School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 2 of 2
-
ItemMeasurement of body composition of lactating ewes using dual energy x-ray absorptiometry( 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.
-
ItemIntake and utilization of a barley supplement treated with virginiamycin by gestating and lactating ewes( 1991)A pen feeding study was conducted to evaluate the influence of virginiamycin (40 g virginiamycin/tonne barley ) on the production of pregnant and lactating ewes fed barley supplement. Twelve single and sixteen twin-bearing ewes were randomly allocated to one . of 3 groups to receive either lupins, barley or barley plus virginiamycin (BVM), fed for 3 weeks before and 3 weeks after lambing. During late pregnancy, feed intakes in ewes carrying twins were not altered by treatments. Mean liveweights at parturition of the barley-supplemented 'ewes. were below than those of the other groups (p=0.14). Feed conversion efficiency was significantly improved (p=0.05) in the lupin and BVM groups as compared to the barley supplemented ewes. The condition score of the ewes was not improved by supplementation and type of supplement had no effects on body condition score loss. Mean retention time of Cr-hay in the GI tract was increased (p<0.05) by supplementation with virginiamycin treated grain. However the dry matter digestibility on the BVM diet was not improved (p<0.05) as compared to the lupin supplemented ewes. The performance of ewes carrying singles was generally unaffected by treatment (p>0.1). The. exception occurred during lactation, where the barley-supplemented ewes lost more weight than the other groups (p<0.05). Differences in the mean birth weight of twin lambs were significant (p=0.05) while those of lambs born as singles was not significant. Twin lambs from ewes fed barley showed significantly higher mortality (p<0.01) than lambs born to ewes in lupin and BVM groups. However , no single born lambs in any group died from birth to 42 days of age. No significant differences were found between total milk yields of ewes nursing either twin or single lambs. The yield of milk fat from ewes nursing twins in lupin group was significantly higher (p<0.05) at day 20 of lactation than the other groups. The results suggest that lupin grain was not superior to barley grain plus virginiamycin as a supplement for gestating and lactating ewes carrying twin lambs fed hay as a basal diet. However, on the basis of cost, barley plus virginiamycin would generally be prefered.