Freeze-dried Diet Research Articles

193 Apparent Total Tract Nutrient Digestibility of Frozen Raw, Freeze-Dried Raw, Fresh, and Extruded Dog Foods and Their Effects on Fecal Characteristics and Metabolites of Adult Dogs

Abstract Various pet food diet formats are now available. Processing methods are known to impact nutrient digestibility and are thought to affect pet health but are poorly studied. Therefore, the objective of this study was to determine the apparent total tract macronutrient digestibility (ATTD) of frozen raw, freeze-dried raw, fresh, and extruded dog foods and assess their effects on fecal characteristics, and fecal metabolites of healthy adult dogs. Ten healthy adult spayed female dogs were used in a replicated 5x5 Latin square study to test the following diets: Chicken and Barley Recipe [extruded diet; Hill’s Science Diet (EXT)], Chicken and White Rice Recipe [fresh diet; Just Food for Dogs (FRSH)], Chicken Formula [raw frozen diet; Primal (FRZN)], Chicken and Sorghum Hybrid Freeze-dried Formula [hybrid freeze-dried raw diet; Primal (HFD)], and Chicken Dinner Patties [raw freeze-dried diet; Stella & Chewy (FD)]. The experiment was composed of five 35-day periods. Total feces excreted during a 5-day total collection phase was frozen until analyses and ATTD calculations. On the first day of fecal collections, one fresh fecal sample was collected for measurement of pH, dry matter (DM) content, and bile acid (BA) and fermentative metabolite concentrations. Data were analyzed statistically by Mixed Models using SAS 9.4, with P < 0.05 being significant. Widespread differences were noted among diets. Wet and DM fecal output was greater for EXT than other diets, and wet fecal output was greater for FRSH than FRZN, HFD, and FD. Protein ATTD was greater for FRZN and FD than other diets, and greater for HFD than FRSH and EXT. Fat ATTD was greater for HFD than FRZN and EXT, and less for EXT than other diets. Fecal pH was less in EXT and FRSH than other diets. Fecal scores were greater (looser) in EXT and FRSH than FRZN and FRZDR. Fecal DM% was greater in FD than other diets, and greater in FRZN and HFD than EXT and FRSH. In general, fecal short-chain fatty acids were highest in EXT, intermediate in FRSH and HFD, and least in FRZN and FD. Fecal branched-chain fatty acids were greatest in FDF, intermediate in EXT, FRZN, and FD, and least for FRSH. Fecal phenols and indoles were greatest in HYB and least in FRSH, with others being intermediate. Fecal primary BA were greater in FRSH than other diets, while fecal secondary BA were greater in FRZN than HFD, FRSH, and EXT, greater in FD than FRSH and EXT, and greater in HFD than FRSH. In summary, the diets tested were very different in regard to nutrient digestibility, fecal characteristics, and fecal metabolites. More research is necessary to distinguish how ingredient source, diet processing, macronutrient composition, and other factors may contribute to these differences.

PSVIII-18 Standardized Amino Acid Digestibility and Nitrogen-Corrected True Metabolizable Energy of Frozen Raw, Freeze-Dried Raw, Fresh, and Extruded Dog Foods Using Cecectomized and Conventional Rooster Assays

