Browsing by Subject "Stickstoffnutzungseffizienz"
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Publication Evaluation and improvement of N fertilization strategies in the wheat/maize double-cropping system of the North China Plain(2015) Hartmann, Tobias Edward; Müller, TorstenThe North China Plain (NCP) is the main production area of cereal crops in China. The intensification of agricultural systems and the increased use of chemical N fertilizers are contributing to environmental pollution. One of the objectives of this thesis was to apply an Nmin based approach for the calculation of N application rates to a previously over-fertilized farmers field of the NCP and to evaluate the potential of reducing N inputs while maintaining the grain yield of a summer-maize/winter-wheat double-cropping system; and to evaluate fertilizer strategies, aiming to reduce N inputs and loss. Using an Nmin based approach for the calculation of fertilizer application rates, a reduction of fertilizer input by up to 50% compared to farmers practice (550 kg N ha-1 a-1) is possible without negatively affecting the grain yield of a wheat / maize double cropping system. The extreme re-supply of N during the summer-vegetation periods of maize in the first two experimental seasons resulted in high yields of the control treatment (CK: 2009: 5.7 and 2010: 5.9 Mg ha-1), which did not significantly differ from the fertilized treatments. This resulted in a reduced recovery efficiency of N (REN: 0.09 kg kg-1 – 0.30 kg kg-1). According to the results of this field experiment there was no agronomic justification for the application of fertilizer N. The grain yield of maize of the control treatment finally decreased in the third vegetation period of summer-maize. While maintaining the yield level, the optimized application of N increased REN (0.37 – 0.58 kg kg-1) significantly compared to farmers practice (0.21 kg kg-1) in this final vegetation period of maize. Wheat, in contrast to maize, is dependent on the application of fertilizer N for yield formation. In both vegetation periods of wheat, REN of the reduced treatments (0.34 – 1.0 kg kg-1) was significantly higher compared to FP (0.26 and 0.27 kg kg-1). The highest cumulated (5 vegetation periods) agronomic efficiency of N, as well as cumulated grain yield of the wheat/maize double-cropping system was observed when ammoniumsulphate-nitrate was applied in combination with the nitrification inhibitor 3,4-dimethylpyrazolephosphate (ASNDMPP: AEN: 19 kg kg-1, yield: 35 Mg ha-1) and according to crop N demand and residual soil mineral N. The highest REN was observed when urea ammonium nitrate was applied in a shallow, banded depot (UANDEP: 40 kg kg-1). The results of this field experiment further show that the N surplus (fertilized N - grain N) as well as the N balance (N Input - N output) after harvest are significantly lower when an optimized approach to fertilizer application is followed. The over-application of N for an optimized application of urea or ASNDMPP (Surplus: -25kg to 98 kg N ha-1; Balance: -36 to 102 kg N ha-1) was significantly reduced compared to current farmers practice (Surplus: 156kg to 187 kg N ha-1; Balance: 56 to 262 kg N ha-1). This leads to lower residual N in the soil horizon from 0 - 90 cm in the reduced treatments (113 kg N ha-1 at end of experiment) compared to FP (293 kg N ha-1). The results of this experiment indicate that N contained in the residues of maize is available only to the subsequent summer-crop and may sufficiently supply N for the yield formation of maize. Should the over-application of N be effectively reduced in the cropping systems of the NCP it is therefore necessary to take the N mineralization potential of soils into account. Based on the results of this field experiment and others, a crop-soil interface model (HERMES) was calibrated and validated to the conditions of the NCP. Finally, this research observed the effect of wheat straw and the urease inhibitor (UI) N-(n-buthyl) thiophosphoric triamide (nBPT) on the turnover of urea, as well as the loss of ammonia and nitrous oxide from an alkaline soil of the NCP. UI inhibit or reduce the appearance of ammonia after the application of urea and almost completely prevent the loss of N as ammonia (urea: 12 – 14% loss). nBPT effectively reduces the rate of urea hydrolysis but does not down-regulate the process enough to completely inhibit nitrification, thereby maintaining the availability of N from urea for plants. Further, the addition of wheat straw prolongs the appearance of ammonium after the application of urea while the appearance of nitrate is reduced. Wheat straw may therefore