Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2009
Publication Date: N/A
Interpretive Summary: Cryopreserved chicken sperm from commercial lines retain < 2% of the fertilizing capacity of fresh semen. As part of a systematic evaluation of poultry sperm physiology and function after cryopreservation, we conducted a large-scale study to determine the influence of genetic selection on the success of semen cryopreservation by evaluating the ‘freezability’ of semen from individual roosters from multiple males within and across pedigreed lines. We found several differences among lines that have implications for the success of cryopreservation of chicken semen, including age of the male and cryoprotectant type. These data have permitted development of a model to study the cryosurvival of rooster sperm.
Technical Abstract: The fertility rates of cryopreserved poultry semen are highly variable and not reliable for use in commercial production or preservation of genetic stocks. The objective of the present work was to compare semen from 7 pedigreed layer lines before and after cryopreservation. A total of 140 roosters (20 males/line) were used as semen donors at 6, 9 and 12 mths of age. Prior to cryopreservation, semen from each male was assessed for sperm motility (sperm mobility assay), sperm viability (SYBR-14/PI), and ATP content. Semen from each male was frozen individually 1) in straws with 11% glycerol and 2) as pellets with 6 % DMA as the cryoprotectant. Glycerol was removed from thawed semen by Accudenz gradient centrifugation; DMA was not removed from thawed semen. For pre-freeze analysis, sperm viability was consistent within line at 6, 9 and 12 mths of age; while sperm ATP values were similar among age groups for 3/7 lines. For the remaining 4 lines, ATP values were lower in sperm from 12-mth old males. The highest sperm mobility values for 4/7 lines were observed at 12 mths of age and sperm mobility was not correlated with ATP content. For all lines, sperm viability was greater for semen frozen with glycerol than DMA. For most lines, ATP content was greater in sperm frozen with glycerol; however, ATP content was higher for sperm from 3 lines that were frozen with DMA. Fertile eggs were obtained from some hens as long as 14 days after a single AI with frozen/thawed semen; however, the highest fertility rates occurred 2 days after AI. The fertility of frozen/thawed semen from pedigreed lines varied with respect to freezing method and age of male. These results demonstrate that there is variability in fresh and frozen/thawed semen characteristics among these pedigreed lines.