Sustainable feeding of swine

17.6.3.1 Feeding pigs in the context of ammonia emissions

Rational feeding of pigs is expected to benefit animal health, and production results in the form of weight gains and high-quality slaughter products (pork), while reducing negative environmental impacts. A 1% decrease in protein in pig diets has been shown to result in 10% lower ammonia (NH₃) emissions. Lowering the level of total protein in the feed requires the use of feed materials with higher protein digestibility and a certain ratio and concentration of essential amino acids. In practice, such a procedure can be technically difficult to perform due to limited access to the relevant components. The protein content of the ration can also be reduced if the supply of amino acids is optimised by adding synthetic amino acids (e.g., lysine, methionine, threonine, arginine, and tryptophan), but this increases production costs.

Multiphase feeding involves carefully balancing nitrogen to the physiological capacity of the animal’s body to take it up. The introduction of 3 or 4 types of feed with varying protein concentrations, instead of the usual 2 types for a given technological group of pigs, reduces the amount of nitrogen excreted, and thus ammonia emissions, while maintaining productivity levels and reducing feeding costs.

The multiphase feeding does not require special arrangements in the organisation of nutrition and is carried out just like conventional nutrition. The effect of introducing multiphase feeding is estimated at a 15% reduction in NH₃ emissions for the 2-phase feeding of piglets and 25% for the 3-phase feeding of fattening pigs. Regardless of the scale and concentration of production, multiphase feeding can be effectively implemented on large and small farms.

In terms of reducing nitrogen excretion, additives of synthetic proteolytic enzymes are used, breaking down usually inaccessible organic combinations of protein compounds. Some organic acids (e.g. benzoic, lauric) have a slightly different effect. Used as feed additives, they lower the pH of faeces, reducing the effectiveness of urease and thus ammonia emissions. The same is true for saponins, which have a beneficial effect on the microflora by reducing protein fermentation in the large intestine. They modify not only protein metabolism but also carbohydrate assimilation.

17.6.3.2 General principles of pig nutrition

The living and production needs of pigs must be met at every stage. We consider living needs to be the factors necessary to maintain physical fitness and vital functions. Their level is affected by body weight, ambient temperature, level and type of animal activity. Production needs are nutrient requirements to produce output – weight gain. This value varies with the age of the pigs, sex and housing conditions.

The most important principles to consider when feeding pigs:

1. Feed rations should be balanced following current nutritional standards and adapted to each technological group.
2. Individual feed must be of the best quality, and nutrient deficits in the basic feed must be supplemented.
3. Feedstuffs must be stored under hygienic conditions, according to the manufacturer’s recommendations.
4. The fineness of the feedstuff affects the level of digestibility of its components.
5. Pigs must have constant access to fresh water.
6. Feed should be provided in such a way as to avoid fighting in the herd and ensure equal access for all heads in the group (coop).

Basic requirements for feeding pigs according to the Pork Quality System (PQS):

1. Balanced and biphasic feeding to maximise the animal’s genetic potential for muscularity and to prevent meat quality defects and excessive fattening of pigs, including intramuscular fat deposition;
2. Fishmeal must not be used in the last fattening period (the last month before slaughter) and limit the proportion of corn to a maximum of 20% in the ration.

Basic requirements for nutrition according to the Quality Assurance for Food Products (QAFP, 2019):

1. It is necessary to provide animals with feed whose quantity and nutritional value are adapted to their species, age, body weight and physiological state,
2. Pigs are fed a minimum of once a day,
3. Pigs kept in groups have simultaneous access to feed,
4. Equipment and devices intended for feeding and watering animals shall be placed in such a way as to minimise the possibility of contamination of feedstuff or water and to facilitate conflict-free access of such animals to feedstuff and water,
5. Premixes used in pig nutrition may contain other legally permitted substances in addition to vitamins and mineral salts,
6. It is prohibited to add feed additives not listed in the Register of Feed Additives and materials listed in Annex 3 to Regulation (EC) No 767/2009 of the European Parliament and of the Council of 13 July 2009 on the placing on the market and use of feed, amending European Parliament and Council Regulation (EC) No 1831/2003 and repealing Council Directive 79/373/EEC, Commission Directive 80/511/EEC, Council Directives 82/471/EEC, 83/228/EEC, 93/74/EEC, 93/113/EC and 96/25/EC and Commission Decision 2004/217/EC (OJ EU L 229, 01/09/2009, p. 1, as amended).
7. Due to the muscularity of the carcass and feed use, fattening should be completed when the body weight reaches 95-135 kg.

