Abstract
A deterministic simulation was conducted to assess the effects of sexed semen utilization strategies on age at first calving (AFC). Four different strategies were implemented on dairy heifers: continuous use of conventional semen only (CC), continuous use of sexed semen only (SS), utilization of sexed semen for both the first and second services with conventional semen afterwards (S2), and utilization of sexed semen for the first service with conventional semen afterwards (S1). Results indicated that continuous utilization of sexed semen led to the greatest AFC; however at high conception rates, strategies displayed negligible differences on AFC. Increases in estrus detection rate had the greatest effects on decreasing AFC of the SS scenarios. Negative effect of sexed semen on AFC increased when the effect of low estrus detection rate was combined with low conception rate of sexed semen. Results indicated that in the case of access to sexed semen conception rate, prediction of AFC is possible by quadratic polynomial or exponential equations, depending to the applied breeding strategy. Simultaneous utilization of sexed and conventional semen in a herd did not make a substantial change in AFC when a low percentage of sexed semen was employed. Increasing the contribution of different sexed semen strategies led to higher AFC variation, especially for the SS strategy. AFC of strategies that utilize sexed semen is highly dependent on the conception rate, estrus detection rate and the contribution of sex sorted semen in the total number of inseminations of the heifer herd.
Highlights
The beginning of a cow’s productive life is marked by age at first calving (AFC)
Lower AFC after the continuous use of sexed semen strategy resulted from lower pregnancy rate in the 3rd and 4th services (15 and 10%) in contrast with S2 strategy (21% and 12% pregnancy rate at 3rd and 4th services)
The results showed that the utilization of any sexed semen strategy increased the AFC
Summary
The beginning of a cow’s productive life is marked by age at first calving (AFC). An optimum AFC is desired because an increase in AFC is associated with heifer rearing expenses and leads to increased generation interval and decreased life production (Mohd Noor et al, 2013). A reduced AFC may cause productive and reproductive problems for heifers (Mohd Nor et al, 2013). Flow cytometry is the most common procedure for separating bovine sperm bearing X vs Y chromosomes (Seidel & Garner, 2002; Weigel, 2004). The reliability of separating males vs female sperm by flow cytometer varies among different sires at a range from 85 to 95% (Garner & Seidel, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
