Amelioration of selenium toxicity by arsenicals and cysteine

Young chicks exhibited a 61% reduction in weight gain when a corn-soybean meal diet was supplemented with 15 mg/kg Se provided as Na selenite. The same level of Se provided as selenomethionine depressed weight gain by 32%. Supplementing the high selenite diet with isoarsenous (14 mg/kg As) additions of As2O5, As2O3, phenylarsonic acid, phenylarsine oxide and roxarsone ameliorated the Se-induced growth depression: As2O5 almost totally restored growth rate; As2O3, phenylarsonic acid and phenylarsine oxide gave intermediate responses; and roxarsone gave only a small ameliorative growth response. Arsanilic acid was without effect in stimulating growth rate of selenite-intoxicated chicks. Dietary addition of .4% L-cysteine produced a growth response in selenite intoxicated chicks that was somewhat greater than that obtained with roxarsone; administering both roxarsone and cysteine corrected growth better than either compound given singly. Both roxarsone and As2O5 also effectively ameliorated the Se-toxicity growth depression caused by selenomethionine (15 mg Se/kg) supplementation, but cysteine showed no efficacy against morbidity caused by this form of Se. Liver Se concentration was elevated 10-fold by selenite and 25-fold by selenomethionine supplementation. The arsenic compounds had varying effects on liver Se, whereas cysteine tended to increase Se concentration. These findings suggest that both inorganic and organic arsenicals as well as cysteine ameliorate selenium toxicity by different mechanisms.     

Reduction of liver copper concentration by the organic arsenical, 3-nitro-4-hydroxyphenylarsonic acid

The interaction between 3-nitro-4-hydroxyphenylarsonic acid (roxarsone) and Cu was studied in a series of experiments with crossbred, broiler-type chicks. A fully fortified corn-soybean meal diet was fed in all assays. While roxarsone caused a marked reduction in liver Cu concentration, arsanilic acid (4-aminophenylarsonic acid), As2O3 and As2O5 were without effect. When structural analogs of roxarsone were studied, it was found that o-nitrophenol and 3-nitro-4-hydroxybenzoic acid also had no effect on liver Cu concentration in birds fed a high level of Cu. However, liver Co concentration was reduced by the addition of either o-nitrophenol or roxarsone to the diets of birds fed a high level of Co. It was concluded that arsenic per se had no effect on liver Cu accumulation or depletion, but that a chelate was probably formed between Cu or Co and the nitroso and hydroxyl groups of the ring portion of roxarsone. In addition to the reduction in liver Cu deposition, concentrations of Cu in the bile, brain, heart and pancreas of chicks were reduced by the addition of roxarsone to a high-Cu diet. Neither dietary nor intraperitoneally (ip) injected roxarsone had an effect on liver Cu concentration when Cu was injected ip. Therefore, both roxarsone and Cu had to be present in the diet for the liver Cu-lowering effect of roxarsone to be exerted. A further experiment was conducted with growing rats to determine the effect of roxarsone on Cu balance. Feeding roxarsone elevated Cu excretion in the urine but had no effect on Cu excretion in the feces.     

Toxic effects of supplemental copper and roxarsone when fed alone or in combination to young pigs

Three experiments were conducted to investigate the roxarsone (3-nitro-4-hydroxyphenylarsonic acid) X copper (Cu) interaction in weanling pigs. Supplemental roxarsone at 400 mg/kg diet decreased rate and efficiency of weight gain and caused visible neurological signs of toxicosis. Copper addition (CuSO4 X 5H2O) at a level of 650 mg Cu/kg diet likewise decreased weight gain and feed efficiency, and it also increased hepatic Cu deposition. The combination of these growth-depressing dosages of roxarsone and Cu resulted in a far greater reduction in gain and efficiency of feed utilization than was the case when either compound was fed alone. A growth-promoting dosage of Cu (250 mg/kg) increased weight gain by 32% in one experiment but showed no efficacy in alleviating the growth-depression resulting from feeding 400 mg/kg roxarsone. A roxarsone dosage of 100 mg/kg increased gain and feed efficiency. Surprisingly, the decreased weight gain in pigs fed 650 mg/kg Cu was ameliorated by feeding 100 mg/kg roxarsone concomitantly. This level of roxarsone also reduced liver Cu concentration substantially. It thus appears that the nature of the roxarsone X Cu interaction is dependent on the dose of each compound administered. Moreover, low-dose roxarsone administration appears to ameliorate Cu toxicity, but low-dose Cu feeding does not show efficacy against roxarsone toxicity.     

