School of Agriculture, Food and Ecosystem Sciences - Theses

Permanent URI for this collection

http://hdl.handle.net/11343/427

Filters

1993 - 2000 3
Reset filters

Settings
Statistics
Citations
Subject: Measurement ×

Search Results

Now showing 1 - 3 of 3
  • Item
    Thumbnail Image
    Measurement of body composition of lactating ewes using dual energy x-ray absorptiometry
    Hunter, Trepheena Emily ( 2000)
    The measurement of body composition in live animals has previously been limited to subjective methods such as condition scoring and ultrasound. There are now many direct techniques available to estimate body composition. Dual-energy x-ray absorptiometry (DXA) is a technique that offers a rapid and non-invasive analysis of body composition. It should therefore be possible to use DXA technology to measure changes in body composition in ewes throughout lactation. However DXA has not previously been used for measuring body composition in live sheep. Experimental work was undertaken to determine the correlation between body composition given by DXA and chemical body composition. Correlations between DXA and chemical composition were excellent (R2>0.96 for live animal and R2>0.91 for carcass composition). Regression equations for body composition from DXA and chemical analysis were developed: the equations for analysis in position 1 (entire scan placed in the Right Arm region for analysis) were: fat tissue mass by chemical analysis (FTM) = (1.20 x DXA FTM) - 0.067 (R2=97.8) chemical inorganic matter = (1.08 x DXA bone mineral content) + 0.294 (R2 = 97.2) chemical lean tissue mass (LTM) = (0.933 x DXA LTM) + 1.25 (R2 = 98.9) This study concluded that DXA has great potential for use in live sheep and carcass research. The East Friesian is a relatively new breed in Australia and little is known about its productive capacity under Australian conditions. It is thought, on the basis of work undertaken in New Zealand, that the breed will provide excellent prime lamb mothers that produce large quantities of milk over long periods and are highly fecund. Lamb carcass quality is also claimed by breeders to be excellent. East Friesians were first introduced to Australia in 1996 and most ewes are half-cross, commonly East Friesian x Romney. While the East Friesian is reputedly one of the most productive dairy breeds, the lactational performance of East Friesian cross ewes in Australia is unknown. A study was therefore undertaken to compare the performance of single-bearing East Friesian x Romney ewes and the common Australian prime lamb dam, the Border Leicester x Merino. The results of this study showed that East Friesian x Romney ewes have the potential to produce significantly more milk over the first nine weeks of lactation (mean milk yield: 2.6 ± 0.1 vs 1.9 ± 0.2 kg/day for East Friesian x Romney and Border Leicester x Merino, respectively). The feed intake and changes in liveweight of the two breeds were not significantly different. Mean feed intake over the nine week experimental period was 3.39 ± 0.20 and 3.10 ± 0.16 kg/day for the EFR and BLM ewes, respectively. Mean liveweight was 76.6 ± 4.0 and 77.4 ± 3.2 kg for the EFR and BLM ewes, respectively. The question arising from this initial study was: can East Friesian x Romney ewes produce more milk by using the available feed more efficiently or by mobilising body reserves? This has significant nutritional implications, both at a research and field level. Having determined correlation equations for use of DXA on live sheep, a study of the changes in body composition (fat, lean and bone mineral) during lactation was undertaken to examine the differences between East Friesian x Romney and Border Leicester x Merino ewes. Differences were observed which indicated some differences in body composition between the EFR and BLM ewes: the EFR ewes had a significantly lower percentage of fat tissue mass and higher percentage of lean tissue mass. Some technical issues were defined and further investigation into DXA including the effect of wool cover and gastrointestinal water contents is required. However the present results indicate that DXA provides a sound basis for examining body composition in live sheep.
  • Item
    Thumbnail Image
    Logging residue assessment
    O'Hehir, James Francis ( 1993)
    A total logging residue assessment system is proposed specifically for application in the Pinus radiata D.Don. (radiata pine) plantations in South Australia and Western Victoria. The choice of line intersect sampling using pseudo-circular sample lines, believed not to have been tried before, ensures a robust sampling technique able to overcome any bias that exists in the alignment of residue following harvesting. An analysis is presented defining the bias and precision obtained from a variety of geometric sample line arrangements and sampling intensities. A cost effective residue sampling system of known efficiency can be implemented as an integral component in an overall yield regulation and control system.
  • Item