This study’s objective was to determine the effects of increasing the dietary added zinc (Zn) on the milk production, milk somatic cell count (SCC), and immunoglobulin and antioxidant marker concentrations in the blood of dairy cows. Twelve Holstein cows (67 ± 2.5 days in milk) were assigned randomly to (1) a diet containing Zn–methionine at 76 mg/kg of DM (CTL) or (2) CTL top-dressed with about 21 mg/kg of DM extra Zn–methionine (+Zn) for 70 d. The concentrations of reduced (GSH) and oxidized (GSSG) glutathione, malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), and immunoglobulins in the blood were measured on d 0, 35, and 70. Compared to CTL, +Zn decreased the dry matter intake (DMI) throughout the trial and the milk yield (MY) during the first phase of feeding (0–35 d). It, however, increased the milk yield during the last phase (36–70 d). The +Zn tended to have lower and greater milk protein yields than CTL during the first and last feeding phases, respectively. The +Zn tended to decrease the SCC and was associated with lower plasma GSH: GSSG and lower serum SOD concentrations relative to CTL. The +Zn did not affect the immunoglobulins, MDA, or CAT. Despite the early DMI and MY reduction, the prolonged Zn–methionine supplementation at about 100 mg/kg of DM improved the milk yield, possibly as a result of the improved udder health of dairy cows.

The study objective was to assess the methane (CH₄)-mitigating potential (CH₄-MP) of an Asparagopsis taxiformis variety (Brominata) and evaluate its effects on cow health and milk food safety when fed at increasing dietary inclusion rates (IR) in dairy cows. This paper reports data on the CH₄-MP and production performance. In this study, 48 late-lactation cows (mean DIM = 386) blocked by parity were assigned randomly to receive 1 of 4 freeze-dried and pelletized Brominata IR treatments: 0% (CTL), 0.30% (standard IR [SIR]), 0.45% (SIR1.5), and 0.60% of DM (SIR2.0), with mean bromoform concentrations of 0, 17.4, 26.1, and 34.8 mg/kg of DM, respectively. The study consisted of a 10-d baseline measurement period (P1), a 4-wk IR ramp-up phase (P2), and a subsequent 9-wk response measurement period (P3). The pelletized Brominata was mixed uniformly into the TMR delivered daily to individual cows. The CH₄ emissions were measured daily using the GreenFeed system. Milk composition, BW, and body condition scores were recorded once every 2 wk. The feces samples were collected directly from the rectum every 8 h over 2 consecutive days during the last week of P3 to determine the apparent total-tract digestibility of nutrients. Orts were examined periodically during P3 to assess pellet refusals. Treatment effects were analyzed using the MIXED procedure of SAS with the REPEATED option. The model included fixed effects of IR, time (in weeks), the treatment × time interaction, parity, the covariate effect of P1 measurements, and the random effect of cow. The DMI decreased linearly with increasing IR. The DMI decreases of SIR1.5 (32.3%) and SIR2.0 (46.5%) were sustained throughout P3, whereas that of SIR became negligible after the fourth week of P3. The pellet refusals revealed sorting against Brominata pellets, resulting in 37% to 43% lower Brominata concentrations in ingested DM compared with the treatment IR. The mean CH₄ production decreased by 50%, 70%, and 77%, and CH₄ yield decreased by 42%, 55%, and 59% compared with the CTL in response to SIR, SIR1.5, and SIR2.0, respectively. The CH₄ yield reduction of SIR gradually decreased from the second week of P3 onward and became negligible in the last week, whereas SIR1.5 and SIR2.0 sustained it at 66% until the seventh week and then experienced a reduction to 36%. Consistently, the bromoform concentration (mg/g) in freeze-dried Brominata declined during P3, reaching a 23% reduction by the final 2 wk, primarily due to variability among harvested batches. Milk yield, milk component yields, and milk fat content decreased linearly with increasing Brominata IR. Compared with CTL, only SIR2 decreased those responses, except for milk fat yield, which was also decreased by SIR1.5. The nutrient digestibility had cubic relationships with IR, such that the DM, OM, and CP digestibility of SIR1.5 was lower than that of SIR but similar to that of CTL and SIR2.0. Overall, the results highlight that addressing the palatability issues and managing variability in bromoform concentration are essential in order to effectively mitigate enteric CH₄ emissions from dairy cows in late lactation, and possibly in other lactation stages, using Brominata.

