Response of microbial communities to the changes in grazing intensity and season in a typical steppe.

Livestock grazing is an influencing factor playing a key role in shaping the plant community, microbial community, and soil properties in grassland ecosystems. Northern China's Loess Plateau has been used for livestock grazing for centuries and is a vulnerable ecosystem. In this study, the fates of bacterial and fungal communities of the typical steppe of the Loess Plateau were investigated under increasing grazing intensities practiced in summer and winter seasons. The results revealed changes in soil physiochemical properties, plant community properties, and microbial diversity in response to alterations in the grazing intensity. The alpha diversity of microbial communities (including bacteria and fungi) exhibited an uneven trend during summer grazing due to an increase in grazing intensity, but it decreased during winter grazing; however, the observed changes were not significant. The beta diversity of the bacterial community was highly influenced by grazing intensity, the summer community clustered near nongrazing, and the winter community presented significantly different results. The beta diversity of the fungal community was not influenced by grazing intensity or season. Grazing induced the growth of fast-growing bacteria (such as Actinobacteria and Firmicutes) and saprophytic fungi and a reduction in overall pathogenic traits. Co-occurrence network analysis and a structural equation model revealed changes in soil and plant properties (such as soil nitrogen level, soil organic carbon level, aboveground biomass, and litter biomass), with an increase in grazing intensity contributing to alterations in bacterial and fungal diversities. This finding demonstrates that grazing intensity can directly affect soil microbes and play an indirect role by modifying soil nutrients and reducing plant biomass, which eventually contributes to changes in microbial communities. Overall, implementing low grazing intensity is suggested for maintaining the microbial community structure the same as that of the native microbiome (ungrazed) in the steppe ecosystems.

Concurrent and legacy effects of sheep trampling on soil organic carbon stocks in a typical steppe, China.

Grazing plays a key role in ecosystem biogeochemistry, particularly soil carbon (C) pools. The non-trophic interactions between herbivores and soil processes through herbivore trampling have recently attracted extensive attention. However, their concurrent and legacy effects on the ecosystem properties and processes are still not clear, due to their effects being hard to separate via field experiments. In this study, we conducted a 2-year simulated-sheep-trampling experiment with four trampling intensity treatments (i.e., T0, T40, T80, and T120 for 0, 40, 80, and 120 hoofprints m-2, respectively) in a typical steppe to explore the concurrent and legacy effects of trampling on grassland ecosystem properties and processing. In 2017 (trampling treatment year), we found that trampling decreased aboveground biomass (AGB) of plant community and community-weighted mean shoot C concentration (CWM C), soil available nitrogen (N) and available phosphorus (P), but did not affect plant species diversity and belowground biomass (BGB). We show that compared with T0, trampling increased soil bulk density (BD) at T80, and decreased soil organic carbon (SOC) stocks. After the cessation of trampling for two years (i.e., in 2019), previous trampling increased plant diversity and BGB, reaching the highest values at T80, but decreased soil available N and available P. Compared with T0, previous trampling significantly increased soil BD at T120, while significantly decreased CWM C at T80 and T120, and reduced SOC stocks at T80. Compared with 2017, the trampling negative legacy effects amplified at T80 but weakened at T40 and T120. We also show that trampling-induced decreases in soil available N, AGB of Fabaceae and CWM C were the main predictors of decreasing SOC stocks in 2017, while previous trampling-induced legacy effects on soil available P, AGB of Poaceae and CWM C contributed to the variations of SOC stocks in 2019. Taken together, short-term trampling with low intensity could maintain most plant functions, while previous trampling with low intensity was beneficial to most plant and soil functions. The results of this study show that T40 caused by sheep managed at a stocking rate of 2.7 sheep ha-1 is most suitable for grassland adaptive management in the typical steppe. The ecosystem functions can be maintained under a high stocking rate through the process of providing enough time to rebuild sufficient vegetation cover and restore soil through measures such as regional rotational grazing and seasonal grazing.

Seeding alpine grasses in low altitude region increases global warming potential during early seedling growth.

