Dietary beta glucans to fight chronic enteritis

Since early 2006, laying hen farmers in the Netherlands have reported multiple table egg flocks that failed to reach peak production and had a poor laying persistency. Flocks showed a gradual but finally dramatic increase in daily feed intake. There was no obvious cause for this phenomenon; it was seen in all housing systems (although reported more in alternative housing systems, where hens have contact with litter and faeces on a regular basis), and found in all regions of the Netherlands. Post-mortem examinations of laying hens by the Dutch Animal Health Service (AHS) showed chronic inflammatory changes in the duodenum. Over time, the number of gut-related health problems increased within the laying hen sector, and chronic enteritis was determined to be one of the most challenging problems of the past decade. It was calculated that the loss of profit could easily add up to about €2 per hen, depending on the severity of inflammation.

 

The syndrome of chronic enteritis affects mainly brown layers and can be characterised as follows: 1) A reduction in feed intake early in the laying period followed by; 2) loss of feathers without feather renewal. Feathers are immediately eaten, resulting in complete absence of loose feathers on the floor; 3) low peak production and a poor laying persistency; 4) poor body condition of the hens; 5) a gradual but finally extremely increased feed intake up to 150 g per hen per day, and; 6) increased mortality.

 

Usually, no clear abnormalities were observed in litter and/or faeces. At necropsy, focal areas of necrosis associated with Clostridium perfringens were found in the majority of the flocks. Histopathology examination of the duodenum revealed villus blunting and fusion, marked crypt hyperplasia and an extensive lymphoplasmacytic infiltrate. Necrotic foci affected by Clostridium perfringens contained an abundant infiltrate of macrophages and heterophils.

 

The incidence of chronic enteritis was reported by a high number of farms; around 10% of the Dutch flocks had clinical symptoms related to chronic enteritis. The exact cause of developing chronic enteritis in laying hens is, however, still unknown. Based on a detailed screening study performed by the AHS, a variety of enteric infectious agents, like Clostridium perfringens, Brachyspira spp. and nematodes could be isolated from affected flocks. However, chronic enteritis of the duodenum could not be induced by these pathogens. Chronic enteritis appears to be a multifactorial disease. Certain stressors could also interfere with the health of the hens and increase the chance of development of chronic enteritis in the flock, such as transport of hens from rearing to laying farms, as well as the transition period around puberty.

 

Stress can induce an inflammation in the intestine (mainly the duodenum) thereby increasing the risk for secondary bacterial infections like Clostridium perfringens. Although this bacterium is not the cause of chronic enteritis, it plays an important role in the development of the disease. The constant alternation between recovery and infection increases the requirement of nutrients for immune response and recovery. The more nutrients that are allocated for those processes, the fewer nutrients will be available for growth, egg production and feather renewal. It is suggested that the hen is initially trying to compensate the higher need for nutrients by increasing the daily feed intake, but eventually cannot compensate for its increased nutrient requirements. This implies that the hen’s body condition suffers, body weight (breakdown of muscle tissue) and feathers are lost, and that egg production is lower. Finally, mortality in a flock will increase.

 

Because of the immense loss of profit of laying hen farming, together with the need for more practical advice for feeding and management factors, Schothorst Feed Research (Lelystad) and the Animal Health Service (Deventer) began a large research project to study the efficacy of different water, feed and management tools to reduce or eliminate problems associated with chronic enteritis. For the trial, five flocks with typical chronic enteritis symptoms were selected and 470 productive hens from each flock were placed in the facilities of AHS. All hens were housed on the litter from the farm of origin (except for one treatment that was housed on clean litter). The hens were randomly allotted over different feed and water treatments (21 in total). Treatments were continued for six weeks.

 

Every week, four hens per treatment were selected for necropsy to examine intestinal health and recovery. Production performance of the hens was measured as an indication of recovery. In total, five cycles (replicate flocks) were used to draw conclusions regarding the efficacy of all treatments, resulting in five replicates times 21 birds per treatment.

 

This research project was financed by a group of Dutch feed producers, the Product Board for Livestock Production, and various producers of feed/water additives, who are kindly acknowledged. The results of the following six treatments from the Product Board for Livestock Production and one treatment from feed additive supplier Orff a will be briefly discussed: 1) control corn-soy diet; 2) clean litter; 3) aspirin; 4) vitamins and minerals; 5) medium chain fatty acids (MCFA); 6) tylosin; and 7) β-1,3/1,6 glucans (MacroGard, Biorigin/Orffa).

 

The most important parameter for intestinal health and recovery was the ratio between the length of the villi and depth of the crypt. A high ratio indicates a long villus in which epithelium is sufficiently maturated and functionally active, in combination with a shallow crypt with a constant cell division (cell renewal). Birds suffering from chronic enteritis are in a constant mode of intestinal inflammation and intestinal recovery. Due to inflammation the length of the villus can vary and is often shortened. Usually, crypt depth is increased indicating an increased rate of cell renewal. A shorter villus in combination with an increased crypt depth will result in a lower villus/crypt ratio.