Ration balancing is to cover the living and production needs – it should be done at least in terms of basic components such as metabolic energy, total protein, and essential amino acids (lysine, methionine, cystine, tryptophan and threonine). This applies to the economic preparation of feed and complete mixes. Professional computer programs for balancing rations are helpful. These calculations can also be made using the “Pig Feeding Standards” or the “Feeding Recommendations and Nutritional Value of Feedstuffs for Pigs”. Complete mixes are widely used and are well-balanced in terms of basic nutrient content. This solution is the least complicated but requires specific “technology” in the piggery. It is also possible to prepare feed mixes on one’s own based on bruised grains and purchased concentrates (containing significant amounts of protein) or premixes, which are a source of essential amino acids, vitamins and other nutrients. Concentrates are added at 10-15% and premixes up to 3%. Grains are the basis of such nutrition, but there is variability in the nutrients they contain. Therefore, it is recommended to perform analyses of the basic composition of the cereals used in specialised laboratories.

Feed that provide energy, protein feed and other types of feed, as well as feed additives, are used in pig nutrition. Grain is the most commonly used component in feed mixes for pigs. This is due to its availability, ease of storage, composition, etc. Cereals have a high nutritional value. However, it must be taken into account that before using different types of grain, special attention should be paid to its quality (chemical composition, mycotoxin contamination, presence of pests in it, etc.), as well as proper preparation and processing of the grain by kibbling. Barley and wheat grains can be counted among the staple grains in pig nutrition. They have a high energy value (12-13.5 MJ EM) and total protein content of 11-13%, some varieties even >15%. These cereals are suitable for fattening. Corn grain is typically a carbohydrate feed, but it also contains quite a lot of fat (up to 5%) and little fibre. It has the highest energy value of all cereals. It contains relatively little protein (up to 9.0%), and due to the deficiency of essential amino acids, has a low biological value. Like the grain of other cereals, it is poor in minerals, which should be taken into account in balancing mixes. Corn grain contains almost no antinutritional compounds and has high digestibility, and can be used in the feeding of all groups of pigs. Too much corn in the feed ration for fattening pigs can result in a deterioration of carcass quality. Oats contain 11-12% protein, little starch and about 4% fat. Due to its high crude fibre content (10-12%), its share in rations for growing pigs is limited to 5-10%, and for sows to 15%. In addition to starch, carbohydrates include simple sugars and dietary fibre consisting of non-starch polysaccharides. Starch in pigs is digested in the small intestine in 97-99%, non-starch polysaccharides in 0-21%, including glucans in 17-31%. Arabinoxylans are digested in the large intestine. Microorganisms participate in this process, resulting in the formation of large amounts of short-chain fatty acids in this part of the gastrointestinal tract. In the gastrointestinal tract of pigs, these acids are quickly absorbed, but the energy contained in them can cover the energy needs of animals only by 10-25%.

Protein feed mainly includes post-extraction meals, such as soybean and rapeseed, as well as seeds of bean crops. Post-extraction soybean meal is an extremely valuable protein feed. It contains 12.1-12.9 MJ EM and 35-43% total protein. The biological value of this meal’s protein is limited by its low methionine and cystine content (1.02-1.25%). Post-extraction rapeseed meal is also a major source of protein in pig nutrition, containing 10.8 MJ EM and 32-37% total protein. The amino acid composition of this meal is very beneficial. The level of rapeseed meal used is 8% in rations for gestating sows, 5% for nursing sows, 10% for piglets, and up to 15% for fattening pigs. In the feeding of pigs, the seeds of lupins (yellow, narrow-leafed), which have a high content of total protein, but contain anti-nutritional alkaloids, can be used  A good source of protein is pea grains, but they come at a high price. Potato concentrate, dried distillers grains with solubles, dried yeast, plant and fish concentrates can also be used in pig feeding.

Content of metabolic energy, total protein and selected essential amino acids in feedstuff materials.

