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Prior work using a contractility bioassay determined that the serotonin (5-HT) receptor subtype 5-HT2A is present in bovine lateral saphenous veins and plays a role in ergot alkaloid (EA)-induced vascular contraction in steers grazing endophyte-infected (Epichloë coenophiala) tall fescue (Lolium arundinaceum). Ergot alkaloids have also been shown to be vasoactive in bovine gut vasculature. To determine what 5-HT receptors are involved in vasoconstriction of gut vasculature, contractility of ruminal and mesenteric arteries and veins collected from cattle was evaluated in the presence of agonists selective for 5-HT1B (CP 93129), 5-HT1D (L-694, 247), 5-HT2A (TCB-2), 5-HT2B (BW 723C86), 5-HT4 (BIMU-8), and 5-HT7 (LP 44) receptors. Segments of ruminal and mesenteric veins and arteries were collected and suspended in a multimyograph containing continuously oxygenated Krebs-Henseleit buffer. Blood vessels were exposed to increasing concentrations of 5-HT agonists every 15 min and contractile response data were normalized as a percentage of the maximum contractile response induced by 120 mM KCl. Analysis of variance was evaluated using mixed models procedure of SAS for effects of agonist concentration for each vessel type. Receptor agonists for 5-HT2B, 5-HT1D, and 5-HT7 did not induce a contractile response for ruminal or mesenteric vasculature (P > 0.05). However, when exposed to agonists for 5-HT2B or 5-HT1D, mesenteric veins relaxed below zero (P < 0.05). Exposure of all 4 blood vessel types to 5-HT2A agonist induced contractile responses (P < 0.05). The findings of this study indicate that 5-HT1D and 5-HT2B are present in mesenteric veins and may play a role in vasorelaxation. Further, 5-HT2A is present in ruminal and mesenteric vasculature, plays a role in vasoconstriction of these vessels, and could be influenced by EA exposure as has been demonstrated in peripheral blood vessels.

Organic, grassfed (OGF) dairy, which requires higher pasture and forage dry matter intake compared with standard organic dairy practices, is unique both in its management needs and in production challenges. The OGF dairy sector is rapidly growing, with the expansion of this industry outpacing other dairy sectors. There is a lack of research outlining OGF dairy production practices, producer-identified research needs or social factors that affect OGF systems. The objectives of this study were to, with a group of OGF dairy producers, (1) assess information regarding current production practices and producer knowledge, and (2) identify agronomic and social factors that may influence milk production on OGF farms across the United States. A mail survey, focused on demographics, forage and animal management, knowledge, and satisfaction of their farm, was developed and distributed in 2019, with 167 responses (47% response rate). The majority of producers indicated they belonged to the plain, or Amish-Mennonite, community. Milk production was greater on farms that had Holstein cattle, as compared to farms with Jerseys and mixed breeds, and employed intensive pasture rotation. Furthermore, most producers reported the use of supplements such as molasses and kelp meal, which can improve milk production, but also increase feed costs. Producers who indicated that they were at least satisfied with their milk production also reported high levels of knowledge of grazing management and cow reproductive performance. Comparison of response data from plain/non-plain respondents revealed that those that did not identify as plain were more likely to utilize certain government programs, had different priorities and utilized technology more frequently. Based on these results, more research exploring financial and production benchmarks, effective communication strategies to reach OGF producers and methods to improve cattle production through improved forage quality is needed.

