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

Thesis Abstract

This study was conducted to investigate the effect of 45 and 60 minutes of exposure ofcrossbred (LW x Local) and exotic (LW) boars to tropical solar radiation on their bodytemperature pattern, libido, semen quality and haematological profile. 12 LW x Local and12 LW boars of 10 months old were used for the experiment. The experiment was carriedout 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 forthe boars to recover). The results showed that, in the exposure period, the rectaltemperature of the boars exposed to solar radiation significantly (P<0.05) increased from36.80 ± 0.360C to 41.88 ± 0.470C in LW x Local and 37.23 ± 0.360C to 42.04 ± 0.240C inLW boars and these changes varied significantly (P<0.05) between the durations of theexposure.The hyperthermic state of the exposed boars adversely affected the libido,semen quality and haematological characteristics. Specifically, the values for spermprogressive motility, sperm concentrations, sperm abnormalities, reaction time, andejaculation time were significantly (P<0.05) affected between genotypes and betweendurations of exposure to thermal treatments. The interactions effects of genotype andduration of exposure (G x D) were highly significant (P<0.01) in all these parameters.Total volume of ejaculate was significantly (P0.05) different between genotypes and between durations of exposure. Gx D interaction also had no significant effect on these parameters. Total ejaculate volumewas 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 significantlydifferent (P< 0.05) between genotype and between durations of exposure to thermalstress. G x D interaction significantly (P< 0.05) influenced these parameters. In therecovery phase, the two genotypes were reared under average ambient temperature of26.100C.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 afterwithdrawal of heat stress. The LW x Local boars recovered much more rapidly (30-40minutes) than LW (45 -60 minutes). The LW x Local boars recovered much faster thanthe LW in most of the semen quality and haematological traits under both durations ofexposure. The crossbred pigs retuned to their post exposure values from the 2nd week for