Hotly Debated: Is Pronutrin an Effective Substance for Gastric Ulcers?

This article was translated using AI.

Feeding hay in portions along with concentrate and Pronutrin ensures higher gastric pH values than ad libitum hay feeding! Therefore, horses with gastric ulcers should by no means receive hay ad libitum for therapy, but rather hay in rations with concentrate (and Pronutrin).

At least that is the summary statement of a doctoral thesis from 2007 that is repeatedly cited (Damke C, 24-hour intragastric pH-metry in horses during the feeding of various rations, University of Leipzig, 2007). But what is behind this statement? To find out, one has to read the entire study and not just the summary.

Studies in/with horses – feasible but complex

Scientific studies in horses are still scarce, making them all the more important for finding better treatment options for various diseases. However, many of these studies are not suitable for direct application to horses in riding stables or integration into everyday life, because scientific studies always look at only individual partial aspects of the organism, never the whole horse (as no one could record such volumes of data). In addition, relatively small groups are always examined, as keeping large animals for testing is very expensive and elaborate even for universities. Therefore, the significance of a single study must always be critically questioned for statistical reasons alone. Accordingly, a single study is often not sufficient; one must look at several that consider different partial aspects of the topic and determine a cross-section from them. Furthermore, the design of each study must be examined closely, as methodological errors can lead to significant distortions of the results.

These are exactly the problems with the aforementioned doctoral thesis, which deals with the pH value in the stomach after various feeding schemes or feeds. Here, only six animals were used and, after 14 days of habituation to the feed in each case, the pH value in the stomach was determined for 24 hours using a probe.

The basic statement here is: in order to heal a change (inflammation, ulcer) in the stomach, the gastric pH value should be kept above 4, and this is achieved by portioning hay with concentrate, but not with hay ad libitum.

But how was the study conducted?

Feeding before measuring the pH value

The 6 horses underwent 3 feeding schemes in succession for 14 days each before measurements were taken:

1. 24/7 14 days hay ad libitum (the horses ate an average of 2.4kg / 100kg body weight)
2. Rationed hay (1.5kg / 100kg body weight) in three meals with 4 meals of concentrate (energy pellets and crushed oats)
3. Rationed hay (1.5kg / 100kg body weight) in three meals in combination with 4 meals of concentrate (energy pellets and crushed oats) plus Pronutrin, a pectin-lecithin complex designed to significantly improve the elevation of the gastric pH value compared to pure hay feeding.

After each of these 14-day feeding periods, a 24-hour measurement of the gastric pH value was carried out using a probe that was placed gastroscopically in the stomach under sedation and attached to the halter with a long cord reaching from the probe to the nostril.

With six horses and three different feeding schemes, this results in 18 different measurements in total. In 10 of these 18 measurements alone, the gastric probe slipped into the esophagus. Once the probe slipped as far as the small intestine. Both resulted in pH values above 6. However, it is not clear from the data how many values were unusable and how many finally flowed into the statistical evaluation. This reduces the number of (already manageably few) measured values considerably, so that such an investigation is rather questionable from the viewpoint of the statistical reliability of the data.

In humans, the gastric pH value depends on age and sex

The doctoral thesis refers to the fact that in humans there are differences in the gastric pH value between male and female persons; in humans and dogs, age-dependent differences are also evident. None of this has been investigated in horses yet. Nevertheless, a completely inconsistent group was examined here with both male and female animals, various age groups, and also two animals that showed changes in the stomach ("gastric ulcers"). However, the results were always only shown as a median of all animals; a distinction between the individual individuals was never made or corresponding groups formed, which was of course not possible here due to the small group size.

Two horses experienced a longer feeding pause under pure hay feeding

Two horses showed a pH value between 1 and 2 over a longer period under pure hay feeding, i.e., no feed was consumed at this time. What these pauses were related to was not analyzed. In the other groups, this did not happen because these horses received concentrate. It is possible that eating the much softer concentrate was more pleasant with a probe cord hanging in the gullet than eating hay. However, for the calculation of the median value (average) in feeding, these atypical values were included, which is statistically inadmissible.

There was no additional incentive to eat in the hay-ad-libitum group

Which brings us to the next question: why, in a trial comparing two high-fiber feeds, is one group combined with concentrate, even though the paper explicitly points out that the increase in pH by the concentrate is by no means intended to heal lesions in the stomach? Wouldn't the simultaneous feeding of haycobs instead of pellets and oats, with and without an additive, have made more sense? Because everyone who deals with horses knows that cereal-containing feed in the trough is eaten much more readily than hay. In addition, a change in eating behavior caused by the gastric probe could have been analyzed in the hay-ad-libitum horses, because everything offered in the trough is more attractive than hay. The horses in the concentrate and Pronutrin group were therefore probably more encouraged to eat than the horses in the hay-ad-libitum group, who lacked an additional incentive. If one really wanted comparable data, then a sensible distribution of the feeding schemes would be:

1. Hay ad libitum
2. Hay ad libitum with soaked hay cobs
3. Hay ad libitum with soaked hay cobs and Pronutrin

Then the data would actually be comparable and one could make visible whether Pronutrin has a positive effect or whether this was only achieved by the addition of cereal-containing concentrate.

