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1.
Lead and cadmium levels were determined in 131 infant foods. Mean lead and cadmium levels were 19.3 and 3.3 ng/g for meats, 8.4 and 4.1 ng/g for vegetables, 14.9 and 0.58 ng/g for fruits and desserts, 9.6 and 0.53 ng/g for juices and drinks, and 32.8 and 33.6 ng/g for dry infant cereals. These data, combined with those from other recent surveys, yielded average dietary (food and water) intakes of lead and cadmium by infants 0-1 year old of 2.4 and 0.37 microgram/kg/day, respectively. Lead intakes were most strongly influenced by storage of infant formulas in lead-soldered cans. For infants 0-1 month old, they ranged from 0.5 microgram/kg/day when human or cow milk was fed to infants to 5.3 micrograms/kg/day (exceeding the FAO/WHO provisional tolerable daily intake, PTWI, of lead by children of 3.5 micrograms/kg) when ready-to-use formula stored in lead-soldered cans was fed. Cadmium intakes were most strongly affected by soya based formulas, and ranged, for 0-1 months olds, from 0.16 microgram/kg/day for infants fed human or cow milk to 0.50 microgram/kg/day for infants fed soya-based concentrated liquid formula. Cadmium intakes were all below the FAO/WHO PTDI of cadmium by adults of 0.96-1.2 micrograms/kg.  相似文献   

2.
Lead (Pb), cadmium (Cd) and aluminum (Al) were determined in 437 individual samples of infant formulae, oral electrolytes and 5% glucose solutions available in Canada. In the electrolytes, Cd and Pb concentrations were all below 0.01 and 0.041 ng g(-1), respectively. In the 5% glucose solutions, Pb and Cd levels averaged 0.01 and 0.09 ng g(-1), respectively. Reported on an as-consumed basis, Pb levels in milk- and soya-based formulae averaged 0.90 and 1.45 ng g(-1), respectively, while Cd levels averaged 0.23 and 1.18 ng g(-1), respectively Average Al levels on an as-consumed basis were 440 ng g(-1) (range 10-3400 ng g(-1)) in milk-based formulae and 730 ng g(-1) (range 230-1100 ng g(-1)) in soy-based formulae. Al concentrations increased in the following order: plain formula < low-iron formula < iron-supplemented formula < casein hydrolysate formula ≈ premature formula ≤ soy formula. For example, in the powdered formulae, average Al concentrations were 18 ng g(-1) for plain milk-based, 37 ng g(-1) for low-iron, 128 ng g(-1) for iron supplemented, 462 ng g(-1) for lactose-free, 518 ng g(-1) for hypoallergenic and 619 ng g(-1) for soy-based formula. Al concentrations, as-consumed, increased with decreasing levels of concentration: powder < concentrated liquid < ready-to-use. Formulae stored in glass bottles contained between 100 and 300 ng g(-1) more Al than the same formulae stored in cans. The source of the increased Al did not appear to be the glass itself, because most electrolytes and glucose solutions, also stored in glass, contained less than 8 ng g(-1) Al. Corresponding differences in Pb and Cd levels were not observed. Al concentrations varied substantially among manufacturers; however, all manufacturers were able to produce plain milk-based formulae containing less than 50 ng g(-1) Al, i.e. within the range of Al concentrations found in human milk. Next to soya-based and hypoallergenic formulae, premature formulae contained among the highest concentrations of Al, ranging 851-909 ng g(-1) from one manufacturer and 365-461 ng g(-1) from another.  相似文献   

3.
Total mercury (Hg) was measured in 150 infant formula products (as sold) and oral electrolyte solutions purchased in Canada in 2003. Results less than the limit of detection (LOD) were reported as the numeric value of the LOD. Electrolytes contained the lowest concentrations, averaging 0.026?ng/g. Average levels in milk-based ready-to-use, concentrated liquid and powdered concentrate were 0.028, 0.069 and 0.212?ng/g, respectively. In soy-based formulae, the respective mean concentrations were 0.049, 0.101 and 0.237?ng/g. These concentrations cannot be considered on an absolute basis because 76% of sample concentrations fell below the limit of detection. Despite the inability to measure many of the actual background concentrations, the method was sufficiently sensitive to identify clear cases of low-level Hg contamination (up to 1.5?ng/g) of individual lots of powdered formula. Also, all the different lots of one brand of concentrated liquid infant formulae had significantly higher concentrations of Hg than those of all other concentrated liquid products. After dilution with preparation water, the Hg concentrations in all products would be lower than the Canadian Drinking Water Guideline for Hg of 1?ng/mL and too low to impact on health.  相似文献   

