Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods.

The determination of amino acid (AA) requirements for mammals has traditionally been done through nitrogen (N) balance studies, but this technique underestimates AA requirements in adult animals. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) technique for the determination of AA requirements in humans, and recently in dogs. However, the determination of AA requirements specific to adult dogs and cats at maintenance is lacking and the current requirements outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirements of indispensable AA (IAA) for the population. To ensure the physiological requirements of our cats and dogs are met, we need methods to accurately and precisely measure digestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animal models and toward in vitro methods. Harmonized static digestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinal tract (GIT) of cats and dogs. The Digestible IAA Score (DIAAS) is one metric that can help define protein quality for individual ingredients or mixed diets that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibility estimates. Finally, we need accurate and reliable laboratory AA analyses to measure the AA present in complete diets, especially those used to quantify methionine (Met) and cysteine (Cys), both often limiting AAs in cat and dog diets. Together, this will guide accurate feed formulation for our companion animals to satisfy requirements while avoiding over-supplying protein, which inevitably contributes to excess N excretion, affecting both the environment and feed sustainability.

Determination of ileal endogenous nitrogen losses and true ileal nitrogen digestibility during non-steady-state conditions of the 15N-isotope dilution technique.

The aim was to determine ileal endogenous nitrogen losses (ENL) and true ileal N-digestibility (TD-N) under non-steady-state conditions of the 15N-isotope dilution technique (15N-IDT), using diets generating low and high ENL and compare results to those obtained under steady-state conditions. Twelve growing pigs (mean LW 22.4 kg) fitted with a post-valve T-caecum cannula were fed an enzyme-hydrolysed casein (EHC)-based diet or an EHC diet + 4% quebracho tannins (QT) and were labelled via continuous 15N-leucine i.v. infusion or twice daily oral 15N-leucine administration. Digesta were collected daily over three consecutive hours with blood plasma sampled on the four consecutive days after cessation of 15N-labelling. There was a significant effect of sampling day on the dilution factor. Endogenous N losses were significantly lower for the EHC than the EHC+QT diet (2.41 vs. 8.69 g/kg DMI), while no significant effect of sampling day was observed. The TD-N of the EHC+QT diet did not differ from the TD-N of the EHC diet (95.1 vs. 92.0%). A significant effect of sampling day was observed for TD-N with day 1 and 2, being higher than day 4. Non-steady-state conditions overestimated ENL by 25-28% as compared to 3 h collections in steady-state conditions, but the relative overestimation was similar for the EHC diet as for the EHC+QT diet. TD-N did not differ significantly compared to 12 h steady-state measurements, but comparison to 3 h steady-state measurements showed that non-steady-state conditions overestimated TD-N for the EHC+QT diet by 9%. However, on day 4 this overestimation disappeared. Using the 15N-IDT during non-steady-state conditions can provide valuable additional data on endogenous N losses and TD-N.

Impact of brining and drying processes on the nutritive value of tambaqui fish (Colossoma macropomum).

Preservation of fish as diet ingredient is challenging in many tropical regions due to poor socioeconomic conditions and lack of freezing facilities. So, alternative preservation techniques could be viable to address the issue. The present study evaluated the effect of brine salting (15% w/v) prior to drying at different temperatures on the nutrient profiles of tambaqui fish (Colossoma macropomum). Whole fish samples (n = 48; 792 ± 16 g; 8 months old) were grouped into two as brine-salted and non-salted, and treated at seven different drying temperatures of 30, 35, 40, 45, 50, 55 and 60°C for a period of 23 h each. To evaluate the impact of Maillard reaction, reactive lysine was also quantified. Drying temperature had no effect on the evaluated macro- and micro-nutrients of tambaqui fish (P > 0.05) while brining reduced the overall protein concentration by 6% (58.8 to 55.4 g/100 g DM; P = 0.004). Brining significantly reduced many amino acids: taurine by 56% (7.1 to 3.1 g/kg; P < 0.001), methionine 17% (14.7 to 12.1 g/kg; P < 0.001), cysteine 11% (5.1 to 4.4 g/kg, P = 0.016), and reactive lysine 11% (52.0 to 46.4 g/kg; P = 0.004). However, alanine, arginine, and serine were not affected by brining (P > 0.05). Brining also reduced the concentrations of Se by 14% (149 to 128 µg/kg DM; P = 0.020), iodine 38% (604 to 373 µg/kg DM; P = 0.020), K 42% (9.71 to 5.61 g/kg DM; P < 0.001) and Mg 18% (1.32 to 1.10 g/kg DM; P = < 0.001) versus an anticipated vast increase in Na by 744% (2.70 to 22.90 g/kg DM; P < 0.001) and ash 28% (12.4 to 16.0 g/100g DM; P < 0.001) concentration. Neither brining nor drying temperature induced changes in % lysine reactivity and fat content of tambaqui fish (P > 0.05). Agreeably, results of multivariate analysis showed a negative association between brining, Na, and ash on one side of the component and most other nutrients on the other component. In conclusion, drying without brining may better preserve the nutritive value of tambaqui fish. However, as a practical remark to the industry sector, it is recommended that the final product may further evaluated for any pathogen of economic or public health importance.

In vitro fermentation potential of gut endogenous protein losses of growing pigs.

