Link between Hemorrhagic Bowel Syndrome (HBS) and liquid feed

Sudden death due to HBS is a devastating, stealthy phenomenon that affects pigs in growth and finishing phases. The heaviest animals die, sometimes a few over several days, or a few per week, but in a constant succession that can last (up to nine months in Italy’s case, where heavier animals are killed).
Sudden death due to HBS is a devastating, stealthy phenomenon that affects pigs in growth and finishing phases. The heaviest animals die, sometimes a few over several days, or a few per week, but in a constant succession that can last (up to nine months in Italy’s case, where heavier animals are killed). It is believed that the majority of farms have a mortality rate between 0,1 and 7 %. The etiology is complex and, in this sense, can be classified:
a) dry feed in the form of meal, low risk,
b) dry feed in the form of pellets, medium risk,
c) dry feed in the form of meal or pellets, high risk, and
d) liquid feed, extra high risk, and which this article is about.
Causes of Hemorrhagic Bowel Syndrome
The first reports linked the increase in mortality due to HBS to dry pellet feed, but above all to the use of liquid whey. On the other hand, the mortality rate increased with the use of fresh whey but not with the use of whey acidified due to natural storage. The hypothesis included allergenic mechanisms, infective mechanisms, the presence of micotoxins, hemorrhagic forms sensitive to vitamin K and the presence of intestinal twisting. The presence of intestinal twisting was converted into an almost constant (table 1). An important observation, since it describes an intermediate stage of the phenomena. The pig, therefore, is prone to intestinal twisting but, in spite of this natural tendency, there is always a trigger.

Table 1. Predisposing factors for HBS according to diverse sources.

Source Predisposing factors for HBS
Kinnaird, 1964
Whey and pellet feed
Jones, 1967
Whey (fresh, non-acidified)
O’Neill, 1970
Allergic form
Smith e Shanks, 1971
Intestinal twisting
Rountree, 1972
Infections
Rowland e Lawson, 1973
Intestinal twisting
Kurtz, 1976
Vitamin K deficiency
Todd e coll., 1977
Whey and intestinal twisting
McCausland e Southgate, 1980
Whey
Gebhart e coll., 1983
Infections
Wendt, 1987
Whey
Ligget, 1989
Micotoxins
Drochner, 1990
Whey
Hani e coll., 1993
Whey and intestinal twisting
Sansot e coll., 1997
Whey and intestinal twisting
Buddle e Twomey, 2002
Whey
Straw, 2002
Intestinal twisting
Straw 2004
Intestinal twisting
Couture e Le Treut, 2008
Elevated ambient temperature
Labuscagne, 2009
Elevated ambient temperature

Let’s hypothesize a practical, frequent case of food competition. The fight for a portion induces the dominant animal to consume a large quantity of food in a very short period of time. This entails incomplete digestion due to insufficient acidification. This reduces the antibacterial action of hydrochloric acid in the stomach. This, added to the abundance of nutrients, stimulates the multiplication of bacteria, which produces an enormous quantity of gas, in the stomach as well as in the intestines. These gas bubbles make intestinal mobility difficult, stopping the pumping action and the progression of the food. This stagnation produces even more gas. The elevated pressure due to gas can produce lesions in the intestinal wall, or even displace the stomach or intestine upwards. The pressure exerted on the abdominal organs can involve vascular obstruction, slowing down blood circulation or compressing the thoracic cavity, producing dyspnea (see image). Death is quick due to circulatory collapse, or respiratory insufficiency. If this sequence of facts is plausible, competition at the trough, as well as feed contamination, play a key role. Summer temperatures as well as some particularly fermentable ingredients can worsen the situation.



Liquid feed as a specific risk factor
Ever since we are little we learn the principal notion of biology; water is life. Later, we tend to forget this. This explains our less than adequate preparation for the handling of wet and liquid feed. In addition to water, we should also have in mind the optimal fermentability of the base feed and its development with the use of some sub products of the sugar, beer, lactose, and starch industries. The fermentation helps one to understand why the use of whey was perceived as an aggravating factor in HBS. The microbiological instability of liquid feed has led manufacturers to design equipment with wash systems. However, the residue of the wash with water either goes directly back to the tank or temporarily accumulates in a recuperation cistern, although normally, the recovered material ends up in the cistern for the next turn. This wash water is a formidable breeding ground, and this is another critical point. Washing can be followed by disinfection which, in order to be efficient, cannot be too radical. The residue that is left on the line will feed microbial activity to massive multiplication where all of the acidophilus and coliform species will fight for supremacy. This is another critical phase, since the instability could allow for the rise of a pathogenic strain. After this tumultuous stage, there will be a rather stable community of microorganisms that can provide a natural defense against pathogenic strains.

Control of the mortality rate due to HBS with liquid feed
A generic predisposing factor, such as food competition, is added to the use of a product that easily ferments. Preventing death due to HBS implies acting on both factors. Firstly, avoid overcrowding and guarantee enough space at the trough for all of the pigs (table 2); insufficient space at the trough will increase competitiveness. The pump should be strong enough to distribute the feed homogeneously along the length of the trough (dominant animals, with a higher risk of HBS, should be placed in the center). The cleanliness of the trough, being free from fecal matter and urine (that get pushed to the sides, making those positions less attractive) improves the regular consumption of the group.

Table 2. Trough dimensions
Live weight, kg Front of trough, cm/head
(6,7 * kg live weight 0,333)
Width of trough
(distance between inside edges), cm
30
20.8
25
55
25.5
25
70
27.7
25
100
31.1
25
110
32.2
30
120
33.1
30
140
35,0
30
160
36,5
30

However, the decisive question is the microbiological control of the food and the digestive system, the stomach in particular. Antibiotic treatment prevents death due to HBS, just as in the past strong biocides like formaldehyde were used for prevention. But nowadays we cannot use antibiotics on a daily basis, so we have had to modulate the microbial presence in feed and on the installations, encouraging a biofilm ideal for the development of lactic acid producing bacteria. Disinfection should be limited to emergencies only; it will be more useful to support compatible microflora. Acidification, for example, is effective although organic acids are not recommended: citric acid and fumaric acid are good promoters of yeast growth, while acetic acid and propanoic acid are not of much interest. Formic acid in low concentrations (0,1 %) presents no contraindications.

The ideal would be the addition of a substance that inhibits the yeast without affecting the lactic acid producing bacteria. In this sense, water treated with potassium sorbate and sodium benzoate could be useful, at 0,15% and 0,05% respectively. In this way the use of selected lactic acid producing bacterial cultures is effective only in the bacterial strain stands out in the production of lactic acid. The cost of these additives is probably justified during hot weather, depending on the specific conditions of each farm.

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