CO-Synch as an economical fixed-time artificial insemination protocol to improve pregnancy rate in cow-calf production systems

Fixed-time artificial insemination (FTAI) protocols are a tool to increase the reproductive efficiency in beef herds, however their use in Mexico and worldwide is limited. The aim of this experiment was to compare the pregnancy per artificial insemination (P/AI), overall pregnancy rate (PR), follicular dynamics, and cost among beef cattle treated with three different FTAI protocols. A total of 191 females were assigned to CO-Synch (n=63), CO-Synch+CIDR (n=60) and estradiol/progesterone (n=68) protocols balanced by body condition scores (BCS). Females treated with the estradiol/progesterone protocol had higher (P<0.05) estrus presentation than females in the CO-Synch and the CO-Synch+CIDR protocol. P/AI tend to be higher (P<0.10) in cattle treated with the estradiol/progesterone protocol than females in the CO-Synch protocol, however overall pregnancy rate (PR) was similar among protocols (P>0.05). Diameter of largest follicle, number of dominant follicles (>= 6 mm) and percentage of females with a dominant follicle at prostaglandin F2-alpha (PGF2-alpha) injection were higher (P<0.05) in females of the CO-Synch protocol than females in the estradiol/progesterone protocol. Number of follicles from 2 to mm was higher (P<0.05) in females treated with the estradiol/progesterone protocol than females in the CO-Synch protocol. Cost of treatment in relation to total calves born, was higher in estradiol/progesterone and in the CO-Synch+CIDR protocols than the CO-Synch protocol.