Effects of Probiotics, Prebiotics and Synbiotics Injected in Ovo on the Microstructure of the Breast Muscle in Different Chicken Genotypes.

The aim of the study was to analyse the effect of probiotics, prebiotics and synbiotics injected in ovo on day 12 of embryonic development on the microstructure of the superficial pectoral muscle (musculus pectoralis superficialis) from 42-day-old chickens of different genotypes: broilers (Ross 308) and general-purpose type (green-legged partridge (GP) chickens Zk-11, native chickens). Incubated eggs were divided into four groups (each genotype separately) depending on the substance injected in ovo: normal saline (C, control); subsp. (PRO); galactooligosaccharides, GOS (PRE) or GOS + (SYN). After hatching, chicks were placed in eight replicated pens (four pens/genotype group). There were eight birds per pen. In total, 64 birds were used in the experiment. Birds were slaughtered at the age of 42 days, and samples of superficial pectoral muscles were taken for analysis. The microstructure of the pectoral muscles was evaluated using the cryosectioning (frozen tissue sectioning) technique and staining with haematoxylin and eosin. Statistical analysis revealed that the in ovo injection of probiotics, prebiotics and synbiotics had no significant effect on the diameter of muscle fibres from chickens of the two genotypes. The number of fibres in the muscles from green-legged partridge chickens was about three-fold higher than the fibre density in the muscles from broiler chickens, with the fibre diameter being two-fold smaller. This fact may indicate a greater tenderness of meat from GP chickens compared to the meat from Ross 308 broilers. In the case of broilers, a prebiotic (GOS) was the most effective bioactive substance in reducing the number of histopathological changes. Considering muscles from GP chickens, the number of normal fibres was highest in birds treated with the probiotic. These findings indicate that the microstructural features of pectoral muscles depend not only on the type of the injected bioactive substance but also on the genotype of chickens.