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2 Nutrition

Introduction

Pigs are omnivores. Wild species in their natural environment eat a very wide variety of foodstuffs. Domesticated pigs are kept in very varied environments from extremely large commercial breeding and fattening units through to smallholder units with pigs living very closely with humans in rural environments, to pet pigs living very close to their owners. Their nutrition will vary in a similar manner, with very high scientific diets and at the lower range ad hoc diets. In all situations it should be stressed that pigs should NEVER be fed any household scraps containing meat products because of the danger of the spread of pandemic infectious diseases, e.g. FMD, classical swine fever (CSF) and African swine fever (ASF). In most countries these diseases are notifiable and there is legislation banning not only the feeding of household scraps but also the feeding of commercial waste products called swill.

The full nutritional requirements for all types, ages and breeds of pig are beyond the scope of this book. Diseases of the neurological system and the skin as they are related to nutrition are listed below and also will be cross-referenced in Chapters 11 and 12.

Water

Good-quality water must be freely available even if pigs are being fed wet feed. This includes suckling pigs. These require 60 ml/kg daily. Weaners weighing 15 kg require 2 l daily. Fat pigs weighing 90 kg require 12 l daily. Non-pregnant sows require 12 l daily, pregnant sows require 20 l daily and lactating sows require 40 l daily. This is an important welfare requirement. Interruption of water availability will cause the acute neurological problem of salt poisoning.

Food Requirements

Nutritional deficiencies and excesses

These are rarely a problem in well-run commercial herds. They only become a problem when errors occur, e.g. in mixing of food when home mixing is carried out or spillage of food when moulds may become a problem; lack of cleaning of food bins will also add to this problem. When pigs escape there are likely to be problems with excess food and toxicity from eating garbage, etc. Nutritional problems are much more common in smallholder operations, e.g. when too much bread is fed from bakery waste. Practitioners should question pig keepers carefully in a no-blame manner to see if nutritional requirements of pigs have been met. Any bought food should be examined carefully for any physical problems. If need be, samples may be taken for analysis.

In the commercial world the genetics of pigs are constantly being upgraded. It is important that diets are constantly reviewed as well.

Minerals

The total requirements are regularly revised. The minerals normally listed are: calcium, cobalt, copper, iodine, iron, magnesium, manganese, phosphorus, potassium, selenium, sodium and zinc.

Vitamins

As with minerals, the levels required are constantly being reviewed. The normal vitamins quoted are: vitamin A, vitamin D₃, vitamin E, vitamin C, vitamin K, vitamin B₁₂, thiamin, riboflavin, nicotinic acid, pantothenic acid, pyridoxine, choline, biotin and folic acid.

Amino acids

The requirement of essential amino acids is an emerging science. The two which are normally quoted are linolenic acid and arachidonic acid. However, new information is constantly being made available.

Pigs in the late finisher stage are often growing quickly towards market weight, at approximately 1 kg/day, with much of this growth being muscle development. This necessitates high levels of amino acid (AA) intake and uptake, and requires dietary attention to both high-protein feed components (such as soybean or fish meal) and also an AA feed supplement, particularly the first-limiting AAs lysine and threonine. Many commercial synthetic AA supplements contain lysine, threonine and other components. Incorporation of some larger muscled pig breeds, such as the Pietrain, into farm breeding programmes may lead to higher incremental needs for these supplements. The usage of the metabolic partitioning agent ractopamine in some markets (non-European) plays a further major incremental role in this AA uptake requirement (Corona et al., 2012).

Finisher feed costs are widely recognized as the major factor in the cost of the production of market pigs. The rapidly rising costs and diminishing availability of some of the high-protein components of these feeds have led to a search for strategies to reduce the necessity for excessive lysine and other AA intakes (Niven et al., 2006). The numerous enterobacteria, such as those located in the pig intestine, can act to decarboxylate AA, producing biogenic amines such as cadaverine (Santos, 1998; Marino et al., 2000). One of these lysine-conserving strategies is, therefore, to identify feed additives that may reduce the bacterial degradation of AA intake during their passage in the gastrointestinal (GI) tract. The sanguinarine alkaloids (derived from Macleaya cordata and related plants) were developed in the 1980s and 1990s for incorporation into a variety of commercial oral anti-inflammatory products. More recent development of these alkaloids has been for animal feed additives, partly as an anti-inflammatory agent (Chaturvedi et al., 1997). Also, an in vitro study suggested an ability of these alkaloids to reduce the activity level of AA degradation enzymes, such as decarboxylase, located within the GI tract (Drsata et al., 1996). However, investigation of the activity of these alkaloids within feed additives, aimed at reducing the degradation of dietary tryptophan during its passage through the pig, found no useful influence on performance (Blank et al., 2010). Further research needs to be carried out to make certain these substances are really worthwhile in pig diets.

