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SEMEN QUALITY AND HAEMATOLOGICAL CHARACTERISTICS OF EXOTIC AND CROSSBRED BOARS EXPOSED TO DIFFERENT DURATIONS OF THERMAL STRESS IN THE HUMID TROPICS

ABSTRACT
This study was conducted to investigate the effect of 45 and 60 minutes of exposure of
crossbred (LW x Local) and exotic (LW) boars to tropical solar radiation on their body
temperature pattern, libido, semen quality and haematological profile. 12 LW x Local and
12 LW boars of 10 months old were used for the experiment. The experiment was carried
out in the Piggery Unit of the Department of Animal Science Farm, University of Nigeria,
Nsukka for a period of eight weeks (4 weeks for the exposure and, another 4 weeks for
the boars to recover). The results showed that, in the exposure period, the rectal
temperature of the boars exposed to solar radiation significantly (P<0.05) increased from
36.80 ± 0.360C to 41.88 ± 0.470C in LW x Local and 37.23 ± 0.360C to 42.04 ± 0.240C in
LW boars and these changes varied significantly (P<0.05) between the durations of the
exposure.

The hyperthermic state of the exposed boars adversely affected the libido,
semen quality and haematological characteristics. Specifically, the values for sperm
progressive motility, sperm concentrations, sperm abnormalities, reaction time, and
ejaculation time were significantly (P<0.05) affected between genotypes and between
durations of exposure to thermal treatments. The interactions effects of genotype and
duration of exposure (G x D) were highly significant (P<0.01) in all these parameters.
Total volume of ejaculate was significantly (P<0.01) higher in LW boars than LW x
Local, while volume of gel-fraction, strained ejaculate and semen pH were not
significantly (P>0.05) different between genotypes and between durations of exposure. G
x D interaction also had no significant effect on these parameters. Total ejaculate volume
was not significantly (P<0.05) affected by durations of exposure and G x D interaction.
Erythrocyte count, PCV, Hb concentration, MCV, MCH and MCHC were significantly
different (P< 0.05) between genotype and between durations of exposure to thermal
stress. G x D interaction significantly (P< 0.05) influenced these parameters. In the
recovery phase, the two genotypes were reared under average ambient temperature of
26.100C.

They returned to their normal body temperature of 37.00 ± 0.190C and 36.97
±0.200C for LW x Local and LW boars respectively within period of one hour after
withdrawal of heat stress. The LW x Local boars recovered much more rapidly (30-40
minutes) than LW (45 -60 minutes). The LW x Local boars recovered much faster than
the LW in most of the semen quality and haematological traits under both durations of
exposure. The crossbred pigs retuned to their post exposure values from the 2nd week for