Identification and concentration of soy isoflavones in commercial cat foods

OBJECTIVE: To determine the absolute and relative soy isoflavone content in commercial cat foods. SAMPLE POPULATION: 14 dry, 6 semimoist, and 22 moist commercial cat foods. PROCEDURE: Soy isoflavone content of each food was determined by use of acid-methanol hydrolysis and high-pressure liquid chromatography with ultraviolet absorbance detection. Isoflavones were identified and quantified by reference to authentic standards. RESULTS: Genistein and daidzein were the major soy isoflavones identified in 24 of 42 foods, with concentrations ranging from 1 to 163 microg/g of food. Foods labeled as containing soybean solids (16/42) had isoflavone concentrations > 11 microg/g. More dry (13/14) and semimoist (6/6) foods contained isoflavones than moist foods (5/22). Isoflavone content and food cost were negatively correlated for dry and semimoist foods but not for moist foods. Total amount of isoflavone consumed by cats fed these soy-containing foods as a sole maintenance diet was estimated to be between 0.6 and 4.5 mg/kg of body weight/d, which is comparable to concentrations in humans that result in a measurable although modest effect on serum concentrations of steroid and thyroid hormones. CONCLUSIONS AND CLINICAL RELEVANCE: Genistein and daidzein are common constituents of commercial cat foods. Predictors of isoflavone content included ingredient labeling, food type, and food cost. Soy isoflavones in some commercial cat foods were detected in amounts predicted to have a biological effect.     

Detection of estrogenically active substances in diets for sows by an in vitro bioassay supported by HPLC analysis

There is considerable evidence that exogenous estrogenic compounds can have adverse effects on fertility. The main reason cited in literature for hyperestrogenism in pigs is contamination of feedstuffs by the mycotoxin zearalenone (Boehm, 2000), but further estrogenically active substances might also be involved in cases of impaired fertility with symptoms like enlarged, red-coloured vulvae in piglets, irregular estrus cycles and anestrus of sows (Bennetts et al., 1946; Drane et al., 1981). It is well known that soy used in diets for pigs as a main protein source contains phytoestrogens. Amongst them, isoflavones like genistein and daidzein are of particular interest. Aim of this study was to optimize and use an established bioassay (Kluczka, 2003) to determine estrogenic activity in feedstuffs for pigs related to isoflavones and further substances with estrogenic potential. This bioassay is a reporter gene assay based on stably transfected human embryonal kidney cells (HEK 293) that contains either alpha or beta estrogen receptor (alpha- or beta-HEK). The estrogenic activity measured in the luciferase assay was expressed in estradiol-equivalents (EEQ) and the results were compared with the isoflavone content (genistein, daidzein) obtained by chemical analysis using high performance liquid chromatography-Ultraviolet (HPLC-UV). Mean estrogenic activity in diets fed to sows in herds with altered fertility was 275.8 microg EEQ/kg feed in alpha-HEK cells and 295.0 microg EEQ/kg feed in beta-HEK cells. Feedstuffs from herds without any altered fertility showed an average estrogenic activity of 204.9 microg EEQ/kg feed in alpha-HEK and 213.3 microg EEQ/kg feed in beta-HEK. The estrogenic activity was strongly related to the concentration of the isoflavones (alpha-HEK, r(2)=0.9488; beta-HEK, r(2)=0.9427). Clinically relevant zearalenone concentrations (>50-150 microg/kg feed) displayed estrogenic effects in the bioassay that did not differ significantly from those caused by high isoflavone concentration because of the use of soy as protein source.     

Dietary isoflavone absorption, excretion, and metabolism in captive cheetahs (Acinonyx jubatus)

