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Nitrogen use efficient (NUE) wheat varieties have potential to reduce input costs for growers, limit N runoff into water ways, and increase wheat adaptability to warmer environments. Previous studies have done little to explain the genetic basis for NUE and components, nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE). Four studies were conducted to 1) determine genotypic stability of NUE under high and low N regimes and under warming 2) determine effect of warming on NUE 3) indentify QTL associated with NUE components 4) assess the utility of canopy spectral reflectance (CSR) as a high-throughput phenotyping device for NUE. Genotypic response to N stress or warming varied. Uptake efficiency was found to be more important than utilization efficiency to genotypic performance under high and low N environments and under warming. Selection under low N for NUpE and under high N for NUtE most efficiently identified NUE varieties. Uptake and utilization were lower under warming due to quickened development. No strong correlations between the CSR indices and NUE existed. No QTL were found to be significantly associated with NUE components. Further research into the mechanisms controlling NUE and to reveal plant response to N stress and under warming is necessary.

O suprimento inadequado de nutrientes em pastagem influencia diretamente na produtividade da planta. A eficiência de utilização de nitrogênio (EUN) é definida como a quantidade em kg de MS produzida por kg de nitrogênio aplicado. A EUN é influenciada por fatores de temperatura e disponibilidade hídrica. O objetivo geral do trabalho foi definir critérios agroclimáticos para recomendação de épocas para adubação nitrogenada de Urochloa brizantha cv. Marandu na região de São Paulo. Com base na literatura foram definidas três classes de expectativa de resposta à adubação: alta, moderada e baixa. Estas classes foram relacionadas a critérios térmicos e hídrico, definidos a partir de dados de literatura e de modelagem matemática. O modelo APSIM (Agricultural Production System Simular) foi utilizado para estimar a eficiência de uso de N em quatro cidades do Estado de São Paulo com climas contrastantes. Em seguida, os dados foram relacionados à temperatura média diária e foram definidos os critérios térmicos relacionados à expectativa de resposta à adubação. A relação entre armazenamento relativo de água e produção relativa de Urochloa brizantha cv. Marandu, obtida a partir de dados de literatura, foi utilizada para definição dos critérios hídricos. A adubação nitrogenada em cada período foi classificada em \"recomendada\" ou \"não recomendada\", a partir da combinação entre os critérios de disponibilidade de água e temperatura. Os dados de armazenamento relativo de água no solo e temperatura média de Itapetininga, São Carlos, São José do Rio Preto e Araçatuba foram submetidos à análise estatística descritiva. Os períodos nos quais havia probabilidade igual ou superior a 80% de ocorrer a condição \"recomendada\" foram considerados adequados para adubação nitrogenada. A expectativa de resposta à adubação foi considerada alta quando a temperatura média do período era superior a 21,6°C, moderada quando a temperatura média era entre 16,7 e 21,6°C e baixa quando a temperatura média era inferior a 16,7°C. Em relação ao critério hídrico, a expectativa de resposta à adubação foi considerada alta quando o armazenamento relativo de água era superior a 0,82, moderada entre 0,82 e 0,62 e baixa quando o armazenamento era inferior a 0,62. As épocas para adubação nitrogenada foram diferentes nas cidades em estudo devido a diferenças climáticas entre elas. De dezembro a março foram os meses recomendados para adubação em Araçatuba, outubro a fevereiro para Itapetininga. Em São José do Rio Preto a adubação nitrogenada deve ser recomendada a partir de dezembro. Entre março e abril, o risco associado ao critério hídrico é um pouco mais elevado, voltando a diminuir em maio. Entre junho e novembro a adubação nitrogenada não é recomendada em São José do Rio Preto. Em São Carlos a melhor época para adubação nitrogenada é de novembro a maio. Modelo APSIM não simulou adequadamente a produtividade de Urocloa brizantha cv. Marandu, principalmente em sistema sem adição de nitrogênio. A definição de critério relacionados a temperatura e disponibilidade de água possibilitou a identificação de épocas para recomendação de adubação nitrogenada em função da expectativa de resposta de Urocloa brizantha cv. Marandu visando as maiores eficiências de utilização de nitrogênio e sustentabilidade dos sistemas de produção animal / Inadequate grazing nutrient supply directly influences plant productivity. The nitrogen utilization efficiency (EUN) is defined as the amount in kg of DM