VcPP的稳定性和生物利用率

1 VcPP的稳定性 为了改善 Vc的稳定性,使之更适合于加入饲料中,人们开发出多种稳定型的 Vc制剂商品。 VcPP是近年来国际市场新出现的一种高稳定性的 Vc衍生物,大量试验表明,该产品加入饲料中稳定性极好,同时又具有很高的生物利用率。 1.1自身贮存的稳定性 VcPP产品相当稳定,将它装于塑料袋中置入纤维板包装桶存放于仓库中,经一年的效价分析跟踪（每 3个月测定一次）,年平均效价损失率为 4.2％。具体数据见表 1。 VcPP效价指产品中所含的有效成分被磷酸酯酶水解而转化为 Vc的质量分数（质量百分比）。一般的 VcPP合成品…     

维生素的作用和营养

维生素需要量美国国家科学研究委员会 (ＮＲＣ)提出了畜禽在集约化饲养管理条件下对维生素的推荐需要量。ＮＲＣ的营养需要量标准形成了制定商品家禽维生素需要量的基础 ,以便预防家禽的维生素缺乏症。这些推荐需要量数据经常更新 ,以便将最新的研究结果包括进去。ＮＲＣ推荐量与任何现代商品猪种或者其特定的商业参数有联系。ＮＲＣ推荐量数据是用以评价商品鸡饲料中维生素添加率的基础。为了确定鸡饲料中的维生素添加率 ,常常需要在不同的饲养管理条件下再次进行评价。一般来说 ,ＮＲＣ推荐量被认为是鸡饲料中的维生素最低添加水平 ,在考…     

维生素的稳定性和商品制剂

所有的维生素都一定程度地对不良储存和处置条件敏感。为了保持维生素原来的效价 ,以下简要介绍维生素对之最为敏感的一些条件以供读者参考 :维生素Ａ、Ｄ和类胡萝卜素·暴露于空气中时容易被氧化 ;·对氧化剂敏感 ;·在酸性条件下会形成异构体 ;·对长时间加热敏感 ;·对金属的催化作用敏感。维生素Ｅ·对空气的氧化作用敏感 ;·‘对碱敏感 ;·酯的形态比较稳定。维生素Ｋ3·对热敏感 ;·接触氧时对氧化敏感。硫胺素 (维生素Ｂ1)·在低 ｐＨ值条件下比较稳定 ,效价随 ｐＨ值升高而降低 ;·对氧和中性或碱性溶液中的氧化剂敏感 ;·在亚硫酸…     

利用近红外线反射分析法研究以放牧或谷物为主牛的碎肉中添加维生素C对肉色、脂肪稳定性、脂肪酸组成的影响

本试验的目的是为了探讨添加 VC(试验组 )和不添加 VC(对照组 )对以放牧或谷物为饲养主牛的牛肉肉色和脂肪稳定性的影响 ,牛肉在 4℃下放置 8d后观察肉色和脂肪稳定性。采用近红外线反射分光镜预测碎牛肉的脂肪酸组成 ,并评估此法在鉴别不同营养背景下牛肉的潜在价值。以放牧为主牛的牛肉总脂肪含量要比以谷物为主牛的低 5 3% (P<0 .0 5 )。放牧为主饲养牛的牛肉有较高的饱和脂肪酸 (P<0 .0 1)和多聚不饱和脂肪酸含量 ,以及较少的单一不饱和脂肪酸 (P<0 .0 1)。在以谷物为主饲养牛的牛肉中 ,添加 VC试验组比对照组 ,从第 2～ 8d脂肪氧化减慢 (P<0 .0 1) ,肉色更深(P<0 .0 1) ,颜色更红 (P<0 .0 1)。以放牧为主牛的牛肉 ,添加VC试验组与对照组相比较 ,脂肪的氧化差异不显著 (P>0 .0 5 ) ,但在 8d的试验期 VC可延缓肉色加深 ,从而提高肉色的稳定性 (P<0 .0 1)。采用最小二乘均方模型结果表明 ,使用近红外线反射分析法可准确预测饱和脂肪酸 (标准误 SEP=1.16 % ,准确度 r2 =0 .87)、不饱和脂肪酸 (标准误 SEP=1.18% ,准确度 r2 =0 .90 )、硬脂酸 (标准误 SEP=1.2 0 % ,准确度 r2 =0 .91)、油酸 (标准误 SEP=1.2 7% ,准确度 r2 =0 .92 )和亚麻油酸 (标准误 SEP=0 .0 7% ,准确度 r2 =0 .93)的含量。然而其它     

