Quantifying the use of and the genetic progress from advanced mating strategies in US dairy herds

The use of mating technologies, including genomic testing and sexed semen, has recently increased in the breeding programs of commercial dairy herds, along with the use of beef semen. We aimed to quantify the use of advanced mating strategies in US dairy herds and the influence of these strategies on genetic merit. Breeding records (n = 35,124,479) that resulted in successful pregnancies of cows and heifers by semen type (conventional dairy, sexed dairy, and beef) and records of genomic testing of female dairy cattle were extracted from the National Cooperator Database for the years 2008 to 2023. Herds were categorized within year by semen type used and use of genomic testing of heifers, and the genetic merit of heifers born in 2023 (n = 678,064) was compared by herd mating strategy. Female dairy cattle in the United States are genotyped, on average, at 6 mo of age. When the net merit of a genotyped heifer increased by 1 SD, the odds that she remained in the herd through first lactation increased by 13%. Breeding values of net merit ($1,203) and most of the traits investigated were most favorable in heifers born in herds that used all mating strategies investigated (genotyping of heifers as well as a combination of beef, sexed, and conventional semen). Calves born in herds that used a combination of sexed and conventional semen had the least net merit ($532) and generally had the least favorable breeding values across production, fertility, and longevity traits. However, calves born in herds that genotyped heifers and used a combination of sexed and conventional semen had the greatest genetic merit for the conformation composites of udder and feet and legs. Results suggest that farms are primarily genotyping heifers and that the genomic merit of a heifer influences the probability that she is kept in the herd through first calving. Herds that used multiple mating technologies generally had heifers with more favorable genetic merit across selection indexes and most traits investigated. The breeding objectives of herds that use a combination of sexed and conventional semen in their mating programs appear to focus on improvement of conformation traits, whereas herds using other breeding strategies investigated appear to select for many economically relevant traits.