A combination of Sanger and 454 sequences of small subunit rRNA loci were used to interrogate microbial diversity in the bovine rumen of 12 cows consuming a forage diet. Observed bacterial species ...richness, based on the V1-V3 region of the 16S rRNA gene, was between 1,903 to 2,432 species-level operational taxonomic units (OTUs) when 5,520 reads were sampled per animal. Eighty percent of species-level OTUs were dominated by members of the order Clostridiales, Bacteroidales, Erysipelotrichales and unclassified TM7. Abundance of Prevotella species varied widely among the 12 animals. Archaeal species richness, also based on 16S rRNA, was between 8 and 13 OTUs, representing 5 genera. The majority of archaeal OTUs (84%) found in this study were previously observed in public databases with only two new OTUs discovered. Observed rumen fungal species richness, based on the 18S rRNA gene, was between 21 and 40 OTUs with 98.4-99.9% of OTUs represented by more than one read, using Good's coverage. Examination of the fungal community identified numerous novel groups. Prevotella and Tannerella were overrepresented in the liquid fraction of the rumen while Butyrivibrio and Blautia were significantly overrepresented in the solid fraction of the rumen. No statistical difference was observed between the liquid and solid fractions in biodiversity of archaea and fungi. The survey of microbial communities and analysis of cross-domain correlations suggested there is a far greater extent of microbial diversity in the bovine rumen than previously appreciated, and that next generation sequencing technologies promise to reveal novel species, interactions and pathways that can be studied further in order to better understand how rumen microbial community structure and function affects ruminant feed efficiency, biofuel production, and environmental impact.
•Grazing-induced shifts in plant biomass and diversity may foretell changes in SOC.•Grazing treatments that boosted SOC did not boost plant biomass and richness.•Grazing treatments that boosted plant ...biomass and richness did not boost SOC.•Shifts in microbial functioning may instead drive grazing-induced SOC accrual.
A new aim for grassland management is to increase soil organic carbon (SOC) and to offset CO2 emissions by companies. This practice of carbon ranching may be informed by grazing-induced shifts in plant biomass and diversity which may foretell changes in SOC. Unfortunately, little is known about how grazing-induced shifts in plant properties correspond with shifts in SOC stocks. To help fill this gap, we used data from a field experiment to test whether above-ground plant properties (i.e. biomass, species richness) act as leading indicators of grazing-induced SOC accrual in the Northern Great Plains. The 5-yr bovine grazing experiment had a randomized complete block design and pre-treatment data. Moderate summer grazing (control) is widely used in the Northern Great Plains, and treatments that may alter grassland vegetation and SOC included: severe summer grazing, moderate fall grazing, and severe fall grazing. Severe fall and summer grazing increased SOC but had no effect on plant species richness and biomass relative to controls. Fall moderate grazing increased above-ground plant biomass but had no effect on SOC relative to controls. Changes to grazing practices can affect SOC without measurably affecting plant properties and can affect plant properties without measurably affecting SOC. While two drivers of SOC are plant carbon inputs and microbial respiration, our study indicates that grazing-induced change in above-ground vegetation is not predictive of change in SOC.
Abstract
Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of prenatal and postnatal ...melatonin supplementation on overall calf performance and dam milking traits in relation to calves, molecular factors involved in growth and metabolism of calves, along with testicular physiology and fertility traits in subsequent bulls. On days 190, 220 and 250 of gestation, dams (N = 60) were administered either two subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves were blocked based on prenatal treatment and sex. Calves received either melatonin implants (posMEL) or none (posCON) on days 0, 30, and 60 of age. On day 60 of lactation, a subset of dams (N = 32) were selected based on age, weight, and calf sex for milk collection and analysis. At weaning, (day 210 postnatally) calf weight, morphometric data, liver samples, and loin samples were collected. At 12 mo of age, bull (N = 30) scrotal circumference, scrotal temperature, and testicular artery measurements were recorded. Milk yield and fat percent from dams tended to decrease in the preMEL group (P < 0.07) compared with preCON group. Prenatal melatonin administration did not affect (P = 0.95) calf birth weight and similarly calf weaning weight was unaffected (P < 0.10) by prenatal or postnatal melatonin supplementation. Blood analysis demonstrated that plasma concentrations of melatonin were not different (P = 0.12) in dams; however, an increase (P < 0.001) in plasma concentrations of melatonin was observed in posMEL vs. posCON calves. A tendency (P < 0.10) for decreased MYF5 and MYOD1 expression in loin muscle was observed in the posMEL calves. Prenatal and postnatal melatonin administration did not affect subsequent bull scrotal measurements or testicular hemodynamics (P ≥ 0.14). Administering supplemental melatonin via implants during the prenatal and postnatal phase did not alter performance characteristics in offspring. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature might have attributed to a lack of differences in melatonin levels during the prenatal phase. In the postnatal period, the level of developmental plasticity appears to be too low for melatonin properties to be effective.