Material	Metabolic energy (MJ)	Total protein (g)	Lysine (g)	Methionine (g)	Threonine (g)	Tryptophan (g)
Barley	12.74	110.0	3.8	1.8	3.6	1.4
Rye	13.25	95.0	3.7	1.6	3.2	1.0
Triticale	13.78	122.0	4.1	1.8	1.2	3.9
Wheat	14.03	119.0	3.3	1.9	3.4	1.3
Oats	11.25	118.0	4.7	1.9	4.0	1.5
Wheat bran	8.75	143.0	5.7	2.1	4.5	2.3
Post-extraction soybean meal	13.32	452.0	19.8	7.7	16.1	4.8
Post-extraction rapeseed meal	10.50	364.0	27.1	6.1	17.5	5.9

In the practical feeding of pigs, attention should be paid to antinutritional compounds, the content of which varies considerably depending on the plant variety. For example, legumes can contain trypsin inhibitors, broad beans and pellets – tannins, rye – resorcinols, non-starch polysaccharides, trypsin and chymotrypsin inhibitors. The harmfulness of anti-nutritional compounds involves reducing the palatability of feed (some of them have a bitter taste, such as faba bean tannins and lupin alkaloids), worsening the digestibility of nutrients (especially protein), disrupting digestive processes (protease inhibitors, pentosans). They also often have toxic effects on the animal’s body (e.g. alkaloids, glucosinolates). Mycotoxins (mainly – ochratoxin A, deoxynivalenol, and zearalenone), compounds that are metabolites of fungi present in feed materials, are also significantly harmful. They have carcinogenic, teratogenic, and immunosuppressive effects, and cause disorders and permanent changes in the functioning of many internal organs. Zearalenone in sows causes disturbances in reproductive processes (e.g., ovarian lesions), possibly even causing agalactia or permanent infertility and even miscarriages. It is important to provide animals with feedstuffs free of mycotoxins. Of course, substances that bind these toxins can be used as feed additives; this method is recommended as a last resort and can only be applied in fattening.

Feed enzymes have been added to feed mixes for many years. Introduced with the feed into the digestive tract of pigs, they contribute to the following benefits: distribution of cell membranes and dietary fibre fractions (β-glucans, cellulose) in the feed, better feed utilisation (up to 8%), improved weight gain, reduced diarrhoea, the possibility of replacing more expensive feed with cheaper ones, increased feed nutritional value, especially metabolic energy levels, better mineral absorption. The most commonly used in pig feed are b β-glucanase, xylanase, phytase and cellulase. The β-glucanase enzyme is primarily intended for mixes with a high proportion of barley and oats. The xylanase enzyme is added to mixes with a significant proportion of rye, wheat or triticale. Today, the feed industry has many such solutions.

Wet feeding/dry feeding
In recent years, wet feeding has become increasingly widespread. Study results indicate that wet feeding can improve production rates. The decision to use liquid or wet feed is individual and depends on the management and technology of the farm. This decision is also influenced by water consumption and indirectly by the amount of manure produced, which must be managed. The dry feeding system allows for complete mechanisation and therefore will also reduce labour as well as investment costs. It also allows for greater hygiene. In a wet feeding system, slightly better feed utilisation is often achieved. Fattening pigs have thinner fat, higher meat content and higher body weight gains. The mix obtains a liquid consistency by mixing solid dry feed with a liquid substance (water or a by-product, e.g. whey) at a ratio of 1:2 or 1:3. Adding the liquid component should be done immediately before feeding, and mixing must be thorough, otherwise, the ingredients may delaminate. One of the advantages of using a wet feeding system is the use of liquid by-products of dairy (whey, rinsing from yoghurt and ice cream production), starch, brewing (yeast suspension), and food industries. In this case, while balancing feed rations a liquid component liquid component should be taken into account.

17.6.3.3 Use of feed additives in pig nutrition

Feed additives are substances introduced into the feed outside the usual balancing. They can modify assimilation processes or affect the body in multiple ways. The introduction of a ban on the use of antibiotic growth promoters in European Union countries in 2006 has increased interest in natural products of plant origin in terms of their use in animal nutrition as phytobiotic additives. In recent years, several feed additives have been developed to prevent pathogenic bacteria from colonising the digestive tract. Antibiotics can be largely replaced by using the following substances in animal nutrition: probiotics, prebiotics, synbiotics, acidifiers (organic and inorganic acids, salts of these acids), dried herbs and plant extracts – phytobiotics, mineral compounds and chelates of some bioelements.

