According to the EU regulation, the feeding of food waste to pigs has no longer been permitted since 1 November 2006. Disposal is now mainly via biogas plants. This political, from a technical point of view nonsensical regulation presents numerous pig farmers with serious problems. Heated food leftovers from canteen kitchens were a popular, high-quality, low-priced, hygienically problem-free pig feed. By using them, feed cost advantages could be realized and good fattening performance could be achieved. The usual food residues usually contained high amounts of protein and energy as well as other valuable ingredients and were usually mixed with other by-products. Due to the entry in the positive list, food residues could even be used in QA plants.
Especially at this time, when the prices for cereals and protein feed are enormously high, the feed ban naturally weighs particularly heavily. In addition, it will hardly be possible to simply close the resulting feed gap with other by-products. Because the by-products produced in the food industry and suitable for pig feeding are only available on the market to a limited extent. The ban on food waste feeding on the one hand and the rise in prices for cereals and soya bean meal on the other hand will certainly bring a lot of movement to the market for by-products. Those farmers who have long-term purchase agreements will, of course, have an advantage.
Irrespective of this market development, the fundamental question arises as to what possibilities exist to compensate for the loss of food waste with other by-products. Table 1 lists some components from the food industry that are of greater importance for pig fattening and have proven themselves in feeding practice.
Old bread and baking residues are highly digestible products with energy values between 13.8 and 16.6 MJ ME per kg (based on 88% dry matter). As a rule, baking residues contain a lot of fat and sugar, which also make them particularly tasty. Both by-products contain very little crude fibre, which must be taken into account when designing the ration. The total ration should contain no less than 30 to 35 g of crude fibre per kg of fattening feed (88 % DM), and the quantities used should be estimated accordingly. Both components are very rich in sodium, on the other hand low in calcium and phosphorus. Special attention must therefore be paid to the correct choice of appropriate mineral feed.
Bread and baking residues contain only small amounts of amino acids and little is known about their digestibility in pigs. It should be pointed out that there are sufficient supplies via special supplementary feeds or soy meal. Experience has shown that 15 to 35 % old bread or 10 to 25 % baking residues in the fattening mixture should not be exceeded.
Potato steam peels have always been a popular by-product from the production of chips or other potatoes. The peeling of the potatoes takes place under hot steam pressure. This considerably improves the digestibility of the starch still adhering to the peel. Nevertheless, the energy content is only 11 MJ ME/kg (at 88 % DM), so that energy-rich components have to be added when this product is fed. Food waste offered good combination possibilities here. In order not to allow the energy concentration in the fattening feed to drop too far, no more than 20 % potato steam peels should be used.
Fresh whey and whey in concentrate form are widely used by-products of cheese and curd production. A distinction is made between sweet whey and sour whey. Sweet whey is usually mixed with organic acids to make it more durable. Fresh whey contains almost 95% water and is therefore hardly worth transporting over long distances. The situation is different with whey concentrates, which contain between 24 and 33 % DM. Both products contain far more than 50% milk sugar (lactose) based on 88% DM. Since a fattening mixture should not contain more than 10 % total sugar in order not to risk digestion problems with the fattening animals, the whey use is limited to 10 to 20 %. Similar to food leftovers, whey contains a lot of sodium.
Recently, large quantities of rapeseed cake have been produced from decentralised smaller oil presses stationed on farms or with contractors. Depending on the degree of pressing, the rapeseed cake left over from oil extraction may contain much or little residual oil (fat), which determines the energy value. The fat contents from farms measured by the North Rhine-Westphalia Chamber of Agriculture ranged between 14 and 22%. This resulted in energy contents of 13.1 to 15.2 MJ ME/kg, on average 14.0 MJ ME/kg, almost comparable to the food leftovers. Rapeseed cake also contains significantly more protein than food leftovers. However, the amino acids of the rapeseed cake are not particularly well utilised by pigs, as is the case with food leftovers, so that the protein supply to the animals during rapeseed cake feeding must not be calculated too tightly. Practical experience has shown that up to 5% should be used for initial fattening and a maximum of 8% to 10% for final fattening.
In the past, food waste was usually fed in a mixture with other by-products. In Westphalia there is a larger marketer who has now designed a new energy mix instead of the leftover food mixture which consists of wheat protein (thickened stillage), whey concentrate, a maize by-product (from starch production) and rapeseed cake. This feed pulp with 31.6 % DM contains the following ingredients: 15.6 % crude protein, 0.52 % lysine, 2.3 % crude fibre, 11.1 % crude fat, 42.5 % sugar, 4.6 % starch and 9.7 % crude ash (each based on 88 % DM). The energy content is about 15 MJ ME/kg (at 88% DM). This sugar-rich product with a pH value of 4.2 is delivered at 40 to 50 degrees Celsius and has a shelf life of about 2 to 3 weeks. Mixture proportions of 20 to 30 % are recommended for soy grain generations.
In the following, mast blends with by-products, which may continue to be fed, are presented. In order to have a better comparison, Table 2 is preceded by mixtures with, meanwhile forbidden, food residues and normal grain-soy mixtures. From the ingredients of the mixtures it becomes clear that a safety surcharge for lysine is necessary for by-products due to fluctuating ingredients. In order to have control over the fluctuating ingredients, it is advisable to regularly check the TS content of all liquid by-products. In the case of protein feeds, the crude protein and lysine content must be checked; in the case of by-products rich in fat, starch or sugar, the energy content should be checked. The supplement or the mineral feed must be precisely adapted to the particularities of the by-products used, especially with regard to the supply of essential amino acids (e.g. lysine) or minerals (e.g. sodium).
Due in particular to the high fat content, rations with food leftovers are characterised by a high energy content, which is 0.3 – 0.5 MJ ME/kg higher depending on the proportion of food leftovers in the ration. If one compares the energy content of the by-products in Table 1 with the energy content of wheat (14.4 MJ ME/kg), it becomes clear that only baking residues and the by-product mixture enhance the energy content of the fattening mixtures due to the high sugar content. In order to avoid diarrhoea in particular, sugar-rich by-products must not be fed in excessive proportions. The guideline value is 10 – 11 % sugar in the total mixture.