produced per kg of nitrogen applied. EUN is influenced by temperature factors and water availability. The general objective of the work was to define agroclimatic criteria for the recommendation of nitrogen fertilization periods of Urochloa brizantha cv. Marandu in the region of São Paulo. Based on the literature, three classes of expectation of response to fertilization were defined: high, moderate and low. These classes were related to thermal and water criteria, defined from literature data and mathematical modeling. The APSIM (Agricultural Production System Simulate) model was used to estimate the efficiency of N use in four cities of the State of São Paulo with contrasting climates. The data were then related to the average daily temperature and the thermal criteria related to the expected response to fertilization were defined. The relationship between relative water storage and relative yield of Urochloa brizantha cv. Marandu, obtained from literature data, was used to define the water criteria. Nitrogen fertilization in each period was classified as \"recommended\" or \"not recommended\", based on the combination of water and temperature availability criteria. The data of relative water storage in the soil and average temperature of Itapetininga, São Carlos, São José do Rio Preto and Araçatuba were submitted to descriptive statistical analysis. The periods in which there was a probability equal to or greater than 80% of the \"recommended\" condition were considered adequate for nitrogen fertilization. The expected response to fertilization was considered high when the mean temperature of the period was higher than 21.6°C, moderate when the average temperature was between 16.7 and 21.6°C and low when the average temperature was below 16.7°C. Regarding the water criterion, the expectation of response to fertilization was considered high when the relative water storage was higher than 0.82, moderate between 0.82 and 0.62 and low when storage was less than 0.62. The seasons for nitrogen fertilization were different in the cities under study due to climatic differences between them. From December to March were the months recommended for fertilization in Araçatuba, October to February for Itapetininga. In São José do Rio Preto nitrogen fertilization should be recommended as of December. Between March and April, the risk associated with the water criterion is slightly higher, decreasing again in May. Between June and November nitrogen fertilization is not recommended in São José do Rio Preto. In São Carlos, the best season for nitrogen fertilization is from November to May. Model APSIM did not adequately simulate the productivity of Urocloa brizantha cv. Marandu, mainly in system without addition of nitrogen. The definition of criteria related to water temperature and availability made it possible to identify times for nitrogen fertilization recommendation as a function of the expected response of Urocloa brizantha cv. Marandu aiming at greater nitrogen utilization and sustainability efficiencies of animal production systems.

O suprimento inadequado de nutrientes em pastagem influencia diretamente na produtividade da planta. A eficiência de utilização de nitrogênio (EUN) é definida como a quantidade em kg de MS produzida por kg de nitrogênio aplicado. A EUN é influenciada por fatores de temperatura e disponibilidade hídrica. O objetivo geral do trabalho foi definir critérios agroclimáticos para recomendação de épocas para adubação nitrogenada de Urochloa brizantha cv. Marandu na região de São Paulo. Com base na literatura foram definidas três classes de expectativa de resposta à adubação: alta, moderada e baixa. Estas classes foram relacionadas a critérios térmicos e hídrico, definidos a partir de dados de literatura e de modelagem matemática. O modelo APSIM (Agricultural Production System Simular) foi utilizado para estimar a eficiência de uso de N em quatro cidades do Estado de São Paulo com climas contrastantes. Em seguida, os dados foram relacionados à temperatura média diária e foram definidos os critérios térmicos relacionados à expectativa de resposta à adubação. A relação entre armazenamento relativo de água e produção relativa de Urochloa brizantha cv. Marandu, obtida a partir de dados de literatura, foi utilizada para definição dos critérios hídricos. A adubação nitrogenada em cada período foi classificada em \"recomendada\" ou \"não recomendada\", a partir da combinação entre os critérios de disponibilidade de água e temperatura. Os dados de armazenamento relativo de água no solo e temperatura média de Itapetininga, São Carlos, São José do Rio Preto e Araçatuba foram submetidos à análise estatística descritiva. Os períodos nos quais havia probabilidade igual ou superior a 80% de ocorrer a condição \"recomendada\" foram considerados