Prebiotic products failed to deliver in broiler study

A study evaluating the use of dry whey, chitosan, a mixture of both, and inulin in wheat based broiler diets found reduced bird growth due to lower feed intake.

The researchers, who work at NEIKER-Tecnalia, the Basque Institute for Agricultural Research and Development in Spain, and the University of Hohenheim in Germany, said they investigated the influence of those supplements on broiler performance, duodenal histomorphometry and caecal microbial composition.

Their findings indicated that adding dry whey powder (DWP), chitosan (CHIT), a mixture of DWP and CHIT, or inulin (INU) to wheat based broiler diets resulted in decreased weight at early growth stages.

They said they also observed lower weight and feed intake in the birds at later growth stages, except in the case of INU supplementation, where the researchers saw similar performance to birds fed with the control diet.

“Poor performance results obtained in the present study were unexpected, since an improvement in growth and intake has been reported in broilers fed with similar amounts of DWP (Kermanshahi and Rostami, 2006), CHIT (Khambualai et al., 2009), and INU (Velasco et al., 2010). Conflicting findings could be related to differences in the basal diet composition,”​ concluded the authors, who reported that corn-soybean based diets has been used in those earlier studies.

Study rationale ​

There is a growing interest in effective alternatives to antibiotic growth promoters. The authors stressed that it is critical to identify which ones are best suitable for poultry, in part due to conflicting evidences that their use improves broiler productivity and health (Geier et al., 2009b).

Such inconsistencies might be related to the main cereal used in diet formulation (Rodríguez et al., 2012), and, thus, said the researchers, it is vital to evaluate additive effectiveness in wheat and barley based diets, two of the most common energy sources in poultry nutrition (Amerah, 2015).

Positive productive results have been reported in poultry when using dry whey powder (DWP; Pineda-Quiroga et al., 2017) and inulin (Velasco et al., 2010) as prebiotics in corn based diets, although results about the response of chickens to supplemented diets based on cereal high in soluble non-starch polysaccharides (NSP) are scarce, said the team.

The researchers cited previous work showing that caeca fermentation of lactose from DWP, and fructo-oligosaccharides from inulin, promotd the growth of selective beneficial bacteria populations in detriment of potentially pathogens (Flickinger et al., 2003; Gulsen et al., 2002).

Similarly, natural antimicrobials such as chitosan, which has a wide spectrum of activity against Gram-positive and Gram-negative bacteria (Kong et al., 2010), have been used in corn based broilers diets with positive performance results (Khambualai et al., 2009), though it is possible that their inclusion increase gut digesta viscosity, noted the authors.

They said that for that reason they decided to evaluate the impact of such prebiotic material in wheat-barley broiler diets and observe how they influence bird performance through duodenal development and caeca microbial modulations.

Method​

The team said the DWP tested was a commercial sweet powder composed by a mixture of ovine and bovine whey composed by 703 g of lactose/kg of product. The CHIT was a commercial product prepared from chitin of shrimp shells. The INU used was also a commercial product obtained from chicory roots, containing 900 g of inulin/kg of product.

The study, which was conducted at the experimental facilities of Neiker-Tecnalia in Spain, involved 1,500 one-day-old Ross male broiler chickens, which were randomly allocated to floor pens at a stocking density of 30 kg/m2. Pens were equipped with one manual feeder, nipple drinkers, and wood shavings as litter material, reported the authors.

The scientists said the wheat and barley based diets used were formulated to meet broilers’ requirements during the starter and grower-finisher stages (FEDNA, 2008). Starter diets were offered from day one to 21 as crumbles, and grower-finisher diets were offered from day 22 to 42 as pellets. Each treatment comprised 10 pens, with 30 chickens each.

The trial diets included: control (no additive supplementation); 60-DWP (60 g/kg of inclusion of dry whey powder); 5-CHIT (5 g/kg of inclusion of chitosan); DWP-CHIT (60 g/kg of inclusion of dry whey powder and 5 g/kg of inclusion of chitosan); and 20-INU (20 g/kg of inclusion of inulin).

They said β-glucanases and β-xylanases were included in the same amount in all diets. 

They measured productive performance during the starter period (day 1-21) and for the entire feeding period (day 1-42), while duodenal measurements were registered at day 21. Caeca microbiota composition was determined using Illumina amplicon sequencing at days 21 and 42.

Findings ​

The researchers said that during the starter period, feeding chickens with any of the tested additives diminished their body weight (BW), average daily gain (ADG) and feed intake (FI) as compared to control diet. “This was also observed during the entire feeding period, except for INU supplementation, that showed similar values to control birds.” ​

The authors noted that none of the treatments affected duodenal histomorphometry.

“Our results also revealed that, as expected, the caeca microbiota composition was influenced by diet at every stage of the productive period, although an association between microbiota and performance was not clear.”​

At day 21, they said they did not observe any differences in microbiota composition of the control, 60-DWP, 5-CHIT and 20-INU birds although they noted that only the control diet promoted greater body weight (BW), average daily gain (ADG), and feed intake (FI).

The control and 60-DWP diets did not differ in their caeca communities at day 42, although only the control diet increased BW, ADG, and FI, said the researchers.

In both cases, caeca showed higher abundance of Lactobacillus gallinarum and Bacteroides vulgatus, and lower abundance of Escherichia coli/Shigella flexneri and Bacteroides fragilis, they said.

The study, said the researchers, also showed that an increase of Klebsiella pneumoniae (OTU 66) at day 21 of age, and of Streptococcus gallolyticus (OTU 39) at day 42, were particularly promoted by feeding with a mixture of DWP and CHIT, together with a reduction in performance.

“These bacteria can be part of the gut microbiota of clinically healthy broilers (Sekizaki et al., 2008), but they also represent a high sanitary risk because they are opportunistic pathogens in both animals and humans (Schulz et al., 2015; Wu et al., 2016).  OTU 66 is one of the respiratory pathogens causing high mortality in poultry farms (Aly et al., 2014), while OTU 39 causes septicemia in birds (Sekizaki et al., 2008). ​

“Unfavorable shifts in the intestinal microbiota are likely to result in relevant losses for poultry industry, either by a reduction in animal performance or by an increased risk of illness and death (Geier et al., 2009a). ​

“These findings suggest that the joint supplementation of DWP and CHIT at the tested doses did not act synergistically, as initially hypothesized. For a better understanding of the effects of the joint use of DWP and CHIT in wheat and barley based diets, further investigations evaluating them at lower doses are advisable to determine their feasibility in this type of diets.”​

Source:​ Animal Feed Science and Technology ​

Authors: ​C. Pineda-Quiroga, A. Camarinha-Silva, R. Atxaerandio, R. Ruiz, A. García-Rodríguez