Lee Jung Wook, Kim In Ho, Woyengo Tofuko Awori
Department of Animal Science, South Dakota State University, Brookings, SD 57007, USA.
Department of Animal Resource and Science, Dankook University, Cheonan-si, Chungnam 31116, Korea.
Animals (Basel). 2020 Dec 9;10(12):2337. doi: 10.3390/ani10122337.
Canola co-products are widely included in swine diets as sources of proteins. However, inclusion of canola co-products in diets for pigs is limited by toxicity of glucosinolate degradation products. Aliphatic and aromatic glucosinolates are two major classes of glucosinolates. Glucosinolate degradation products derived from aliphatic glucosinolates (progoitrin) include crambene, epithionitriles, and goitrin, whereas indole-3-acetonitrile, thiocyanate, and indole-3-carbinol are the major aromatic glucosinolates (glucobrassicin)-derived degradation products. At acidic pH (<5.7), progoitrin is degraded by myrosinases to crambene and epithionitriles in the presence of iron, regardless of the presence of epithiospecifier protein (ESP), whereas progoitrin is degraded by myrosinases to goitrin in the absence of ESP, regardless of the presence of iron at neutral pH (6.5). Indole-3-acetonitrile is the major degradation product derived from glucobrassicin in the absence of ESP, regardless of the presence of iron at acidic pH (<4.0), whereas thiocyanate and indole-3-carbinol are the major glucobrassicin-derived degradation products in the absence of ESP, regardless of the presence of iron at neutral pH (7.0). In conclusion, the composition of glucosinolate degradation products is affected by parent glucosinolate composition and hindgut pH. Thus, toxicity of canola co-product-derived glucosinolates can be potentially alleviated by modifying the hindgut pH of pigs.
油菜籽副产品作为蛋白质来源被广泛应用于猪的日粮中。然而，油菜籽副产品在猪日粮中的添加量受到硫代葡萄糖苷降解产物毒性的限制。脂肪族硫代葡萄糖苷和芳香族硫代葡萄糖苷是硫代葡萄糖苷的两大主要类别。脂肪族硫代葡萄糖苷（前致甲状腺肿素）衍生的硫代葡萄糖苷降解产物包括克拉烯、环硫腈和致甲状腺肿素，而吲哚-3-乙腈、硫氰酸盐和吲哚-3-甲醇是主要的芳香族硫代葡萄糖苷（葡萄糖芸苔素）衍生的降解产物。在酸性pH（<5.7）条件下，无论是否存在硫代葡萄糖苷特异性蛋白（ESP），前致甲状腺肿素在铁存在的情况下都会被硫代葡萄糖苷酶降解为克拉烯和环硫腈；而在中性pH（6.5）条件下，无论是否存在铁，在前致甲状腺肿素缺乏ESP的情况下，都会被硫代葡萄糖苷酶降解为致甲状腺肿素。在酸性pH（<4.0）条件下，无论是否存在铁，在缺乏ESP的情况下，吲哚-3-乙腈是葡萄糖芸苔素衍生的主要降解产物；而在中性pH（7.0）条件下，无论是否存在铁，在缺乏ESP的情况下，硫氰酸盐和吲哚-3-甲醇是葡萄糖芸苔素衍生的主要降解产物。总之，硫代葡萄糖苷降解产物的组成受母体硫代葡萄糖苷组成和后肠pH的影响。因此，通过调节猪的后肠pH，有可能减轻油菜籽副产品衍生硫代葡萄糖苷的毒性。
