Sincronização do ciclo estral em vacas nelore com prostaglandi na F2-alfa análoga (ICI-80.996, Cloprostenol) por via intramuscular

Abstract

The objective of this study is to determine the efficiency of PGF2-OL analogue (Cloprostenol, ICI-80.996) in the synchronization of the estrous cycle and the fertility level in Nelore cows from a farm adjacent to Londrina, Paraná State. On the first day of the trial, 132 cows were selected after genital examination, the majority of them, 7 to 9 months after parturition and the rest barren during the previous year. These animals were distributed at random into three groups of 44 each. Groups I and II received two doses of 0.5 mg of Cloprostenol through intramuscular route 11 days apart. Group I animals were inseminated twice at 72 and 96 hours after while those in group II were inseminated once, aproximately 12 hours after the heat detection by teaser bulls with chin-ball. The third group received no treatment and served as control, following the same scheme as group II over a fixed period of 21 days. The results obtained were as follows: Group I - without having any concern over the symptoms of heat, 24 (54,54%) cows became pregnant and from the other 20,70% repeated a normal cycle. Group II-between the 2nd and the 8th day, 42 (95,45%) cows showed signs of heat and were inseminated, 15 of them (34,09%) became pregnant and from the 27 animals that were not pregnant 18 (66.66%) returned to heat 19 to 22 days later, confirming the data observed in the previous group. Group III - heat and insemination rates of43 (97.72%) cows resulted in 16 (36.36%) pregnancies while rest of the animals returned to the regime of natural service. The conception rate between groups were not significantly different (P > 0.05).