Spring 2006

General News  

When I put pen to paper for the last edition of SPESFEED News I predicted that the maize market could be “interesting” in the months ahead.  The truth is that few of us expected the Rand to weaken as suddenly or as sharply as it did in June.  Neither did we expect the crop quality to be as poor as it has been.  The nett result has been a steady upwards movement in the cost of maize and of feed prices in general. Sadly, many of us have been caught without adequate forward cover.

This needs to be viewed against a background of expansion in all forms of intensive animal production and the likely effect this may have on product prices.  On the positive side, the price of both beef and mutton has been high and the cost of importing meat products will have increased in sympathy with the weakening Rand .  I believe that things may well become a little trickier in our industry over the next few months.

By coincidence, this edition of the SPESFEED News has much to do with gut health, both in broilers and in pigs.  This topic has assumed considerable importance to producers in both sectors.

Biofuels

The production of Biofuel is likely to have an impact on the animal feed industry both locally and globally.  Those of us involved in agribusiness need to be aware of the impact it may have on our businesses.

I have associated with alternative energy sources since my father built a solar water heater in the 1960’s.  As a boy, I found myself climbing around in the roof lagging pipes and being abused for having 5 thumbs on each hand.  Despite this, I managed to develop an enduring interest in alternative energy sources.  I have recently been studying internet sites that show you how to build a bio diesel plant in your kitchen (it is that simple).

So what has this to do with our industry?

The truth is that there is increasing pressure on governments and individuals to use alternative or renewable energy sources. Not only is there concern that the supply of fossil fuel is limited, but there is also a real concern about the emission of greenhouse gases and global warming. There is a worldwide trend towards the production of energy from alternative sources.

The use of solar energy is well established, clean but relatively expensive. I have a solar lighting system in my cottage on the farm which works well, but has some limitations with regards any application that requires serous power.  In short, we need to find an alternative to fossil fuel to meet the energy demand for things like cars, heating and refrigeration.

The second alternative is the production of biodiesel from fats and oils. Sasol is investigating building a plant for the production of biodiesel using soybeans.  However, it is possible to use oil from sunflowers, used restaurant grease and fat and other sources to produce biodiesel.  The British supermarket chain ASDA is investigating turning the fat derived from their chicken roasteries into biodiesel.  They may not sell this fat for use in animal feed and shortly they will not be able to dump it in landfills.

The developments in the move to more biofuel production will have an impact on our industry in a number of ways:

Glycerine, one of the by-products of biodiesel product can be used in soap and cosmetic manufacture.  Supply will probably shortly outstrip demand though. Recent work at the University of Arkansas has shown that this carbohydrate source (it is glycerol after all) can safely be added to the diets of chickens. In a recent study in broiler chickens, it was shown that diets containing 

Rick Kleyn

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Feed Passage in Broilers

"Feed passage," or, more accurately, the passage of undigested feed in the faeces of broilers, continues to be reported. In the past its occurrence has been linked to the feeding of poor grain, but this is not the only cause.  Several factors may work in concert and limit the broiler's ability to digest and/or absorb feed. Investigation of the cause(s) requires gross examination of the affected poultry.  This entails either true diagnostic work, or more often, subjective observation.

Symptoms include the passing undigested feed in the faeces.  This includes large grain particles, excess moisture, a characteristic green colouration with orange mucus, and poor formation to the faeces. Affected broilers have poor pigmentation, poor feed conversion, and lower body weights with variable uniformity. On necropsy, lesions are commonly found in the proventriculus and gizzard of affected broilers. They are also found in the small intestines.

The severity and clinical manifestations of the disease vary depending on management practices, presence of concurrent diseases, and specific shipments of grain. A series of factors need to be considered when passage of undigested feed is to be investigated.

Feed passage syndrome in broilers can be defined as "the passage of nutrients in faeces due to improper digestion and/or absorption in the intestines."  The cause of the syndrome is the broiler's inability to digest or to absorb the feed, or both. The syndrome may result from a single factor or a combination of factors.

Many infectious and nutritional diseases cause primary lesions in the gut. Feed passage is a general term not associated with a specific disease syndrome but rather occurs during many diseases. Feed passage results from some abnormality in the digestion and absorption of nutrients, and although the causes may be numerous, the clinical expression in the broiler is simply feed passage.

Heat Stress:   This causes broilers to increase water consumption in an effort to cool down. Much of it will be voided in the faeces, causing them to be wet and poorly formed. Physical changes in the intestinal lining can be detected histologically within 48 hours of heat stress and can be observed for at least 3 days. Changes include a decrease in villus length and surface area.

Dietary Salt Intake: An increase in salt consumption, in the feed or water, causes birds to consume additional water to assist in its elimination. This is voided by way of the faeces, resulting in them being wet and poorly formed.

