Feed sources for pigs
Feed sources for pigs are wide and varied. A well balanced feed ration should contain the necessary amount of energy, protein, minerals and vitamins. Feed for pigs can be categorized into energy, protein, vitamin or mineral sources.
Cereal grains are considered to be the first class of energy feeds. For example maize is an excellent source of energy. It has a (Digestible Energy) DE content of 3525 Kcal/kg. Usually the energy value of maize is used as a standard in which other energy sources are compared. Crude Protein (CP) is 8.5%. Maize can be used up to 85% in the diet of pigs. However maize is low in lysine and tryptophan therefore cannot be used as a sole source of feed.
Wheat is high in energy and its feeding value is equal to or slightly inferior to maize. It is low in lysine and threonine. If it is to be included in pig diet it should not be too fine.
Barley has 90% feeding value of maize. It should be ground but not too fine. Has high lysine content to meet the needs of growing pigs. Only small amounts of other protein sources are required to supply sufficient lysine and threonine.
Sorghum has 95% feeding value of maize. Grower/finisher ration may contain up to 95% sorghum. Major limitation is tannin content especially the red sorghum. Tannin depresses growth rate, nutrient digestibility and utilization and palatability.
Dry cassava has practically a feeding value as maize. Inclusion of 50% cassava depresses weight gain and feed efficiency. This effect can be counteracted by addition of methionine in swine diet.
Wheat bran has 67% feeding value of maize but due to its high fiber content should be restricted to diets of growing and finishing pigs and dry sows.
Maize bran has 86% feeding value of maize. High levels in pig diet however can cause gastric ulcers.
Wheat pollard (middling) is high in energy and protein. It can be used as sole source of protein and energy to finisher diet. However the feed efficiency and dressing percentage decreases with increasing amounts of wheat pollard.
As a general guideline the cereal by-products are included in pig diet in combination with other sources of energy mainly the cereal grains.
Protein feed sources
Usually the animal protein sources are superior because they have better amino acid profile.
Fish meal is an excellent protein source. There are various types/sources of fish meal. The various sources determine the quality of the feed. Fish meal also provides adequate quantities of essential amino acids. The recommended inclusion rates of fish meal in diet are 2 – 10%. Fishmeal should not be included in diets of finisher ration because pork will be tainted and protein requirements of finisher pig are low.
Soya bean meal is of plant origin. It is one of the most important plant protein in livestock feeding. Protein amount varies depending on method of extraction. The amino acid profile is not large but will meet requirements. Soya bean meal can be used as sole protein source.
Cotton seed cake major limitation is gossypol content which is toxic. Effect of gossypol can be counteracted by adding iron sulphate. Iron precipitates gossypol but is not absorbed and also interacts with other minerals preventing their absorption. Lysine is partially available. Cotton seed cake should be limited to less than 10% of diet. Free gossypol content of diet should be less than 0.01%
Mineral and vitamin sources
The largest proportion of a ration is made of energy and protein sources. Most of these will contain some vitamins and minerals but not adequate such that it is necessary to supplement with pure sources. Among the necessary minerals is sodium chloride or common salt. Common salt is routinely added to all swine diets because almost all feedstuff are deficient in sodium and chloride. It is commonly added at a level of 0.25 to 0.5 % of diet. Excess salt can be toxic. A level of 2% for example is toxic to swine and in the absence of sufficient water 1% can be toxic. As a guideline common salt should not exceed 0.9%. Swill should not have excess salt.
Calcium – almost all feedstuff contain some calcium but contents vary widely. For example cereals have 0.02 to 0.1%. Plant protein supplements vary in calcium content usually from 0.17% to 0.66% therefore specific supplements high in calcium are almost always required in formulating swine diet. Good sources for swine diet are limestone and oyster shell. Sources which contain both calcium and phosphorous can also be used e.g. dicalcium phosphate and deflourinated phosphates.
Phosphorous is present in variable amounts in almost all feedstuff but only a fraction is available because non ruminants like pigs lack the necessary enzymes to digest them in the guts. Inorganic sources of phosphorous are therefore used.
Zinc can be lacking especially when calcium is excess. Zinc is added to pig diet predominantly as zinc oxide.
The vitamins supplied by energy and protein sources are inadequate to meet metabolic needs. Some of the vitamin most likely to be low in natural diet are niacin, B12, vitamin A and D. In practice a commercial preparation is added at the rate of 0.1 to 0.5%. Similarly trace mineralized salts are added, premixed then incorporated in diet.
Feed additives include antibiotics and growth promoting materials. They are good in terms of growth rate, feed conversion efficiency and reduced mortality. Among the antibiotics approved by FDA are tetracyclines and lincomycin normally added at sub-therapeutic levels. Other feed additives are probiotics like fungi and bacteria which promote beneficial microorganism and suppress harmful ones.