either act as a stimulant of hydrolysis or as an inhibitor of nitrification. The addition of urea increases soil respiration and the emission of N2O drastically, possibly acting as a C and N source for microbial organisms and causing a priming effect on microbial activity in soils. This effect was increased further when wheat straw as well as urea were added to soil. nBPT, in contrast, prevents a significant increase in CO2-respiration and N2O-emission. The urease inhibitor may therefore generally restrict microbial activity or shift nitrification/denitrification processes towards the emission of N2.Publication Genomische und mikrobielle Analysen von Effizienzmerkmalen beim Schwein(2022) Weishaar, Ramona Ribanna; Bennewitz, JörnMost traits in animal breeding, including efficiency traits in pigs, are influenced by many genes with small effect and have moderate heritabilities between 0.1 and 0.5, which enables efficient selection. These so-called quantitative traits are influenced by genetic factors and environmental factors. The use of next-generation sequencing methods, such as 16S rRNA sequencing to analyse the gut microbiome of livestock, allows identification and analysis of the gut microbiota. It has been shown that the composition of the microbiota in the gastrointestinal tract is heritable and has an influence on efficiency traits. Thus, the animal genome influences the phenotype not only directly by altering metabolic pathways, but also indirectly by changing the composition of the microbiota. This increases the interest in implementing gut microbiota into existing breeding strategies as an explanatory variable. The potential of an efficient utilization and absorption of nutrients varies between individuals. Differences in nutrient absorption depend on feed intake, digestion of dietary components in the stomach and intestine, and intake of digested nutrients from the gastrointestinal tract into blood and lymphatic vessels. Undigested nitrogen is excreted as urea and can be detected by blood urea nitrogen (BUN). The BUN is correlated with efficiency traits and there exist differences between pig breeds. Thus, therefore the BUN would be conceivable as an easier recordable trait for nitrogen utilisation efficiency in pig breeding. In the first chapter of this study, an existing data set of the Department for Animal Genetics and Breeding of the University of Hohenheim was used. This is a data set with 207 phenotyped and genotyped Piétrain sows. The relationship between gut microbial composition, efficiency traits and the porcine genome is investigated using quantitative genetic methods. The heritabilities of the traits FVW, RFI, TZ, and FI ranged from 0.11 to 0.47. The microbiabilities of the traits were significant and ranged from 0.16 to 0.45. In a further step, the previously generated microbial animal effects were used as observation vector for a genomic mixed model. Subsequently, heritabilities for the microbial animal effect were estimated, ranging from 0.20 to 0.61. The similarity of the heritabilities and microbiabilities suggests that the traits are influenced to a similar extent by both genetics and gut microbiota and that the microbial animal effect is determined by the host. These results are underlined by the identification of genera and phyla with significant effects on efficiency traits. The microbial architecture of the traits demonstrated a poly-microbial nature, there are many OTUs with small effects involved in the variation of the observed traits. Genomic Best Linear Unbiased Predictions (G-BLUP) and Microbial Best Linear Unbiased Predictions (M-BLUP) were performed to predict complex traits. The accuracies of M-BLUP and G-BLUP were all in a similar range between 0.14-0.41. This shows that gut microbiota could be used to predict performance traits or be included as a variable in the existing models of breeding value estimation to realize an increase in accuracies. The second part of the paper analysed a dataset from a research project called "ProtiPig". The data set included 475 sows and castrates of crossbreds of German Landrace x Piétrain and was analysed for protein utilization efficiency and nitrogen(N)-utilization efficiency. N-utilization efficiency is a trait that is difficult to record. Because conventional metabolic cage methods are a very complex procedure and difficult to integrate in the standard recording, it was tested whether the BUN is suitable as a proxy trait. Moderate to medium heritabilities could be estimated for all traits and ranged from 0.13 to 0.49. The genome-wide association studies showed that the traits were polygenic. For the BUN, SNPs could be