Longstaff M, McNab J M
AFRC Institute for Grassland and Animal Production, Poultry Department, Roslin, Midlothian.
Br J Nutr. 1991 Mar;65(2):199-216. doi: 10.1079/bjn19910081.
The effects of polysaccharides and tannins present in the hulls of field beans (Vicia faba L.) on the digestion of amino acids, starch and lipid were studied in poultry. A control diet without hulls and the same diet substituted with 400 g hulls/kg diet from three different varieties of beans were fed to 3-week-old chicks for 4 d. Digestibility coefficients for amino acids, starch and lipid were calculated from measurements made of these nutrients in the diets and the freeze-dried excreta with the aid of titanium dioxide as a marker. Activities of trypsin (EC 3.4.21.4), alpha-amylase (EC 3.2.1.1), and lipase (EC 3.1.1.3) in digesta removed from the upper jejunum, sucrase (EC 3.2.1.48) in the gut mucosa from the upper jejunum, and alpha-amylase and lipase in the pancreas were measured. The hulls were analysed for their polysaccharide and tannin contents. Results showed that the hulls were mostly carbohydrate in composition, with cellulose the predominant polysaccharide. Tannins present in the hulls of two coloured-flowering varieties (Brunette and Minica) were of the condensed type. The diet with tannin-free hulls (white-flowering variety Medes) lowered slightly the digestion of amino acids, starch and lipid compared with the control diet. This effect was believed to be due to inhibition of digestive enzymes, possibly through their adsorption onto the hulls. Diets with tannin-rich hulls (varieties Brunette and Minica) caused a large reduction in the digestion of amino acids, starch and lipid compared with the control diet mainly due to inactivation of digestive enzymes by the formation of tannin-enzyme complexes in the digestive tract. Enzyme activities could be partially restored by the addition of polyvinylpyrrolidone to the digesta. Tannins inactivated trypsin the most, alpha-amylase to a lesser extent and lipase the least and as a consequence lowered the digestion of amino acids the most, starch to a lesser extent and lipid the least. Tannins did not induce an increased pancreatic production of digestive enzymes, nor did they affect activity of jejunum mucosal sucrase. Condensed tannins from Brunette and Minica hulls were partially extractable in methanol alone, but required acidic methanol for fuller extraction. The vanillin:anthocyanidin ratio suggested that tannins were polymerized to the same degree in the Brunette and Minica varieties, both in the methanol and acidic methanol extracts. Hulls from the variety Minica contained a greater amount of methanol-extractable tannins, the quantity of remaining tannins that required acidic methanol for extraction being the same for both varieties.
研究了蚕豆（野豌豆）豆皮中的多糖和单宁对家禽氨基酸、淀粉和脂质消化的影响。将不含豆皮的对照日粮以及用三种不同品种的蚕豆以400 g豆皮/kg日粮替代的相同日粮喂给3周龄雏鸡，持续4天。借助二氧化钛作为标记物，根据日粮和冻干排泄物中这些营养素的测量值计算氨基酸、淀粉和脂质的消化系数。测定了从空肠上段取出的食糜中胰蛋白酶（EC 3.4.21.4）、α-淀粉酶（EC 3.2.1.1）和脂肪酶（EC 3.1.1.3）的活性，空肠上段肠黏膜中蔗糖酶（EC 3.2.1.48）的活性，以及胰腺中α-淀粉酶和脂肪酶的活性。分析了豆皮中的多糖和单宁含量。结果表明，豆皮的成分主要是碳水化合物，纤维素是主要的多糖。两个有色花品种（Brunette和Minica）豆皮中的单宁为缩合型。与对照日粮相比，不含单宁的豆皮（白花品种Medes）日粮使氨基酸、淀粉和脂质的消化率略有降低。据信这种影响是由于消化酶受到抑制，可能是通过它们吸附在豆皮上。与对照日粮相比，富含单宁的豆皮（Brunette和Minica品种）日粮导致氨基酸、淀粉和脂质的消化率大幅降低，主要是因为消化道中形成单宁-酶复合物使消化酶失活。通过向食糜中添加聚乙烯吡咯烷酮，酶活性可部分恢复。单宁对胰蛋白酶的失活作用最大，对α-淀粉酶的失活作用较小，对脂肪酶的失活作用最小，因此对氨基酸消化率的降低最大，对淀粉消化率的降低较小，对脂质消化率的降低最小。单宁不会诱导胰腺消化酶分泌增加，也不会影响空肠黏膜蔗糖酶的活性。Brunette和Minica豆皮中的缩合单宁仅用甲醇即可部分提取，但需要酸性甲醇才能更充分地提取。香草醛：花青素的比例表明，Brunette和Minica品种中的单宁在甲醇和酸性甲醇提取物中的聚合程度相同。Minica品种的豆皮中含有更多可被甲醇提取的单宁，两个品种中需要酸性甲醇提取的剩余单宁量相同。