4.
Levels of aluminium in 82 different infant formulae from nine different manufacturers in Spain were determined by acid-microwave digestion and graphite furnace atomic absorption spectrophotometry. The influence of aluminium content in tap water in reconstituted powder formulae was examined and an estimate was made of the theoretical toxic aluminium intake in comparison with the provisional tolerable weekly intake (PTWI). Possible interactions between aluminium and certain essential trace elements added to infant formulations have been studied according to the type or main protein-based infant formula. In general, the infant formulae contained a higher aluminium content than that found in human milk, especially in the case of soya, preterm or hydrolysed casein-based formulae. Standard formulae gave lower aluminium intakes amounting to about 4% PTWI. Specialized and preterm formulae resulted in a moderate intake (11-12 and 8-10% PTWI, respectively) and soya formulae contributed the highest intake (15% PTWI). Aluminium exposure from drinking water used for powder formula reconstitution was not considered a potential risk. In accordance with the present state of knowledge about aluminium toxicity, it seems prudent to call for continued efforts to standardize routine quality control and reduce aluminium levels in infant formula as well as to keep the aluminium concentration under 300 μg l-1 for all infant formulae, most specifically those formulae for premature and low birth neonates.  相似文献   

5.
Perchlorate is a naturally occurring inorganic anion used as a component of solid rocket fuel, explosives, and pyrotechnics. Sufficiently high perchlorate intakes can modify thyroid function by competitively inhibiting iodide uptake in adults; however, little is known about perchlorate exposure and health effects in infants. Food intake models predict that infants have higher perchlorate exposure doses than adults. For this reason, we measured perchlorate and related anions (nitrate, thiocyanate, and iodide) in 206 urine samples from 92 infants ages 1-377 days and calculated perchlorate intake dose for this sample of infants. The median estimated exposure dose for this sample of infants was 0.160 μg/kg/day. Of the 205 individual dose estimates, 9% exceeded the reference dose of 0.7 μg/kg/day; 6% of infants providing multiple samples had multiple perchlorate dose estimates above the reference dose. Estimated exposure dose differed by feeding method: breast-fed infants had a higher perchlorate exposure dose (geometric mean 0.220 μg/kg/day) than infants consuming cow milk-based formula (geometric mean 0.103 μg/kg/day, p < 0.0001) or soy-based formula (geometric mean 0.027 μg/kg/day, p < 0.0001), consistent with dose estimates based on dietary intake data. The ability of perchlorate to block adequate iodide uptake by the thyroid may have been reduced by the iodine-sufficient status of the infants studied (median urinary iodide 125 μg/L). Further research is needed to see whether these perchlorate intake doses lead to any health effects.  相似文献   

6.
有机大豆粉富含优质蛋白、矿物质和微量元素,是一类非乳配方粉的主要原材料。本研究以有机大豆粉及大豆分离蛋白为蛋白源,开发出不含乳糖的豆基婴儿配方粉。通过配方粉的化学成分、氨基酸、微观结构、渗透压等指标的测定与分析对配方粉的品质进行了研究,使用蛋白质功效比值法评价配方粉的营养,结果表明该豆基婴儿配方粉营养成分与GB 10765—2021《食品安全国家标准 婴儿配方食品》设计值相符合,必需氨基酸组成优于市售豆基婴儿配方粉,氨基酸评分(amino acid score,AAS)更平衡,且强化组氨酸等必需氨基酸可以满足婴儿需求,起到代替母乳的作用;透射电子显微镜观察发现该配方粉与市售豆基婴儿配方粉相比,颗粒分布更加均匀,具有更好的体系稳定性,且该配方粉渗透压((281.00±1.20)(mOsm/kg H2O))符合婴儿体液平衡的需求。蛋白质功效比值(protein efficiency ratio,PER)分析结果表明该配方粉的大鼠实验组体质量总增长率和PER均优于酪蛋白参比组,具有较好的促进生长发育功效,营养价值较高,本研究可为研制豆基婴儿配方粉提供基础数据。  相似文献   

7.
Aluminium levels in infant formulae purchased in 1990 and prepared as for consumption were in the range 530 micrograms/l to 640 micrograms/l for soya-based products and 27 micrograms/l to 120 micrograms/l for cows' milk-based formulae. Mean aluminium concentrations in these soya and cows' milk-based samples were, on average, 37% and 45% lower, respectively, than those of the same brands purchased between 1985 and 1987. Levels of aluminium in breast milk were in the range 3 micrograms/l to 79 micrograms/l. In the case of retail cows' milk, values ranged from 4 micrograms/l to 33 micrograms/l whilst more variable amounts of between 5 micrograms/l and 285 micrograms/l were detected in retail soya milk.  相似文献   

