Production and preservation of boar spermatozoa.

The use of artificial insemination for breeding pigs has developed slowly over the past few years within the United Kingdom. Future development will depend to a large extent, on the ability to maintain and improve on the present conception rates, by improved techniques for the preservation in vitro of boar spermatozoa. This dissertation examines the production, and the methods of preservation of boar spermatozoa. In Section I, the production of spermatozoa is reviewed, from the division of the germ cells within the seminiferous epithelium, through the various stages of development, to the maturation of the spermatozoa within the epididymis. Variation in sperm production rates and sperm output are related to age and strain of boar, ejaculation frequency and environ­mental temperature. These aspects are examined, as are the methods of collection of semen from the boars and the laboratory examination of the spermatozoa. In Section II, a review is undertaken of the methods of extending the life of the spermatozoa when stored in vitro. The advantages of storing spermatozoa 'fresh' as opposed to 'frozen' are discussed, and the various diluents used for storing spermatozoa by each method are examined. The freezing of boar spermatozoa has presented more difficulties than the freezing of bull spermatozoa. The various procedures involved with freezing, including the effects of glycerol, 'holding time' and the use of surfactant agents are investigated. Two experiments are reported. The 1st. experiment investigates the relationship of morphological abnormalities of spermatozoa to conception rates and litter size. The 2nd. experiment examines the effect on acrosomal integrity of the various stages involved with cooling and freezing the spermatozoa