The effects of probiotic Lactobacillus acidophilus and/or prebiotic mannan oligosaccharides on growth performance, nutrient utilization, blood metabolites, faecal bacteria, and economics of crossbred calves.

Background: The ban on antibiotics as growth promoters paved the way for probiotics and prebiotics as growth promoters in animal production. Aims: The present study was conducted to evaluate the effect of probiotic Lactobacillus acidophilus and/or prebiotic Mannan oligosaccharides on growth performance, blood biochemical variables, and faecal bacterial count in crossbred calves. Methods: Fifteen-day-old crossbred calves (n=24) were divided into four groups, each consisting of six calves, and subjected to different experimental diets. The control group (T0) received a basal diet without any additives. The T1 and T2 groups received the basal diet and the probiotic (L. acidophilus, 2 × 1010 cfu/g) @ 1 g/calf per day and prebiotic (Mannan oligosaccharide) @ 4 g/calf per day, respectively. Calves of the T3 group were offered a basal diet and synbiotic (L. acidophilus, 0.5 g + Mannan oligosaccharide, 2 g/calf per day). The feed additives were mixed in milk. Results: The results of 90 days feeding trial showed that calves of the T3 and T1 groups had higher (P<0.05) body weight (BW) gain and dry matter digestibility than the control. Feeding the probiotic showed a positive effect (P<0.05) on body length at the first, second, and third months, compared to the control. The blood serum total protein and globulin concentrations in the T1 group, on days 30 and 90, and T3 group, on day 90, were higher (P<0.05) than those of the control. All the treatment groups (T1, T2, and T3) showed a reduction (P<0.05) in faecal coliform and E. coli count, compared to the control, on the 15th and 30th days of the study. Additionally, the T2 group showed a significant coliform count reduction on days 45 and 60 of the study. Conclusion: The dietary addition of L. acidophilus, 2 × 1010 cfu/g @ 1 g/calf per day and the combination of L. acidophilus, 0.5 g + Mannan oligosaccharide, 2 g/calf per day improved growth performance, serum biochemical values, and favourable gut microbiota.