Animal Nutrition and Feed Evaluation

Agriculture

Animal Nutrition and Feed Evaluation

Qualitative, scientific-based evaluations of animal feed and the resultant nutrition of the animal are crucial for maintaining optimal animal health and responding to problems that develop as a result of diet. In the case of ruminants, this can be particularly important as their unique digestive system can complicate providing optimal nutrition from traditional feed sources and techniques. A balanced nutrient approach to ruminant diet must take into account not only the feed that is being given to the animal, but also, crucially, the way in which the animal's digestive system will process that feed and provide (or not) nutrition to the animal. Creating this type of qualitative knowledge about the digestive system and nutrition needs of rumens with regard to different feeds "developed most rapidly when isotope dilution techniques became easy to apply, facilitated by improved instrumentation and mathematical approaches" (1). From this information, researchers have recognized some of the fundamental problems with traditional feed evaluation and feeding standards in practice as they applied to digestion, metabolism, and growth -- especially when ruminants were fed low-quality forage.

Therefore, it is crucial that we question traditional feed evaluation and standards for ruminants, as research has demonstrated them to be not effective in producing optimal nutrition for the animals. Until the late 1980s, it was taken for granted that feed standards for ruminants be based on the metabolizable energy contained within the feed, on the unproven assumption that the ruminant's stomach would be able to process this caloric and nutritive content on a simple 1:1 basis (2). In practice, though, research has demonstrated that this assumption is dubious at best. The assumptions made by earlier researchers on the subject generally do not apply in real-world situations, especially when ruminants are fed lower-quality feeds, as they are in much of the world. The limitations inherent in the lower-quality forage most ruminants subsist on place severe limits on production including a "low protein supply from the microbial ecosystem and a virtual absence of dietary bypass protein" (2). In other words, low-quality feed based on past assumptions has created a feeding situation in which the nutrition needs of the animals are not being met.

In order to combat this deficiency, new trends in research have been developed to increase ruminant productivity and health through a balanced nutrient approach. In fact, research into ruminant feeds and nutrition has been proceeding along these lines, with definite gains being made into deepening our understanding of how nutrients are absorbed from the ruminant digestive tract from various feeds, especially common, low-quality feeds. In particular, researchers must pay attention to microbial growth efficiencies in the rumen and the ratio of amino acids to nutrient energy. When these twin understandings are applied to "diets based on relatively poor quality roughage, surprisingly high levels of production can be achieved" (4). In essence, a deeper knowledge of how nutrients are processed in the rumen from different feeds will allow us to better improve animal nutrition through feeds and enhance animal health and productivity.