Association of fertility with group mating behavior in ewes.

It was hypothesized that values for fertility variables would vary with number of rams ewes mated with in a group mating management system. In Experiment 1, for adult ewes (n = 872) joined with rams for 35-38 days, 19.0 ± 2.2 %, 19.2 ± 3.5 %, 34.4 ± 1.3 % and 27.4 ± 3.3 % were marked by zero, one, two or three rams during the first 17 days, respectively. In general, as number of rams with which ewes mated increased, number of lambs born (NLB) increased, however, ovulation rate (OR) did not. In mated ewes, embryo survival (ES) increased (P < 0.05) as number of rams with which ewes mated increased. In Experiment 2, ewes that mated with zero or one ram had lesser concentrations of estradiol than ewes that mated with two or three rams when evaluated 30 h after initiation of the follicular phase. Following breeding on the subsequent estrus, number of fetuses at mid-gestation was less in ewes that had mated, in the previous estrus, with zero or one ram compared to two or three rams. In summary, ewes mating with a larger number of rams had greater values for the fertility variables that were evaluated compared with those mating with fewer rams. When ewes mated with fewer rams during the estrous period there were lesser concentrations of estradiol, potentially associated with the decreased ES.

Variability of Escherichia coli Concentrations in Rivers during Base-Flow Conditions in New Zealand.

concentrations in rivers are known to vary considerably. Much research has focused on storm events and the relationships between fecal microbe concentrations and flows. However, there is still considerable variability in microbial concentrations during base-flow conditions, and little research has been conducted to understand this short-term variability in rivers. We investigated the variability of concentrations in base flows at the time scales of minutes, hours, and days and compared this to variability from laboratory replication of the measurement methods. This was conducted in three different-sized rivers in both summer and winter seasons. Estimates of variability were analyzed using the coefficient of variation (CV). The variability at the minute time scale was 17%, compared with the laboratory replication variability of 15%. The CV then increased to approximately 32 and 60% at the hourly and daily time scales, respectively. There is strong evidence that both time scale ( < 0.001) and river ( < 0.001) significantly affect the variation in concentrations. The concentrations were higher in summer than winter, with a marked effect in the smallest stream, where at one site the concentrations were >2000 most probable number (mpn) 100 mL in all summer samples. This variability of concentrations should be considered when interpreting the results from a one-off grab sample used to compare against water quality standards or for calibrating models.

Soil carbon sequestration potential of permanent pasture and continuous cropping soils in New Zealand.

Understanding soil organic carbon (SOC) sequestration is important to develop strategies to increase the SOC stock and, thereby, offset some of the increases in atmospheric carbon dioxide. Although the capacity of soils to store SOC in a stable form is commonly attributed to the fine (clay + fine silt) fraction, the properties of the fine fraction that determine the SOC stabilization capacity are poorly known. The aim of this study was to develop an improved model to estimate the SOC stabilization capacity of Allophanic (Andisols) and non-Allophanic topsoils (0-15 cm) and, as a case study, to apply the model to predict the sequestration potential of pastoral soils across New Zealand. A quantile (90th) regression model, based on the specific surface area and extractable aluminium (pyrophosphate) content of soils, provided the best prediction of the upper limit of fine fraction carbon (FFC) (i.e. the stabilization capacity), but with different coefficients for Allophanic and non-Allophanic soils. The carbon (C) saturation deficit was estimated as the difference between the stabilization capacity of individual soils and their current C concentration. For long-term pastures, the mean saturation deficit of Allophanic soils (20.3 mg C g-1 ) was greater than that of non-Allophanic soils (16.3 mg C g-1 ). The saturation deficit of cropped soils was 1.14-1.89 times that of pasture soils. The sequestration potential of pasture soils ranged from 10 t C ha-1 (Ultic soils) to 42 t C ha-1 (Melanic soils). Although meeting the estimated national soil C sequestration potential (124 Mt C) is unrealistic, improved management practices targeted to those soils with the greatest sequestration potential could contribute significantly to off-setting New Zealand's greenhouse gas emissions. As the first national-scale estimate of SOC sequestration potential that encompasses both Allophanic and non-Allophanic soils, this serves as an informative case study for the international community.