Thesis Abstract

Abstract
The study aimed to investigate the growth performance and testicular characteristics of indigenous Nigerian native (NN) and exotic Large White x Landrace (EW) boars experimentally infected with a pathogenic strain of Brucella suis. A total of 24 boars (12 NN and 12 EW) were used in the study, with 6 boars of each breed designated to each of the two treatment groups infected and non-infected (control). The animals were monitored for a period of 12 weeks post-infection. Results showed that infected NN boars exhibited a significant decrease in average daily weight gain compared to the control group (P < 0.05). In contrast, the infected EW boars did not show a significant difference in weight gain compared to the control group (P > 0.05). Testicular measurements revealed a significant reduction in testicular size and weight in infected NN boars compared to the control group (P < 0.05). However, no significant changes were observed in testicular measurements of infected EW boars compared to the control group (P > 0.05). Histopathological examination of testicular tissues from infected NN boars revealed severe pathological changes, including necrosis, inflammation, and fibrosis. In contrast, testicular tissues from infected EW boars showed mild to moderate pathological changes. Immunohistochemical analysis demonstrated a higher expression of proinflammatory cytokines in the testes of infected NN boars compared to infected EW boars. Serum testosterone levels were significantly lower in infected NN boars compared to the control group (P < 0.05). In contrast, infected EW boars did not show a significant difference in serum testosterone levels compared to the control group (P > 0.05). The findings suggest that indigenous NN boars are more susceptible to Brucella suis infection compared to exotic EW boars, as evidenced by the negative impact on growth performance, testicular characteristics, histopathology, and hormonal profiles. The study highlights the importance of breed-specific responses to infectious agents and underscores the need for targeted control measures to prevent reproductive losses in swine populations.

Thesis Overview

Tolerance to African animal trypanosomosis (AAT) among several animal species involves awide milieu of factors which modulate the animal’s response to the disease and is considered abreed attribute. To investigate the effect of breed on tolerance/resilience to trypanosomeinfection on pubertal boars, nine (9) Nigerian Native and nine (9) Large-White x Landracecrossbreed boars were experimentally inoculated with laboratory samples of Trypanosoma

brucei brucei.

Their comparative responses with regard to clinical symptoms, growth parameters,histopathological and histometrical features of the testis, Sertoli and germ cell numbers andspermatogenic output including cell ratios and daily sperm production were studied over twostudy periods- 63 days post infection (63d p.i.) and 98 days post infection (98d p.i.). Resultsobtained indicated that infected boars of both breeds were clearly parasitaemic in the first studyperiod, with a significant (P<0.05) reduction observed in the native boars by 98d p.i. The generaltrend in the results obtained showed significant (P<0.05) differences in the various parameters,with the Nigerian Native boars exhibiting strong marginal gains by the second study period. Thiswas not the case with the exotic Large-White x Landrace boars and suggested that the nativeboars possessed a superior ability to mitigate the more severe effects of the pathology and atendency to return to normal. With respect to the clinical features investigated, the NigerianNative boars presented significantly (P<0.05) higher values with respect to parasitaemia logvalues, rectal temperatures, as well as packed cell volume. Histopathological findings revealedthat lesions, including tubular distortion, denudation of basement membrane, seminiferousepithelial damage led to the distortion of the architecture of the seminiferous epithelium as wellas degradation of the inter-tubular compartment and values were significantly (P<0.05) lower

among the native boars.

The parameters on growth showed the nutrient-parasite interaction wasinfluenced by breed attributes. Biometrical and linear body measurements were affectedsignificantly (P<0.05) less in the native boars than in the exotic boars. Weight loss wasminimized among the native boars with a tendency to significantly (P<0.05) increase growth rateas during the second study period, whereas this trend was not clearly observed among the exoticboars. The effect of the infection on clinical and histopathological features, as well as growthresponses and especially in relation to the testes’ capacity for spermatogenesis was studied. Weobserved significant (P<0.05) reductions in testes weight, somatic and germ cell populations andalso significant (P<0.05) reductions in the overall kinetics of spermatogenesis and daily spermproduction. The mechanisms of action implicated in breed responses to the pathology appearedto relate to phenotypic characteristics as well as innate mechanisms which are known tomodulate the pathogenesis of trypanosomosis. Equally the lowered parasitaemia observed amongthe native boars suggested that toxicological effects of trypanosomes on this breed of boars werelimited. It was concluded that the Nigerian Native boars possessed an attribute that could reversethe adverse patho-physiological effects of T. b. brucei infection and were therefore more resilient

to T. b. brucei infection than the exotic Large-White x Landrace boars.

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ABSTRACTTolerance to African animal trypanosomosis (AAT) among several animal species involves awide milieu of factors which modulate the animal’s response to the disease and is considered abreed attribute. To investigate the effect of breed on tolerance/resilience to trypanosomeinfection on pubertal boars, nine (9) Nigerian Native and nine (9) Large-White x Landracecrossbreed boars were experimentally inoculated with laboratory samples of Trypanosoma

brucei brucei.

Their comparative responses with regard to clinical symptoms, growth parameters,histopathological and histometrical features of the testis, Sertoli and germ cell numbers andspermatogenic output including cell ratios and daily sperm production were studied over twostudy periods- 63 days post infection (63d p.i.) and 98 days post infection (98d p.i.). Resultsobtained indicated that infected boars of both breeds were clearly parasitaemic in the first studyperiod, with a significant (P<0.05) reduction observed in the native boars by 98d p.i. The generaltrend in the results obtained showed significant (P<0.05) differences in the various parameters,with the Nigerian Native boars exhibiting strong marginal gains by the second study period. Thiswas not the case with the exotic Large-White x Landrace boars and suggested that the nativeboars possessed a superior ability to mitigate the more severe effects of the pathology and atendency to return to normal. With respect to the clinical features investigated, the NigerianNative boars presented significantly (P<0.05) higher values with respect to parasitaemia logvalues, rectal temperatures, as well as packed cell volume. Histopathological findings revealedthat lesions, including tubular distortion, denudation of basement membrane, seminiferousepithelial damage led to the distortion of the architecture of the seminiferous epithelium as wellas degradation of the inter-tubular compartment and values were significantly (P<0.05) lower

among the native boars.

The parameters on growth showed the nutrient-parasite interaction wasinfluenced by breed attributes. Biometrical and linear body measurements were affectedsignificantly (P<0.05) less in the native boars than in the exotic boars. Weight loss wasminimized among the native boars with a tendency to significantly (P<0.05) increase growth rateas during the second study period, whereas this trend was not clearly observed among the exoticboars. The effect of the infection on clinical and histopathological features, as well as growthresponses and especially in relation to the testes’ capacity for spermatogenesis was studied. Weobserved significant (P<0.05) reductions in testes weight, somatic and germ cell populations andalso significant (P<0.05) reductions in the overall kinetics of spermatogenesis and daily spermproduction. The mechanisms of action implicated in breed responses to the pathology appearedto relate to phenotypic characteristics as well as innate mechanisms which are known tomodulate the pathogenesis of trypanosomosis. Equally the lowered parasitaemia observed amongthe native boars suggested that toxicological effects of trypanosomes on this breed of boars werelimited. It was concluded that the Nigerian Native boars possessed an attribute that could reversethe adverse patho-physiological effects of T. b. brucei infection and were therefore more resilient

to T. b. brucei infection than the exotic Large-White x Landrace boars.