Degradation of transgenic Cry1Ab DNA and protein in Bt-176 maize during the ensiling process

Maize silage is commonly used as feed for farm animals. The aim of this study was to monitor the time-dependent degradation of non-recombinant chloroplast DNA (exemplified by the rubisco gene) in comparison with the recombinant cry1Ab gene in the course of the ensiling process. In parallel, the Cry1Ab protein content and fragment sizes were determined. Fragments of the rubisco (173, 896, 1197, 1753 and 2521 bp) and of the cry1Ab gene (211, 420, 727 and 1,423 bp) were selected to investigate the DNA degradation process. The detection of the Cry1Ab protein was performed using an enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Rubisco gene fragments of 173 bp were still detectable after 61 days, while fragments of 1,197 and 2,521 bp were detectable up to 30 days and on the first day only respectively. Polymerase chain reaction (PCR) analyses revealed that fragments of the cry1Ab gene with sizes of 211 and 420 bp were detectable up to 61 days, fragments with sizes of 727 and 1,423 bp, 30 and 6 days respectively. The ELISA showed a decrease of the Cry1Ab protein in maize silage during the ensiling process. No marked degradation was observed during the first 43 h. Thereafter, a sharp decrease was measured. After 61 days, 23.6 +/- 0.9% of the initial Cry1Ab protein was still detectable. Immunoblotting confirmed the results of the ELISA showing a positive signal of approximately 60 kDa size for 8 days of ensiling; no further immunoactive fragments were detectable by immunoblotting. In conclusion, the ensiling process markedly decreases the presence of long functional cry1Ab gene fragments and full size Cry1Ab protein.     

Detection of corn intrinsic and recombinant DNA fragments and Cry1Ab protein in the gastrointestinal contents of pigs fed genetically modified corn Bt11

Genetically modified corn has been approved as an animal feed in several countries, but information about the fate of genetically modified DNA and protein in vivo is insufficient. Genetically modified corn Bt11 is developed by inserting a recombinant DNA sequence encoding insecticidal Cry1Ab protein from Bacillus thuringiensis subsp. kurstaki. We examined the presence of corn intrinsic and recombinant cry1Ab gene by PCR, and the Cry1Ab protein by immunological tests in the gastrointestinal contents of five genetically modified corn Bt11-fed and five nongenetically modified corn-fed pigs. Fragments of corn zein (242 bp), invertase (226 bp) and of ribulose-1,5-bisphosphate carboxylase/ oxygenase genes (1,028 bp) were detected in the gastrointestinal contents of both Bt11 and nongenetically modified corn-fed pigs. Fragments of recombinant cry1Ab gene (110 bp and 437 bp) were detected in the gastrointestinal contents of the Bt11-fed pigs but not in the control pigs. Neither corn intrinsic nor cry1Ab gene fragments were detected in the peripheral blood by PCR. The gastrointestinal contents were positive for Cry1Ab protein by ELISA, immunochromatography, and immunoblot; however, these methods did not work for blood and precluded conclusions about any potential absorption of the protein. These results suggest that ingested corn DNA and Cry1Ab protein were not totally degraded in the gastrointestinal tract, as shown by their presence in a form detectable by PCR or immunological tests.     

不同来源肽对培养液中瘤胃细菌蛋白产量的影响

试验研究了大豆肽、玉米肽和瘤胃液肽对培养液中瘤胃细菌蛋白产量的影响。结果表明:培养液中氨基氮含量越高,细菌生长速度越快,菌体蛋白氮产量显著增加(P<0 01或P<0 05)。培养初期(0～6h),细菌生长快,菌体蛋白氮产量也显著增加(P<0 01或P<0 05);培养后期(6～24h),细菌生长缓慢,菌体蛋白氮产量处于平稳期(P>0 05)。对于不同来源肽来说,瘤胃液肽和大豆肽对细菌生长的促进作用要明显好于玉米肽(P<0 05)。结果表明:瘤胃细菌生长需要肽营养,肽可能是细菌生长的限制性因素之一。     

Effects of feeding calves genetically modified corn bt11: a clinico-biochemical study

Genetically modified corn Bt11 is insect-resistant and expresses Cry1Ab toxin, an insecticidal protein, in kernels. Although Bt11 corn is considered safe based on animal performance, there are no reports available on the clinico-biochemical effects of feeding it to cattle. In this study, we evaluated the effects of feeding Bt11 to calves, using blood and ruminal clinico-biochemical parameters. Our three-month-long feeding experiment demonstrated that calves (n=6), fed with a ration containing 43.3% of Bt11 corn kernels as dry matter, did not develop any discernible clinical, hematological, biochemical, or ruminal abnormalities as compared with control calves (n=6) fed non-Bt11 corn. The results suggest that the transgenic Bt11 has no negative clinico-biochemical effects on calves.     

