Low fertilizer use efficiency is commonly found in China’s agriculture sector.  It is critical to understand the drivers of fertilizer use in order to increase fertilizer use efficiency (FUE).  The purpose of this paper is to investigate the relationship between farm size and FUE based on farm-level data in China.  The results suggest a positive farm size–FUE relationship.  The estimated elasticities of farm size for rice, maize, wheat–maize, and rice–maize are similar, and the average elasticity of farm size is around 0.2.  Statistically, a 1% increase in farm size is associated with a 0.2% increase in FUE.  The positive effect of farm size on FUE is not due to the increase in yield, but the reduction in fertilizer use while keeping yield largely unchanged.  The findings suggest that promoting the expansion of farm size may increase FUE, and thus reduce environmental pollution caused by fertilizer overuse.

The assessment of the biomass of energy crops has garnered widespread interest since renewable bioenergy may become a substantial proportion of the future energy supply, and modeling has been widely used for the simulation of energy crops yields.  A literature survey revealed that 23 models have been developed or adapted for simulating the biomass of energy crops, including Miscanthus, switchgrass, maize, poplar, willow, sugarcane, and Eucalyptus camaldulensis.  Three categories (radiation model, water-controlled crop model, and integrated model with biochemical and photosynthesis and respiration approaches) were addressed for the selected models according to different principles or approaches used to simulate biomass production processes.  EPIC, ALMANAC, APSIM, ISAM, MISCANMOD, MISCANFOR, SILVA, DAYCENT, APEX and SWAT are radiation models based on a radiation use efficiency approach (RUE) with few empirical and statistical parameters.  The AquaCrop model is a typical water-crop model that emphasizes crop water use, the expression of canopy cover, and the separation of evapotranspiration to soil evaporation and plant transpiration to drive crop growth.  CANEGRO, 3PG, CropSyst and DSSAT are integrated models that use photosynthesis and respiration approaches.  SECRETS, LPJmL, Agro-BGC, Agro-IBIS, and WIMOVAC/BioCro, DNDC, DRAINMOD-GRASS, and AgTEM are integrated models that use biochemical approaches.  Integrated models are mainly mechanistic models or combined with functional models, which are dynamic with spatial and temporal patterns but with complex parameters and large amounts of input data.  Energy crop models combined with process-based models, such as EPIC in SWAT and CANEGRO in DSSAT, provide good examples that consider the biophysical, socioeconomic, and environmental responses and address the sustainability and socioeconomic goals for energy crops.  The use of models for energy crop productivity is increasing rapidly and encouraging; however, relevant databases, such as climate, land use/land cover, soil, topography, and management databases, are scarce.  Model structure and design assumptions, as well as input parameters and observed data, remain a challenge for model development and validation.  Thus, a comprehensive framework, which includes a high-quality field database and an uncertainty evaluation system, needs to be established for modeling the biomass of energy crops.

    D-Lactate-utilizing bacteria play important roles in maintaining the balance of gut lactate; however, studies on gut D-lactate-utilizing bacteria have been limited. This study aimed to isolate and identify D-lactate-utilizing bacteria from pig gut using the Hungate roll-tube method, and to investigate their metabolic characteristics in vitro. Six different anaerobes were isolated from pig feces, which were identified as related to Bacteroides fragilis, Bacteroides acidifaciens, Veillonella denticariosi, Veillonella caviae, Bacteroides uniformis, and Megasphaera elsdenii based on the 16S rRNA gene sequences. All strains had a significant ability to utilize D-lactate, which was concluded after in vitro fermentation with 25 mmol L–1 D-lactate as the primary carbon source. Of all 6 strains, M. elsdenii J6 showed the highest efficiency of D-lactate utilization and produced a higher ratio of butyrate in total short chain fatty acids (SCFAs). Thus, the in vitro fermentation characteristics of this strain in D-, L-, and DL-lactate mixtures (D-lactate:L-lactate=1:1 or 1:2) were further studied. The results showed that M. elsdenii J6 preferred utilizing D-lactate, and produced more SCFA when using D-lactate as the primary carbon source. The findings suggest that the administration of D-lactate-utilizing bacteria such as M. elsdenii J6 may have a potential advantage in the alleviation of D-lactic acidosis in the animal gut.