Abstract Processing conditions, particularly temperature and duration of heating, impact the digestibility of pet foods. Various alternative commercial pet food formats are now available, but few have been well tested. Therefore, the objective of this study was to determine the amino acid (AA) digestibility and nitrogen-corrected true metabolizable energy (TMEn) of frozen raw, freeze-dried raw, fresh, and extruded dog foods using the precision-fed cecectomized and conventional rooster assays. The diets tested were Chicken and Barley Recipe [extruded diet; Hill’s Science Diet (EXT)], Chicken and White Rice Recipe [fresh diet; Just Food for Dogs (FRSH], Chicken Formula [raw frozen diet; Primal (FRZN)], Chicken and Sorghum Hybrid Freeze-dried Formula [hybrid freeze-dried raw diet; Primal (HFD)], and Chicken Dinner Patties [raw freeze-dried diet; Stella & Chewy (FD)]. Two precision-fed rooster assays utilizing Single Comb White Leghorn roosters (1.5 to 2.5 yr, 2.5 to 3 kg) were conducted. In the first assay, 20 cecectomized roosters (n = 4/treatment) were used to determine AA digestibility. In the second assay, 20 conventional roosters (n = 4/treatment) were used to determine TMEn. In both assays, roosters were crop intubated with 12 g of test diet and 12 g of corn, and then excreta were collected for 48 h. The reactive lysine:total lysine ratios were 0.94, 0.96, 0.93, 0.93, and 0.95 for the EXT, FRSH, FRZN, HFD, and FD diets, respectively. In general, FD had the greatest AA digestibilities and EXT had the least AA digestibilities. Arginine digestibilities were different (P < 0.05) across all diets and in this pattern: FD > FRZN > FRSH > HFD > EXT. Isoleucine digestibilities were different (P < 0.05) across all diets, but with a slightly different pattern: FD > FRZN > FRSH > EXT > HFD. Lysine digestibility was greater (P < 0.05) in FD and FRZN than EXT, with other diets being intermediate. Methionine digestibility was greater (P < 0.05) in FD than FRSH, with other diets being intermediate. Threonine digestibility was greater (P < 0.05) in FD than EXT, with other diets being intermediate. Valine digestibilities were different (P < 0.05) across all diets and in this pattern: FD > FRZN > EXT > FRSH > HFD. Digestibilities of the other essential AA were not different among diets. TMEn was greater (P < 0.05) in FRZN than FD, FRSH, and EXT, greater (P < 0.05) in HFD than FRSH and EXT, and greater (P < 0.05) in FD than EXT. In conclusion, our results support the notion that diet processing impacts AA digestibility, with freeze-dried raw, frozen raw, and fresh diets consistently having greater digestibility coefficients, as well greater TMEn, than the extruded diet. More research in dogs is necessary to test the effects of these diet formats on palatability, digestibility, stool quality, and other physiologically relevant outcomes.

Standardized amino acid digestibility and nitrogen-corrected true metabolizable energy of frozen and freeze-dried raw dog foods using precision-fed cecectomized and conventional rooster assays.

Commercial raw or minimally-processed diets, often referred to holistically as raw meat-based diets (RMBD) represent a small portion of the pet food market, but the growth of this sector has been significant in recent years. While traditionally, high-moisture, frozen options were the standard format of commercially available raw diets, freeze-dried raw diets have become more prevalent as of late. Despite the increasing popularity of these commercial raw diet formats, there is a dearth of literature describing their nutritional properties, particularly regarding freeze-dried diets. Therefore, the objective of this experiment was to determine and compare the standardized amino acid (AA) digestibilities and nitrogen-corrected true metabolizable energy (TMEn) of raw frozen and freeze-dried dog foods using precision-fed cecectomized and conventional rooster assays. Three formats of frozen or freeze-dried raw diets provided by Primal Pet Foods (Fairfield, CA, USA) were tested: traditional freeze-dried nuggets (T-FDN), hybrid freeze-dried nuggets (H-FDN), and frozen nuggets (FZN). Diets were fed to cecectomized roosters (4 roosters/diet) to determine AA digestibilities, while conventional roosters (4 roosters/diet) were used to determine TMEn. In both cases, after 26 h of feed withdrawal, roosters were tube-fed 12 to 13 g of test diets and 12 to 13 g of corn. Following crop intubation, excreta were collected for 48 h. Endogenous corrections for AA were made using five additional cecectomized roosters. All data were analyzed using the Mixed Models procedure of SAS version 9.4. There were no significant differences in standardized AA digestibilities among diets, with digestibilities being high for all diets tested. For most of the indispensable AA, digestibilities were greater than or equal to 90% for all diets. Histidine and lysine were the exceptions, with digestibilities ranging from 82% to 87% and 87% to 92%, respectively. Moreover, the reactive lysine:total lysine ratio, a measure of heat damage, ranged from 0.91 to 0.95. TMEn values were higher (P = 0.0127) in T-FDN (6.1 kcal/g) and FZN (5.9 kcal/g) than H-FDN (5.3 kcal/g) and were most similar to those estimated by Atwater factors. In general, all diets tested had high AA digestibilities and had TMEn values that were most similar to Atwater factors.

