The influence of ejaculate traits on strategies for Genome Resource Banking in tigers (Panthera tigris ssp.)

The Tiger Species Survival Plan has established a genome resource bank to store cryopreserved spermatozoa from all adult males from all three of the populations managed in U.S. zoos (Amur, Panthera tigris altaica , Sumatran, P.t. sumatrae , and Malayan, P.t. jacksoni ). We analyzed 104 ejaculates collected from 69 individuals (Amur n = 32, Sumatran n = 23, Malayan n = 14, ages 2 – 18 y, collected between 2013 and 2023). The results provided the opportunity to characterize reproductive traits of males in the current population and determine how the number of spermatozoa produced in a single collection will affect future strategies to maintain the GRB given current success rates for artificial insemination, in vitro fertilization, and embryo transfer. Semen was collected via electroejaculation, subjected to analysis, and cryopreserved. Total sperm count per ejaculate did not differ by subspecies (population average = 175.2 ± 22.5 ×10 6 ). Although most spermatozoa were motile (population average = 67.1 ± 2.2%), the number of morphologically normal was very low (average = 14.5 ± 1.0%). This percentage of normal sperm is much lower than that of previous studies of the North American population. For the genetics of each individual to be fully represented in a GRB, there must be sufficient spermatozoa to produce 10 offspring through assisted reproduction, which we estimate to be 30 procedures requiring 150 million motile spermatozoa if laparoscopic oviductal AI is used. Population managers must plan for frequent collections throughout the reproductive lifespan of the male. In addition, further studies of in vitro ART are warranted to maximize the potential of collected samples.