Evaluación de tratamientos con implantes de norgestomet más PMSG para el control del anestro postparto en vacas mestizas

To stablished the efficiency of the treatments using Norgestomet implants plus PMSG for anestrous control, a retrospective study was conducted using records from 1993 to 1998 of 222 crossbred cows (Bos taurus x Bos indicus) in anestrus. One hundred and twenty two animals were treated with Norgestomet implants (3mg + 3mg Norgestomet and 5mg Estradiol Valerate in 2ml solution when the implant was placed) per 9 days, plus an inyection of PMSG (500 I.U.) on the day of implant removal (implant group). One hundred were in a control group without any treatment. The dates of treatment for the cows in the control group were the same as in the treatment group, according to the month and year of calving. The studied variables were: Treatmen Efficiency (ET) as estrus response to induction with implants, Treatment-First Service Interval (ITS), Treatment-Conception Interval (ITC), Fertility at First Service (F1S) and Fertility at Second Service (F2SE). ET was 58.2% (71/122) of estrus response and 41.8% (51/122) estrus as non-response; with significant differences (P < 0.05, Chisquare). Neither Breed nor Parturation, not even Milk Production showed significant effects en ET. ITS was 29.8 ± 4.0 days in implant group and 55.1 ± 3.8 days in control group (P < 0.001). ITC was 28.7 ± 4.4 days in implant group and 70.9 ± 4.7 days in control group (P < 0.001). F1S was 58.3% (67/115) and 54% (54/100) in implant and control groups respectively. F2S was 60% (24/40) and 57.8% (19/45) in implant and control groups. Both F1 S and F2S did not show statistical differences for implant and control groups. It was concluded that using norgestomet implants combined with PMSG in anestrus crossbred cows is effective, in shorting the interval to estrus and to conception, and obtaining a good fertile estrus induction.