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.     

Influence of transgenic corn (CBH 351, named Starlink) on health condition of dairy cows and transfer of Cry9C protein and cry9C gene to milk, blood, liver and muscle

The influence of transgenic event CBH 351 (Starlink)-derived hybrid corn (SL) on the health condition, physiological function and lactational performance of dairy cows as well as the transfer of the cry9C gene and Cry9C protein present in SL to milk, blood, liver and muscles was examined, and compared with a diet containing non-transgenic (isogenic) control corn (non-SL). After adapting to a diet containing non-SL for 2 weeks, four Holstein cows were assigned to each of the non-SL and SL groups and were fed diets containing non-SL or SL, respectively, for 5 weeks. There were no significant influences on the physiological condition, milk yield or serum biochemical and hematological values after feeding with SL. There was also no influence on pH value, cell density of protozoa, or volatile fatty acid concentration and composition of rumen fluids. In addition, no significant differences were observed on histopathological examination of the major organs and tissues between the SL and non-SL groups. Moreover, the cry9C gene and Cry9C protein were not detected by the polymerase chain reaction method and ELISA in the milk, blood, liver and muscles of the cows at the end of the experiment.     

不同处理玉米的有机物质瘤胃降解率及小肠消化率的研究

用３头带瘤胃瘘管的杂种肉牛测定玉米、无机保护剂处理玉米、有机保护剂处理玉米、１０％和３０％鲜血处理玉米有机物质（ＯＭ）和非蛋白质有机物质（ＮＰＯＭ）的瘤胃动态降解率，ＯＭ分别为５３．０３％，４３．９１％，５３．５７％，３５．７３％和３８．８５％，ＮＰＯＭ分别为５３．６７％，４８．０６％，５５．７２％，３９．２４％和４４．４８％。用酶解法（牛小肠液冻干粉（ＢＩＦ））测得玉米、无机保护剂处理玉米、有机保护剂处理玉米、１０％和３０％鲜血处理玉米１２小时瘤胃非降解ＯＭ的消化率分别为７４．３９％，７６．２６％，７５．５４％，７７．８８％和７７．４３％，ＮＰＯＭ分别为６３．９２％，６４．７８％，６４．４３％，６７．７８％和６５．００％。     

ORIGINAL ARTICLE: Ruminal and total tract phosphorus release from feedstuffs in cattle measured using the mobile nylon bag technique

Phosphorus (P) excretion in manure is a concern for dairy and beef producers. Excess P released into surface water runoff can lead to eutrophication and algal blooms in streams and lakes. One approach to reducing P excretion is to reduce dietary P. Data regarding P release from feedstuffs is limited and more precise formulations based on specific feed P release in the digestive tract may be one way to lower excreted P. In this experiment, the mobile nylon bag technique was used to determine the disappearance of P in corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton‐85 bermudagrass hay in steers after ruminal (24 h), ruminal + pepsin/HCl (rumen + PHCl), and ruminal + pepsin/HCl + intestinal (rumen + PHCl + I) incubation. Ruminal disappearance of P differed (p < 0.05) between feedstuffs and by site of incubation. Total tract (rumen + PHCl + I) P disappearance for corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton‐85 bermudagrass hay were 90.6%, 93.7%, 83.8% and 84.0% respectively. The range in P release (approximately 7%) indicates that considering P availability when balancing rations could have a measurable impact on subsequent P excretion from ruminants. More data concerning P availability as affected by other feed ingredients or plant species, maturity, and/or quality are needed to more accurately define P release from ruminant feeds.     

Amino acid profiles of rumen undegradable protein: a comparison between forages including cereal straws and alfalfa and their respective total mixed rations

Optimizing the amino acid (AA) profile of rumen undegradable protein (RUP) can positively affect the amount of milk protein. This study was conducted to improve knowledge regarding the AA profile of rumen undegradable protein from corn stover, rice straw and alfalfa hay as well as the total mixed ratio diets (TMR) based on one of them as forage source [forage‐to‐concentrate ratio of 45:55 (30% of corn stover (CS), 30% of rice straw (RS), 23% of alfalfa hay (AH) and dry matter basis)]. The other ingredients in the three TMR diets were similar. The RUP of all the forages and diets was estimated by incubation for 16 hr in the rumen of three ruminally cannulated lactating cows. All residues were corrected for microbial colonization, which was necessary in determining the AA composition of RUP from feed samples using in situ method. Compared with their original AA composition, the AA pattern of forages and forage‐based diets changed drastically after rumen exposure. In addition, the extent of ruminal degradation of analysed AA was not constant among the forages. The greatest individual AA degradability of alfalfa hay and corn stover was Pro, but was His of rice straw. A remarkable difference was observed between microbial attachment corrected and uncorrected AA profiles of RUP, except for alfalfa hay and His in the three forages and TMR diets. The ruminal AA degradability of cereal straws was altered compared with alfalfa hay but not for the TMR diets. In summary, the AA composition of forages and TMR‐based diets changed significantly after ruminal exposure, indicating that the original AA profiles of the feed cannot represent its AA composition of RUP. The AA profile of RUP and ruminal AA degradability for corn stover and rice straw contributed to missing information in the field.     

