Seck M, Linton J A Voelker, Allen M S, Castagnino D S, Chouinard P Y, Girard C L
Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre, 2000 College, Sherbrooke, Québec, Canada, J1M 0C8; Département des Sciences Animales, Université Laval, 2425 rue de l'Agriculture, Québec, Québec, Canada, G1V 0A6.
Department of Animal Science, Michigan State University, East Lansing 48824-1225.
J Dairy Sci. 2017 Mar;100(3):1914-1922. doi: 10.3168/jds.2016-12111. Epub 2017 Jan 18.
Effects of the forage-to-concentrate ratio on apparent ruminal synthesis of thiamine, riboflavin, niacin, vitamin B, folates, and vitamin B were evaluated in an experiment using 14 ruminally and duodenally cannulated Holstein cows. The experiment was a crossover design with two 15-d treatment periods and a 14-d preliminary period in which cows were fed a diet intermediate in composition between the treatment diets. Treatments were diets containing low-forage (44.8% forage, 32.8% starch, 24.4% neutral detergent fiber) or high-forage (61.4% forage, 22.5% starch, 30.7% neutral detergent fiber) concentrations. Both diets were formulated with different proportions of the same ingredients. Concentrations of B vitamins were analyzed in feed and duodenal digesta. Apparent ruminal synthesis of each B vitamin was calculated as the duodenal flow minus the intake. The high-forage diet had the highest concentrations of riboflavin, niacin, vitamin B, and folates, whereas the low-forage diet had the highest thiamine concentration. Vitamin B in the diets was under the level of detection. Consequently, despite a reduction in dry matter intake when the cows were fed the high-forage diet, increasing dietary forage concentration increased or tended to increase intakes of riboflavin, niacin, and vitamin B but reduced thiamine and folate intakes. Increasing dietary forage concentration reduced apparent ruminal degradation of thiamine and apparent ruminal synthesis of riboflavin, niacin, and folates and increased ruminal degradation of vitamin B, but had no effect on ruminal synthesis of vitamin B. As a consequence, increasing the forage-to-concentrate ratio had no effect on the amounts of thiamine, riboflavin, and vitamin B reaching the small intestine but decreased the amounts of niacin, vitamin B, and folates available for absorption. Apparent ruminal syntheses of riboflavin, niacin, folates, and vitamin B were correlated positively with the amount of starch digested in the rumen and duodenal flow of microbial N, whereas these correlations were negative for thiamine. Apparent ruminal syntheses of thiamine and vitamin B were negatively correlated with their respective intakes, whereas folate intake was positively correlated with its synthesis in the rumen.
在一项使用14头装有瘤胃和十二指肠瘘管的荷斯坦奶牛的实验中，评估了饲粮精粗比对硫胺素、核黄素、烟酸、维生素B₆、叶酸和维生素B₁₂瘤胃表观合成的影响。该实验采用交叉设计，有两个15天的处理期和一个14天的预试期，在此期间给奶牛饲喂一种组成介于处理饲粮之间的中间饲粮。处理为低粗饲料（44.8%粗饲料、32.8%淀粉、24.4%中性洗涤纤维）或高粗饲料（61.4%粗饲料、22.5%淀粉、30.7%中性洗涤纤维）浓度的饲粮。两种饲粮均由相同成分按不同比例配制而成。分析了饲料和十二指肠食糜中B族维生素的浓度。每种B族维生素的瘤胃表观合成量计算为十二指肠流量减去摄入量。高粗饲料饲粮的核黄素、烟酸、维生素B₆和叶酸浓度最高，而低粗饲料饲粮的硫胺素浓度最高。饲粮中的维生素B₁₂低于检测水平。因此，尽管给奶牛饲喂高粗饲料饲粮时干物质摄入量减少，但提高饲粮粗饲料浓度会增加或趋于增加核黄素、烟酸和维生素B₆的摄入量，但会降低硫胺素和叶酸的摄入量。提高饲粮粗饲料浓度会降低硫胺素的瘤胃表观降解率以及核黄素、烟酸和叶酸的瘤胃表观合成率，并增加维生素B₁₂的瘤胃降解率，但对维生素B₆的瘤胃合成没有影响。因此，提高精粗比不会影响到达小肠的硫胺素、核黄素和维生素B₆的量，但会减少可吸收的烟酸、维生素B₁₂和叶酸的量。核黄素、烟酸、叶酸和维生素B₆的瘤胃表观合成与瘤胃中消化的淀粉量和微生物氮的十二指肠流量呈正相关，而硫胺素的这些相关性为负。硫胺素和维生素B₆的瘤胃表观合成与其各自的摄入量呈负相关，而叶酸摄入量与其在瘤胃中的合成呈正相关。
