Ileal and total tract nutrient digestibility in blue foxes (Alopex lagopus) fed extruded diets containing different protein sources

Comparing the standardized amino acid digestibility of an alternative protein source with commercially available protein-based ingredients using the precision-fed cecectomized rooster assay

Using single-cell-based proteins in pet foods is of interest, but little testing has been done. Therefore, our objective was to determine the amino acid (AA) digestibilities, assess protein quality of a novel microbial protein (MP) (FeedKind), and compare it with other protein-based ingredients using the precision-fed cecectomized rooster assay. Test ingredients included: MP, chicken meal (CM), corn gluten meal (CGM), pea protein (PP), and black soldier fly larvae. Thirty cecectomized roosters (n = 6/ingredient) were randomly assigned to test ingredients. After 24 h of feed withdrawal, roosters were tube-fed 15 g test ingredient and 15 g corn, and then excreta were collected for 48 h. Endogenous AA corrections were made using additional roosters. Digestible indispensable AA score (DIAAS)-like values were calculated to determine protein quality according to Association of American Feed Control Officials (AAFCO), The European Pet Food Industry Federation, and National Research Council reference values for growing and adult dogs and cats. Data were analyzed using the Mixed Models procedure of SAS 9.4, with P ≤ 0.05 being significant. All reactive lysine:total lysine ratios, an indicator of heat damage, were higher than 0.9, except for CM (0.86). Digestibility of indispensable and dispensable AA were >85% and >80% for MP, respectively, with indispensable AA digestibilities being >80% for all other ingredients. In general, CGM had the highest, while CM had the lowest AA digestibilities. Two exceptions were lysine and tryptophan. Lysine digestibility for MP was higher than that of all other ingredients, while tryptophan digestibility for MP was higher than that of CM, CGM, and PP. Threonine digestibility was highest for CGM and MP. Valine digestibility was highest for CGM, PP, and MP. DIAAS-like calculations identified limiting AA of each ingredient and depended on the reference used and life stage and species of animal. Using AAFCO guidelines, all DIAAS-like values for MP were >100 suggesting that it could be used as the sole source of protein in adult dog and cat diets; only methionine had DIAAS-like values <100 for growing kittens. For dogs, limiting AA was most commonly methionine, threonine, and tryptophan in the other protein sources. For cats, limiting AA was most commonly lysine and methionine. Lysine was severely limited in CGM across all life stages considered. Further research in dogs and cats is necessary, but our data suggest that the MP tested has high AA digestibilities and is a high-quality protein source that may be useful in pet foods.

Ileal and total tract digestibility and nitrogen utilisation in blue fox (Vulpes lagopus) fed low-protein diets supplemented with DL-methionine and L-histidine

To formulate low-protein diets for blue foxes with sufficient amounts of amino acids (AA), AA digestibility and AA requirements of the animals are crucial information. Therefore, a digestibility and nitrogen (N) balance trial was conducted with 20 blue foxes to determine the macronutrient and AA digestibility and N utilisation in low-protein diets supplemented with DL-methionine (Met) and L-histidine (His). In addition, plasma urea and plasma AA were measured. The diets were designated as P24 (control), P20, P20M, P16M and P16MH and contained energy from digestible crude protein (DCP) at 24%, 20% or 16% of total dietary metabolisable energy (ME). The 20% protein level was fed with or without Met and the 16% protein level was fed with Met and with or without His. The apparent total-tract digestibility (ATTD) of crude protein linearly decreased with decreasing dietary protein level. The ATTD of dry matter, organic matter and crude carbohydrates increased when wheat starch was added as a replacement for protein. The apparent ileal digestibility (AID) and ATTD methods were compared to determine the AA digestibility. The decreasing dietary protein supply decreased the ATTD of most of the AA: threonine, tryptophan (Trp), valine, alanine (Ala), aspartic acid (Asp), glutamic acid, glycine (Gly), proline (Pro), serine (Ser) and total AA. The AID of the AA was constant between diets. Diverging AA showed higher or lower digestibility when determined in the AID or ATTD methods. Isoleucine, lysine, Met, Ala and tyrosine showed higher levels of AID. Arginine, His, cysteine (Cys), Trp, Asp, Gly, Pro and Ser showed higher levels of ATTD, which may reflect the net loss of these AA in the large intestine. Met and His supplementation improved the ATTD and AID of the AA in question, respectively, but did not affect the other variables examined. N retention did not differ between diets and renal N excretion decreased with decreasing protein level; thus N utilisation improved. It was concluded that the protein supply and AA composition in low-protein diets with supplemented Met were adequate for adult blue foxes, since the lower protein supply improved N utilisation and did not affect N retention. However, His supplementation failed to reach the designed level and therefore showed no clear results.

Effects of dietary copper on elemental balance, plasma minerals and serum biochemical parameters of growing-furring male mink (Mustela vison)

