Quantitation of the fertilising ability of fresh compared with frozen and thawed fowl spermatozoa

Abstract

1. The fertilising abilities of freshly‐diluted and frozen and thawed fowl semen were compared by inseminating a wide range (0.2 to 1600×10⁶) of doses of spermatozoa. 2. These data demonstrated that there was a non‐linear relationship between numbers of spermatozoa and the probability of fertilisation. 3. It was concluded that a typical fertility trial, which assesses the percentage of fertile eggs laid by groups of hens inseminated with a fixed dose of semen, was inadequate for comparing the quality of semen samples. 4. An alternative fertility trial is described, which involves assessing the numbers of spermatozoa required to fertilise a particular percentage of eggs laid. 5. This modified method showed that the quality of frozen and thawed semen, in terms of its fertilising ability, was reduced to 1.6% of that of fresh semen.