Intramuscular fat and muscle fibre lipid contents in halothane-gene-free pigs fed high or low protein diets and its relation to meat quality

Immediately after exsanguination, samples were taken from M. longissimus dorsi (LD) and M. biceps fermorsi (BF) of halothane-gene-free Swedish Yorkshire pigs (entire males and gilts) fed a high-protein (18·5% crude protein, 0·96% lysine; n = 20) or a low-protein diet (13·1% crude protein, 0·64% lysine; n = 20). The lipid content, measured as triglyceride (TG), was analysed after the samples had been freeze-dried and dissected free from blood, fat and connective tissue. Fibre type composition (type I, IIA, IIB, IIC) was analysed by histochemical staining on all samples. In 14 samples of LD, representing the entire variation of the intramuscular fat content (IMF) among the 40 animals, fibre areas, lipid content and oxidative capacity within the fibre types were evaluated. IMF, meat colour and drip loss were measured in both muscles. Shear force was measured on cooked meat samples from LD. IMF was higher in both LD (2·5%) and BF (2·0%) from pigs on the low-protein diet compared with LD (1·5%) and BF (1·3%) from pigs on the high-protein diet. TG content did not differ between diets in BF but was higher in LD from pigs on low- vis-à-vis high protein diet. A significant correlation was seen in LD between IMF and TG content (r = 0·57; P < 0·001). Fibre type composition did not differ between pigs on the two diets. BF had a higher proportion of type I and IIA fibres and a lower proportion of IIB fibres, compared with LD. TG content in muscle was not correlated with fibre type composition or staining intensity for lipids and oxidative capacity. High staining intensity for lipid in LD was seen in all type I fibres and in some type IIA fibres. Meat quality parameters did not differ between groups except shear force, which was higher in pigs fed the high- vis-à-vis low-protein diet (4·7 and 4·0 kg/cm(2), respectively). Shear force was correlated significantly with TG content (r = -0·42; P < 0·01) and IMF (r = -0·43; P < 0·01) in LD. The results of this study show that lipids are stored mainly in type I fibres and in some type IIA fibres. Intracellular triglycerides account for only a small fraction of IMF. The results indicate that IMF and TG content in muscle fibres may be related to shear force.     

Responses to graded postruminal doses of histidine in dairy cows fed grass silage diets

Five Finnish Ayrshire cows were used in a 4 x 4 Latin square experiment designed to study the effects of graded doses of postruminal His infusion on milk production, arterial concentrations, and mammary uptakes of plasma amino acids (AA) as well as utilization of added His. Grass silage (16.9% CP) was given ad libitum with 8 kg of cereal-based concentrate per day (11.3% CP). Treatments were abomasal or duodenal infusions of 250 g of glucose/d in combination with 0, 2, 4, or 6 g of His/d. Infusions did not affect dry matter intake (mean 18 kg/d). Infusion of His increased milk yield linearly from 27.0 to 28.8 kg/d, protein yield from 861 to 919 g/d and lactose yield from 1345 to 1457 g/d. Milk fat yield and content changed in a cubic manner (1240, 1167, 1296, and 1177 g/d and 4.60, 4.16, 4.60, and 4.09). Infusion of His had no influence on milk protein or lactose concentrations. Arterial Lys and His concentrations increased linearly, but other AA concentrations were unaffected as well as calculated arteriovenous differences and mammary AA uptakes. The extraction of His decreased linearly with an increasing amount of His. The utilization of added His (28%) was not affected by the level of infusion, and mammary AA uptake seemed to be regulated by an inverse relationship between arteriovenous difference of essential AA and calculated mammary plasma flow. This experiment confirmed that His is the first-limiting AA on grass silage-cereal based diets.     

