Martin Upsdell

We used a previously developed simulation model of a plant cell wall and its enzymatic degradation to compare the abilities of two hemicelluloses, glucuronoarabinoxylan (GAX) and xyloglucan (XG), to protect cellulose microfibrils (CMFs) from attack by cellulose-degrading enzymes. Additionally, we investigated the effect of XG abundance on the degradation rate of CMFs in the presence of the same enzymes. Simulations were run using hypothetical cell-wall compositions in which the numbers and arrangement of CMFs and (1,3;1,4)-β-glucan were kept constant, but the proportions of GAX and XG were altered. Scenarios considered walls with low and equal proportions of either GAX or XG, and also low, medium and high proportions of XG in the absence of GAX. The rate of CMF degradation was much lower in walls with GAX than walls with XG, except for early in the simulation when the reverse held, suggesting that XGs were protecting CMFs by competitive inhibition. Increasing XG content reduced both the degradation rate of CMFs and the percent of XG degraded, indicating that activity of enzymes decreased with XG density despite XG being degradable. Glucose oligosaccharide breakdown products were analysed on the basis of the originating polysaccharide and their degree of polymerisation (DP). The presence of GAX as opposed to equal amounts of XG had some significant effects on the amount and profile of breakdown products from XG and CMFs.

Research has shown a technical description of a blend for most woollen carpet applications can be met with objective measurements, namely mean fibre diameter, fibre length after carding, wool bulk, proportion of medullation, base colour and vegetable matter content. The compressional property of wool as reflected in bulk is strongly related to mean fibre diameter and mean fibre curvature. Both these measurements can now be measured simultaneously with recently developed electronic instrumentation. While the processing implications of changes in mean fibre diameter are well understood, the processing implications of changes in objectively measured mean fibre curvature have not been investigated in detail. A total of 360 New Zealand Romcross type fleeces shorn from yearling sheep, with an individual range in mean fibre diameter of 23.2–40.6 μm and an individual range in mean fibre curvature of 34–115°/mm were used. The individual fleeces were sorted to create five, similar-sized, wool-processing lines with the following specifications for mean fibre diameter and mean fibre curvature. Lot 1: low fibre diameter/high fibre curvature (30.2 μm, 72°/mm); Lot 2: high fibre diameter/high fibre curvature (33.5 μm, 70°/mm); Lot 3: medium fibre diameter/medium fibre curvature (32.1 μm, 64°/mm); Lot 4: low fibre diameter/low fibre curvature (31.1 μm, 58°/mm); and Lot 5: high fibre diameter/low fibre curvature (34.5 μm, 51°/mm). Each processing lot was scoured, combed to reduce the proportion of short fibre within each lot and spun into yarn on the semi-worsted system. Mean spindle speed at break (50 fibres in cross-section) and yarn breaking load were greatest for Lot 4 and lowest for Lot 2. Increasing fibre diameter and increasing fibre curvature resulted in less unevenness within the yarn and a decrease in neps. Coarse highly crimped fibre produced the bulkiest yarn while the finer straighter fibre produced the lowest bulk yarn. Potential wearability of knitted garments using yarn spun from each processing lot was assessed using standard knitted squares. Increasing fibre diameter and increasing fibre curvature resulted in greater relaxation shrinkage in length, while decreasing fibre diameter and increasing fibre curvature resulted in increased extensibility in width. Overall resistance to felting shrinkage increased as crimp and diameter increased. There was no difference in pilling between the processing lots. The presented results indicate that increasing fibre curvature in Romcross type sheep as may occur through selection or crossbreeding associated with improving lamb production, will have a beneficial effect on the performance of products made from their wool.

Intensification of pastoral agriculture has led to increased N losses to the wider environment. This has led to an emphasis on improving our understanding of soil N dynamics, and development of management practices which mitigate N losses. The natural abundance of the stable isotope δ ¹⁵ N relative to ¹⁴ N (δ ¹⁵ N) in soils can provide an integrated measure of past N cycle processes, and in particular soil δ ¹⁵ N can reflect past N losses, because during most N transformation processes ¹⁴ N is preferentially lost. We therefore hypothesized that pastoral soils under intensive management regimes (with high N inputs, cycling, and loss) would become progressively enriched with ¹⁵ N relative to soils under less intensive management. To test this hypothesis we analyzed archived surface soils from two long‐term grazed field trials in New Zealand, where different rates of irrigation and superphosphate fertilizer had been applied for ∼50 yr. In all treatments except one (a control treatment receiving no fertilizer), δ ¹⁵ N increased with time and the increase was greater in treatments receiving more superphosphate or irrigation (average increases ranged from ∼0.015–0.034 ‰ yr ^–1 ). Pasture production and grazing intensity also increased with increasing fertilizer rate and irrigation frequency, and we found positive correlations between the average rate of change in soil δ ¹⁵ N, and total pasture production ( r ² = 0.77, p = 0.02), clover production ( r ² = 0.95, p < 0.001), and calculated N losses ( r ² = 0.98, p < 0.001) over ∼50 yr. We suggest that most of the difference in δ ¹⁵ N observed between treatments was due to the influence fertilizer and irrigation had on pasture production, and the resulting effects this had on isotope fractionating N loss processes. Soil δ ¹⁵ N could therefore be a useful indicator of past management intensity and N cycling and loss from pastoral systems.