detected that were above the genome-wide significance level. Significant genetic and phenotypic correlations were found between some traits. In particular, the heritabilities of BUNs and the significant genetic correlation between BUN and N-utilization efficiency indicate an opportunity to use the BUN to select for improved N-utilization efficiency. Before the research results generated here can be implemented in breeding practice, further questions must be clarified. In addition, a larger number of animals is needed to validate the results. The results presented here demonstrate the potential of microbial-assisted breeding value estimation and the use of BUN to identify selection candidates for breeding for increased efficiency.Publication Investigations on factors influencing the response of broiler chickens to low crude protein diets with specific regard to nonessential amino acids(2020) Hofmann, Philipp; Rodehutscord, MarkusNitrogen (N) excretion caused by animal husbandry can have negative effects on the environment. Lowering dietary crude protein (CP) concentrations can reduce these negative impacts by lowering the N excretion of the animals. However, reduction of dietary CP concentrations for broiler chickens may be accompanied by reduced growth. This thesis focused on the effects of dietary CP reduction on growth of broiler chickens and influencing factors that need to be considered in low CP diets. The first study was carried out to investigate to what extent dietary CP concentrations can be reduced when dietary glycine equivalent (Glyequi) and essential amino acid (AA) concentrations are adequately supplied. Further, it was the aim to determine the response of broiler chickens to dietary Glyequi concentrations at varying CP levels. Ten male broiler chickens each were housed in 1 of 84 metabolism units. Diets with three CP levels of 16.3% (CP16.3), 14.7% (CP14.7), and 13.2% (CP13.2) each containing four Glyequi concentrations of 12, 15, 18, and 21 g/kg were used. Quantitative excreta collection was carried out from days 18–21. The reduction of dietary CP concentrations decreased average daily gain (ADG) and gain:feed ratio (G:F) from days 7–21 and increased the nitrogen-utilization efficiency (NUE). Supplementation of Glyequi increased ADG and G:F at CP13.2. The ADG at CP14.7 and G:F at CP14.7 and CP16.3 increased up to 15 g Glyequi/kg. These results indicated that the minimum to which dietary CP concentrations can be reduced in broiler chickens up to three weeks of age is between 16.3 and 14.7% when dietary Glyequi and essential AA are adequately supplied. Further, these findings showed that the growth-response of broiler chickens to dietary Glyequi is influenced by dietary CP concentrations. The second study was conducted to determine whether supplementation of single nonessential AA (neAA) can diminish or overcome the growth-decreasing effect of a diet with reduced dietary CP and neAA concentrations. Further, the effect of non-protein nitrogen supplementation in a diet with insufficient neAA concentrations was investigated. Nine male broiler chickens each were kept in 1 of 81 metabolism units. Two diets with different neAA concentrations, except Glyequi, and adequate essential AA concentrations were mixed resulting in CP levels of 17.8% (CP17.8), and 15.6% (CP15.6). The dietary Glyequi concentration was 15 g/kg in each diet. Other diets were mixed by supplementing either L-Alanine, L-Proline, L-Aspartic acid, a mix of L-Aspartic acid and L-Asparagine·H2O, L-Glutamic acid, or a mix of L-Glutamic acid and L-Glutamine to CP15.6 to achieve the respective neAA concentration of CP17.8. Ammonium chloride (NH4Cl) was added to CP15.6 to achieve the CP concentration of CP17.8. Excreta were collected quantitatively from days 18–21. Highest ADG and G:F from days 7–21 were found at CP17.8 and decreased at CP15.6. Supplementation of aspartic acid and asparagine (Asp+Asn), glutamic acid (Glu), and glutamic acid and glutamine (Glu+Gln) increased ADG and G:F to a similar extent, but not to the level of CP17.8. The NUE was highest at CP15.6, and CP15.6 supplemented with alanine, proline, and Glu. Lower NUE was observed at CP17.8 than at CP15.6 without and with neAA supplementation. Overall lowest ADG, G:F, and NUE were found upon NH4Cl supplementation. These findings showed that individual supplementation of Asp+Asn, Glu, and Glu+Gln could partly overcome the growth-reducing effect of very low CP diets. NH4Cl was found unsuitable to increase growth. The aim of the third study was to investigate interactive effects among dietary Glyequi, cysteine (Cys), and choline (Cho) on the growth of broiler chickens. Ten