| This study evaluated the degree of synchrony and the rate of first service non-return to estrus achieved when using a progesterone intravaginal insert (CIDR-Pharmacia Animal Health), and a two injection system of progesterone-estradiol combination (ABS) and prostaglandin (ProstaMate- Rx Veterinarian Products) in conjunction with one 24 h timed breeding regimen. A total of 39 virgin beef heifers (N=39) of different breeds where provided by different consignors from different areas of east Texas. The heifers were developed to reach an average body score of 5.0. All heifers were assigned to a protocol that consisted of CIDR estrous synchronization and breeding via AI according to 24 h timed insemination. All heifers were equipped with an electronic HeatWatch RTM transmitter to aid in heat detection, and were exposed to a vasectomized Jersey bull equipped with a chin-ball marker.; The degree of synchrony and the rate of first service non-return to estrus were analyzed using the general linear model procedure and least square means analysis procedures of SAS (SAS Institute, Inc. Cary, NC) to determine if there was any significant difference for breed, average daily gain, and age at time of insemination. (Abstract shortened by UMI.)... |
