Sperm cryopreservation reduces offspring growth

Abstract

Sperm cryopreservation is routinely used in reproductive medicine, livestock production and wildlife management. Its effect on offspring performance is often assumed to be negligible, but this still remains to be confirmed in well-controlled within-subject experiments. We use a vertebrate model that allows us to experimentally separate parental and environmental effects to test whether sperm cryopreservation influences offspring phenotype under stress and non-stress conditions, and whether such effects are male-specific. Wild brown trout (Salmo trutta) were stripped for their gametes, and a portion of each male's milt was cryopreserved. Then, 960 eggs were simultaneously fertilized with either non-cryopreserved or frozen-thawed semen and raised singly in the presence or absence of a pathogen. We found no significant effects of cryopreservation on fertilization rates, and no effects on growth, survival nor pathogen resistance during the embryo stage. However, fertilization by cryopreserved sperm led to significantly reduced larval growth after hatching. Males varied in genetic quality as determined from offspring performance, but effects of cryopreservation on larval growth were not male-specific. We conclude that cryopreservation causes a reduction in offspring growth that is easily overlooked because it only manifests itself at later developmental stages, when many other factors affect growth and survival too.

Keywords: assisted reproductive technology; fish; good genes; infection; sperm cryopreservation; vertebrate.

Figure 1.

Effect of cryopreservation on sperm quality indicators: (a) motility (paired t-test: t₁₄ = 12.1, p < 0.001), (b) percentage of fast progressive sperms (t₁₄ = 9.7, p < 0.001) and (c) the average path velocity VAP (t₁₄ = 2.3, p = 0.04). (d) The fertilization success of the 40 males used in the breeding experiment, based on 2 × 12 eggs per male (see table 1a for statistics). Plots show means and 95% confidence intervals for non-cryopreserved sperm (empty bars or symbol) and cryopreserved sperm (filled bars or symbol). Asterisks indicate the levels of significance (***p < 0.001; *p < 0.05; ‘n.s.’, not significant).

Figure 2.

Effects of (a,c) sperm cryopreservation and (b,d) exposure to pathogen on (a,b) larval length at hatching and (c,d) larval growth during 14 days after hatching. The figure gives the means and 95% CI (based on family means) and the total number of larvae that could be measured per treatment group. Asterisks indicate the levels of significance (***p < 0.001; *p < 0.05; ‘n.s.’, not significant). See table 2a,c for statistics.