Thawing boar semen in the presence of seminal plasma: Effects on sperm quality and fertility

Abstract

Causes of poor fertility after insemination of frozen-thawed (FT) sperm include reduced sperm viability at thawing and a shorter longevity of surviving sperm in the female genital tract due to sub-lethal damage. The present studies examined the effect of incubating thawed boar sperm in seminal plasma (SP) on sperm membrane integrity (viability), and motility in vitro (experiment 1), and fertility in vivo (experiment 2). For experiment 1, FT sperm from five individual boars and a sperm pool from these boars were thawed and incubated for 4 h in media containing 0%, 10%, or 50% autologous seminal plasma (individual boars) or pooled seminal plasma (sperm pool). At approximately 10 min (0 h) and again at 1 h, 2 h, 3 h, and 4 h, sperm populations were examined for percentage sperm viability and percent sperm motility. Each variable progressively decreased during the incubation period. Incubation in 50% SP increased percentages of live sperm ( P < 0.0001) and percent sperm motility ( P < 0.01) at all time points compared to incubation in either 0% or 10% SP. For experiment 2, multiparous Large white × Landrace sows ( n = 82) each received 900 IU eCG at weaning and 750 IU hCG 80 h later to control time of ovulation. Sows were assigned on the basis of parity to be inseminated with pooled semen with or without SP from the boars used in experiment 1. Sows received 3 × 10 9 live fresh-extended sperm ( n = 30) or FT sperm thawed in 80 mL BTS extender ( n = 26) or 3 × 10 9 live FT sperm thawed in 80 mL BTS containing 50% SP (FT-SP; n = 26). Sows were inseminated at 36 h, and 42 h after hCG injection. Compared to sows receiving fresh semen, the pregnancy rate of FT inseminated sows tended ( P = 0.06) to be lower with the FT-SP group being intermediate. Farrowing rates were not different (83.3%, 69.2%, and 65.4% for fresh, FT, and FT-SP, respectively). Inseminations with FT sperm were associated with a reduction in litter size ( P < 0.05), which was not evident in the FT-SP group. Taken together, these data confirm an adverse effect of inseminating FT sperm on sperm quality and sow fertility but suggest that thawing FT sperm in 50% SP may partially alleviate these adverse effects.