tended to have a greater total VFA concentration (35.60 ± 11.4 vs. 11.90 ± 11.8 mM) but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.17 ± 0.21, respectively). Between PRE-S (wk 6) and POST-S (wk 9), calf starter intake increased (250 ± 219 vs. 2,239 ± 219 g/d), total VFA concentrations increased (35.6 ± 11.4 vs. 154.4 ± 11.8 mM), but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.40 ± 0.22, respectively). Compared with POST-S, POST-B calves had greater starter intake in wk 7, 8, and 9, but POST-B tended to have lower total VFA concentration (131.0 ± 11.8 vs. 154.4 ± 11.8 mM) and lower mean ruminal pH (5.83 ± 0.21 vs. 6.40 ± 0.22). In conclusion, the weaning transition does not appear to affect rumen pH and VFA profile, but supplementing rumen-protected butyrate during the weaning transition increased starter intake and average daily gain. Further, these data suggest that the ability of the rumen to manage rumen pH changes fundamentally postweaning. Why weaned calves with lower rumen pH can achieve higher calf starter intakes is unclear; these data suggest the effect of rumen pH on feed intake differs between calves and cows.

The objective of this study was to evaluate growth and performance of postweaning heifers supplemented with monensin (MON), sodium butyrate (SB), or the combination of MON and SB (MSB) compared with heifers not receiving these feed additives. Forty Holstein heifers [mean age 84.2 ± 1.2 d; body weight (BW) 99.8 ± 10.8 kg (mean ± SD)] were housed in a freestall barn, blocked by birth date, and randomly assigned to 1 of 4 treatments in a randomized complete block design. Treatments were (1) 100 g of soybean meal carrier (control; CON); (2) 0.75 g of SB/kg of BW + carrier (SB); (3) 1 mg of MON/kg of BW + carrier (MON); (4) 1 mg of MON/kg of BW + 0.75 g of SB/kg of BW (MSB). Data were analyzed using single degree of freedom contrasts evaluating CON versus additives (ADD), SB versus MON, and SB and MON versus MSB. Treatments were hand-mixed daily. Feed and orts were measured daily and frozen at −20°C. Orts samples were subsampled for dry matter (DM) determination, and total mixed ration samples were taken weekly and composited monthly for DM and nutrient analysis. Initial BW, heart and paunch girths, body length, blood samples, and fecal coccidia counts were measured before the start and weekly during the 12-wk trial. Blood samples were analyzed for glucose, plasma urea nitrogen (PUN), and ketone concentrations. Apparent totaltract nutrient digestibility was determined from d 21 to 27 and from d 63 to 69 using acid detergent insoluble ash as a marker. Daily dry matter intake (DMI) and metabolizable energy intake were increased in ADD compared with CON, and average BW, final BW, and heart girth tended to increase. Whereas MSB tended to be greater than SB and MON for heart girth, feed efficiency was greater with MON compared with SB. Compared with CON, ADD decreased coccidia counts. No effect of treatment on PUN was detected. Monensin and SB tended to have greater plasma glucose than MSB did. Average blood ketone concentrations were greater with ADD versus CON, in SB versus MON, and in MSB versus SB and MON. During the wk-3 digestibility phase, DMI tended to be greater in heifers fed SB versus MON, as well as in heifers fed MSB versus SB and MON. Digestibility of nutrients were similar, except that starch digestibility was increased in heifers fed MSB versus SB and MON. During the wk-9 digestibility phase, DMI and digestibility of nutrients were similar, except NDF, which tended to be greater in CON than in ADD. Overall, ADD resulted in positive growth and reduced coccidia compared with CON.

Botanical extracts (BE; Adisseo North America, Altanta, GA) are known to enhance dry matter intake (DMI) and gut health, while direct-fed microbials (DFM), such as a actobacillus acidophilus fermentation product (RC: RumaCell DF 5G; Pacer Technology, Inc., Murtaugh, ID), had shown improved gut health and growth performance of growing Holstein calves. The hypothesis was this combination may be synergistic to neonatal calf growth performance. Eighty 2- to 5-d old Holstein bull calves were blocked by body weight (BW) and randomly assigned to one of 8 treatments arranged in a 2 x 4 factorial using a randomized complete block design. Main factors were 2 milk replacers (MR) without (Control) and with RC added at 5 g/d fed with calf starter (CS) main effect of 4 experimental CS being: 1) Control: no additives; or 2) BE added at 496 mg/kg to the calf starter (CS); 3) RC added to the CS at 2.50 g/kg; and 4) BE&RC: same BE and RC rates to CS. The CS was a 25% crude protein dry matter basis with the MR being a 22:20 (CP:fat) fed 2x/day at 0630 and 1800 h along with free choice water. Weaning occurred after d 42 for the 56-d experiment. No significant (P > 0.10) MR by CS interactions were detected for BW, BW gain, CS intake, total DMI, or feed conversion parameters. The BW gain (38.0 and 39.3 kg for Control and RC, respectively) for MR main effect was similar (P > 0.10) for calves fed both MR, while CS main effect (38.7, 39.7, 39.2, and 37.2 kg for Control, BE, RC, and BE&RC, respectively) were similar (P > 0.10) among all CS. This study demonstrated little calf growth performance and health benefits when feeding an BE and/or RC alone or in combination compared with calves fed Control.

