Growth performance and carcass traits of growing and finishing pigs fed diets with a partial to total replacement of soybean meal with Spirulina powder

The protein sources in pig diets strongly rely on soybean meal, but its production has been associated with soil degradation, deforestation and loss of biodiversity. Microalga Spirulina can be a potentially more sustainable alternative to soybean meal, but comprehensive information about its use in growing pigs is still lacking. This study aimed to evaluate the effects of partial to full replacement of dietary soybean meal with Spirulina on the growth and carcass traits of growing pigs and on the chemical and physical attributes of the meat. Eighty-eight pigs, gilts and barrows mixed together, with initial body weight of 52.4 ± 4.2 kg, were allotted into 4 isoenergetic, isoproteic, and isoaminoacidic dietary treatments, which included a conventional control diet based on cereals and soybean meal and one of 3 diets formulated by replacing nearly 33%, 66% or 100% soybean with Spirulina. Each treatment had 2 pens (11 pigs/pen), which were equipped with electronic feeders that were able to record individual feed intake. After 138 d on feed, at 174.9 ± 6.4 kg body weight, the pigs were slaughtered, and the carcass traits and meat quality parameters from loin samples were assessed. The palatability of feeds was not depressed in pigs fed Spirulina, even when the soybean was completely replaced by the microalga. The incorporation of Spirulina in the diets in place of soybean did not impair the growth rate or feed efficiency, irrespective of the extent of replacement. The carcass traits and yield of commercial cuts were comparable for all Spirulina-included compared with those of the soybean-based groups, and the same was found for the chemical and physical attributes of loin meat. The results obtained at the herd and slaughter levels revealed that the replacement of soybean meal with Spirulina did not negatively affect the growth or carcass traits of growing pigs or the main attributes of meat. Therefore, this study provides, for the first time, insights into the technical possibility of switching growing pig feeding systems toward more environmentally sustainable diets by including a microalga originating from landless feed production systems, which does not result in soil degradation or loss of biodiversity.