104 Standardized Amino Acid Digestibility of Three Formats of Freeze-Dried dog Foods Using the Precision-fed Cecectomized Rooster Assay

Abstract Freeze-dried pet foods represent a small segment of the pet food market, but its growth has been significant in recent years. Despite their increasing popularity, freeze-dried diets have not been well tested. Therefore, the objective of this experiment was to determine and compare the standardized amino acid (AA) digestibilities of freeze-dried dog foods using the precision-fed cecectomized rooster assay. Three formats of freeze-dried diets provided by Primal Pet Foods (Fairfield, CA) were tested: traditional freeze-dried nuggets (FDN), low-temperature freeze-dried nuggets (LTN), and a hybrid freeze-dried nugget (HN). All animal care procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation. Twelve cecectomized roosters (4 roosters per substrate) were randomly assigned to the three test substrates. After 24h of feed withdrawal, roosters were tube-fed 12-13g of test substrates and 12-13g of corn. Following crop intubation, excreta (urine and feces) were collected for 48h. Endogenous corrections for AA were made using 5 additional cecectomized roosters. All data were analyzed using the Mixed Models procedure of SAS version 9.4. There were no significant differences in standardized AA digestibilities among diets, with digestibilities being high for all tested. For most of the indispensable AA, digestibilities were greater than 90% for all diets (arginine: 94.1%-95.6%; isoleucine: 91.2%-93.1%; leucine: 92.4%-95.3%; methionine: 92.8%-94.9%; phenylalanine: 90.8%-93.6%; tryptophan: 96.2%-98.6%; valine: 90.2%-92.9%). Histidine, lysine, and threonine were the exceptions, with digestibilities ranging from 81.7%-86.6%, 86.7%-91.7%, and 89.6%-91.7%, respectively. Moreover, the reactive:total lysine ratio, a measure of heat damage, ranged from 0.91 to 0.95. In general, the low-temperature nugget had thegreatest numerical AA digestibilities, likely due to reduced heat damage, but all diets performed very well.

Influence of Freeze-Dried Diet on Oral Hygiene Indicators in Strict Isolation Condition of an Analog Space Mission.

Analog space missions were created to study the human factor in extraordinary conditions that would occur in future space habitats. Isolation has been shown to cause stress and disrupt individuals’ daily routine, which can also affect their oral hygiene and lead to an increased risk of dental caries and gingivitis. The astronauts’ specific freeze-dried diet is associated with “lazy” chewing, potential dehydration and vitamin A deficiency, which may adversely affect their saliva. The aim of this study is to investigate the influence of the freeze-dried diet on selected oral hygiene indicators in analog astronauts (AA) enduring strict isolation conditions during six consecutive analog space missions at the LunAres Research Station. During the experiment the oral hygiene and gingival inflammation status measurements were conducted on the group of AAs at the beginning and at the end of each mission. Measurements included four oral hygiene indicators: API, sOHI, PI by Silness and Loe and GBI by Ainamo and Bay. Each AA’s individual scores were noted and analyzed. Statistically significant reduction in the amount of plaque and intensity of gingival bleeding was observed over the course of the study, which could indicate positive results of applied oral hygiene procedures despite unfavorable dietary and stressful isolation conditions.

