Animal protein sources

Spray-dried blood products are by-products obtained from swine and bovine harvesting plants. The whole blood is collected in chilling tanks and prevented from coagulating by adding an anticoagulant. Spray-dried blood cells and spray-dried plasma are produced by separating the blood fractions, whereas spray-dried blood meal contains both blood cells and plasma (Almeida et al., 2013).

Spray-dried blood products contain high concentration of crude protein (75 to 90%) and lysine (7 to 8%) (NRC, 2012). Standardized ileal digestibility of lysine and most amino acids is high, above 95 to 95% (Almeida et al., 2013). However, lysine availability is reduced with use of excessive heating in spray-dried blood products.

The use of spray-dried blood products requires attention to an favorable balance of branched-chain amino acids due to the high concentration of leucine but low concentration of isoleucine and valine, particularly in spray-dried blood cells or blood meal (Kerr et al., 2004; Goodband et al., 2014). Also, the concentration of methionine is low in all spray-dried blood products. The inclusion of other protein sources or supplementation of diets with feed-grade amino acids is important to adjust the amino acid profile in diets with spray-dried blood products (Remus et al., 2013).

Spray-dried blood products may vary substantially in composition and quality according to source and processing methods. The application of heat is critical to eliminate pathogens (Narayanappa et al., 2015), but post-processing recontamination can be a concern. In order to minimize the risk of disease transmission via feed ingredients, it is advisable to only use non-porcine-derived blood products.

Meat and bone meal is a by-product from various tissues obtained from harvesting plants. Meat and bone meal contains high concentrations of crude protein (50 to 55%), lysine (2.5%), and most amino acids except for tryptophan (NRC, 2012). Standardized ileal digestibility of lysine and most amino acids is low, approximately 65 to 80% (Kong et al., 2014).Moreover, lysine availability is further reduced with use of excessive heating during processing of meat and blood meal.

Meat and bone meal is an excellent source of calcium and phosphorus, providing the minerals in high concentration and with a high phosphorus bioavailability (Traylor et al., 2005).

Meat and bone meal quality and composition may vary substantially according to the raw materials characteristics. The thermal processing of meat and bone meal is critical to eliminate pathogens, but post-processing recontamination can be a concern.In order to minimize the risk of disease transmission via feed ingredients, it is advisable to only use non-porcine-derived meat and bone meal.

Poultry meal is a by-product from viscera and various tissues obtained from poultry harvest. Poultry meal contains high concentration of crude protein (60 to 65%), lysine (4%), and most amino acids except for tryptophan (NRC, 2012). The digestibility of amino acids can be affected by the ash content of poultry meal. The ash content is directly related to the level of bone included in poultry meal and is a measure associated with low digestibility and inferior quality (Keegan et al., 2004).Moreover, lysine availability is further reduced with use of excessive heating during processing of poultry meal.

Poultry meal quality and composition may vary substantially according to the raw materials characteristics. The thermal processing of poultry meal is critical to eliminate pathogens, but post-processing recontamination can be a concern.

Fish meal is a product obtained by processing whole fish or fish waste. Fish meal typically contains high concentration of crude protein (60 to 65%) and lysine (4.5%), favorable amino acid profile, and omega-3 fatty acids (NRC, 2012). Standardized ileal digestibility of lysine and most amino acids is high, approximately 85% (Cervantes-Pahm and Stein, 2010).

The inclusion of fish meal in swine diets enhances palatability and usually increases feed intake. However, fish meal quality can vary considerably depending on the species of fish, raw fish freshness, and processing method (Kim and Easter, 2001; Jones et al., 2018). Fish solubles, also known as stickwater concentrate, is a by-product rich in B vitamins and minerals derived from fish meal processing. The amount of fish solubles is variable in fish meal, generally found at 8 to 15%, but it is not associated with fish meal quality (Jones et al., 2018).

Currently, there is no single laboratory test that provides a general estimate of fish meal quality. Analysis of mineral content and fat can be used as an indicative of fish meal feeding value. Fish meal with high mineral content (> 20%) and lower fat level (< 7.5%) is generally from fish offal and contains lower feeding value compared to fish meal from whole fish. Freshness of raw fish can be estimated by analysis of total volatile nitrogen. Values below 0.15% total volatile nitrogen generally indicate good fish meal freshness. Bacterial analysis is important to assess quality of fish meal, as Salmonellacan be transmitted via fish meal (Morris et al., 1970).

Porcine intestinal mucosa products are by-products of the pharmaceutical industry obtained from processing of porcine intestinal mucosa to extract the anticoagulant heparin. The mucosa linings are enzymatically hydrolyzed after extraction of heparin and co-dried with plant proteins to produce porcine intestinal mucosa products. Commercially available products are generally referred to as enzymatically-hydrolyzed intestinal mucosa, dried porcine solubles, or peptones.

Porcine intestinal mucosa products provide small peptides that are easily digestible by pigs. The concentration of crude protein is high (50 to 60%) and amino acid profile is favorable (Myers et al., 2014). Standardized ileal digestibility of lysine and most amino acids is high, above 80 to 85% (Sulabo et al., 2013).

Variation in composition of porcine intestinal mucosa products is due to different plant proteins used as carriers during drying and processing of intestinal mucosa (Jones et al., 2010; Myers et al., 2014). The thermal processing of porcine intestinal mucosa products is critical to eliminate pathogens, but post-processing recontamination can be a concern.

Spray-dried egg is a by-product from the egg industry produced only from eggs without shell that do not meet the quality standards for human consumption. Spray-dried egg contains high concentration of crude protein (50%), lysine (3.5%), and favorable amino acid profile (NRC, 2012). Spray-dried egg is also a good source of energy.

Spray-dried egg provides bioactive compounds, such as antimicrobial proteins (lysozyme) and immunoglobulins (IgY). The composition of spray-dried egg is thought to provide benefits to improve health (Song et al., 2012). Moreover, hens can be immunized against pathogens, such as enterotoxigenic Escherichia coli, and the hyperimmunized eggs serve as a pathogen-specific antibody source (Da Rosa et al., 2014).

Whey is derived from milk curdling during production of milk products like cheese and yoghurt (Grinstead et al., 2000). The whey is separated from the curd and processed into whey products, including dried whey, whey protein concentrate, and whey permeate. Whey products are sources of both protein and lactose.

Dried whey is produced by removing most of the water from liquid whey. The drying process can be accomplished by spray drying or roller drying. Spray-drying is the preferred method to prevent over-heating of whey because of the fast evaporation at lower temperatures compared to roller-drying method (Grinstead et al., 2000). Dried whey contains 11 to 12% crude protein and high lactose concentration, approximately 72% (NRC, 2012).

Whey protein concentrate is produced by having an additional process of ultrafiltration of liquid whey before the drying process (Grinstead et al., 2000). The ultrafiltration process concentrates the whey protein and removes most of the lactose. Whey protein concentrate contains 75 to 80% crude protein and low lactose concentration, generally around 5% (NRC, 2012). Whey protein concentrate is an edible-grade product in high demand by the food industry, limiting its availability for use in swine diets.

Whey permeate is a by-product from the ultrafiltration process of liquid whey to produce whey protein concentrate. Whey permeate contains most of the lactose that is removed from the ultrafiltration process. Whey permeate contains low crude protein (3.5%) and high lactose concentration, approximately 80% (NRC, 2012).