The effect of storage on spermatozoa in vitro and the composition of the extender on the proportion of offspring from heterospermic insemination in the chicken.

Abstract

Summary. Spermatozoa from a Columbian (C) and a Leghorn (L) cock were stored at 4°C for 4 h before mixing in equal numbers for insemination. When hens were inseminated with either 100 × 106, 200 × 106 or 300 × 106 spermatozoa, the proportion of chicks sired by Cocks C and L was not affected (P > 0·05) by the total number of spermatozoa inseminated or the interval from insemination to oviposition (2–16 days). Cock C sired 61% of the chicks after the 4-h storage period. In a concurrent study Cock C was found to sire 34% of the offspring when fresh semen was used, indicating that the relative fertilizing ability of spermatozoa from different males does not change during storage in vivo, but may do so during storage in vitro. Ringer's solution (R) was compared to Locke's solution (O) in its ability to maintain the fertilizing ability of spermatozoa. Spermatozoa from Cocks C and L were stored in either R or O and then mixed in a 1:1 ratio in the four combinations: CR + LR, CO + LO, CR + LO, and CO + LR. When the same extenders were used for both cocks, i.e. CR + LR and CO + LO, differences between groups were not significant (P > 0·05) for the number of eggs collected, the % of eggs fertilized and the proportion of chicks sired by each cock. With the combinations CR + LO and CO + LR, the number of eggs collected, the % of eggs fertilized, and the number of chicks in the two groups were similar. The CR + LO combination resulted in 57% of the chicks being sired by Cock C, but the proportion of chicks sired by this cock rose significantly (P < 0·005) to 77% when the CO + LR combination was used. This 20% increase was presumably due to the advantage of storage in the O extender and indicates that appropriate heterospermic inseminations are more sensitive than homospermic insemination for evaluating treatments applied to semen.