Real-time quantification of the immune gene expression in rainbow trout fed different forms of probiotic bacteria Lactobacillus rhamnosus

Whether it is better to use viable or non-viable probionts in aquaculture is still a matter of debate. In this study, the molecular immunomodulation in rainbow trout Oncorhynchus mykiss induced by viable or killed forms of the probiont Lactobacillus rhamnosus JCM 1136 was investigated. Three forms of this probiont: (1) heat-killed (HK), (2) live spray (LI) and (3) freeze-dried (FD) were incorporated into a basal (control) diet for rainbow trout O. mykiss. The LI and FD diets are referred to as viable diets. A rearing trial, in triplicate, was conducted for 30 days, with the control and probiotic diets as treatments. The cytokine genes such as the tumour necrosis factor (TNF), transforming growth factor (TGF-β), interferon (IFN) and immune gene Immunoglobulin (Ig) found in tissues from the kidney and spleen were assessed for their expression pattern by real-time polymerase chain reaction. The tested immune genes were up-regulated in the treatment groups, sometimes even in many folds like in the case of the Ig gene. The TNF gene was found to be highly (P<0.05) up-regulated (5000-fold) in groups fed both viable forms (LI, FD). With regard to the TGF-β gene, the spleen of the HK and FD groups showed significant up-regulation of 20- and 30-folds respectively. The IFN gene was up-regulated (P<0.05) in all treatments, but more in the viable diet treatments. Kidney and spleen tissues showed similar expression patterns, i.e. all of these genes were up-regulated more with the viable diets that with the control, and in most cases, the viable diets induced a higher expression of the immune genes than the HK diet.

Using combinatorics to screen Bacillus thuringiensis isolates for toxicity against Manduca sexta and Plutella xylostella

Screening Bacillus thuringiensis (Bt) isolates or strains for toxicity has traditionally been performed with one bacterial isolate at a time versus a specific insect. By testing Bt strains in groups, we more rapidly identified 28 of 147 Bt isolates as toxic to either diamondback moth, Plutella xylostella (L.), or tobacco hornworm, Manduca sexta (L.). The use of freeze-dried diet and directed pooling of isolates for toxicity testing decreased the number of bioassays required to identify toxic strains by as much as 60% for a given group of isolates. Three of the B. thuringiensis isolates were more toxic to diamondback moth than a standard commercial strain. This method parallels the concept of combinatorics used for screening compounds in the pharmaceutical industry by the use of bacterial strains rather than chemicals.

ATTRACTIVENESS AND EFFECTIVENESS OF AN ARTIFICIAL DIET FED TO HYBRID IMPORTED FIRE ANTS, SOLENOPSIS INVICTA × RICHTERI (HYMENOPTERA: FORMICIDAE)

Abstract Attractiveness of freeze-dried and reconstituted entomophage diet to hybrid fire ants (Solenopsis invicta × richteri) was investigated in choice tests using freeze-killed, crushed cricket (Acheta domestica L.) as a standard. Worker ants were strongly attracted to both crickets and reconstituted diet. Foragers collected approx. 27 times more reconstituted diet than freeze-dried diet, and collected statistically equivalent amounts of artificial diet and crickets (36.0 ± 7.0 and 26.0 ± 0.3 mg/h, respectively). Even though workers were strongly attracted to the artificial diet, all measures of colony growth (mean mass of brood, workers, and queen) were at least 30% lower in colonies fed sugar water + artificial diet than in colonies fed sugar water + crickets or sugar water + artificial diet + crickets. While this diet may have some utility as a bait for monitoring fire ants in the field, it offers no advantage over a standard diet of crickets and sugar water for rearing fire ants in the laboratory.

