A growth trial followed by a digestibility trial were conducted to assess the bioavailability of arginine (Arg) and amino acid digestibility of two feather meals (FeMs) and their pre‐treated counterparts (PTFeMs). Two FeMs, identified as FeM1 and FeM2, were incubated in 200% distilled water (%FeM w/w), with 0.05% of Savinase® 16L (%FeM v/w) and 2% sodium sulphite (%FeM w/w) at 55ºC for 24 hr in a shaking incubator to produce PTFeM1 and PTFeM2 respectively. A basal diet, highly deficient in Arg (12.0 g/kg Arg) was formulated and 10 other diets were formulated to contain 13.5 or 15.0 g/kg Arg by adding increasing amounts of L‐Arg, FeMs or PTFeMs. The experimental diets were fed for 8 weeks using a standard protocol. At 13.5 g/kg Arg, the PTFeMs supported 10.5% to 11.5% higher growth rates (p < 0.05) than their untreated counterparts. The diets formulated with PTFeMs presented 3.5%–4.5% and 2.7%–5.9% higher (p < 0.05) apparent digestibility coefficients of protein when compared to the diets containing the FeM counterparts at 13.5 and 15.0 g/kg Arg respectively. The results from this study demonstrate the potential of the pre‐treatment to improve the nutritive value of FeMs in rainbow trout.

A digestibility trial was carried to assess the apparent digestibility coefficient (ADC) of crude protein (CP) and amino acids (AA) in two feather meals (FeM) of different origin (FeM1 and FeM2) and in their enzymatically pre‐treated ingredient stream (PTFeM1 and PTFeM2) in rainbow trout. The ADC of CP was 11%–17% higher (p < 0.05) in the PTFeMs than in their FeM counterparts. There was no difference (p > 0.05) of ADC of CP among FeMs and among PTFeMs. The FT‐Raman analysis showed a reduction in concentration and conformational stability of disulphide bonds in the PTFeMs when compared to their FeM counterparts. Moreover, important discrepancies in disulphide concentration were observed between FeMs and between PTFeMs. These observations suggest that the ADC of CP in FeM is not only governed by disulphide bond content and other variables should be considered. Higher concentrations of the cross‐linked amino acids (CLAA) lanthionine, lysinoalanine and β‐aminoalanine were measured in FeM1 and PTFeM1 as compared to FeM2 and PTFeM2 respectively. Previous studies have suggested inverse relationships between CLAAs and the digestibility as well as bioavailability of AAs in feed ingredients. A previous study conducted in our laboratory showed a lower (p < 0.05) bioavailability of arginine in FeM1 and PTFeM1 than in FeM2 and PTFeM2, respectively, in rainbow trout. Our results suggest that (a) the digestibility of AAs in FeM may be affected by disulphide bond content and the presence of CLAAs, and (b) CLAA content may be indicator of bioavailability of AAs in FeM.

There is dearth of knowledge with regards to mineral digestibility of ingredients in canines, and current knowledge is focused on the digestibility of supplemented minerals, not on intrinsic mineral digestibility of ingredients. The objectives of the present study were to determine the apparent and true digestibility (TD) of macronutrients and micronutrients, and the total tract gastrointestinal endogenous nutrient outputs in canines fed either animal-or vegetable-based adult maintenance diets. Eight purpose bred Beagles (two intact males, six spayed females) of similar age (2.12 ± 0.35 yr, mean ± SD) and weight (9.92 ± 0.73 kg, mean ± SD) were pair housed in kennels but fed individually based on individual maintenance energy requirements. Two basal diets (animal and vegetable protein based) were formulated to meet nutritional requirements of adult canines. Two additional trial diets were created, using the basal diets, by diluting diets by 50% with anhydrous α-d-glucose to attempt to quantify endogenous mineral losses and enable calculation of TD. All diets contained titanium dioxide at 0.3% for calculations of nutrient digestibility. Dogs were provided with deionized water as their only source of water throughout the trial. Dogs in a specific kennel were randomly assigned to an experimental diet for 10 d (experimental period), and fecal samples were collected the last 4 d of each period. All dogs were fed all experimental diets in random order based on a 4 × 4 replicated Latin square design. Dogs fed intact diets had a higher apparent mineral digestibility compared to dogs fed diluted diets (P < 0.05). Apparent phosphorus digestibility was higher for dogs fed the diet 2 compared with the diet 1 (P = 0.01) and the diluted diets (P < 0.001). There was a trend towards a greater TD of Cu for dogs fed the diet 2 compared with the diet 1 (P = 0.08). P, Mg, Zn, and Mn true digestibilities were higher for dogs fed the diet 2 compared with the diet 1 (P < 0.05, P = 0.01, P = 0.02, P = 0.009, respectively). These results suggest that apparent and TD do not result in similar values. Further research should be conducted on TD in canines only if a better model is developed.

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This study describes the process of developing an enzymatic pretreatment to improvethe nutritional value of feather meal (FeM). In a first experiment, a full factorial design was used toexamine the effects of various incubation conditions on the solubilization of nitrogen in FeM. Weincubated FeM for 3 h with various levels of a commercial alkaline serine protease (Savinase®16L), sodium sulphite (Na2SO3), and digestion buffer. A Savinase® 16L level of 3% (%FeM v/w),Na2SO3 level of 3% (%FeM w/w), and digestion buffer level of 500% (%FeM w/w) were identifiedas the optimal conditions. Under these optimal conditions, 45% of the nitrogen in FeM wassolubilized. In a second experiment, we evaluated the effect of more economically sustainableincubation conditions on the in vitro digestibility of protein (pepsin-HCl digestibility andmultistep protein evaluation) in FeM. Two FeMs were incubated with 0.5% Savinase® 16L (%FeMv/w), 2% Na2SO3 (%FeM w/w), and 200% buffer (%FeM w/w) for 24 h. The pretreatment improvedpepsin-HCl digestibility by 7%–16% and the total tract degradable protein content by 14%–50%.Accordingly, this novel pretreatment could be applied in the animal feed industry to improve thenutritional value of FeM.