Rapid Methods for Estimating the Quality of Bull Semen

Abstract

New techniques for testing quality of bull semen have been developed which may be employed in field artificial insemination with the simplest of equipment. I. !~IOTILITY DURATION AT HIGH TEi~,IPERATURES A study was undertaken to determine the relation between the duration of spermatozoan motility in a nutrient-buffer diluter at a standard low tem- perature and the duration of spermatozoan motility from the same semen ejaculations in the same diluter at higher temperatures. To be most useful the high-temperature or incubation test should not require more than an hour. The desirable range of temperature for this purpose was established by an experiment in which semen, collected by means of the artificial vagina, from fertile bulls, was diluted at the rate of 1 : 4 with yolk-citrate (11), and was examined for motility at 15, 30, and 45 minutes, when stored at 2.5 ° C. intervals from 37.5 ° C. up to 47.5 ° C. The temperature of the water in the bath was controlled by mercury thermoregulators , mercury relays, and immersion heating coils. Ten ejaculations of semen were diluted and divided into 15 portions of about 1.0 ml. each. Three portions of each ejaculation, one for each motility examination, were stored at each of the five different temperatures. The motility estimations were made to the near- est 10 per cent, making 10 general classes of motility from 90 to 0. Willett and Salisbury (15) have shown this method of estimating motility to give highly repeatable results, and unpublished work of the present authors show the method to be highly accurate when compared with a more objective method of counting the number of motile spermatozoa in a dilute sample. The mean results are shown in figure 1. The data indicated that tem- peratures between 45.0 ° C. and 47.5 ° C. should be employed if the duration