Ruminally degradable intake protein (DIP) and metabolizable indispensable amino acid (MIAA) requirements of feedlot steers were evaluated. Dietary treatments consisted of isocaloric 80% concentrate steam-flaked corn-based diets containing either .8% urea, 1.5% fish meal (FM), 3.0% FM, 4.5% FM, or 4.5% soybean meal (SBM). Treatment effects on characteristics of ruminal and total tract digestion were evaluated using four Holstein steers (249 kg) with cannulas in the rumen and proximal duodenum. Ruminal digestibility of OM (RDOM; P < .05) and feed N (P < .01) and microbial N flow (MNF; P < .01) to the small intestine were greater with urea as the supplemental N source. The level of DIP was closely associated (R2 = .89) with MNF. Postruminal digestibility of OM was greater (P < .05) for FM than for urea-supplemented diets, compensating for lower RDOM. There were no treatment effects (P > .10) on DOM. As the level of FM was increased, MIAA increased linearly (P < .01). Intestinal MIAA were similar (P > .10) for urea- and SBM-supplemented diets. Treatment effects on 56-d growth performance were evaluated using 100 medium-framed crossbred steers (231 kg). Daily weight gain (linear effect; P < .01), DM intake (linear effect; P < .10), feed efficiency (linear effect; P < .05), and diet NE (linear effect; P < .05) increased with level of FM supplementation. Daily weight gain (P < .10) and DM intake (P < .05) were greater for urea- than for SBM-supplemented diets. Using bovine tissue as the reference protein, the biological value (based on chemical score) of the intestinal chyme protein averaged 73%; methionine was first-limiting. There was a close association (R2 = .99) between methionine supply to the small intestine and observed/expected dietary NE. The metabolizable methionine requirement (MMETR, g/d) of medium-framed feedlot steers can be reliably predicted from measures of BW and ADG (MMETR = 1.565 + .0234ADG[268 - (29.4 x .0557BW(.75)ADG(1.097))/ADG] + .0896BW(.75)). There was a very close association (R2 = .89) between DIP and MNF (MNF = 13.7DIP - .66DIP(2) + 25.9). At maximal observed synthesis, DIP accounted for 76% of the MNF. A minimum of 100 g DIP/kg of total tract digestible OM was required to maximize RDOM and MNF.

Using ammonium sulfate, three levels of dietary S (.15, .20, and .25%, DM basis) were evaluated in a finishing trial with 108 yearling crossbred heifers (384 kg). The basal diet contained (DM basis) 4% alfalfa hay, 6% sudangrass hay, 74% steam-flaked corn, 4% yellow grease, 6% cane molasses, and 6% protein-mineral supplement. Increasing dietary S decreased ADG (quadratic effect, P < .10), DMI (linear effect, P < .10), feed efficiency (quadratic effect, P < .10), diet NE (quadratic effect, P < .10), and longissimus muscle area (linear effect, P < .05). Six Holstein steers (218 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Treatment effects on ruminal and total tract digestion of OM and N were small (P > .10). However, ruminal digestion of ADF and starch was slightly lower (quadratic effect, P < .10), and postruminal digestion of ADF and starch was correspondingly greater (quadratic effect, P < .05) with supplemental S. Dietary S level did not influence (P > .10) ruminal synthesis of microbial N. Increasing dietary S did not influence (P > .10) ruminal pH or lactic acid. Increasing S decreased molar proportions of acetate (quadratic effect, P < .10) and increased molar proportions of propionate (linear effect, P < .10). We conclude that S in excess of .20% of dietary DM may have detrimental effects on growth performance and dietary NE. Excessive dietary S may also compromise carcass merit by decreasing longissimus muscle area.