Introduction of alpine grasses to low altitude regions has long been a crucial strategy for enriching germplasm diversity, cultivating and acclimating high-quality species, enhancing ecosystem resilience and adaptability, as well as facilitating ecosystem restoration. However, there is an urgent need to investigate the impacts of planting Gramineae seeds on greenhouse gas (GHG) emissions, particularly during the critical stage of early plant growth. In this study, four species of grass seeds (Stipa breviflora, Poa pratensis, Achnatherum splendens, Elymus nutans) were collected from 19 high-altitude regions surrounding the Qinghai-Tibet Plateau and sown at low-altitude. Measurements of GHG emissions at early seedling growth in the mesocosm experiment using static chamber method showed a strong increase in the cumulative emissions of CO2 (5.71%-9.19%) and N2O (11.36%-13.64%) (p < 0.05), as well as an elevated CH4 uptake (2.75%-5.50%) in sites where the four grass species were introduced, compared to bare soil. Consequently, there was a substantial rise in global warming potential (13.87%-16.33%) (p < 0.05) at grass-introduced sites. Redundancy analysis showed that seed traits, plant biomass, and seedling emergence percentage were the main driving biotic factors of three GHGs fluxes. Our study unveils the potential risk of escalating GHG emissions induced by introducing high altitude grasses to low altitude bare soil, elucidating the mechanism through linking seed traits with seedling establishment and environmental feedback. Furthermore, this offers a new perspective for assessing the impact of grass introduction on ecological environment of introduced site.

Metagenomic Profiles of Yak and Cattle Manure Resistomes in Different Feeding Patterns before and after Composting.

Antibiotic resistance is a global threat to public health, with antibiotic resistance genes (ARGs) being one of the emerging contaminants; furthermore, animal manure is an important reservoir of biocide resistance genes (BRGs) and metal resistance genes (MRGs). However, few studies have reported differences in the abundance and diversity of BRGs and MRGs between different types of animal manure and the changes in BRGs and MRGs before and after composting. This study employed a metagenomics-based approach to investigate ARGs, BRGs, MRGs, and mobile genetic elements (MGEs) of yak and cattle manure before and after composting under grazing and intensive feeding patterns. The total abundances of ARGs, clinical ARGs, BRGs, MRGs, and MGEs were lower in the manure of grazing livestock than in the manure of the intensively fed group. After composting, the total abundances of ARGs, clinical ARGs, and MGEs in intensively fed livestock manure decreased, whereas those of ARGs, clinical ARGs, MRGs, and MGEs increased in grazing livestock manure. The synergy between MGEs mediated horizontal gene transfer and vertical gene transmission via host bacteria proliferation, which was the main driver that altered the abundance and diversity of ARGs, BRGs, and MRGs in livestock manure and compost. Additionally, tetQ, IS91, mdtF, and fabK were potential indicators for estimating the total abundance of clinical ARGs, BRGs, MRGs, and MGEs in livestock manure and compost. These findings suggest that grazing livestock manure can be directly discharged into the fields, whereas intensively fed livestock manure should be composted before returning to the field. IMPORTANCE The recent increase in the prevalence of antibiotic resistance genes (ARGs), biocide resistance genes (BRGs), and metal resistance genes (MRGs) in livestock manure poses risks to human health. Composting is known to be a promising technology for reducing the abundance of resistance genes. This study investigated the differences and changes in the abundances of ARGs, BRGs, and MRGs between yak and cattle manure under grazing and intensive feeding patterns before and after composting. The results indicate that the feeding pattern significantly affected the abundances of resistance genes in livestock manure. Manure in intensive farming should be composted before being discharged into the field, while grazing livestock manure is not suitable for composting due to an increased number of resistance genes.

Nitrogen mineralization in grazed BSC subsoil is mediated by itself and vegetation in the Loess Plateau, China.

