Healthy Ageing Is Associated with Preserved or Enhanced Nutrient and Mineral Apparent Digestibility in Dogs and Cats Fed Commercially Relevant Extruded Diets

Age-related changes in gastrointestinal function have been reported in companion animals, but the impact on digestive efficiency remains uncertain. Healthy dogs (n = 37; 2.6–14.2 years) received four diets varying in total dietary fibre (TDF; 6–29%, as fed). Healthy cats (n = 28; 1–13 years) received four diets with two fat (10–12%; 17–18%) and TDF (9 and 12%) levels. In a crossover design, diets were provided over four consecutive 10-day cycles, including a 4-day faecal collection. Apparent crude protein (CP), ether extract (EE), TDF, calcium (Ca), and phosphorus (P) digestibilities were determined. The effect of age was analysed as a continuous variable in dogs and as differences between adult (1–5 years) and senior (7–13 years) cats. In dogs, EE digestibility was unaffected by age (p > 0.10). Dogs of 6–12 years had higher digestibility of CP (p = 0.032), TDF (p = 0.019), Ca (p = 0.019), and P (p = 0.024) when fed the 6% TDF diet. Senior cats had greater digestibility of TDF (p < 0.01) and Ca (p = 0.024) but had lower EE and CP digestibility with one diet (17% fat; 9%TDF) (age, p > 0.10; diet × age, p < 0.001). Healthy ageing was associated with preserved nutrient digestibility in dogs and cats within the age ranges studied. The effect of ingredient sources in senior cats warrants further investigation.

Metaproteomics—An Advantageous Option in Studies of Host–Microbiota Interaction

Gut microbiome contributes to host health by maintaining homeostasis, increasing digestive efficiency, and facilitating the development of the immune system. Manipulating gut microbiota is being recognized as a therapeutic target to manage various chronic diseases. The therapeutic manipulation of the intestinal microbiome is achieved through diet modification, the administration of prebiotics, probiotics, or antibiotics, and more recently, fecal microbiome transplantation (FMT). In this opinion paper, we give a perspective on the current status of application of multi-omics technologies in the analysis of host–microbiota interactions. The aim of this paper was to highlight the strengths of metaproteomics, which integrates with and often relies on other approaches.

Egg nutritional modulation with amino acids improved performance in zebrafish larvae

New and more efficient methods to sustainably intensify Aquaculture production are essential to attain the seafood demand for direct human consumption in the near future. Nutrition has been identified as one strategy of early exposure that might affect animal early development and later phenotype. This strategy may have positive consequences in the modulation of fish digestive physiology, which will correlate with higher performance outputs. Thus, improving fish digestive efficiency will lead to higher productivity and lower biogenic emission from aquaculture facilities, minimising the impact on the environment while increasing the biological efficiency. An innovative in ovo nutritional modulation technique based on low-frequency ultrasounds was used to enhance the transport of amino acids across the embryo membranes. An early stimulus with either arginine or glutamine, both involved in gut maturation, was applied in zebrafish (Danio rerio) embryos at 3.5 hours post-fertilization (hpf). At 22 days post-fertilization (dpf), growth performance, digestive enzyme activities and gut microbiota composition were analysed to evaluate the larval nutrition-induced metabolic plasticity and the effects on fish digestive efficiency. Results showed that fish survival was not affected either by the sonophoresis technique or amino acid supplementation. Final dry weight at 22 dpf was statistically higher in larvae from glutamine treatment when compared to the control even with lower trypsin activity, suggesting a higher nutrient digestion capacity, due to a slightly modulation of gut microbiota. Higher arginine supplementation levels should be tested as strategy to enhance growth at later developmental stages. In conclusion, this study demonstrated the efficiency of sonophoresis technique for in ovo nutritional modulation and suggests that in ovo glutamine supplementation might promote growth at later developmental stage through a positive microbiota modulation.

Prenatal and Postnatal Nutrition Influence Pancreatic and Intestinal Carbohydrase Activities of Ruminants

In ruminant livestock species, nutrition can play an important role in the long-term programming of gastrointestinal function. Pancreatic and small intestinal digestive enzymes are important for postruminal digestion of carbohydrates and protein. Carbohydrases have been shown to respond to changes in the level of feed intake and the dietary inclusion of specific nutrients, including arginine, butyrate, folic acid, fructose, and leucine. Understanding how diet influences enzyme development and activity during prenatal and postnatal life could lead to the development of dietary strategies to optimize offspring growth and development to increase digestive efficiency of ruminant livestock species. More research is needed to understand how changes in fetal or neonatal carbohydrase activities in response to nutrition influence long-term growth performance and efficiency in ruminant livestock species to optimize nutritional strategies.

