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Management, nature and composition of feed
Nutrition is considered to be a clear factor that increases the risk of ulcers appearing. However, no researcher has been able to create ulcerogenic diets that reproduce the problem under any circumstance or type of management. Five factors to consider are: 1) alimentation system, 2) presentation of the feed, 3) size of the particles, 4) ingredients used, and 5) use of additives.
More problems are observed in restricted animals than in animals fed ad libitum and there is a higher risk of ulcers in fasted pigs (although there are studies showing the contrary in both cases). In fact, there are more cases of ulcers in pigs that are taken directly to the slaughterhouse than in pigs that are fasted during the night. Prolonged fasting reduces the digestive pH which affects the incidence of ulcers. From here it is reasonable to think that the principal cause of ulcers is a disordered feeding pattern with periods of fasting followed randomly by periods of feeding ad libitum. These situations can occur when the supply of feed is poorly controlled, when access to the feeder is difficult or when the animals suffer some type of illness.
Other factors that should be considered are the presentation of the feed in granules, grinding the feed too finely, and an unsuitable level of fiber and protein. The presentation of the feed in granules and fine-grinding (< 600um in maize-soya feeds) increases the consumption of water and the fluidity of the stomach content. This causes the stomach’s pH to rise which leads to a higher incidence of ulcers. However, no relation has been found between the incidence of ulcers with either dry or humid nutrition. An excess of protein results in a greater presence of ammonia which can affect the digestive physiology of the animal. However, a lack of protein is more damaging than an excess in this matter. Within the composition of the feed it is believed that oats and barley are less problematic cereals than wheat or maize although the data on this matter are quite contradictory. The problem increases with the use of thermally processed or expanded cereals. Probably, the two key factors in relation to the type of cereal are the percentage of very fine particles (< 200 um; not the average size of the particle) of the feed as a consequence of grinding and the level of fiber. So, fine grindings increase the fluidity of the digestive content which has been related to a high incidence of ulcers.
Fine grindings also increase the velocity of the emptying of the stomach which leads to a lower pH. On the other hand, high fiber contents have contrary effects. Besides, a moderate contribution of fiber improves the tonicity of the walls of the digestive apparatus. In fact, the incidence of ulcers seems to be lower in pigs on straw beds than in pigs on slats. It is reasonable to recommend the use of fibrous raw materials and feed in thickly ground flour in the event of an incidence of ulcers. It should be kept in mind that feed with these characteristics tend to reduce the energy consumption and worsen the conversion rates which is why they should only be used in very problematic cases. Finally on many occasions the problem tends to appear due to the addition of additives. However, the efficiency of these additives is very relative.
Certain studies have shown an increase in the processes of organic oxidation in animals with ulcerogenic processes. It is known that the lack of vitamin E provokes ulcers and mortality but an excess of this vitamin (> 20-30 mg/kg feed) does not reduce the incidence of the problem on the majority of affected farms. Given that the lack of this vitamin is usually accompanied by liver problems, an additional supply of this vitamin, together with Se (> 0.3 mg/kg) could be of interest when both problems, ulcers and hepatosis, are evident. Whatever the case the use of rancid or poor quality fats must be avoided and the use of adequate levels of antioxidants in the feed must be assured. Finally, diverse studies recommend the use of basifiers such as bicarbonate (1% of the feed) or to raise the level of Zn and of certain group B vitamins such as folic acid to reduce the problem of ulcers, but these practices have only shown beneficial results on a few occasions. In a similar way the reduction of Fe, Cu and Ca levels has been recommended in these cases but the scientific base of these recommendations is weak. The use of drugs that reduce hydrochloric acid secretions (e.g. omeprazole and by-products) may be an important means for reducing the incidence of ulcers. However, these products are expensive and their use in swine has not yet been evaluated.
Ulcers and pathologies
Many researchers have speculated about the infectious origin of the problem of ulcers, similar to that which occurs in humans (H. pylori). However, the tests that have been made with the aim of producing ulcers in the esophageal region of the stomach with this microorganism have not been successful so far. Diverse studies have shown that a certain correlation exists between the presence of diverse diseases and the appearance of ulcers. The reason for this correlation could be that sick animals tend to show disordered feeding behavior, with many animals showing periods of anorexia with the stomach remaining empty for hours. It has been observed that the seasonal nature of the incidence of ulcers (more problems between November and March according to data from Murcia) coincides with the months with greater incidence of pneumonic processes. Also, illness results in a greater secretion of histamine which leads to a higher incidence of ulcers in the esophageal region. Finally, the incidence of ulcers has been related to intensive medication. The problem is probably more related with the illness per se than with the medication, although certain treatments (e.g. aspirin) can affect the digestive mucosa and influence the development of ulcers.
Conclusions
The existing information confirms what has been observed in practice; it is not easy to resolve the problem of ulcers through nutritional modifications or by using antibiotics or additives in the feed. Probably the best guidelines consist of improving the management of the nutrition programs together with a good control of respiratory and digestive type diseases. In the case of high incidences of ulcers it is recommended to increase, in a reasonable manner, the size of the particles and the levels of vitamin E, selenium and fiber in the feed, and to reduce levels of energy and protein. This feed should be supplied for 7 to 10 days.
