Shearing during pregnancy — review of a policy to increase birthweight and survival of lambs in New Zealand pastoral farming systems

Over the past decade, lambing percentages have risen in conjunction with a rise in the percentage of multiple lambs born. Multiple-born lambs are smaller than their singleton counterparts and are particularly susceptible to starvation-exposure. Any technique that can increase the birthweight or thermoregulatory capability, or both, of otherwise lightweight lambs has the potential to substantially increase survival of multiple-born lambs.

In the United Kingdom under housed conditions, shearing during pregnancy has been shown to increase both the birthweight and thermoregulatory capability of newborn lambs. However, shearing during pregnancy under pastoral conditions has failed to consistently affect the newborn lamb’s thermoregulatory capability. In contrast, under New Zealand’s pastoral conditions shearing during pregnancy has been found to increase birthweight, but results have been inconsistent in both magnitude and birth-rank specificity. Increase in feed intake by the dam, types of shearing comb used and changes in gestation length do not explain the variation observed. When studies involving shearing during pregnancy are collated it becomes apparent that there are two criteria that must be met to achieve a birthweight response. Firstly, the dam must have the potential to respond and secondly, the dam must have the means to respond.

Any increase in lamb survival through shearing during pregnancy would be predominantly through an increase in birthweight of otherwise lightweight lambs. However, in the few studies conducted to date, an increase in birthweight has not resulted in a statistically significant increase in survival. For an increase in birthweight to have a positive effect on lamb survival, lambs must be otherwise destined to be born within a birthweight range in which survival rate is below optimum (<4.0 kg), and the increase in birthweight observed must move a significant proportion of otherwise lightweight lambs into a higher range of survival rate.     

Effects of Time of Application of Inorganic Nitrogen Fertilizers on Apple Trees in a Grassed Orchard

Sulphate of ammonia, calcium nitrate or Nitrochalk was applied as a single annual dressing in October, December, February, April, June or August to Cox’s Orange Pippin apple trees on M.2 rootstock over a 14-year period, whilst control trees received no supplementary nitrogen.

The treatments affected the soil physical and chemical conditions, sward composition, and leaf and fruit mineral composition but, despite these effects, there were no long-term differences in tree growth or cropping between the kinds of fertilizer used or their times of application.

Nitrogen effects were progressive ; in the first four years there was a time X kind interaction on cropping; in the next five years only the time of application affected cropping and in the final five years neither time nor kind had differential effects on cropping, although N increased yield compared with the control. Growth was also increased by the N treatments but, again, only in the latter years of the experiment.

Leaf N was highly correlated with rainfall during March to August. In all but the first two and the last of the 14 years, rainfall was above the long-term average for the site.

February appeared to be the best month in which to apply sulphate of ammonia and calcium nitrate, and December for Nitrochalk application.     

Water,Osmotic and Pressure Potential Relationships in Apple Leaves

Water (ψ_w) and osmotic (ψ_s) potentials were measured in leaves of irrigated and unirrigated Cox’s Orange Pippin apple trees on MM. 104 rootstock during the summer seasons of 1969 and 1970. Turgor pressure potential (ψ_ρ) was assessed from the difference between and ψ_s.

Intercept values for ψ_s derived from regressions of ψ_s on ψ_w reflected an increasing intracellular osmotic concentration throughout the season and an increasing ability of the trees to withstand environmental stress in respect to turgor. In 1970 ψ_s decreased about 5 bars from July to September.

The slope relating ψ_s and ψ_w remained nearly constant after June and reflected the property of the leaf cells to expand or contract with increasing or decreasing ψ_w. Since the slope was similar throughout both seasons, a general relationship between ψ_w, ψ_s and ψ_p was evaluated, from which it was deduced that a diurnal decrease in ψ_w resulted from the sum of the depressions in ψ₃ and ψ_ρ in the ratio of 3 : 4.

The rate at which ψ_w decreased with increasing evaporation demand appeared to be under stomatal control; the latter was maximal when ψ_ν equalled the value of ψ_s at full turgor. The value of ψ_p at this point was about 8 bars. Further depression of ψ_w led to yellowing and dropping of the basal leaves of shoots and spurs—an effect only present in the unirrigated trees.

Under moderate conditions of evaporation demand the effect of irrigation on ψ_w appeared to be negligible while the soil moisture tension within any part of the root zone remained within the tensiometer measurement range. When soil moisture stress became greater than this, irrigation maintained ψ_w at between 5.3 and 6.3 bars higher than it was in the leaves of the unirrigated trees. Subsequently, the unirrigated trees defoliated completely several weeks earlier than the irrigated trees.     

Changes in Earth's reflectance over the past two decades

We correlate an overlapping period of earthshine measurements of Earth's reflectance (from 1999 through mid-2001) with satellite observations of global cloud properties to construct from the latter a proxy measure of Earth's global shortwave reflectance. This proxy shows a steady decrease in Earth's reflectance from 1984 to 2000, with a strong climatologically significant drop after 1995. From 2001 to 2003, only earthshine data are available, and they indicate a complete reversal of the decline. Understanding how the causes of these decadal changes are apportioned between natural variability, direct forcing, and feedbacks is fundamental to confidently assessing and predicting climate change.