Dietary isoflavones, capable of influencing reproductive parameters in domestic cats (Felis catus), have been detected in commercial diets fed to captive cheetahs (Acinonyx jubatus). However, the absorptive and metabolic capacity of cheetahs towards isoflavones has not yet been studied. Experiments were designed to describe the plasma concentration-time curve, metabolite profile, and urinary and fecal excretion of genistein and daidzein in cheetahs following consumption of isoflavones. Four adult cheetahs were administered a single oral bolus of genistein and daidzein, and five juvenile cheetahs consuming a milk replacer formula found to contain isoflavones were also included. Urine was collected from all animals, and blood and feces were also collected from adult cheetahs following isoflavone exposure. Samples were analyzed for isoflavone metabolite concentration by liquid chromatography-electrospray ionization-multiple reaction ion monitoring mass spectrometry and high-performance liquid chromatography. Sulfate conjugates were the primary metabolites detected of both genistein and daidzein (60-80% of total isoflavones present) in the plasma and urine of cheetahs. A smaller proportion of daidzein was detected as conjugates in the urine of juvenile cheetahs, compared to adult cheetahs. Other metabolites included unconjugated genistein and daidzein, O-desmethylangolensin, and dihydrodaidzein, but not equol. Only 33% of the ingested genistein dose, and 9% of daidzein, was detected in plasma from adult cheetahs. However, of the ingested dose, 67% of genistein and 45% of daidzein were detected in the feces of adults. This study revealed that cheetahs appear efficient in their conjugation of absorbed dietary isoflavones and only a small fraction of ingested dose is absorbed. However, the capacity of the cheetah to conjugate genistein and daidzein with sulfate moieties appears lower than reported in the domestic cat. This may confer greater opportunity for biologic activity of isoflavones in the cheetah than would be predicted from findings in the domestic cat. However, further investigation is required.     

The isoflavone content of commercially-available feline diets in New Zealand

AIM: To identify and quantify concentrations of the isoflavones genistein, daidzein, biochanin A and formononetin in commercially- prepared feline diets sold in New Zealand. METHODS: Feline diets (n=138) were collected from supermarkets, pet stores and veterinary clinics in New Zealand. Diets were classified into five categories based on the following criteria: the presence/absence of soy, the presence/absence of non-soy plant material, and dry matter (DM) content. A high performance liquid chromatography (HPLC)-based assay was developed and validated to identify and quantify concentrations of the isoflavones genistein, daidzein, biochanin A and formononetin. RESULTS: Isoflavones were detected in all categories of diet, and at quantifiable concentrations in 104/138 (75%) of the diets tested. More dry diets (127/138; 92%) contained isoflavones at quantifiable concentrations than moist diets (83/138; 60%, p<0.001). Of the isoflavone-positive diets, moist diets that contained soy had the highest median isoflavone content (71.1 mg/kg DM and 0.018 mg/kcal metabolisable energy; ME) whilst moist meat-only diets had the lowest (3.24 mg/kg DM and 0.0004 mg/kcal ME). Isoflavone contents varied similarly between categories of diet whether evaluated on a DM or ME basis. High isoflavone contents were associated with diets containing soy and those of low cost. Biochanin A and formononetin were found at concentrations above the detection limit of the assay in 25/138 (18%) and 7/138 (5%) of the diets analysed, respectively. The estimated median daily isoflavone exposure for cats consuming feline diets sold in New Zealand ranged from 0.03 mg/kg bodyweight (BW) for moist meat-only diets to 1.47 mg/kg BW for moist diets containing soy, whilst the diet with the highest isoflavone content would provide daily exposure of 8.13 mg/kg BW. CONCLUSIONS: Isoflavones are present in commercially-prepared feline diets sold in New Zealand at concentrations that have elicited physiological responses in the reproductive, endocrine, and immune systems of other mammalian species. Since isoflavones appear to be a common constituent of feline diets, further investigation of the biological activities of these dietary compounds in cats is warranted.     

In sacco evaluation of ruminal degradability of isoflavones from full-fat soybean and extracted soybean meal—A pilot study

