Effects of dietary protein supplementation and plane of nutrition on the resistance and the resilience of Boer goats against artificial Haemonchus contortus infection under confined conditions

Abstract

The effects of protein and/ or energy supplementation have been well studied in sheep. However, the few pen studies conducted with goats have failed to identify the role of protein supplementation and combinations with energy supplements against H. contortus infection.The general objective of this thesis was to investigate the effects of protein supplementation and plane of nutrition on resistance and resilience of Boer goats to infection from Haemonchus contortus. To achieve this the first experiment was designed to determine the appropriate amount of additional dietary protein (by having three groups of mature goats effectively fed three different levels of dietary protein) required by nematode free animals given a single relatively high dose of infective H. contortus larvae, to not become infected or at least develop resistance and/or resilience. It was assumed, based on the scientific literature, that a single relatively high dose of infective larvae would elicit strong pathogenic effects where additional dietary protein would give some assistance to the does with their defense to Haemonchus. As often is the case with research on goats the results were not unequivocally clear.Based on these results it was clear that a single dose of infective larvae was insufficient to become established and that these animals had already developed some level of immune response and thus it was assumed, again based on the scientific literature, to elicit strong pathogenic effects the animals tested needed to be younger (more naïve to Haemonchus) and with greater i.e. continued exposure to infective larvae as would happen under grazing conditions (trickle infection) such that different quantities of dietary protein would give these animals different responses to infection by Haemonchus. Again the responses by the goats only indicated subtle differences in immune responses against trickle H. contortus L3 infection. These results, again unexpected, indicated that level of intake (or more specifically plane of nutrition, prior to or during exposure) may be at least as important as protein supplementation in reasonably well fed animals; and or that the method of infection (oral drenching with L3 larvae) was possibly an unreliable method of infection requiring a more consistent method of infection. As such the third experiment involved nematode free mature animals (the only animals available at that time) fed on very different planes of nutrition preceding and during the experiment given relatively high trickle doses of H. contortus larvae via intra-ruminal infection.Overlaid across these experiments were constraints imposed on the amount of infective L3 larvae used to achieve infection; 100 L3 larvae per kg live-weight as a single dose was the maximum initially approved by the University Animal Ethics committee, as they had concerns about animals dying, they also stipulated the use of oral drenching for infective larvae. It was only after these methods failed ii to elicit a strong response was approval given by the Univers...

Prevalence, effects and alternative control methods of Haemonchus contortus in small ruminants: A review

“…In addition, because the degree of infectivity varies significantly according to the H. contortus isolates, studies concluded on the importance to take in to account the parasite genetic diversity in various agro-ecological zones (Aumont et al, 2003) in all prevention and control measures. These above factors justify its high pathogenicity which is a requirement to the treatment and control of this parasite in small ruminants (Can, 2015) *Corresponding author e-mail: abiodouno@yahoo.fr. Tel: +229 97 085 468.…”