Técnicas e instrumentos de recolección de datos

RESILIENCE OF GOATS AGAINST GIN INFECTION 2.7.1 Under field conditions

There is much less information about the effect of protein supplementation on PPR in goats compared with sheep. The studies conducted by Etter et al., (1999) in Alpine dairy goats from - 5 weeks to + 4 weeks around parturition confirmed that the PPR could be eliminated by increasing protein supplementation (commercial concentrates) by 28% and 44% above their normal protein requirements (INRA standards, 1988). Under tropical conditions, the same finding was also attained in 2 - 3 year old West African Dwarf does (Faye et al., 2003) with higher planes of nutrition during pregnancy and lactation (200 g of cotton seed and 200 g of rice bran, achieved by supplementing their diets) rather than protein supplementation alone. Abdullah (2015) has recently reported that Boer does, naturally challenged with GIN infection and supplemented with protein (lucerne pellets) at 1% of their live-weight during their last four weeks of pregnancy, produced more IgG and IgA antibodies in their serum. It seems that the elimination of the PPR by the manipulation of nutrition supplementation in goats is similar to sheep.

In non-reproducing goats, fewer studies have been conducted. The studies by Torres-Acosta et al., (2004; 2006) on growing Criollo kids in Mexico confirmed that higher planes of nutrition (using sorghum and soybean, AFRC standards, 1993) could improve resilience and, to a lesser extent, resistance against GINs in wet and dry seasons. The studies of Martı´nez Ortiz de Montellano et al., (2007) showed a clear effect of the plane of nutrition (100 g of sorghum and soybean with ratio of 74:26) on the resistance in growing Criollo kids in that FEC of supplemented animals before slaughter was significantly lower than those of non-supplemented cohorts. In addition, supplementation reduced the female worm length of T. colubriformis and the prolificacy of both H. contortus and T. colubriformis (Martı´nez Ortiz de Montellano et al., 2007).

2.7.2 Under confined conditions

There is a major lack of information concerning the effect of dietary protein supplementation on the resistance and resilience of reproducing goats against experimental GIN infection, especially with H. contortus. Most information is from studies in non-reproducing goats on differing planes of nutrition or given protein supplementation, but results are inconsistent.

With regards to plane of nutrition, the first indoor trials were performed by Blackburn et al., (1991; 1992) that investigated the interactions between planes of nutrition (roughage, and 100 g mixture of corn (80%) and soybean (20%)) and H. contortus. These authors reported a significant difference in the live-weight of goats fed different nutrition levels, and goats given a low plane of nutrition tended

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to carry more worms and have higher establishment rates than that of their counterparts. However, their study did not determine whether the response was attributable to protein or the combination between energy and protein supplementation. Additionally, they failed to find an effect of a higher plane of nutrition on FEC. This finding is not in agreement with the report of Phengvichith and Ledin (2007), who used Gamba grass (Andropogon gayanus) and Gliricidia foliage (Gliricidia sepium) supplemented with dried cassava root chip and a commercial piglet starter concentrate, in that their high plane of nutrition diet reduced FEC in goats when compared with goats fed the low plane of nutrition.

There are studies that were conducted to identify the effect of dietary protein supplements on the resistance and resilience of goats against GIN infection. Unfortunately, these studies also failed to achieve their objectives. For example, Torres-Acosta (1999) conducted an indoor trial with kids, artificially infected with H. contortus, given iso-energy diets under a restricted feeding regime to identify the role of metabolisable protein (soybean meal, NRC, 1989) and reported a reduction in the FEC of the kids, in both high and low metabolisable protein groups, from the beginning to the end of the trial. However, FEC and worm burdens of the goats given the high metabolisable protein diet were higher than that of their counterparts. It is likely that kids could not utilize the extra metabolisable protein from the diet when their energy intake was low. Etter et al., (2000) examined the effect of different levels of dietary protein (in a diet based on corn, wheat straw, hay, and fibrous pellets) on resistance and resilience of Alpine dairy goats given a trickle infection with T. colubriformis and reported that resistance (shown by reduced FEC and eosinophil) of goats was enhanced by a protein supplement. However, no information about the effect of the protein supplement on the worm population was given. Therefore, the conclusions from that study remain somewhat limited. Nnadi et al., (2007; 2009) investigated the effects of protein supplementation of a diet based on grass, Palm kernel cake, and Bambara nut chaff on the resistance and resilience of West African Dwarf goats against H. contortus infection. They found that protein supplementation could delay parasite establishment, significantly enhance the level of albumin but not improve PCV and total serum protein level.

It is clear that indoor trials failed to separate the effects of metabolisable protein or the combination of protein and energy on resistance of goats to GIN infections. An additional complication comes from the ability of goats to select their preferred diet ingredients from their feed-trough, thus biasing the expected outcome of the diets (Hoste et al., 2008). Selection can only be overcome by feeding a pelleted diet.

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CHAPTER 3: EXPERIMENT 1 - THE EFFECTS OF PROTEIN SUPPLEMENTATION ON THE RESISTANCE AND RESILIENCE OF YOUNG DRY BOER DOES AGAINST H. CONTORTUS AFTER A SINGLE LARGE CHALLENGE WITH L3 LARVAE UNDER CONFINED CONDITIONS