The aim of the study was to determine the ruminal degradability of dry matter (DM), daidzein, genistein, glycitein and total isoflavones in ground full-fat soybean (GFFS) and solvent-extracted soybean meal (SSBM) using the in sacco method. The experiment was carried out in three replications on ruminally cannulated sheep that were fed twice a day with a diet consisted of hay and supplemental mixture (6:4, DM basis). The nylon bags with 2 g feed samples ground to 2 mm were incubated in the rumen for 0, 2, 4, 8, 16 and 24 h. The effective degradability (ED) of DM, daidzein, genistein, glycitein and total isoflavones was calculated at outflow rate of 0.06 h. The ED of DM in GFFS was 77.8% and was higher than in SSBM being 71.8% (p < 0.001). The ED of daidzein (96.8%) and genistein (93.6%) was higher for SSBM compared with GFFS (93.9% and 92.8%, p < 0.001 and p = 0.003, respectively) while ED of glycitein was lower for SSBM than for GFFS (75.5 and 81.7%, respectively, p < 0.001). All isoflavones in the incubations were extensively degraded in the rumen, and regardless of dietary source, they were almost completely degraded after 16 h of incubation. Further, the disappearance patterns, that is the functions describing the time courses of the analyte disappearance, were assessed. The disappearance patterns of daidzein, genistein, glycitein and total isoflavones were similar and showed greater disappearance of mentioned isoflavones from SSBM compared to GFFS (p < 0.001 for daidzein, genistein and total isoflavones and p = 0.002 for glycitein). The study provides knowledge on the effect of processing on degradability of isoflavones in rumen that can be used to clarify the interrelationship between isoflavones and rumen microbiota.     

The effect of ingredients in dry dog foods on the risk of gastric dilatation-volvulus in dogs

Using dry dog food label information, the hypothesis was tested that the risk of gastric dilatation-volvulus (GDV) increases with an increasing number of soy and cereal ingredients and a decreasing number of animal-protein ingredients among the first four ingredients. A nested case-control study was conducted with 85 GDV cases and 194 controls consuming a single brand and variety of dry food. Neither an increasing number of animal-protein ingredients (P=0.79) nor an increasing number of soy and cereal ingredients (P=0.83) among the first four ingredients significantly influenced GDV risk. An unexpected finding was that dry foods containing an oil or fat ingredient (e.g., sunflower oil, animal fat) among the first four ingredients were associated with a significant (P=0.01), 2.4-fold increased risk of GDV. These findings suggest that the feeding of dry dog foods that list oils or fats among the first four label ingredients predispose a high-risk dog to GDV.     

高效液相色谱法测定饲料中大豆异黄酮

为了建立检测天然植物饲料添加剂中大豆异黄酮类主要成分含量的快速分析方法,采用HPLC法,分别以大豆中的大豆甙、染料木甙、大豆素、染料木素为标准品,在其紫外最大吸收峰260nm处,测定样品分离提取的样液,从而得出大豆异黄酮类各主要单体的含量。     

Phytoestrogens alter cortisol and androstenedione secretion by porcine adrenocortical cells

The effect of plant-derived, nonsteroidal estrogens (genistein, daidzein and biochanin A) on cortisol and androstenedione secretion by porcine adrenocortical cells was examined. Adrenals were harvested from locally slaughtered mature gilts on days 5-9 of the oestrous cycle. Adrenocortical cells were incubated with or without genistein, daidzein, biochanin A (0.5, 5, 10 or 50 microM), oestradiol (10, 50, 100 or 500 pg/mL) and ACTH (5 nM--positive control). All incubations were performed for 8 h (95% air and 5% CO2, 37 degrees C). ACTH increased cortisol and androstenedione secretion. Genistein, daidzein and biochanin A suppressed cortisol output, whereas androstenedione secretion was enhanced by these phytoestrogens. In contrast, oestradiol did not alter steroid secretion by porcine adrenocortical cells, which may suggest that phytoestrogens have a non-oestrogenic mechanism of action. Therefore, phytoestrogens present in commercial forage may influence adrenocortical function in pigs by decreasing cortisol and increasing androstenedione secretion.     

Soybean: feed quality and safety. Part 1: biologically active components. A review

A large number of soybean components have diverse biological activities. These include hormonal, immunological, bacteriological and digestive effects. The presently known allergens are listed. The divergence between chemical evaluation and biological value is highlighted. The following components are discussed: Kunitz inhibitor, Bowman-Birk inhibitor, saponins, soyacystatin, phytoestrogens (daidzein, glycitein, genistein), Maillard products, soybean hydrophobic protein, soy allergens, lecithin allergens, raffinose, stachyose, 2-pentyl pyridine. The studies describing the effects of the isolated components are reviewed.     

