Vle CONG. INTERN. REPROD. ANIM. INSEM. ARTIF.,, PARIS, 1968, VOL. I

THE EFFECTS OF FREEZING METHOD ON SPERM
FROZEN IN PLASTIC STRAWS

J, W, MACPHERSON, S, CHATTERJEE, and G, J. KING,
Department of Animal Science, University of Guelph,
Guelph, Ontario, Canada,

Bovine semen samples have been routinely frozen for storage
and subsequent insemination in both ampoules and plastic straws with
satisfactory results, The advantage of the plastic straws for
storage are obvious because of the reduced space requirements, We
have observed great variation in both laboratory and field results
in samples frozen in nitrogen vapour as compared to those frozen in
an alcohol bath when the semen was packaged in glass ampoules,
This study was designed to compare by laboratory methods the effects
of freezing semen packaged in plastic straws when frozen by the two
methods,

MATERIALS AND METHODS, A split sample technique was used to compare
seventy ejaculates of bovine semen, two of which were collected from
each of thirty-five bulls, One ejaculate was processed in milk
extender (1) and the second was processed in Minn Go (2). The

semen was packaged in ,5 ml, plastic straws with portions of all
ejaculates in glass ampoules as controls,

Freezing was carried out,after four hours equilibration, in the
vapour above liquid nitrogen and in a programmed temperature
controlled alcohol bath, Frozen samples were stored in liquid
nitrogen for one week after which they were thawed in cold water
and immediately examined for live spermatozoa by the method of
Hackett (3)., Examination was repeated by the same method on
portions of the samples following incubation at 37°C, for five hours,

RESULTS, The mean per cent of live spermatozoa for samples in straws
frozen in nitrogen vapour was 13,76 before incubation and 10,33
following incubation, For the same samples in straws frozen in the
alcohol bath the mean per cent recovery rates were 28,91 before
incubation and 22,47 after incubation, No differences were

observed between extenders, Analysis of the data, Table 1, showed
that the difference in per cent live spermatozoa between the straws
frozen in nitrogen vapour and those frozen in the alcohol bath was
significant in favour of those processed in the alcohol bath,

The control semen packaged in glass ampoules and frozen in the

alcohol bath had mean recovery rates of 25,36 per cent before
incubation and 20,10 after incubation,

1085