Winter maternal melatonin supplementation decreased subsequent dam milk yield without altering calf weaning weight. Furthermore, prenatal and postnatal exposure to supplemental melatonin did not affect measurements of bull performance.
Lay Summary
Previous studies have examined maternal melatonin implants in fall calving Mississippi cattle during the third trimester of pregnancy. These studies have shown increased maternal uterine blood flow without any change in calf birth weight when supplemented with melatonin implants. However, calf weaning weights were increased in calves born to melatonin supplemented dams vs. their control counterparts. The objective of this study was to examine offspring performance following maternal melatonin supplementation (prenatal) and/or postnatal calf melatonin supplementation in spring calving Montana cattle. Calf performance and weight at weaning were not affected by maternal or postnatal melatonin supplementation. However, dam milk yield and fat percent were decreased in the melatonin supplemented dams. Maternal and postnatal melatonin supplementation did not affect bull measurements of reproductive performance. Interestingly, maternal concentrations of melatonin were not different between dam treatment groups; however, postnatal melatonin supplementation increased calf concentrations of melatonin. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature may attribute to a lack of differences in melatonin levels during the prenatal phase.
Correctly assessing whether rangeland ecosystem services are stable, improving, or degrading is of global importance. Soil aggregate stability (SAS) is widely used to infer rangeland health, partly ...because high SAS is thought to reduce run‐off by increasing infiltration. We studied the sensitivity of SAS to grazing and other disturbances, the effects of SAS on infiltration, and the utility of alternative indicators of infiltration in the Northern Great Plains.
To test grazing effects on SAS, we compared SAS between paired areas that were lightly to moderately grazed or excluded from grazing for 6 years. Additionally, we compared SAS between grazed and not‐grazed plots of a 2‐year controlled grazing experiment with moderate and severe grazing. We also applied herbicide, mowing, and fungicide treatments to test SAS responses to disturbances more generally, as well as effects of SAS and other factors on infiltration. To more generally test for a SAS–infiltration relationship, we performed a meta‐analysis of our data combined with other data from the region.
Grazing often reduced stability of small macroaggregates (0.25–1 mm) in the controlled grazing experiment but not the paired grazing area experiment. Grazing had no detectible effect on SAS of larger macroaggregates (1–2 mm). Herbicide tended to reduce SAS, and mowing sometimes increased SAS. Infiltration exhibited high plot‐to‐plot variation and was not significantly affected by treatments. Variation in infiltration was best explained by plant community composition variables and was not explained by either SAS or other soil properties. Our meta‐analysis revealed no general SAS–infiltration relationship.
Synthesis and applications. Our findings counter prevailing expectations that soil aggregate stability (SAS) is consistently sensitive to rangeland disturbance(s) and a leading indicator of soil water transport. Plant community composition properties were better predictors of infiltration. Our findings support the theory that excessive grazing increases the prevalence of a grazing tolerant species, which was associated with low levels of infiltration irrespective of SAS.
Our findings counter prevailing expectations that soil aggregate stability (SAS) is consistently sensitive to rangeland disturbance(s) and a leading indicator of soil water transport. Plant community composition properties were better predictors of infiltration. Our findings support the theory that excessive grazing increases the prevalence of a grazing tolerant species, which was associated with low levels of infiltration irrespective of SAS.