The Effects of Isoflavones on Androgens and Glucocorticoids During Puberty on Male Wistar Rats

Isoflavones are the most common phytoestrogens found in human diets. However, it is still not clear whether isoflavones have effects on the reproductive and the endocrine systems under normal dietary intake and overdose. The aim of this study was to determine how the most important isoflavones, genistein and daidzein, affect androgen and glucorticoid levels on male prepuberal rats. A hundred and seventy‐five 30‐day‐old male Wistar rats were dosed orally by stomach tube every day for 35 days, with saline solution, low and high doses of genistein, daidzein and a mixture of both. Serum samples were analysed by an enzyme immunoassay for hormone determinations. In control group, there was a peak of testosterone (T) and dihydrotestosterone levels associated to the onset of puberty, at the third week. However, in low‐dose groups, the same peak was found at the fourth week (p < 0.05), indicating a delay in the onset of puberty in these groups. Moreover, high doses groups serum androgen levels were significantly lower (p < 0.05) than the control group from the first week until fifth week. This fact was supported by a epididymal histological analysis that indicate in low doses there were several content of spermatozoa at fourth week and in high doses there were few content of spermatozoa. Besides, corticosterone levels followed the same pattern of androgens in all groups. We can conclude that oral administration of isoflavones in male rats decreased the secretion of androgens and glucocorticoids causing a delay in the onset of puberty and may cause physiological and developmental problems.     

Diet type affects viscosity of ileal digesta of dogs and simulated gastric and small intestinal digesta

Two experiments were conducted to determine effects of diet type on viscosity of ileal digesta of dogs and simulated gastric and small intestinal digesta. In experiment 1, three canned and three dry dog foods were surveyed for effects on ileal digesta viscosity. Experiment 2 evaluated the same six diets for effects on simulated gastric and small intestinal digesta. Canned diets and dry diets contained an average 22.7% and 89.9% dry matter (DM) respectively. Concentrations of total dietary fibre (TDF) in the diets ranged from 1.8% to 26.5%. Ileal digesta viscosities ranged from 1326 to 46,641 and 7748 to 10,208 cP for canned and dry treatments respectively. Ileal DM concentrations ranged from 8.2% to 16.2% and 15.4% to 15.8% for canned and dry treatments respectively. Dry matter intake ranged from 224 to 290 and 295 to 325 g/day for canned and dry treatments respectively. During gastric digestion simulation, viscosity peaked at 2 and 4 h for all three canned diets and dry diets respectively. During small intestinal digestion simulation, viscosity peaked between 6 and 12 h for most diets except one canned diet and one dry diet, which contained high concentrations of TDF (25.1% and 26.5% respectively). Viscosity of these solutions peaked between 12 and 18 h. Viscosity of ileal digesta and simulated gastric and small intestinal digesta was the lowest after consumption of canned diets with the exception of the canned diet containing very high concentrations of dietary fibre (25.1% TDF). Ileal digesta viscosity of dogs appears to be responsive to the diet type characteristics.     

大豆异黄酮在畜禽生产中的应用及安全性研究进展

大豆异黄酮是来源于豆科植物且具有微弱的雌激素样作用的多酚类混合物,主要活性成分为染料木素、大豆黄酮和黄豆黄素。因其具有提高畜禽生产性能、免疫机能、抗氧化、促进骨代谢等生理作用,越来越多地应用在畜牧生产中。但近年来也出现了一些关于大豆异黄酮安全性和副作用的报道,因此,如何科学有效地利用需要进一步深入研究。文章综述了大豆异黄酮的种类、养分代谢特点、生理特性、对畜禽生产中的促进作用及对动物和人类存在的安全性问题。     

Research Progress on Application and Safety of Soybean Isoflavone in Animal Husbandry

Soybean isoflavone is a kind of faint estrogen-like mixture of polyphenols which derived from the leguminous plants.Its active components include genistein,daidzein and glycitein.It is used in animal husbandry for its physiological functions that it can enhances performance,immune function,antioxidant and improves bone metabolism.But some following reports about safety and side effects of soybean isoflavones are also appeared.That is a worthy further research topic how to use it effectively.The article summarizes the types of soybean isoflavones,nutrient metabolism characteristics,physiological characteristics,the promoting effect of livestock and poultry production and security problems about animal and human.     

