Male Holstein calves fed a milk replacer and pelleted calf starter containing a botanical extract or a direct fed microbial (DFM) alone or in combination.

Botanical extracts (BE; Apex, Adisseo, North America, Atlanta, GA) are known to enhance DMI and gut health, while direct fed microbials (DFM), such as a lactobacillus acidophilus fermentation product (EX: Excel; Pacer Technology, Inc., Murtaugh, ID), has demonstrated improved gut health and growth performance when fed to growing neonatal Holstein calves. The hypothesis was this combination may be synergistic to neonatal calf growth performance and intestinal health. Eighty 2-5-d old Holstein bull calves were blocked by BW and randomly assigned to 1 of 4 treatments arranged using a randomized complete block design. Treatments were: 1) Control: no additives; 2) BE added at 496 mg/kg to the calf starter (CS); 3) EX added to the CS at 2.50 g/kg with EX added to the milk replacer (MR) at 5 g/d; and 4) BE&EX: BE and EX added to CS at same rates and added EX to MR. Calves received 0.283 kg MR in 1.9 L fed 2 x/d for the first 14 d, then increased to 0.42 kg in 2.84 L fed 2x/d through d 35, followed by 0.42 kg MR in 2.84 L fed 1x/d through d 42, followed by weaning. The CS was a 25% CP DM basis mini-pellet and the MR was a 22:20 (CP:fat) fed 2x/d at 0630 and 1800 h along with free choice water. Weaning occurred after d 49 of the 70-d experiment. Calves fed CS EX alone demonstrated greater BW gain compared with calves fed BE&EX with calves fed Control and BE being intermediate and similar (63.9, 63.5, 65.0, and 59.7 kg for Control, BE, EX, and BE&EX, respectively). Total DMI (MR+CS) was lower for calves fed BE&EX compared with calves fed the remaining treatments (116.5, 114.2, 116.4, and 104.9 kg). The feeding of a BE in combination with EX (DFM) to neonatal calves reduced BW during wk 8, 9, and 10 and reduced 0-70 d ADG (874.7, 870.0, 889.7, and 817.6 g/d) compared with calves fed the remaining treatments. Calves fed BE&EX demonstrated the lowest calf starter intake during wk 4 through 10 compared with calves fed the other treatments. The study average calf starter intake for calves fed Control and EX was greater compared with calves fed BE&EX with calves fed BE being similar and intermediate. Calves fed EX and BE&EX demonstrated greater total d of fecal scour score = 1 (5.4, 5.7, 8.0 and 8.3 d) compared with calves fed Control and BE. Gains in frame measurements of hip height, hip width, withers height, and body length were similar while calves fed BE&EX demonstrated lower heart girth gains (19.2, 18.3, 19.7 and 17.6 cm) during the milk feeding phase (0 - 7 wk) compared with calves fed Control and EX, with calves fed BE being similar and intermediate. It is not known why this study demonstrated an antagonism between BE and EX in growth performance and feed intake but further research is needed to identify the mechanism of action.

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.

Effects of weaning on regulators of volatile fatty acid absorption and intracellular pH in Holstein calves.

This study examined the effects of changes in rumen fermentation during the weaning transition on abundance of transporters involved in volatile fatty acid (VFA) absorption or intracellular pH homeostasis. Holstein bull calves (n = 27) were assigned to 1 of 3 treatment groups in a randomized, complete block design: 2 preweaning groups [animals fed milk only (PRE-M) or milk, calf starter, and hay (PRE-S)] and 1 postweaning group (animals fed milk, starter, and hay with a 2-wk weaning transition; POST-S). Calves were euthanized at 42 d of age (PRE-M and PRE-S) or at 63 d of age (POST-S), and rumen epithelium and rumen fluid samples were collected. Rumen fluid was analyzed for VFA concentration, and rumen epithelium was analyzed for the abundance of VFA transporter monocarboxylate transporter isoform 1 (MCT1) and the intracellular pH regulators sodium bicarbonate co-transporter 1 (NBC1) and sodium-proton exchanger 3 (NHE3) protein. Preweaning, total VFA concentrations tended to increase and NBC1 abundance increased with starter intake. Between pre- and postweaning, total VFA concentrations increased but NHE3 protein abundance decreased. In calves, rumen epithelial development during the weaning transition appears to show more pronounced changes in intracellular pH homeostasis than in VFA transport capacity.