In vitro prediction of standardised ileal crude protein and amino acid digestibilities in grain legumes for growing pigs

Abstract

The study was conducted to validate in vitro prediction of standardised ileal digestibilities (SID) of crude protein (CP) and amino acids (AA) in grain legumes for growing pigs using six different cultivars of faba beans (Vicia faba), six different cultivars of field peas (Pisum sativum), and five different cultivars of lupins (Lupinus spp.). The SID for CP and AA were predicted from in vitro analysis by means of a two-step enzymatic method using pepsin and pancreatin incubations. In vitro predicted SID values of CP and AA were generally higher than the corresponding SID values measured in vivo. There were strong linear relationships (r 2 5 0.73 for Lys to r 2 5 0.91 for Cys and Trp) between in vivo and in vitro predicted SID values in the assay feed ingredients if grain legume species (i.e. faba beans, field peas and lupins) was included as a covariate in multiple linear regression analysis. However, to rapidly and accurately predict SID of CP and AA in individual batches of various feed ingredients, further studies are warranted.Keywords: standardised ileal digestibility, in vitro, grain legumes, amino acids, pigs ImplicationsClose linear relationships between in vivo standardised ileal digestibilities (SID) and in vitro predicted SID values for crude protein (CP) and amino acids (AA) in faba beans, field peas and lupins were obtained. However, probably due to the presence of anti-nutritional factors, differences between in vitro predicted SID and in vivo SID values varied between and within these grain legume species. Thus, further validation of the in vitro assay based on the results of in vivo SID studies is required before being used for the prediction of SID of CP and AA in feed ingredients and diets for pigs.

Alternative prediction methods of protein and energy evaluation of pig feeds

“…Only relationship for methionine was poor and not significant ( R 2  = 0.477). Similar results have been obtained by Jezierny et al [92], who found high correlations between SID of protein and AA of grain legumes determined in pigs and predicted in vitro. The highest relationship was obtained for tryptophan, cysteine and histidine ( R 2  = 0.91, 0.91 and 0.89, respectively) and the lowest for lysine ( R 2  = 0.73).…”

“…A close relationship between the SID of AA determined in pigs and the two-step in vitro method of Boisen and Fernandez [10] was confirmed by Święch [91] and Jezierny et al [92]. The SID values of protein and AA of seven feedstuffs (after exclusion of raw soybean) determined in pigs and in vitro were closely related [91], the highest relationships were found for protein, phenylalanine and valine ( R 2  = 0.937, 0.925 and 0.918, respectively) and the lowest for threonine ( R 2  = 0.796).…”

“…It seems that the in vitro method may not be suitable for all types of feedstuffs, because it does not reflect effects of trypsin inhibitor content [28]. In contrast, the in vitro SID of AA is close related to tannin content [28, 92]. …”

Protein quality of pig diets : processing effects on amino acid digestibility and post-absorptive utilization

“…This involves the use of in vivo experiments, which is expensive and laborious (Jezierny et al, 2010). Thus, faster and cheaper methods are required for routine ingredient evaluation.…”

“…This is especially true for processed ingredients and diets, as the wide range in processing conditions increases the variation and influences the protein quality (such as protein solubility, AA content, and protein digestibility; Moughan, 1999). In vitro methods have been used to predict protein digestibility for many ingredients (Boisen and Fernández, 1995;Jezierny et al, 2010). However, studies on in vitro methods that can accurately predict SID of CP for thermally processed ingredients are scarce (for example, Eklund et al, 2015).…”