Diet starch and fiber contents influence the rumen microbial profile and its fermentation products, yet no information exists about the effects of these dietary carbohydrate fractions on the metabolic activity of these microbes. The objective of this experiment was to evaluate the effects of dietary carbohydrate profile changes on the rumen meta-proteome profile. Eight cannulated Holstein cows were assigned to the study as part of a 4 × 4 Latin square design with a 2 × 2 factorial treatment arrangement including four 28-d periods. Cows received 1 of 4 dietary treatments on a dry matter (DM) basis. Diets included different concentrations of rumen fermentable starch (RFS) and physically effective undigested NDF (peuNDF240) content in the diet: (1) low peuNDF240, low RFS (LNLS); (2) high peuNDF240, low RFS (HNLS); (3) low peuNDF240, high RFS (LNHS); and (4) high peuNDF240, high RFS (HNHS). Rumen fluid samples were collected from each cow on the last 2 d of each period at 3 time points (0600, 1000, and 1400 h). The microbial protein fraction was isolated, isobarically labeled, and analyzed using liquid chromatography combined with tandem mass spectrometry techniques. Product ion spectra were searched using the SEQUEST search on Proteome Discoverer 2.4 (Thermo Scientific) against 71 curated microbe-specific databases. Data were analyzed using PROC MIXED procedure in SAS 9.4 (SAS Institute Inc.). A total of 138 proteins were characterized across 26 of the searched microbial species. In total, 46 proteins were affected by treatments across 17 of the searched microbial species. Of these 46 proteins, 28 were affected by RFS content across 13 microbial species, with 20 proteins having higher abundance with higher dietary RFS and 8 proteins having higher abundance with lower dietary RFS. The majority of these proteins have roles in energetics, carbon metabolism, and protein synthesis. Examples include pyruvate, phosphate dikinase (Ruminococcus albus SY3), 30S ribosomal protein S11 (Clostridium aminophilum), and methyl-coenzyme M reductase subunit α (Methanobrevibacter ruminantium strain 35063), which had higher abundances with higher dietary RFS. Conversely, glutamate dehydrogenase (Butyrivibrio fibrisolvens) and 50S ribosomal protein L5 (Pseudobutyrivibrio ruminis) and L15 (Ruminococcus bromii) had lower abundances with higher dietary RFS content. Among the remaining 18 proteins unaffected by RFS content alone, 5 proteins were affected by peuNDF240 content, and 13 were affected by peuNDF240 × RFS interactions. Our results suggest that the RFS content of the diet may have a greater influence on rumen microbial protein abundances than dietary peuNDF240 content or peu-NDF240 × RFS interactions. This research highlights that dietary carbohydrate profile changes can influence rumen microbial protein abundances. Further research is needed to fully characterize the effects of diet on the rumen meta-proteome and manipulate the various roles of rumen microbes. This will aid in designing the strategies to maximize the efficiency of ...

The aim of this study was to evaluate the effects of processed dietary supplements derived from two seaweeds, Saccharina latissima (SL) and Ascophyllum nodosum (AN), on microbial methane production and fermentation profile using in vitro methods. Four dual-flow continuous culture fermenters were utilized in a 4x4 Latin Square design to assess these 4 supplements: unwashed, coarsely milled SL (UNW), 3-min rinsed SL (3MR), 20-sec blanched SL (20SB), and a crude phlorotannin extract from AN (PHLT). Treatments were randomly assigned to fermenters and were top dressed on the total mixed ration (TMR) at 5% of total dry matter (DM). Four, 10-d experimental periods were conducted, consisting of a 7-d equilibration period followed by a 3-d sampling period. Vessel pH was continually measured, and effluent samples were collected for volatile fatty acid (VFA) analysis and calculation of DM, organic matter (OM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities. Methane was measured prior to the first AM and PM feedings during the 3-d sampling period. Data were analyzed using the PROC MIXED procedure of SAS (9.4) with fermenter as the random effect and period and treatment as fixed effects. Processed treatments (3MR= 7.86, 20SB= 5.75, PHLT= 10.46 mg/dL) yielded less methane (P &lt; 0.02) than unprocessed (UNW= 24.06 mg/dL). Apparent digestibilities of DM, OM, NDF and ADF were not affected by treatment. Total VFA (mM) was greater (P = 0.02) in 3MR than PHLT. The acetate to propionate ratio (A:P) was greater (P &lt; 0.01) in PHLT compared with 20SB, 3MR and UNW (5.62 vs 1.47, 1.27 and 1.54, respectively). Time spent below pH 5.8 during fermentation was not affected by treatment. These results indicate that seaweed processing method can affect methane production in vitro without negatively impacting rumen fermentation and should be further investigated using in vivo models.

