Nutritional attributes
Blood meal contains mostly protein (about 90-95% DM) and small amounts of fat (less than 1% DM) and ash (less than 5% DM), though non-industrial blood meals may include other materials and thus be richer in ash. Unlike other animal protein sources, blood meal has a poor amino acid balance. Its lysine content is relatively high (7-10% DM) which makes it an excellent supplementary protein to use with plant-derived feed ingredients that are low in lysine. However, its isoleucine content is very low (about 1% DM), so diets for monogastric animals must be formulated to contain enough isoleucine for the level of performance desired (Piepenbrink et al., 1998; Maiga et al., 1996). Pepsin digestibility has been shown to be a good test for assessing the availability of the protein fraction of blood meal (Hegedüs et al., 1989). Blood meal is rich in iron (more than 1500 mg/kg DM).

Blood meal is generally unpalatable, particularly if overcooked, so care needs to be taken to not add more than 5 to 6% blood meal to a ration, especially if high feed consumption and performance are desired. Often an adaptation period is required to get animals used to eating blood meal.

Potential constraints
For safety reasons, blood must be heated to be used in animal feeding: a minimal temperature of 100°C for 15 min is necessary in order to destroy potentials pathogens (salmonella, mycotoxins, prions) (Göhl, 1982). It is recommended to avoid feeding a species with blood meal from the same species.

In the European Union, blood meal has been banned from feeding to animals since 2000 (Council Decision 2000/766/EC), though since 2006 blood products from non-ruminants are now authorized for use in aquaculture (Médale et al., 2009).

Ruminants
Blood meal is valuable for ruminants due to its high protein content and rumen-resistant amino acids. Rumen undegradable protein is up to 78% in blood meal and increases with the heating temperature used in its processing. Blood meal contains more essential amino acids than soybean meal (Klemesrud et al., 2000; Piepenbrink et al., 1998), but it is deficient in sulphur-containing amino acids (Klemesrud et al., 2000) and isoleucine (Maiga et al., 1996). It should be supplemented with other protein sources (Maiga et al., 1996).

Cattle
In steers and in calves, 3% dietary inclusion of blood meal increased daily weight gain, dry matter intake and energy intake (Knaus et al., 1998; Tartari et al., 1989). In dairy cows, it improved milk production and milk protein yield (Schor et al., 2001).

Sheep
In sheep, blood meal can be used as a by-pass protein (Kamalak et al., 2005), which allows a reduction in the overall dietary protein content of the diet (from 16-18% to 13%) (Antongiovanni et al., 1998). The nutritional status of pregnant ewes fed at or near maintenance while consuming low-quality roughages was enhanced by supplementation with additional crude protein in the form of blood meal (Hoaglund et al., 1992).

Pigs
Blood meal is a good source of protein in pigs. Recommended dietary levels vary from 4% of DM (Cunha, 1977; Wahlstrom et al., 1977) to 6-8% of DM (Seerley, 1991 cited by Lewis et al., 2001).

Piglets
During post-weaning phase I (day 0-14), dry skimmed milk can be replaced by animal by-products, such as porcine blood meal, porcine plasma, extracted meat protein, bovine plasma protein, spray-dried blood meal or soybean protein concentrate. Spray-dried porcine plasma (SDPP) is superior to every other protein sources (Hansen et al., 1991; Tokach et al., 1991; Rantanen et al., 1994). Recommended inclusion rate is 7.5% spray-dried plasma (Bergstrom et al., 1994; Owen et al., 1994). However, spray-dried blood meal at 2.5% of the dietary DM could replace 67% of spray-dried plasma from day 7 to 14 (Kats et al., 1992b; Dritz et al., 1993).

During post-weaning phase II (day 14-28), spray-dried blood meal will be preferred to SDPP or fish by-products as it increases both animal performance (Tokach et al., 1991) and economic performance (Kats et al., 1992a; Dritz et al., 1992). Inclusion rates should be no more than 2-2.5% of DM (Kats et al., 1992a; Kats et al., 1992b).

During post-weaning phase III (day 28-42), spray-dried blood meal can be included at 2-2.5% of DM and supplemented with 0.4-0.44% methionine (Owen et al., 1993).