ELISA testing for common food antigens in four dry dog foods used in dietary elimination trials

This study evaluated four over the counter venison dry dog foods available from one on-line retail vendor for potential contamination with common known food allergens: soy, poultry or beef. An amplified, double sandwich type enzyme linked immunosorbent assay (ELISA) test of soy, poultry and beef proteins were performed by an independent accredited food laboratory. The ELISA test for poultry protein was found to be unreliable when testing in dry dog foods because false negatives occurred. ELISA testing of control diets for both soy and beef proteins performed as expected and could be useful in antigen testing in dry dog foods. Three of the four over the counter (OTC) venison canine dry foods with no soy products named in the ingredient list were ELISA positive for soy; additionally one OTC diet tested positive for beef protein with no beef products listed as an ingredient list. One OTC venison diet was not found to be positive for soy, poultry or beef proteins. However, none of the four OTC venison diets could be considered suitable for a diagnostic elimination trial as they all contained common pet food proteins, some of which were readily identifiable on the label and some that were only detected by ELISA. Therefore, if the four OTC venison products selected in this study are representative of OTC products in general, then the use of OTC venison dry dog foods should not be used during elimination trials in suspected food allergy patients.     

Determining metabolizable energy content in commercial pet foods

This study was conducted to assess the suitability of several equations for the estimation of metabolizable energy (ME) of pet foods. Sixteen canned and 31 dry cat foods and 24 dry dog foods representing the range of energy densities found in commercial adult, growth or all life stage products were evaluated in four separate experiments. In vivo ME was compared with estimates of ME generated by several previously published equations. The results indicated that the equation recommended by Association of American Feed Control Officials provided reasonable estimates of in vivo ME for both canned cat foods and dry dog foods, but proved unsuitable for dry cat foods. Better estimates were generated in each case using other published equations. Of the equations tested, the most accurate equations for estimating ME (kJ/g) without feeding trials were:
for canned cat foods: [(16.32 × protein) + (32.22 × fat) + (12.55 × NFE)];
for dry cat foods: [((GE × 1.209) – 1.911) × 4.184] or [((0.075 × g fat) + 2.766) × 4.184]
for dry dog foods: [GE=(24 × g protein) + (38 × g fat) + (17 × g NFE), then percentage energy digestibility=91.2 – (1.43 × percentage crude fibre in dry matter), then ME=(GE × percentage energy digestibility) – (4.34 × g protein)].
With the exception of high-fibre weight-management diets, the simple equation [((GE × 1.209)–1.911) × 4.184] also reliably predicted ME in dry dog foods.     

The effect of crude fibre on apparent digestibility and digestible energy content of extruded dog foods

The apparent digestibility of nutrients and energy of 38 commercial dry extruded dog foods was measured using six adult (2 to 3 year-old) female Beagles. Diets contained [in g/kg dry matter (DM)]: 164–360 crude protein (CP); 79–261 ether extracts (EE); 8–33 crude fibre (CF) and 318–585 nitrogen free extracts (NFE). Apparent energy digestibility ranged from 77.3 to 91.6%, and was closely related to CF content ( r =–0.85), yielding the resultant equation: GED (%)=94.00 – 4.04 × CF (% DM). The estimation of digestible energy content of foods from digestibility coefficients predicted from the above equation and gross energy measured or estimated from the Weende fractions, provides a more accurate prediction of experimental values than the Atwater approach followed by the National Research Council and the Association of American Feed Control Officials.     

Vitamin A concentrations in commercial foods for dogs and cats

The vitamin A concentration was determined in 89 Australian brands of commercial foods for dogs and cats. It was found that 8% of the dog foods and 14% of the cat foods had concentrations of vitamin A below the minimum recommended 1.1 mg/kg dry matter (dm) for dogs and 1.8 mg/kg dm for pregnant or lactating cats. Canned and fish-labelled cat foods were the only varieties with less than the minimum recommended concentration of Vitamin A, of which 71% were the same brand. The minimum recommended concentration of vitamin A was exceeded in all canned dog food tested. Concentrations of vitamin A in dry (ca. 6% moisture) dog and cat foods and semi-moist dog foods (ca. 23% moisture) never exceeded 10 mg vitamin A/kg dm. In contrast, canned pet foods stated to contain liver or kidney showed vitamin A concentrations from 13 to 284 mg/kg dm.     