adequados para adubação nitrogenada. A expectativa de resposta à adubação foi considerada alta quando a temperatura média do período era superior a 21,6°C, moderada quando a temperatura média era entre 16,7 e 21,6°C e baixa quando a temperatura média era inferior a 16,7°C. Em relação ao critério hídrico, a expectativa de resposta à adubação foi considerada alta quando o armazenamento relativo de água era superior a 0,82, moderada entre 0,82 e 0,62 e baixa quando o armazenamento era inferior a 0,62. As épocas para adubação nitrogenada foram diferentes nas cidades em estudo devido a diferenças climáticas entre elas. De dezembro a março foram os meses recomendados para adubação em Araçatuba, outubro a fevereiro para Itapetininga. Em São José do Rio Preto a adubação nitrogenada deve ser recomendada a partir de dezembro. Entre março e abril, o risco associado ao critério hídrico é um pouco mais elevado, voltando a diminuir em maio. Entre junho e novembro a adubação nitrogenada não é recomendada em São José do Rio Preto. Em São Carlos a melhor época para adubação nitrogenada é de novembro a maio. Modelo APSIM não simulou adequadamente a produtividade de Urocloa brizantha cv. Marandu, principalmente em sistema sem adição de nitrogênio. A definição de critério relacionados a temperatura e disponibilidade de água possibilitou a identificação de épocas para recomendação de adubação nitrogenada em função da expectativa de resposta de Urocloa brizantha cv. Marandu visando as maiores eficiências de utilização de nitrogênio e sustentabilidade dos sistemas de produção animal / Inadequate grazing nutrient supply directly influences plant productivity. The nitrogen utilization efficiency (EUN) is defined as the amount in kg of DM produced per kg of nitrogen applied. EUN is influenced by temperature factors and water availability. The general objective of the work was to define agroclimatic criteria for the recommendation of nitrogen fertilization periods of Urochloa brizantha cv. Marandu in the region of São Paulo. Based on the literature, three classes of expectation of response to fertilization were defined: high, moderate and low. These classes were related to thermal and water criteria, defined from literature data and mathematical modeling. The APSIM (Agricultural Production System Simulate) model was used to estimate the efficiency of N use in four cities of the State of São Paulo with contrasting climates. The data were then related to the average daily temperature and the thermal criteria related to the expected response to fertilization were defined. The relationship between relative water storage and relative yield of Urochloa brizantha cv. Marandu, obtained from literature data, was used to define the water criteria. Nitrogen fertilization in each period was classified as \"recommended\" or \"not recommended\", based on the combination of water and temperature availability criteria. The data of relative water storage in the soil and average temperature of Itapetininga, São Carlos, São José do Rio Preto and Araçatuba were submitted to descriptive statistical analysis. The periods in which there was a probability equal to or greater than 80% of the \"recommended\" condition were considered adequate for nitrogen fertilization. The expected response to fertilization was considered high when the mean temperature of the period was higher than 21.6°C, moderate when the average temperature was between 16.7 and 21.6°C and low when the average temperature was below 16.7°C. Regarding the water criterion, the expectation of response to fertilization was considered high when the relative water storage was higher than 0.82, moderate between 0.82 and 0.62 and low when storage was less than 0.62. The seasons for nitrogen fertilization were different in the cities under study due to climatic differences between them. From December to March were the months recommended for fertilization in Araçatuba, October to February for Itapetininga. In São José do Rio Preto nitrogen fertilization should be recommended as of December. Between March and April, the risk associated with the water criterion is slightly higher, decreasing again in May. Between June and November nitrogen fertilization is not recommended in São José do Rio Preto. In São Carlos, the best season for nitrogen fertilization is from November to May. Model APSIM did not adequately simulate the productivity of Urocloa brizantha cv. Marandu, mainly in system without addition of nitrogen. The definition of criteria related to water temperature and availability made it possible to identify times for nitrogen fertilization recommendation as a function of the expected response of Urocloa brizantha cv. Marandu aiming at greater nitrogen utilization and sustainability efficiencies of animal production systems.