Characteristics of the impacts of probiotics on animals

Rare impact:	Frequently occurring:	Commonly occurring:
– modulation of the immune response – production of specific biologically active substances – neurogenic and endocrine effects – other	– vitamin synthesis – direct antagonism – increase in enzymatic activity and neutralisation of carcinogens – bile acid metabolism – stabilisation of the intestinal barrier	– protection against colonisation – normalisation of the microbiota – competition with pathogenic microorganisms – production of short-chain fatty acids – effect on intestinal transit

Phytobiotics
Phytobiotics are preparations of plant origin derived mainly from herbs, which contain biologically active substances that are secondary metabolites. They are the basis of traditional medicine as well as can be an attractive feed additive for livestock. Phytobiotic additives to animal feed are well-known in organic farming, but the growing interest is mainly due to their potential for replacing antibiotics. Added to the ration, they can positively affect animal health (preventive effect), feed intake, increase productivity and improve the quality of animal products, giving them functional characteristics. However, the content of active compounds can vary depending on the plant parts used (seeds, leaves, etc.), the geographic origin and harvest season of the plants, and storage or extraction methods. The effects can also be variable depending on the synergistic effect of individual bioactive compounds, as well as the form of application. Among this group of compounds, essential oils are of great interest. According to scientific data, the most active phytoncides used in animals are thymol, carvacrol and phenylpropanoid eugenol, cinnamaldehyde and others.

A very important stage in pig breeding is the weaning period for piglets. Health problems arising at this time significantly affect the economics of production. During weaning, there is an increased susceptibility to disease, which is associated with some physiological, immunological and microbiological changes in the gastrointestinal tract. In addition, piglets that have difficulty adapting to solid feed in the first week after weaning and those that are housed in poor environmental conditions have a low growth rate. As a rule, the body weight of such animals is lower at a later age and the age on the day of slaughter is higher compared to individuals with an undisturbed growth pattern. Factors limiting the growth rate of weaned piglets include:

• deprivation of the beneficial components contained in the sow’s milk,
• insufficient water and feed intake,
• insufficient production of gastric acids and digestive enzymes,
• reduced ability to absorb nutrients in the small intestine.

During the weaning period, there are changes in the bacterial flora, as the number of coliforms and enterococci bacteria increases and the number of desirable lactobacilli decreases. Changes in intestinal flora are responsible for an increase in the amount of water excreted in faeces, which is particularly observed between 3 and 10 days after weaning. The most common cause of diarrhoea occurring in weaned piglets is enterotoxigenic strains of Escherichia coli. Supporting the process of building a normal microbial flora of the digestive tract after weaning piglets is particularly important. The inclusion of probiotic and prebiotic formulas in the feeding of piglets can help optimise digestion and populate the digestive tract with beneficial bacterial microflora, potentially reducing the susceptibility of piglets to gastrointestinal infections. Also, the research done so far confirms that plant extracts can have a desirable effect on production results in piglet rearing, through beneficial effects on the structure of the epithelium of the small intestinal mucosa. The use of feed additives that allow early enough colonisation of the gastrointestinal tract not only creates the opportunity to improve the health of the intestines but also contributes to piglet immunity. Phytobiotic preparations with antioxidant properties improve the health of animals by stimulating the antioxidant status of the body. The benefits resulting from the administration of phytobiotic preparations, registered in the form of higher daily gains and improvements in feed intake and utilisation, allow for an increase in the efficiency of piglet rearing or fattening.

