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This study aims to compare rumen microbiome and metabolites between second lactation dairy cows in the 75th percentile (n = 12; 57.2 ± 5.08 kg/d) of production according to genomic predicted transmitting ability for milk (GPTAM) and their counterparts in the 25th percentile (n = 12; 47.2 ± 8.61 kg/d). It was hypothesized that the metagenome and metabolome would differ between production levels. Cows were matched by days in milk (DIM), sire, occurrence of disease, and days open in previous lactation. For an additional comparison, the cows were also divided by phenotype into high (n = 6; 61.3 ± 2.8 kg/d), medium (n = 10; 55 ± 1.2 kg/d), and low (n = 8; 41.9 ± 5.6 kg/d) based on their milk production. Samples were collected 65 ± 14 DIM. Rumen content was collected using an oro-gastric tube and serum samples were collected from the coccygeal vessels. High-resolution liquid chromatography-mass spectrometry (LC-MS) was used for rumen and serum metabolite profiling. Shotgun metagenomics was used for rumen microbiome profiling. Microbiome sample richness and diversity were used to determine alpha and Bray-Curtis dissimilarity index was used to estimate beta diversity. Differences in metabolites were determined using t-tests or ANOVA. Pearson correlations were used to consider associations between serum metabolites and milk production. There was no evidence of a difference in rumen metabolites or microbial communities by GPTAM or phenotype. Cows in the phenotypic low group had greater serum acetate to propionate ratio and acetate proportion compared to the cows in the phenotypic medium group. Likewise, serum propionate proportion was greater in the medium compared to the low phenotypic group. Serum acetate, butyrate, and propionate concentrations had a weak positive correlation with milk production. When investigating associations between rumen environment and milk production, future studies must consider the impact of the ruminal epithelium absorption and post-absorption processes in relation to milk production., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Ravelo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The objective of this study was to evaluate the effect of increasing choline supplementation on the intake of milk replacer (MR) and calf starter (CS), growth performance, and fecal scores of calves over 8 wk. One hundred calves from commercial herds were transported to the University of Minnesota Southern Research and Outreach Center (SROC) calf facility randomized to one of 4 treatments differing in choline supplementation within MR including: 0 (C0; n = 24), 700 (C700; n = 26), 1,400 (C1400; n = 25), and 2,100 mg/kg choline (C2100; n = 25). Milk replacer contained a basal concentration of 1,650 mg/kg MR resulting in total choline concentrations in the MR of 1,650 mg/kg for C0, 2,350 mg/kg for C700, 3,050 mg/kg for C1400, and 3,750 mg/kg for C2100. Calves were weaned at 49 d, and the trial ended at 56 d. Body weight was measured at d 0, 14, 28, 42, 49, and 56. Fecal scores were measured weekly. Feed intake was measured daily and calculated every 2 wk. All feeding, BW measurements, and fecal scoring were conducted by the research staff at the University of Minnesota SROC. Growth, feed intake, and gain to feed ratio were analyzed using a linear mixed effects model with choline concentration as a fixed effect and source herd and room as random effects. Initial BW was included as a covariate for average daily gain. Fecal scores were analyzed as a chi-squared test of significance. Feeding 700 mg/kg supplemental choline increased MR intake throughout the preweaning period and increased ADG in both the preweaning and postweaning periods compared with the other treatments. No differences were observed for fecal scores across treatments. Results suggest that calf performance can be improved with MR containing 2,350 mg/kg choline, contrasting with current NASEM (2021) requirements of 1,000 mg/kg., (© 2024.)