丙烯酰胺和环氧丙酰胺的毒性及大蒜素对其 毒性的保护作用研究进展

丙烯酰胺(acrylamide,AA)是一种重要的食品中内源性污染物,现已被国际癌症机构列为2A类人类可能的致癌物。环氧丙酰胺(glycidamide,GA)是AA重要的体内环氧化代谢产物,GA细胞毒性和遗传毒性远远强于AA。研究表明,大蒜素(allicin)作为大蒜鳞茎中的主要功能成分,对AA和GA引起的组织和细胞氧化损伤具有较强的保护作用。本文主要针对AA和GA的代谢毒性及大蒜素对AA和GA毒性的保护作用的研究进展进行了综述,为大蒜素(或大蒜提取物)在食品加工中作为预防AA和GA毒性的膳食补充剂提供了一定的理论基础。     

Change in the prostaglandin and catecholamine levels in spontaneously hypertensive rats fed diets with different polyunsaturated fatty acid contents

The authors provide the data on the content of prostaglandins and catecholamines in biological fluids (blood and urine) derived in experiments on 28 rats aged 4 months with spontaneous hereditary hypertension given the diets with varying content of polyunsaturated fatty acids during pre- and postnatal periods. Rats fed the diet containing sunflower and linseed oil manifested a significant decrease in arterial blood pressure and activation of prostaglandin and sympathoadrenal systems.     

不同豆浆饮品对普通及高脂饲料饲喂小鼠健康的影响

研究普通日粮和高脂饲料条件下不同豆浆饮品对小鼠健康的影响。采用4种不同豆浆饮品(自磨非转基因豆浆F、自磨转基因豆浆G、两种常见市售豆浆K和M)灌胃C57小鼠,并分别饲喂普通日粮和高脂饲料,10周后处死,测定其体重增长率、肝脏系数和结肠长度等参数,并用生化分析仪测定小鼠血清葡萄糖(Glucose,GLU)、甘油三脂(Triglycerides,TG)、总胆固醇(total cholesterol,CHOL)、高密度脂蛋白胆固醇(High density lipoprotein cholesterol,HDL-C)和低密度脂蛋白胆固醇(Low density lioprotein cholesterol,LDL-C)等指标。用不同豆浆处理人结肠癌细胞HCT-116,检测其对细胞增殖和脂滴积累的影响。结果显示,所有豆浆都不同程度地降低了小鼠血液TG,且市售豆浆M还降低了小鼠血液GLU和CHOL浓度;豆浆处理后结肠癌细胞增殖活性得到明显抑制,但是对油酸诱导的细胞增殖和脂滴积累影响不显著。不同豆浆由于营养及功能活性物质的含量不同,对小鼠血糖、血脂和胆固醇等参数的影响不同,市售豆浆相对自磨豆浆更利于减轻高脂饲料带来的健康副作用。     

Lactation and metabolic responses to graded abomasal doses of methionine and lysine in cows fed grass silage diets

Five rumen-cannulated Finnish Ayrshire cows were used in two 5 x 5 Latin square experiments designed to study the lactation and metabolic responses to increasing doses of DL-Met or L-Lys infused into the abomasum. The cows were fed grass silage ensiled with a formic acid additive for ad libitum intake. A supplement with barley and oats was given at a rate of 9 kg/d (Experiment 1) or 7 kg/d (Experiment 2). The experimental treatments were 0, 10, 20, 30, or 40 g of Met/d (Experiment 1) and 0, 15, 30, 45, or 60 g of Lys/d (Experiment 2). The infusion of Met did not significantly affect feed intake or daily milk yield, but increased milk fat content, ECM yield, and C4 to C14 and C18 to C20 fatty acid production in milk. The infusion of Met caused an increase in arterial plasma Met concentration and a decline in branched-chain amino acids (AA). Mammary gland uptake of Met was not related to plasma AA concentration. The infusion of Lys did not affect feed intake, milk yield, or milk composition, except for increases in milk urea and NPN contents. The infusion of Lys increased plasma Lys, BCAA, EAA, and the EAA to TAA ratio. Uptake of plasma BCAA and NEAA by the mammary gland decreased, which suggests that Lys was used as a substrate for milk NEAA synthesis. These data demonstrate that Met is important in the milk fat synthesis, and Lys is important in mammary gland AA metabolism. However, neither Met nor Lys is the first-limiting AA in the milk protein yield of cows fed a grass silage and cereal diet.     

