Sperm morphology and fertility in the dog.
Normal and abnormal dog spermatozoa were studied by means of bright field light and transmission electron microscopy and the effect of abnormal spermatozoa on dog fertility was evaluated. Semen samples were collected by digital manipulation from 67 dogs of 34 different breeds. Ten of the samples were examined ultrastructurally. The association between the percentage abnormal spermatozoa in the ejaculate and the fertility of the dog was statistically evaluated, based on insemination of 42 bitches. On this basis, the male dogs were divided into normal and subnormal groups. The percentage normal morphology below which fertility was adversely affected was found to be 60%: the fertility of dogs with > 60% normal morphology was 61% (14 of 23 inseminated bitches) whereas the fertility of dogs with < 60% normal morphology was 13% (two of 15 inseminated bitches). There was no statistical difference between the ages of the dogs in the two groups; from this it was concluded that subfertility may affect a dog at any age.