8.
Cadmium levels were determined in 59 baby food samples, including milk-based, cereal and milk-based and soy-based formulas, recommended from 0 to 18 months of age. Determinations were performed by Zeeman graphite furnace atomic absorption spectrophotometry, after dry ashing, with parallel determinations of certified reference samples. Mean cadmium levels were found to range from 1.10 to 23.5 mu g / kg fresh weight concentrated formulas. L evels were related to the composition of the diets. Formulas based on cow's milk had the lowest concentrations. Soy formulas contained approximately six times more cadmium than cow's milk formulas, and diets with a cereal content had 4-21 times higher mean levels. The mean weekly intakes of dietary cadmium were estimated to vary between 0.10 and 3 : 05 mu g / kg body weight of the child, if the recommended amount of formula were to be consumed at the recommended age, and if the child were of average weight. This estimation however does not include the contribution of cadmium from drinking water. The highest intake on a body weight basis was found in 6-month-old children, consuming the recommended amount of wheat-, oat- and milk-based formulas. This intake is below the provisional tolerable weekly intake (PTW I) of 7 mu g / kg body weight, established by a W HO/FAO expert group. However, the risk assessment is based on renal effects in adults. Furthermore, preparations of a formula by adding water with cadmium concentrations at the W HO guideline level could lead to intakes at the PTW I level. Compared to breast-fed children, the exposure of dietary cadmium from weaning diets can be up to 12 times higher in children fed infant formula.  相似文献   

9.
A survey of the pesticide content of 25 commercially available infant formulae and 30 weaning foods available in New Zealand was undertaken in 1996. It included a representative mixture of imported and New Zealand manufactured infant foods. Three different pesticide screening techniques were used: a high-sensitivity organochlorine screen was carried out on all infant formulae, while a multiresidue screen (organochlorine and organophosphorus pesticides, synthetic pyrethroids, carbamate pesticides, fungicides and herbicides), and a specific screen for dithiocarbamate fungicides were both carried out on all weaning foods and on soy-based infant formulae. All results are expressed on a ready-to-feed basis. Extremely low levels of residues of three organochlorine compounds (p,p'-DDE, p,p'-DDT and dieldrin) were detected in infant formulae samples. Residues of p,p'-DDE were found in seven of 20 milk-based infant formulae at concentrations ranging from 0.03 to 0.5 μg kg-1. Residues of p,p'-DDT were found in one imported milk-based infant formula at 0.7 μg kg-1, and dieldrin residues were detected in four of five soy-based infant formulae at concentrations ranging from 0.05 to 0.08 μg kg-1. The multiresidue pesticide screen detected low levels of residues of two organophosphorus pesticides; azinphos-methyl in one soy-based infant formula at a level of 22 μg kg-1 and pirimiphos-methyl in two cereal-based weaning foods at concentrations of 5 and 14 μg kg-1. None of the other approximately 140 pesticides (including fungicides and herbicides) included in the multiresidue screen were detected in any weaning foods or soy-based infant formulae, at a detection limit of 10 μg kg-1. No residues of dithiocarbamate fungicides were detected in any product analysed, at a detection limit of 100 μg kg-1.  相似文献   

10.
Twenty-four hour duplicate diets, including drinking water and snacks, were collected from 24 adults living in five Canadian cities. Each diet was separated by the participants into 10 food categories, and each of the samples was analyzed in duplicate for lead, cadmium, arsenic and fluoride. Minimum detection limits for the respective elements in foods were about 0.1, 0.01, 0.3 and 5 ng/g. Mean dietary intakes were 53.8 micrograms/day or 0.80 micrograms/kg/day for lead, 13.8 micrograms/day or 0.21 micrograms/kg/day for cadmium, and 16.7 micrograms/day or 0.26 micrograms/kg/day for arsenic. The median intakes were 42.7 micrograms/day or 0.57 mu/kg/day for lead, 11.9 micrograms/day or 0.17 micrograms/kg/day for cadmium, and 9.79 micrograms/day or 0.139 micrograms/kg/day for arsenic. Half of the participants lived in communities with 1 microgram/g fluoride in the drinking water, and half lived in cities with less than 0.2 microgram/g fluoride in the water. The dietary intake of fluoride for the former was 2802 micrograms/day or 39.7 micrograms/kg/day; while that of the latter was 563 micrograms/day or 8.5 micrograms/kg/day. The respective median intakes of fluoride were 2090 micrograms/day or 30.3 micrograms/kg/day, and 414 micrograms/day or 7.0 micrograms/kg/day. Contribution of individual foods and food categories to the dietary intakes is discussed.  相似文献   