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) poisoning in pigs

Young pigs, six to ten weeks of age, from two unrelated swine operations were fed a grower ration obtained from a common commercial supplier. Following ingestion of the feed for approximately two weeks, pigs in both groups developed neurological disturbances characterized by blindness, ataxia, incoordination, muscle tremors, posterior paralysis, and quadriplegia. Vocalization described as “screaming” was also observed in several animals. Necropsy findings and tissue arsenic concentrations were consistent with a diagnosis of phenylarsonic acid poisoning. The liver and kidney contained an average arsenic content of 2.9 and 1.8 mg/kg (wet weight), respectively. The feed contained 38 mg of arsenic/kg corresponding to 133 mg roxarsone (3-nitro-4-hydroxyphenylarsonic acid)/kg. This level of roxarsone is approximately three to five times higher than the levels recommended for swine rations. The feed company had placed roxarsone in the ration at levels recommended for the less toxic arsanilic acid. It was assumed that the two organic arsenicals could be added to the rations interchangeably at the same level of formulation. The present investigation indicated that roxarsone is more toxic than arsanilic acid and the margin of safety in swine rations is low.     

Effect of roxarsone inclusion in the diet on the performance and hepatic lipid metabolism of laying Tsaiya duck

1. The aim of this study was to examine the effects of roxarsone (3-nitro-4-hydroxyphenylarsonic acid) inclusion in the diet on the performance, liver function and lipid metabolism in the liver of laying Brown Tsaiya ducks. 2. Sixty 36-week-old laying ducks were selected and allocated at random into 4 dietary treatments with 3 replications for each treatment. Feeding was for 7 weeks with 3 weeks of experimental diets followed by a 4 week withdrawal period. The experimental diets were supplemented with 0, 50, 100 and 300 mg/kg roxarsone, respectively 3. Dietary inclusion of 50 or 100 mg/kg roxarsone did not significantly promote performance. Inclusion of 300 mg/kg significantly depressed (P<0.05) performance, liver weight and content, serum triacylglycerol (TG), serum nonesterified fatty acid (NEFA) and increased (P<0.05) cholesterol, creatine kinase (CK) and aspartate aminotransferase (AST) in the serum at the end of 3 weeks on the experimental diet. 4. Laying characteristics returned to normal 4 weeks after withdrawal of roxarsone. The liver weight, fat and TG in the liver and serum concentrations of TG, NEFA, high density lipoprotein (HDL) and AST increased significantly (P<0.05), while the level of very low density lipoprotein (VLDL) decreased (P<0.05) at the end of the withdrawal period. More prominent vacuolised hepatic fatty cells were observed in laying ducks treated with 300 mg/kg of roxarsone.     

猪粪中洛克沙胂的HPLC检测及排泄规律

在建立猪粪中洛克沙胂HPLC检测方法基础上,选用24头育肥猪,分别混饲给予0、25、50、100 mg/kg洛克沙胂,混饲给药后不同时间采集粪样,以高效液相色谱法测定其中洛克沙胂质量浓度,了解洛克沙胂混饲给药后在猪体内的排泄情况,然后从江苏和山东省15个使用洛克沙胂的集约化猪场采集150头猪的粪样,调查猪粪样中的洛克沙胂含量。结果表明,所建立的猪粪中洛克沙胂HPLC检测方法的平均回收率为82.09%~84.03%,变异系数为2.92%~5.45%,检测限为0.05 mg/kg,定量限为0.1 mg/kg;以不同剂量混饲给药后,洛克沙胂在粪中排泄量在36~48 h达峰,峰质量浓度分别为12.31、22.52、34.78 mg/kg,猪粪中检测不到洛克沙胂的时间分别为72、108、132 h;所调查150个粪样中洛克沙胂平均质量浓度为23.13 mg/kg。     

