The effect of feeding calf starter feed containing differentcellulose levels on growth performance, rumen microbiomeand some blood biochemistry values in early weaned calves

Objective: The aim of the study was to examine the effects of cellulose level in the starter feed and early weaning ages on growth performance, rumen development and blood values in calves. Material and Methods: In the study, 24 Holstein male calves with similar body weights and birth weights were investigated for calf starter feed containing different levels of cellulose and the effect of different weaning ages. The trial was arranged in a 2 x 2 trial design. Results: In the study, it was determined that early weaning in the post-weaning period significantly increased the body weight gain (P<0.05). There was no effect of starter feed cellulose level and weaning time on body weight and body measurements. Early weaning of calves increased starter feed consumption at 6 (548 g and 1102 g) and 7 weeks (978 and 1832 g) of the study (P<0.05). Early weaning of calves in the post-weaning period significantly increased starter feed consumption (P<0.05). Among the rumen content parameters examined biochemically, it was determined that acetic acid increased significantly in the early weaning group consuming low-cellulose starter feed in the post-weaning period (57.35 mol/100 mol; P<0.05). It was determined that rumen isobutyric acid value increased (0.16 and 0.42 mmol/L; P<0.05) in the group that consumed starter food with high cellulose level. While Prevotella was found to be the most abundant bacterium at genus level in rumen content taken in all periods, Firmicutes was detected at branch level. In the period before weaning, the highest number of bacteria was seen in the group that consumed low-cellulose starter feed from early weaning, while the lowest number of bacteria was observed in the group that consumed high-cellulose starter feed from early weaning. It was found that there was a significant increase (P<0.05) in the groups. At the same time, it was determined that urea, GGT and GLDH increased significantly (P<0.05) in the early weaning groups. Conclusion: It was determined that different cellulose levels in the starter feed given to the calves and different weaning ages did not adversely affect performance, rumen and blood parameters. Key Words: Calf, Cellulose Level, Early Weaning, Performance, Rumen Microbiome.