The efficiency of using various forms of herbs in feeding different animal species

– low efficiency (0-2% improvement)
++ – desired efficiency (2.1-5%)
+++ – high efficiency (above 5%)
0 – no efficiency or information

Selected biologically active compounds contained in plants

Compounds	Biological function
Polyphenols	They are characterised by potent antioxidant activity (evidenced by the presence of a large number of hydroxyl groups), inhibition of lipid peroxidation, and anticoagulant, antifungal and antiviral activity. The mechanism of action is most often indirect, through products of secondary metabolism.
Terpenoids	They have anti-inflammatory and antiseptic activity, relax smooth muscles and lower blood pressure. In addition, they have bactericidal and fungicidal properties.
Saponins	They have immunomodulatory effects, stimulate kidney function, and regulate the metabolism of cholesterol and triglycerides. They often exhibit vasoprotective properties.
Alkaloids	They mainly affect the nervous system, acting as a stimulant for the body. They have a relatively strong effect. They also show bacteriostatic effects.
Non-starch polysaccharides	They can retain water, modify the absorption of nutrients, and bind toxins and bile acids.

17.6.3.4 Detailed principles of sustainable feeding of pigs by age group and production direction

Piglets
Good growth and development of piglets have a key impact on the performance of animals later in life. Intensification of breeding and, above all, breeding work to improve the fertility of sows has increased the number of live-born piglets. The higher number of piglets in a litter resulted in a reduction in their body weight. In practice, it is sometimes possible to observe large variations in weight within a litter. Therefore, it is important to properly feed piglets from the first days of life. Milk replacers recommended for feeding suckling piglets from the first day of life are available in the feedstuff market. They can either replace or supplement sow’s milk. Such a product is an excellent source of energy and protein and has a high lactose content. It contains fatty acids and other biologically active compounds which ensures effective inhibition of pathogenic bacteria in the digestive tract and allows weaker piglets to regain weight, thus preventing cachexia and litter differentiation.

During the period of rearing piglets with their mothers, it is advisable to provide them with special feed of the highest quality and digestibility. Failure to feed piglets always leads to problems after weaning. Depending on the size of production on the farm, industrial “super baby” feed are used, or simply roasted barley on small farms. Such feeding with solid feedstuffs should be started around the 5th-7th day of life, always fresh, several times a day, so that they do not lose their value and attractiveness of taste and smell. The intake of even small amounts ensures that the digestive system is well prepared for the digestion of solid feed and eliminates possible digestive disorders after weaning. High-quality prestarters additionally contain flavouring compounds, the right amount of vitamins, sodium butyrate and probiotic bacteria that effectively compete with pathogenic bacteria such as E. coli. The introduction of the prestarter should be gradual. Veterinary treatments (administration of iron, castration of young boars, proper vaccinations, etc.) must not be omitted. In piggeries where the occurrence of diarrhoea or the so-called oedema disease is a significant problem, we recommend additional acidification of the feed (or water) used in the weaning period.

Piglets
Piglets at about 28 days of age with a body weight of 7-10 kg are basically ready to live independently without their mothers, but this is the point at which many mistakes are unfortunately made. When weaning piglets from their mothers, another selection should be made so that in the dry and warm rearing room they are divided by weight, condition and possibly health status. Litter mixing should also be minimised (as much as possible). Piglets need to adjust to their new environment and establish a hierarchy in the new group. At this period, the piglets’ digestive and immune systems are not yet fully developed and there is a high risk of gastrointestinal diseases. A measure to prevent emerging diarrhoea is to frequently feed only small portions of easily digestible nutrients. In addition, piglets should get used to the new feed as soon as possible, but this period of habituation should be gradual minimising the reduction in daily gains. This moment of rearing is also not “time to save money.” The feed provided must be of the best quality. High-energy feeding during this period makes piglets more vigorous from the first days after weaning. Protein with high digestibility determines proper weight gain, and macro- and micronutrients and vitamins will ensure proper development.

The change from prestarter to starter feed should be carried out gradually, as such a system allows the digestive tract to optimally adapt to digesting the new mix. Starter feed are prepared based on very good quality components, with increased digestibility, a high proportion of readily available energy and top quality cereals, often extruded. This ensures far better feed utilisation. Special attention should be paid at this time to the origin of the protein. The undigested part of the protein lingering in the digestive tract is the beginning of many health problems. The occurrence of stress may be related to fluctuations in feed intake, which in turn can cause feeding disorders. Feed rations for piglets from 10-30 kg body weight are about 13 MJ EM and 17.5-18% total protein.