洛克沙胂对猪生产性能和血液指标的影响

本研究通过断奶仔猪、生长猪和肥育猪3个试验研究了日粮添加洛克沙胂对猪生产性能及血液指标的影响。试验分别选择96头杜×长×大三元杂交断奶仔猪(8.29±0.99)kg、生长猪(32.68±3.43)kg和肥育猪(62.74±8.89)kg,随机分为4个处理,每个处理6个重复,每个重复4头猪,公母各半。处理1为对照组,日粮中不添加洛克沙胂,处理2、3和4分别在日粮中添加50、100 mg/kg和150 mg/kg洛克沙胂。基础日粮为玉米-豆粕型,各处理日粮营养水平均为等能量、等蛋白。结果表明:日粮中添加洛克沙胂能显著提高断奶仔猪与生长猪日增重和饲料转化效率(P<0.05),减少仔猪腹泻率(P<0.01)。但对肥育猪增重效果不明显(P>0.05);日粮中添加洛克沙胂使动物血红蛋白、肌酐和谷草转氨酶含量升高,白蛋白含量降低(P<0.05)。表明洛克沙胂对猪具有一定的促生长效果,可增加动物血液运氧能力,但同时有可能对动物肝脏、肾脏造成一定损伤。     

Effect of roxarsone and canthaxanthin on broiler pigmentation

Broiler chicks were fed on a commercial‐type ration containing 20 g oxy‐carotenoids/ton for 5 weeks, half receiving 0.005% roxarsone. All birds were then fed on finisher rations containing a moderate (20 g/ton) to high level (40 g/ton) of oxycarotenoids from food ingredients alone and in combination with 2 and 4 g canthaxanthin/ton for 26 d. The birds given roxarsone in the starter ration also received 0.005% roxarsone in the finisher ration together with the above‐listed oxycarotenoid supplements. Roxarsone was withdrawn from the ration 5 d prior to termination of the study to simulate commercial requirements.

The continuous feeding of 0.005% roxarsone had no effect on weight gain, food conversion or pigmentation as assessed by visual shank scores, using the Roche Yolk Color Fan, and colorimetric assay of total carotenoid concentrations in plasma, toe‐web skin and shank skin. Shank visual scores reflected the increased levels of oxycarotenoids derived from food ingredients alone and the effect of supplemental canthaxanthin. These data show that canthaxanthin is an effective pigmenter adjuvant, when added at 2 to 4 g/ton to rations containing 20 to 40 g of oxy‐carotenoids/ton from food ingredient sources. Concurrent feeding of 0.005% roxarsone, while having no positive effect on pigmentation, had no adverse effect on the pigmenting properties of canthaxanthin.     

Effect of glutamic acid content of the diet on the catabolic rate of isotope-labeled glutamic acid in rats. 3. Determination of 14CO2 and 15N excretion following intragastric infusion of 14C- and 15N-glutamic acid

Male rats (body weight 100 g) received during a 8 days experimental feeding period diets with different contents in glutamic acid. The daily feed intake was restricted to the energy maintenance level of 460 kJ/kg0.75. The diet contained a mixture of L-amino acids corresponding to the pattern of egg protein except glutamic acid. Glutamic acid was added successively at 10 levels (0 to 14,8% of dry matter) and the resulting diets were fed to groups of 4 animals each. At the end of the experimental feeding period 14C- and 15N-labelled glutamic acid were applied by intragastric infusion. CO2- and 14CO2-excretion was measured during the following 4 hours and the urinary N- and 15N-excretion during the following 24 hours. The CO2-excretion decreased from 53 to 44 mmol CO2/100 g body weight with increasing levels of dietary glutamic acid. This change seems to result from the increasing proportion of amino acids as an energetic fuel. While the amount of oxidized glutamic acid increased with increasing supplements of glutamic acid the relative 14CO2-excretion decreased from 57 to 48% of the applied radioactivity. The urinary 15N-excretion during 24 hours was 31% of the given amount of 15N if no glutamic acid was included in the diet. This proportion increased successively up to 52% in the case of the highest supply of glutamic acid. Because the total N-excretion increased at the same extent as the 15N-excretion a complete mixing of the NH2-groups resulting from glutamic acid due to desamination with the ammonia pool was assumed. No correlation between glutamic acid content of the diet and specific radioactivity of CO2 or atom-% 15N excess of urinary N was observed.     

