Evaluation of lactoferrin administration as an antibiotic alternative growth promoter: impacts on rabbit's growth, meat quality, blood biochemical parameters, immune status, antioxidant status, and tissue histology.

Antibiotic-resistant microbes have emerged because of the widespread misuse of antibiotics in modern animal production. To overcome antibiotic resistance, the name lactoferrin (Lf) is promising since it is a naturally safe alternative to antibiotics. Considering the few sources available, this study evaluated the effects of Lf administration as a possible alternative to antibiotics on the growth, meat quality, blood hematology, hepato-renal function, antioxidant, and immune status of rabbits. A total of 60 four-week-old V-line male weaned rabbits (average body weight 530 ± 20 g) were randomly distributed to three experimental treatments (TRTs). The first TRT was the control group (CON). In the 2nd and 3rd TRTs, rabbits were orally administered with 1 mL oxytetracycline (OXY)/kg BW and 300 mg Lf/kg body weight (BW), respectively. The TRTs were applied orally twice weekly for 8 weeks. The results showed that the BW of rabbits treated with Lf was higher than the CON rabbits at the 8th and 12th week of age (P < 0.05). The average daily gain was higher in the Lf-treated group than in the CON and OXY-treated groups in the 12th week (P < 0.01). The meat quality parameters showed that Lf produced bright red meat with the highest lightness and lowest yellowness and hue values compared to OXY TRT and CON rabbits. At the same time, the other technological meat parameters, such as water holding capacity, drip loss (24 and 48 h), cooking loss, and Warner-Bratzler Shear Force, were not significantly changed. The serum levels of AST, ALT, ALP, and urea were reduced in the Lf-treated group and increased in the OXY-treated group compared with the CON. The total and direct bilirubin levels and creatinine and uric acid levels were increased in the OXY-treated rabbits. The total protein and globulin serum levels were raised in the Lf-treated rabbits and reduced in the OXY-treated rabbits. The albumin level decreased in the OXY-treated group. The serum levels of IgG and IgM were higher in the LF-treated animals compared to the CON and OXY-treated groups (P < 0.01). The serum levels of IgA, IgD, and IgE were increased in both Lf- and OXY-treated groups compared with the CON group. The hepatic and renal MDA and NO concentrations were decreased in the LF-treated group and increased in the OXY-treated group. The opposite is true for the activity of glutathione peroxidase, glutathione-reduced glutathione-S-transferase, and catalase. Lactoferrin administration upregulated the growth-related genes and downregulated the proinflammatory and apoptotic genes. In conclusion, lactoferrin in a dose of 300 mg /kg BW is a potential antibiotic alternative for improving rabbits' growth, health, meat quality, antioxidant, and immune status.