Fermentation of dietary and endogenous protein in the hindgut is generally considered detrimental to the health of pigs. We investigated the in vitro fermentation potential of porcine endogenous protein in ileal digesta and colonic mucus, using a N-free buffer with an excess of fermentable carbohydrates. Urea, whey protein isolate (WPI, positive control), WPI hydrolysate (WPIH), and combinations of the latter two were used to validate the assay. A new biphasic model, including a linear end simulation, fitted to the gas production data over a 48-h period identified the time point when substrate fermentation ended. A higher degree of hydrolysis of WPI resulted in a higher maximum gas production rate (Rmax, P < 0.01). Differences in Rmax and the time required to reach Rmax were observed among ileal digesta samples, with Rmax increasing with the insoluble protein content, and the highest Rmax occurring with colonic mucus samples (P < 0.05). The endogenous proteins entering the large intestine of pigs can ferment more rapidly compared to highly soluble and digestible protein sources, with Rmax positively correlated with decreasing solubility of endogenous nitrogenous components.

Protein fermentation in the hindgut of pigs can impact their health, affecting factors like growth rates and feed efficiency. Besides dietary protein, up to 50% of the protein entering the large intestine of growing pigs may be of endogenous origin. Therefore, we explored the fermentation potential of endogenous proteins compared to a well-known protein source, whey protein isolate (WPI). In developing and validating an in vitro gas production technique, we employed urea, WPI, WPI hydrolysate, and various combinations as substrates. The study introduces a new biphasic model for in vitro gas production, offering a detailed analysis of the fermentation process over a 48-h period. Our results revealed that porcine endogenous proteins can undergo rapid fermentation because the maximum gas production rate was higher compared to WPI. This insight is crucial for understanding the dynamics of protein fermentation in pigs. Additionally, we explored the solubility and molecular size of proteins, providing a comprehensive understanding of their fermentation characteristics. We found that endogenous proteins were less soluble compared to WPI but contained more smaller peptides. Unraveling the complexities of protein fermentation in pigs contributes to improvement of feed formulation for optimal gut health.

Protein quality of a small mammal prey and its body organs for felids.

This study evaluated the protein quality of small mammalian prey and its body organs by analyzing amino acid (AA) composition and digestibility of wild adult rats and their body organs (skin/fur, bone, muscle, intestine, liver, kidney, spleen, brain, heart, and lung) utilizing an in vitro digestion method. The average dry matter (DM) digestibility of whole rats was 89.9%. The digestibility of total AA (TAA), total indispensable AA (TIAA), and total dispensable AA (TDAA) in whole rats was 85.6, 87.0, and 87.6%, respectively. Differences in DM digestibility were observed among rat organs, ranging from 59.0% in bone to 99.8% in muscle (P < 0.001). Highly digestible organs generally exhibited AA digestibility exceeding 90%, except for cysteine (Cys) in the intestine and kidney (83.8% and 88.9%, respectively). The digestibility of AAs in skin/fur ranged from 19.7% for Cys to 81.0% for glycine (Gly). In bone, the digestibility spanned from 56.9% for Gly to 81.1% for tyrosine (Tyr). Additionally, examining the digestible indispensable AA score (DIAAS) gives us an idea of the protein quality of small mammalian prey and their body organs. Our results complement information on AA supply and digestion during prey ingestion by felids.

As obligate carnivores, free-ranging felids consume prey and rely on nutrients from animal organs. Studies in adult carnivores such as domestic cats have demonstrated the importance of the dietary amino acid profile. Therefore, this research used rats as a small prey model to analyze the amino acid composition and digestibility of whole prey and its body organs through in vitro digestion methods. Our results add information on amino acid supply and digestion during natural food intake in felids.

Diet composition influences probiotic and postbiotic effects on broiler growth and physiology.

Dietary ingredient and nutrient composition may affect the efficacy of additives in broilers. Specific feed ingredients can represent dietary challenging conditions for broilers, resulting in impaired performances and health, which might be alleviated by dietary probiotics and postbiotics. We assessed the effects of a Lactobacilli probiotic (Pro) and postbiotic (Post) when added to a standard (SD) and challenge (CD) diet. A completely randomized block study with 2 diets (SD, CD) and 3 additive conditions (Control, Pro and Post) involving 1,368 one-day-old Ross male broilers, equally distributed among 36 pens, from d1 to d42 was conducted. Both diets were formulated to contain identical levels of nutrients, with CD formulated to be richer than SD in nonstarch polysaccharides using rye and barley as ingredients. Readout parameters included growth performance parameters, footpad lesions score, blood minerals and biochemical parameters, and tibia health, strength, and composition. Compared to SD, CD decreased BW (1,936 vs. 2,033 g; p = 0.001), increased FCR (p < 0.01) and impaired tibia health and strength (p < 0.05) at d35, thereby confirming the challenging effect of CD. Pro and Post increased BW in CD (+4.7 and +3.2%, respectively, at d35; P < 0.05) but not in the SD group, without affecting FCR. Independently of the diet, Pro increased plasma calcium, phosphorus and uric acid at d21 (+6.2, +7.4, and +15.5%, respectively) and d35 (+6.6, +6.2 and +21.0%, respectively) (P < 0.05) while Post increased plasma magnesium only at d21 (+11.3%; P = 0.037). Blood bile acids were affected by additives in an age- and diet-dependent manner, with some opposite effects between dietary conditions. Diet composition modulated Pro and Post effects on broiler growth performance. Additionally, Pro and Post affected animal metabolism and leg health diet-dependently for some but not all investigated parameters. Our findings show that the effects of pro- and postbiotics on the growth performance and physiology of broilers can be dependent on diet composition and thus possibly other factors affecting diet characteristics.