Abstract P239: Diet Modifies Cardiometabolic Effects Of DOCA-salt In C57BL/6J Mice

The deoxycorticosterone acetate (DOCA)-salt model of hypertension is widely used to investigate the neurohormonal regulation of blood pressure. We investigated the modulatory effect of three common “chow” diets upon cardiometabolic consequences of DOCA-salt treatment in mice. Male C57BL/6J mice (6 wks of age) were randomly assigned to 5L0D (LabDiet 67138, 4.0 g Na/kg), a Soy-free extruded diet (Envigo 2920, 1.5 g Na/kg), or an NIH-31 modified open formula diet (Teklad 7913, 3.1 g Na/kg) and provided with autoclaved deionized water for 3 weeks (n=16/diet). At 9 weeks of age (ie, before DOCA-salt), intake behaviors and energy flux were assessed using metabolic caging and bomb calorimetry. Before DOCA-salt, body mass, digestive efficiency, energy efficiency, total sodium intake, urine volumes, and apparent sodium & potassium retentions (ie, ingested-urine loss) were significantly modified by diet (p<0.05), but calories absorbed per day was not. Mice (n=8/diet) were then implanted with a DOCA pellet (50mg, sc) and provided 0.15 M NaCl as an additional drink option, or underwent sham surgery (n=8/diet). At 12 weeks of age (ie, after DOCA-salt), intake behaviors and energy flux were again assessed before tissue harvest. After DOCA-salt, body mass, energy efficiency, total sodium intake, urine volume, apparent sodium retention, and renal renin mRNA were significantly affected by a diet x DOCA-salt interaction (p<0.05). In contrast, digestive efficiency and apparent potassium retention were modified by diet (p<0.05), and calories absorbed per day, plasma sodium, and plasma potassium were affected by main effects of diet (p<0.05) and DOCA-salt (p<0.05), but these endpoints were not modified by a diet x DOCA-salt interaction. Combined with analyses of tissue masses, expression of various renal electrolyte transporters, blood chemistries, and urinalyses, these many endpoints highlight a multitude of cardiometabolic outcomes of the DOCA-salt model that are sensitive to environmental contexts such as diet. Ongoing work is investigating the modulatory effect of diet upon increases in total body sodium retention and blood pressure induced by DOCA-salt treatment, and roles for varied sodium vs protein contents of the diets in these effects.

Abstract P249: ICV Infusion Of AgRP Modulates Feeding Behavior And Energy Expenditure In Mice

A subset of Agouti-related protein (AgRP) neurons within the arcuate nucleus express angiotensin type 1a receptors (AT1A), and genetic ablation of AT1A in these cells disinhibits AgRP gene expression and attenuates energy expenditure (EE) in mice. To further understand the role of AgRP in metabolic control, and to establish relevant dosing schedules in this species, here we tested the effect of intracerebroventricular infusion (icv) of recombinant AgRP on metabolic functions in C57BL/6J male mice. First, we examined the effects of AgRP(82-132) (21 days, 1 or 10 nmol/d, icv) or artificial cerebrospinal fluid (aCSF) using metabolic cages. High dose AgRP reduced body mass (aCSF n=12, +0.8±0.6 vs 1 nmol/d n=14, +0.6±0.6 vs 10 nmol/d n=11, -1.5±0.5 p<0.05 g/21d), without affecting food intake (15.1±1.2 vs 14.1±1.1 vs 16.3±1.1 kcal/d) or digestive efficiency (85.2±0.5 vs 84.5±0.7 vs 85.1±0.6 %), but a significant reduction in energy efficiency (+3.8±2.0 vs +2.7±2.8 vs -5.9±2.2 p<0.05 mg/kcal) indicated increased total EE. Next, we examined the effect of AgRP(82-132) (14 days, 1 nmol/d, icv) using a multiplexed system (Promethion, Sable). AgRP had no effect on body mass (25.1±1.2, n=8 vs 26.7±0.5, n=8), overall body composition (by NMR), heat production (Weir, 24h: 0.485±0.015 vs 0.490±0.022 kcal/h), or respiratory exchange ratio (0.88±0.01 vs 0.89±0.01). AgRP increased total food intake (10.1±0.6, n=8 vs 11.9±0.5, n=8, kcal/d, p=0.03) through a synergistic effect on number of meals and median meal mass. We conclude that AgRP (1-10 nmol/d, 2-3 wk, icv) infusion causes subtle changes in feeding behavior without effect on digestive efficiency. In contrast, EE is paradoxically increased by AgRP when infused at a high dose (10 nmol/d). We postulate that these differences may reflect differential accessibility of the peptide to relevant feeding vs autonomic control regions of the hypothalamus when infused into the cerebral ventricles, and/or compensatory increases in EE secondary to changes in feeding behavior. Future studies to deconvolute the role of AgRP in the control of EE in mice will require site-specific delivery of the peptide to relevant target regions or manipulation of its receptor in those regions. Funding: HL134850, HL084207