11.
Lead concentrations in 82 different types of infant formulae (cow's milk and soy based) marked in Spain were analysed by acid-microwave decomposition and anodic stripping voltammetry. Dietary lead intake from infant formula and tap water used for powder formula reconstitution were estimated in comparison with the provisional tolerable weekly intake (PTWI). Additionally, the influence of physical state (powder and ready-to-use formulae), the type of container used and the impact of the industrial process from different manufacturers on lead levels were evaluated. According to the results, lead exposure from drinking water was negligible with respect to formulae investigated; where soya formulae contributed the highest intake (58-73% PTWI), non-adapted starter and specialized formulae gave an moderate intake (31-42 and 26-37% PTWI, respectively), and, finally, pre-term, adapted starter and follow-up formulae provided the lowest lead intake (22-25, 22-26 and 16-22% PTWI, respectively). Based on the current state of knowledge about lead toxicity, manufacturers are called to make an additional effort in order to keep a maximum lead level at 20 µg l-1 for all infant formulae, although it is recommendable that these formulations supply the upper limit (5 µg l-1) of 'normal' human milk.  相似文献   

12.
Diets with different fat treatments and with 25, 125, or 250 IU of supplemental vitamin E (all-rac alpha-tocopheryl acetate)/kg of dry matter (DM) were fed for 28 d to midlactation Holstein cows to determine factors affecting concentrations of alpha-tocopherol in milk. Diets contained no supplemental fat or 2.25% added fat from roasted soybeans or tallow. Vitamin E treatment had no effects on production, but fat supplementation increased milk yield (37.2 vs. 35.1 kg/d). Cows fed RSB ate more DM (24.0 vs. 21.9 kg/d) and produced more milk fat than cows fed tallow. Supplemental fat increased plasma concentrations of alpha-tocopherol and cholesterol. Increased intake of alpha-tocopherol linearly increased concentrations of alpha-tocopherol in plasma but the rate of increase was 1.9 times greater when fat was fed. Plasma alpha-tocopherol concentrations were linearly related to concentrations in milk, but a change in plasma alpha-tocopherol resulted in a smaller change in milk alpha-tocopherol when fat was fed than when it was not. Fat treatment did not affect plasma alpha-tocopherol expressed relative to plasma cholesterol (mg alpha-tocopherol/g cholesterol) or relationships between plasma alpha-tocopherol/g of cholesterol and milk alpha-tocopherol. These data suggest that concentrations of alpha-tocopherol in milk are a function of the alpha-tocopherol enrichment of the plasma lipid fraction and enrichment of that fraction is saturable.  相似文献   

13.
The presence of mycotoxins in corn-based foods available in Argentina was determined in order to make a preliminary exposure assessment. Thirty-eight samples [corn meal ('polenta') and corn flakes] of different local brands were analysed for zearalenone, deoxynivalenol and aflatoxins by TLC and fumonisins (FB1, FB2 and FB3) by HPLC. None of the 38 samples contained any detectable amount of aflatoxins (< 2 micrograms/kg), zearalenone (< 50 micrograms/kg) and deoxynivalenol (< 50 micrograms/kg). By contrast fumonisin contamination was found in 95% of the samples. The highest fumonisin levels were found in corn meal: FB1 (range positives: 60-2860 micrograms/kg; mean positive value: 556 micrograms/kg), FB2 (61-1090 micrograms/kg; 232 micrograms/kg) and FB3 (18-1015 micrograms/kg; 150 micrograms/kg). Low levels of fumonisin B1 were detected in 16/17 corn flakes samples (2-38 micrograms/kg). Total fumonisin levels in corn meal were more than 1000 micrograms/kg in 24% (5/21) of the samples. Although it is not the staple food in Argentina, maize consumption is very important, especially among children. A daily fumonisin intake of 11.3 micrograms/kg of body weight was estimated for child consumers (1-5 years old) based on an average consumption of 200 g of corn meal/day. Calculated at an average rate for all children (consumers or not) the intake estimate was 0.9 microgram/kg of body weight.  相似文献   