Ascarids and Cestodes:  Intestinal parasites can irritate the gut and cause passage of undigested feed. A mild infestation of ascarids is enough to cause irritation and feed passage. A significant cestode infection must occur before losses are recognized.

Viral Infections: A number of viruses, including reovirus, calicivirus, adenovirus, parvovirus, enterovirus, coronavirus, and togavirus are associated with broiler feed passage. Historically, reovirus has been considered a primary viral cause of broiler feed passage or "malabsorption syndrome." However, it is now clear that this virus does not play a significant role. Some investigators have described this virus as "one in search of a disease" as it is wrongly blamed for many syndromes in poultry.

Bacterial Infections: Bacterial enteritis often occurs secondary to viral or coccidial infections. The intestinal tract houses a large bacterial population that is necessary for its normal gut function. An imbalance in this flora can result in disease. Prevention is best achieved with effective use of growth promoters, control of coccidial infections, protection of immune system integrity, and biosecurity practices.

A specific bacterial infection in the gut that is increasing in incidence in recent years is Necrotic Enteritis (NE), caused by C. perfringens. This bacterium is common in the environment and is considered part of the normal gut flora of poultry. A number of predisposing factors are recognized;  

Tannins:  Tannic acid is found in the coatings of grains, especially some varieties of sorghum. Toxic levels of tannins in the feed cause oesophageal and gastric oedema, hemorrhagic ulceration, necrosis and sloughing of the mucosal lining, hyper secretion of mucin, and crop wall thickening. This damage results in feed passage.

Biogenic Amines:  Are present in low levels in animals, plants, and micro-organisms. At higher concentrations they are toxic. They cause more problems in hot weather when there is increased bacterial degradation of free amino acids, dietary proteins, and animal by-products. Lesions associated with feeding toxic levels of biogenic amines include proventricular enlargement, gizzard erosion, sloughing of intestinal epithelia, poor weight gain and feed conversion, impaired immune response, and diarrhoea. Affected birds are poorly pigmented and have low body weights and FCR conversions.

Gizzerozine:  This toxin is produced in over-processed fishmeal. It has an effect similar to the biogenic amine, histamine, in causing overproduction of hydrochloric acid in the proventriculus and resulting gizzard erosion.

Rancid Fats: Rancid fats are a common cause of feed passage, especially in hotter climates where fats readily become rancid if not stored properly. The process involves the oxidizing of dietary fat and fat-soluble compounds to produce free radicals or reactive oxygen molecules. Examples include the surperoxide radical (O₂) and hydrogen peroxide (H₂O₂).  Lesions include proventriculitis, gizzard erosions, and enteritis. Impaired immunity, poor growth, poor feed conversion and poor pigmentation may occur.

Litter Quality:  Litter is often consumed by chicks before they find feed and water.  Ensure litter is of high quality, free from foreign materials, and fresh.  Ingestion of contaminated litter can cause irritation of the gut linings of the young chick, resulting in poor nutrient absorption.

Management practices can play a major role in preventing feed passage. It directly affects the most important broiler economic performance parameters, feed conversion and body weight. When feed passage is observed in broiler houses, evaluating basic management practices may be the most efficient manner to resolve the problem.

    G. Butcher, A. Nilipour, R. Miles

University of Florida

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Balanced Protein, Pellets and Mash in Broilers

In a recently published paper Lemme and his co-workers examined the response of broilers to increased levels of balanced protein (BP) offered as either a coarse mash or as pellets of varying quality.

Bird performance levels can be improved by increasing BP levels, where BP is defined as the whole balanced amino acid profile.  However, response to BP may be limited by other nutritional, environmental or management factors, and it was hypothesised that feed form, particle size and the use of certain ingredients may be among those factors.

These diets represented 90, 100,110 and 120% of the CVB (2000) recommendation.

Table:  Summary of the composition of the diets used in experiment 1

In experiment 1, diets were fed either as coarse mash, poor pellets or good pellets.  Good pellets were characterised by high durability.  In the second experiment, diets were fed as either good quality pellets or coarse mash.  In the case of the mash, particle size distribution was either kept constant with increasing BP, or changed by increasing the proportion of soybean meal.

All of the results achieved exceeded the Ross recommendation. All effects that measured in both experiments were significant.  Feed intake generally decreased with increasing BP and that feed intake was highest in the case of good pellets and lowest in mash fed birds.

Although there was a small response in weight gain of mash fed birds, feed conversion improved substantially for all feed forms with increasing BP.  In experiment 2, particle size distribution in the mash made no difference to bird performance. There was an almost linear decrease in abdominal fat content indicating improvements in energy use with increasing BP levels.

