What are the nutritional characteristics of protein feeds for pigs
Protein feed generally refers to feed whose dry matter contains more than 20% crude protein and less than 18% crude fiber. It includes both plant-based and animal-based protein feeds. Plant-based protein feeds are mainly various oilseeds and the cakes and meals left after oil extraction, while animal-based protein feeds mainly include fish meal, meat-and-bone meal, silkworm pupa meal, blood meal, feather meal, and so on.
(1) Plant-based protein feeds
1. Legumes: Legume feeds are high in protein and can be called protein feeds. This type of feed includes soybean, black soybean, broad bean, and pea; compared with cakes and meals, they contain less protein. Soybean is relatively expensive and is also a raw material for soy products, so it is not suitable to feed soybean to pigs. Suckling piglets can be appropriately fed some cooked soybean or roasted soybean powder, but not in excess. Never feed pigs raw soybean or raw cake, because they contain trypsin inhibitor with strong activity, which can cause diarrhea and hinder growth.
Black soybean is often used as pig feed, but feeding it to pigs is not economical. Broad bean and pea are also not commonly used because their sources as feed are limited. If some areas have abundant production, they can account for 5%-7% of the pig diet, and the feeding effect is relatively good.
2. Soybean cake (meal): If soybean is first pressed for oil as pig feed, its cake is used to feed pigs. Soybean cake is a by-product of soybean oil extraction. The by-product of processing soybean by pressing is called soybean cake, and the by-product of processing soybean by solvent extraction is called soybean meal. Soybean cake (meal) is the best protein feed for raising pigs. Its protein content is 40.9%, and soybean meal is 43%. It is also rich in lysine. When used to raise lean-meat pigs, it has a great effect on lean meat growth. Soybean cake (meal) can account for 12%-20% of pig feed, with a maximum not exceeding 25%; feeding too much causes diarrhea.
3. Peanut kernel cake: Good palatability, rich nutrition, and easy to digest. Its feeding value is second only to soybean cake (meal). The crude protein content is 44.7%, and peanut kernel meal is 47.8%, but it lacks lysine, tryptophan, methionine, and threonine. Peanut cake does not store well and is easily infected by Aspergillus flavus, harming pig health. During storage, special attention must be paid to ventilation and dryness, and mold must be strictly avoided.
4. Rapeseed cake: Contains 36%-38% crude protein, is rich in methionine, and has relatively low lysine content. It contains glucosinolates, which under the action of myrosinase are hydrolyzed into toxic substances such as isothiocyanates and oxazolidinethiones. These are disease-causing substances for the pig thyroid, hinder pig growth and weight gain, and in severe cases cause poisoning and death. Therefore, the feeding amount must be strictly controlled, generally accounting for 3%-5% of the diet. In recent years, Zhejiang Agricultural University developed a rapeseed cake detoxification agent, the 6107 additive, allowing its dosage to reach 20%.
5. Cottonseed cake (meal): Cottonseed cake contains 40.5% crude protein, and cottonseed meal is 42.5%, but it contains free gossypol, which in excess causes poisoning and even death. It has an especially adverse effect on the reproductive capacity of boars and sows, so it is not used in their diets. The proportion of cottonseed cake and meal in the diet of finishing pigs should be controlled at 10%-15%. There are three commonly used methods for detoxifying cottonseed cake:
(1) Boil for 1-2 hours, cool, and then feed.
(2) Soak in 5% limewater for 10 hours, or soak in 1%-2% ferrous sulfate solution for 24 hours.
(3) Ferment the cottonseed cake before feeding, or add 10% lime to water and boil it.
In recent years, cotton experts have developed gossypol-free cotton. Its stems, stalks, leaves, and the cakes left after pressing oil from the seeds are all good feed for raising pigs. They contain no gossypol or only a small amount, and can be tried for feeding pigs.
6. Sunflower seed cake: It can be divided into two types, dehulled and hulled. The protein of dehulled sunflower seed cake is higher than that of the hulled type, about 36.5%, while the hulled type is about 25%, and its methionine content is relatively high. The disadvantage is that its lysine content is relatively low, and the crude fiber of the hulled type is above 20%, so its feeding value is relatively low and it can only be used in small amounts.
7. Corn protein powder: The gluten remaining after removing the germ and starch has protein as high as 63.5%, and the medium grade is also 44%-51%. However, its important component is gliadin, and its lysine and tryptophan contents are relatively low, so it must be combined with cakes and meals to meet the protein needs of growing, breeding, and finishing pigs.
8. Distiller's and residue types: These are industrial processing by-products, mainly including brewer's grains, distiller's grains, sauce residue, and okara. After the above residues are dried, their protein content is above 20%, so they can also be classified as protein feed, but the feeding amount should be strictly controlled. Okara has a relatively high protein content and is a nutritious, easily digestible feed, most suitable for feeding young pigs, but it must be cooked or steamed before feeding, because it contains trypsin inhibitor and therefore is not easy to digest.
(2) Animal-based protein feeds
1. Fish meal: It is the best protein feed. Its protein content is as high as 62%-65%, its essential amino acids are complete, its vitamin content is rich, and its mineral content is also relatively complete, with an appropriate calcium-to-phosphorus ratio. Using fish meal in pig diets can significantly improve production performance, and the average daily gain of pigs can be increased by 15%-25%. However, fish meal is expensive, and there is a lot of fake Peruvian fish meal, so at present many pig farms use soybean cake and meal to replace Peruvian fish meal in the diet.
2. Meat meal and meat-and-bone meal: These are powdered products made from meat or meat-processing by-products that have passed sanitary inspection and are not suitable for human consumption, after high-temperature and high-pressure or boiling treatment, and after degreasing, dehydration, and drying. Usually, that containing less than 10% is called meat meal, while that containing more than 10% is called meat-and-bone meal.
The crude protein content of meat meal is 50%-60%, while meat-and-bone meal varies in protein content depending on the ratio of meat to bone, generally 40%-50%. It is best used in combination with plant-based protein feeds, at 3%-10% of the diet.
3. Blood meal: It is the blood obtained when slaughtering livestock, made into powder by spray drying. It contains 82.8% crude protein and is a high-protein feed containing a variety of essential amino acids. Blood meal has poor palatability, and its protein digestibility is low. In pig rations, it is generally appropriate not to exceed 5%.
4. Silkworm pupae and silkworm pupa meal: These are by-products of the silk reeling industry, rich in fat, not easy to store, and they affect the quality of meat and fat. Therefore, it is advisable to extract the fat first and then make silkworm pupa meal for feed, which stores well and can also improve utilization. Its protein content is nearly 80%, rich in various amino acids, and used in combination with cakes and meals it can increase average daily gain.
5. Yeast: It is another protein feed between animal and plant proteins, and its protein content is also between the two, about 52.4%. Yeast has a bitter taste and relatively poor palatability. Control the feeding amount so as to avoid anorexia in pigs and affect weight gain and growth. The dosage is 2%-3%, and it is appropriate not to exceed 5%.
6. Feather meal: After hydrolysis, its crude protein is 77.9%, higher than fish meal, making it a good protein feed. Feather meal contains much keratin protein and must be hydrolyzed before it can be fed to pigs, but the cost of hydrolysis is high, so small amounts are still acceptable.