Zebu cattle under natural matting programs, over of the RP. Cost-effectiveness studies should have to be done to assess its usefulness in a routine way in farms of zebu cattle.