 

For the trial, the villus/crypt ratio at the start of the trial and after 2- and 6-week treatment was compared for each treatment. After two weeks all treatments showed an improved villus/crypt ratio compared to the villus/crypt ratio at the start of the trial. This highest increase was found in groups that received treatment with aspirin or were housed on clean litter. However, the control treatment and supplementation of extra vitamins and minerals resulted in a lower increase in villus/crypt ratio. After six weeks, all treatments showed comparable high villus/crypt ratios. These results indicated that there was a difference in response between treatments in time of intestinal recovery, but that recovery was shown for all treatments after six weeks treatment. Besides the villus/ crypt ratio, the number of inflammatory cells was indicative for recovery. The number of inflammatory cells in the villi and crypts indicated the severity of the inflammation, e.g. more inflammatory cells indicate a more severe inflammation. Treatment with aspirin, β-1,3/1,6 glucans, and housing on clean litter resulted in the lowest number of inflammatory cells during the 6-week treatment, whereas the control treatment and supplementation of vitamins and minerals resulted in the highest number of inflammatory cells. This data supports the data of the villus/crypt ratio.

 

Besides improvement of intestinal health, improvement of the production performance was also an indication for recovery. After arrival at the AHS, feed intake increased markedly in the fourth week and stabilised thereafter. The high feed intake probably indicated a recovery phase. This was shown by an increased body weight (1,830 to 1,850 g), while egg production (74% to 89%) and egg mass (47 to 57 g/d) also increased. However, as for intestinal recovery, some treatments showed a better improvement of performance than others. Egg production and egg mass were improved by supplementation of aspirin, vitamins and minerals, and β-1,3/1,6 glucans. Housing on clean litter and supplementation of MCFA resulted in the poorest production performance. In Figure 1 an overview of the effects of the different treatments is presented.

 

 

 

Purified β-1,3/1,6 glucans are known to modulate gut-immunity. The specific structure of this carbohydrate molecule can bind to specific receptors (dectin 1 receptor) on macrophages. Macrophages are white blood cells within tissue and play an important role in both the non-specific as the specific immune system. Research in pigs (Li et al., 2006) has demonstrated that the feeding of β-1,3/1,6 glucans reduced the plasma concentrations of the pro-inflammatory cytokines, IL-6 and TNFα, and raised the concentration of the anti-inflammatory cytokine, IL-10. This indicates that the intake of β-1,3/1,6 glucans reduces inflammation. The inflammatory changes observed in laying hens with chronic enteritis also contain infiltration of macrophages, next to abundant lymphocytes and plasma cells. The reduction in inflammation is assumed to be the most important mode of action behind the presented positive effects in laying hens suffering from chronic enteritis.

 

The product tested here is a highly purified product derived from baker’s yeast (Saccharomyces cerevisiae). It is important to consider that the effects of such a highly purified product can not be translated as such to impure yeast cell walls. To produce purified β-1,3/1,6 glucans one starts from yeast cells. First the cell content (yeast extract, used in human food application) is removed. What is left over is the crude yeast cell wall. This crude yeast cell wall roughly consists of two layers. The outside layer is mainly a protein layer (mannoproteins), whereas the inside layer contains the β-1,3/1,6 glucans (carbohydrates). In order to enable the β-1,3/1,6 glucans to bind to the receptors on macrophages, the protein layer should be removed. If the protein layer is removed in a proper way, the β-1,3/1,6 glucans are free and able to bind to the receptors on the macrophages. As long as the β-1,3/1,6 glucans are covered by the protein layer, they are not able to bind and no effect on the immune system can be expected. Most yeast cell wall products are crude cell walls with the protein layer still in place. In the production process of MacroGard (MG) the protein layer is efficiently removed and accordingly the protein content in the product is low (max 8%).

 

Chronic enteritis is considered as one of the most challenging problems in today’s table egg laying flocks in the Netherlands. Costs of chronic enteritis are very high for the farmer, due to impaired production, increased feed consumption, and the need for supportive treatments in affected flocks. Until now it was difficult to find an effective treatment of hens with chronic enteritis. The presented new trial results show that treatment is possible, but will take at least six weeks. For intestinal recovery best improvement was shown by supplementation of an antiinflammatory agent (aspirin), √-1,3/1,6 glucans (MG), and housing on clean litter, whereas for performance recovery best improvement was shown by supplementation of aspirin, β-1,3/1,6 glucans (MG), and vitamins and minerals. Aspirin may not be a practical application, due to withdrawal times for eggs. MG (purified β-1,3/1,6 glucans) is a natural feed ingredient that can modulate the inflammatory response and therefore provides, in combination with extra vitamins and minerals, a promising tool for the laying hen sector to fight chronic enteritis.