Background and Aim: Europe and the USA have banned antibiotics use as growth promoters. There is a need for alternative products that can ensure production and health protection. Prebiotics has been proposed as alternatives because these materials have wide-ranging physiological effects on gut function, activity of the large intestinal microflora, mineral absorption, and immunity. The aim of this study was to determine the effect of three different doses of inulin, a prebiotic, in combination with probiotic Enterococcus faecium (a new synbiotic) on postnatal rumen development by comparing rumen papilla length, width, muscle layer thickness, and content pH level.

Materials and Methods: Randomly selected 23 (±5)-days-old healthy male Holstein crossbreed calves, weighing 50 kg (±5 kg), were randomly allocated to seven groups, ten in each group. The calves were kept in a pen of 5, under the same conditions and were fed twice a day, ∼3.5 liters of whole milk per feeding. Control group (C n=10) was fed with whole milk only (no additives were added). The six other groups (three prebiotics and three synbiotics) received food additives with their morning milk feeding. The source of prebiotics, Jerusalem artichoke powder concentrate (JAPC) contained 50% of inulin. JAPC in doses of 6 g, 12 g, or 24 g were added to the milk. Formed prebiotic groups were denoted as PreG6, PreG12, and PreG24. To evaluate if the addition of the probiotic E. faecium 2×10⁹ colony forming unit g^–1 to manufacturer recommended dose of 0.25 g improves inulin effect on rumen, it was added to all their JAPC doses. The new content synbiotic groups were denoted as SynG6, SynG12, and SynG24. On day 57 of the study, when all calves were approximately 12 weeks old, they were slaughtered in a certified slaughterhouse. Tissue cultures for histological analysis were obtained from Saccus dorsalis and Saccus ventralis of the rumen. Tissue culture staining for histology was carried out using hematoxylin and eosin staining method. Rumen histological samples were used to measure papilla length, width, and muscle layer thickness. Each sample was used to make five measurements on the present rumen papilla.

Results: The results showed that by adding 12 g of inulin to whole milk when feeding calves improves rumen papilla development, which is seen by increased length and width of papilla, especially in the Saccus ventralis region. By combing this dose of inulin with 0.25 g of E. faecium, a significant increase of papilla is achieved. Saccus ventralis muscle layer in the rumen is thicker than it is in Saccus dorsalis regardless of addition of prebiotics or synbiotics.

Conclusion: The addition of inulin to whole milk can influence the pH of the rumen by making it more alkaline. The addition of prebiotic inulin and a novel synbiotic (inulin combined with E. faecium) can accelerate postnatal rumen development and improve its functionality.

Keywords: calf, pH, prebiotic, rumen, symbiotic.