Feed physical form and formic acid addition to the feed affect the gastrointestinal ecology and growth performance of growing pigs

The effect of feeding a coarsely ground meal (COARSE) and a finely ground pelleted diet with 1.8% (as-fed basis) added formic acid (ACID) was compared with feeding a standard finely ground pelleted diet (STD) on the gastrointestinal ecology of growing pigs at different intervals after feeding. One hundred five castrated male growing-finishing pigs (initial BW 27 kg) were used. At a BW of 63 kg, 60 pigs were killed 0.5, 2.5, 4.5, 6.5, and 8.5 h after feeding, and samples from the gastrointestinal tract (GIT) were obtained. The remaining 45 pigs were kept on the experimental diets to a BW of 99 kg. Feeding the three diets resulted in a similar pattern of gastric pH with time, (i.e., highest pH values 0.5 h after feeding and decreasing values at the following sampling times, to reach a value of 2.12 at 8.5 h after feeding). The pH of the gastric digesta of pigs fed the ACID diet was below 4 at all sampling times, whereas the digesta from the other two dietary groups had values above pH 4 at the first sampling times. Feeding the ACID diet decreased the counts of total anaerobes in the proximal GIT (P < or = 0.007), and of lactic acid bacteria (P < or = 0.001), enterobacteria (P < or = 0.02), and yeasts (P < or = 0.01) along the GIT compared with feeding the other two diets. Feeding the COARSE diet stimulated the growth of total anaerobes and lactic acid bacteria in the stomach and distal small intestine increased the microbial diversity mainly in the stomach (P = 0.001), compared with feeding the other two diets (P < or = 0.09), and decreased the number of enterobacteria in the cecum compared with the STD diet (P = 0.03), with the same tendency in the mid-colon (P = 0.07). The concentration of lactic acid in the stomach was highest in the pigs fed the COARSE diet compared with the other two groups (P < 0.05). The concentration of formic acid was highest in the stomach and all segments of the small intestine of the pigs fed the ACID diet compared with those fed the STD and COARSE diets (P < 0.05). The results from this study suggest that feeding a coarsely ground diet and a finely ground diet with added formic acid affect the gastrointestinal ecology of pigs mainly by changing the environment in the proximal GIT. The presence of organic acids in the proximal GIT is a crucial factor contributing to the decrease in the number of enterobacteria along the GIT. The time after feeding at which samples are taken to measure characteristics describing the gastrointestinal ecology affects the results from the stomach and small intestine.     

Production and carcase traits in broiler chickens given diets supplemented with inorganic trivalent chromium and an organic acid blend

1. The study was conducted to ascertain the effects of supplemental organic acids and chromium (Cr) on production and carcase traits of broiler chickens. 2. A total of 120 1-d-old broiler chicks were divided into 4 treatment groups in a 2 x 2 factorial design (each treatment group contained 6 replicates with 5 birds per replicate). 3. The diets were supplemented with an organic acid blend containing ortho-phosphoric, formic and propionic acid and calcium propionate (1 g/kg diet) and inorganic trivalent chromium (Cr(3+)) as chromic chloride hexahydrate (0.5 mg/kg diet) either independently or together as a combination for 35 d. 4. Individual supplementation of organic acids and Cr(3+) and their combination significantly improved the food conversion ratio, hot and dressed carcase weight and weight of the wholesale cuts compared to the control group of birds. 5. Organic acids, either independently or along with Cr(3+), increased total accretion of ash in carcase. Protein accretion was improved by dietary Cr(3+) and organic acid supplementation compared to the control group and a further improvement in this regard was observed when Cr(3+) and organic acid were supplemented together. Across the treatment groups meat fat content and fat accretion were lower in birds receiving dietary Cr(3+) supplementation. 6. Circulatory Cr(3+) and meat Cr(3+) concentration increased compared to the other treatment groups when Cr(3+) was supplemented to the birds. 7. It was concluded that, instead of individual supplementation, a combination of Cr(3+) and organic acids may improve the production and carcase traits of broilers more effectively presumably because of an additive effect.     

