In a series of indoor and outdoor experiments with young sheep, feed supplements having different protein content were investigated. The supplements were chosen as those likely to elicit different Protein:Energy (P/E) ratios in the nutrients absorbed by the animal. The objective was to identify and characterize those that would support faster growth rate, bigger and leaner carcass production for the meat market, in different seasons in Southern Victoria, Australia (35-37° South, 141-143° East). Throughout, the GrazFeed model provided a reference system chosen for prediction of performance, with which the results of grazing experiments could be compete. / Supplementary feeding experiments were undertaken in the field (Experiments 1 and 4) in seasonal periods in which the pasture base found to poorly support high growth rates of weaned lambs. These experiments were supported by nutritional studies in pens (Experiments 2, 3 and 5) and supplement effects were evaluated in terms not only of liveweight but carcase and meat characteristics. Supplements used were evaluated and selected for use in further experiments on the basis that they would provide additional metabolisable energy but also would differ in the amount and nature of the crude protein they supplied and thus deliver different balances of absorbed nutrients, in particularly different P:E ratios. / Fish meal, with a high content of rumen undegradable protein of high biological value was used in each of these experiments to provide a test of the hypothesis that slow ruminal degradation and additional protein digested in the small intestine can influence animal response. In Experiment 1 and the related pen Experiment 2, comparing a lower to a higher P (CP%):E(MJ/kg) ratio feeds (barley, 12:13 P:E ratio) to (fishmeal / lucerne meal, 1/2 w/w, 35:10 P:E ratio), barley resulted in higher fat and lower protein amounts deposited as carcass components (P<0.01). The animals consuming extra protein were larger, leaner and became more uniform as a flock in terms of the range in LW and fat content at slaughter than those provided with supplements that are classed as energy feeds. / In Experiment 3 a range of alternative protein rich feeds and composite supplements was assembled that are cheaper and more readily available than fishmeal, with the idea that different patterns of ruminal degradation, intra-ruminal N availability and amounts of RUP could be created that would be beneficial in terms of the overall animal response. The paths of rumen protein degradability was determined with nylon bag techniques, and this was used to select feeds for investigation in a field and indoor experiments, Experiments 4 and 5. / In Experiment 4, grazing animals supplemented with lupines; (P:E 32:12), fishmeal / wheat bran 1/2 w/w (P:E 35:12) and formaldehyde treatment protected sunflower meal / wheat bran 1/2 w/w (P:E 24:11) responded poorly to the supplements where quality and quantity of pasture was such that unsupplemented growth rates were predicted to be poor by the decision support model, GrazFeed. In this and the supporting pen Experiment 5, the liveweight gain, final weight and dressing percentage of all supplemented lambs were significantly better than those of control (grazing only) animals (P<0.05). High and low commencing LW animals responded to protein supplements differently when these were fed at 1% BW with ad libitum medium quality roughage diet in indoor conditions. The heavier subgroup of fish meal / wheat bran (P:E 35:12) animals were significantly fatter than the heavy subgroup of wheat bran (P:E 17:10) animals (P<0.001). Lighter subgroup of animals were leaner and became more uniform (less variable) in weight and composition as a flock. Both the heavy and the light liveweight subgroups of fish meal grew faster but were fatter at slaughter than any other sub-groups. Lightest lambs fed bran grew from 26 to 36 kg in 10 weeks and had the most suitable carcase with the lowest priced supplement tested in the experiment. / Though protein supplementation had a positive effect on lamb performance; the advantage of high RUP was not consistent or always statistically significant. Compared to the alternative protein rich feeds, fish meal showed no cost effective advantage. The consequence of this current or possible future market conditions for feeding strategies for high quality lamb production are considered.
| Identifer | oai:union.ndltd.org:ADTP/269956 |
| Date | January 2000 |
| Creators | Polat, Esad S. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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