EVALUACIÓN ULTRASONOGRÁFICA POSTPARTO DE VACAS PRIMÍPARAS Bos taurus x Bos indicus (F1) EN EL TRÓPICO Ultrasonographic Evaluation During Postpartum of Primiparous Bos taurus x Bos indicus (F1) Cows at Tropic Conditions

Uterine involution (IU) and ovarian resumption (RAO) during postpartum period were evaluated by ultrasound technique in twenty F1 (Holstein x Brahman) lactating primiparous cows. Cows grazed Brachiaria brizantha. Complete mineral mix was offered ad libitum all time. Manual milking were applied twice a day (d) with calf presence and restricted suckling post both milking. Transrectal ultrasonography was applied (Sonoace Pico, lineal sound 5Mz) at 21 ± 4 post-partum d (DPP) until 93 ± 3 DPP with 14 d interval. Uterine cervix diameter (DCU) (mm) diameter of the horn uterine at involution for previous gestation (DCG) (mm) were measured to describe IU; number of different classes of follicles: follicles class 1 (FC1) ( 5mm), FC2 (6-9 mm); FC3 ( 10 mm) were used to evaluate RAO. DCU decreased at -0.24 mm/d ± 0.03 mm/d (R 2 ajust=0.41); DCU = 40.34 – 0.24 DPP (P<0.01) was the expression of lineal equation regression; for DCG lineal equation regression was 19.7 – 0.74DPP (R 2 ajus=0.07) (P<0.01). A statistical (P<0.01) increase of FC3 (0.08 ± 0.03 at 47 DPP vs. 0.76 ± 0.12 at 60 DPP) started at 60 ± 4 DPP. Almost, a dominant follicle appears, nevertheless calf presence two times daily. Non corpora lutea were observed until 93 DPP. It could be appear due to luteinizing hormone liberation problems. Concluding, ultrasound evaluation each 14 d lets record uterine changes during early postpartum in F1 primiparous cows. IU was complete between 34 and 47 DPP in primiparous cows at grazing and tropic conditions.