Influence of the gastric probe on feed intake

The influence of the examination method on the feeding behavior of the horses was not investigated. To avoid the possibility that the gastric probe might influence the measurement results, the experiment could have been divided so that two horses always received a different feed over the 14 days, because in the hay-ad-libitum group the horses were equipped with the gastric probe for the first time and it cannot be ruled out that this influenced feed intake, while in the next two experiments they were already used to it. If two horses had always been in a different group in parallel, there would have been two horses in each group wearing this gastric probe for the first time.

The study states: "The horses tolerated the tube exiting the nostril and the recording device in the mane protector very well and showed undisturbed feeding and general behavior," which is intended to be proven by the following images:

To what extent the probe actually did not restrict the horses must be judged by their facial expression; investigations into the stress level caused by the probe (e.g. by measuring salivary cortisol) were not carried out.

It cannot be seen from the data in the study whether the horses consumed more feed in the 14 days before the test day than on the test day itself, which would have documented the influence of the stomach probe. The values were determined but not shown in the paper.

However, all horses showed small cuts on the nostril during 6 out of 18 trials due to the tension of the stomach probe, and in a few cases also gagging, coughing, snorting, flehmen, inappetence, and mild colic. It is therefore quite obvious that the horses did not feel comfortable with the stomach probe and that this can influence their feeding behavior. An evaluation of the feeding behavior in the 14 days before the measurement compared to the measurement day could have clearly shown this and would probably have made the data of the hay-ad-libitum group look different.

Median values do not show the whole picture

In the interpretation of the data, it is pointed out that the average pH value in hay-ad-libitum feeding was lower than the average in meal-feeding of hay with concentrate or hay with concentrate and feed additive. That sounds as if the pH value in hay feeding were consistently more acidic than in the other feeding schemes. However, if one looks at the original data, a somewhat different picture emerges.

Hay ad libitum shows the following picture as an average value over all measurements over the 24-hour measurement period:

The pH value drops significantly after the probe is inserted, which is an indication that the horses did not immediately start eating hay with enthusiasm, but instead did not consume any feed for about 3 hours. Then it rises as hay is consumed and is in the normal range around pH 3 most of the time.

When measuring the other groups, the following picture emerges:

Blue is the profile with only concentrate, dark red the profile with concentrate and Pronutrin. Here it becomes clear that the pH value fluctuates extremely compared to hay feeding. On average – i.e., the average over all measuring points in 24h – it is indeed slightly higher than that with hay-ad-libitum feeding. In the real measurements, however, the pH value repeatedly drops significantly into the acidic range, only to shoot up again. This means that the pH value is by no means in a less acidic range over the entire time, as the median value suggests, but that pH values well below 3 occur repeatedly. Furthermore, this representation also shows that the difference between concentrate only and concentrate plus Pronutrin is marginal, so that one cannot actually expect any real stomach-protecting effect from this feed.

This takes the frequently spread statement that concentrate and hay in meals lead to a higher pH value in the stomach and that this feeding is therefore gentler on the stomach than hay ad libitum ad absurdum.

He who pays the piper calls the tune...

All in all, one can see that with a clever choice of experimental approach, the measured values can be moved in the desired direction. This is also called "reverse research" – the desired result is achieved through the choice of the experimental setup as well as the clever selection of desired or omission of undesired data.

Another study (Koeller et al., Pferdeheilkunde 2010) has since shown that Pronutrin only leads to an average increase in the gastric pH value to 2.7 for 15 minutes! The study by Sanz et al. (The Veterinary Record, 2014) even comes to the conclusion that feeding a pectin-lecithin complex neither leads to an improvement nor serves to protect against gastric ulcers.

Conclusion: The simplest and most effective method for preventing gastric ulcers remains 24h access to hay with grazing

The best therapy remains low-stress husbandry with 24h access to hay and (limited) grazing. Several authors have been able to show that gastric ulcers only occur extremely rarely under hay-ad-libitum feeding and only in combination with pure box stalling (stress). If the horses also had access to pasture, no gastric ulcers could be detected or caused. Alfalfa also has an excellent buffering effect due to its high protein and calcium content. Perhaps someone will investigate in the near future whether the combination of hay-ad-libitum feeding with alfalfa allows existing gastric ulcers to heal even better and faster. But hopefully with a sensible experimental setup whose results can be defended.

More on the topic: Factsheet: Gastric Ulcers in Horses or in our Podcast Episode #18 Burping in Horses – A Sound Nobody Should Ignore

Sources

Damke, Cornelia. 24-hour intragastric pH-metry in horses during the feeding of various rations. Diss. Leipzig, Univ., Diss., 2007.