We determined decadal changes in soil carbon (C) and nitrogen (N) due to different irrigation regimes and phosphorus fertilization of pastures. Archived soil samples (0–75 mm) collected annually from two long‐term trials in New Zealand were analyzed for %C and %N from three P input treatments (ranging from 0 to 376 kg superphosphate ha ⁻¹ yr ⁻¹ , 1952–2009) and three irrigation treatments (unirrigated and irrigated when soil moisture content fell below either 10 or 20%, 1959–2002). In the fertilizer trial, soil C increased linearly from 2.7 to 4.2%, and there was no difference in rates of increase in C between treatments, despite much greater aboveground production when P was added. This lack of difference was attributed to higher stocking rates on treatments with higher production, and to the possibility that root inputs (which differed less between treatments) was a more important control of soil C accumulation. Nitrogen (%) was lower in the unfertilized than fertilized treatments due to lower clover N fixation, which was constrained by P availability. Soil C (%) was significantly greater in the unirrigated treatment than the irrigated treatments throughout the trial. Aboveground production was much greater in the irrigated than dryland treatment but root biomass was lower. Irrigation must have increased C and N losses, possibly via increased respiration rates during seasonally dry periods. Our study showed that P fertilizer application did not result in an increase in surface soil C and that flood irrigation resulted in a constrained increase in surface soil C content.

Much of the nitrogen (N) excreted by grazing animals is within highly concentrated urine patches. The N that is not used by plants is likely to be lost through leaching, emitted as N gases or added to the soil organic N pool. The present study used custom-made global positioning system (GPS) and urine sensors on 20 non-lactating ewes and 20 non-lactating beef heifers grazing steep hill country to determine potential critical source areas for N loss to the environment. Bite counters on four sheep and five heifers showed when and where animals were eating. Animals were monitored simultaneously on 0.5 ha adjacent paddocks over 8 days. Sheep and cows urinated a mean (±s.d.) of 21.2 ± 6.1 and 9.0 ± 3.0 times/day, respectively. Eating started soon after sunrise and increased during the day to reach a maximum in the hour before sunset, after which the eating activity of both species was near zero for most of the night, except for a short feeding period at around 0300 hours. The urination frequency of sheep increased as eating activity increased during the day, but this relationship was not seen in heifers. Land classified as easy hill country (=12°) comprised 31% of the sheep paddock and contained 23% of the urination events. In contrast, although the easy hill country comprised 33% of the cattle paddock, 46% of the urine patches were in this area. Although aerial application of N mitigation products to whole paddocks or farms is uneconomic, the results of the present study suggest that mitigation products could possibly be cost-effectively targeted to easy contoured, cattle-grazed hill country areas accessible by farm vehicle.

Comparison of DNA samples at different points of a supply chain offers a powerful means of verifying tracing systems for primal cuts of meat. However, this approach is problematic for products made...

The impact of nutrition on lactation can be separated into acute effects, affecting day-to-day yield, and chronic effects, which govern the persistency of lactation and rate of decline of the lactation curve. A mathematical model of the mammary gland was constructed to investigate both acute and chronic effects. Mammary growth is expressed in terms of the dynamics of populations of active (secreting) and quiescent (engorged) alveoli. The secretion rate of active alveoli is expressed in terms of the energy status of the dam. The model was fitted to data from a 2 x 2 factorial trial in which lactation curves were measured for heifers of two different genotypes (North American and New Zealand Holstein-Friesians) fed two different diets [grass and total mixed rations (TMR)]. Total formation of alveoli during pregnancy and lactation was statistically the same across all groups despite differences between diets, in the rate of formation of alveoli at parturition. The senescence rate of alveoli was significantly higher for heifers fed grass compared with heifers fed TMR, which corresponds to better persistency for heifers fed TMR. Heifers fed TMR had a higher rate of reactivation of quiescent alveoli than heifers fed grass, which also contributes to increased persistence for heifers fed TMR. There was a genotype x diet interaction in the rate of quiescence of active alveoli: the North American-Grass group had a higher rate of quiescence than the other three groups, perhaps reflecting differences in selection pressures between the New Zealand and North American genotypes.

Accumulation of phosphorus was investigated in the substrata and surface deposits of pilot-scale gravel-bed constructed wetlands after 2 (planted and unplanted) and 5 (planted only) years operation. Four different hydraulic loading rates of farm dairy wastewaters provided mean cumulative total P (TP) loadings ranging from ~520 to 2000 g m⁻² after 5 years operation. Mean substratum TP accumulations after 2 years operation ranged from 52 to 100 g m⁻² in the planted wetlands and from 40 to 51 g m⁻² in the unplanted wetlands, both showing a general increase with wastewater loading. After S years operation, associated with declining wetland TP removal performance, substratum TP accumulations in all the planted wetlands converged at similar values of 115 to 128 g m⁻². This represented 6 to 23% of their cumulative loadings.