Development of livestock feed additives using porcine blood cells.

Livestock blood discarded during slaughtering has potentially valuable components such as plasma proteins and haemoglobin. Plasma is used as a feed additive following processing via different methods, including spray drying, whereas blood cells have been underutilized. In this study, we developed haemoglobin hydrolysate (HH) and iron-enriched residue (IER) from porcine blood cells and investigated whether their oral administration regulates the immune system and gut microbiota in growing rats. Twenty-one Sprague-Dawley male rats (n = 7) were used during a 4-week trial and were fed a control, HH or IER diet. The ratio of beneficial bacteria such as Lactobacillus and Akkermansia strains increased in rats fed HH or IER diets. Moreover, compared with the control group, the IER group had an elevated ratio of Lactobacillus to Enterobacteria, which is regarded as an index of beneficial aspect in the gut. Phagocytosis of peripheral blood leucocytes was higher in the HH and IER groups than in the control group. The level of plasma immunoglobulin G increased to approximately 72.7 mg/ml and 152.0 mg/ml in the HH and IER groups, respectively, which was significantly (p < 0.05) higher than that in the control group. These results confirm that HH and IER developed in this study may be a potential additive for animal feeds.