Amylase addition increases starch ruminal digestion in first-lactation cows fed high and low starch diets

The objective of this study was to evaluate the effect of an exogenous amylase preparation on digestion of low- and high-starch diets in dairy cattle. Rumen and total-tract nutrient digestibility were measured in a 4 × 4 Latin square design with 28-d periods using 4 first-lactation cows cannulated at the rumen and duodenum. Corn silage-based diets had 20 or 30% starch, attained by changing the composition of concentrate, with or without addition of an exogenous amylase preparation. Effects of the enzyme additive were observed on ruminal digestibility but not at the total-tract level. Ruminal digestibility of starch increased from 75% in control to 81% with amylase supplementation. This difference in ruminal starch digestion was compensated postruminally, so that the total-tract digestibility of starch was almost complete and did not differ between treatments. The amylase supplement also increased the true ruminal digestibility of organic matter but did not affect microbial N flow to the duodenum. Amylase supplement reduced the proportion of acetate and butyrate and increased that of propionate, particularly in the high-starch diet, where it tended to increase the concentration of total volatile fatty acids in the rumen. Other effects were a higher amylase activity in the solid-associated microbial community and a tendency for lower numbers of protozoa. In contrast, we observed no changes in intake, production, dry matter and fiber (neutral detergent fiber and acid detergent fiber) digestibility, or ruminal digestion, and no or small changes on selected fibrolytic and amylolytic bacteria and on the microbial community in general. We conclude that the exogenous amylase improved starch digestion in the rumen in first-lactation cows with moderate intake and production levels.     

Effective nitrogen preservation during urine collection from Holstein heifers fed diets with high or low protein content

Six Holstein heifers (body weight = 535-625 kg) fed a total mixed ration containing either high protein (13.4%) or low protein (9.0%) were used to evaluate the effect of 3 urine collection methods (chilled, acidified before collection, or acidified after 6 h of collection) on urinary N preservation. In a 2-period crossover design, 16-d diet adjustment stages preceded five 24-h collections. Urinary catheters were inserted 1 d before the collection periods. Urine collection tubes were configured to split urine to 3 collection containers: 1 acidified with 6 N HCl before collection at a rate calculated to reduce pH to below 2, 1 acidified every 6 h during collection to pH below 2, and 1 located in a large cooler of ice. Collection method did not affect urinary concentration of N or urine urea-N (9.2 ± 0.9 g/L and 6.58 ± 0.9 g/L, respectively) or urinary excretion of N or urea-N (82 ± 3.8 g/d and 59.5 ± 3.8 g/d, respectively). These 3 collection methods are equally effective in preserving N during urine collection, but the “chilled immediately” approach may be useful for studies focused on ammonia emission. Urinary and fecal N excretion were significantly different across collection days; fecal N was more highly variable than urinary N. Intake and apparent N digestibility decreased during the collection week, and excretion of urinary and fecal N increased, particularly on d 5. (Stable rectal temperatures suggested no urinary infections.) Improvements in total collection methodology will support continued progress in the understanding of livestock N utilization and post-excretion changes in manure N.     

Effect of total and rumen undegradable protein on the performance of cows fed low fiber diets.

Twelve multiparous and 18 primiparous Holstein cows were fed a 17.3% CP, 21.0% ADF diet during wk 2 through 6 postpartum. Cows then were assigned from wk 7 through 14 to one of three low fiber (10.7% ADF) dietary treatments containing either 14.4 or 18.7% CP, the latter with or without a soybean meal enhanced with rumen undegradable protein. Treatments had no effect on milk yield or composition in multiparous cows, although milk fat percentage was not depressed in multiparous cows receiving the low fiber diets. The soybean meal diet enhanced with rumen undegradable protein increased yields of milk, 4% FCM, fat, protein, and DMI compared with the 14.4% CP diet in primiparous cows; it also increased yields of 4% FCM and fat versus the 18.7% CP, untreated diet in primiparous cows. Blood urea N concentrations were greater for high CP diets than for the low CP diet in both parity groups. Rumen acetate: propionate ratios were higher for both high CP diets than for the low CP diet in multiparous cows. Soybean meal enhanced with rumen undegradable protein improved yields of milk and its components in primiparous cows fed low fiber diets, even when high protein diets were fed.     

