Metabolic biomarkers in heifers fed with r-zeta® additive in their diets

The aim of this work was to evaluate different rearing diet strategies with r-zeta® additive in heifers (192.6 ± 19.0 kg body weight, (BW)). The additive formulation includes flavorings that regulate intake, enzymes, microorganisms that modulate the gut microbiota, liver protectants, and anti-inflammatories. The treatments were HR+CS (hay roll (HR) and control supplementation at 1% BW—80% whole corn grain and 20% pelleted protein concentrate); HR+Sr-zeta® (HR and balanced pellet r-zeta® supplementation at 1% BW); HR+SFr-zeta® (HR and self-feeding balanced pellet r-zeta®) and SFr-zeta® (self-feeding balanced pellet r-zeta®). In treatments with the additive and self-feeding, food was offered ad libitum from the first day. Whole-blood samples were collected on days 0, 28, 56 and 83 to evaluate metabolic biomarkers (lactate dehydrogenase (LDH), uremia and glycemia). Continuous variables were analyzed using repeated measures (α = 0.05). All treatments showed similar values ​​of LDH (1200 to 1400 mU/mL; p= 0.0713). The different feeding alternatives affected uremia (p= 0.0143). The animals fed SFr-zeta® had higher values ​​on day 28 compared to supplemented groups. Furthermore, both self-feeding groups showed higher values on day 56​​ in comparison to the supplemented groups. In relation to the reference values ​​(20 to 40 mg/dl), the supplemented animals showed even lower values, which could be considered an insufficient supply of nitrogen compounds in the diet. The self-feeding groups showed normal urea levels throughout the study (30 to 40 mg/dl). A lower value was observed in the blood glucose levels in HR+CS treatment on day 28 compared to the HR+SFr-zeta® group on day 56 (p= 0.0174). For the remaining sampling times, all groups showed similar means. Only the HR+CS group had the range established by other authors (60 to 80 mg/dL), while all groups fed with r-zeta® were above the reference values. The results demonstrate that there was no negative effect on the metabolic variables studied when the additive was included in self-feeding diets without adaptation protocols.