Four Holstein steers (261 +/- 2 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the interaction of dietary Ca (.45 vs. 90%) and supplemental fat (0 vs 5% yellow grease) on characteristics of digestion. There were no treatment interactions (P > .10). Supplemental Ca did not influence (P > .10) digestibility of OM, NDF, starch, N, and fatty acids. Supplemental fat decreased ruminal (21%, P < .05) and total tract (3%, P < .01) digestibility of OM and ruminal (25%, P < .10) and total tract (20%, P < .01) digestibility of NDF. Supplemental fat increased (P < .10) ruminal microbial efficiency. Ruminal free Ca was not affected (P > .10) by Ca intake but was closely associated with ruminal pH and fatty acid intake (R2 = .84). Apparent ruminal Ca absorption was generally negative, being increased (P < .05) by Ca supplementation and decreased (P < .10) by fat supplementation. Postruminal (P < .05) and total tract (P < .01) apparent Ca absorption was increased by Ca supplementation. Supplemental fat did not influence (P > .10) postruminal or total tract Ca absorption. One hundred forty-four medium-frame crossbred steers were used to evaluate treatment effects on feedlot growth performance. There were no treatment interactions (P > .10). Increasing dietary Ca did not influence (P > .10) steer performance. Supplemental fat decreased (P < .01) DMI and increased NE value of the diet (P < .01). It is concluded that increasing dietary Ca from .45 to .9% in high-grain finishing diets will not affect the feeding value of supplemental fat and that high levels (5%) of supplemental fat will not have a detrimental effect on Ca absorption.

Transplantation of olfactory ensheathing cells (OECs) is a potential treatment for spinal cord injury (SCI). However, this process lacks extracellular matrix guiding cell growth, tissue morphogenesis, and remodeling. In order to solve this problem, we fabricated silk fibroin scaffolds (SFS) with different fiber diameters by electrospinning. The behaviors of OECs on 300 and 1800 nm SFS were studied by analyzing cell morphological feature, distribution, and proliferation. The results showed the 300 nm SFS with good potential to guide OECs growth. Subsequently, the properties of 300 nm SFS were further investigated along with PLL. With 300 nm SFS, the preservation of cell phenotype was confirmed by the presence of cell-specific markers, including nerve growth factor receptor p75 and glial fibrillary acidic protein. And the migration behaviors of OECs were also observed by Leica AF6000. In addition, migration tracks, turning behavior, migration distances, migration speeds, and forward migration indices were calculated. Furthermore, the expression of neurotrophic factors was assayed at transcription and protein levels using RT-PCR and ELISA. All these results indicated the diameter of the fiber played an important role in guiding cell adhesion, growth, and migration in vitro and the 300 nm SFS could be suitable to construct tissue-engineered scaffolds for SCI repair.

The improvement of the fermentation quality of rice straw silage by application of lactic acid bacteria (LAB) and glucose was investigated in this study. Sixteen rice varieties were harvested at the maturity stage and the rice straw was ensiled with LAB inoculant (1×10 5 cfu/g of fresh weight) and glucose (2% of fresh weight). Inoculation with LAB improved the fermentation as reflected in reductions in pH, acetic acid (by 3.7 to 78.3%), butyric acid (by -6.0 to 100.0%) and ammonia nitrogen (by 1.0 to 71.7%) concentrations, and increases in lactic acid (by 43.9 to 282.9%) and crude protein concentrations compared with the control. Application of LAB plus glucose was more effective in improving fermentation quality than LAB alone. The variety of rice straw which contained relatively high levels of water soluble carbohydrates (WSC) tended to obtain better fermentation quality. The results suggested that LAB application and selection of rice varieties whose straw contained high levels of WSC were effective in improvement of the fermentation quality of rice straw silage.

Background Phosphorus (P) deficiency in soil is a worldwide issue and a major constraint on the production of sorghum, which is an important staple food, forage and energy crop. The depletion of P reserves and the increasing price of P fertilizer make fertilizer application impractical, especially in developing countries. Therefore, identifying sorghum accessions with low-P tolerance and understanding the underlying molecular basis for this tolerance will facilitate the breeding of P-efficient plants, thereby resolving the P crisis in sorghum farming. However, knowledge in these areas is very limited. Results The 29 sorghum accessions used in this study demonstrated great variability in their tolerance to low-P stress. The internal P content in the shoot was correlated with P tolerance. A low-P-tolerant accession and a low-P-sensitive accession were chosen for RNA-seq analysis to identify potential underlying molecular mechanisms. A total of 2089 candidate genes related to P starvation tolerance were revealed and found to be enriched in 11 pathways. Gene Ontology (GO) enrichment analyses showed that the candidate genes were associated with oxidoreductase activity. In addition, further study showed that malate affected the length of the primary root and the number of tips in sorghum suffering from low-P stress. Conclusions Our results show that acquisition of P from soil contributes to low-P tolerance in different sorghum accessions; however, the underlying molecular mechanism is complicated. Plant hormone (including auxin, ethylene, jasmonic acid, salicylic acid and abscisic acid) signal transduction related genes and many transcriptional factors were found to be involved in low-P tolerance in sorghum. The identified accessions will be useful for breeding new sorghum varieties with enhanced P starvation tolerance. Electronic supplementary material The online version of this article (10.1186/s12870-019-1914-8) contains supplementary material, which is available to authorized users.

