Impact of Essential Oils on the Growth Performance of New-Born Holstein Calves

Plant extracted essential oils (EO) can exhibit antimicrobial properties that make them potential alternatives to antibiotics. The objectives were to evaluate the use of plant EO (oregano blend) on the growth, development, health status, and rumen development of newborn calves. Forty (40) Holstein heifer calves were blocked by birth date and alternately assigned to 1 of 2 calf starters (CS). Twenty calves receive a Control (CN) CS without EO and 20 calves received the EO CS (40 g/t). Calves were fed the CS for ad libitum consumption starting the 3^rd day after birth through 70 d with weaning occurring at 42 d of age. Calves fed EO CS demonstrated significantly (P < 0.05) greater dry matter intake (DMI) than calves fed CN for the time periods of 8-14 (0.14 and 0.16 kg/d for CN and EO, respectively) to 64-70 d of age (2.95 and 3.11 kg/d). The average daily gains (ADG) were significantly (P < 0.05) greater for calves fed EO (0.78 and 0.87 kg/d) compared to calves fed CN throughout the study. At 70 d of age, calves fed EO demonstrated significantly (P < 0.01) greater body frame growth measurements (hip height 96.2 and 101.9 cm; body length 98.0 and 104.6 cm; abdominal girth 96.6 and 103.4 cm; chest girth 97.5 and 101.8 cm; and pastern 12.8 and 14.1 cm) than calves fed CN. Scour incidences were lower for calves fed EO compared to calves fed C (P＜0.01). The blood total serum protein (54.2 and 57.2 mg/dL), IgG (110.8 and 117.2 mg/dL), IgA (5.8 and 9.0 mg/dL), and IgM 19.8 and 22.4 mg/dL) concentrations were significantly (P < 0.01) higher for calves fed EO compared to calves fed C at 14 d. The blood volatile fatty acid concentrations were significantly (P < 0.01) higher for calves fed EO compared to calves fed CN. The calves fed EO demonstrated significantly (P ＜ 0.01) greater nutrient digestibilities of dry matter (88.61 and 92.2%), crude protein (86.7 and 91.9%), acid detergent fiber (48.1 and 66.0%), neutral detergent fiber (49.2 and 66.8%), and starch (98.5 and 99.4%),) compared to calves fed C. This study demonstrated that incorporating an EO in a CS resulted in positive benefits, similar to antibiotics, including increase calf growth, ruminal development, intestinal health, and nutrient digestibility when compared to a CN CS without EO.