The objectives of this study were to study the effects of different levels of dietary copper on copper and zinc balance, plasma minerals and serum biochemical parameters of mink in the growing-furring periods. One hundred and five standard dark male mink were randomly assigned to seven groups with the following dietary treatments: basal diet with no supplemental Cu (Control); basal diet supplemented with either 6, 12, 24, 48, 96, or 192 mg/kg Cu from copper sulfate, respectively. The average daily gain (ADG) linearly (P = 0.0026, P = 0.0006) responded to increasing levels of Cu; maximal growth was seen in the Cu24 group. Feed efficiency tended to improve with the increase of dietary copper level (linear P = 0.0010, quad, P = 0.0011). Fecal copper, urinary copper, retention copper responded in a linear (P < 0.05) fashion with increasing level of Cu. The effect of level of Cu was linear (P < 0.001) for plasma Cu concentration. The serum glutamic-oxalacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) activities were increased linearly (P < 0.05) with dose of Cu, but serum total protein (TP) and albumin (ALB) concentrations decreased linearly (P < 0.05) as dietary copper levels increased. Effect of level of Cu was linear (P < 0.001) for serum ceruloplasmin (CER) concentration or Cu-Zn superoxide dismutase (Cu-Zn SOD) activity. Supplemental dose of Cu linearly decreased serum triglyceride (TG) (P = 0.011) and total cholesterol (TC) (P = 0.007). Our results indicated that the activity of Cu-dependent enzymes was enhanced by increasing dietary Cu concentration and that supplementation of Cu in the diet of mink could alter the plasma lipid profile and copper concentration.

Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals

Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2).

Evaluation of methane-utilising bacteria products as feed ingredients for monogastric animals

Bacterial proteins represent a potential future nutrient source for monogastric animal production because they can be grown rapidly on substrates with minimum dependence on soil, water, and climate conditions. This review summarises the current knowledge on methane-utilising bacteria as feed ingredients for animals. We present results from earlier work and recent findings concerning bacterial protein, including the production process, chemical composition, effects on nutrient digestibility, metabolism, and growth performance in several monogastric species, including pigs, broiler chickens, mink (Mustela vison), fox (Alopex lagopus), Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and Atlantic halibut (Hippoglossus hippoglossus). It is concluded that bacterial meal (BM) derived from natural gas fermentation, utilising a bacteria culture containing mainly the methanotroph Methylococcus capsulatus (Bath), is a promising source of protein based on criteria such as amino acid composition, digestibility, and animal performance and health. Future research challenges include modified downstream processing to produce value-added products, and improved understanding of factors contributing to nutrient availability and animal performance.

Comparative apparent total tract digestibility of major nutrients and amino acids in dogs (Canis familiaris), blue foxes (Alopex lagopus) and mink (Mustela vison)

Major nutrient and amino acid digestibilities were evaluated in experiments with dogs (Canis familiaris), blue foxes (Alopex lagopus) and mink (Mustela vison) using seven extruded diets containing different protein sources. Four dogs (German shepherd), four blue foxes and four mink were offered each of the experimental diets to determine apparent total tract digestibility. Average digestibility of crude protein (CP) in blue foxes and mink was similar, and lower than the corresponding value in dogs (0·834 and 0·831 v. 0·864) (P< 0·001). CP digestibility in blue foxes showed significant correlations with dogs and mink (P< 0·05), while no significant correlation was observed between dogs and mink. Average digestibility of most amino acids was significantly lower in blue foxes than in dogs (P< 0·001), whereas mink digested most essential amino acids at the same level as did dogs. Most non-essential amino acids were digested at a significantly lower rate in the mink than in the dog and the blue fox (P< 0·001). There were significant correlations in the digestibility of most amino acids between dogs and blue foxes, and between blue foxes and mink (P< 0·05). Correlations were significant between dogs and mink for the digestibility of most essential amino acids (P< 0·05) but not significant (P> 0·05) for several non-essential amino acids. Average digestibility of crude fat was high and similar among the species studied: 0·968, 0·967 and 0·959 in dogs, blue foxes and mink, respectively. Average digestibility of starch ranged from 0·971 in mink to 0·998 in dogs; significantly higher in dogs than in blue foxes and mink, and significantly higher in blue foxes than in mink (P< 0·001). It was concluded that digestibility determined with mink, blue foxes or dogs may be used to predict digestibilities in the other investigated species. However, both the characteristics of the protein sources as well as the individual amino acid studied will influence the difference in digestibility among the species.

Growth Performance and Ileal and Total Tract Amino Acid Digestibility in Broiler Chickens Fed Diets Containing Bacterial Protein Produced on Natural Gas

A total of 180 broiler chickens were fed 1 of 3 diets from day-old to slaughter at 35 d: a control diet with 35% soybean meal (SOY) or diets in which either 6% basic bacterial protein meal (BBP) or 6% autolysed bacterial protein meal (AUT) partially replaced soybean meal protein. Ileal and total tract apparent amino acid digestibility were examined in 5 chickens per diet using TiO(2) as an inert marker. Chickens fed the diets with bacterial protein had higher weight gain and feed consumption than control chicks during the first 3 wk, but there were no differences in growth or feed intake during the last 2 wk or during the total experimental period. The birds fed the BBP diet showed more efficient feed conversion compared with chickens fed the SOY and AUT diets. Litter quality at 5 wk was poorer in pens where the chickens were fed the AUT diet compared with the other 2 treatments. There were no differences among diets in the dressing percentage. Ileal amino acid digestibility at 5 wk of age revealed only minor differences between diets. There was a tendency toward lower ileal digestibility (0.12 > P > 0.07) of Arg, Lys, Met, and Phe in the AUT diet compared with the SOY diet, whereas there were no differences between the SOY and BBP diets. Total tract amino acid digestibilities at 5 wk were similar or slightly lower than the ileal digestibilities within diets. Total tract amino acid digestibility at 2 wk was similar to the total tract amino acid digestibility at 5 wk. The diets containing bacterial protein showed lower total tract digestibility of most amino acids compared with the SOY diet. It was concluded that 6% of either basic or autolysed bacterial protein can replace soybean meal in diets for broiler chickens without impairing growth performance, and the basic bacterial protein seemed to be a slightly better substitute than the autolysed bacterial protein.