Bioavailability of ascorbic acid in horses

The bioavailability of ascorbic acid administered to thoroughbreds by intramuscular injection was investigated. For intramuscular injection two preparations were studied, and the percentage bioavailability up to 24 h of 10 g of ascorbic acid was 95% +/- 22 in four horses and 60% in two horses with preparations A and B, respectively. Bioavailability at 24 h in three horses injected subcutaneously with 10 g of preparation B was 82%. Intramuscular injection of both preparations was apparently well tolerated while subcutaneous injection of preparation B (pH 6.0) was associated with marked irritancy. In a cross-over trial in seven thoroughbreds the effect of 13 or 15 days of oral administration of crystalline ascorbic acid (20 g) or ascorbyl palmitate (47 g) on plasma ascorbic-acid concentrations was investigated. Marked differences occurred between individuals. There was a greater increase in plasma ascorbic-acid concentration with ascorbyl palmitate compared to ascorbic acid at 6 and 24 h following administration. In two horses there was no increase in plasma ascorbic acid at 6 h following either oral preparation. The finding of lowered plasma ascorbic-acid concentrations following a period of supplementation warrants further investigation to assess its significance.     

Pharmacokinetics of ascorbic acid in horses

The pharmacokinetics of ascorbic acid were studied in 29 horses after intravenous (iv), subcutaneous, intramuscular (im) and oral administration. Following iv injection of 5 and 10 g ascorbic acid, respectively, a biphasic decline of ascorbic acid serum levels was found, indicating that the vitamin distributes in the body according to a two-compartment open model. The apparent volume of distribution (average value for V_d(ss)= 0.6 litre/kg) was approximately equivalent to the volume of total body water. The terminal half-life of the biexponential serum level-time curve (t_1/2β) varied between 5 and 17 h. Both distribution and elimination were found to be positively correlated with the iv dose administered. Following subcutaneous and im injection, the average bioavailability of ascorbic acid amounted to 82 and 61 per cent, respectively. However, both routes of administration gave rise to marked local irritation. Following oral administration, the systemic availability of ascorbic acid was very poor. Serum levels in most experiments were not increased above the endogenous pre-administration values of the vitamin. Thus, in horses iv injection appears to be the only satisfactory route of administration of ascorbic acid if supplementation is required.     

Sexual difference in ascorbic acid synthesis, tissue ascorbic acid and plasma total antioxidant capacity in mature chickens

1. An experiment was conducted with commercial White Leghorn type chickens to determine the effect of gender on tissue ascorbic acid concentration, antioxidant capacity and ascorbic acid synthesis. 2. Birds reared and maintained on litter were given a standard layer diet, without supplemental ascorbic acid, from 18 weeks of age. Tissue ascorbic acid concentration, plasma total antioxidant capacity and renal L-gulonolactone oxidase activity were measured at 30 weeks of age. 3. Females and males differed in ascorbic acid synthesis, as measured by renal L-gulonolactone oxidase activity, and tissue ascorbic acid concentration. 4. Plasma total antioxidant capacity and adrenal, gonadal, plasma and pituitary ascorbic acid concentrations were significantly higher in males, whereas ascorbic acid synthesis and splenic and thymic ascorbic acid concentrations were significantly higher in females. 5. L-Gulonolactone oxidase activity was not detected in the comb of cockerels.     