Biological soil crust (BSC) exists widely in many kinds of grassland, its effect on soil mineralization in grazing systems has well been studied, but the impacts and threshold of grazing intensity on BSC have rarely been reported. This study focused on the dynamics of nitrogen mineralization rate in biocrust subsoils affected by grazing intensity. We studied the changes in BSC subsoil physicochemical properties and nitrogen mineralization rates under four sheep grazing intensities (i.e., 0, 2.67, 5.33, and 8.67 sheep ha-1) in seasons of spring (May-early July), summer (July-early September), and autumn (September-November). Although this moderate grazing intensity contributes to the growth and recovery of BSCs, we found that moss was more vulnerable to trampling than lichen, which means the physicochemical properties of the moss subsoil are more intense. Changes in soil physicochemical properties and nitrogen mineralization rates were significantly higher under 2.67-5.33 sheep ha-1 than other grazing intensities (Saturation phase). In addition, the structural equation model (SEM) showed that the main response path was grazing, which affected subsoil physicochemical properties through the joint mediation of BSC (25%) and vegetation (14%). Then, the further positive effect on nitrogen mineralization rate and the influence of seasonal fluctuations on the system was fully considered. We found that solar radiation and precipitation all had significant promoting effects on soil nitrogen mineralization rates, the overall seasonal fluctuation has a direct effect of 18% on the rate of nitrogen mineralization. This study revealed the effects of grazing on BSC and the results may enable a better statistical quantification of BSC functions and provide a theoretical basis to formulate grazing strategies in the grazing system of sheep in Loess Plateau even worldwide (BSC symbiosis).

Effects of grazing and precipitation addition induced by functional groups on the relationship between aboveground biomass and species richness of a typical steppe.

Several studies have explored the influence of grazing or precipitation addition (PA), two important components of human activities and global climate change on the structure and function of communities. However, the response of communities to a combination of grazing and PA remains largely unexplored. We investigated the impact of grazing and PA on the relationship between aboveground biomass (AGB) and species richness (SR) of communities in three-year field experiments conducted in a typical steppe in the Loess Plateau, using a split-plot design with grazing as the main-plot factor and PA as the split-plot factor. AGB and SR have response threshold value to PA, which was decreased by grazing for AGB, but increased for SR. This indicates that implementing grazing management strategies is conducive to strengthening the protection of biodiversity in arid and semi-arid grasslands. Grazing promoted the AGB-SR coupling of the community by increasing the SR of medium drought tolerance (MD), low drought tolerance, and grazing tolerant functional groups. Grazing also accelerated the AGB-SR decoupling of the community by changing the AGB of high drought tolerance, MD, high grazing tolerance, and medium grazing tolerance functional groups. PA mediated changes in MD and SR of both drought and grazing tolerant functional groups and AGB of low grazing tolerance promoted the coupling of AGB-SR of the community. The Two-dimension functional groups classification method reflects the changes of AGB and SR in communities more reasonable than the division of single-factor functional groups.

Long-term grazing improved soil chemical properties and benefited community traits under climatic influence in an alpine typical steppe.

Grazing and climate change both contribute to diversity loss and productivity fluctuations. Sensitive climate conditions and long-term grazing activities have a profound influence on community change, particularly in high-altitude mountain grassland ecosystems. However, knowledge about the role of long-term continuous grazing management on diversity, productivity and the regulation mechanisms in fragile grassland ecosystems is still rudimentary. We conducted a long-term grazing experiment on an alpine typical steppe in the Qilian Mountains to assess effects of grazing intensity on soil, diversity, productivity and the regulation mechanisms. Plants and soil were sampled along grazing gradients at different distances from the pasture entrance (0, 0.3, 0.6, 0.9, 1.2 and 1.5 km) under the non-growing (WP) and the growing season grazing pasture (SAP). The results revealed that community diversity and biomass did not change significantly on a time scale, while the concentration of soil organic carbon and total phosphorus increased significantly. Heavy grazing (0-0.3 km) decreased community diversity and biomass. Grazing increased soil chemical properties in heavy grazed areas of WP, while the opposite was recorded in SAP. Soil chemical properties explained the largest variances in community diversity and community biomass. The prediction model indicates that grazing in WP mainly affects community diversity through soil chemical properties, and promotes a positive correlation between community diversity and community biomass; in SAP, the direct effect of grazing gradients on community diversity and biomass is the main pathway, but not eliminating the single positive relationship between diversity and biomass, which means that diversity can still be used as a potential resource to promote productivity improvement. Therefore, we should focus on the regulation of soil chemical properties in WP, such as the health and quality of soil, strengthening its ability to store water, sequester carbon and increase nutrients; focus on the management of livestock in SAP, including providing fertilizer and sowing to increase diversity and production in heavily grazed regions and reducing grazing pressure through regional rotational grazing. Ultimately, we call for strengthening the stability and sustainability of ecosystems through targeted and active human intervention in ecologically sensitive areas to cope with future grazing pressures and climate disturbances.