Feeding of fattening pigs
Fattening efficiency depends mainly on the amount of daily weight gain and feed consumption per 1kg of gain. Looking slightly differently, it can be assumed that the period of weight gain from 30 to 100 kg cannot exceed 4 months, with low feed consumption per 1 kg of gain. This requires the use of well-balanced feed, which are currently available in a wide offer of feed companies. Therefore, breeders can use ready-made complete mixes or buy cereals, concentrates and premixes and carefully prepare mixes based on them. Achieving high animal weight gains with adequate meatiness requires ensuring adequate levels of energy and nutrients in the mix. Thus, the feed should fully meet the nutritional needs of pigs at a low price.

Intensive fattening is characterised by large daily gains (>700 g). Extensive fattening, on the other hand, can be carried out on farms that use farm feed (cereals, steamed potatoes, by-products of the food industry, green fodder and others) and, of course, complementary mixes. The intensive feeding scheme should include 3 periods: starter, grower and finisher. In each of the above-mentioned periods, we must provide adequate levels of energy (13-13.5 MJ), protein (16-18%), essential amino acids (lysine, methionine, threonine, tryptophan), minerals (Ca, P, Na) and vitamins in the rations for fattening pigs. However, it is important to remember that a fattening pig’s nutrient requirements depend on its body weight, growth rate and type of fattening. Assuming an energy content of 12.5 MJ in feed, daily intake should be as follows for each month of fattening: 1st month – 2 kg, 2nd month – 2.4 kg, 3rd month – 2.8 kg, 4th month – 3.0 kg. It should be remembered that the younger the fattening pigs are, the higher the concentration of energy in the ration should be. For example, young fattening pigs fed prestarter feed require about 13.5 MJ of metabolic energy per kg of feed dry matter. The increase in energy concentration in mixes has a positive effect on animal growth, the amount of daily gains and improved feed utilisation. The rational selection of essential amino acids such as lysine, methionine, tryptophan, threonine, valine and isoleucine, allows for better balancing of the amino acid composition, in addition to reducing protein loss in the form of nitrogen, which contributes to environmental pollution. Too low a level of lysine in the rations limits the intake of the rest but importantly reduces the formation of muscle tissue. When composing feed for pigs, it is worth paying attention to the crude fibre content. Its optimal level stimulates the motility of the digestive tract and causes a feeling of satiety. If it is too high in the ration, it worsens the digestibility of feed nutrients and reduces its energy content. A very important element is also the animals’ access to fresh water, the need for which can vary depending on the season.

Feeding of sows
Breeding progress has led to the fact that today sows have a high number of piglets born per litter, high milk yields and maternal instinct, which allows them to wean balanced piglets weighing more than 7 kg. The perfect feed for sows should have caloric content adjusted to their physiological cycle. An improperly balanced ration in terms of energy and protein and a lack of essential nutritional elements, vitamins and minerals translates into poorer reproduction and overall health. A sow goes through various physiological periods in her production cycle (oestrus, gestation, periparturient period, lactation, weaning of piglets). In each of them, nutrient requirements are different, so the specifics of feeding sows in each physiological state vary. Poor-quality feed, nutritional deficiencies, the presence of mycotoxins, or anti-nutritional factors in feeds take a toll on production performance. Such mistakes result in sows having small litters, low milk yields, and piglets with low body weights. These errors also affect reproduction (e.g., sows take longer to barren) and the frequency of farrowing per year, or a decline in milk production. Then the profitability of production decreases. Sows are divided into the following production groups, which have distinct nutritional requirements:

• sows during the barren period (from weaning to mating),
• low-gestation sows (from mating to day 30, with confirmed gestation),
• low-gestation sows (from the day 31 of gestation to the day 90 of gestation),
• high-gestation sows (from the day 91 of gestation to farrowing),
• lactating sows (from farrowing to weaning of piglets).

In the period after weaning the piglets, the sow should return to proper condition and undertake reproductive functions – its energy requirements are generally high. Recommendations during this period are quite precise and take into account the flushing mix, such as feeding sows with feed for lactating sows (3.5-4 kg) and flushing mix (0.3-0.5 kg/unit/day) or feeding sows with feed for gestating sows (4-5 kg) + flushing mix (0.3-0.5 kg/unit/day). Only a flushing-type complete mix of about 3.0-3.5 kg and be used successfully.  Proper feeding during this period will translate into the number of piglets per litter.