The effects of frequency of feeding on some quantitative aspects of digestion in the rumens of growing steers

Three steers with simple rumen and abomasal cannulas were given ground and pelleted diets containing predominantly dried grass meal (DG) or rolled barley (RB). Diets were given at frequencies of two or eight feeds/d in a simple changeover design. Chromic oxide and polyethylene glycol were given as flow markers and flows (g/24 h) of organic matter (OM), nitrogenous and carbohydrate compounds were calculated. Ribonucleic acid and 35S were used as microbial markers and diaminopimelic acid (DAP) as a bacterial marker. Frequency of feeding had no significant effect on mean rumen pH, ammonia levels or liquid outflow rates with either diet. Rumen volume was decreased and abomasal digesta flow increased on Diet DG with more feeds but these parameters were unaffected with Diet RB. Increased feeding frequency with both feeds resulted in increased numbers of protozoa. There were no significant effects of feeding frequency of Diet DG on the abomasal flows of any of the nitrogenous constituents measured. However, there was a significant increase in microbial-N flow from 33 to 43 g/d with more frequent feeding of diet RB which was not reflected in bacterial-N flow as measured by DAP. The apparent digestion of OM in the rumen, expressed as g/g intake with diet DG was 0.41 and 0.31 for two feeds and eight feeds/d respectively. Corresponding values for diet RB were 0.56 and 0.63 respectively. The reduction in OM digestion with frequent feeding of diet DG was reflected in similarly reduced rumen digestibilities of all dietary carbohydrate components whereas the increase in OM digestion with diet RB was reflected only by the component sugars of the dietary fibre. The efficiencies of microbial protein synthesis (expressed as gMN/kg ADOM) increased from 36 to 46 when the feeding frequency of diet DG was increased from two to eight times/d. No significant effect of frequency of feeding was found for diet RB. Mouth to abomasum degradation of feed-N (expressed as g/g intake) of 0.64 was unaffected by the number of feeds of diet DG but was significantly increased from 0.55 to 0.82 when eight rather than two feeds/d of diet RB were given.     

肉用仔鸡日粮中添加蛋氨酸铜、锌和锰对粪便微量元素排放的研究

为了比较肉用仔鸡日粮中添加不同有机微量元素后粪便中铜、锰、锌、排放的影响,试验选择1日龄AA肉仔鸡,分为7个处理,对照组添加无机硫酸盐（锌50mg/kg;铜10mg/kg;锰50 mg/kg）,试验组分别用Mintrex-Cu替代5 mg/kg或全部替代硫酸铜;以Min-trex-Zn代替20 mg/kg硫酸锌,以Mintrex-Mn代替20 mg/kg硫酸锰,或在对照组基础上添加20mg/kg的Mintrex-Mn或Mintrex-Zn。42日龄时,采用全收粪法收集粪样72h,用原子吸收分光光度计测定粪样中铜、锰、锌的含量。结果表明：Mintrex-Cu代替50%或100%硫酸铜,对粪便中铜、锌和锰的排泄量没有显著影响（P〉0.05）,Mintrex-Zn/Mn替代40%无机锌、锰对锌、锰排泄量没有显著影响（P〉0.05）。在基础日粮中额外添加20mg/kgMintrex-Zn/Mn显著提高了粪便中锌、锰的排泄量（P〈0.05）,但添加20mg/kgMintrex-Mn降低铜排泄量20%以上（P〈0.05）。研究说明,在基础日粮微量元素水平低于需要量的情况下,采用有机微量元素替代无机微量元素对粪便中微量元素排泄量的影响很小,额外添加有机微量元素则提高粪便微量元素的排泄。     

Evaluation of amino acids, B vitamins and butylated hydroxyanisole as protective agents against pyrrolizidine alkaloid toxicity in rats

Supplementation of the diets of rats with branched chain amino acids (BCAA: leucine, isoleucine, valine) did not alter their susceptibility to chronic poisoning by tansy ragwort (Senecio jacobaea), which contains hepatotoxic pyrrolizidine alkaloids (PA). Phenobarbital in the diet, which alters liver microsomal enzyme activity, also did not alter susceptibility to PA poisoning. A combination of butylated hydroxyanisole (BHA), cysteine and BCAA did increase (P less than .05) survival time of rats fed tansy ragwort. Dietary BHA and cysteine increased the survival time of rats injected with the PA monocrotaline, with evidence that addition of vitamin B12 and folic acid improved the effectiveness of this treatment. In a chronic feeding trial with tansy ragwort, a combination of BHA and cysteine increased (P less than .05) the survival times of rats, showing protective activity against PA poisoning. A mixture of B-complex vitamins, or vitamin B12-folic acid, was not effective in improving the response.     