male broiler chickens each were housed in 105 metabolism units. Excretion of N was determined from days 18–21. Five levels each of dietary Glyequi, Cys, and Cho were tested in 15 dietary treatments. Another diet was provided to 15 birds each in another 5 metabolism units to measure prececal AA digestibility. The G:F from days 7–21 increased with digestible Glyequi intake. Differences between low- and high-digestible Cys intake were low. Hardly any effect of Cho intake on G:F was found compared to digestible intake of Glyequi and Cys. The NUE was very high with low variation among treatments. These results showed that the interactive effects among dietary Glyequi, Cys, and Cho on growth were slightly pronounced. This was likely an effect of high NUE and its low variation that caused the Glyequi requirement to be low. In conclusion, the lowest level to which dietary CP for broiler chickens up to three weeks of age can be reduced is between 16.3 and 14.7%. The growth-decreasing effect of a diet with reduced neAA concentrations can be slightly overcome upon supplementation of Asp+Asn, Glu, and Glu+Gln. Moreover, dietary CP concentrations and the related amounts of excreted N influenced the response of broiler chickens to dietary Glyequi.Publication Nitrogen dynamics in organic and conventional farming systems in the sub-humid highlands of central Kenya(2019) Musyoka, Martha; Cadisch, GeorgNitrogen (N) deficit is one of the limiting factors to food security in most developing countries while the excessive use of N has resulted in environmental contamination. Timely N availability, at the right rate is crucial to improving crop yield and N use efficiency in farming systems. Therefore, understanding nitrogen dynamics under different farming systems is essential to improve N use and recovery efficiencies of crops and in addressing environmental impacts associated with increased use of inorganic and organic inputs. This study focused on N dynamics in conventional (Conv) and organic (Org) farming systems as practiced by small scale farmers (at ∼50 kg N ha−1yr−1, Low input) and at recommended levels of input (∼225 kg N ha−1yr−1, High input) for commercial use in the sub humid and humid regions of Central Kenya. Data was collected during three cropping seasons between October 2012 and March 2014 in an on-going long-term trial established since 2007 at Chuka and at Thika sites located in central highlands of Kenya. Mineral N-based fertilizer and cattle manure were applied in Conv-High and Conv-Low while composts and other organic inputs were applied at similar N rates for Org-High and Org-Low. Farming systems were laid down in a randomized complete block design with 4 and 5 replications at Chuka and Thika respectively. The trial follows a 2 season-three-year crop rotation envisaging maize, legumes, vegetables and potatoes. N mineralization was studied using a modified buried bag approach while N loss was measured using Self-Integrating Accumulator (SIA) cores. N synchrony was assessed using daily N flux differences constructed as daily N release minus daily N uptake at different stages of the crops. N uptake was assessed at various stages of the crop through destructive sampling while nitrogen use efficiency (NUE) was assessed at harvest. Surface N balances were constructed using N applied as inputs, N deposition via rainfall, biological N fixation and crop yield and biomass as outputs. Out of the total N applied from inputs, only 61, 43 and 71 % was released during potato, maize and vegetable seasons respectively. Farming systems did not show a major impact in their influence on N synchrony, i.e. matching N supply to meet N demand. Rather the N synchrony varied with crop and N demand stages. Positive N flux differences were observed (higher N release compared to N demand) during the initial 20-30 days of incubation for all the farming systems, and negative N flux differences (higher N demand than release) at reproductive stages of the crops. Nitrogen uptake efficiency (NUpE) of potato was highest in Conv-Low and Org-Low at Thika and lowest in Org-High and Org-Low at Chuka where late blight disease affected potato performance. In contrast, NUpE of maize was similar in all systems at Chuka site, but was significantly higher in Conv-High and Org-High compared to the low input systems at Thika site. The NUpE of cabbage was similar in Conv-High and Org-High while the NUpE of kale and Swiss chard were similar in the low input systems. Potato N utilization efficiencies (NUtE) and agronomic efficiencies of N use (AEN) in Conv-Low and Conv-High were higher than those from Org-Low and Org-High, respectively. The AEN