In Vitro Methods of Assessing Protein Quality for Poultry

Abstract

Protein quality assessment of feed ingredients for poultry is often achieved using in vitro or in vivo testing. In vivo methods can be expensive and time consuming. Protein quality can also be evaluated using less expensive and time consuming chemical methods, termed in vitro. These techniques are used to improve the user’s efficiency when dealing with large sample numbers, and some mimic the physiological and chemical characteristics of the animal digestive system to which the ingredient will be fed. The pepsin digestibility test is the in vitro method of choice for quick evaluation of protein sample during quality control and in most research settings. Even though the pepsin digestibility test uses enzymes to liberate the amino acids from the protein, it does not mimic normal in vivo digestive conditions. The results obtained with this method may be misleading if the samples tested contain fats or carbohydrates which they often do. Multi-enzyme tests have been proposed to overcome the problem encountered when using the pepsin digestibility test. These tests use a combination of enzymes in one or multiple steps customized to simulate the digestive process of the animal. Multi enzyme assays can predict animal digestibility, but any inherent biological properties of the ingredients on the animal digestive tract will be lost.

Trends in feed evaluation for poultry with emphasis on in vitro techniques

“…For details of these methods, refer to reviews by Boisen and Eggum (1991) , Butts et al. (2012) and, Bryan and Classen (2020) .…”

“…In protein solubility tests, either sodium or potassium hydroxide or sodium tetraborate can be used as the alkali solution ( Parsons et al., 1991 ; Lee et al., 1992 ; Bryan and Classen, 2020 ). However, protein dispersibility test involves high speed mixing of a protein sample in water, followed by the assessment of solubility ( Batal et al., 2000 ).…”

“…Although solubility index and dispersibility index methods provide a rating of the protein quality of feed ingredients, but do not give any indication of the amount of nutrient absorbed by the animal. In general, protein solubility and protein dispersibility methods are used as measures of ingredient quality in most poultry nutritional research evaluating high protein ingredients ( Bryan and Classen, 2020 ).…”

NUTRIENT ENHANCEMENT OF PALM KERNEL CAKE VIA SOLID STATE FERMENTATION BY LOCALLY ISOLATED Rhizopus oryzae ME01

“…Moreover, protein quality and presence of nondigestible polysaccharide components such as nonstarch polysaccharide (NSP) in PKC also hindered its maximum utilisation by monogastric animals. Protein quality is closely related to amino acid components bioavailability and animal digestive ability (Bryan and Classen, 2020). Protein quality is also determined by the ability of amino acids to be absorbed by the body which is also known as amino acid digestibility (Alshelmani et al, 2017a).…”

Integrative Structural and Computational Biology of Phytases for the Animal Feed Industry

“…Two enzymes-pepsin and trypsin-with proteolytic activities in the digestive tract of poultry are considered as barriers to proteins and enzymes that are added to industrial chicken diet. Pepsin cleavage sites are at the N-terminals of the aromatic amino acids tryptophan, tyrosine and phenylalanine, while the trypsin cleavage sites are at the C-terminals of arginy1 and Lysy1 peptide bonds [49]. In this section, the contributing factors, as shown in Figure 10, in proteolytic stability are described, as shown in Table 3.…”