An improved understanding of nitrogen metabolism in the gastrointestinal tract of the pig is required in order to provide accurate estimates of nitrogen and amino acid (AA) bioavailability in feed ingredients and for adequate diet formulation. Research objectives were to estimate the extent of fermentative AA catabolism (FAAC) in the upper gut of pigs. Further objectives were to determine the impact of lower gut nitrogen absorption on measures of apparent ileal digestibility of AA and nitrogen, whole-body nitrogen balance, and urea kinetics in pigs fed a valine-limiting diet. It was determined that simple isotope dilution calculations are inappropriate for determining ileal ammonia flux and FAAC from a continuous infusion of labelled ammonia and urea. A static model with two-pools (blood urea and digesta ammonia) was then developed to determine possible value ranges for FAAC in the upper gut of pigs. Maximum estimated FAAC based on this model was lower when dietary protein content was decreased (P < 0.001). The model presented is limited to minimum and maximum estimates of FAAC due to the sampling and isotope infusion protocol used. Refinements to the model and experimental protocol could allow for more accurate estimates of FAAC. Infusion of casein or urea into the lower gut of pigs did not affect measures of apparent ileal digestibility of AA or nitrogen. These results further validate the methodology available for determination of ileal digestibility and the use of ileal digestibility to estimate bioavailability of AA and nitrogen. Infusion of casein or urea into the lower gut resulted in an increase in nitrogen balance and urea flux in growing pigs fed a valine-limiting diet. Nitrogen absorbed from the lower gut of pigs is likely in the form of ammonia which is converted to urea. Lower gut nitrogen can contribute to whole-body protein deposition via urea recycling and microbial AA production in the upper gut. Lower gut nitrogen absorption should be accounted for when estimating bioavailability of nitrogen in feeds and foods. / Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA); Ontario Pork; Canadian Swine Research and Development Cluster; Natural Sciences and Engineering Research Council of Canada (NSERC); Evonik Industries AG

The objective of this experiment was to determine if nutrient utilization and energy partitioning by lactating dairy cows would differ in response to dietary corn grain (CG) types [steam-flaked corn (SFC) vs. high-moisture corn (HMC)] and to test if the types of CG would interact with slow-release urea (SRU) on lactational performance and energy utilization. Eight multiparous Holstein cows (32 ± 8.2 days-in-milk) were used in a duplicated 4 × 4 Latin square with one square consisting of ruminally cannulated cows. A 2 × 2 factorial arrangement was used to test 4 dietary treatments: SFC without SRU, SFC with SRU, HMC without SRU, and HMC with SRU. The experimental diets contained 60.5% dry matter (DM) of forages, whereas 12.9% or 14.4% DM of SFC or HMC was added in the diets, respectively. The SRU was supplemented at 0.46% DM, replacing a mixture of soybean meal and canola meal in a 50:50 ratio. Feeding HMC decreased intakes of DM, crude protein, and fiber compared with SFC. Supplementation of SRU did not affect intakes of DM and nutrients, whereas it tended to increase intakes of DM or increased crude protein intake under SFC but no effect under HMC, leading to CG ×SRU interactions on DM and crude protein intakes. Neither type of CG nor SRU supplementation affected milk production except that cows fed HMC-based diets tended to decrease energy-corrected milk yield compared to those fed SFC-based diets. Utilization of HMC in the diet had a tendency to increase dairy efficiency based on milk yield over SFC utilization. Cows fed HMC diets gained more body weight (BW) than those fed SFC diets, whereas supplementing SRU tended to reduce BW gain regardless of type of CG. Cows fed HMC diets shifted more net energy into BW compared with those fed SFC diets, whereas supplementing SRU tended to decrease a portion of net energy partitioned into BW gain under both SFC and HMC diets. Dietary treatments exerted minor impacts on ruminal fermentation profiles. Feeding HMC diets decreased fecal N excretion compared with SFC diets. In addition, supplementing SRU increased fecal N excretion under SFC, but it was decreased by SRU with HMC, leading to an interaction between CG and SRU. These collective results demonstrate that feeding HMC with SRU can be a practical option in high-forage lactation diets to maintain or improve nutrient and energy utilization efficiency and minimize negative environmental impacts.

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