of maize was similar in all the systems at Chuka but was higher in the high input systems compared to the low input systems at the site in Thika. The AEN of vegetables under conventional systems were similar to those from organic systems. Both conventional and organic systems lost substantial amounts of mineral-N into lower soil horizons before crop establishment (0-26 days). Cumulative NO3--N leached below 1 m was similar in all the farming systems but was higher at the more humid Chuka site compared to Thika site during the maize season. Significantly more N was leached during potato season compared to maize and vegetable seasons. When NO3--N leached was expressed over total N applied, 63-68% more NO3--N was leached from the low input systems compared to the high input systems. Org-High showed a positive partial N balance at both sites and in all the cropping systems except during the vegetable season at Chuka. All the other systems exhibited negative partial N balances for the three cropping seasons with exception of Conv-High during potato season and Conv-Low and Org-Low during vegetable season at Thika site. In summary, organic and conventional had similar effects on N release, synchrony and N loss through leaching. Furthermore, more N was leached (when expressed as a fraction of N applied) during potato and vegetables cropping seasons in the low input systems compared to the high input systems. In addition, conventional and organic farming systems had similar effects on NUpE, AEN, NUtE and NHI for maize and vegetables, while conventional systems improved NUE of potato compared to organic systems. The research therefore concludes that organic and conventional farming systems at high input level are viable options of increasing food security in sub-Saharan Africa (SSA) for maize and vegetables as demonstrated by similar yields, NUE, N supply and loss. Ability to meet food security in conventional and organic system at low input is hampered by high N losses, negative N balances coupled with low productivity due to biotic and abiotic stresses. In both conventional and organic systems, there is a need to reduce N application at planting and increase N applied at reproductive stages to minimize potential loss during the initial 20-30 days after application and improve N supply midseason when crop demand is high. Since organic systems depend on organic inputs, there is a critical need to improve the quality of manure, composts and other organic inputs to improve N supply and availability.Publication The effects of rumen nitrogen balance on nutrient digestion, protein metabolism, and performance of dairy cows as influenced by diet composition(2021) Kand, Deepashree Dilip; Dickhöfer, UtaFeeding excess dietary crude protein (CP) beyond the requirements of dairy cattle and microbes in the rumen increases production costs for farmers, excretion of nitrogen (N) to the environment, and has negative effects on the cows’ health and reproductive performance. Researchers have been interested in exploring the effects that diets with negative rumen nitrogen balance (RNB) may have on the dairy cattle and their rumen function. Results so far have been inconsistent may be due to the performance level of the animal with high-yielding dairy cows being more sensitive than low performing ones. Moreover, it may be supposed that variable responses to negative RNB in different studies may at least partly be related to varying ingredient composition and the type of main carbohydrate or N sources in the animals’ diets. The overall objective of the thesis was to generate a comprehensive understanding on the effects of interactions between the RNB levels and carbohydrate and N sources in cattle diets on rumen fermentation, the efficiency of microbial CP synthesis, and on N use efficiency in vitro and in vivo. The results of the present thesis indicate that the effects of negative RNB levels may vary with dietary composition in dairy cows. Therefore, outlining a single minimum RNB balance threshold for dairy cattle diets may not be appropriate when optimizing N utilization in dairy cows, because several animal and dietary factors modify the requirements of rumen microbes.Publication Variation and estimation of nitrogen utilization efficiency in a crossbred pig population(2022) Berghaus, Daniel; Rodehutscord, MarkusEfficient utilization of dietary nitrogen (N) in pork production is of increasing concern. Previous studies revealed that a genetic basis for N utilization efficiency (NUE) might exist, but to assess the potential of breeding for improved NUE, the between-animal variation of a large number of animals needs to be