The hydrogen-ion concentration of the vaginal secretion of merino sheep during oestrus, dioestrus, and pregnancy, with some remarks on its influence on sex-determination, and the influence of the vaginal temperature at the time of mating on conception

Abstract

(1) The pH of the vaginal secretion of mature merino ewes, measured during oestrus, gave a mean value of 6·648, with a range of 5·85 to 7·40. During mid-dioestrus the mean value was 6·694, with a range of 6·00 to 7·60. During pregnancy the mean value was 6·272, with a range of 6·00 to 7·00. There are indications that there is a tendency to slightly increased acidity during oestrus and pregnancy. (2) There are indications that there is a slight tendency for male offspring to be associated with a pH approaching neutral or alkaline measurements. (3) The percentage fertility was higher with pH measurements below 7 (82·51 per cent.) than with those above 7 (73·18 per cent.). There are indications that an alkaline medium may be detrimental to the vitality of the spermatozoa in the vagina when pregnancy is used as an indicator. (4) Forced exercise increased the vaginal temperature of ewes when they are compared with ewes, kept under similar environmental conditions, which were allowed voluntary exercise. (5) The temperature of the vagina (within a range of 100·2°F. to 106·2°F.), at the time of mating or artificial insemination did not influence the sex of the lamb. (6) The temperature of the vagina, within a range of 100·2°F. to 106·2°F., did not make a significant difference in the resulting pregnancies in three groups of sheep with mean temperatures, at 1st and 2nd matings or artificial inseminations, of: (1) 103·286, 103·264, (2) 103 ·244, 103·096, and (3) 104·017, 104·108 (temperatures are recorded in °F.). (7) The gestation period, for 79 normal pregnancies in merino sheep, showed a range of 146 to 156 days, with an average of 151·4 days.