Nutritional induced diarrhoea

Naturally, clinicians should make sure that the diarrhoea has no infectious cause. Probably the most common non-infectious cause of diarrhoea is an imbalance of cereals, particularly a high wheat inclusion. Also new crop cereals, particularly barley, may cause problems. The reason for these problems is the presence of non-starch polysaccharides. These are xyloses and arabinoses, which are not digestible by pigs unless cooked. In the raw state they pass through the small intestine and absorb water. When they reach the large intestine they are altered by bacteria and release the water. The pig is not able to absorb all this and so diarrhoea occurs. The excessive use of soy meal to increase protein levels may cause colitis. Pig keepers are always complaining about high levels of manioc. However, there is little real evidence that manioc does cause colitis. There is evidence that rape meal in excess will cause colitis. The proven level is over 5% w/w of the diet. Such a high level is extremely unlikely unless there is a real mistake at the feed mill. Of course, an excessive feed intake will cause diarrhoea.

Colostrum

The importance of colostrum to the neonatal pig cannot be overstated. Adequacy of colostrum quantity and quality can and should be measured by blood testing piglets. The test used is the zinc turbidity test. Gilt colostrum is liable to be of poorer quality than that of sows, so it is important to evaluate gilt colostrum by blood testing pigs from gilts as well as from sows. Milk continues to play an important role in providing antibodies to the mucus layer of the gut, which protects against infection. It is important that lactating gilts and sows are given adequate nutrition as well as access to fresh clean water at all times. Piglets reared away from a sow will survive if given adequate colostrum (Fig. 2.1).

Neurological Diseases Caused by Changes in Nutrition

Copper deficiency myelopathy

This is extremely rare. It may be associated with iron deficiency in commercial indoor pigs. Pigs may be found dead or convulsing from heart damage.

Copper toxicity

This is now rare as copper is no longer used as a growth promoter. Signs are anorexia and depression. The signs disappear rapidly when excess copper is removed from the diet.

Fig. 2.1. Piglets reared away from a sow will survive if given adequate colostrum.

Hypoglycaemia

This is seen in neonatal pigs which have not received adequate energy, e.g. in very cold conditions when a sow has farrowed outside in winter. Convulsions will be seen in piglets. Hypoglycaemia can also be brought on by low levels of various infections in piglets. The farrowing fever complex syndrome, which will decrease milk output, will put piglets at risk. Treatment is proprietary energy fluids by mouth or in extreme cases injections of 15 ml of 5% w/w glucose intraperitoneally (ip) every 4 h.

Osteomalacia

This condition will mainly be seen in very badly fed adult, aged backyard pigs. Calcium has to be virtually absent from the diet. The bones are very brittle. The pig may have multiple long-bone fractures and be unable to rise (Fig. 2.2). Prompt euthanasia is the only course of action.

Vitamin A deficiency

This will cause blindness and so the pigs will appear to show nervous signs. The condition is certainly a possibility in badly fed backyard pigs. Once there is blindness recovery is impossible, even with vitamin A injections. Single or pairs of affected pigs might be thought to have a reasonable quality of life but euthanasia should be seriously considered.

Vitamin B deficiency

This may occur in backyard pigs fed either a very fatty diet or solely on bread. Normally pigs go off their hind legs; this is followed by a progressive paralysis. They may recover with good nursing and a proper diet.

Vitamin K deficiency

This occurs as a result of eating rat bait containing warfarin.

Skin Diseases Caused by Changes in Nutrition

Biotin deficiency

The main signs are hair loss and hoof lesions. Normally hoof lesions precede hair loss. Treatment with biotin in the food readily controls the condition and can be used as a diagnostic tool.

Fig. 2.2. This pig is not receiving an adequate diet and is suffering from osteomalacia.

Iodine deficiency

This is an extremely rare condition of piglets born to iodine-deficient sows. The piglets will be hairless but will not show goitre.

Parakeratosis

This is caused by a deficiency of zinc in the diet or by a conditioned deficiency from high levels of phytic acid in soy. It is found in young growing pigs and is manifest as scaly papules. Diagnosis should be made with a skin biopsy as testing the blood for zinc levels is unreliable. Treatment is restoring the zinc level in the diet to 100 ppm taking into account the level of soy in the food. The response to treatment can be used as a diagnostic tool.

Vitamin A deficiency

This is extremely rare and is manifest as a generalized seborrhoea. It is seen in weak piglets born to deficient sows. Other signs of vitamin A deficiency, e.g. neurological signs, particularly blindness, are going to be much more obvious than the skin disease. The neurological signs are irreversible.

Vitamin B deficiency

Other than biotin deficiency, which is relatively common, deficiencies of niacin, pantothenic acid and riboflavin have been reported as well but they are extremely rare. Skin disease signs are very variable but are usually seen as dry scaly areas. Total recovery will occur if the diet is corrected.