Identification and concentration of soy phytoestrogens in commercial dog foods

OBJECTIVE: To identify and determine the concentrations of phytoestrogens in commercial dog foods. SAMPLE POPULATION: 24 commercial dog foods, including 12 moist or dry extruded commercial dog foods that contained soybeans or soybean fractions and 12 foods without any soybean-related ingredients listed on the label. PROCEDURE: Foods were analyzed for phytoestrogen content, including 4 isoflavones (genistein, glycitein, daidzein, and biochanin A), 1 coumestan (coumestrol), and 2 lignans (secoisolariciresinol and matairesinol) by use of acid-methanol hydrolysis and high-pressure liquid chromatography with UV-absorbance detection. Phytoestrogens were identified and quantified by reference to authentic standards. RESULTS: Isoflavones, coumestans, and lignans were undetectable in diets that did not list soybean-related ingredients on the label. Only 1 of the 12 diets that included soybean or soybean fractions had undetectable concentrations of phytoestrogens and that product contained soy fiber. The major phytoestrogens were the isoflavones daidzein (24 to 615 microg/g of dry matter) and genistein (4 to 238 microg/g of dry matter). CONCLUSIONS AND CLINICAL RELEVANCE: Soybean and soybean fractions are commonly used ingredients in commercial dog foods. Dietary intake of phytoestrogens may have both beneficial and deleterious health effects. Our results indicated that certain commercial dog foods contain phytoestrogens in amounts that could have biological effects when ingested long-term.     

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.     

大豆异黄酮的特性及其应用研究进展

大豆异黄酮属异黄酮类植物雌激素,主要存在于豆科植物中,其主要成分为染料木素、大豆苷元和大豆黄素,具有类雌激素和抗雌激素活性的双重作用,且具有抗氧化、调节机体免疫系统及内分泌系统等多种生物学功能,在畜牧业中有着极其广泛的用途,其应用前景非常广阔,是目前国内外研究的热点.文章综述了黄酮类和异黄酮类化合物的结构、大豆异黄酮的...     

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.     

Concentrations of isoflavones and their metabolites in the blood of pregnant and non-pregnant heifers fed soy bean

The present study compared the changes in isoflavones (daidzein and genistein) and their metabolite (equol and para-ethyl-phenol) concentrations in the blood plasma of cyclic and pregnant heifers after feeding with soy bean. Twelve healthy heifers were divided into three groups: cyclic heifers (days 8-12 of the estrous cycle; control group; n=4), an early pregnancy group (2 months pregnant; n=4) and a late pregnancy group (8 months pregnant; n=4). All heifers were fed a single dose of 2.5 kg of soy bean and then blood samples were taken from the jugular vein for 8 h at predetermined intervals. The concentrations of soy bean-derived isoflavones and their active metabolites were measured in the blood plasma on an HPLC system. In the blood plasma of the early- and late-pregnant heifers, we found lower concentrations and time-dependent decreases in daidzein and genistein in comparison to cyclic heifers (P<0.05). Moreover, we noticed significant increases of equol and para-ethyl-phenol in the blood plasma of the early-pregnant heifers (P<0.05). In contrast, in the blood plasma of the late-pregnant heifers, we did not find an increase in the isoflavone metabolite concentrations compared with the early-pregnant heifers (P>0.05). In conclusion, physiological status (cyclicity or pregnancy) of the females influenced the concentrations of isoflavone metabolites in the blood plasma of the heifers. The stage of pregnancy affects isoflavone absorption, biotransformation and metabolism differently and results in higher concentrations of active metabolites of isoflavones during early pregnancy in comparison to their lower concentrations during late pregnancy. Therefore, we surmise that cows are more sensitive to active isoflavone metabolite actions during early pregnancy than cyclic heifers and heifers in late pregnancy.     

