PREGNANCY PER AI OF HIGH PRODUCING HOLSTEIN COWS TREATED WITH NORGESTOMET EAR IMPLANT OR PROGESTERONE INTRAVAGINAL DEVICE
The aim of present study was to compare pregnancy per AI (P/AI) of high producing Holstein cows subjected to timed artificial insemination (TAI) using a new or previously used progesterone intravaginal device or a Norgestomet ear implant. In Experiment 1, 359 cows (173 primiparous and 186 multiparous) received 2 mg estradiol benzoate i.m. (Gonadiol, MSD Animal Health, Brazil) at random days of the estrous cycle (D0) and were homogenously distributed in two groups. Cows on group NEW-PROGESTERONE received a new progesterone releasing intravaginal device (CIDR, Zoetis, Brazil), while cows on group NEW-NORGESTOMET received a new Norgestomet ear implant (Crestar, MSD Animal Health, Brazil). On D8, 500 mg Cloprotenol (Ciosin, MSD Animal Health, Brazil) and 1 mg estradiol cypionate (E.C.P., Zoetis, Brazil) were administered and the ear implants or intravaginal devices were removed. On D10, 100 μg gonadorelin (Fertagyl, MSD Animal Health, Brazil) was administered and TAI was performed 10h later. In Experiment 2, 293cows (146 primiparous and 147 multiparous) were subjected to the same experimental design described above except for using implants and devices previously used for eight days (USED-PROGESTERONE = 146 cows vs. USED-NORGESTOMET = 147 cows). The experimental period began in May and ended in September 2012. Statistical analyses were performed using logistic regression (PROC GLIMMIX of SAS). There were no interactions for treatment and parity, farm, and times in bred. The P/AI 30d after TAI was similar (P > 0.10) between groups NEW-PROGESTERONE [31.6 % (50/158)] and NEW-NORGESTOMET [35.3 % (71/201)], and between groups USED-PROGESTERONE [35.6 % (52/146)] and USED-NORGESTOMET [36.7 % (54/147)]. These results indicate that both CIDR and Crestar, either new or previously used for eight days, can be used for TAI treatments producing similar P/AI.
Keywords: Norgestomet, pregnancy per AI, Holstein