The objective of this study was to evaluate the effects of dietary replacement of magnesium oxide (MgO) with calcium-magnesium hydroxide [CaMg(OH) 2 ] and its interaction with ruminal buffer (sodium sesquicarbonate) supplementation on production, Ca and Mg balance, and overall physiological response of mid-lactation Holstein dairy cows. Sixty cows averaging 40.5 ± 7.0 kg of milk/d were used. Treatments were assigned following a 2 × 2 factorial arrangement: (1) MgO, (2) MgO + buffer, (3) CaMg(OH) 2 , or (4) CaMg(OH) 2 + buffer. Diets were formulated to have 16.5% of crude protein, 1.82 Mcal/kg of net energy for lactation, 0.67% Ca, 0.39% P, and 0.25% Mg, all on a dry matter (DM) basis. Treatments were individually top dressed. Milk production, composition, and DM intake were evaluated. A subsample of 20 cows were randomly selected for the evaluation of Ca and Mg balance, blood gases, and electrolytes. Ruminal fluid was also collected for evaluation of pH and Ca and Mg solubility. Effects of Mg source, buffer, and the interaction Mg source × buffer were analyzed through orthogonal contrasts. An interaction of Mg source × buffer was found for DM intake and feed efficiency, in which cows fed CaMg(OH) 2 had a similar feed efficiency regardless of ruminal buffer inclusion; however, when cows were fed MgO, the inclusion of buffer reduced feed efficiency. No effects on body weight and milk yield were observed. Buffer addition tended to increase the concentrations of fat, protein, and solids-not-fat, without affecting the yields of these milk components. Magnesium source and buffer did not affect ruminal fluid, blood, urine, or fecal pH; however, buffer supplementation increased urinary pH. Treatment with CaMg(OH) 2 increased blood concentration of HCO 3 - , total CO 2 , and base excess compared with cows fed MgO. No differences were observed in the ruminal solubility of Ca and Mg or on milk or urinary Ca and Mg excretion. Greater plasma Mg concentration was observed for animals fed MgO compared with cows fed CaMg(OH) 2 ; however, both sources were above the threshold recommended in the literature for dairy cows. Also, a reduction in fecal Mg excretion was observed in animals fed CaMg(OH) 2 . In summary, we provide evidence that CaMg(OH) 2 could replace MgO without affecting performance, overall physiological response, or Ca and Mg balance of mid-lactating dairy Holstein cows., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

The objective of this study was to evaluate the effects of feeding sugars as a replacement for starch on the ruminal microbiome using a dual-flow continuous culture system. Four periods of 10 days each were conducted with 8 fermenters in a 4 × 4 replicated Latin square design. Treatments included: 1) control with corn-CON, 2) molasses-MOL, 3) untreated condensed whey permeate-CWP, and 4) CWP treated with a caustic agent-TCWP as a partial substitute for corn. Sugars were defined as the water-soluble carbohydrates (WSC) concentration. Diets were formulated by replacing 4% of the diet DM in the form of starch from corn with the sugars in byproducts. Microbial samples for DNA analysis were collected from the solid and liquid effluent containers at 3, 6, and 9 h after feeding. Bacterial community composition was analyzed with sequencing the V4 region of the 16S rRNA gene using Illumina MiSeq platform. Data were analyzed with R 4.1.3 packages vegan, lmer, and ggplot to determine the effects of treatment on the relative abundance of taxa in the solid and liquid fractions, as well as the correlation of Acetate: Propionate ratio and pH to taxa relative abundance. Treatments did not affect alpha or beta diversity. At the phylum level the relative abundance of Proteobacteria was increased in CON compared to sugars in the solid fraction. In the liquid fraction, Firmicutes had greater relative abundance in sugar treatments while Bacteroidota and Spirochaetota were present in lower relative abundance in CWP. For solid and liquid samples, the family Lachnospiraceae had greater relative abundance in sugar treatments compared to CON. The decreased relative abundance of Christensenellaceae and Rikenellaceae paired with the greater relative abundance of Selenomonadaceae in CWP could help explain greater propionate molar proportion and decreased ruminal pH previously observed for this treatment. The genera Olsenella a lactic acid-producing bacterium, had the greatest relative abundance in MOL. Incorporating TCWP or MOL as a partial replacement for starch was more conservative of fibrolytic bacterial taxa compared to CWP. Additionally, TCWP did not increase bacterial taxa associated with synthesis of lactate as compared to MOL. Overall, replacing starch with sugars is mostly conservative of the ruminal microbiome; however, changes observed coincide with differences observed in acetate and propionate proportions and ruminal pH., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Magnesium oxide (MgO) is one of the most used Mg supplements in livestock. However, to avoid relying upon only one Mg source, it is important to have alternative