Development of immunity in boer goats naturally infected with the nematode haemonchus contortus

Haemonchus contortus (H. contortus) is a major gastrointestinal nematode that adversely affects goat production in tropical and subtropical countries leading to high economic losses due to lower growth rates, markedly reduced reproductive performance and mortality. Farmers can use different strategies including anthelmintic treatments, grazing management, vaccination, improved nutrition and selection of resistant animals in order to control or prevent their animals from infection by this nematode. This study was conducted to determine and describe the development of immunity in Boer goats kids based on their faecal egg count (FEC) and selected blood parameters in relation to specific antibody production against this nematode. Understanding the development of immunity could enhance control programs in animals, particularly in goats. Three experiments were conducted at two different locations. Fresh faecal and blood samples were collected, at monthly intervals, from a total of 346 multiple-age Boer goats at Yarrabee Boer Goat Stud and The University of Queensland Gatton farm. Worm burdens were determined from FEC’s and larval culture, blood was analysed for packed cell volume (PCV), haemoglobin, eosinophil, mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), and specific antibodies (IgG, IgA and IgM) were obtained from analyses of sera using Enzyme-link Immunosorbent Assays (ELISA). Colostrum and milk samples were collected as four series at monthly intervals from post-partum does that were either given or not given protein supplements, for four weeks prior to parturition, and immunoglobulin titres were analysed using ELISA.The results of this study showed that Boer goats developed immunity against H. contortus infection under naturally at about 14 months of age. Female Boer goats were apparently more resistant and resilient to H. contortus infection compared to male Boer goats based on immune parameters - H. contortus-specific immunoglobulin (IgG, IgA, IgM), FEC and PCV values. However, there was a lack of evidence that the development of immunity was influenced by the intensity of L3 infection as indicated by FEC values due to the inclusion of occasionally drenched animals in this study. The pre-partum supplementation of goats in this study did not have any effect on resilience of kids naturally infected with H. contortus as there were no significant differences on birth and live weight throughout the study period. Goat kids were susceptible to gastrointestinal parasite infection as soon as they begin feeding on pastures, based on faecal analysis results which were positive when they were 2 months of age. The study also showed a lack of evidence of a relationship between the immunoglobulin content of milk from dams and the immunoglobulins content in suckling kids’ serum. Furthermore, protein supplementation to does during their last 4 weeks of their pregnancy had no significant influence on their kids’ serum immunoglobulins from 1 to 3 months after birth.