Experiments were conducted to determine the influence of reduced pressures during storage on the motility and fertility of fowl spermatozoa. The stocks used in these experiments were commercial White Leghorn birds. Semen was collected by a one-man technique from 18 to 24 males of less than one year old. The pooled semen was thoroughly mixed and 1m
l quantities were pipetted into specially designed flasks of about 110m
l capacity, each of which contained 3m
l of a phosphate buffer with antibiotics. After mixing, these flasks were placed directly into ice until brought to the laboratory. Each flask was connected to a vacuum system which consisted of a manometer, a glass chamber for minimizing the fluctuations of pressure, and a vacuum pump.
When the required pressure was achieved through pumping, a cock connected to the pump was closed to keep the pressure. While maintaining this pressure, the neck of the flask was then sealed with a gas flame and stored for 2 to 7 days at 0°C. The pressure is expressed as the height of a mercury colum (mmHg), 760mmHg representing 1atm. (absolute). After storage, the semen samples were taken from the flasks by cutting the flask's neck with a glass cutter. The samples were concentrated by centrifugation (2, 000 r.p.m. for 15min.) and resuspended to the volume at ejaculation with a phosphate buffer containing 4mg/m
l fructose. Eight hens in each treatment were inseminated vaginally with 0.1m
l of the reconstituted semen. Eggs were collected from the second through eighth day after insemination and incubated for 4 or 5 days.
When semen was stored for 2 days at 13, 25, 50, 100mmHg, and atmospheric pressure, average fertility was 98.1, 71.8, 92.0, 65.7, and 48.4%, respectively. In contrast, the motility of spermatozoa declined with decreasing pressure.
When semen was stored for 4 days at 13mmHg, addition of 4mg/m
l or 8mg/m
l fructose to a phosphate buffer before storage resulted in improved fertility (68.6 and 65.3% respectively) as compared to the buffer without fructose (29.5%). On the other hand, storage at atmospheric pressure gave low fertility (4.9%). No apparent difference in motilily was observed among these treatments.
An attempt was made to determine whether the fertilizing capacity of spermatozoa could be maintained for 7 days under 13mmHg. A hypertonic phosphate buffer (Δ=-0.93°C) was also compared with the isotonic buffer used in the above experiments. Storage with the hypertonic buffer resulted in negligible fertility regardless of addition of fructose, while a considerable fertility (26.0%) was obtained with the isotonic buffer containing 4mg/m
l fructose.
It is suggested that an environment of 13mmHg during storage of fowl semen is beneficial in the maintenance of the fertilizing capacity of spermatozoa held at 0°C and that under these conditions addition of fructose is necessary for the prolonged storage of semen.
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