Chemical composition, true nutrient digestibility, and true metabolizable energy of chicken-based ingredients differing by processing method using the precision-fed cecectomized rooster assay1

Abstract

Chicken-based ingredients are commonly used in pet food products, but vary greatly in nutrient composition and processing conditions that may affect their protein quality and digestibility. Testing the quality of protein sources undergoing different processing conditions provides important information to pet food producers. The objective of this study was to determine the chemical composition, nutrient digestibility, protein, and AA digestibility scores, and nitrogen-corrected true metabolizable energy (TMEn) of chicken-based ingredients that had undergone different processing conditions (i.e., chicken meal, raw chicken, retorted chicken, and steamed chicken) using the precision-fed cecectomized rooster assay. True nutrient digestibility was variable among the protein sources (60% to 76% of DM, 66% to 81% of OM, 83% to 90% of AHF, 50% to 95% of AA and 73% to 85% of TMEn/GE). In general, the chicken meal had a lower (P < 0.05) nutrient digestibility than other ingredients tested, including DM, OM, and most indispensable and dispensable AA, with most having a true digestibility between 75% and 85%. The steamed chicken had the highest indispensable AA digestibilities, with all having a true digestibility greater than 88% and most being over 90%. TMEn value and digestible indispensable AA scores (DIAAS)-like values were higher (P < 0.0001) in the less processed chicken-based ingredients in comparison to chicken meal. Although animal proteins are often considered to be complete proteins, DIAAS-like values <100% suggest that ingredients like chicken meal may not provide all indispensable AA when included at levels to the meet minimal crude protein recommendation. Although raw protein sources are often touted as being the most digestible and of the highest quality, the steamed chicken had the highest (P < 0.0001) DIAAS-like values in this study. This study demonstrates the considerable variability that exists, not only in the chemical composition but also in the true nutrient digestibility among chicken-based ingredients undergoing different processing conditions. These data justify more in vivo testing and the use of DIAAS-like values that consider AA profile, in vivo digestibility, and species-specific recommendations, to evaluate protein-based ingredients intended for use in dog and cat foods.

Use of precision-fed cecectomized rooster assay and digestible indispensable amino acid scores to characterize plant- and yeast-concentrated proteins for inclusion in canine and feline diets1,2

“…These values are similar to the TMEn value reported by Parsons et al (1982) for dehulled soybean meal with a TMEn value of 2.95 kcal/g (DMB). Traditional protein sources used in the pet food industry, such as chicken-based ingredients, have been reported by Oba et al (2019) . Chicken meal was reported to have a TMEn value of 3.72 kcal/g (DMB), whereas raw, steamed, and retorted chicken products had higher TMEn values, with an average of 5.59 kcal/g ( Oba et al, 2019 ).…”

“…Traditional protein sources used in the pet food industry, such as chicken-based ingredients, have been reported by Oba et al (2019) . Chicken meal was reported to have a TMEn value of 3.72 kcal/g (DMB), whereas raw, steamed, and retorted chicken products had higher TMEn values, with an average of 5.59 kcal/g ( Oba et al, 2019 ). The differences observed in the study by Oba et al (2019) is reflective of how processing conditions and variation in the composition of animal-derived protein sources can influence energy content of ingredients, which is also observed, to a lesser extent, among the protein concentrates tested in the current study.…”

“…Minimal data had been reported for DIAAS-like values for use in canine and feline nutrition. Recently, DIAAS-like values have been used to evaluate novel protein sources ( Do et al, 2020 ) and traditional protein sources ( Oba et al, 2019 ) used in companion animal diets. The determination of DIAAS-like scores for both traditional and novel protein sources helps to identify potential complementary protein sources that could be included in diet formulations to meet the requirements for all essential amino acids.…”

“…These results resemble those of the current study, as the first-limiting amino acid for all protein concentrates, with the exception of POP, was methionine. Chicken-based ingredients were evaluated by Oba et al (2019) , which allows for comparison of the novel plant-based protein sources evaluated in the current study to traditional animal proteins. Oba et al (2019) determined the DIAAS-like scores for raw chicken, retorted chicken, steamed chicken, and chicken meal.…”

“…The precision-fed rooster assay has proven to be an accurate model for companion animal nutrition based on its correlation to results from ileal-cannulated dogs ( Johnson et al, 1998 ). Although the use of DIAAS-like scores to evaluate ingredients used in pet foods is only just emerging ( Oba et al, 2019 ; Do et al, 2020 ), it is the recommended method of evaluating protein quality according to the FAO Expert Consultation ( FAO, 2013 ). It was hypothesized that the amino acids in the select protein concentrates would be highly digestible in the cecectomized rooster model and could be considered high-quality protein sources for use in canine and feline diets.…”