Microecosystem of yak rumen on the Qinghai-Tibetan Plateau is stable and is unaffected by soil or grass microbiota.

The rumen of livestock grazing on the Qinghai-Tibetan Plateau (QTP) acts as a transfer station for the circulation of soil, grass, faecal mineral elements and nutrients. Whether the microorganisms from the soil and grass could circulate through livestock rumen and excreted faeces. We studied the structural composition and interactive networks of microbiomes (bacteria and fungi) in soil, grass, and grazing yaks (rumen and faeces) on the QTP by using 16S rRNA gene and internally transcribed spacer (ITS) sequencing technology and to calculate the contribution rate of microorganisms from one habitat to another habitat using SourceTracker analysis. The meta-co-occurrence network revealed that soil, grass, rumen, and faeces comprise four independent habitats. The bacterial and fungal composition was significantly different in these four habitats. Soil microbiota showed the highest alpha diversity and microbial network complexity. Rumen microbiota demonstrated the highest microbial network stability and synergy, while grass endophytes showed the lowest microbial network complexity, stability, and synergy. According to the SourceTracker model, grass contributes 0.02% to the rumen microbes of yaks, while soil microorganisms do not circulate in the rumen. The soil and grass microbiota originating from faeces were 4.5% and 1.2%, respectively. The contribution of soil to grass was found to be 1.1%. Overall, the rumen microbiota of yaks is relatively stable and is only minimally influenced by the microbiota inhabiting the environment under natural grazing conditions. However, the contribution of yaks to soil and grass microbiota is relatively high when compared with the contribution of soil and grass to yaks microbiota.

Trace elements apportionment in forage, soil, and livestock in rangeland ecosystems along climatic gradients.

BACKGROUND: Alpine meadows, typical steppes, and deserts are among the globally important rangeland types that are generally distributed along temperature and precipitation gradients. Mineral losses caused by grazing are one of the key factors that can lead to instability or even degradation of these rangeland ecosystems. METHODS: We examined the concentrations of Cu, Fe, Mn, and Zn in soil, forage, and livestock dungs from diverse rangeland types in northwest China, to determine the relationships between these trace elements (TEs) concentrations and climatic factors (i.e., temperature, precipitation, and humidity), and to evaluate the potential risks of TEs deficiencies or excesses in these rangeland ecosystems. RESULTS: Forage Zn concentrations in forage of all three types of rangeland, and Cu concentrations in forage of the alpine meadow did not meet the growth requirements of grazing livestock. Concentrations of Cu, Fe, and Mn in forage and Fe, Mn, and Zn in livestock dungs had quadratic parabola relationships with temperature, precipitation, and humidity, but the relationships between climate factors and Cu, Fe, and Mn concentrations in soil were not significant. In addition, the abilities of the plant to absorb Cu, Fe, and Zn from soil were stronger in the typical steppe than that in the alpine meadows and desert. Also, the abilities of livestock to return TEs to soil were stronger in the alpine meadow than that in the typical steppe and desert. CONCLUSION: We derived a conceptual mode that the ratio of TE concentrations of the plant to soil and of livestock dung to forage represents the abilities of plants to absorb TEs from the soil matrix and livestock to return TEs to soil or to absorb TEs from forage, respectively. Results indicate potentially more serious risks of TEs deficiencies, especially that of Zn than previously considered in typical steppes and desert rangelands.

Litter manipulation enhances plant community heterogeneity via distinct mechanisms: The role of distribution patterns of plant functional composition and niche breadth variability.

Plant litter can greatly alter community compositional dynamics and variability of intraspecific interactions in grasslands, and thus the overall ecosystem structure and functions. However, whether plant activity can be driven by plant litter to modify plant community heterogeneity remains poorly explored. We investigate the responses of plant community heterogeneity to litter addition as well as their associated mechanisms. Here we conducted a three-year field experiment in a Tibetan alpine meadow to explore the effects of multiple plant litter addition (five mass levels and three species) on plant communities. We found that the effect of litter manipulation on plant community heterogeneity was mainly driven by litter mass rather than litter species. Higher litter mass manipulation significantly enhanced plant community heterogeneity, which was mainly determined by the niche breadth of forbs and the distribution patterns of functional composition rather than plant diversity. Our findings provide significant insights for understanding the effects of plant litter on grassland ecosystem dynamics to maintain the structure and function of ecosystems. Furthermore, this study suggests that reasonable management practices (e.g., moderate grazing in non-growing seasons) may be pivotal in achieving sustainability of grassland systems through plant litter dynamics.