Raw mechanically separated chicken meat and salmon protein hydrolysate as protein sources in extruded dog food: effect on protein and amino acid digestibility

Protein quality was evaluated for mechanically separated chicken meat (MSC) and salmon protein hydrolysate (SPH), and for extruded dog foods where MSC or SPH partially replaced poultry meal (PM). Apparent total tract digestibility (ATTD) of crude protein (CP) and amino acids (AA) in the protein ingredients and extruded foods was determined with mink (Neovison vison). The extruded dog foods included a control diet with protein from PM and grain, and two diets where MSC or SPH provided 25% of the dietary CP. Nutrient composition of the protein ingredients varied, dry matter (DM) was 944.0, 358.0 and 597.4 g/kg, CP was 670.7, 421.2 and 868.9 g/kg DM, crude fat was 141.4, 547.8 and 18.5 g/kg DM and ash was 126.4, 32.1 and 107.0 g/kg DM for PM, MSC and SPH respectively. The content of essential AA (g/100 g CP) was more than 10.0 percentage units lower in SPH than in PM and MSC. The ATTD of CP differed (p < 0.001) between protein ingredients and was 80.9%, 88.2% and 91.3% for PM, MSC and SPH respectively. The ATTD of total AA was lowest (p < 0.001) for PM, and similar (p > 0.05) for MSC and SPH. In the extruded diets, the expected higher ATTD of CP and AA from replacement of PM with MSC or SPH was not observed. The ATTD of CP was determined to be 80.3%, 81.3% and 79.0% for the PM, MSC and SPH extruded foods respectively. Furthermore, the ATTD of several AA was numerically highest for the PM diet. Possibly, extrusion affected ATTD of the diets differently due to different properties and previous processing of the three protein ingredients.     

大豆异黄酮在雏鸡机体中吸收、转运及沉积的观察

9日龄雏鸡128只按初重随机分为4组:饲喂基础日粮对照组(C组)、基础日粮 3 mg/kg大豆黄酮组(3Da组)、基础日粮 6mg/kg大豆黄酮组(6Da组)和基础日粮 染料木素组(Ge组),试验期持续2周。与对照组相比,3Da组、6Da组和Ge组的日增重有增加趋势,料重比有所下降;空肠食糜、肝脏和肌肉中6Da组大豆黄酮含量分别增加288.15%(P<0.01),81.48%(P<0.05),155.97%(P<0.01);Ge组分别增加415.64%,172.48%,164.18%。食糜、肝脏中染料木素含量,6Da组分别增加154.16%和150.51%;Ge组分别增加238.13%和148.48%。肌肉内未检测出染料木素。上述结果提示,大豆黄酮和染料木素在雏鸡体内吸收、转运,并在肝脏和肌肉内代谢。两者可相互转化,仅大豆黄酮在肌肉内沉积。     

Milk secretion of nitrofurantoin,as a specific BCRP/ABCG2 substrate,in assaf sheep: modulation by isoflavones1

Studies on residues in milk used for human consumption have increased due to health concerns and priority interest in the control of potentially risky drugs. The protein BCRP/ABCG2, present in the mammary epithelia, actively extrudes drugs into milk and can be modulated by isoflavones. Nitrofurantoin is a specific BCRP substrate which is actively excreted into milk by this transporter. In this research, we studied nitrofurantoin transport into milk in four experimental groups: G1‐calves fed forage with isoflavones; G2‐calves fed forage with isoflavones and administered exogenous genistein and daidzein; G3‐calves fed forage without isoflavones; G4‐calves fed forage without isoflavones and administered exogenous genistein and daidzein. Results show increased levels of nitrofurantoin in milk from calves without isoflavones (G3) and decreased nitrofurantoin residues in milk when isoflavones were present, either by forage (G1 and G2) or by exogenous administration (G4). The values of C_max in milk were significantly lower in those groups with isoflavones in forage (G1, G2). Plasma levels were low and unmodified among the groups. Inter‐individual variation was high. All these results seem to point to a feasible control of drug secretion into milk through isoflavones in the diet when the drug is a good BCRP/ABCG2 substrate.