Effects of monensin sodium and plant extracts containing cinnamaldehyde, capsicum oleoresin, and eugenol on days to puberty, gain, pregnancy rate, and feed efficiency in developing beef heifers receiving a high roughage diet

The objectives of the studies were to determine the effect of monensin sodium vs. a combination of plant extracts containing cinnamaldehdye, capsicum oleoresin, and eugenol on ADG, feed efficiency, pubertal onset, subsequent conception rate following AI, and differences in docility among yearling beef heifers.;During exp. 1, Angus heifers (n = 105; initial BW 347.4 +/- 29.5 kg) were utilized in a completely randomized block design for a 72 d experiment. Heifers were randomly distributed within 5 weight blocks, and assigned to one of 3 treatments: monensin sodium (MON); combination of plant extracts cinnamaldehyde, capsicum oleoresin, and eugenol (CCE); or no feed additive (CON). Performance measurements included ADG, DMI, G:F, and pubertal onset. There was a tendency (P = 0.06) for CON and MON heifers to have greater ADG compared to CCE ). There was a tendency (P = 0.09) for CON heifers to have greater AI pregnancy rate than females that received MON (59.8 vs. 44.2%). There were no differences (P > 0.10) for DMI, G:F, or pubertal onset between treatments.;During exp. 2, of the study, Angus heifers (n = 107; initial BW of 318.4 +/- 26.1 kg) were utilized in a balanced randomized block design using a 2 X 2 factorial arrangement of treatments. Females were stratified according to initial BW and randomly assigned to pens. Pens were randomly assigned to 1 of 4 treatments: 1) monensin sodium (MON); 2) combination of plant extracts cinnamaldehyde, capsicum oleoresin, and eugenol (CCE ); 3) no feed additive (CON); or a combination of both monensin sodium and a combination of plant extracts cinnamaldehyde, capsicum oleoresin, and eugenol (COMB). The MON premix was fed to supply 200 mg·hd-1·d-1 monensin sodium, the CCE premix was fed to supply 12,000 mg·hd-1·d -1 of the plant extracts, and the COMB premix was fed to supply 12,000 mg·hd-1·d-1 of the plant extracts as well as 200 mg·hd-1·d-1 monensin sodium. During exp. 2, blood samples were collected via jugular venipuncture at 11 d intervals for progesterone concentration via RIA analysis to determine time of pubertal onset. Once a blood sample reached a progesterone concentration ≥1 ng/mL, the heifer was considered to be pubertal. Also during exp. 2, subjective chute scores (CS) and objective exit velocity (EV) measurements were taken at 11 d intervals for each heifer. Weight for each heifer was also collected at 11 d intervals to calculate ADG. Ort samples were collected and weighed every other d to calculate feed intake and feed efficiency. Performance measurements included ADG, DMI, G:F, initial BW, 60 d BW, and final BW. Behavioral measurements take on d 0, 60, and 120 included EV and CS. Reproductive performance measurements included age at puberty, pregnancy rate to AI, BCS, and BW at breeding.;Heifers in the COMB and CCE treatment group that received a combination of plant extracts cinnamaldehyde, capsicum oleoresin, and eugenol along with monensin sodium had a greater ADG (P = 0.04) than the CON and the MON heifers. These data explain that DMI was reduced (P = 0.02) for heifers in the MON (9.80 kg +/- 0.57) and the COMB (9.16 kg +/- 0.57) treatments when compared to females in both the CON (10.55 kg +/- 0.57) and CCE (11.36 kg +/- 0.57) treatment groups. There were no differences (P > 0.05) between treatments for G:F, initial BW, 60 d BW, or final BW.;Differences in behavior were measured between treatments. Final EV was greater (P = 0.05) for heifers in the CCE (0.66 m/s) as well as the COMB (0.73 m/s) treatment groups when compared to females in the CON (0.71 m/s) and MON 1.19 (m/s) treatments. There was no difference ( P > 0.05) between treatments for initial, midpoint, or final CS; initial and midpoint EV were also not affected (P > 0.05) by treatment.;Receiving monensin sodium (347.1 d), a combination of plant extracts (342.5 d), or a combination of the 2 (355.4 d) decreased (P = 0.03) age at puberty when compared to controls (370.6 d). Breeding weight was collected the last d of supplementation, heifers in the CCE (440.06 kg) exhibited the greatest BW at breeding compared to MON (422.6 kg), COMB (422.8 kg), or CON (429.71 kg) There was a tendency (P = 0.06) for CON and MON heifers to have greater ADG compared to CCE . Body condition scores, response to estrus synchronization, and pregnancy rate were not (P > 0.05) different by treatment. (Abstract shortened by UMI.).