Relationship between residual feed intake and digestibility for lactating Holstein cows fed high and low starch diets

We determined if differences in digestibility among cows explained variation in residual feed intake (RFI) in 4 crossover design experiments. Lactating Holstein cows (n = 109; 120 ± 30 d in milk; mean ± SD) were fed diets high (HS) or low (LS) in starch. The HS diets were 30% (±1.8%) starch and 27% (±1.2%) neutral detergent fiber (NDF); LS diets were 14% (±2.2%) starch and 40% (±5.3%) NDF. Each experiment consisted of two 28-d treatment periods, with apparent total-tract digestibility measured using indigestible NDF as an internal marker during the last 5 d of each period. Individual cow dry matter (DM) intake and milk yield were recorded daily, body weight was measured 3 to 5 times per week, and milk components were analyzed 2 d/wk. Individual DM intake was regressed on milk energy output, metabolic body weight, body energy gain, and fixed effects of parity, experiment, cohort (a group of cows that received treatments in the same sequence) nested within experiment, and diet nested within cohort and experiment, with the residual being RFI. High RFI cows ate more than expected and were deemed less efficient. Residual feed intake correlated negatively with digestibility of starch for both HS (r = ?0.31) and LS (r = ?0.23) diets, and with digestibilities of DM (r = ?0.30) and NDF (r = ?0.23) for LS diets but was not correlated with DM or NDF digestibility for HS diets. For each cohort within an experiment, cows were classified as high RFI (HRFI; >0.5 SD), medium RFI (MRFI; ±0.5 SD), and low RFI (LRFI; <?0.5 SD). Digestibility of DM was similar (~66%) among HRFI and LRFI for HS diets but greater for LRFI when fed LS diets (64 vs. 62%). For LS diets, digestibility of DM could account for up to 31% of the differences among HRFI and LRFI for apparent diet energy density, as determined from individual cow performance, indicating that digestibility explains some of the between-animal differences for the ability to convert gross energy into net energy. Some of the differences in digestibility between HRFI and LRFI were expected because cows with high RFI eat at a greater multiple of maintenance, and greater intake is associated with increased passage rate and digestibility depression. Based on these data, we conclude that a cow’s digestive ability explains none of the variation in RFI for cows eating high starch diets but 9 to 31% of the variation in RFI when cows are fed low starch diets. Perhaps differences in other metabolic processes, such as tissue turnover, heat production, or others related to maintenance, can account for more variation in RFI than digestibility.     

Effects of dietary protein on milk, rumen, and blood parameters in dairy cattle fed low fiber diets

Eighteen multiparous and 9 primiparous Holstein cows were used to determine the effects of a 13 and 23% crude protein concentrate on milk fat depression during early lactation. Beginning on d 22 postpartum, cows were fed a high fiber diet (27% acid detergent fiber) for 3 wk and then switched to a low fiber diet (9 to 10% acid detergent fiber) for 6 wk. Crude protein percentages calculated from dry matter consumption were 13.5 and 17.9% during the high fiber period and 12.7 and 22.3% during the low fiber period. Daily milk and fat yields for both primiparous and multiparous cows were greater for the high protein treatment. The magnitude of decline in milk fat percentage (from high to low fiber) was greater for the low protein treatment, as determined by nonlinear regression. The high protein treatment was more effective in reducing the severity of milk fat depression in primiparous cows than in multiparous cows. Dietary crude protein had no effect on milk protein or solids-not-fat percentages, rumen volatile fatty acid molar proportions, or serum acetate concentration. The mechanism by which the high protein ration minimized the fat depression response to low fiber rations by primiparous cows is unknown.     

Influence of dietary protein and supplemental niacin on lactational performance of cows fed normal and low fiber diets.