A freeze-dried diet to test pathogens of Colorado potato beetle

The Colorado potato beetle is an important pest on potato, eggplant, and tomato. Because Colorado potato beetles develop resistance to insecticides quickly, new methods are needed for control. Bacillus thuringiensis is the only bacterium to successfully control Colorado potato beetle. Until recently, one of the drawbacks to testing bacteria against the Colorado potato beetle has been the lack of an artificial diet for screening. Previous artificial diets will only be consumed by Colorado potato beetle larvae when fresh. To improve storage, we developed a freeze-dried diet, based on a 96-well plate, suitable to feed larvae for the duration of a bioassay. Individual diet components were tested both for their effect on insect growth and on pathogen toxicity. When the preservatives, methylparaben and sorbic acid, were removed from the diet, the average weight of second instar larvae increased from 7.9 mg to greater than 9.8 mg. The preservatives inhibited the growth of two of the bacteria tested, Photorhabdus luminescens HM and Chromobacterium sp. PRAA. The removal of these preservatives also allowed for fungal growth and reduced survival from 94 to 38%. Removing diet preservatives, that inhibited the growth of Chromobacterium sp. PRAA, increased the total mortality of the larvae as well as reducing the time needed to kill 50% of the larvae. Compared to incorporation of bacteria into molten diet, the total mortality of Colorado potato beetle fed either P. luminescens HM or Chromobacterium sp. PRAA on freeze-dried diet doubled. Preparation of freeze-dried diet need not be synchronized with the insect or the pathogen. The freeze-dried diet gave consistent results as measured by low control mortality and pathogen toxicity over time.

Evaluation of freeze-dried microalgal diets for the seed culture of Ruditapes decussatus using physiological and biochemical parameters

This study evaluates the nutritional value of several species of freeze-dried microalgae used to feed the seed of Ruditapes decussatus. These microalgae were: Isochrysis galbana, clone T-ISO; Tetraselmis suecica; and Phaeodactylum tricornutum. The addition of antibiotics, kaolin and fresh microalgae to the freeze-dried diet was also evaluated, and a study was made of the nutritional value of one species of microalga in each of the four stages of preparation of the freeze-dried diet: culture; concentration; freezing and freeze-drying. Both physiological and biochemical criteria were used to evaluate the different diets: availability; acceptability; digestibility; and biochemical composition. The highest seed growth rate were achieved with a diet of Isochrysis, followed by Tetraselmis, whilst the growth rates achieved with a dried diet of Phaeodactylum were much lower. The differences observed between diets of Isochrysis and Tetraselmis were due to a greater ingestion of the cells of Isochrysis. The minimal nutritional value of Phaeodactylum appears to be related to the low digestibility of its cell wall. The growth rates of seed fed on a diet of dried microalgae were significantly lower than those achieved with fresh diets (Albentosa et al., 1996b) for each of the species of microalgae that were tested, and this appears to be related to the lower digestibility of the microalgae after they have been freeze-dried. The addition of antibiotic or kaolin to the freeze-dried diet did not result in a major increase of seed growth rates. The substitution of a small proportion of freeze-dried microalgae with fresh microalgae produced a significant increase in seed growth rates, although these were still lower than those obtained with a completely fresh diet. The loss of nutritional value of microalgae when they are freeze-dried may be due to some kind of process which occurs during freeze-drying, altering the digestibility of the microalgae.

Food Preference and Patterns of Foraging Activity of the Southern Fire Ant (Hymenoptera: Formicidae)

We investigated foraging patterns of the southern fire ant, Solenopsis xyloni (McCook), using combinations of readily available foods that might be incorporated into a bait mixture. Choice tests conducted to determine the most attractive diet for S. xyloni included preference tests for each of 4 particle sizes. Freeze-dried diets were more attractive than oven-baked diets, and diets made with freeze-dried chicken eggs and anchovies were the most attractive. A particle size of diet of 11-20 mesh (840-2,000µn) resulted in the largest amount of diet removed by the colony. The smallest particle size, 40 mesh (420-590µm), had the most particles removed by workers but yielded the least amount of diet brought into the ant colony. S. xyloni is primarily a nocturnal forager, whose foraging begins ≈4 h before sunset and whose maximal foraging occurs between 2 and 7 h after sunset. There was considerable seasonal intracolony variation, but the maximal amount of diet was taken in June, August, and October.

Freeze-Dried Artificial Diet-Based Technique for Screening Plant Extracts Against Epiphyas Postvittana (Lepidoptera: Tortricidae)

A bioassay method based on freeze-dried artificial diet for assessing feeding and contact toxicity in light brown apple moth, Epiphyas Postvittana Walker, larvae is described. Diet disks were vacuum freeze-dried. Organic solvent extracts were added to the disk (120 μl), vacuum evaporated for 3 h, and reconstituted with distilled water before adding the neonate larvae(40 per replicate). This technique took 42 min per extract to set up and evaluate. Results for a range of foliage extracts of New Zealand gymnosperms are discussed. Ability to test the activity of extracts dissolved in volatile organic solvents was seen as a major advantage of this technique.