The data from both experiments would suggest that regardless of the physical feed form, increasing BP levels to up to 120% of the current CVB recommendations had beneficial effects on broiler performance.  When pellets of poor quality are fed, higher levels of BP are required to achieve the same performance levels. 

Lemme, Wijtten, van Wichen, Petri and Langhout (Poultry Science 85: 721 -730)

Figure: Feed intake, weight gain, and feed conversion ratio  responses to increasing levels of balanced protein offered as coarse mash, poor quality pellets, and good quality pellets.

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Post Weaning Syndrome in Piglets

An important aspect of the resistance in the gut against PWS is a diverse and stabile microflora, by which ‘competitive exclusion’ is generated and growth and attachment of (pathogenic) bacteria is counteracted. Newly weaned piglets may suffer from PWS because of the immature development of the gut and inadequate capacity to digest a ‘vegetable’ diet. Gut damage is also caused by the weaning process. As a result, the colonization resistance is disturbed and E. coli can proliferate and attach to the enterocytes.

In newly weaned piglets the gut can be damaged by the reduced feed intake immediately post weaning and the subsequent increase in the their susceptibility to infections like Rota virus. Weaning itself is stressful. The villus height is reduced, crypt depth is increased, and the rate of mitosis is increased. In addition, the ability of the gut to digest a solid diet is inadequate. These processes result in mal-digestion, malabsorption and increased undigested food in the ileum. This substrate induces an explosive growth of bacteria and a disturbance of the colonisation resistance. Normally transient E. coli strains in the gut multiply and attach. The toxins produced by these bacteria are responsible for the PWS symptoms.

Specific measures with regards feed composition and feeding strategy are discussed. These may have variable effects under practical conditions.

Improvement of gut development and prevention of gut damage at weaning:  When weaning occurs around three to four weeks of age, it takes 10–14 days before gut development matures enough to digest vegetable diets. In addition, the villus height is impaired because of low feed intake, infection, stress etc. Feed and hence energy intake is often below the maintenance requirement for the five days after weaning. Thereafter feed intake increases but gut development remains inadequate.  This creates an overload on the digestive system.

Improvement of digestion and absorption in the gut, reduction of the amount of substrate:  The impaired digestive and absorptive function of the gut can (partly) be  compensated by the provision of highly digestible diets or by the addition of supplements stimulating digestion. These measures diminish the amount of substrate and reduce the risk of bacterial growth. The following can support improvement of the digestibility:

Inhibition of the growth of pathogenic bacteria:

Growth of Enterobacteriaceae like E. coli is inhibited below pH 4 (acid). Because of the faecal-oral recontamination, the stomach plays an important role in the infection cycle and an adequate function of the stomach.  Additives like organic acids and other measures with bacteriostatic or bacteriocidic may be used:

Improvement of colonization resistance:  A diverse and stabile microflora can prevent the growth and attachment of pathogenic bacteria. Bacteria regarded as beneficial create a less favourable gut environment or Enterobacteriaceae.  Lactobacillae are regarded as positive bacteria as they produce lactic acid and bacteriocins which suppress the growth of E. coli.  Improvement of colonisation resistance can be achieved as follows:

Decrease the attachment of bacteria and increase immune response:  Certain additives reduce the attachment of bacteria to enterocytes. The systemic and local immune response can be influenced by certain nutrients.

Many of the feed additives mentioned- enzymes, probiotics, nucleotides etc. - have variable effects under practical conditions. Factors influencing the effectiveness of these feed additives are the nature and amount of the substrate in the diet, the effective pH in the digestive tract, housing conditions and infection pressure from the environment. More insight and research is required for an appropriate evaluation and practical application of the measures mentioned.

Drikzwager, Veldman and Bikker

Animal Research: 54 231 -236

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 Report on trip to Europe

In September I was fortunate enough to attend two back-to-back conferences in Europe .  The first was the World Nutrition Forum, hosted by Biomin in Vienna and the second was the European Poultry Science meeting which was held in the ancient city of Verona in Italy. I only intend to pass on some interesting snippets here.  Should you require more information I have copies of the proceedings of both meetings.  

Dr Nick Dale from Georgia showed some data that was a little worrying.  He believes that the production of ethanol and biodiesel in the US could well lead to a shortage of grain and oil as energy sources for the US poultry industry.  He also alluded to the skills shortage in the poultry industry stating that the poultry industry was perceived as “not sexy” and that the image of “chicken farming” prevented people from understanding that we deal with the dynamic

Dr Jim McAdam of Aviagen presented data on where the Ross breed has come from and where it is likely to go to infuture.  Although most of us have seen information of this sort in the past, it does not look as if we have reached a

Rick Kleyn