科研之友
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摘要
The scientific literature contains divergent views about the effects of nutrition on cashmere. The consequences of ignoring nutrition will be an increase in the number of goats suffering lower production, increased welfare risks and premature mortality. This review evaluated published reports to identify current knowledge and best practice in regard to the design and management of cashmere nutrition experiments. The ability of experiments to distinguish between treatments was evaluated based on their statistical evidence. Many experiments had serious deficiencies in their design, conduct and reporting. Six of 16 papers did not provide statistical information that would enable a reader to verify differences between treatments. For most experiments to detect nutrition affects at P < 0.05, they required a difference between treatments of 0.2-0.8 mu m in cashmere mean fibre diameter and 15-42 g in clean cashmere production. Government Research Institutes research was characterised by more experienced authors conducting longer (P < 0.05) and larger (P < 0.05) experiments than those conducted by Universities. Much of the "debate" regarding the affects of nutrition on cashmere production arises from the misinterpretation of both experiments that did not detect statistically significant effects and of experiments that did detect statistically significant effects. Based on a comparison between experiments reporting responses to nutrition with those reporting no response, 13 design and management features were identified that are related to the ability of experiments to detect significant treatment affects. Methods Must be adopted to reduce the variance in cashmere production within treatments. by using sufficient animals per treatment, and having replication to provide sufficient degrees of freedom to reduce error terms in analysis. The power of experimental designs should be evaluated before experiments commence. Cashmere production records from a previous full production year could be used as co-variants during statistical analyses but this requires that potential experimental goats are managed in one flock, without variations resulting from different grazing, reproduction or other management for a year prior to an experiment. It is preferable to use more productive and older goats, and goats that are used to handling, and to the conditions and feed to be used. Allocation of animals to treatments must take into account live weight. Nutrition treatments need to be sufficiently different to produce different growth curves. An appropriate control is needed such as live weight maintenance. Evidence of both nutrition intake and growth curves must be published with cashmere production data so the claims made can be verified by the actual responses. As cashmere production is an order of magnitude less than fibre production of Merino sheep or Angora goats and is more difficult to measure, the requirements for measurement, sampling and testing cashmere fleeces are summarised. The use of mid side cashmere patches to determine cashmere growth and quality is seriously biased and must be avoided, preferably by shearing goats prior to and at the end of experiments. In order to obtain higher fleece growth responses and improve the ability of experiments to detect treatment effects it is preferable to start cashmere growth experiments by midsummer and conduct experiments for at least 4 months. These requirements make it difficult for many university students to plan, undertake and complete long-term cashmere nutrition experiments without considerale management support. It is not possible for experiments to disprove the Null hypothesis regarding the effects of nutrition on cashmere production as they can only report a failure to detect treatment effects. Researchers and journals need to be more rigorous in providing statistical information including: degrees of freedom for error terms, treatment variances, standard error of differences or similar to enable readers to compare treatment effects. Publications that do not provide sufficient statistical information should be disregarded from future discussions. Claims that an experiment shows no responses to nutrition should be subject to rigorous examination using the issues identified in this review.
- 出版日期2009-4