Congenital ascorbic acid deficiency in pigs

In a swine production herd, spontaneous scurvy was observed among piglets 2–3 weeks after weaning. All affected pigs had the same boar as both maternal and paternal grandfather. The affected pigs had only traces of ascorbic acid in blood and tissues as compared to litter mates and other normal pigs. The ratio between the total numbers of normal and affected pigs in the 4 litters concerned was in agreement with a 3:1 segregation, which is characteristic of simple autosomal recessive inheritance in matings between non-affected carriers.Two affected pigs were restored to normal when given ascorbic acid in the diet. Without vitamin C supplement affected pigs died or had to be euthanized.Liver microsomes from an affected pig were unable to synthesize ascorbic acid in vitro with 1-gulonolactone as a substrate, unlike microsomes from normal control pigs.Key words: scurvey, vitamin C, congenital, inbreeding, pigs     

Oral administration of ascorbic acid to horses

The effects of oral administration of high doses of ascorbic acid on plasma concentrations were investigated in both experimental Thoroughbred horses and those within racing stables. A single oral dose (20 g) did not result in any increase in plasma concentrations. However, daily administration of either 4.5 g or 20 g doses resulted in significant increases in plasma concentrations. Monthly variations in plasma ascorbate concentrations were found in both supplemented (20 g daily) and unsupplemented stables. It is concluded that oral supplementation with ascorbic acid is a satisfactory route to increase plasma and tissue concentrations.     

Plasma ascorbic acid concentrations in healthy dogs

Using a highly sensitive and selective analytical method and careful stability control, plasma concentrations of ascorbic acid were determined in German Shepherd Dogs, Labrador Retrievers and Siberian Huskies, a total 99 animals. Mean concentration was 35.9 micromol l(-1)(range 18.2-50.7), and no significant variation was observed neither between breeds nor between females and males. These and previous reported data on plasma ascorbic acid levels in dogs are discussed in the light of methodological aspects.     

Pharmacokinetic study of ascorbic acid in sheep.

Four groups of sheep (5/group) were used in the experiment. Group 1 sheep were given 1 g of ascorbic acid (AA) intravenously (i.v.), group 2 were given 3 g i.v., group 3 were given 1 g intramuscularly (i.m.) and group 4 received 3 g i.m. Blood was collected for 7 h after i.v. administration and for 48 h following i.m. administration. Plasma was analyzed for AA using HPLC techniques. After i.v. administration the rate of elimination was greater at the high dose than the low (0.8560 vs 0.5231 h-1) but the area under the curve (AUC) parameter was proportional to the dosage (127.9 vs 39.7 mcg*h/mL). After i.m. administration AUC parameters were higher than following the i.v. injections. When the times that AA levels were > or = 5 mcg/mL after i.m. injection were compared there was no significant difference between the 1 and 3 g dosages. Times that levels were > or = 10 mcg/mL were significantly longer for the 3 g dose. Using the AUC (area under the curve) parameter as an index of drug exposure, supplementation of adult sheep with AA by the i.m. route should have a greater effect on the animal than i.v. administration.     

Serum ascorbic acid concentrations in previously unsupplemented greyhounds after administration of a single dose of ascorbic acid intravenously or per os

Plasma vitamin C concentrations (mean + SD) were measured after a large (1 g) dose of vitamin C was administered orally or intravenously to each of four trained greyhounds in a randomized cross-over design. Concentrations increased (p<0.05) for 2 h but returned to baseline by 6 h after supplementation. Peak concentrations were greater (p<0.01) after intravenous than oral administration (6.1+/-1.2 vs. 0.54+/-0.23 mg/dl). This suggests that vitamin C must be administered many times daily to maintain plasma concentrations above normal.     

Effects of ascorbic acid on stress and disease in chickens.

White leghorn chickens were given feed containing 100 mg of ascorbic acid (AA)/kg. One day later, treated chickens and a similar group of unmedicated control chickens were chilled for 1 hour at 6 C, exposed to an unusual sound, fasted, or subjected to rough handling. Heterophil:lymphocyte (H:L) ratios were determined one day later. The AA-treated birds had significantly lower H:L ratios than untreated controls. Chickens that received a diet containing AA had lower H:L ratios than controls (0.86 vs. 1.65) following administration of adrenocorticotropic hormone. Chickens fed a diet containing AA showed increased resistance to a combined Newcastle disease virus-Mycoplasma gallisepticum infection and to a secondary Escherichia coli infection, as well as to a primary E. coli challenge infection. The effects of AA and an antibacterial drug (furaltadone) were additive. In all experiments, the optimum dose of AA was 100 mg/kg of feed. There was a negative correlation between AA level in the diet and feed efficiency.