Feed additive carriers affected the physiological effects of a lactobacilli-based pro- and postbiotic in broilers

To promote growth performance and health of broiler during production, additives, like pro- and postbiotics, are often used and most of them use carriers. This study aimed to investigate if carriers can modulate the physiological effects of two lactobacilli-based pro- (Pro) and postbiotic (Post) additives, and to gain more insight into their physiological effects in the absence of carriers, in broilers fed a non-starch polysaccharide-rich diet reared under practical housing conditions. A total of 1,600, one-day-old male Ross 308 chicks were equally distributed among 5 treatments (control, Pro and Post with and without their respective carriers) with 8 replicate pens each and 40 broilers/pen. Growth performance parameters, footpad lesions, and blood plasma physiological parameters related to nutrition and immunity were determined. On d35, Pro increased body weight (BW) (+2.1%; p = 0.025), while its carrier negated this effect (-1.9%; p = 0.047). Post did not affect d35 BW but increased the feed conversion ratio (FCR) by 1.3% (p = 0.041), while its carrier increased BW (+2.4%; p = 0.013), and lowered FCR (-1.3%; p = 0.042). Growth performance parameters showed a beneficial effect of Pro but not Post, while the use of their respective commercial carriers had a growth-depressing and -promoting effect, respectively. Carriers also affected the footpad lesion score, and blood parameters related to nutrition and immunity. These results highlight that additive carriers can modify the effects on broiler growth and metabolism of the pro- and postbiotic additives to which they are added. The occurrence of an additive-carrier interaction indicates that carriers for pro- and postbiotic additives for broilers must be carefully selected.