Comparing the standardized amino acid digestibility of an alternative protein source with commercially available protein-based ingredients using the precision-fed cecectomized rooster assay

Abstract

Using single-cell-based proteins in pet foods is of interest, but little testing has been done. Therefore, our objective was to determine the amino acid (AA) digestibilities, assess protein quality of a novel microbial protein (MP) (FeedKind), and compare it with other protein-based ingredients using the precision-fed cecectomized rooster assay. Test ingredients included: MP, chicken meal (CM), corn gluten meal (CGM), pea protein (PP), and black soldier fly larvae. Thirty cecectomized roosters (n = 6/ingredient) were randomly assigned to test ingredients. After 24 h of feed withdrawal, roosters were tube-fed 15 g test ingredient and 15 g corn, and then excreta were collected for 48 h. Endogenous AA corrections were made using additional roosters. Digestible indispensable AA score (DIAAS)-like values were calculated to determine protein quality according to Association of American Feed Control Officials (AAFCO), The European Pet Food Industry Federation, and National Research Council reference values for growing and adult dogs and cats. Data were analyzed using the Mixed Models procedure of SAS 9.4, with P ≤ 0.05 being significant. All reactive lysine:total lysine ratios, an indicator of heat damage, were higher than 0.9, except for CM (0.86). Digestibility of indispensable and dispensable AA were >85% and >80% for MP, respectively, with indispensable AA digestibilities being >80% for all other ingredients. In general, CGM had the highest, while CM had the lowest AA digestibilities. Two exceptions were lysine and tryptophan. Lysine digestibility for MP was higher than that of all other ingredients, while tryptophan digestibility for MP was higher than that of CM, CGM, and PP. Threonine digestibility was highest for CGM and MP. Valine digestibility was highest for CGM, PP, and MP. DIAAS-like calculations identified limiting AA of each ingredient and depended on the reference used and life stage and species of animal. Using AAFCO guidelines, all DIAAS-like values for MP were >100 suggesting that it could be used as the sole source of protein in adult dog and cat diets; only methionine had DIAAS-like values <100 for growing kittens. For dogs, limiting AA was most commonly methionine, threonine, and tryptophan in the other protein sources. For cats, limiting AA was most commonly lysine and methionine. Lysine was severely limited in CGM across all life stages considered. Further research in dogs and cats is necessary, but our data suggest that the MP tested has high AA digestibilities and is a high-quality protein source that may be useful in pet foods.

Keywords: canine nutrition; feline nutrition; microbial protein; nutrient digestion; pet food; single-cell protein.

Figure 1.

Digestible indispensable AA score (DIAAS)-like values of various protein-based ingredients for adult dogs at maintenance. CM, chicken meal; CGM, corn gluten meal; PP, pea protein; MP, microbial protein; BSFL, black soldier fly larvae. ^a,b,c,d,eMeans with different superscripts within guidelines (NRC, AAFCO, or FEDIAF) differ (P < 0.05); n = 6 roosters per treatment. DIAAS-like % = 100 × [(mg of digestible dietary indispensable AA in 1 g of the dietary protein)/(mg of the minimum recommendation of the same dietary indispensable AA in 1 g of the minimum protein recommendation)]. DIAAS-like values were calculated from AA digestibility values from cecectomized roosters and Association of American Feed Control Officials (AAFCO, 2023) nutrient profiles, National Research Council (NRC, 2006) recommended allowances, and The European Pet Food Industry (FEDIAF, 2021) nutritional guidelines for adult dogs at maintenance.

Figure 2.

Digestible indispensable AA score (DIAAS)-like values of various protein-based ingredients for growing puppies after weaning. CM, chicken meal; CGM, corn gluten meal; PP, pea protein; MP, microbial protein; BSFL, black soldier fly larvae. ^a,b,c,d,eMeans with different superscripts within guidelines (NRC, AAFCO, or FEDIAF) differ (P < 0.05); n = 6 roosters per treatment. DIAAS-like % = 100 × [(mg of digestible dietary indispensable AA in 1 g of the dietary protein)/(mg of the minimum recommendation of the same dietary indispensable AA in 1 g of the minimum protein recommendation)]. DIAAS-like values were calculated from AA digestibility values from cecectomized roosters and Association of American Feed Control Officials (AAFCO, 2023) nutrient profiles, National Research Council (NRC, 2006) recommended allowances, and The European Pet Food Industry (FEDIAF, 2021) nutritional guidelines for growing puppies after weaning.

Figure 3.

Digestible indispensable AA score (DIAAS-like) values of various protein-based ingredients for adult cats at maintenance. CM, chicken meal; CGM, corn gluten meal; PP, pea protein; MP, microbial protein; BSFL, black soldier fly larvae. ^a,b,c,d,eMeans with different superscripts within guidelines (NRC, AAFCO, or FEDIAF) differ (P < 0.05); n = 6 roosters per treatment. DIAAS-like % = 100 × [(mg of digestible dietary indispensable AA in 1 g of the dietary protein)/(mg of the minimum recommendation of the same dietary indispensable AA in 1 g of the minimum protein recommendation)]. DIAAS-like values were calculated from AA digestibility values from cecectomized roosters and Association of American Feed Control Officials (AAFCO, 2023) nutrient profiles, National Research Council (NRC, 2006) recommended allowances, and The European Pet Food Industry (FEDIAF, 2021) nutritional guidelines for adult cats at maintenance.

Figure 4.

Digestible indispensable AA score (DIAAS)-like values of various protein-based ingredients for growing kittens after weaning. CM, chicken meal; CGM, corn gluten meal; PP, pea protein; MP, microbial protein; BSFL, black soldier fly larvae. ^a,b,c,d,eMeans with different superscripts within guidelines (NRC, AAFCO, or FEDIAF) differ (P < 0.05); n = 6 roosters per treatment. DIAAS-like % = 100 × [(mg of digestible dietary indispensable AA in 1 g of the dietary protein)/(mg of the minimum recommendation of the same dietary indispensable AA in 1 g of the minimum protein recommendation)]. DIAAS-like values were calculated from AA digestibility values from cecectomized roosters and Association of American Feed Control Officials (AAFCO, 2023) nutrient profiles, National Research Council (NRC, 2006) recommended allowances, and The European Pet Food Industry (FEDIAF, 2021) nutritional guidelines for growing kittens after weaning.