Characterization of a diet reference material for 17 elements.

A freeze-dried diet reference material was prepared from commonly consumed everyday foods. Concentrations of major (Mg, Ca, Na, K and P), minor (Mn, Zn, Fe, Cu, and Al), and trace elements (Cr, Ni, Co, Mo, As, Se, and Cd) in this diet material were determined by the authors and 10 collaborating laboratories using a total of 10 different analytical techniques. Good agreement between concentration values determined by the different laboratories enabled the authors to computer recommended values and uncertainties for these 17 elements. Values for proximates as well as several other nutrients were also reported by collaborators. This diet material is available to the scientific community as Reference Material 8431 through the National Bureau of Standard's Office of Standard Reference Materials.

Contribution of Streptococcus thermophilus to Growth-Stimulating Effect of Yogurt on Rats

The origin of the growth-stimulating factor in yogurt was studied in rats fed liquid or freeze-dried diets of milk, yogurt, milks fermented individually by Streptococcus thermophilus and Lactobacillus bulgaricus, and milks to which cells of Streptococcus thermophilus and Lactobacillus bulgaricus were added. Diets containing sonicated cells, cell supernatant, and cell fractions also were fed. Milk fermented by Streptococcus thermophilus and milk plus Streptococcus thermophilus cells stimulated growth as effectively as did yogurt. That finding and the absence of stimulation in rats fed Lactobacillus bulgaricus showed that Streptococcus thermophilus is responsible for stimulation of growth by yogurt. Growth was stimulated by an intracellular factor and not by fermentative changes in the milk.

Importance of dietary amines in meal-induced gastrin release

The dietary chemical constituents responsible for initiating the gastrin secretory response to a meal have yet to be identified. The evidence supporting the importance of dietary amino acids in the initiation of the postprandial release of gastrin is both conflicting and unconvincing. In this study we investigated the role of the amino acid breakdown products ammonia and the amines in the regulation of gastrin release both in vivo and in vitro. Lyophilization of standard rat food under alkaline conditions results in the volatilization of both ammonia and the amines, which can be subsequently condensed in a cold trap. The normal postprandial release of gastrin is significantly reduced by approximately 50% when rats are fed this freeze-dried diet. Addition of the amine-containing condensate back to the freeze-dried diet completely restores this response to normal. Analysis of the completely restores this response to normal. Analysis of the condensate by thin-layer chromatography revealed that it contained ammonia, methylamine, ethylamine, dimethylamine, and a fourth unidentified aliphatic amine. All of the above compounds significantly stimulated the release of gastrin from isolated G cells. Similarly, addition of ammonia and a synthetic amine mixture to the freeze-dried diet completely restored the postprandial release of gastrin to normal levels. In conclusion, our results suggest that dietary amines and ammonia may play a key role in initiating the gastrin secretory response to a meal.

Comparative food utilization of coffee bean weevil larvae on a new freeze-dried diet and green coffee beans

A meridic diet for culturing the coffee bean weevil, Araecerus fasciculatus was formulated and freeze-dried into pellets. When exposed to an atmosphere of 80 ± 5%r.h. the diet reached a moisture equilibrium that invoked oviposition and was satisfactory for growth and development of the insect. Larvae ingested larger amounts of the freeze-dried diet than of the natural food, green coffee beans, reaching equivalent weight and pupation in 31.8 ± 0.4 days on the diet as compared to 46.8 ± 0.8 days on the coffee beans. Approximate digestibilities of the two foods were not significantly different. However, the coffee beans were converted more efficiently to body mass than was the diet. Faeces of larvae on the diet contained more uric acid than those of larvae on coffee beans. Continuous culture and mass rearing of A. fasciculatus on the diet is possible.