Blood Meal
Blood meal is very high in crude protein, and while it is an excellent source of lysine, it is very deficient in isoleucine and this imbalance needs correcting if any substantial quantity is used in a diet. Blood meal is essentially the solids of the blood from processing plants, and consists mainly of hemoglobin, cell membranes, cellular electrolytes and a small quantity of lipid.
Historically, the level of blood meal used in diets has been severely limited, mainly because of problems of palatability, poor growth rate and abnormal feathering. All these problems relate to inherent amino acid balance and also to low digestibility induced by overheating of the blood during processing. With less harsh drying treatments, the amino acids are more stable, and there are few problems with palatability. If blood meal is overheated, it has a much darker color, tending to be black rather than reddish-brown. The amino acid balance of blood meal can be 'improved' by combining it with other ingredients. For example, a 50:50 mixture of blood meal and hydrolyzed hair meal gives a product with a reasonable amino acid balance, and certainly a balance that is preferable to either product alone. Such a mixture may be used in least-cost formulation, whereas either ingredient is unlikely to be used independently because of amino acid balance.
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