Mg sources. Therefore, the objective of this study was to evaluate the effects of the interaction of two Mg sources with buffer use on the ruminal microbiota composition, ruminal fermentation, and nutrient digestibility in lactating dairy cows. Twenty lactating Holstein cows were blocked by parity and days in milk into five blocks with four cows each, in a 2 × 2 factorial design. Within blocks, cows were assigned to one of four treatments: 1) MgO; 2) MgO + Na sesquicarbonate (MgO+); 3) calcium-magnesium hydroxide (CaMgOH); 4) CaMgOH + Na sesquicarbonate (CaMgOH+). For 60 d, cows were individually fed a corn silage-based diet, and treatments were top-dressed. Ruminal fluid was collected via an orogastric tube, for analyses of the microbiota composition, volatile fatty acids (VFA), lactate, and ammonia nitrogen (NH3-N). The microbiota composition was analyzed using V4/16S rRNA gene sequencing, and taxonomy was assigned using the Silva database. Statistical analysis was carried out following the procedures of block design analysis, where block and cow were considered random variables. Effects of Mg source, buffer, and the interaction between Mg Source × Buffer were analyzed through orthogonal contrasts. There was no interaction effect of the two factors evaluated. There was a greater concentration of NH3-N, lactate, and butyrate in the ruminal fluid of cows fed with CaMg(OH)2, regardless of the buffer use. The increase in these fermentation intermediates/ end-products can be explained by an increase in abundance of micro-organisms of the genus Prevotella, Lactobacillus, and Butyrivibrio, which are micro-organisms mainly responsible for proteolysis, lactate-production, and butyrate-production in the rumen, respectively. Also, dietary buffer use did not affect the ruminal fermentation metabolites and pH; however, an improvement of the apparent total tract digestibility of dry matter (DM), organic matter (OM), neutral fiber detergent (NDF), and acid fiber detergent (ADF) were found for animals fed with dietary buffer. In summary, there was no interaction effect of buffer use and Mg source, whereas buffer improved total tract apparent digestibility of DM and OM through an increase in NDF and ADF digestibility and CaMg(OH)2 increased ruminal concentration of butyrate and abundance of butyrate-producing bacteria., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

This study aimed to evaluate the effects of Saccharomyces cerevisiae and Megasphaera elsdenii as direct fed microbials (DFM) in beef cattle finishing diets to alleviate acute ruminal lactic acidosis in vitro. A dual-flow continuous culture system was used. Treatments were a Control, no DFM; YM1, S. cerevisiae and M. elsdenii strain 1; YM2, S. cerevisiae and M. elsdenii strain 2; and YMM, S. cerevisiae and half of the doses of M. elsdenii strain 1 and strain 2. Each DFM dose had a concentration of 1 × 10 8  CFU/mL. Four experimental periods lasted 11 days each. For the non-acidotic days (day 1-8), diet contained 50:50 forage to concentrate ratio. For the challenge days (day 9-11), diet contained 10:90 forage to concentrate ratio. Acute ruminal acidosis was successfully established. No differences in pH, D-, L-, or total lactate were observed among treatments. Propionic acid increased in treatments containing DFM. For N metabolism, the YMM treatment decreased protein degradation and microbial protein synthesis. No treatment effects were observed on NH 3 -N concentration; however, efficiency of N utilization by ruminal bacteria was greater than 80% during the challenge period and NH 3 -N concentration was reduced to approximately 2 mg/dL as the challenge progressed., (© 2022. The Author(s).)

Carbohydrates are one of the three macronutrients that provides energy in diets and are classified by their structures. Starch is a nonstructural carbohydrate and polysaccharide made of glucose monomers used for storage in plant cells. When starch makes up greater than 30% of the DM in diets there can be adverse effects on NDF digestibility due to decreases in ruminal pH. Sugars are water soluble carbohydrates that consist of monosaccharide and disaccharide units. Sugars ferment faster than starch because microorganisms in the rumen can ferment carbohydrates at different rates depending on their structure; however, this has not been shown to have negative effects on the ruminal pH. Sources of sugars such as molasses (sucrose) or whey (lactose) can be included in the diet as a partial replacement for starch in dairy cow diets. The purpose of replacing starch with sugars in a diet would be to add differing sources of carbohydrates in the diet to allow for continual fermentation of carbohydrates by the microorganisms in the rumen. It has been seen in studies and previous literature that the partial replacement of starch with sugars has the potential to maintain the ruminal environment and milk yield and composition in dairy cows without reducing NDF digestibility. The objective of this review is to evaluate the effects of partially replacing starch with sugars in dairy diets and its implication on