14.
Two experiments were performed using lactating cows fed various treated and non-treated commodities from AFB1 contaminated peanut cakes. Treatment with ammonia gas by an autoclaving process was used for detoxification. Two methods were used for AFM1 determination in every milk sample: a TLC procedure recognized by AOAC and IDF and an HPLC method with a detection limit of 0.100 and 0.010 microgram/l, respectively. In a first experiment, lactating cows were fed treated and untreated meals during periods separated by uncontaminated soya meals phases. The total excreted AFM1 was 2.6% of the total ingested AFB1 from untreated feed contaminated at 1100 micrograms/kg. During periods receiving treated meals in the diet, AFM1 contents in milk were below 0.1 microgram/l. However, by using AFM1 data obtained using the HPLC method, an AFM1/AFB1 ratio of 4.6% was found from treated feed contaminated at 40 micrograms AFB1/kg. In a second experiment, a herd of 50 lactating cows was used for a long term (16 months) feeding of mixed commodities containing 30% ammoniated peanut cakes. AFB1 residues in the treated diet were below 10 micrograms/kg, the EEC action level, and no AFM1 residue was found up to 0.1 microgram/l in collected milk throughout this experiment.  相似文献   

15.
Mammary transfer of vitamin E in dairy cows   总被引:1,自引:0,他引:1  
Milk vitamin E from eight dairy cows was analyzed for vitamin E by HPLC during the 1st mo of lactation. Colostrum gave a mean value of 1.9 micrograms alpha-tocopherol/ml while concentrations of fresh milk averaged .3 microgram alpha-tocopherol/ml. D-gamma-tocopherol concentrations were observed in very small amounts. When six cows at the end of the 1st mo of lactation were injected intraperitoneally with an emulsion of dl-alpha-tocopherol acetate (5 g), plasma and milk concentrations of alpha-tocopherol were increased from their original values of 4.5 micrograms/ml plasma and .3 microgram/ml fresh milk to 10.9 micrograms/ml plasma and 1.6 micrograms/ml fresh milk, 12 h later. The results show that intraperitoneal administration of vitamin E to dairy cows in an effective way of increasing plasma and milk tocopherol concentration.  相似文献   

16.
Ten Holstein cows in mid-lactation which had been fed only stored feeds for several years were paired on milk production. One cow from each pair was assigned to either the control or group treated with supplemental vitamin E for a 12-wk experiment. All cows were fed 3 kg alfalfa-brome hay, corn silage ad libitum, and concentrate at 1 kg/3 kg milk produced daily. This ration provided about 500 mg of vitamin E (total tocopherols) daily. Five cows were fed an additional 300 mg vitamin E daily as D-alpha-tocopherol acetate in their concentrate mix. Feeding the supplemental vitamin E increased the vitamin E content of milk fat 15 to 20% from 18 microgram/g fat to over 21 microgram/g fat. However, this change in vitamin E content of milk was not sufficient to improve the oxidative stability of the milk. Blood characteristics indicative of vitamin E status generally were unaffected by vitamin E supplementation although red cell hemolysis, glutamic oxaloacetic transaminase, and lactate dehydrogenase of serum were lower in blood of supplemented cows.  相似文献   

17.
Supplementing cows grazing highly digestible pasture with a Saccharomyces cerevisiae fermentation product (SCFP) was hypothesized to increase dry matter (DM) intake and milk production. Sixty multiparous dairy cows were fed 3 kg of crushed triticale DM/cow per day for 23 ± 4.4 d before calving. Half of the cows received SCFP (60 g/d; Diamond V Original XP; Diamond V Mills, Inc., Cedar Rapids, IA). Cows in both treatment groups were randomly allocated at calving to 1 of 2 amounts (3 or 6 kg of DM/d) of triticale feeding with or without 60 g of SCFP/day (n = 15/treatment) until 84 days in milk. The amount of pasture harvested (kg of DM/cow per day) and milk yield (kg/cow per day) were not affected by SCFP. Milk protein content and yield were greater in cows receiving 6 kg of crushed triticale DM/d. Plasma nonesterified fatty acids and β-hydroxybutyrate concentrations were not affected by SCFP supplementation, but were lower in cows fed 6 kg of crushed triticale DM/d than those fed 3 kg of DM/d. Supplementation with SCFP increased milk lactose content without affecting milk production under the conditions investigated.  相似文献   

