Diazotrophs for Lowering Nitrogen Pollution Crises: Looking Deep Into the Roots

During and after the green revolution in the last century, agrochemicals especially nitrogen (N) were extensively used. However, it resulted in a remarkable increase in crop yield but drastically reduced soil fertility; increased the production cost, food prices, and carbon footprints; and depleted the fossil reserves with huge penalties to the environment and ecological sustainability. The groundwater, rivers, and oceans are loaded with N excess which is an environmental catastrophe. Nitrogen emissions (e.g., ammonia, nitrogen oxide, nitrous oxide) play an important role in global climate change and contribute to particulate matter and acid rain causing respiratory problems, cancers, and damage to forests and buildings. Therefore, the nitrogen-polluted planet Earth needs concerted global efforts to avoid the disaster. Improved agricultural N management focuses on the synchronization of crop N demand and N supply along with improving the N-use efficiency of the crops. However, there is very little focus on the natural sources of N available for plants in the form of diazotrophic bacteria present inside or on the root surface and the rhizosphere. These diazotrophs are the mini-nitrogen factories that convert available (78%) atmospheric N2 to ammonia through a process known as "biological nitrogen fixation" which is then taken up by the plants for its metabolic functioning. Diazotrophs also stimulate root architecture by producing plant hormones and hence improve the plant's overall ability to uptake nutrients and water. In recent years, nanotechnology has revolutionized the whole agri-industry by introducing nano-fertilizers and coated/slow-releasing fertilizers. With this in mind, we tried to explore the following questions: To what extent can the crop N requirements be met by diazotroph inoculation? Can N input to agriculture be managed in a way leading to environmental benefits and farmers saving money? Can nanotechnology help in technological advancement of diazotroph application? The review suggests that an integrated technology based on slow-releasing nano-fertilizer combined with diazotrophs should be adopted to decrease nitrogen inputs to the agricultural system. This integrated technology would minimize N pollution and N losses to much extent.

Evaluating the impact of organic chromium on hepatic phospholipid fatty acid molecular species, transcription of genes associated with lipid metabolism and oxidative status in broiler chickens fed flaxseed

Flaxseed is a rich source of α-linolenic acid (ALA, 18:3 n-3) and can be used to enrich chicken tissues with n-3 fatty acids (FA). However, antinutritional factors in flaxseed compromise the live performance of birds coupled with increased oxidative stress. Chromium (Cr) is a trace element with antioxidant properties. It is hypothesized that Cr supplementation will affect the hepatic total lipid profile, phospholipid n-3 and n-6 FA molecular species, lipid oxidation products, and transcription of genes associated with lipid metabolism in broiler chickens fed flaxseed. Ninety (n = 90), day-old Cornish cross chicks were fed a corn-soybean meal-based diet containing 0% flaxseed (CTR), 10% flaxseed (FLAX), and FLAX + 0.05% organic Cr (FLAXCr) for 42 d. The chicks were kept in 18 pens with 5 chicks per pen. For all response variables, the effect of dietary treatments were compared separately using SAS 9.4. P values were considered significant at ≤0.05. Total lipids, saturated FA, long-chain (≥20C) n-6 FA were reduced while total n-3 FA and long-chain n-3 FA were higher in the liver of FLAX and FLAXCr than CTR (P < 0.05). Hepatic phosphatidylcholine (PC) and phosphatidylethnolamine (PE) n-3 species (36:5, 38:6) were higher in FLAX and FLAXCr compared to CTR (P < 0.05). On the contrary, n-6 species in PC (36:4, 38:4) and PE (38:4) were lower in FLAX and FLAXCr compared to CTR (P < 0.05). Addition of Cr to a flaxseed-containing diet led to an increase in PE 36:4 (P < 0.05). A decrease in the transcription of ELOVL6 gene involved in de novo lipid synthesis was observed in FLAXCr (P = 0.01). An increase in the transcription of genes involved in FA oxidation (ACAA2, ACOX1) was observed in FLAX compared to FLAXCr (P = 0. 05; P = 0.02). A trend for a decrease in the transcription of FADS2 and HMGCS1 was observed in FLAXCr than CTR and FLAX (P = 0.06; 0.08). Transcription of other genes involved in de novo lipid synthesis (FASN, PPARA), FA oxidation (CPT1A, CPT2, ACAA1), and oxidative stress response (GPX1, NQO11, GSTA2, SLC40A1, NFE2L2) were not affected by the diets (P > 0.05). Lipid peroxidation products measured as thiobarbituric acid reactive substances (TBARS) in liver was reduced in FLAXCr than CTR (P < 0.05) and was not different from FLAX (P > 0.05). Serum cholesterol and aspartic aminotransferase were reduced in FLAX and FLAXCr compared to CTR (P < 0.05). The serum glucose level was decreased in FLAX compared to CTR (P < 0.05) and a trend in decrease was noticed in FLAXCr vs. CTR (P = 0.10). Serum TBARS were higher in CTR and FLAXCr compared to FLAX (P < 0.05). In conclusion, flaxseed supplementation enhances total and long-chain n-3 FA while reducing total lipids, saturated, and n-6 FA in the liver. Supplementing Cr along with flaxseed increased n-6 FA species in the hepatic PE and decreased the transcription of genes involved in FA oxidation and lipid synthesis.

