Holstein calves fed a milk replacer with a direct-fed microbial and a starter containing a botanical extract or a direct-fed microbial alone or in combination

Botanical extracts (BE; Apex, Adisseo) have demonstrated enhanced DMI and improved gut health, whereas direct-fed microbials (DFM), such as Lactobacillus acidophilus fermentation product (Excell EX, Pacer Technology Inc.), have demonstrated improved gut health and growth performance of growing Holstein calves. The hypothesis was this combination may be synergistic to neonatal calf growth performance and intestinal health. Eighty 2- to 5-d-old Holstein bull calves were blocked by BW and randomly assigned to 1 of 8 treatments arranged in a 2 × 4 factorial using a randomized complete block design. The main factors were milk replacer (MR) without (control) and with EX added at 5 g/d fed and calf starter (CS). The CS containing no additives (control); CS containing BE at 496 mg/kg; CS containing EX at 2.50 g/kg; and CS containing BE and EX at the same inclusion rates. The MR were fed 2×/d at 0630 and 1800 h along with free choice CS (amounts and orts weighed daily) and water. Weaning occurred after d 42 for the 56-d experiment. No MR by CS main effects interactions were detected for BW, ADG, CS intake, total DMI, feed efficiency, or body frame gain parameters. The BW gain (38.0 and 39.3 kg for control and EX, respectively) for MR main effect was similar for calves fed both MR treatments, whereas CS main effects (38.7, 39.7, 39.2, and 37.2 kg for control, BE, EX, and BE+EX, respectively) was similar among all CS. Gains in body length (10.6 and 10.8 cm), hip width (4.5 and 4.5 cm), withers height, (10.5 and 10.6 cm), heart girth (18.6 and 19.9 cm), and body length (9.1 and 7.9 cm) were similar for calves fed both MR, while CS main effects for hip height (10.5, 10.2, 10.3, and 10.9 cm), hip width (4.7, 4.6, 4.4, and 4.3 cm), withers height (10.7, 10.9, 10.3 and 10.6 cm), heart girth (19.9, 18.9, 18.9, and 19.4 cm), and body length (11.7, 9.1, 8.3, and 8.4 cm) were similar. Total days of a fecal score = 0 was greater for calves fed control MR and BE CS compared with calves fed control MR and the combination of BE+EX, with calves fed the remaining treatments being intermediated and similar. This study demonstrated little calf growth performance and health benefits when feeding a BE or EX alone or in combination compared with calves fed control treatments.