18.
The aim of this study is to obtain data on the exposure of non-breast-fed infants to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), polychlorinated biphenyls (PCB), organochlorine pesticides (OCP), and bisphenol A (BPA) and its chlorinated derivatives through consumption of commercial infant foods with largest shares of the market in 22 European Union countries. The E-Screen bioassay was employed to assess the oestrogenicity of the baby foods and the ethoxyresorufin-O-deethylase (EROD) induction was measured to determine the levels of PCDD/F and PCB. Consequently, the highest total effective xenoestrogen burden (TEXB) of 73.60?pM?Eeq?g(-1) was found in the soy-based formula and the EROD bioassay was always below the limit of quantification (LOQ) (3.5?pg?g(-1)). Overall, the estimated dietary exposure to BPA via commercial baby foods was lower than the tolerable daily intake (TDI) of 50?μg?kg(-1) body weight (bw). Furthermore, the findings indicated that the dietary exposure of 0-9-month-old infants through the products investigated here does not exceed the maximum TDI of 4?pg WHO-TEQ (toxic equivalents)?kg(-1) bw. However, exposure to more than 2?pg WHO-TEQ?kg(-1)?bw?day(-1) might occur for 0-4-month-old infants consuming 'starting' hypoallergenic formula. Moreover, analysis of OCP indicated that the dietary exposure of non-breast-fed infants was not harmful. Considering the importance of early development and the vulnerability of infants and children, it is essential to determine their dietary exposure to contaminants in order to decide which efforts of risk reduction should receive highest priority.  相似文献   

19.
The assessment of acute and chronic dietary exposure to contaminants in baby foods is needed to ensure healthy infant growth. Monthly European Union market baskets of commercial baby foods were designed for the first 9 months of life by the ‘babyfood’ study group of the CASCADE Network of Excellence for the specific purpose of assessing exposure to potentially toxic substances in infants fed with such foods. The present paper reports the different steps that led to the preparation of monthly pooled samples of commercial baby foods (‘Infant formulae and follow-on formulae’ and ‘Other baby foods’) that may constitute the extreme case of the diet for an infant who would not be breast fed at all. Several market baskets were generated for an ‘average European Union infant’ and for infants of four selected countries (Italy, Sweden, Spain, and the Slovakia), fed with either milk infant formulae, soy infant formulae or hypoallergenic infant formulae and weaned (at the fifth month) with commercial baby foods and beverages available on the European Union market. Market share data for 2007 for baby foods were used to design the baskets. Holding companies and the name of all their products were identified. Monthly diets for European Union infants were elaborated in terms of food categories (e.g. infant cereals) of typologies of products (e.g. infant cereals without gluten) and of a specific product. The number of baskets generated was 30 for ‘Infant formulae and follow-on formulae’ (including 62 products) and 13 for ‘Other baby foods’ (including 35 products). These market baskets were designed to be used for the determination of certain contaminants and nutrients in the diet of European Union infants and for the assessment of their effects on infant health.  相似文献   

20.
Our previous published work demonstrated that feeding rumen-degradable valine to late-lactation dairy cows increased milk production compared with control-fed cows, with a response that was equivalent to that of recombinant bovine somatotropin. To further elucidate the response mechanism, we hypothesized that thyroxine (T4) and triiodothyronine (T3), which are important regulators of basal metabolism, may be involved. Previous short-term studies have demonstrated increased milk production when feeding iodinated casein. Eight multiparous Holstein dairy cows (255 ± 26.4 d in milk) were blocked by milk yield (34.1 ± 8.25 kg/d) and randomly assigned to 1 of 4 treatments using a replicated 4 × 4 Latin square design with 21-d periods (7 d for dietary adaptation and 14 d for data collection). Treatments were control (CON), a single injection of recombinant bovine somatotropin (rbST), and synthetic valine fed at 40 (V40) or 80 (V80) g/cow per day. Cows were fed a total mixed ration with a distillers dried grains carrier fed at 113.4 g/d containing no valine or added valine. Blood samples were collected twice during wk 2 and 3 of each period for T3 and T4 analysis. Concentrations of T4 (3.28, 3.90, 3.98, and 3.87 µg/dL for CON, rbST, V40, and V80, respectively) were increased for cows receiving rbST, V40, and V80 compared with CON cows. Concentrations of T3 (125.7, 140.7, 148.8, and 139.7 ng/dL) were increased for cows receiving rbST, V40, and V80 compared with CON cows, with cows receiving V40 having the highest T3 concentrations. In conclusion, feeding rumen-degradable valine increases plasma T4 and T3 concentrations, which would explain the mechanism leading to increased milk production.  相似文献   

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