Forty-seven cows (24 primiparous) were assigned to one of four normal (20.5%) ADF diets for wk 2 to 5 postpartum. Dietary treatments in a 2 x 2 factorial design were diets of 13.8 versus 18.8% CP and 0 versus 12 g/d of niacin per cow. During wk 6 to 13 postpartum, cows were fed low (11.8%) ADF diets while maintaining CP and niacin treatments. Low CP diets contained solvent-extracted soybean meal; rumen soybean meal with enhanced undegradable protein was used in high CP diets. High CP diets increased milk protein percentage in multiparous cows and yields of milk, 4% FCM, fat, protein, and SNF in primiparous cows during the normal fiber period. High dietary CP also increased yields of 4% FCM, fat, protein, and SNF in primiparous cows fed normal fiber diets. When switched to low fiber diets, primiparous cows fed high CP diets decreased more in 4% FCM and fat yields than those fed low CP. Primiparous cows fed niacin decreased more in 4% FCM than controls. High dietary CP increased DMI in primiparous cows fed normal fiber diets, but those fed low CP diets increased more in DMI when switched to low fiber diets. Supplemental niacin appeared to interact with dietary CP in multiparous cows, increasing blood glucose and decreasing blood beta-hydroxybutyrate and NEFA concentrations with the high CP, normal fiber diet. Increased dietary CP improved yields of milk and milk components in primiparous cows.     

Recombinant bovine somatotropin with lactating cows fed diets differing in energy density

Sixty-four Holstein cows (32 primiparous) were assigned randomly at parturition to one of two diets differing in forage:grain ratio and were further assigned to either control or treatment with recombinant bST. A full lactation study was conducted. Total mixed rations consisted of alfalfa silage, high moisture ear corn, soybean meal, and vitamin and mineral supplements. Percentages of forage in the diet (dry basis) for the high and medium energy diets were wk 1 to 12, 38.2 and 58.2; wk 13 to 26, 48.2 and 68.2; and wk 27 to 44, 68.2 and 88.2. Injection of a saline placebo or 20.6 mg/d per cow of bST started at wk 13 and stopped at wk 43 of lactation. Administration of bST increased 305-d milk yield by 19.9 and 18.3% for multiparous cows fed high and medium grain diets and by 13.0 and 5.9% for primiparous cows fed the same diets. Body weight gain during lactation tended to be lower for cows treated with bST, and body condition scores were significantly lower for those treated with bST and fed the medium energy diets. Daily injection of bST did not change concentrations of glucose or urea in blood or beta-hydroxybutyrate in plasma. Multiparous cows had a transitory increase in plasma FFA concentration immediately after bST treatment started. Milk composition, health, and reproductive parameters observed were not adversely affected by bST administration. Cows fed low energy diets during bST administration in the first lactation did not produce as much milk as controls when compared during the first 10 wk of their second lactation.     

Glucose metabolism in cows fed low- and high-roughage diets.

Six lactating first-calf Holstein cows were used to test the effect of dietary roughage on glucose metabolism. Cows were fed either a low-roughage or high-roughage diet at isocaloric digestible energy intakes in a double changeover design experiment. Mean values (plus or minus standard deviation) for milk yield (kg/day), fat (%), lactose (%), and protein (%) for cows fed low-roughage were 19.0 plus or minus 4.4, 3.11 plus or minus .78, 5.19 plus or minus .27, 3.44 plus or minus .48; values for cows fed high-roughage were 17.5 plus or minus 5.1, 3.99 plus or minus .58, 4.94 plus or minus .25, and 2.78 plus or minus .33. One hour post-feeding on the 20th day of each period 2 mCi of tritiated glucose were administered to each cow by single injection to measure glucose kinetics. Mean values (plus or minus standard deviation) for plasma concentration (mg/100 ml) pool size (mg/kg), half-time (min), and utilization rate (mg/kg--75 per min) of glucose, and plasma insulin concentration (muU/ml) for cows fed low-roughage were 63.1 plus or minus 3.9, 17.9 plus or minus 3.4, 30.4 plus or minus 5.2, 8.55 plus or minus 2.44, and 22.0 plus or minus 3.9; for cows fed high-roughage values were 54.9 plus or minus 2.2, 114.5 plus or minus 17.2, 40.0 plus or minus 2.2, 4.06 plus or minus .38, and 16.2 plus or minus 2.4. A glucose load was administered intravenously to each cow on the last day of each period. Glucose half-times and mean plasma insulin following the clearance test were not affected by diet. Compared to high-roughage, low-roughage diets greatly affect metabolism in lactating cows when isocaloric intakes of each are fed. Fat depression, however, may or may not occur simultaneously.     

