• Energy Research

This study aimed at assigning climate-relevant gaseous emissions from ruminants to animal- or feed-related origin. Three adult rumen-cannulated German Holstein steers and three forage types (corn silage (CS), alfalfa silage (AS) and grass hay (GH)) were used in a 3 × 3 Latin square design. Each period consisted of 12 days (d), during which animals received 10 kg dry matter/day of one forage as sole feed. Gaseous samples from forages and the steers´ rumen were taken and analyzed for CO2, CH4, and N2O using gas chromatography. There were large differences in the amounts of CO2 and N2O emitting from the forage types. Most N2O came from AS and only small amounts from GH and CS. Results indicate that fermented forages rich in nitrogen can release climate-relevant N2O. The highest CO2 amounts were measured in CS. Methane was not detected in any forage sample. Animals consuming CS showed slightly lower CH4 concentrations in the rumen gas sample than animals fed AS or GH. Big differences were found for ruminal N2O with the highest concentration after AS ingestion such that the N2O measured in the rumen seems to originate from the used feedstuff.

Leaf ascorbic acid (ASA) level is thought to be an important trait conferring stress tolerance in plants, but definite evidence regarding its effectiveness in the breeding of stress tolerant crops is lacking. Therefore, the stress response of a rice TOS17 insertion mutant (ND6172) for a GDP-D-mannose-3',5'-epimerase gene, which is involved in ASA biosynthesis, was tested. Two fumigation experiments were conducted, in which rice plants (Oryza sativa L.) were exposed to (i) high ozone for ten days at the tillering stage (100 ppb, 7 h day⁻¹); and (ii) to four different ozone concentrations ranging from charcoal filtered air to 2.5 times the ambient concentration for the entire growth season. The mutant ND6172 had around 20-30% lower ASA level than the wild-type (Nipponbare), and exhibited a moderately higher level of visible leaf symptoms due to ozone exposure. Differences in ASA level between ND6172 and Nipponbare led to differential responses of the glutathione level, and the activities of glutathione reductase, ascorbate peroxidase, and dehydroascorbate reductase. With season-long ozone fumigation, yields and yield components were not negatively affected at ambient ozone level in both genotypes, but showed stronger decreases in ND6172 at higher ozone levels, especially at 2.5 times the ambient level. Similarly, the mature straw of ND6172 exhibited a higher degree of lignification at the 2.5 times ambient ozone level. In conclusion, a difference in leaf ASA level of around 20-30% is relevant for ozone tolerance in rice at levels exceeding the current ambient ozone concentrations.

Ruminant production systems frequently rely on grassland utilization and conservation of herbage as hay or silage. Conservation affects the crude protein (CP) composition and protein value, which is particularly recognized during ensiling. The aim of the current study was to describe the effect of the conservation method on forage protein value and N utilization in dairy cows. Herbage from the same sward was cut and conserved as silage (SI), barn-dried hay (BH), or field-dried hay (FH). Laboratory evaluation indicated differences in CP fractions and ruminal degradability of CP. Conserved forages were fed to six lactating Holstein cows in a replicated 3 × 3 Latin square design, and N balance was assessed. Partitioning of N into milk, feces, and urine was affected only moderately. Lower concentrations of serum, milk, and also urinary urea indicated lower N turnover for FH compared to SI and BH, likely due to lower N intake for FH. However, the use efficiency of feed N for milk N did not differ between the types of forage. Further, high CP concentrations and the unbalanced concentrations of CP and energy in the forages led to excess excretion of N in all treatments and presumably superimposed effects of the conservation method on N utilization.

Extensive experimentation on individual animals in respiration chambers has already been carried out to evaluate the potential of dietary changes and opportunities to mitigate CH4 emissions from ruminants. Although it is difficult to determine the air exchange rate of open barn spaces, measurements at the herd level should provide similarly reliable and robust results. The primary objective of this study was (1) to define a validity range (data classification criteria (DCC)) for the variables of wind velocity and wind direction during long-term measurements at barn level; and (2) to apply this validity range to a feeding trial in a naturally cross-flow ventilated dairy barn. The application of the DCC permitted quantification of CH4 and NH3 emissions during a feeding trial consisting of four periods. Differences between the control group (no supplement) and the experimental group fed a ration supplemented with condensed Acacia mearnsii tannins (CT) became apparent. Notably, CT concentrations of 1% and 3% of ration dry matter did not reduce CH4 emissions. In contrast, NH3 emissions decreased 34.5% when 3% CT was supplemented. The data confirm that quantification of trace gases in a naturally ventilated barn at the herd level is possible.