EVALUATION OF ESSENTIAL OIL AND INJECTABLE TRACE MINERAL ON BULL GROWTH PERFORMANCE AND FERTILITY

ABSTRACT The objective of this study was to evaluate the effects of an essential oil mixture (EOM) in conjunction with injectable trace mineral (ITM) on growth performance and fertility of growing, yearling bulls. Angus bulls born in the consecutive springs (2016; n=37 and 2017; n=29) were weaned, weighed and stratified by weight and sire across two diet treatment groups (EOM and CONTROL). Additionally, a similar stratification procedure was used, generating injectable trace mineral subsets (ITM-Yes and ITM-No) of bulls, within each diet group. In 2016 (yr 1), d -35 and 2017 (yr 2) d -32, bulls were weaned and exposed to CONTROL diet for total mix ration (TMR) adaptation. At d 0, weight and scrotal measurements were taken as well as dietary treatments applied. Weight and scrotal measures were collected every 28 days, with ITM implemented at d 42 and 70 in yr 1 and d 47 and 75 in yr 2. Final assessment of weight and scrotal measurement, as well as semen quality measures, were concluded on d 98 in yr 1 and d 103 in yr 2. Differences due to ITM as a main effect were observed in the overall weight measures only, as bulls in the ITM-Yes subset exhibited higher overall weight measures (P = 0.05), even though no weight differences were observed at d 0 as a result of stratification structure. Differences in post-weaning average daily gain (ADG) and semen motility scores were observed due to the diet × ITM (year) interaction. The ITM-Yes subset bulls of yr 2, achieved a greater post-weaning ADG compared to the ITM-No subset within the EOM diet consuming group (P < 0.01). Implementing ITM can improve weight gain and augment semen motility scores while dietary EOM alone has limited impact on growth measures and semen motility.