Ecological thresholds of toxic plants for sheep production and ecosystem multifunctionality and their trade-off in an alpine meadow.

Toxic plants are a natural component of alpine meadow which co-evolved with Tibetan sheep for thousands of years. One challenge for indigenous herders is to know the ecological thresholds of toxic plants and maintain their vital functions in ways that are compatible with economic income and ecological conservation. To achieve this, field trials with Tibetan sheep grazing in alpine meadow were conducted to examine the ecological thresholds of toxic plants for sheep production and ecosystem functions and their trade-offs. Our results demonstrated that the changing point values of biomass proportion of toxic plants for dry matter intake and liveweight gain of sheep were 17% and 22%, respectively. The changing point value of biomass (richness) proportion of toxic plants for soil carbon accumulation index was 31% (59%), for soil nutrient cycling index was 38% (42%), and for ecosystem multifunctionality index was 28% (50%). The trade-off between liveweight gain of sheep and ecosystem multifunctionality first decreased and then increased along the gradient of biomass proportion of toxic plants (the value of changing point was 37%), and had a significant negative correlation with richness of toxic plants. In addition, structural equation modeling indicated that toxic plants can affect the trade-off between liveweight gain of sheep and ecosystem multifunctionality though increasing acid detergent fiber of plant and decreasing plant species richness, belowground biomass and soil total phosphorus. Consequently, opinions towards toxic plants should shift from the conventional view that they are serious threat to grassland ecosystem health to an inclusive understanding that they are beneficial to livestock and ecosystem functions under certain ecological thresholds.

Selenium supplementation improves nutrient intake and digestibility, and mitigates CH4 emissions from sheep grazed on the mixed pasture of alfalfa and tall fescue.

Low selenium (Se) in soil and forage can adversely affect on the quality of animal-derived foods, and hence on human health. Lambs grazed on mixed pastures of alfalfa (Medicago sativa) and tall fescue (Festuca arundinacea) were supplemented with five levels of Se [0, 3, 6, 9 and 12 µg/kg body weight (BW)]. The intake of dry matter (DM) and organic matter (OM) varied with the level of Se supplementation, with a peak at 6 µg Se per kg BW (p ≤ 0.05). Gross energy (GE) intake, digestive energy (DE) intake and metabolic energy (ME) intake were higher at 6 µg Se per kg BW than at other Se levels (p < 0.01); in addition, methane energy (CH4 -E) output was lower at 6 µg Se per kg BW. Supplementation with Se significantly increased nitrogen (N) intake, faecal N and urine N, for which the peak values were 20.2 g N/, 5.62 g N/day and 7.92 g N/day, respectively, at 6 µg Se per kg BW. Se intake, blood Se, faecal Se, urine Se and retained Se were negatively correlated with forage crude protein (CP) content (p < 0.001) but were positively correlated with the content of neutral detergent fibre (NDF) (p < 0.001) and acid detergent fibre (ADF) (p < 0.001). Thus, we recommend the addition of 6 µg Se per kg BW to sheep grazed on pastures in regions with low soil Se.

Altitude influences microbial diversity and herbage fermentation in the rumen of yaks.

BACKGROUND: Rumen microbiota in ruminants are vital for sustaining good rumen ecology, health, and productivity. Currently, limited information is available regarding the response of yaks (Bos grunniens) to fluctuating environments, especially the rumen microbiome. To address this, we investigated the diet, rumen bacterial community, and volatile fatty acids (VFA) of rumen fluid of yaks raised in the great Qinghai-Tibet plateau (QTP) at 2800 (low altitude, L), 3700 (middle altitude, M), and 4700 m (high altitude, H) above sea level. RESULTS: The results showed that despite a partial diet overlap, H yaks harbored higher fibrous fractious contents than the M and L grazing yaks. Bacteria including Christensenellaceae_R-7_group, Ruminococcus_1, Romboutsia, Alloprevotella, Eubacterium coprostanoligenes, Clostridium, Streptococcus, and Treponema were found to be enriched in the rumen of yaks grazing at H. They also showed higher rumen microbial diversity and total VFA concentrations than those shown by yaks at M and L. Principal coordinates analysis (PCoA) on weighted UniFrac distances revealed that the bacterial community structure of rumen differed between the three altitudes. Moreover, Tax4fun metagenome estimation revealed that microbial genes associated with energy requirement and carbohydrate metabolic fate were overexpressed in the rumen microbiota of H yaks. CONCLUSIONS: Collectively, our results revealed that H yaks had a stronger herbage fermenting ability via rumen microbial fermentation. Their enhanced ability of utilizing herbage may be partly owing to a microbiota adaptation for more energy requirements in the harsh H environment, such as lower temperature and the risk of hypoxia.