A botanical extract (BE; garlic oil, anise oil, cinnamaldehyde, rosemary, and thyme blend) has been shown to enhance dry matter intake (DMI) and gut health, while eubiotics (EU; lactobacillus acidophilus fermentation product), has been shown to improve gut health and growth performance of growing Holstein calves. The hypothesis was the combination BE and EU could be synergistic to post-weaning neonatal calf growth performance. Seventy-seven (77) Holstein bull calves from a previous milk replacer trial were randomly assigned to 1 of 4 treatments using a 3 wk experimental period. Treatments were: 1) Control: Calf starter (CS) without BE or EU; 2) BE: CS with 275.6 g/ton of an experimental BE (Adisseo North America, Alpharetta, GA); 3) EU: CS with 0.22% EU (RumaCell DF 5G; Pacer Technology, Murtaugh, ID); and 4) BE&EU: CS with added BE and EU. The 22% crude protein CS was a mini-pellet and fed for ad-libitum consumption with amounts fed and orts recorded daily. Calves fed EU demonstrated greater (P < 0.05) body weight (BW; 81.3, 80.8, 84.8, and 84.2 kg for Control, BE, EU, and BE&EU, respectively) compared with calves fed Control and BE with calves fed BE&EU being intermediate and similar (P > 0.10). Calves fed BE demonstrated greater (P < 0.05) average daily gains (ADG; 965.5, 984.3, 1052.8 and 989.1 g/d) compared with calves fed Control with calves fed BE and BE&EU being intermediate and similar (P > 0.10). The DMI (2.19, 2.18, 2.31, and 2.14 kg/d) and feed conversions (0.45, 0.46, 0.45, and 0.45 kg BW gain/kg DMI) were similar (P > 0.10) among calves fed all treatments. Blood urea nitrogen concentrations (14.7, 14.6, 14.9, and 13.4 mg/dL) were similar (P > 0.10) among calves fed all treatments. Feeding a EU improved BW of weaned growing Holstein bull calves, but the BE and EU combination was not beneficial for enhancing growth performance.

Butyrate (UltraMix GF; Adisseo) is known to enhance ruminal papillae development for transitioning calves to dry feed. The hypothesis was that butyrate would be beneficial to neonatal calf growth performance. Eighty 2- to 5-d old Holstein bull calves were assigned to one of 2 treatments using a randomized complete block design. Treatments were: 1) control: no butyrate; or 2) butyrate: 0.3% butyrate added to milk replacer (MR). Calves were fed 2x/d at 0630 and 1800 h along with free choice water and a 22% CP mini-pelleted calf starter (CS). The MR was fed at 0.567 kg/d for d 1–14, then increased to 0.85 kg/d for d 15–42, and feeding reduced to 1x/d for d 42–49 with weaning occurring after the 49-d experimental period. Calves fed butyrate demonstrated greater (P < 0.04) ending body weight (BW; 54.7 and 56.2 kg, for control and butyrate, respectively), BW gain (29.0 and 31.7 kg), and average daily gains (ADG; 591.3 and 647.7 g/d), compared with calves fed control. Dry matter intake (DMI) was similar (P > 0.10) for both treatments, but the number of d required for calves to consume 0.9 kg CS for 3 consecutive days (47.3 and 45.7 d) was lower (P < 0.05) for calves fed butyrate compared with calves fed control. Feed conversions were improved (P < 0.05) for calves fed butyrate (0.53 and 0.58 kg/kg) compared with calves fed control. At the end of the 49-d study, withers height tended (P < 0.10) to be greater for calves fed butyrate (85.2 and 86.0 cm) compared with calves fed control, while the remaining frame measurements (hip height, hip width, body length, and heart girth) and fecal scores were similar (P > 0.10) for calves fed both treatments. Feeding neonatal calves butyrate in the MR improved growth performance and reduced the days to transition calves to CS.