Lees G L
Research Station, Agriculture Canada, Saskatoon, Saskatchewan.
Basic Life Sci. 1992;59:915-34. doi: 10.1007/978-1-4615-3476-1_55.
For the past 20 years, the focus in our laboratory has been on finding the causes of ruminant pasture bloat and eventually breeding a bloat-safe alfalfa (Medicago sativa L.); i.e., with bloat potential reduced to the economic threshold. In the mid-seventies, the mechanisms of bloat were explored and found to be more physical than chemical. Characteristic of all bloating legumes after ingestion was a very rapid initial rate of ingestion by rumen microbes. Through the study of bloating and non-bloating legumes, factors were elucidated in the plant that would slow this process. One of these factors was the presence of condensed tannins in the herbage. Some of the non-bloating legumes contained these secondary metabolites, but no condensed tannins were found in any of the bloating legumes. Therefore, species containing an appreciable amount of condensed tannins in their leaves and stems are considered to be non-bloating. Conventional breeding methods have not been successful in producing an alfalfa with condensed tannins in its herbage. New approaches using tissue culture techniques are being attempted, but genetic engineering has the greatest potential for success.
在过去20年里，我们实验室的重点一直是找出反刍动物牧场臌胀的原因，并最终培育出一种对臌胀安全的苜蓿（紫花苜蓿）；也就是说，将臌胀可能性降低到经济阈值。在70年代中期，对臌胀机制进行了探索，发现其更多是物理性而非化学性的。所有引起臌胀的豆科植物在被摄入后，瘤胃微生物的初始摄入速率都非常快。通过对引起臌胀和不引起臌胀的豆科植物的研究，阐明了植物中会减缓这一过程的因素。其中一个因素是牧草中存在缩合单宁。一些不引起臌胀的豆科植物含有这些次生代谢产物，但在任何引起臌胀的豆科植物中都未发现缩合单宁。因此，在其叶片和茎中含有相当数量缩合单宁的物种被认为是不引起臌胀的。传统育种方法未能成功培育出牧草中含有缩合单宁的苜蓿。正在尝试使用组织培养技术的新方法，但基因工程取得成功的潜力最大。
