Main page > News archive > Progut^® Info Letter 2/2009

14.11.2009

The effect of Progut^®on the recovery from chronic enteritis in laying hens. Schothorst Feed Research 2008.

Modified from the original report by Juhani Vuorenmaa

1.       Background

The chronic enteritis syndrome in laying hens is characterized as extremely high feed intake, loss of feathers, low peak production, moderate laying rate, poor body condition and high mortality. Although the problem is reported by a high number of farms, the exact cause for it is still unknown. It is suggested that certain stressors, like transport of hens from rearing to laying farms, increase the risk for chronic enteritis. Stressors can induce inflammation in the intestines thus increasing the risk for secondary bacterial infections like Clostridium perfringens. Chronic enteritis is usually reported in alternative housing systems where hens do have regular contact with litter and faeces. The recovery from the infection increases the need for specific nutrients for the immune response and recovery and fewer nutrients are available for growth and egg production. It is suggested that the hen is initially trying to compensate the higher nutrient need by increasing the daily feed intake but eventually failing. As a consequence the hen is losing its body condition, weight, feathers, reducing egg production and finally dies. It has been calculated that the loss of profit could add up to € 2 per hen depending on the severity of the infection.

2.      Objective

The purpose of the trial was to study the effect of Progut^®on the recovery from chronic enteritis in laying hens.

3.      Materials and methods

The trial was conducted by Schothorst Feed Research in the Netherlands in 2008. Alternatively housed brown layers suffering from chronic enteritis were selected from five commercial farms and transported to the trial farm. A total of 315 laying hens were allotted to three different treatments as a part of a bigger trial (Table 1). Each treatment consisted of a floor pen with 21 laying hens. Hens were housed on litter originating from the laying hen farm with exception of treatment 3. These hens were housed on a clean litter. All treatments were replicated in time with five different flocks and each replicate lasted six weeks.

Table 1. Description of the treatments

After arrival to the trial farm, the birds were weighed to set a start weight per treatment. The hens were also weighted at day 7, 14, 21 and 28 (10 individual, randomly chosen hens). At day 35, the remaining hens were weighed. Feed and water were available ad libitum. Weekly feed intake, laying rate, egg weight and egg mass were measured per treatment. Feed conversion ratio was calculated per week and treatment. 

At arrival, 21 animals were sent for post-mortem examinations in order to determine a zero value of each flock at the start of the experiment. All animals were investigated on general health indicators, like possible disease and infections. After this macroscopic observation, five productive and flock representative animals were selected for microscopic observations. The same activities were repeated at day 14, 21, 28 and 35 using four animals per treatment to indicate differences in time. A macroscopic post-mortem examination was also performed for animals that died during the experiment or were euthanized because of health problems. At the last day of the experimental period the remaining hens per treatment (max. 5) were sacrificed and examined.

Duodenum samples were collected at different time points and the three most representative samples were selected for histological evaluation. The following parameters were measured from the duodenum samples in HE coloured freeze coupes.  

Villus height and crypt depth

Villus length[S1]  and crypt depth of five representative villus and crypt per bird were measured. Birds suffering from chronic enteritis are in constant mode of intestinal inflammation and recovery. Due to the acute inflammation, the villus length can vary and is often shortened. The number of active cells for cell division in the crypt will increase. This will result in increased crypt depth and higher cell renewal which can be expressed by the number of mitoses per crypt.

Number of mitoses per crypt

The number of cells in division per crypt for six representative crypts per bird was counted. Active cell division indicates higher turn-over of the crypt cells. Determination of the active cell division at weeks 2 and 6 of the trial indicates the effects of the treatments on the recovery from chronic enteritis.    

Infiltrate inflammation cells

The presence of inflammatory cells was scored in the lamina propria mucosa of the intestine of each duodenum sample. The number of inflammatory cells indicates the severity of the inflammation.

The data was evaluated statistically by analysis of variance using Genstat statistical software. Treatments were compared based on the least significant differences. Effects with P < 0.05 were considered to be statistically significant.

4.      Results  

One flock was a clear outlier and was therefore deleted from the dataset prior to the final statistical analysis.

The results from the first flock illustrated well the recovery process of laying hens from chronic enteritis. In this flock the feed intake of the hens increased from 136 to 168 g/d by the fifth week in the trial and stabilised thereafter (table 1). The laying rate and egg mass showed a similar trend. It was therefore concluded that the high nutrient intake indicates recovery phase from chronic enteritis. This was shown by increased body weight and egg production. The hens first need a higher nutrient intake to recover. Subsequently, the feed intake and egg production will normalise.

Table 1. The performance of the first flock during the trial period

Progut treatment showed the highest feed intake and production performance as an average over the 6 week trial period (table 2). The differences were numerically or significantly higher than the control treatment 1 (own litter) and 3 (clean litter). Hen weight was also highest in the Progut treatment. Feed intake was on average 123 g/d at the start of the experiment. It increased rapidly to over 150 g/d and was maintained at this level until the end of the trial. Laying rate, egg mass and body weight followed a similar trend. The average of all trial groups for laying rate, egg mass and body weight at week 1 and 6 are presented in table 2.   

Table 2. The performance parameters during the trial

The results from the histological measurements showed increased villus / crypt ratio from 2 to 6 weeks of the trial, which was mainly due to reduced crypt depth (table 3). The villus length was not affected. In addition, the number of mitoses per crypt was decreased but the severity of the infiltrate cells was not changed in time. The results indicate improvement of intestinal health during the trial.   

The crypt depth in the Progut treatment was intermediate to the control treatments suggesting low cell turnover (table 3). This was supported by the lowest number of mitoses in the crypt cells, although the differences weren’t statistically significant. Severity of the inflammation cells in the Progut treatment was numerically lower than the control 1 (basal feed) but higher than the control 3 (clean litter). All these parameters are indicating recovery of the small intestine in the Progut treatment. However, the villus length was lowest in the Progut treatment which was contradictory to the other histological parameters. It may be that the lower cell renewal activities in the crypt have resulted in shorter villi.

Table 3. Histological parameters in different treatments

5.      Conclusions

-          High nutrient intake and as a consequence increased body weight and egg production were indicators of a recovery phase from chronic enteritis

-          Progut treatment showed the highest feed intake, body weight and production performance over the trial period

-          The differences were numerically or significantly higher than the control treatments

-          The supporting data from the histological analysis indicated lower cell turnover and inflammation based on crypt depth, number of mitoses per crypt and severity of the inflammation cells

-          However, the villus length was lowest in the Progut treatment which is a contradictory finding to other histological parameters measured. The reason for the lower villus length remained unclear

-          Progut addition alleviated chronic enteritis based on improved performance parameters. The effects on production performance were partially supported by the effects on histological parameters