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Grassfed dairy production systems often rely on alternative diet supplements such as apple cider vinegar (ACV) to improve productivity. The objectives of this study were to 1) compare rumen fermentative patterns resulting from diets consisting of forages harvested at mature and vegetative stages, and 2) evaluate the effects of ACV supplementation on fermentation metrics of vegetative forage mixtures using ruminal batch culture, performed as two different experiments. In each experiment, treatments were arranged as a randomized design with three periods per experiment. In experiment 1, 15 mL tubes were supplemented with 1.0 g DM of either vegetative 50% red clover + 50% orchardgrass (VEG) or mature 50% red clover + 50% orchardgrass (MAT). Tubes were inoculated with a 3:1 buffer: rumen fluid mixture (12 mL) and incubated at 39ºC under anerobic conditions for 48 h. In experiment 2, tubes received either 1.0 g DM VEG substrate only or 1.0 g DM VEG substrate + 0.125 mL ACV. Samples were collected at 0, 1, 2, 4, 6, 8, 12, 18, 24, and 48 h, pooled, and analyzed for carbohydrates (WSC), pH, in vitro DM disappearance (IVDMD), methane (CH4), and ammonia N (NH3-N). Data were analyzed using PROC GLIMMIX of SAS at P ≤ 0.05. The VEG treatment produced more CH4 than the MAT treatment (4.98 mg/ dL v. 2.87 mg/ dL; P &lt; 0.0001); however, CH4 from the VEG treatment was not affected by ACV. Tubes receiving VEG had greater WSC (2.39 mg/mL v. 1.56 mg/mL; P ≤ 0.05), IVDMD (81.7% v. 77.3%; P ≤ 0.05), and mean pH compared with those receiving MAT. Tubes receiving MAT had greater concentrations of NH3-N (P &lt; 0.01) compared with tubes receiving VEG. Fermentation metrics of VEG tubes were not affected by ACV; however, considerations need to be made for forage maturity.

The impact of using diverse forage mixtures on rumen performance is poorly characterized. The objective of this study was to evaluate the impact of feeding diverse pastures on rumen performance using in vitro continuous culture fermenters. Treatments were assessed using a 4 x 4 Latin square design. Each 10-d period included 7-d of adaption followed by 3-d of sample collection. Dietary treatments (DM basis) included 1) 50% orchardgrass + 50% alfalfa (OG-ALF); 2) 50% OG-ALF + 50% red clover (RC); 3) 50% OG-ALF + 50% pearl millet (MIL); and 4) 50% OG-ALF + 50% sorghum x sudangrass (SUD). Forage diets (131 g DM/ fermenter/ d) were divided into 4 portions/d (33%, 0600 h; 17%, 0720 h; 33%,1800 h; 17%, 1920 h). Fermenter pH measurements were collected every min for the entire experiment. Methane concentrations were measured using a gas probe and recorded twice daily (0530 h,1730 h) in triplicate on d 7, 8, 9, and 10. Daily total effluent samples were collected on d 8, 9, and 10 for VFA analysis. Results were analyzed using PROC MIXED of SAS. There were no differences in total VFA concentrations (P = 0.08), molar proportions (P = 0.22), or individual VFA ratios (P &gt; 0.05) as a result of treatment. Fermenter pH did not differ between fermenters as a result of treatment (P &gt; 0.05). Fermenters receiving OG-ALF had the greatest methane concentration (50.8 mg/dL), which was higher (P &lt; 0.05) than methane concentrations in fermenters receiving MIL (6.2 mg/dL), SUD (6.9 mg/dL), or RC (21.2 mg/dL). Methane concentrations from the MIL, SUD and RC treatments did not differ (P &gt; 0.05). This indicates that binary forage mixtures may have lower nutritional value compared with diverse mixtures, and this diversification could provide nutritional benefits.