The effects of some essential oils on feedstuff degradability, nutrient digestibility and performance of Holstein feedlot calves

Twelve feedlot Holstein calves (213±17 kg initial BW) were used in a complete randomized design to evaluate the effects of thyme (THY) and cinnamon (CIN) essential oils on performance and nutrient digestibility. Treatments were: 1- control (CON, basal diet), 2-THY (5 g/d/calf) and 3-CIN (5 g/d/calf). Calves were fed ad libitum diets consisting of 15% forage and 85% concentrate for 80 d. Supplementation of THY or CIN did not affect DMI and average daily gain, whereas feed conversion ratio tended (P=0.08) to be improved. Apparent digestibility of nutrients and blood metabolites were not affected by experimental treatments. Four ruminally fistulated Holstein steers (540±35 kg initial BW) were used in a 4×4 Latin square design with 21-d periods and assigned randomly to 1 of 4 treatments: 1- CON (basal diet), 2- THY (500 mg/kg DM), 3- CIN (500 mg/kg DM) and 4- monensin (MON; 33 mg/kg DM) to evaluate the effects of MON, THY and CIN on rumen degradation characteristics of feedstuff. The addition of essential oils (EO) and MON had no effect on DM degradability parameters of soybean meal (SBM), corn grain (COR) and alfalfa hay (ALF). Crud protein degradability characteristics of COR and ALF were not influenced by EO. However, CP degradability parameters of SBM were partly changed by additive treatments (P≤0.05). Results suggest that supplementing bulls with THY and CIN have minor impacts on performance and rumen degradation characteristics of feedstuff.