Abstract
BackgroundGrain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility (AID) of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination.MethodsThree experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans (Vicia faba L.) and peas (Pisum sativum L.), five different cultivars of lupins (Lupinus luteus L., Lupinus angustifolius L.), and one diet with a soybean meal (SBM) were fed.ResultsThe starch content of faba beans and peas was greater (P < 0.05) when determined polarimetrically than enzymatically (438 vs. 345 g/kg dry matter (DM) in faba beans and 509 vs. 390 g/kg DM in peas, respectively). Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM (analyzed polarimetrically) and <1.1 and 3 g/kg DM (analyzed enzymatically), respectively. Mean values for contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF) in grain legumes ranged from 111 and 79 g/kg DM in peas to 248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater (P < 0.05) in pea than in faba bean cultivars, and using the polarimetric starch determination method resulted in greater (P < 0.05) digestibility values than using enzymatic starch analysis (84 vs. 80% in faba beans and 86 vs. 83% in peas). Moreover, AID of starch differed (P < 0.05) within pea cultivars and starch digestibility in faba beans decreased linearly (P < 0.05) as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars.ConclusionBoth contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.
Highlights
Grain legumes represent a valuable energy source in pig diets due to their high starch content
Starch content for all lupin cultivars was below the detection limit of 1.1 g/kg dry matter (DM) when analyzed enzymatically
According to results of in vitro digestion of starch in red kidney beans (Phaseolus vulgaris), amylolysis was enhanced by wet homogenization and pepsin pretreatment [52]. These findings suggest that disruption of cell walls is important for efficient starch digestion, no relationship between apparent ileal digestibility (AID) of starch and neutral detergent fiber (NDF) or acid detergent fiber (ADF) contents in the diets could be established, likely due to low variation among cultivars
Summary
Grain legumes represent a valuable energy source in pig diets due to their high starch content. Grain legumes have proven to be a valuable energy source in animal nutrition due to their high content of starch in faba beans and peas and lipids in lupins [1]. The use of grain legumes in livestock nutrition, is often limited due to the presence of secondary plant metabolites (tannins, protease inhibitors, alkaloids, lectins, pyrimidine glycosides, saponins), referred to as anti-nutritional factors (ANF). These metabolites can induce feed refusals (tannins, alkaloids), reduced nutrient digestibility (tannins, protease inhibitors, lectins), or even toxic effects (alkaloids) [3]. Hydrolysis of starch by pancreatic α-amylase has been reported to be inversely related to the amylose content, with high amylose starches being resistant [5]
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