Comparison of Different Estrus Synchronization Protocols

Abstract

Genetic make-up of a cow herd is comprised by 50% of the bull’s genetic material, so genetic progress in herd improvement can quickly be made with usage of genetically superior bulls. Generally, commercial beef producers cannot afford to purchase truly “outstanding” bulls because they are expensive and can only breed about 40 cows per year. However, artificial insemination (a.i.) offers relatively inexpensive alternative with semen as cheap as $5 per breeding without the annual maintenance costs of bulls which can be $500 and higher. Further, different a.i. bulls can be used on specific cows to complement their deficiencies, such as lack of milking ability or lack of mature size, etc., and even by selecting sexed semen to select desirable traits for bull or heifer calves. There are several a.i. protocols, and we selected two for this experiment; a) short duration (33 d) and b) long duration (54 d). Longer duration generally results in more heifers exhibiting estrus at appropriate time. Heifers (n= 36) were randomly assigned to protocols, and treatments administered. Heifers were observed for estrus as per the protocol, and inseminated when appropriate. Those not exhibiting estrus were inseminated on the final day of the trial. Heifers were palpated about 60 days post a.i. treatment with conception rates as follows: short duration pregnant = 89%, and long duration pregnant = 89%. Conception rates were much higher than expected, and no differences due to treatment (16/18 for both treatments palpated pregnant) were observed.