Substitution of leguminous forage for oat hay improves nitrogen utilization efficiency of crossbred Simmental calves.

Low nitrogen (N) utilization efficiency (NUE, the ratio of retained N to N intake [NI]) of ruminants is always a potential dietary protein wastage as well as a global environmental problem, and dietary N manipulation is the most effective way to improve NUE. We conducted 2 experiments to investigate the effects of replacing oat hay by leguminous forages (alfalfa hay [AH] in experiment [Exp] 1 and common vetch hay [CVH] in Exp 2) with 4 levels (0%, 8%, 16% or 24% AH and 0%, 10%, 20% or 30% CVH on dry matter [DM] basis) at the same crude protein (135 g/kg DM) and metabolizable energy (10.1 MJ/kg DM) on feed intake, N metabolism, NUE and blood composition of crossbred Simmental calves. Sixteen calves of each Exp were assigned to the four diets in a randomized block design. Faecal N (FN) output and the ratio of FN to NI increased with increasing AH/CVH proportions, whereas urinary N (UN) output, the ratio of UN to NI, and the ruminal ammonia N concentration gradually decreased in both experiments. Nutrient digestibility (DM, organic matter [OM] and neutral detergent fibre [NDF]) of calves showed a parabolic trend with gradually increasing AH/CVH proportions. The highest values of nutrient digestibility (DM, OM and NDF) of calves were observed in 16% AH in Exp 1 and 20% CVH in Exp 2. Our findings suggest that 16% and 20% substitution (as a percentage of the total DM allowance) of AH and CVH, respectively, for oat hay are optimal diets to improve NUE and reduce the potential impact of N excretion from livestock farming on the environment through shifting routes of N from urine to faeces without negative effects on live weight gain and nutrient digestibility of crossbred Simmental calves in dryland environments.

Increasing roughage quality by using alfalfa hay as a substitute for concentrate mitigates CH4 emissions and urinary N and ammonia excretion from dry ewes.

Twelve Hu sheep × thin-tail Han crossbred dry ewes with an average body weight of 32.6 ± 0.68 kg and an age of 3 years were arranged in a 3 × 3 Latin square design, with each experimental period of 24 d to evaluate the effect of substituting alfalfa hay in a portion of concentrate on nutrient intake, digestibility, N utilisation efficiency and methane emissions. The ratios of corn straw to alfalfa to concentrate for 3 diet treatments were 60:0:40, 60:15:25 and 60:30:10, respectively. Intake and digestibility were measured for each of the ewes, which were housed in individual metabolism crates for 6 d after an adaptation period of 14 d, and the feed was offered at 1.2 MEm to ensure approximately 10% orts. Methane emissions were determined in a respiration chamber for 2 consecutive d. An increase in the levels of alfalfa as a substitute for concentrate significantly increased the roughage, NSC and ADF intake and faecal N output as a proportion of N intake and manure N output. Furthermore, this increase in alfalfa input levels decreased DE, ME and N intake; nutrient digestibility; DE/GE, ME/GE and CH4 emissions per day; CH4 output expressed as a portion of the DM, OM and GE intake; and urinary N and ammonia N output, especially between extreme treatments. Alfalfa input levels had no effect on the BW, DM and GE intake; the EB or EB/GE intake; and the retained N. This study indicated that increasing alfalfa input as a substitute for concentrate could significantly decrease the digestibility, CH4 emissions and urinary N and NH4 + -N outputs; and shift the N excretion from urine to faeces; and could sustain a similar DM intake.

Relationship of mineral elements in sheep grazing in the highland agro-ecosystem.