  To investigate the roles of Escherichia coli in the pathogenesis of postpartum uterine diseases in dairy cows, a total of 145 E. coli isolates were recovered from 18 healthy cows (61 isolates) and 25 cows with clinical endometritis (84 isolates) at 25–35 days after parturition. Genomic characteristics including phylogenetic grouping, genetic diversity and virulence genes of E. coli isolates were screened to profile the characteristics related to uterine infections. The susceptibility of the bacteria against 23 antibiotics was also evaluated to support prevention and treatment of clinical cases. Genetic diversity of E. coli identified by random amplification of polymorphic DNA (RAPD) revealed 103 clonal types, including 3 common types to unaffected cows and endometritis cows, 39 types specific to healthy cows and 61 types in endometritis subjects. In addition, the isolates from endometritis uteri showed more genetic variability compared with that of healthy cows. According to the findings of phylogenetic grouping, the E. coli isolates were assigned to group A (35.9%), B1 (59.3%) and D (4.8%). The expression of 10 of 20 virulence gens were detected positively, and only fimH gene was revealed significantly (P<0.05) associated with endometritis. From antimicrobial susceptibility test, E. coli was found highly resistant to tetracycline, ampicillin, carbenicillin and amoxicillin, but sensitive to amikacin, netilmicin, tobramycin, cefepime and ceftazidime. In conclusion, E. coli were extensively observed in both healthy and endometritis cows, and presented a large clonal types, however, fimH was the only gene observed associated with clinical endometritis. Our results suggest that the drugs like amikacin, netilmicin, tobramycin and cefepime could be considered for preventing and treating clinical endometritis in the practical management of dairy cow.  

Erhualian and Landrace breeds are typical genetically obese and lean pigs, respectively. To compare the fecal methanogenic Archaeal community between these two pig breeds, fecal samples from different growth phase pigs were collected and used for PCR-denaturing gradient gel electrophoresis (DGGE) with two primer pairs (344fGC/519r and 519f/915rGC) and real-time PCR analysis. Results showed that a better separation and higher quality of bands pattern were obtained in DGGE profiles using primers 344fGC/519r as compared with primers 519f/915rGC. Sequencing of DGGE bands showed that the predominant methanogens in the feces of Erhualian and Landrace pigs belonged to Methanobrevibacter spp. and Methanosphaera spp. Real-time PCR analysis revealed that there was no significant difference in the numbers of fecal total methanogens between Erhualian and Landrace pigs; however, pig growth phase affected the numbers of 16S rRNA genes of total methanogens and Methanobrevibacter smithii. Dissociation curves of methyl coenzyme-M reductase subunit A (mcrA) gene fragments amplified with real-time PCR showed all samples possessed a single peak at 82°C, which might be associated with M. smithii. Samples from the same growth phase of each breed showed good replicative dissociation curves. The results suggest that the growth phase (including diet factor) other than genotype of pig may affect the fecal methanogenic Archaeal community of pigs.

Microbiota in the gastrointestinal tract (GIT) of piglets during weaning transition can experience a sharp change which could result in growth reduction and diarrhea of weaned piglets. Dietary manipulations can play an important role in attenuating such changes caused by weaning stress. Therefore, ileal and colonic contents of weaned piglets were used as inocula, mannan oligosaccharide (MOS) or sugar beet pulp (SBP) was supplied as single energy sources to investigate effects of MOS or SBP on the shifts of gastro-intestinal microflora and lactobacilli populations. The universal bacteriaand lactobacilli-specific PCR/denaturing gradient gel electrophoresis (DGGE), cloning and sequencing techniques were used. DGGE profiles of the universal bacteria showed that great changes were found in the position, numbers and intensity of dominant bands after fermentation. The similarity of bacterial community between ileum and colon was increased to 85-97% by MOS or SBP treatment after fermentation from the similarity with 20% before fermentation. MOS treatment significantly increased the bacterial diversity and band number in both ileal and colonic fermentation (P<0.05). SBP treatment significantly increased the bacterial diversity and band number in colon (P<0.05). It implies that some species were enriched by the addition of MOS or SBP to increase the similarity and diversity of bacterial community in weaned piglets. Five specific bands appearing in MOS or SBP treatment group after fermentation were cloned and sequenced, the changes of species related to Prevotella and Ruminococcus were observed. Two bands related to uncultured bacterium with 98% similarity were detected by MOS or SBP treatment. However, there were no effects on the similarity, diversity index and lactobacilli species revealed by MOS or SBP treatment. These results imply that MOS or SBP could have beneficial effects on the weaning piglets by stablizing microbiota in the GIT microflora.