No abstract

The Intergovernmental Panel on Climate Change methodology estimates that over 50% of total nitrous oxide (N 2 O) emissions in New Zealand derive from animal excreta-N deposited during grazing. The emission factor for excreta-N as used by this methodology has an important impact on New Zealand's total N 2 O inventory. The objectives of this study were to refine the N 2 O emission factor for urine by simultaneously measuring N 2 O emissions from 5 pastoral soils of different drainage class, in 3 different regions in New Zealand following a single application of urine; plus test various aspects of the soil cover method for determining emission factors. Cow urine and synthetic urine was applied to pastoral soils in autumn 2000 and N 2 O emissions were measured using closed flux chambers at regular intervals for 4-18 months following application. The N 2 O emission factors for cow urine estimated for the first 4 months after urine application varied greatly depending on rainfall and soil drainage class, and ranged from 0.3 to 2.5% of the urine-N applied, suggesting that adopting a single emission factor for New Zealand may be inappropriate. The largest emission factor was found in a poorly drained soil, and the lowest emission factor was found in a well-drained stony soil. Ongoing measurements on one of the soils resulted in an increase in emission factors as the N 2 O emissions had not reached background levels 4 months after urine application. To characterise urine-induced N 2 O emissions, we recommend measurements continue until N 2 O emissions from urine-amended soil return to background levels. Furthermore, we recommend using real animal urine rather than synthetic urine in studies when determining the N 2 O emission factor for urine. S R 0 2 1 2 8 N i t r o u s o x i d e e m i s s i o n f a c t o r C e c i l e A . M . d e K l e i n e t a l .

No abstract

Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-secreted factors known to be involved in regulating the proliferation and differentiation of granulosa cells during follicular growth. The aims of this study were to determine the signalling pathways used by recombinant forms of murine and ovine GDF9 and BMP15 in combination (GDF9CBMP15) and the molecular complexes formed by combinations of these factors. Differences in the molecular forms of combinations of murine and ovine GDF9CBMP15 were observed by western blot analysis. Ovine GDF9CBMP15-stimulated 3 H-thymidine uptake was completely blocked by SMAD2/3 and nuclear factor-kB pathway inhibitors and partially blocked by a p38-mitogen-activated protein kinase (MAPK) inhibitor. Thymidine uptake by murine GDF9CBMP15 was reduced by the SMAD2/3 and extracellular signal-regulated kinase-MAPK pathway inhibitors and increased after addition of a c-Jun N-terminal kinase inhibitor. Stimulation of 3 H-thymidine uptake by GDF9CBMP15 from either species was not affected by the SMAD1/5/8 pathway inhibitor. In conclusion, both murine and ovine GDF9CBMP15-stimulated thymidine incorporation in rat granulosa cells was dependent on the SMAD2/3 signalling pathway but not the SMAD1/5/8 pathway. Divergence in the non-SMAD signalling pathways used by murine and ovine GDF9CBMP15 was also evident and may be due to the differences observed in the molecular complexes formed by these factors. These results are consistent with the hypothesis that the disparate cooperative functions of GDF9 and BMP15 in different species are mediated by divergent non-SMAD signalling pathways.

Genetic relationships among six populations of Merino sheep were investigated using microsatellites. The history of the six populations is relatively well documented, with all being derived from the Spanish Merino breed within the last 400 years. Genetic variation was highest amongst the Spanish and Portuguese populations, although the preservation of genetic diversity within the other populations was high. By a variety of different statistical tests the French Mutton, German Mutton and New Zealand Merino populations could be differentiated from each other and the Iberian Merinos, indicating that microsatellites are able to track relatively recent changes in the population structure of sheep breeds. The dendrograms constructed on the basis of microsatellite allelic frequencies showed that populations that have shared selection criteria (meat vs. wool) tend to cluster together.