One hundred twenty medium-frame crossbred steers (364 kg) were used in a 106-d feedlot trial to compare the feeding value of Condor, a hulless barley (HB), with Leduc, a conventional covered barley (CB). Dietary treatments consisted of a finishing diet containing 77% grain (DM basis) as 1) steam-flaked corn (SFC); 2) dry-rolled HB (DRB-H); 3) steam-flaked HB (SFB-H); 4) dry-rolled CB (DRB-C); and 5) steam-flaked CB (SFB-C). Feed intake was lower (8.6%, P < .01) for HB than for CB. Diet NE was greater for HB than for CB (P < .01) and for SFB than for DRB (P < .01). Incidence of liver abscess was greater for DRB than for SFB (239%, P < .05) and for HB than for CB (167%, P < .10). Diet NE were greater (P < .10) for SFC than for barley treatments. Treatment effects on characteristics of digestion were evaluated using five Holstein steers (202 kg) with cannulas in the rumen and proximal duodenum. There were barley variety x grain processing interactions on ruminal digestion of OM (P < .10), ADF (P < .05), and starch (P < .05). Ruminal OM digestion increased (9.0%) with steam flaking HB and decreased slightly (1.9%) with steam flaking CB. Ruminal digestion of starch was enhanced more dramatically (21.5 vs 8.4%, respectively) with steam flaking HB than with CB. Steam flaking decreased ruminal ADF digestion of HB only slightly (6.2%), whereas with CB the decrease was more dramatic (54.3%). Ruminal degradable N was greater (P < .10) for CB than for HB and for DRB than for SFB (19.8%, P < .05). Estimates of ruminal degradable N in DRB-H, SFB-H, DRB-C, and SFB-C were 69.7, 53.9, 78.5, and 65.0%, respectively. Postruminal digestion of OM (P < .01), starch (P < .05), and N (P < .10) were greater for HB than for CB. Steam flaking barley increased (P < .01) postruminal N digestibility. Total tract digestibility of OM (P < .01), ADF (P < .05), starch (P < .01), and energy (P < .01) were greater for HB than for CB. Digestibility of ADF in barley hulls was only 6.4%. Steam flaking increased (P < .01) total tract digestibility of starch. Ruminal digestibility of OM and feed N was lower (P < .01) for SFC than for barley diets. Ruminal pH was lower (P < .10) for HB than for CB and for SFB than for DRB (P < .01). Ruminal propionate was higher (24.1%, P < .01), and methane was lower (17.9%, P < .01) for HB than for CB.

Rice straw and sweet potato vines are the main by-products of agricultural crops, and their disposal creates problems for the environment in the south of China. In order to establish an easy method for making rice straw silage successfully, experiments were conduct to evaluate fermentation quality and nutritive value of rice straw silages ensiled with or without sweet potato vine. Paddy rice straw (PR) and upland rice straw (UP) were ensiled alone or with sweet potato vines (SP) by a ratio of 1:1 (fresh matter basis), over 3 years. Compared with rice straw silages ensiled alone, the mixed-material silages (PR + SP, UR + SP) showed higher fermentation quality with lower propionic acid content and NH -N ratio of total N, and higher (P < 0.05) concentrations of lactic acid and acetic acid, resulting in decrease (P < 0.05) of dry matter loss and higher (P < 0.05) in vitro ruminal dry matter digestion. When the fermentation quality, chemical composition and in vitro rumen fermentation characteristics were considered, ensiling would be an effective way of utilization of rice straw and sweet potato vines in the regions where rice and sweet potato are harvested at same season, and the sweet potato vines have the potential to improve rice straw fermentation quality with low water soluble carbohydrate content in south of China.