This research reports ruminal and fecal microbiota composition of lactating dairy cows enrolled in a study aimed at investigating the effects of a fermentation extract derived from Bacillus licheniformis (BLFE), monensin (Rumensin^®; R), and their interactions on feed efficiency (FE, FE = milk yield/DMI). In a completely randomized design, 48 Holstein cows at 108 ± 35 days in milk were matched for parity and assigned to monensin (0 or 17.6 g/kg of DM) and BLFE (0 or 166 mg/kg of DM) in a 2 × 2 factorial arrangement. Treatments were fed daily for 63 d, including a 21 d adaptation period followed by a 42 d measurement period (P2). On d 38 and d 39 of P2, rumen-fluid (RF) and fecal samples were collected. DNA from RF and feces was sequenced using 16S rRNA gene-amplicon sequencing on an Illumina MiSeq platform. Fecal and RF volatile fatty acid (VFA) concentrations were analyzed, and propionate/acetate (P: A) was determined. The BLFE increased milk yield (3.3 kg/d) and FE (1.20 to 1.28), when fed alone rather than with monensin, while monensin increased energy-corrected milk yield (2.5 kg/d, p < 0.05), regardless of the BLFE in the diet. The BLFE tended to increase ruminal Firmicutes/Bacteroidetes (F: B) when fed alone, while alpha and beta diversities remained unmodified. The BLFE increased the abundances of Bifidobacterium (p = 0.02) and Erysipelotrichaceae_UCG-002 (p = 0.01) in RF, whereas monensin increased and decreased the abundances of Oscillospirales_ge (p = 0.02) and an unclassified Clostridia genus (p = 0.03), respectively. The monensin-suppressed Clostridia were negatively associated with ruminal P: A (r = −0.66; p < 0.01) and feed efficiency (r = −0.30; p = 0.04). The BLFE and monensin interactively affected several fecal genera (p < 0.05), but they had negligible or weak correlations with fecal P: A and FE. Overall, the results showed the ability of dietary supplementations of monensin and BLFE to increase milk production performance and FE by modulating ruminal rather than lower-gut microbiota composition, this is predominantly attributed to the ratio between the Firmicutes and Bacteroidetes abundances in lactating dairy cows.

The study objective was to investigate the impact of monensin and a fermentation extract derived from Bacillus licheniformis-derived fermentation extracts (BLFE) when fed alone or in combination on production performance and feed efficiency in lactating dairy cows. Sixty Holstein cows matched for DIM (108 ± 35; mean ± SD) and parity were assigned to 4 treatments formulated to provide 2 doses of monensin (0 and 17.6 mg/kg DM) and 2 doses of BLFE (0 and 166 mg/kg DM) in a 2 × 2 factorial arrangement. Monensin and BLFE doses were top-dressed on a TMR without added monensin. Cows were allowed to adapt to treatments for 21 d before measuring DMI, milk yield, milk composition, and BW responses to treatments over the next 42 d. Rumen fluid VFA, apparent total-tract digestibility (ATTD) of nutrients, and blood AA concentrations were determined in the last week. The effects of treatments were analyzed, accounting for baseline measurements, using mixed-effects models. Neither monensin nor BLFE modified DMI, which averaged 30.8 kg/d across treatments. At this DMI level, the actual monensin and BLFE doses consumed by cows were 14 and 145 mg/kg of DM, respectively. The BLFE fed alone increased milk yield:DMI (1.19 to 1.26) and NEL:DMI (1.60 to 1.83). It tended to increase milk yield and FCM and ECM yields, DMI and milk protein yields, and CP intake. Supplementing BLFE with monensin attenuated those responses. Monensin fed alone increased BW gain (0.44 kg/d) and tended to increase the component-corrected milk yield: DMI, but supplementing it with BLFE negated those effects. Regardless of the presence or absence of monensin in the diet, BLFE increased milk protein content (3.45% to 3.52%), while monensin enhanced milk fat yield (95 g/d) and component-corrected milk yields (4.7% to 5.1%). Milk fat improvements from monensin were significant in multiparous cows but negligible in primiparous cows. In contrast, the feed and protein efficiency enhancements of BLFE were more pronounced in primiparous than in multiparous cows. Supplementing BLFE did not modify ruminal or fecal VFA profiles when supplemented alone or with monensin. Monensin tended to decrease the molar percentage of butyrate in both rumen fluid and feces, while molar percentages of acetate, propionate, and their ratio remained unmodified. Supplementing BLFE or monensin alone did not affect ATTD of CP, but supplementing both together increased ATTD of CP compared with supplementing BLFE alone (59.2% to 62.1%). The BLFE supplementation alone increased blood EAA concentrations (18%), whereas adding monensin to the diet containing BLFE reversed that increase. The poor alignment between blood AA and ATTD in CP suggests potential effects of treatment on gut microbiota metabolism or postabsorptive AA clearance. Under current feeding conditions, data show that BLFE and monensin distinctly increased milk protein and fat, respectively, and each supplement improved feed efficiency when fed alone. The potential antagonism observed when fed together suggests the need for further research to investigate interactions between monensin and BLFE at varying doses under different feeding conditions.