During a low gestation, proper implantation of fertilised ova in the uterus is important. During this period, the most important cause of failure is the stress of group maintenance and nutritional errors. After mating, sows should be given feed high in crude fibre to keep them feeling satiated. Straw provides sows not only with welfare but also with a source of fibre. Council Directive 2008/120/EC of 18 December 2008, laying down minimum standards for the protection of pigs, indicates that all gestating sows and young sows should be given a sufficient amount of large-chunk or high-fibre food, as well as high-energy food to satisfy their hunger and need to chew. During this period, it is recommended that sows receive about 2.5 kg of low-gestation sow mix daily, given twice a day. Large sows and those in poor condition should receive appropriately more feed (> 4kg per day). However, intensive feeding is generally used for high-gestation sows (>91 days of gestation). Thus, during the period of high gestation, sows should be fed more intensively than during the period of low gestation, but the amount of nutrient intake by the sow must still be normalised. This will ensure proper growth of the fetuses, as well as allow for the accumulation of a certain pool of spare ingredients to be used by the sow during lactation. It is not only the quantity of protein that is important, but especially the quality. This is related to the content of limiting amino acids in the feed (mainly lysine, methionine, threonine and tryptophan) and their digestibility. A small addition of high-fibre feed (good quality hay, wheat bran, oat middlings, dried pulp) is advisable to satisfy the appetite and sense of satiety. A hungry sow during this period is nervous, which does not improve production results. Stress negatively affects the health and productivity of the sow, as well as the quality of the piglets born. By using nutrition enriched with higher-fibre feed, we are using preventive health measures to prevent the development of MMA syndrome.

Almost half of the weight gain of piglets at birth occurs in the last 3-4 weeks of gestation. Fetal growth during the first half of the transition period (10 days to parturition) accounts for 25-30% of the postnatal weight. This is due to the sow’s increased need for protein and amino acids. If nutrient intake during these days is insufficient fat and protein reserves will be mobilised for the growth of fetal and reproductive tissue. The fastest growth of lactating tissue occurs ten days before parturition and continues for ten days after farrowing, but proceeds at a slower pace. Nutrition during this period plays a key role in the development of the mammary gland. After parturition, the sow loses nutrients retained in the expelled placenta, fluids and membranes, resulting in a negative balance. Conversely, when there is a regression of the uterine horns, the nutrients provided by this pass into the blood and are used to produce milk. It is not known exactly how feeding sows during this period affects the regression of uterine tissue.

The feed given to sows that are after the 105th day of gestation must therefore have a higher concentration of protein, amino acids and minerals. In addition, the average daily energy intake of sows is expected to be lower, except for primiparous ones. On the other hand, young sows in their first gestation should be fed a feed with slightly higher protein levels, compared to multiparous sows. From day 111 to farrowing, it is necessary to prepare the sow for parturition, which is expressed in a significant reduction in the amount of feed given. Above day 110, the so-called perinatal period begins. Care should then be taken to provide high-value feed, with the observation, however, that on the day of parturition itself, mild starvation is preferable. Disruption of water-electrolyte balance has very adverse consequences, both for the sow and the piglets. An adequate supply of water is important here. During each gestation period, complete feed should be used, adequate for that period with the appropriate content of minerals and vitamins and other ingredients (such as L-carnitine) necessary for fetal development.

Feeding during lactation should ensure high milk yield in the sow and prevent excessive decline in condition. The daily feed intake of lactating sows is about 5-7 kg and depends on many factors: the condition of the sow, litter size, room temperature, feed palatability, nutrient content and crude fibre. It is generally accepted that the requirement is 1% of the sow’s body weight +0.5 kg for each piglet. Sows should have continuous access to feed. The result of correct feeding of a lactating sow is not only her health but also the condition of the litter (equalised piglet weight, absence of diarrhoea).

Heat stress significantly affects feed intake. It is estimated that an increase in ambient temperature from 25 to 27°C with a relative humidity of 50 to 60% results in a 250g/day decrease in feed intake. The negative effect of increased ambient temperature can be amplified by increased relative humidity. So ventilation and cooling are crucial here to maintain productivity. All-day access to feed is important, although between 44-64% of feed during the hot season is taken by sows at night.