ruminal fermentation, nutrient utilization, milk production, and feeding replacement strategy., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Corn is a feedstuff commonly fed to dairy cows as a source of energy. The objective of this study was to evaluate whether partially replacing dietary corn with molasses or condensed whey permeate, in lactating dairy cow diets in a dual-flow continuous culture system, can maintain nutrient digestibility by ruminal microorganisms. Furthermore, this study evaluated whether treating condensed whey permeate before feeding could aid the fermentation of the condensed whey permeate in the rumen. Eight fermentors were used in a 4 × 4 replicated Latin square with 4 periods of 10 d each. The control diet (CON) was formulated with corn grain, and the other diets were formulated by replacing corn grain with either sugarcane molasses (MOL), condensed whey permeate (CWP), or treated condensed whey permeate (TCWP). Diets were formulated by replacing 4% of the diet dry matter (DM) in the form of starch from corn with sugars from the byproducts. Sugars were defined as water-soluble carbohydrates (WSC) in the rations. The fermentors were fed 52 g of DM twice daily of diets containing 17% crude protein, 28% neutral detergent fiber, and 45% nonfiber carbohydrates. Liquid treatments were pipetted into each fermentor. After 7 d of adaptation, samples were collected for analyses of volatile fatty acids (VFA), lactate, and ammonia, and fermentors' pH were measured at time points after the morning feeding for 3 d. Pooled samples from effluent containers were collected for similar analyses, nutrient flow, and N metabolism. Data were statistically analyzed using Proc MIXED of SAS version 9.4 (SAS Institute Inc.); fixed effects included treatment and time, and random effects included fermentor, period, and square. The interaction of treatment and time was included for the kinetics samples. The TCWP and MOL treatments maintained greater fermentor pH compared with CWP. Total VFA concentration was increased in CWP compared with MOL. The acetate:propionate ratio was increased in TCWP compared with CON, due to tendencies of increased acetate molar proportion and decreased propionate molar proportion in TCWP. Lactate concentration was increased in MOL. Digestibility of WSC was increased in the diets that replaced corn with byproducts. The partial replacement of 4% of DM from corn starch with the sugars in byproducts had minimal effects on ruminal microbial fermentation and increased pH. Treated CWP had similar effects to molasses., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

The objective of this study was to examine the enzyme activities of an enzymatic complex produced by Pleurotus ostreatus in different pH and the effects of adding increased application rates of this enzymatic complex on the fermentation profile, chemical composition, and in situ ruminal disappearance of whole-plant corn silage (WPCS) at the onset of fermentation and 30 d after ensiling. The lignocellulolytic enzymatic complex was obtained through in vitro cultivation of P. ostreatus. In the first experiment, the activities of laccase, lignin peroxidase (LiP), manganese peroxidase, endo- and exo-glucanase, xylanase, and mannanase were determined at pH 3, 4, 5, and 6. In the second experiment, five application rates of enzymatic complex were tested in a randomized complete block design (0, 9, 18, 27, and 36 mg of lignocellulosic enzymes/kg of fresh whole-plant corn [WPC], corresponding to 0, 0.587, 1.156, 1.734, and 2.312 g of enzymatic complex/kg of fresh WPC, respectively). There were four replicates per treatment (vacuum-sealed bags) per opening time. Bags were opened 1, 2, 3, and 7 d after ensiling (onset of fermentation period) and 30 d after ensiling to evaluate the fermentation profile, chemical composition, and in situ dry matter and neutral fiber detergent disappearance of WPCS. Laccase had the greatest activity at pH 5 (P < 0.01), whereas manganese peroxidase and LiP had the greatest activity at pH 4 (P < 0.01; P < 0.01). There was no effect of the rate of application of enzymatic complex, at the onset of fermentation, on the fermentation profile (P > 0.21), and chemical composition (P > 0.36). The concentration of water-soluble carbohydrate quadratically decreased (P < 0.01) over the ensiling time at the onset of fermentation, leading to a quadratic increase of lactic acid (P = 0.02) and a linear increase of acetic acid (P = 0.02) throughout fermentation. Consequently, pH quadratically decreased (P < 0.01). Lignin concentration linearly decreased (P = 0.04) with the enzymatic complex application rates at 30 d of storage; however, other nutrients and fermentation profiles did not change (P > 0.11) with the enzymatic complex application rates. Addition of lignocellulolytic enzymatic complex from P. ostreatus cultivation to WPC at ensiling decreased WPCS lignin concentration 30 d after ensiling; however, it was not sufficient to improve in situ disappearance of fiber and dry matter., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)