Investigations on the effects of dietary insoluble and soluble non-starch polysaccharides (NSP) on host-parasite interactions in laying hen chicks infected with Heterakis gallinarum or Ascaridia galli

The objective of this study was to test the hypothesis that low or highly soluble dietary non starch polysaccharides (NSP) differently affect infections with Heterakis gallinarum or Ascaridia galli in grower layers. Because H. gallinarum acts as a vector for transmission of Histomonas meleagridis, the agent of Blackhead disease , effects of NSP-supplemented diets on interactions between these two parasites were also investigated. The experiments were conducted between 2007 and 2010 at the Department of Animal Sciences of the Gottingen University. Three experimental diets were used: basal diet (CON), supplying metabolizable energy and nutrients for grower layers according to recommended feeding standards. One hundred gram of pea bran or chicory root meal were added to each kg of CON in diets I-NSP and S-NSP supplying insoluble (I-) or soluble (S-) NSP, respectively. The first study aimed at investigating effects of NSP supplemented diets on interactions between H. gallinarum and H. meleagridis, including a prophylactic treatment with dimetridazole (0.05%, w/v) via drinking water against H. meleagridis for half of the birds. Histomonas free H. gallinarum female worms obtained from this study were used for the preparation of infection material applied in the experiment that investigated effects of NSP-supplemented diets on H. gallinarum infection. Effects of dietary NSP on either H. gallinarum- or A. gall-infections were separately investigated in two consecutive experiments, each comprising three identical runs for each nematode species. In each run, three feeding groups of one-day-old female layer chicks were built, each being fed until an age of wk 3 with one of the three experimental diets. At the end of wk 3, the birds were marked with wing tags and weighed. Each feeding group was subdivided into an uninfected control and an infected group of birds, the latter being inoculated with 200 embryonated eggs of H. gallinarum or 250 embryonated eggs of A. galli, respectively. Daily feed consumption was determined per group throughout the experiment until wk 11. In the last two runs of the H. gallinarum-experiment, the infected birds were placed into individual cages and their daily total amounts of faeces, number of eggs per gram of faeces (EPG) and total number of eggs excreted within 24 h (eggs per day, EPD) were determined. In the A. galli-experiment, the faeces were collected at the time of slaughter and EPG was determined. The birds were slaughtered 8 wk post infection (p.i.) and their worm burdens were determined. Volatile fatty acids (VFA) and pH were measured in caeca contents. In the first experiment that dealt with histomonas contaminated H. gallinarum (Chapter-II), treatment against H. meleagridis significantly increased the incidence of H. gallinarum infection and the average worm length in all infected groups irrespective of the type of experimental diet consumed by the birds. An interaction between effects of diet and dimetridazole treatment indicated that S-NSP resulted in lowest worm burden in dimetridazole-untreated birds, whereas it caused highest worm burden in treated birds. Within each feeding group, higher worm burdens were determined in treated than in untreated birds. Infection with H. gallinarum reduced the body weight (BW) of the chicks, and H. meleagridis aggravated this effect. Dimetridazole-treated and untreated uninfected birds developed similar BW. Both NSP-supplemented diets, with S-NSP being inferior to I-NSP, led to lower BW of the birds. In the histomonas free H. gallinarum-experiment (Chapter-III), the NSP-supplemented diets elevated the incidence of infection, the average number of larvae and the total worm burden compared to CON. The worm length was not influenced by the type of diet. The daily amount of faeces increased in NSP-fed birds. The EPG, EPD and female worm fecundity (EPD/female worm) were elevated after feeding S-NSP, whereas I-NSP led to lower EPG/female worm. The EPD increased in the sequence of CON < I-NSP < S-NSP. Both, the NSP-supplemented diets and infection led to reduced BW of birds and infection additionally impaired the feed conversion rate. The NSP-supplemented diets increased average length of caecum with S-NSP exerting a stronger effect than I-NSP. Filled caeca weight was increased by S-NSP. The infection increased the weight of filled and emptied (washed) caeca. Feeding S-NSP lowered intracaecal pH and molar proportion of acetate and increased that of butyrate compared to CON and I-NSP. Caecal pool of VFA was increased with S-NSP. Infection increased intracaecal pH, accompanied by lower molar proportion of butyrate and reduced caecal pools of VFA. In the A. galli-experiment (Chapter-IV) both NSP-diets, particularly S-NSP, increased incidence of infection and worm burden of the birds, but the development (length) and fecundity of the nematode remained unaffected. A. galli-infection caused a less efficient feed utilization for body weight gain (BWG) resulting in lower BW irrespective of type of diet consumed. NSP-fed birds, particularly those on S-NSP, showed retarded BW development compared to birds receiving CON. Intracaecal pH was lowered by feeding S-NSP but was unaffected by A. galli-infection. Both NSP-diets increased caecal VFA pool size, S-NSP exerting a greater effect than I-NSP. Infected birds had smaller caecal VFA pool size than their uninfected counterparts consuming the corresponding diets. S-NSP also led to higher weights of splanchnic tissues and intestinal tract. These effects were less pronounced in I-NSP fed chicken. The results show that H. meleagridis does not only harm the definitive host, but also its vector, H. gallinarum. Both, insoluble and soluble dietary NSP favor H. gallinarum infection while S-NSP additionally intensifies histomonas-infection, which then impairs establishment and development of H. gallinarum. The pea bran and chicory root meal used as sources of insoluble and soluble dietary NSP, respectively, favored the establishment of histomonas-free H. gallinarum in grower layers. Inulin rich chicory root meal additionally enhanced fecundity of this nematode. Insoluble and soluble dietary NSP retard growth performance, alter gastrointestinal environment and lead to higher weights of splanchnic tissues associated with an elevated establishment of A. galli in grower layers. The NSP supplemented diets, and S-NSP in particular, may have altered the gastrointestinal environment, which in turn enhanced nematode infections. It is concluded that the two natural sources of insoluble and soluble NSP offer no potential as protecting agents against the parasitic infections in chicken. Therefore, suitable measures of precaution should be applied to production systems particularly prone to gastrointestinal parasitic infections and where diets with relatively high NSP-contents are fed.