Remy Dehaan

Ewe and lamb contact at lambing is influenced by both shelter type and birth number.

A significant number of lambs born each year in Australia die within 72 h of birth. Periods of high wind, combined with rain and low temperatures can lead to marked increases in the mortality level. Under these climatic conditions mortality levels may be reduced with the provision of shelter. This study used contact loggers to compare interactions between ewes with twin lambs across two shelter types (Hessian and shrubs), while also comparing ewes with single and twin lambs in a single shelter type (Hessian). The contact loggers record the time of the initial contact (within approximately 4 to 5 m) between collared animals and the duration of each contact. Contact levels between ewes immediately after lambing were only 10% of the initial levels (1 h/day). For single-born lambs, lambs averaged 11 h contact per day with their mother, while for twinborn lambs, each lamb averaged 9.25 h/day with its mother and 14.7 h/day with its sibling. The level of contact between ewes and each of their offspring in the Hessian was 24% lower (P < 0.05) for ewes with twin lambs than with singles. For ewes with twin lambs the level of contact was 17% lower (P < 0.05) in the Hessian shelter compared with shrub shelter. We conclude that shelter type and birth number can affect the level of contact between ewes and their offspring.

Shelter type and birth number influence the birth and death sites of lambs and ewe movement around lambing time

A significant number of lambs born each yr in Australia die within 72 h of birth. Periods of high wind, combined with rain and low temperatures, can lead to marked increases in the level of mortality. Under these weather conditions mortality levels may be reduced with the provision of shelter, provided it is utilized by lambs. This study used GPS collars to determine the use of shelter by ewes and lambs, to compare the movement of ewes with twin lambs across 2 types of shelter (hedgerows and shrubs), while also comparing ewes with single and twin lambs in a single shelter type (hedgerows). Additionally, the birth sites of 364 lambs and death sites of 252 lambs were recorded across the 3 shelter type and litter size combinations (Twins in shrubs, Twins in hedgerows, Singles in hedgerows) plus an unsheltered group (Singles in unsheltered). A higher (P < 0.001) than randomly expected percentage of ewes lambed in the areas closest to both shelter types; in the shrub shelter 42% of ewes lambed within 2.5 m of shrub rows compared to an expected 11% based on the proportion of the paddock this area constituted. Despite the higher than expected percentage of ewes lambing close to the shelter rows, ewes in both twin lamb shelter types avoided the areas close to the shelter before and after lambing (Hedgerows-2.5 m; Shrubs- 6.25 m) and single bearing ewes showed no preference for or against these areas. With a high proportion of twin bearing ewes lambing close to the shelter, a design that reduces the potential for ewe and offspring separation while providing good shelter will offer the greatest potential reduction in newborn twin lamb mortality arising from exposure.

Using Field-Derived Hyperspectral Reflectance Measurement to Identify the Essential Wavelengths for Predicting Nitrogen Uptake of Rice at Panicle Initiation:

Rice growers are reluctant to physically sample their crops, with many relying on visual estimates of crop nitrogen status to determine mid-season nitrogen topdressing requirements. There is increased interest in using remote sensing to determine how accurately mid-season rice crop nitrogen status (nitrogen concentration and content in shoots) can be predicted. Field-derived hyperspectral reflectance measurements were collected over three seasons to evaluate the optimal wavelengths for the prediction of in-crop nitrogen at panicle initiation. Rice plots were planted and differing nitrogen rates applied to establish a range of crop nitrogen uptake levels at the panicle initiation stage of crop development. Hyperspectral canopy reflectance (350–2500 nm) data were collected from each plot at the panicle initiation growth stage and plant samples were collected at each scanning location. Calibration models were developed for plant nitrogen concentration, dry matter and nitrogen uptake using partial least squares regression and the influential wavelengths used in the nitrogen uptake prediction model identified. When the nitrogen uptake model, which included samples collected in three crop seasons, was used to predict nitrogen uptake in an independent set of samples, r2 was 0.84 and the root-mean-square error of prediction (RMSEP) was 16.5 kg N ha−1. The important wavelengths utilised for predicting nitrogen uptake were determined from the regression coefficients and a new calibration created by multiple linear regression (MLR) using only four wavelengths (738 nm, 1362 nm, 1835 nm and 1859 nm). The MLR calibration using the four wavelengths had a prediction accuracy of r2 = 0.82 and RMSEP = 18.4 kg N ha−1, which shows potential for commercial applications. These findings will encourage the development of a remote sensing method for predicting nitrogen uptake for rice crops using the identified wavelengths in an inexpensive multiband instrument.