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 effect of soy isoflavones on egg quality and bone mineralisation during the late laying period of quail

1. Soy isoflavones play a role in calcium and bone metabolism. Poor egg quality, skeletal abnormalities and architectural deterioration of bone tissue are common problems under hot climate conditions and with increased age in poultry. 2. In this study, we investigated the effects of soy isoflavone supplementation on egg production, egg quality, bone mineral density (BMD), levels of osteocalcin (OC), vitamin D, calcium (Ca), phosphorus (P) and alkaline phosphatase (ALP) activity in quail (Coturnix coturnix japonica) during the late laying period. 3. The birds (n = 180; 28 weeks old) were randomly assigned to 6 treatment groups consisting of 6 replicates of 5 birds each in a 2 x 3 factorial arrangement of treatments (temperatures, soy isoflavone concentration). Birds were kept in wire cages in a temperature-controlled room at either 22 degrees C (thermo-neutral, TN) or 34 degrees C (heat stress, HS) for 8 h/d (09:00 to 17:00 h; until the end of the study) and fed either on a basal (control) diet or on the basal diet supplemented with either 400 or 800 mg of soy isoflavones/kg of diet. 4. Heat exposure reduced feed intake, egg production, egg quality, BMD, OC, vitamin D, Ca, P and ALP when the basal diet was given. Feed intake, egg production and egg weight were not affected, while eggshell thickness and eggshell weight increased in soy isoflavone-supplemented quails reared under TN conditions. However, feed intake, egg production, egg weight, eggshell thickness, eggshell weight and Haugh units were positively influenced by soy isoflavone supplementation in HS groups for quail during the late laying period. Bone mineral density, serum OC, vitamin D, Ca, P levels and ALP activity were significantly improved by soy isoflavone supplementation in both the TN and HS groups in quail during the late laying period. 5. Soy isoflavone supplementation of basal diet significantly improved egg quality and bone mineralisation in quail during the late laying period.     

Effect of dietary soy on serum thyroid hormone concentrations in healthy adult cats

OBJECTIVE: To compare effects of short-term administration of a soy diet with those of a soy-free diet on serum thyroid hormone concentrations in healthy adult cats. ANIMALS: 18 healthy adult cats. PROCEDURE: Cats were randomly assigned to receive either a soy or soy-free diet for 3 months each in a crossover design. Assays included CBC, serum biochemical profile, thyroid hormone analysis, and measurement of urinary isoflavone concentrations. RESULTS: Genistein, a major soy isoflavone, was identified in the urine of 10 of 18 cats prior to dietary intervention. Compared with the soy-free diet, cats that received the soy diet had significantly higher total thyroxine (T4) and free T4 (fT4) concentrations, but unchanged total triiodothyronine (T3) concentrations. The T3/fT4 ratio was also significantly lower in cats that received the soy diet. Although the magnitudes of the increases were small (8% for T4 and 14% for fT4), these changes resulted in an increased proportion of cats (from 1/18 to 4/18) that had fT4 values greater than the upper limit of the laboratory reference range. There was no significant effect of diet on any other measured parameter. CONCLUSIONS AND CLINICAL RELEVANCE: Short-term administration of dietary soy has a measurable although modest effect on thyroid hormone homeostasis in cats. Increase in T4 concentration relative to T3 concentration may result from inhibition of 5'-iodothyronine deiodinase or enhanced T3 clearance. Soy is a common dietary component that increases serum T4 concentration in cats.     

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.     