known. The standard method to determine N retention (NR) in balance trails is laborious and not feasible for the required numbers of animals. However, correlations between protein utilization and blood urea nitrogen (BUN) concentration have been shown to exist and body protein turnover is subject to hormonal control. Hence, the objective of the present thesis was to quantify NR of growing pigs at two different growth stages by N balance and to determine the impact of body protein turnover on NUE. In addition, equations for the estimation of NR were established, using performance data and blood metabolite concentrations, which were applied to evaluate the variation in NUE of a F1 crossbred population. Over a period of 2.5 years, a total of 508 crossbred pigs (German Landrace x Pietrain) from 20 different boars was investigated from the 11th week of life until slaughter. The pigs were housed individually throughout the experimental period and a two-phase fattening was performed. All animals received the same diet for ad libitum intake which was formulated to contain 90% of the recommended lysine concentration so that marginal lysine supply was the limiting factor for protein retention and pigs were allowed to express their full genetic potential of NUE. In both fattening phases, daily feed intake was recorded for each animal in a five-day sampling period (SP), and blood samples were taken from the jugular vein at around 13:00 h on three consecutive days for determination of BUN, cortisol, and insulin-like growth factor 1 (IGF-I) concentration. Additionally, in both SP, N balance was performed in the same experimental barn on a randomly selected subsample of 56 barrows. The barrows were housed in metabolism crates for six days, two days for adaption and four days for quantitative collection of feces and urine. Simultaneously, their body protein turnover was determined using the end-product method after a single oral dose of 15N-labeled glycine. Based on the N balance results, models for estimation of NR were obtained by multiple regression of performance data and blood metabolite concentrations. The significance of the variables was validated using a bootstrapping method to avoid overfitting the models to the observed data. The goodness of fit of the equations was assessed using the coefficient of determination and the root mean square error. The N balance results revealed a high protein retention potential of the animals, which did not differ on average between the two SP. However, large differences in NR were observed between individuals and NR was strongly correlated with N and lysine intake. NUE was also at a high level and varied considerably between individuals. The mean NUE was significantly higher in SP1 than in SP2 and a moderate correlation was observed between NR and NUE. The mean body protein turnover did not differ between the SP and no correlation with NUE was observed. In estimating NR, the model with the best goodness of fit included the variables initial body weight, average daily gain, average daily feed intake, N intake, BUN, cortisol, and IGF-I concentration. This model was used to estimate NR for all animals and subsequently calculate their NUE. Describing NR as a linear function of lysine intake across both SP showed an average marginal efficiency of lysine utilization for protein retention of 67%. Despite a wide variation in NUE within the offspring of the same boars, significant differences were found between the offspring groups of the boars. Under the prevailing circumstances of marginal lysine supply, the NR of fattening pigs could be estimated from performance data and blood metabolite concentrations with satisfying accuracy. This provides a fast and reliable alternative to performing N balance studies, reducing the experimental effort considerably in studies with large numbers of animals. Although lysine supply was the limiting factor for protein retention, only about 70% of the variation in NR could be explained by the level of lysine intake. The remaining part of the variation was likely caused by differences in the intermediary lysine utilization or differences in the lysine content of the retained body protein between individuals. About 50% of the variation in NUE could be explained by differences in the level of NR, implying that pigs with higher protein retention potential utilized dietary N more efficiently. However, this was not accompanied by differences in body protein turnover. Phenotyping of the F1 crossbred population revealed a large variation between individuals and a significant boar effect, indicating the possibility of improving NUE through breeding measures.