Effects of supplemental humic substances on growth performance, blood characteristics and meat quality in finishing pigs

A total of forty-eight finishing pigs were used to determine the effects of humic substances (HS) on growth performance, blood characteristics, and meat quality. The finishing pigs were assigned randomly by weight to three treatments. The dietary treatments included: 1) Control (CON; basal diet), 2) HS1 (basal diet + 5% humic substances) and 3) HS2 (basal diet + 10% humic substances). Results of the whole experimental period showed that addition of 10% HS to the diet, significantly increased average daily gain (ADG) and gain/feed (G:F) (P < 0.05). At the end of the experiment, the relative lymphocyte counts (% of total white blood cells) of pigs fed HS2 diet were higher (P < 0.05) than that of pigs fed CON diet. The Minolta color parameter a⁎ of pigs fed HS2 was similar to that of pigs fed HS1, however, it was higher (P < 0.05) than that of pigs fed CON diet. The inclusion of either 5% or 10% HS significantly decreased backfat thickness (P < 0.05). The marbling score was increased significantly (P < 0.05) when diets were supplemented with HS at a level of 10%. The results of this study suggest that HS might be utilized as a feed additive in the diet. It could improve growth performance, relative lymphocyte counts and meat quality.