Effects of early experience on food acceptance in a colony of adult research cats: A preliminary study

Acceptance of feline commercial canned and raw-type moist foods was evaluated in 18 adult cats with and without dietary pre-exposure to the same moist foods in the postweaning period. We hypothesized that cats pre-exposed to moist foods would readily accept canned or raw foods on re-exposure as adults, despite consuming a commercial expanded dry food for a period of 7-23 months. A total of 13 cats were fed 1 of 3 moist foods (commercial canned, commercial raw, or homemade raw foods) exclusively between 9 and 20 weeks of age (exposed), and 5 adult cats were offered only dry food during the postweaning period (unexposed). All 18 cats were offered 1 of 3 moist foods as adults. The relative risk, confidence intervals, and P values were determined for weight maintenance and food intake between the exposed and nonexposed cats when they were fed moist foods as adults. Moist food acceptance was generally poor when offered to adult cats accustomed to eating an expanded dry diet for >7 months. There was no difference (P = 0.61) in weight maintenance between those cats fed a moist food or expanded dry food as kittens and the later acceptance of a commercial canned or raw-type moist food as an adult. Similarly, adequacy of food intake measured as a proportion of estimated resting energy expenditure was not different between groups. The shorter the duration of dry food feeding, the greater was the likelihood of weight maintenance on reintroduction of moist foods. Kittens fed canned foods showed greater adaptability and acceptance of both raw and canned foods than those pre-exposed to either of the raw foods.In conclusion, prefeeding kittens a raw or canned food during the postweaning period between 9 and 20 weeks of age, followed by a period of dry foods for >7 months, did not increase later acceptance of the foods as an adult as compared with feeding expanded dry foods alone. Further studies with larger numbers of cats are needed to verify these observations and determine statistical significance.     

Stability of creatine monohydrate and guanidinoacetic acid during manufacture (retorting and extrusion) and storage of dog foods

The stability of creatine monohydrate (CrMH), crystallised guanidinoacetic acid (GAA‐C) and granulated GAA (GAA‐G) in a moist retorted and a dry extruded dog food formulation during production and storage was investigated. Commercial food mixtures were supplemented with CrMH, GAA‐C or GAA‐G. Uniformity after mixing and retorting or extrusion was determined based on replicate samples (moist n = 8, dry n = 10). Storage stability was evaluated at 25°C/60% relative humidity for 15 months and 40°C/75% for 6 months. Foods with CrMH were analysed for creatine (Cr) and creatinine (Crn), whereas GAA‐C and GAA‐G foods were analysed for GAA concentrations. Coefficients of variation (CV) for uniformity of the additives after mixing of moist and dry pet food formulations were below 15%, and the CV was lower in processed mixtures. Recoveries after retorting and extrusion were higher for GAA‐G (79 and 99%) and GAA‐C (89 and 86%) compared to CrMH (36 and 85%) foods. In moist CrMH food, Cr concentrations re‐increased by 54% whilst Crn concentrations decreased by 39% after storage at 25°C for 15 months. With total molar Cr + Crn remaining stable throughout storage, Crn and Cr appeared to effectively interconvert. Storage of the extruded CrMH food at 25°C for 15 months resulted in a 63% decrease in Cr and a 39% increase in Crn concentration. The decrease in Cr concentration was larger at 6 months storage at 40°C compared to 15 months storage at 25°C. Both GAA‐C and GAA‐G moist and dry foods were stable during storage (<10% decrease). This study showed that GAA is highly stable during production and storage of moist and dry canine foods whilst CrMH is relatively unstable, particularly during storage. The latter makes it difficult to establish a guaranteed Cr content in finished moist retorted and dry extruded foods with CrMH.     

Effects of replacing fish meal with soy protein concentrate and of DL-methionine supplementation in high-energy, extruded diets on the growth and nutrient utilization of rainbow trout, Oncorhynchus mykiss