Production of dairy cows fed distillers dried grains with solubles in low- and high-forage diets

The objective of the study was to investigate the effects of dietary forage and distillers dried grains with solubles (DDGS) concentration on the performance of lactating dairy cows. Twelve Holstein cows were blocked by parity and milk production and assigned to replicated 4 × 4 Latin squares with a 2 × 2 factorial arrangement of treatments. Diets were formulated to contain low forage [LF; 17% forage neutral detergent fiber (NDF)] or high forage (HF; 24.5% forage NDF) and DDGS at 0 or 18% of diet dry matter. The forage portion of the diet consisted of 80% corn silage and 20% alfalfa hay (dry matter basis). A portion of the ground corn and all of the expeller soybean meal and extruded soybeans from 0% DDGS diets were replaced with DDGS to formulate 18% DDGS diets. Overall, we found no interactions of forage × DDGS concentrations for any of the production measures. We observed no effect of diet on dry matter intake. Milk yield was greater when cows were fed LF diets compared with HF diets (43.3 vs. 41.5 kg/d). Milk fat concentration (3.03 vs. 3.38%) was lower for cows fed LF diets compared with HF diets, whereas protein concentration (3.11 vs. 2.98%) and yield (1.34 vs. 1.24 kg/d) were greater for cows fed LF diets compared with HF diets. Yields of fat, total solids, energy-corrected milk, and feed efficiency were not affected by diets. Cows partitioned equally for milk, maintenance, and body reserves. Replacing starch from ground corn and protein from soybean feeds with DDGS at either 17 or 24.5% of forage NDF concentration in the diet was cost-effective and did not affect the production performance of lactating dairy cows.     

Lead and zinc contents of food and diets in the Netherlands

Summary The lead and zinc contents of foodstuffs sampled in Dutch retail shops were determined by means of atomic absorption spectrophotometry. Extremely high contents of these metals were not found. The daily intakes through food and beverages calculated on the basis ofper caput consumption data for the Netherlands were 105 microgrammes of lead and 16.8 milligrammes of zinc. Calculations based on diet studies of selected population groups (farmers, inhabitants of a city, families in a northern province and students) provided intakes of lead and zinc of the same order, namely 63 to 161 microgrammes of lead and 15.4 to 24.6 milligrammes of zinc per person per day. The intakes by toddlers were assessed at 42 g and 8.0 mg respectively. These results are compared with those calculated for three other countries. A toxicological evaluation of these levels is given.

---

Blei- und Zinkgehalt der Lebensmittel und der Kost in den Niederlanden

Zusammenfassung Die Blei- und Zinkgehalte von Lebensmitteln aus niederländischen Läden wurden durch Atomabsorptionsspektrophotometrie ermittelt. Außerordentlich hohe Gehalte wurden nicht gefunden. Berechnungen auf Grund der täglichen Aufnahme durch Nahrung und Getränke (aus Produktions-, Import- und Exportwerten ermittelt) ergaben pro Kopf der Bevölkerung 105 g Blei und 16,8 mg Zink. Weitere Berechnungen stützten sich auf den täglichen Lebensmittelverbrauch von Sondergruppen (Bauern, Stadtbewohnern, Familien in einer nördlichen Provinz und Studenten); sie ergaben Blei- und Zinkaufnahmen in ähnlichen Mengen, nämlich 63 bis 161 g Blei und 15,4 bis 24,6 mg Zink pro Tag. Für die Aufnahme durch Kleinkinder wurden 42 g Blei und 8,0 mg Zink pro Tag berechnet. Die Ergebnisse wurden mit Daten aus drei anderen Ländern verglichen. Eine toxikologische Beurteilung der Befunde wurde versucht.

---

---

Authors wish to thank Mr. P. W. J. de Graaf and Mr. W. van der Schee for their zinc and lead determinations.     