Objective: Minerals are one of the important nutrients for supporting the growth of sheep grazing in the highland, northeast of China. The experiment was conducted to investigate the relationship of both macro and micro minerals in sheep grazing in the highlands of six districts located in the Qilian Mountain of China. Methods: Samples of herbage (n=240) and soil (n=240) were collected at random in a "W" shape across the area designated for harvesting from 24 farms, where the sheep commonly graze in October (winter) for mineral analyses. In addition, serum samples were taken via jugular vein from 20 sheep per farm from 24 farms (n=480 samples in total) for serum minerals analyses. Mean values of macro and micro minerals were statistically compared among districts and the correlations among soil-plant-animal were statistically analyzed and correlations were regressed, as well. Results: The results revealed that there were variations for both macro and micro minerals among districts. Statistical analysis of the correlation coefficients between herbage and sheep were significantly different for most of the minerals but not for P, Cu, and Se. Many correlation regression coefficients were found significantly different among minerals of herbage, soil, and sheep serum especially those of K, Na, Fe, Mn, and Zn (between herbage and sheep serum), and Fe and Mn (between herbage and soil), Na, Fe, Mn, and Zn (between soil and sheep serum), respectively. The regression coefficient equations derived under this experiment for prediction of Ca (R2=0.618), K (R2=0.803), Mg (R2=0.767), Na (R2=0.670), Fe (R2=0.865), Zn (R2=0.950), Mn (R2=0.936), and Se (R2=0.630), resulted in significant R2 values. Conclusion: It is inferred that the winter herbage minerals in all the districts were below the recommended levels for macro minerals which indicated there would be some mineral deficiencies in sheep grazing the herbage in these regions. Supplemental minerals may therefore play an important role in balancing the minerals available from the herbage in winter and would lead to increased productivity in sheep on the highland areas of China. These findings could be potentially applied to the other regions for improving the livestock productivity.

Assessment of cutting time on nutrient values, in vitro fermentation and methane production among three ryegrass cultivars.

OBJECTIVE: The 3×3 factorial arrangement was used to investigate if either high watersoluble carbohydrates (WSC) cultivars or suitable time of day that the grass cut could improve nutrient values and in vitro fermentation characteristics. METHODS: The 3 cultivars were mowed at 3 diurnal time points and included a benchmark WSC ryegrass cultivar 'Premium', and 2 high WSC cultivars AberAvon and AberMagic, which contained, on average, 157, 173, and 193 g/kg dry matter (DM) of WSC, and 36.0, 36.5, and 34.1 g/kg DM of N during 7th regrowth stage, respectively. The fermentation jars were run at 39°C with gas production recorded and sampled at 2, 5, 8, 11, 14, 17, 22, 28, 36, and 48 h. The rumen liquid was collected from 3 rumen fistulated cows grazing on ryegrass pasture. RESULTS: High WSC cultivars had significantly greater WSC content, in vitro DM digestibility (IVDMD) and total gas production (TGP), and lower lag time than Premium cultivar. Methane production for AberMagic cultivar containing lower N concentration was marginally lower than that for AberAvon and Premium cultivars. Grass cut at Noon or PM contained greater WSC concentration, IVDMD and TGP, and lower N and neutral detergent fiber (NDF) contents, but CH4 production was also increased, compared to grass cut in AM. Meanwhile, the effects of diurnal cutting time were influenced by cultivars, such as in vitro CH4 production for AberMagic was not affected by cutting time. The IVDMD and gas production per unit of DM incubated were positively related to WSC concentration, WSC/N and WSC/NDF, respectively, and negatively related to N and NDF concentrations. CONCLUSION: These results imply either grass cut in Noon or PM or high WSC cultivars could improve nutrient values, IVDMD and in vitro TGP, and that AberMagic cultivar has a slightly lower CH4 production compared to AberAvon and Premium. Further study is necessary to determine whether the increase of CH4 production response incurred by shifting from AM cutting to Noon and/or PM cutting could be compensated for by high daily gain from increased WSC concentration and DM digestibility.

Fast screening of aflatoxins in dairy cattle feeds with CE-LIF method combined with preconcentration technique of vortex assisted low density solvent-microextraction.