Our objectives were to test the potential replacement of fish meal by soy protein concentrate (SPC) in high-energy, extruded diets fed to rainbow trout (Oncorhynchus mykiss) and to evaluate the efficiency of DL-methionine supplementation of soy-based diets. Groups of trout (initial BW 103 to 106 g) were fed to visual satiety with isonitrogenous (6.6% DM) high-energy (22.8 MJ/kg DM gross energy), extruded diets, in which fish meal was progressively replaced with SPC (0, 50, 75, and 100%). Three 100% SPC diets were formulated to be either unsupplemented or supplemented with DL-methionine, so that total methionine content was .8 or 1.0% of DM. The quality of the SPC source used was assessed by measuring the antitryptic and antigenic activities and the concentrations of the isoflavones daidzein and genistein. Apparent digestibility of the diets was determined using the indirect method. A growth trial was conducted over 90 d at a water temperature of 18 degrees C. In addition to body composition analysis, plasma amino acid concentrations, anti-soy protein antibodies in the serum, and isoflavone concentrations in the bile were measured. The SPC source tested exhibited low antitryptic and antigenic activities, but it contained high concentrations of isoflavones (1,990 and 5,903 ppm for daidzein and genistein, respectively). Protein digestibility was high (92%) and was unaffected either the proportion of SPC in the diet or by DL-methionine supplementation. This was also true for the availability of amino acids, except phenylalanine. Digestibility of lipid and energy was reduced by 19% when SPC totally replaced fish meal. Growth rate was reduced when more than 50% of the dietary protein was of soy origin (daily growth coefficient of 3.2 and 2.1% for the control and the unsupplemented 100% SPC diet, respectively). The effect on growth was mainly explained by a general decline in feed intake (13.7 and 12.0 g DM x kg BW(-1) x d(-1) for the control and the unsupplemented 100% SPC diet, respectively) and in lipid and, thus, in energy digestibility. The DL-methionine supplementation partially reversed the depressive effects of high dietary SPC incorporation (+13% growth), mainly by enhancing intake. The negative effect of SPC incorporation either may be due to the high isoflavone concentration or to an interaction between the soy protein component and the dietary lipids.     

Exposure of growing and adult captive cheetahs (Acinonyx jubatus) to dietary isoflavones: twenty years later

Dietary isoflavones are associated with oestrogenic and anti‐oestrogenic effects, and have been linked to infertility in cheetahs. This study aimed to determine the isoflavone content of commercially prepared diets consumed by captive cheetahs. Sixteen international zoological facilities provided diets, and the isoflavone content of each diet was determined by acid hydrolysis and HPLC quantification. Proximate nutritional composition was also determined. Over half the diets analysed contained detectable concentrations of isoflavones, whereby total isoflavone content ranged from 1.75–183 mg/kg dry matter. The zoo‐specific diets were calculated to deliver a median isoflavone dose of 0.07 mg/kg body weight (BW) and a maximum of 1.95 mg/kg BW to captive cheetahs. On a metabolic body weight basis this equates to a maximum of 4.90–5.43 mg/kg^0.75. Some diets prepared for hand‐rearing neonatal cheetahs could expose neonates to doses of up to 4.24 mg/kg BW (or 4.24–6.33 mg/kg^0.75 for cubs under 3 months of age). Only one of six zoo‐specific diets was found to deliver isoflavones in doses shown to possess biological activity in other species. Therefore, on average, dietary isoflavones were not found in commercially prepared diets consumed by captive cheetahs in concentrations predicted to cause physiological changes. However, a small proportion of these diets, including hand‐rearing formulas, contained elevated isoflavones concentrations which may influence cheetah fertility, behaviour or other physiological parameters.     

Total selenium concentrations in canine and feline foods commercially available in New Zealand