While considerable research has quantified effects of grazing management and precipitation on plant communities, less is known about how seasonal effects influence extrusa diet quality selected by ...grazing ruminants. We tested effects of cattle grazing to two residual herbages (600 kg moderate or 300 kg low animal unit mo AUM/ha) and two grazing seasons (summer and fall) on 20 indicators of ruminant extrusa diet quality over a 6-yr period. We found no effect of residual herbage on 13 indicators of diet extrusa quality (P ≥ 0.13) and no effect of season on 4 indicators of extrusa diet quality (P ≥ 0.0773). We did, however, detect effects of yr on extrusa diet quality metrics and nutrients, likely due to variation in annual precipitation, which ranged from 63.9% to 138.6% of the long-term average. Most noticeably, the mineral Mn in extrusa was substantially lower in yrs with higher precipitation (P < 0.0001). While grazing intensity had divergent effects on forage quality in the summer versus fall, annual precipitation was often important. Crude protein was lowest in fall of 2013 (6.5%) and 2018 (7.78%), two high-precipitation yrs, but it was also low in fall of 2015 (7.30%), a low-precipitation yr (P < 0.0001). Forage extrusa Cu, an important catalyst in ruminant metabolism, exhibited a yr × season interaction. Copper in fall of 2018 was greater compared with all other yrs and seasons in the study (P < 0.0001), 35.7% greater than summer of 2018, a high-precipitation yr, and 82.9% and 43.5% greater than summer and fall of 2013, another high-precipitation yr. Seasonal variation in diet nutrients and quality indicators were complex and complicated by yr effects, which sometimes related to precipitation amounts.
Japanese brome (Bromus japonicus Thunb.) has been introduced to four continents from its Eurasian origins and has increased during recent decades, particularly in North America. Invasion of this C3 ...annual grass into rangelands diminishes native plant communities and hinders livestock performance. Control methods have been developed, but have proven short-lived. Japanese brome is positively correlated with plant litter and standing dead material, suggesting management of those components could be important. Objectives for this study were to isolate and quantify the effects of litter and standing dead on Japanese brome utilizing fall defoliation with four different mowing heights (10, 6, 4, or 1 cm) compared to a non-mowed control. Research was conducted on two ecological sites (silty and claypan) with each site consisting of 25 plots (5.5 × 1.6-m). This study was conducted over 4 yr (2013–2017) and fall mowing reduced old dead mass every year except 2016, which followed a severe drought. Spring soil water was not reduced by fall defoliation. Mowing to 1 cm reduced brome biomass by 40% compared to non-mowed plots and brome production was highly dependent on Sep-Oct precipitation. Brome biomass was least in 2015 during a drought and greatest in 2017 following double the median Sep-Oct precipitation. Non-brome biomass was similar across treatments. An 11% reduction in current-year biomass was observed for mowing heights of 10, 6, and 4 cm whereas a 22% reduction was measured for the 1 cm mowing height compared to non-mowed plots. Perennial grass basal cover was similar for 10, 6, and 4 cm mowing heights and greater than that for mowing at 1 cm whereas, no differences were detected between non-mowed plots and any mowing height. Increasing fall defoliation intensity reduced annual bromes while allowing perennial grasses to persist, indicating fall mowing and possibly grazing are viable options for annual brome management.
•Invasive bromes can be managed through fall defoliation.•Native perennial grasses persist with fall defoliation of bromes.•Heavy defoliation reduces current year primary production.
This study determined changes in plasma amino acid concentration in late-gestating (beginning 58 ± 1.02 days prior to calving), primiparous, winter-grazing range heifers receiving wheat ...middling-based supplement without (CON) or with rumen-protected methionine (MET) to provide 15 g
dl
-MET each day. Plasma was collected on days −2 and 0 (start of MET supplementation just prior to individually receiving supplement at 0700 hours). Plasma was sampled again on days 40, 42 and 44 prior to supplementation at 0700 and 1100 hours (4 h after receiving daily supplement). Data were analyzed with cow as the experimental unit. Continuous variables were analyzed by the main effects of treatment, date, or time and their interaction when appropriate. Comparable BW (
P
= 0.32) and BCS (
P
= 0.83) over the 44-day metabolism trial were found between both CON- and MET-fed heifers. MET-supplemented heifers had greater (
P
< 0.01) plasma concentrations of methionine indicating that the rumen-protection technology successfully delivered methionine to the small intestine. Supplementation with rumen-protected
dl
-MET caused a significant supplement × date interaction for glutamine (
P
= 0.03), glycine (
P
= 0.02), methionine (
P
< 0.01), and serine (
P
= 0.05). In addition, trends for supplement × date interactions were detected for leucine (
P
= 0.07), threonine (
P
= 0.09), valine (
P
= 0.08), total amino acids (TAA;
P
= 0.08), non essential amino acids (NEAA;
P
= 0.08), branched chain amino acids (BCAA;
P
= 0.08), and glucogenic amino acids (GLUCO;
P
= 0.08). These results suggest that the BCAA (leucine and valine) were utilized more efficiently with MET supplemented heifers compared to CON supplemented heifers. Plasma AA concentrations for glutamic acid (
P
< 0.01), histidine (
P
= 0.01), tyrosine (
P
< 0.01), and EAA (
P
< 0.01), all decreased throughout the study. These results further confirm methionine is a limiting amino acid in forage fed late-gestating heifers and further suggests the limitation when grazing dormant range forages as shown by improved utilization of other plasma amino acids when supplemental methionine was provided.
