Ravelo A D, Vyas D, Ferraretto L F, Faciola A
Department of Animal Sciences, University of Florida, Gainesville, FL 32611, USA.
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
Transl Anim Sci. 2022 Apr 12;6(2):txac044. doi: 10.1093/tas/txac044. eCollection 2022 Apr.
Carbohydrates are one of the three macronutrients that provides energy in diets and are classified by their structures. Starch is a nonstructural carbohydrate and polysaccharide made of glucose monomers used for storage in plant cells. When starch makes up greater than 30% of the DM in diets there can be adverse effects on NDF digestibility due to decreases in ruminal pH. Sugars are water soluble carbohydrates that consist of monosaccharide and disaccharide units. Sugars ferment faster than starch because microorganisms in the rumen can ferment carbohydrates at different rates depending on their structure; however, this has not been shown to have negative effects on the ruminal pH. Sources of sugars such as molasses (sucrose) or whey (lactose) can be included in the diet as a partial replacement for starch in dairy cow diets. The purpose of replacing starch with sugars in a diet would be to add differing sources of carbohydrates in the diet to allow for continual fermentation of carbohydrates by the microorganisms in the rumen. It has been seen in studies and previous literature that the partial replacement of starch with sugars has the potential to maintain the ruminal environment and milk yield and composition in dairy cows without reducing NDF digestibility. The objective of this review is to evaluate the effects of partially replacing starch with sugars in dairy diets and its implication on ruminal fermentation, nutrient utilization, milk production, and feeding replacement strategy.
碳水化合物是饮食中提供能量的三种宏量营养素之一，并根据其结构进行分类。淀粉是一种非结构性碳水化合物和多糖，由葡萄糖单体组成，用于植物细胞中的储存。当淀粉在日粮干物质中所占比例超过30%时，由于瘤胃pH值下降，会对中性洗涤纤维的消化率产生不利影响。糖类是由单糖和二糖单元组成的水溶性碳水化合物。糖类比淀粉发酵得更快，因为瘤胃中的微生物可以根据碳水化合物的结构以不同的速率发酵碳水化合物；然而，这尚未显示对瘤胃pH值有负面影响。糖源如糖蜜（蔗糖）或乳清（乳糖）可作为奶牛日粮中淀粉的部分替代品纳入日粮。日粮中用糖类替代淀粉的目的是在日粮中添加不同的碳水化合物来源，以便瘤胃中的微生物持续发酵碳水化合物。在研究和以往文献中已经发现，用糖类部分替代淀粉有可能维持奶牛的瘤胃环境、产奶量和乳成分，而不降低中性洗涤纤维的消化率。本综述的目的是评估奶牛日粮中用糖类部分替代淀粉的效果及其对瘤胃发酵、养分利用、产奶性能和饲料替代策略的影响。
