Abstract #202

# 202
Evaluation of conception rates of sex-sorted semen in commercial dairy farms over the last five years.
C. Heuer*1, D. Kendall1, C. Sun1, J. Deeb1, J. Moreno1, R. Vishwanath1, 1ST Genetics, Navasota, TX.

The objective of this study was to investigate the development of sexed semen conception rates in the field and compare those to the conception rates of conventional semen over the last 5 years (2012–2016). Conception rates were estimated for conventional and sexed semen using field data from 63 commercial dairy farms. In this period, sex-sorted semen underwent many significant changes with the introduction of SexedULTRA processing as well as improvements through the use of high throughput digital sorting technology. The total numbers of inseminations in the data set were 2,214,246 for conventional and 343,154 for sexed semen from 2,508 Holstein sires. The percentage of sexed semen used in those herds increased from 8% in 2012 to 23% in 2015. A linear mixed model was fitted to the data that included an interaction term between year-month of insemination and semen type, the insemination number (1–3) and the age of the service sire at the time of insemination. Random effects included the service sire and a herd-year-season of insemination effect. The model was fitted separately for heifers and cows, whereas the cow model included the lactation number (1–3) as additional fixed effect. Least squares means (LSM) on the interaction between year-month and semen type were used to describe the changes in conception rates over time while averaging over the remaining fixed effects. The cow conception rates showed strong seasonality which is consistent over years with any semen type. That seasonality was not observed in heifers. The LSM conception rate in cows in January 2012 was 0.38 while sexed semen reached 0.25. In heifers this difference in conception rates was even more pronounced with 0.58 using conventional and 0.38 with sexed semen. Through the years the technological and biological advances in sexed semen processing that were introduced seems to have improved the conception rates starting in 2013. In June 2014 conventional and sexed semen conception rates were almost at the same level for the first time (0.34 and 0.33). In 2015 the conception rates of sexed semen were stable and at 0.88 and 0.86 of conventional semen conception rates in cows and heifers, respectively.

Key Words: sexed semen, conception rates, fertility