Clinical and biochemical alterations in calves with nutritionally induced polioencephalomalacia

Polioencephalomalacia (PEM) was induced in calves by feeding a semipurified, low-roughage diet of variable copper and molybdenum composition. Two formulations resulting in Cu-insufficient and Cu-sufficient forms of the diet were fed (n = 10 and 4 calves, respectively); both diets induced PEM. Clinical signs of disease developed as early as 15 days after transition to the experimental diets and included impaired vision, decreased response to external stimuli, and abnormal gait. Grossly evident cerebrocortical lesions consisted of laminar areas of cavitation and/or autofluorescence seen under UV illumination. Hepatic Cu concentration was decreased in calves fed the Cu-insufficient diet, but not below normal range. During the course of feeding either diet, rumen pH decreased, rumen volatile fatty acid concentrations increased, rumen and blood lactic acid concentrations increased, and rumen and plasma thiamine concentrations increased. The thiamine pyrophosphate effect on erythrocyte transketolase activity was unaltered in calves of either diet group. This nutritionally induced form of PEM does not appear to be related to Cu deficiency or reduction in plasma or rumen thiamine concentration.     

Changes in gastric contents in pigs fed a finely ground and pelleted or coarsely ground meal diet.

The objective was to characterize the change in stomach contents in relation to time after feeding between pigs consuming a restricted amount of a finely ground and pelleted (FGP) or coarsely ground meal (CGM) diet. Particular interest was placed on the concentration of organic acids and ammonia, the products of microbial fermentation. Thirty barrows were ranked by weight and assigned to a postfeeding time of 2, 4, 6, 8, or 12 h and either the FGP or CGM diet. Initiation and termination of the experiment were staggered over a 2-wk period. The treatment period was 42 d. Percentage of dry matter was higher (P<.01) in the stomach contents of pigs on the CGM diet. Concentrations of pepsin and protein were higher (P<.05) and ammonia tended to be higher (P = .10) in the proximal stomach of pigs fed the FGP diet. In contrast, concentrations of acetate and L-lactate were higher (P<.05) in the proximal stomach of pigs fed the CGM diet. All pigs on the CGM diet had stomachs that graded as normal on visual inspection. There was variable damage to the stomachs of pigs on the FGP diet. Measurement of chromium concentration in the stomach after an oral dose of Cr-EDTA clearly demonstrated the mixing that occurs between the proximal and distal stomach by 2 h after feeding in pigs consuming the FGP diet, whereas a gradient was maintained in pigs consuming the CGM diet. Thus, components normally secreted in the distal stomach return to the proximal stomach. These data show that components secreted in the distal region, such as acid and pepsin, may play a role in initiating damage to the stratified squamous mucosa. High concentrations of organic acids in the stomach of pigs on the CGM diet were not associated with damage to the stratified squamous mucosa in the esophageal region.     

A randomized controlled trial to evaluate the effects of dietary fibre from distillers grains on enterohemorrhagic Escherichia coli detection from the rectoanal mucosa and hides of feedlot steers

Feeding high levels (≥40% dry matter) of distillers grains may increase the risk for cattle to carry enterohemorrhagic Escherichia coli (EHEC) O157. The mechanism for the increased risk is not known nor whether non‐O157 EHEC are similarly affected. Our objective was to test whether the fibre content or other components of modified distillers grains plus solubles (MDGS) affects the probability for cattle to carry EHEC serogroups of public health importance. A 2 × 2 plus 1 factorial treatment arrangement within a randomized block design was utilized. Within each of four blocks, 25 feedlot pens (n = 8 steers/pen) were assigned randomly to (i) corn‐based control diet; (ii) 20% dry matter (DM) MDGS; (iii) 40% DM MDGS; (iv) corn bran added to corn‐based diet to match fibre of 20% MDGS or (v) 40% MDGS. Rectoanal mucosa swabs (RAMS) were collected on day (d)0, d35, d70 and d105; hide swabs were collected on the last feeding day. Samples were tested for EHEC by a molecular screening assay. The effects of fibre source and fibre level on EHEC carriage were tested using multilevel logistic regression (generalized linear mixed models; α = 0.05). EHEC O45 RAMS detection was associated with fibre level, source and sampling day. EHEC O103 RAMS detection increased by feeding 40% MDGS but not the corresponding corn bran diet. Hide contamination by EHEC O45 or O103 was less likely in cattle fed MDGS compared to corn bran diets. EHEC O111 RAMS detection decreased by feeding 40% MDGS but not by feeding the corresponding corn bran diet. Detection of EHEC O157 or O145 was not associated with dietary factors. Feeding 40% MDGS increased the probability for carriage of some EHEC serogroups but decreased probability of others, which indicated that EHEC serogroups have different risk factors associated with feeding MDGS and little association with dietary fibre.     

