Effect of prebiotic and synbiotic injected in ovo on performance, meat quality and hystopathological changes in muscle of broiler chickens

In poultry farming, the intestinal microbiota and the “gut health” are topical subjects, especially since the EU has banned the use of auxinic antibiotics to avoid the onset of antibiotic resistance and safeguard the consumer health. As a consequence of their prohibition, a higher incidence of enteric diseases is observed in poultry farming with loss of productivity and increased mortality. In the post-antibiotics era, probiotics and prebiotics are proposed as a solution to the intestinal problems of poultry. Studies carried on these bioactives, administered in feed or water, show conflicting results due to the different environmental conditions (experimental and field conditions) and the way of use. The “in ovo” injection of pre-/pro-biotics and their combination (synbiotic), an emergent and original technique, shows promising results similar to those of auxinic antibiotics. The work aimed to evaluate the effects of these substances, “in ovo” administered, on growth performance, meat quality traits (cholesterol content, intramuscular collagen properties, fiber measurements), and the presence of histopathological changes in the pectoral muscle (PS) of Ross 308 broiler chickens. On d 12 of incubation, 480 eggs were randomly divided into five experimental groups treated with different bioactives, in ovo injected: C, control with physiological saline solution; T1 with 1.9 mg of Raffinose Family Oligosaccharides (RFOs); T2 and T3 with 1.9 mg of RFOs enriched with two different homemade probiotic bacteria (from Microbiological Bank of Institute of Biochemistry and Biophysics, Warsaw, Poland), specifically 1,000 cfu of Lactococcus lactis ssp. lactis SL1 and Lactococcus lactis ssp. cremoris IBB SC1, respectively; T4 with commercially available synbiotic Duolac, containing 500 cfu of both Lactobacillus acidophilus and Streptococcus faecium with the addition of lactose (0.001 mg/embryo). Among the hatched chickens, sixty males were randomly chosen (12 birds for each group) andreared according to the animal welfare recommendations of European Union directive 86/609/EEC in an experimental poultry house that provided good husbandry conditions. Birds were grown up to 42 d in collective cages (n = 3 birds in each 4 cages: replications for experimental groups). Broilers were fed ad libitum commercial diets according to their age and water was provided ad libitum. Amounts of feed offered to each cage were recorded, and uneaten feed in each cage was weighed daily (from 1 to 42 d). Cumulative feed intake and feed conversion ratio (FCR) were calculated on a cage basis. At 42 d of age, broilers were weighed individually (after a fasting period of 12 h) and then were electrically stunned and slaughtered at a commercial poultry slaughterhouse. At slaughter, hot carcass weight was recorded, and carcass yield percentage was calculated. Abdominal fat was removed, measured and its percentage was calculated based on hot carcass weight. The pectoral muscle was removed from all carcasses (n = 60) and its percentage was calculated based on hot carcass weight. In addition, pectoral muscle pH was recorded at 45 min (pH45), 12 h (pH12), and 24 h (pH24) postmortem. Samples of the right pectoral muscle of 40 animals, 8 birds from each experimental group, were taken and frozen in liquid nitrogen (-196ºC) for histological and histopathological analyses. The left pectoral muscle was vacuum packaged and stored frozen (-40°C) until intramuscular collagen (IMC) and cholesterol analyses. To verify significant differences in relation to the treatments, the data were evaluated by using 1-way ANOVA and means were separated by Scheffe’s battery of pairwise tests (SPSS Inc., 2010). In ovo prebiotic and synbiotics administration had a low effect on investigated traits, but depend on the kind of bioactives administered. Commercial synbiotic treatment (T4) reduced carcass yield percentage, and the feed conversion ratio was higher in T3 and T4 groups compared with other groups. The abdominal fat, the ultimate pH, and cholesterol of the PS were not affected by treatment. Broiler chickens of treated groups with both slightly greater PS and fiber diameter had a significantly lower amount of collagen. The greater thickness of muscle fibers (not significant) and the lower fiber density (statistically significant), observed in treated birds in comparison with those of C group, are not associated with histopathological changes in the PS of broilers. The incidence of histopathological changes in broiler chickens from examined groups was low, which did not affect the deterioration of meat quality obtained from these birds. Overall, the results obtained at the end of this work have asserted how the in ovo administration, in showing greater effectiveness in terms of uniformity of application, dose used and duration of treatment, as well as homogeneity of the study population (age, weight), may represent a valid alternative to the traditional and well-established methods of post-hatching administration (feed and water) in order to minimize all those variables that could affect the effectiveness of bioactive. Moreover, the study has provided information for an effective application of these natural agents to be used in the future in breeding industry, with significant and positive impact on animal welfare and public health.