Publications

Body growth, feedlot performance and carcass characteristics of ram lambs (n=16) immunized against luteinizing hormone-releasing hormone (LHRH) at 10 weeks of age with recombinant LHRH fusion proteins were investigated. Recombinant fusion proteins, ovalbumin–LHRH-7 and thioredoxin–LHRH-7 were produced using recombinant DNA technology. Animals were immunized (n=8) against LHRH with ovalbumin–LHRH-7 and thioredoxin–LHRH-7 recombinant protein mixture in the Freund’s complete adjuvant. The immunization group received two booster injections 4 and 8 weeks later, with Freund’s incomplete adjuvant. Animals in control group (n=8) were not treated. Animals were kept at relatively poor pasture until 27 weeks of age. This was followed by a 70 days finishing period that involved housing in groups and ad libitum feeding with concentrate. Carcasses were evaluated after chilling for 24h at +4°C. Live weights, finishing weight, weight gain and average daily weight gain were similar between groups (P>0.05). Carcass measurements, loin eye muscle area and back fat thickness were not affected from immunization. Immunization did not affect hot and cold carcass weights, dressing percentage, offal items and wholesale cuts weights. Immunized animals had smaller testis, chop and bone weights than control animals (P<0.05). It was concluded that immunological castration could be achieved at 10 weeks of age in ram lambs using new recombinant LHRH fusion proteins and used in finishing programs without adverse effect on growth rate, feedlot performance and carcass characteristics. Nevertheless, the effectiveness of these proteins should be further evaluated with more animals.

Body growth, feedlot performance and carcass characteristics of ram lambs (n=16) immunized against luteinizing hormone-releasing hormone (LHRH) at 10 weeks of age with recombinant LHRH fusion proteins were investigated. Recombinant fusion proteins, ovalbumin–LHRH-7 and thioredoxin–LHRH-7 were produced using recombinant DNA technology. Animals were immunized (n=8) against LHRH with ovalbumin–LHRH-7 and thioredoxin–LHRH-7 recombinant protein mixture in the Freund’s complete adjuvant. The immunization group received two booster injections 4 and 8 weeks later, with Freund’s incomplete adjuvant. Animals in control group (n=8) were not treated. Animals were kept at relatively poor pasture until 27 weeks of age. This was followed by a 70 days finishing period that involved housing in groups and ad libitum feeding with concentrate. Carcasses were evaluated after chilling for 24h at +4°C. Live weights, finishing weight, weight gain and average daily weight gain were similar between groups (P>0.05). Carcass measurements, loin eye muscle area and back fat thickness were not affected from immunization. Immunization did not affect hot and cold carcass weights, dressing percentage, offal items and wholesale cuts weights. Immunized animals had smaller testis, chop and bone weights than control animals (P<0.05). It was concluded that immunological castration could be achieved at 10 weeks of age in ram lambs using new recombinant LHRH fusion proteins and used in finishing programs without adverse effect on growth rate, feedlot performance and carcass characteristics. Nevertheless, the effectiveness of these proteins should be further evaluated with more animals.

Antigen recognition patterns (Western blotting) and lymphoproliferative response (local and peripheral) have been determined in lambs immunised and partially protected against haemonchosis with p26/23, a purified somatic fraction of Haemonchus contortus. Immunoprotective response induced by p26/23 was accompanied by both specific lymphoproliferative response and serum anti-Haemonchus antibodies. Western blotting showed an extensive reactivity of sera from p26/23 vaccinated lambs with peptides from adult soluble extract of the parasite at 23–26, 34–55, 55 and 65kDa levels. Immunised lambs exhibited, after challenge, significantly higher lymphoproliferative responses (systemic and local) than all other animals groups (unvaccinated, adjuvant control animals, uninfected lambs). Challenge infection was accompanied by significant weight increases of abomasal lymph nodes; in addition specific peripheral and abomasal cell responses were correlated.

Antigen recognition patterns (Western blotting) and lymphoproliferative response (local and peripheral) have been determined in lambs immunised and partially protected against haemonchosis with p26/23, a purified somatic fraction of Haemonchus contortus. Immunoprotective response induced by p26/23 was accompanied by both specific lymphoproliferative response and serum anti-Haemonchus antibodies. Western blotting showed an extensive reactivity of sera from p26/23 vaccinated lambs with peptides from adult soluble extract of the parasite at 23–26, 34–55, 55 and 65kDa levels. Immunised lambs exhibited, after challenge, significantly higher lymphoproliferative responses (systemic and local) than all other animals groups (unvaccinated, adjuvant control animals, uninfected lambs). Challenge infection was accompanied by significant weight increases of abomasal lymph nodes; in addition specific peripheral and abomasal cell responses were correlated.

In an attempt to identify factor(s) that influence in vitro development of preantral follicles (PFs) in sheep, small (40–60μm in diameter) and large (61–100μm in diameter) PFs were cultured for 6 days in tissue culture medium (TCM 199) supplemented with transforming growth factor-α (TGF-α), insulin-like growth factor-II (IGF-II), epidermal growth factor (EGF) or follicle stimulating hormone (FSH). Increase in follicle diameter, oocyte diameter, induction of new DNA synthesis in the follicular cells and increase in number of follicular cells per follicle were measured as the indicators of development. Only EGF supplemented medium increased the follicle diameter, number of follicular cells and also induced intense DNA synthesis in both small and large PFs. TGF-α, IGF-II and FSH on the other hand were able to stimulate intense DNA synthesis only in large PFs. None of the supplemented media caused an increase in oocyte diameter. It is proposed that EGF stimulates the development of preantral follicles of sheep up to 100μm in diameter.

In an attempt to identify factor(s) that influence in vitro development of preantral follicles (PFs) in sheep, small (40–60μm in diameter) and large (61–100μm in diameter) PFs were cultured for 6 days in tissue culture medium (TCM 199) supplemented with transforming growth factor-α (TGF-α), insulin-like growth factor-II (IGF-II), epidermal growth factor (EGF) or follicle stimulating hormone (FSH). Increase in follicle diameter, oocyte diameter, induction of new DNA synthesis in the follicular cells and increase in number of follicular cells per follicle were measured as the indicators of development. Only EGF supplemented medium increased the follicle diameter, number of follicular cells and also induced intense DNA synthesis in both small and large PFs. TGF-α, IGF-II and FSH on the other hand were able to stimulate intense DNA synthesis only in large PFs. None of the supplemented media caused an increase in oocyte diameter. It is proposed that EGF stimulates the development of preantral follicles of sheep up to 100μm in diameter.

In this work, natural fibres (sisal, kenaf, hemp, jute and coir) reinforced polypropylene composites were processed by compression moulding using a film stacking method. The mechanical properties of the different natural fibre composites were tested and compared. A further comparison was made with the corresponding properties of glass mat reinforced polypropylene composites from the open literature. Kenaf, hemp and sisal composites showed comparable tensile strength and modulus results but in impact properties hemp appears to out-perform kenaf. The tensile modulus, impact strength and the ultimate tensile stress of kenaf reinforced polypropylene composites were found to increase with increasing fibre weight fraction. Coir fibre composites displayed the lowest mechanical properties, but their impact strength was higher than that of jute and kenaf composites. In most cases the specific properties of the natural fibre composites were found to compare favourably with those of glass.