The effect of feeding sulla (Hedysarum coronarium) or lucerne (Medicago sativa) on lamb parasite burdens and development of immunity to gastrointestinal nematodes

Two experiments investigated the efficacy of the legume Hedysarum coronarium (sulla), which contains condensed tannins (CTs), for reducing gastrointestinal nematode infections relative to lucerne. Experiment 1 was aimed to show whether the lower faecal egg count (FEC) and larval establishment previously reported in lambs grazing sulla were due to direct effects of the forage on Ostertagia circumcincta and Trichostrongylus colubriformis or were mediated through an enhanced immune response. Experiment 2 evaluated the impact of feeding sulla relative to feeding lucerne (Medicago sativa), before, at, or after larval challenge on subsequent FECs and nematode burdens. In experiment 1, 64 Romney lambs were fed either freshly cut lucerne or sulla (32 lambs per herbage) for the duration of the trial. Within each herbage there were four treatment groups (n=8 per group). Initial levels of immunity were assessed in uninfected (UN) lambs which were maintained parasite-free until challenged with 15,000 O. circumcincta and 15,000 T. colubriformis larvae on day 63, and slaughtered on day 81. The other three treatment groups were trickle-infected with each of 5000 O. circumcincta and 5000 T. colubriformis larvae three times per week from day 1 to 35. Non-steroid infected (CONTROL) and steroid-treated (STER) groups were treated with anthelmintic on day 49 and challenged with 15,000 O. circumcincta and 15,000 T. colubriformis on day 63 and slaughtered on day 81. The STER lambs were given dexamethasone trimethylacetate from day 49 to 81 to determine effects of immunity on parasite infection. From day 35 an establishment group (EST) on each herbage was fed a common pelleted lucerne diet and slaughtered on day 56 to determine nematode establishment during trickle-infection. Diet did not affect FECs but feeding lucerne increased (P<0.05) numbers of T. colubriformis in CONTROL lambs compared to those fed sulla. O. circumcincta numbers were lower (P<0.05) in UN lambs fed sulla than lucerne. The sulla diet was associated with higher (P<0.05) antibody titres against secretory-excretory antigens to adult O. circumcincta and to adult and larval T. colubriformis, so there appeared to be some immunogenic response to the sulla diet but effects upon T. colubriformis numbers were not significant. The second experiment involved 48 Romney lambs grazing conventional pasture which were infected with 10,000 each of O. circumcincta and T. colubriformis larvae either 7 days before, 7 days after, or at the time they commenced grazing either sulla or lucerne. Lambs which grazed sulla had lower (P<0.05) FEC and lower (P<0.05) O. circumcincta burdens than lambs which grazed lucerne but timing of infection had no effect on FEC or worm burdens. T. colubriformis numbers were not affected by treatment or herbage. In conclusion, the sulla diet resulted in lower O. circumcincta numbers compared to lucerne outdoors and some evidence of an immunogenic response was obtained indoors. However, neither the herbage nor the immunogenic response reduced T. colubriformis numbers in either experiment.     

Studies on the Response Time for Plasma Urea Nitrogen as a Rapid Measure for Dietary Protein Quality in Pigs

The optimal response time of plasma urea nitrogen (PUN) was investigated in slaughter pigs fed diets based on barley, wheat or casein as protein sources. Four blood samples were collected during the day from a catheter in the jugular vein: one sample was collected 0.5 h before morning feeding while the other three samples were collected 2, 4 and 6 h after the morning feeding. The effect from previously fed diets on the specific response from the test diet was investigated. However, only the diet fed on the previous day was found to influence the values of PUN before the morning feeding. The reported experiments included nine different diets fed to six pigs in six different feeding designs, all requiring 1 or 2 days for investigating the test diet. The diet used in the morning feeding also significantly influenced the concentration of PUN during the following 6 h. In general, a good agreement was found between the calculated biological value (BV) of the diet and the response of PUN. It was concluded that analysis of PUN can be used as a rapid response parameter for testing the protein quality of the diet and, consequently, this analysis may also be used as a rapid method for determining amino acid requirements in pigs.