AIMS: To determine the total selenium concentrations in petfoods commercially available in New Zealand and to establish whether these meet the current minimum recommended requirements of selenium in foods for cats and dogs. METHODS: Samples (n=89) from petfoods commercially available in New Zealand were analysed for total selenium concentration using a fluorometric method. Data, expressed on a dry matter (DM) basis, were analysed according to petfood type (dog or cat, and wet or dry), predominant flavour (chicken, seafood, chicken and seafood, beef, meat mix, other), manufacturer and country of manufacture. RESULTS: Fifty percent of petfoods purchased for this study were manufactured in Australia, and the remainder were produced in the United States of America (USA), New Zealand or Thailand. Mean total selenium concentrations were similar (0.61-0.80 mg/kg DM) in petfoods produced in Australia, New Zealand and the USA, but higher (mean 3.77 mg/kg DM; p<0.05) in petfoods produced in Thailand. Petfoods produced in Australia, New Zealand and the USA contained a variety of predominant flavours, whereas petfoods from Thailand contained only seafood flavour. Seafood-based flavours had the highest selenium concentrations in both cat and dog foods. Wet and dry dog foods had similar concentrations of selenium to dry cat foods, but wet cat foods had higher and more variable concentrations of selenium than these others (p<0.05). The mean selenium concentrations in cat and dog foods were 1.14 and 0.40 mg/kg DM, respectively, and there were no significant differences between manufacturers. CONCLUSIONS: Selenium concentrations in commercial petfoods sold in New Zealand appeared to meet recommended dietary requirements, although the range of concentrations was highly variable. Whether these recommendations are adequate for the maintenance of optimal health in cats and dogs has yet to be determined. CLINICAL RELEVANCE: Overt selenium deficiency disorders are unlikely in dogs and cats in New Zealand fed commercial petfoods unless the bioavailability of selenium in particular petfoods is low.     

Effect of diet on markers of intestinal health in dogs

The effects of two popular commercial pet foods on faecal markers of microbial metabolism were investigated. Adult dogs were fed a dry, extruded diet and a moist, canned diet in a randomly assigned crossover design. Fresh faecal samples were collected for chemical and enzyme activity assays. Relative to the canned diet, the dry food resulted in decreased faecal pH and faecal indole, sulphide and ammonia concentrations and increased total short-chain fatty acid, acetic and propionic acid concentrations. Faecal beta-glucosidase, beta-glucuronidase, beta-galactosidase and nitroreductase activities were decreased in dogs fed the dry diet. These changes in microbial metabolic activity are consistent with beneficial effects of the dry diet on colonic health.     

Effects of dietary soy isoflavones on growth, carcass traits, and meat quality in growing-finishing pigs

Two experiments were conducted to determine the effect of soy isoflavones on growth, meat quality, and carcass traits of growing-finishing pigs. In Exp. 1, 36 barrows (initial and final BW, 26 and 113 kg, respectively) were used and each treatment was replicated four times with three pigs each. The dietary treatments were 1) corn-soybean meal (C-SBM), 2) corn-soy protein concentrate (low isoflavones, C-SPC), or 3) C-SPC + isoflavones (isoflavone levels equal to those in C-SBM). Daily gain and ADFI were increased (P < 0.10) in pigs fed the C-SPC relative to pigs fed the C-SPC + isoflavone diet in the late finishing period; otherwise, growth performance was not affected (P > 0.10) by diet. Longissimus muscle area, 10th-rib fat depth, percentage muscling (National Pork Producers Council), 24-h pH and temperature, color, firmness-wetness, marbling, drip loss, and CIE L*, a*, and b* color values were not affected (P > 0.10) by diet. Dressing percentage, carcass length, weight and percentage of fat-free lean in ham and carcass, lean gain per day, lean:fat, and ham weight were increased (P < 0.10), and ham fat and percentage fat in ham and carcass were decreased (P < 0.10) in pigs fed the C-SPC + isoflavone diet compared with pigs fed the C-SPC diet. Pigs fed the C-SPC + isoflavone diet had similar (P > 0.10) carcass traits as pigs fed the C-SBM diet, except carcass length, percentage ham lean and thaw loss were greater (P < 0.10), and total ham fat was less (P < 0.10) in pigs fed the C-SPC + isoflavone diet. In Exp. 2, 60 gilts (initial and final BW, 31 and 116 kg, respectively) were used, and each treatment was replicated five times with four pigs per replicate. The treatments were 1) C-SBM, 2) C-SBM + isoflavone levels two times those in C-SBM, and 3) C-SBM + isoflavone levels five times those in C-SBM. Daily feed intake was linearly decreased (P < 0.10) in the growing phase and increased (P < 0.10) in the late finishing phases as isoflavone levels increased; otherwise, growth performance was not affected (P > 0.10) by diet. Diet did not affect (P > 0.10) carcass traits; however, CIE a* and b* color scores and drip loss were decreased (P < 0.06) as isoflavone levels increased. Soy isoflavones decreased fat and increased lean in barrows when fed within the dietary concentrations found in typical C-SBM diets but not when fed to gilts at concentrations above those present in C-SBM diets.     