Evaluating the impact of organic chromium with flax seed in broiler diets: effects on production performance, breast muscle pathology, and meat quality aspects

The study investigated the impact of organic chromium (Cr) and flax seed supplementation on live performance, carcass yield, muscle lipid profile, histopathological aspects, and meat quality parameters in broilers. Ninety (n = 90), day-old Cobb chicks were fed a corn-soybean meal-based diet containing 0% flax seed (Control), 10% flax seed (Diet 1) and Diet 1 + 0.05% organic Cr (Diet 2). The experiment was a completely randomized design and chicks were placed in 6 pens with 5 chicks per each pen. Pen was the experimental unit for production performance and bird collected from each pen was considered as experimental unit for all other analysis. On d 43, 45, and 48, one bird per pen were euthanized. A one-way ANOVA was performed with diet as the main factor and significance was set at P < 0.05. Significant differences between each treatment were analyzed by GLM Lean Square Method and Tukey's Honestly Significant Difference test. Weight gain and feed:gain was determined at d (1-11), (12-21), and (22-42). For all response variables, the effects among dietary treatments were compared using ANOVA separately using SAS 9.4. P -values were considered significant at ≤0.05. At d 22, Diet 1 and Diet 2 birds had lower BW and feed:gain than Control (P < 0.05). At d 42, Diet 2 birds were higher in BW with improved feed:gain when compared to Diet 1 (P < 0.05) but were not different from Control (P > 0.05). The overall weight gain was higher in Diet 2 and Control compared to Diet 1 (P < 0.05) and overall feed:gain was the highest in Control than the experimental diets (P < 0.05). Histopathological changes in breast muscle including floccular/vacuolar degeneration, fibrosis, lipidosis, interstitial inflammation, and muscle lysis were less pronounced in Diet 1 compared to Diet 2 (P < 0.05). Breast muscle total fat and cholesterol was lower in Diet 1 compared to Control (P < 0.05). Diet 1 and Diet 2 increased (>2-5 fold) total and long chain (≥20C) n-3 fatty acids (FA) in the breast muscle (P < 0.05) compared to Control. Lipid peroxidation products measured as thiobarbituric acid reactive substances were lower in the breast muscle of Diet 1 and Diet 2 compared to Control (P < 0.05). Phospholipid n-3 FA molecular species in phosphatidylcholine (PC) 36:5, 38:6, and phosphatidylethanolamine (PE) 36:5 were higher in breast muscle of Diet 1 than Control (P < 0.05) and was not different from Diet 2 (P > 0.05). A decrease in n-6 FA species (36:4 and 38:4) was observed in PC and PE of Diet 1and Diet 2 compared to Control (P < 0.05). Drip loss values were reduced in Diet 1 and Diet 2 versus Control (P < 0.05). As consumer demand for n-3 FA-rich poultry products are on the rise, Cr may serve as a feed supplement that could be used in broilers fed flax seed-containing diets for enriching edible tissues with n-3 FA, while enhancing production performance.

Effects of supplementing rumen-protected arginine on performance of transition cows

An experiment was conducted to determine the effects of supplementing rumen-protected arginine (RPA) on productive performance in dairy cows. One-hundred and 2 cows were blocked by parity and then by energy-corrected milk (ECM) yield. Within block, cows were randomly assigned to control (CON) that received 200 g/d of a mixture of hydrogenated soybean oil and heat-treated soybean meal to supply 30 g of metabolizable protein (MP), or 200 g/d of a product containing 30 g of metabolizable arginine (RPA), which increased the dietary arginine from 5.7 to 7.5% of the MP from 250 d of gestation to 21 d postpartum. After 21 d postpartum, cows were fed the same diet and data were collected until 84 d postpartum. Cows fed RPA produced an additional 2.5 kg of colostrum (5.3 vs. 7.8 ± 1.0 kg) and 220 g more immunoglobulin G (526 vs. 746 ± 93 g) than CON cows. Supplementing RPA increased the yields of milk (32.8 vs. 34.9 ± 1.0 kg/d), ECM (37.8 vs. 40.9 ± 1.2 kg/d), and milk total solids (4.48 vs. 4.86 ± 0.14 kg/d) in the first 21 DIM. The benefits of RPA extended beyond the period of supplementation, with a 6.4% increase in yield of ECM per kg of dry matter consumed in all cows (1.88 vs. 2.00 ± 0.05 kg/kg) and an increase in ECM yield, but only in parous cows (44.2 vs. 48.5 ± 1.5 kg/d). Feeding RPA increased the concentrations of urea N in plasma pre- (12.5 vs. 13.9 ± 0.4 mg/dL) and postpartum (11.6 vs. 13.2 ± 0.4 mg/dL), and in milk during the first 21 d postpartum (11.0 vs. 12.0 ± 0.3 mg/dL). Treatment did not affect the concentrations of AA in plasma prepartum, but feeding RPA tended to increase citrulline (72.5 vs. 77.5 ± 2.7 μM), whereas RPA either tended to decrease isoleucine (129.5 vs. 120.9 ± 5.7 μM) or decreased the concentrations of leucine (181.3 vs. 170.2 ± 6.4 μM) and valine (293.2 vs. 276.7 ± 10.4 μM) postpartum. Feeding RPA increased the relative expression of transcripts involved in AA transport (SLC38A4), urea cycle (ARG1), and gluconeogenesis (PC, PEPCK, and G6PC) in hepatic tissue. Feeding diets to supply additional arginine as RPA during the transition period benefited productive performance in dairy cows that extended beyond the period of supplementation despite minor changes in plasma AA concentrations.