The U.S. slaughter industry produces blood co-products that may be used in diets for nursery pigs because of the high concentration and quality of protein they contain. The quality of protein in blood products can differ based on the processing techniques used.  In particular, products which are heated to too high a temperature during processing can sustain heat damage to amino acids due to the Maillard reaction. Lysine is particularly susceptible to heat damage.

An experiment was performed to determine the comparative amino acid digestibility in five different blood products fed to weanling pigs. Three are spray-dried products, which are dried quickly at temperatures of up to 225˚C. Spray-dried animal blood (SDAB) is manufactured from whole blood containing an anticoagulant. Spray-dried plasma protein (SDPP) is manufactured from blood which has had the plasma separated out by centrifugation. Spray-dried blood cells (SDBC) are the red blood cells left after plasma separation. In addition to the spray-dried products, two sources of blood meal were tested – one from an avian source (avian blood meal, or ABM) and one from a porcine source (porcine blood meal, or PBM). These blood meals were dried using drum driers instead of spraydriers.

A total of seven weanling barrows were prepared with a T-canula in the distal ileum, allotted to a 7 x 7 Latin square design and fed one of seven diets. Five diets were based on a mixture of casein and one of the blood products being studied. One diet was based on casein but no blood products, and the last diet was a N-free diet that was used to determine the basal endogenous losses of amino acids.

The standardized ileal digestibility of crude protein did not differ among spray-dried animal blood, spray-dried blood cells, and spray-dried plasma protein (Table 1). The digestibility of crude protein was greater (P < 0.01) in those products than in the avian and porcine blood meals.

For most dispensable amino acids, the digestibility values were the same among SDAB, SDBC, and SDPP, and were greater (P < 0.01) than the digestibility values in ABM and PBM, which did not differ from each other. In the cases of histidine, leucine, phenylalanine, and valine, the digestibility values in ABM were less (P < 0.01) than in PBM. The mean values for standardized ileal digestibility of all amino acids were the same among SDAB, SDBC, and SDPP, and were greater (P < 0.01) than the digestibility values in ABM and PBM, which did not differ from each other.

The lysine:crude protein ratio in ABM (8.5%) and PBM (8.7%) was less than the ratios in SDAB (9.2%), SDBC (9.6%), and SDPP (9.0%). This indicates a greater degree of heat damage in ABM and PBM than in the spray dried products.

• The digestibility of crude protein and amino acids in SDAB, SDBC, and SDPP is excellent, and close to  100%.
• Due to heat damage, the crude protein and amino acids in the drum dried avian and porcine blood meal products studied in this experiment were less digestible than those in the spray-dried blood products studied.
• All of the blood products studied in this experiment are excellent sources of crude protein and amino acids for weanling pig diets.

Table 1. Standardized (SID) ileal digestibility (%) of CP and AA in blood products fed to weanling pigs

^a-d means in the same row with different superscript are different (P < 0.05).

This research report is based on unpublished research by F. N. Almeida, J. K. Htoo, J. Thomson, and H. H. Stein.