Effect of Dietary Inclusion of a Spirulina (Arthospira Platensis) By-product in Post-weaning Diets on Pig Growth to Day 44 Post-weaning, Haematology and Selected Intestinal Gene Expression

Algal biomass from processing of Spirulina could be a valuable high protein sustainable feed ingredient. This study evaluated a by-product of phycocyanin extraction from Spirulina, which underwent high pressure treatment followed by spray-drying (93.4% dry matter; 41.6% crude protein). The aim was to evaluate the effect of replacing conventional feed ingredients with this Spirulina by-product on growth, haematological profile and intestinal gene expression in post-weaning (PW) pigs. At weaning,126 pigs (9.2 ± 0.09 kg; 29 ± 0.95 days) were formed into 30 pen groups containing 3 pigs and 18 pen groups containing 2 pigs. Pen groups were blocked on pen group size at weaning, sex (entire male and female) and weaning weight and within block randomly assigned to one of three dietary treatments (n = 16 pens per treatment): 1. Control diet, 2. Control diet plus 1% Spirulina by-product inclusion (SP1), and 3. Control diet plus 5% Spirulina by-product inclusion (SP5). Pigs were fed the experimental diets from weaning until day (D) 21 PW, after which a common diet was fed until D44 PW. At D6 PW, one pig from each pen containing 3 pigs (n = 10 pigs/treatment) was euthanised to collect blood and intestinal tissue for haematological and gene expression analyses, respectively. Pig growth was analysed using PROC MIXED, while intestinal gene expression and haematology were analysed using PROC GLIMMIX in SAS. Dietary treatment was the fixed effect, block was included as a random effect and weaning weight included as a covariate when significant. Pig body weight at D6 PW was 3.9% lighter (P ≤ 0.05) and average daily gain from D0-6 PW tended to be 27.8% and 26.9% lower for SP5 pigs compared to Control and SP1, respectively (P = 0.06). Average daily feed intake from D0-6 PW was 16.4% lower in SP5 pigs compared to Control (P ≤ 0.05) but not significantly different to SP1. Dietary treatment did not significantly affect pig growth performance parameters from D0-21 PW or D21-44 PW. Blood haemoglobin concentration was lower in SP1 compared to Control and SP5 (P < 0.01). Mean corpuscular volume tended to be lower in SP1 and SP5 compared to Control (P = 0.07). Dietary treatment did not influence expression of Claudin-4 or Mucin-2 in the duodenum, jejunum, or ileum. In conclusion, Spirulina by-product inclusion at 5% temporarily reduced growth during the first week PW only, while Spirulina by-product inclusion at 1% had no negative impact on pig growth at any stage. Therefore, restricting dietary Spirulina by-product inclusion to 1% during the first week PW is warranted. Despite the minor effects on haematological parameters observed in response to dietary inclusion of the Spirulina by-product, values remained within reference ranges. These results suggest that this Spirulina by-product can be safely incorporated into post-weaning piglet diets at inclusions of up to 5%.