Growing pigs
In growing pigs, blood meal can partially replace soybean meal in maize-soybean based diets: it is then included at 3 to 4% of DM (flash dried blood meal) or at 6% (Ilori et al., 1984; Rerat et al., 1975). It can supplement cottonseed meal to counterbalance the negative effects of gossypol in pig diets (Fombad et al., 2004).

Feeding growing pigs with fermented blood meal (dried or not) in combination with molasses allows the same feed intake, growth and feed conversion efficiency as soybean meal. Utilization of N is also high (M'ncene et al., 1999; King'ori et al., 1998). A 10% fermented blood meal inclusion in pig diets is recommended (Tuitoek et al., 1992).

Poultry
Blood meal can be used successfully in poultry diets.

Broilers
For broilers, blood meal is a good protein source. It can replace 50 to 100% of fish meal (Rao et al., 2009; Seifdavati et al., 2008; Nabizadeh et al., 2005), 50% of soybean meal (Onyimonyi et al., 2007; Tyus et al., 2008), and also copra meal or groundnut meal (Donkoh et al., 2001; Donkoh et al., 1999) resulting in improved performance and greater profit. The amounts of blood meal are equivalent to 3 to 9% of the dietary DM (Tabinda Khawaja et al., 2007; Matserushka, 1996; Quarantelli et al., 1987).

Blood meal has a high tryptophan digestibility coefficient which is valuable as tryptophan is the third limiting amino acid in broilers (Ravindran et al., 2006). It is necessary to supplement blood meal with lysine and isoleucine (Elamin et al., 1990; Tyus et al., 2008) to ensure better animal performance.

Laying hens
In laying hens, blood meal is as palatable as other rendered animal products. Sun-dried blood meal given at 4.5% of the diet has a positive effect on layer performance (feed intake, live-weight gain, egg weight and yolk colour) (Donkoh et al., 2001). Blood meal improves Fe content in yolks (Revell et al., 2009). One case of cannibalism related to blood meal feeding has been reported (Atteh et al., 1993).

Fermented cattle blood gives comparable egg production to fish meal when these products are used to replace soybean meal. However, rendered animal products can cause undesirable flavour in eggs and it is not recommended that they fully replace soybean meal in layers diets (Tuitoek et al., 1994).

Turkeys
Feeding turkeys with rendered animal products does not alter performance (Boling et al., 1997).

Ducks
Combining blood meal with other supplementary proteins has been shown to increase performance in ducks (Sucheep Suksupath, 1980).

Rabbits
Rabbits fed on blood meal had the lowest feed intake, live weight gain and feed efficiency compared to other protein sources such as fish meal, shrimp meal, hatchery by-product meal or poultry by-product meal (Fanimo et al., 2002).

Fish
Blood meal is a good quality ingredient for fish and has been tested succesfully in many fish species. Spray-dried blood meal can be used as a binder in fish feeds.

In gibel carp (Carassius auratus gibelio) (Yang et al., 2004), African catfish (Clarias gariepinus) (Goda et al., 2007) and tilapia, spray-dried blood meal can replace 50 to 75% of the fish meal, and in rainbow trout (Oncorhynchus mykiss) up to 100% (Watanabe et al., 1998; Médale et al., 2009). However, it was found to lower performance in tilapia when replacing fish meal (El-Sayed, 1998). Blood meal is well digested by the humpback grouper (Cromileptes altivelis) (Laining et al., 2003) and its gross energy is well digested by the rohu (Labeo rohita) (Noreen et al., 2008). A maximum of 5% blood meal in the diet is recommended for sea bream (Sparus aurata) as sensorial alterations may occur at a 10% inclusion rate (Martinez-Llorens et al., 2008).

Other species
Silkworm (Bombyx mori)
When included in articifial diets for silkworms, blood meal effectively increased the quantity of cocoon shells though it was a less suitable source of protein than soybean meal in terms of palatability and digestibility. Poultry feed mixed with blood meal was an economically viable concentrate diet for silkworms (Matsura, 1994a; Matsura, 1994b).