•Native species in ponderosa pine woodland are resistant to moderate grazing after summer wildfire.•Total herbaceous productivity is resistant to moderate grazing after summer wildfire.•Moderate ...grazing after summer wildfire reduced old dead material and increased richness.•Early growing season defoliation reduces non-native annual grasses.•Early growing season defoliation increases native diversity.
There remains a high level of ambiguity around post-fire grazing management. The Lodgepole Complex fire burned 109,346 ha in east-central Montana in July 2017, including areas previously burned in 2003 by the Bureau of Land Management for fuels mitigation. We hypothesized that herbaceous productivity and species composition in ponderosa pine woodlands are resistant to moderate grazing and timing of defoliation the first growing season after fire. Eight exclosures (25 × 15 m) were built, 4 on reburned area and 4 on wildfire area. To determine grazing effects, a 15 × 10 m sampling area in each exclosure was paired with a grazed section outside the exclosure. Additionally, four 5x10-m plots were established within each exclosure and were mowed to 10 cm in June, July, August, or not mowed to determine seasonal defoliation effects. Differences between grazed and nongrazed sites in 2019 were limited. There was a trend for less old dead biomass in grazed than nongrazed treatments. Species richness was greater on grazed sites than nongrazed or reburn sites. Native species richness was greater on grazed sites than nongrazed sites and reburn sites had an intermediate level of native species richness. Standing crop was reduced by defoliation, with current year and perennial grass biomass being unaffected. The reduction in standing crop was driven by less old dead biomass on defoliated plots. June defoliation reduced C3 grasses and increased C4 grasses, and June and July defoliation each reduced annual grasses. Simpson’s and native Simpson’s diversity were greater on defoliated plots. Results indicate ponderosa pine woodland is resilient to moderate post-fire grazing.
•Reliable results require good replication and detection of pre-existing variation.•Severe summer (or fall) grazing increased SOC accrual in US Northern Great Plains.•SOC accrual was negatively (not ...positively) associated with root biomass.•SOC accrual was positively associated with soil N and density.•Management heterogeneity is likely necessary to sustainably maximize SOC accrual.
Identifying grazing practices that maximize food production and soil carbon sequestration is of global importance. Currently, we cannot reliably predict which grazing practice will accrue the most soil organic carbon (SOC) partly because of confusion created by an abundance of low-quality experiments. Data quality has likely suffered because adequate treatment replication requires a lot of land, meaningful scale introduces heterogeneity among replicates, and pre-existing differences are often not taken into account. Here we tested the effects of five grazing treatments on SOC stocks with a gold standard randomized controlled trial (RCT) with pre-treatment data. Treatments were no grazing, severe summer grazing, moderate fall grazing, severe fall grazing, and the conventional approach for the system of moderate summer grazing. Because grazing experiments are often little-replicated, we also gauged the dependence of results on pre-treatment data by comparing the results of analyses with vs without pre-treatment data. We also tested for relationships between plant (root biomass, plant species composition) and soil properties (mass, nitrogen concentration) and SOC. After applying treatments for 5-yr, the no grazing and severe summer and fall grazing treatments accrued 0.85 to 1.22 kg × m−2 (0–60 cm soil depth) more SOC than conventional moderate summer grazing and represent appreciable (i.e. >4 per mille per yr) increases in SOC stocks. Furthermore, the entire portfolio of new grazing practices increased SOC accrual compared to conventional management. Given the divergent characteristics of the newly applied practices, sustainable accrual of SOC may depend on management heterogeneity. Accrual of SOC was likely driven by a reduction in SOC mineralization related to increased soil density and nitrogen, decreased root biomass, and change in plant species composition. Our findings counter the prevailing view that plant material inputs are the primary driver of SOC accrual in grazing lands. In other words, SOC accrual was mainly associated with indicators of decreased SOC mineralization (C outputs). We also found unique results for analyses with and without pre-treatment data, thereby indicating the risk of unreliable results for little-replicated RCTs without pre-treatment data. Robust generalizations on grazing practices that will reliably and sustainably maximize the rate of SOC accrual for a specific system, climate and timeline are still lacking, but further focus on factors affecting SOC mineralization will facilitate their development.
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