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

Relationship between pH, other semen traits and
fertility in rabbits.

G.J. More 0'l~‘er'ra11,1 and T.N. Meacham.
Virginia Polytechnic Institute, Blacksburg 24061, U.S.A.

 

Observations during a study on spermatozoa separation
(More O'Ferrall, Meacham and Foreman, 1968) indicated that rabbit
semen quality varied considerably from one collection to another from
the same male as well as from different males. The semen quality
also appeared to be related to its pH. As semen volume, pH, motility
and total spermatozoa per ejaculate were recorded for each lot of
inseminations in the above study it was decided to examine the varia-
tion of these traits in more detail, and to investigate the
possibility of predicting fertility from a laboratory examination
of the semen and in particular from its pH, which is easily determined.

Semen was collected from eight New Zealand White bucks, using
an artificial vagina, three times a week (on alternate days) for
a period of four weeks. Following collection, the semen volume,
spermatozoa concentration, motility and pH of the semen were
determined and the total spermatozoa per ejaculate was calculated.
The pH was recorded on a Beckman zeromatic pH meter, while the
motility was estimated on a percentage basis, and converted to
a 0-6 scale for calculation purposes. A score of 6 was assigned
to semen samples with motility greater than 80%, and for each
decrease of 10% the score was dropped by 1, till those with a motility
of 25% or less were given a score of O. Seven of the bucks were
used for insemination of does over a 9 month period, the semen
evaluation being carried out in the 6th month of this period.
A minimum of 10 x 108 spermatozoa were used to inseminate each doe.
Fertility of the males was estimated as the percent of inseminated
does kindling (from 6-14 does were inseminated with each ejaculate
with a mean of 11.8); litter size is the mean size of litters sired
by each male, The means and standard errors of the semen traits
of each male, together with their fertility and mean size of litters
sired are given in table 1.

There were significant differences (P<0.05) between males for
the four semen traits and for fertility; the differences in litter
size were not significant. The standard errors indicate the large
variation in the traits from one collection to another.

The correlations among the four traits and their repeatab’i'ity
are given in table 2. All except the correlation between semen
volume and motility score were highly significant, although none of
them was very high. The correlations involving pH were all
negative indicating that low pH is associated with better semen
quality. The partial correlation between pH and motility, with

1 Present Address: Agricultural Institute, Castleknock, Ireland.

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