Carcass fat partitioning and meat quality of Alentejana and Barrosã young bulls fed high or low maize silage diets

This study assessed the effect of breed and diet on carcass composition, particularly fat partitioning, and meat quality in young bulls. An experiment with forty young bulls from two phylogenetically distant Portuguese bovine breeds, Alentejana and Barrosã, fed two diets with different maize silage to concentrate ratios, but isoenergetic and isonitrogenous, was carried out until the animals reached 18 months of age. In the longissimus lumborum muscle, Barrosã bulls fed the low silage diet had the highest intramuscular fat (IMF) content. Bulls fed the low silage diet also had the highest IMF content in the semitendinosus muscle. Diet determined the proportions of total visceral fat and individual fat depots. Under these experimental conditions, it was shown that the genetic background is a major determinant of carcass composition and meat quality, and that the dietary differences studied had limited effect on carcass composition.     

硫辛酸对高脂日粮小鼠肠道氧化还原状态与微生物菌群的影响

目的:研究高脂饲粮条件下,添加不同剂量硫辛酸(LA)对小鼠肠道自由基及微生物菌群的影响。方法:将40只昆明种雄性小鼠随机分成4组,设置正常组、高脂组(16·1%猪油),高脂饲粮中分别添加0·05%和0·1%LA每组,饲喂六周,观察对小鼠血浆组织自由基、抗氧化能力及肠道乳杆菌、大肠杆菌数量的影响。结果:高脂饲料可导致小鼠氧化应激,显著升高血浆、肠道组织自由基水平,降低总抗氧化能力,并降低肠道内乳杆菌数量,增加大肠杆菌数量(P0·05);而高脂添加LA能显著降低小鼠血浆和肠道自由基水平及MDA含量(P0·05),提高肠组织SOD活性和肠道与血浆总抗氧化能力(P0·05),达到接近正常组水平。高脂日粮添加LA使肠道乳杆菌数量显著高于高脂组(P0·05),大肠杆菌数量显著降低(P0·05),并与LA添加量呈显著量效关系(P0·05)。结论:小鼠消化道氧化应激引起肠道微生物区系的紊乱,调整肠道氧化还原状态能够使微生物区系恢复正常。     

Diets rich in starch increase the posthepatic availability of amino acids in dairy cows fed diets at low and normal protein levels

Five mid-lactation multicatheterized Jersey cows were used in a 4 × 4 Latin square design to investigate whether the increase in milk N yield associated with diets rich in starch versus fiber could originate from changes in the splanchnic AA metabolism and if these changes depended upon the dietary crude protein (CP) content. Four isoenergetic diets were formulated to provide 2 different carbohydrate compositions [diets rich in starch (350 g of starch and 310 g of neutral detergent fiber/kg of dry matter) versus rich in fiber (45 g of starch and 460 g of neutral detergent fiber/kg of dry matter)] crossed by 2 different CP contents (12.0 vs. 16.5% CP). At the end of each treatment period, 6 hourly blood samples were collected from the portal and hepatic veins as well as the mesenteric artery to determine net nutrient fluxes across the portal-drained viscera (PDV), liver, and total splanchnic tissues. Dry matter and calculated energy intake as well as total absorbed energy were similar across treatments. However, the net portal appearance (NPA) of acetate, total volatile fatty acids, and β-hydroxybutyrate were higher with diets rich in fiber versus starch, whereas that of oxygen, glucose, butyrate, and insulin were lower. Concomitant to these changes, the percentage of N intake recovered as total AA (TAA) in the portal vein was lower for diets rich in fiber versus starch (42.3 vs. 51.4%, respectively), without, however, any difference observed in the NPA of the main AA used as energy fuels by the PDV (Glu, Gln, and Asp). Despite a higher NPA of TAA with starch versus fiber diets, no differences in the net hepatic flux of TAA, essential and nonessential AA were observed, resulting in a higher (+22%) net splanchnic release of AA and, hence, a greater (+7%) milk N yield. The net hepatic flux and hepatic fractional removal of none of the individual AA was affected as the main carbohydrate changed from fiber to starch, except for Gly and Lys, which were higher for the latter. After correcting for differences in NPA of TAA, the net hepatic uptake of TAA tended to be lower with starch versus fiber diets. The higher transfer of N from feed to milk with diets rich in starch is not the consequence of a direct sparing AA effect of glucogenic diets but rather the result of lower energy requirements by the PDV along with a higher microbial N flow to the duodenum. A better AA use by peripheral tissues with starch versus fiber diets was also hypothesized but more studies are warranted to clarify this issue.