IGF-I- and EGF-dependent DNA synthesis of porcine myoblasts is influenced by the dietary isoflavones genistein and daidzein

Soy-derived isoflavones have been reported to be specific inhibitors of protein tyrosine kinases like the type 1 insulin-like growth factor receptor (IGF-1R) and the epidermal growth factor receptor (EGFR). This study was conducted to investigate, whether IGF-I and EGF stimulate porcine myoblast growth and whether the responses are influenced by isoflavones. Satellite cell-born myoblasts derived from the semimembranosus muscle of newborn piglets were treated for 26h with IGF-I or EGF alone and in combination with genistein or daidzein. The DNA amount was measured and DNA synthesis was recorded as 6 h-[(3)H]thymidine incorporation during exponential growth in serum-free basal medium. IGF-I and EGF synergistically stimulated DNA synthesis of porcine myoblast with EGF causing a greater response. Genistein (100mumol/l) effectively reduced the growth factor-mediated DNA synthesis, which was associated with an inhibition of growth factor receptor protein expression. In response to daidzein no reduction in growth factor-mediated DNA synthesis was found. Daidzein (1; 10mumol/l) combined with IGF-I caused even a slight increase in DNA amount compared with the untreated control. The expression of the IGF-1R precursor protein was reduced with 10 and 100mumol/l daidzein, whereas the EGFR expression remained unchanged with daidzein. The results suggest that dietary isoflavones may interact with growth factor-induced stimulation of pig skeletal muscle growth.     

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.     

The histamine content of commercial pet foods

The histamine contents of a range of North American commercial pet foods and pet food ingredients were determined by a spectrofluorometric technique. The change in histamine content of open cans of pet food stored in a refrigerator or at room temperature was also investigated. The histamine content of the pet foods examined ranged from a low of 0.16 microg/g in a liquid critical care diet to a high of 65.5 microg/g in a canned fish diet. The amount of histamine in the foods tested was insufficient to cause histamine toxicosis but it cannot be excluded that some of the foods contained sufficient histamine to cause idiosyncratic reactions in histamine-sensitive cats. Storage of opened cans of pet food, either under refrigeration or at room temperature, did not significantly increase the histamine content of most pet foods.     

Taste Preferences and their Relation to Obesity in Dogs and Cats

In the laboratory situation the preferences of dogs and cats for food seem to be relatively uniform. Cats prefer fish and commercial cat food to rats. Dogs prefer beef, pork and lamb to chicken, liver and horsemeat and strongly prefer meat to cereal diets. They prefer canned meat to fresh meat, ground meat to cubed meat and cooked meat to raw meat. Canned or semimoist preparations are preferred to dry ones. Pet dogs have much more variable preferences according to their owner's subjective evaluation. A variety of factors seem to be related in an as yet unknown way to some flavor preferences of pet dogs, i.e. the dog's sex/reproductive status, weight and relationship to owners and the content of the dog's meals. The complicated interaction between (a) a pet's taste, texture and olfactory sensation, (b) its owner's perception of the pet and its preferences and (c) its physical and social environment deserves further investigation.

Obesity can result from endocrinological causes such as those following ovariohysterectomy, but most cases appear to be related to owner-induced variables. In a kennel situation most, but not all, dogs can be allowed free access to palatable food without becoming obese.