Aflatoxin contamination in agricultural products poses a great threat to humans and livestock. The aim of this study was to establish a simple, rapid, highly sensitive, and inexpensive method for the simultaneous detection of aflatoxin B1 , B2 , G1 , and G2 in agricultural products. We used a vortex assisted low density solvent-microextraction (VALDS-ME) technique for sample preconcentration and sample detection was achieved with a CE-LIF method. Aflatoxins were separated in an uncoated fused-silica capillary with the MEKC mode and were excited by a 355 nm UV laser to produce native fluorescence for detection. The obtained LOD and LOQ for the four aflatoxins were in the range of 0.002-0.075 and 0.007-0.300 µg/L, respectively, and the analysis time was within 6.5 min. Using the established method, aflatoxins were screened in naturally contaminated dairy cattle feed samples including alfalfa, bran, and corn kernel. The result shows that the alfalfa and bran samples were contaminated with aflatoxins to varying degrees. Compared with other analytical techniques for aflatoxin screening in agricultural products, this CE-LIF method combined with VALDS-ME preconcentration technique is simple, rapid, highly efficient, and inexpensive.

Rumen bacterial diversity of Tibetan sheep (Ovis aries) associated with different forage types on the Qinghai-Tibetan Plateau.

Diet is the great determinant of bacterial composition in the rumen. However, little is known about the rumen bacterial community of Tibetan sheep living in the special ecological environment of the Qinghai-Tibetan Plateau (QTP) of China. In the present study, we used high-throughput sequencing to investigate the rumen bacterial community of Tibetan sheep associated with two primary diets: alpine pasture diet (a continuation of the sheep's natural grazing diet) and oat (Avena sativa) hay diet on the QTP. The results showed that bacterial community richness and species diversity of the oat hay diet group were significantly greater than that of the native pasture diet group (p < 0.05). Principal co-ordinate analysis and analysis of similarities revealed that the bacterial community of the oat hay diet group was distinctly different from that of the native pasture diet group (p < 0.05). Bacteroidetes and Firmicutes were the predominant microbial phyla in the rumen. The rumen of oat-hay-fed sheep had higher proportions of Proteobacteria and novel bacteria species than the rumen of native-pasture-fed sheep. Actinobacteria, an uncommon bacterial phylum, occurred only in the oat-hay-fed group. At the genus level, Komagataeibacter, Ruminococcaceae_UCG-014, and Ruminococcaceae_NK4A214 showed significantly higher relative abundance in the oat-hay-fed sheep than in the native-pasture-fed sheep (p < 0.05). This study is the first of the QTP to employ high-throughput sequencing to examine the influence of diet on the rumen microbiome of Tibetan sheep.

Appropriate level of alfalfa hay in diets for rearing Simmental crossbred calves in dryland China.

OBJECTIVE: In dryland areas of China, alfalfa hay (AH) is a possible substitute for concentrate feed for beef cattle. To evaluate the potential benefits of this substitution, we studied the effect of the ratio of AH intake to total dry matter (DM) intake on average daily body-weight gain (ADG), dietary energy utilization status, and economic benefit in Gansu province. METHODS: In each of two feeding trials in 2016 (trial 1 [T1], July 3 to 17; trial 2 [T2], August 15 to September 23), crossbred male Simmental calves were allocated to low AH (LA), medium AH (MA), and high AH (HA) feeding groups (n = 4 per group). The target ADG was set as 1 kg for both trials. In a one-way-layout design based on conventional feeding practices in the province, calves received diets containing the different AH amounts, with a constant ratio of corn stover:total DM and decreasing rations of concentrate feed proportional to the increase in AH. Calves in T1 received AH at 15% (T1-LA), 23% (T1-MA), or 31% (T1-HA) of their dietary DM allowances; those in T2 received 9% (T2-LA), 24% (T2-MA), or 34% (T2-HA) AH. RESULTS: Among the T1 groups, both ADG and economic benefit were highest in T1-LA; whereas in T2, they were higher in the T2-LA and T2-MA groups than in T2-HA. Energy digestibility did not significantly differ among the groups in either trial. The dietary AH inclusion ratios of 14% in the warm season and 8% to 21% in the cool season appeared to yield optimal ADG, metabolizable energy intake, and economic benefit. CONCLUSION: Low-level inclusion of AH, ranging from 8% to 21%, is a practical approach for beef cattle feeding. This modified feeding regimen likely will promote increased growth performance during the fattening stage of beef steers in dryland areas of Gansu province, China.