The effects of rumen fluid on the content of zearalenone in animal fodder

The object of the study was to clarify whether rumination has a bearing on the decomposition of zearalenone in the metabolism of the toxin or not. The experiment was performed using rumen fluid in vitro. Rumen fluid samples containing various amounts of zearalenone were incubated in a carbon dioxide atmosphere at 38 degrees C for two days. The zearalenone content was determined by liquid chromatography after 0, 4, 24 and 48 hours incubation periods. The incubation of 4 hours decreased the toxin content by 11%, that of 24 h by 29% and that of 48 h by 37.5% on average. These results indicate that the quantity of zearalenone and the quality of rumen fluid have effects on the ratio of the toxin decomposed.     

低淀粉饲粮条件下不同瘤胃降解淀粉水平对体外瘤胃发酵的影响

本试验旨在研究玉米作为淀粉来源的低淀粉饲粮条件下不同瘤胃降解淀粉(RDS)水平对体外瘤胃发酵的影响。以3头安装有永久性瘤胃瘘管的健康荷斯坦奶牛作为瘤胃液供体,各组分别以不同RDS水平饲粮作为发酵底物,体外产气法测定培养48 h时产气量和瘤胃发酵参数以及24 h时瘤胃微生物区系变化。结果表明:1)随着饲粮RDS水平的提高,体外培养48 h时产气量、潜在产气部分和产气速率呈线性升高(P0.05),快速发酵部分产气量呈线性下降(P0.05),干物质消失率呈线性升高(P0.05);2)随着饲粮RDS水平的提高,体外培养48 h时发酵液微生物蛋白、乙酸、丙酸、丁酸和总挥发性脂肪酸浓度呈线性升高(P0.05),pH和氨态氮浓度没有显著变化(P0.05);3)随着饲粮RDS水平的提高,体外培养24 h时发酵液中白色瘤胃球菌和嗜淀粉瘤胃杆菌的相对数量呈线性升高(P0.05),黄色瘤胃球菌、琥珀酸丝状杆菌、溶纤维丁酸弧菌、牛链球菌和溶淀粉琥珀酸单胞菌的相对数量没有显著变化(P0.05)。综合考虑,低淀粉饲粮条件下提高RDS水平有利于瘤胃发酵。     

不同蛋白质和碳水化合物饲料来源对牛瘤胃洗涤纤维降解和瘤胃液产物的定量研究

试验采用3×3拉丁方设计,3头安装永久性大口径瘤胃瘘管的青年母牛饲喂3种不同精饲料的日粮,3种精饲料分别为豆粕+玉米(日粮1),猪血粉+玉米(日粮2)和豆粕+小麦(日粮3)。精料日喂量按活牛体重的1%喂给,干玉米秸等量组成的日粮配给。试验为3个试验周期,每一周期为37d,其中适应期26d,在早晨采食后2、4、8、16和24h,分别5次实施瘤胃掏空,全量测定瘤胃物存留量。结果表明:日粮1在采食后2～8h瘤胃干物质、液体和NDF的存留量最低,与其他两种日粮相比差异显著(P<0.05);日粮1和日粮3瘤胃液氨氮存留量在采食后2～8h始终高于日粮2(P<0.05),但日粮3在采食4h后瘤胃液氨氮开始下降,而日粮1至采食后16h开始下降,日粮1瘤胃液氨氮数量采食后2～8h处于高峰状态,说明瘤胃微生物在瘤胃环境长时间一直保持稳定的降解能力;日粮1和日粮3在采食2～4h后处于较高的总挥发性脂肪酸(VFA)瘤胃存留量,日粮1在采食后8～16h瘤胃存留量降低,与日粮2和日粮3相比差异显著(P<0.05),日粮1对瘤胃VFA的快速移除,意味着瘤胃液的快速流出以及可能解释瘤胃固体物的快速移除。因此,日粮1和日粮3在牛瘤胃洗涤纤维降解和瘤胃液产物代谢模式发挥不同作用。     

N tau-methylhistidine--feed and duodenal content and ruminal degradation

N tau-methylhistidine (NMH) concentrations were determined in acid hydrolysates of 12 common feedstuffs for ruminants, and duodenal digesta from steers fed alfalfa haylage and high-moisture corn. For six species of grass hays, NMH concentrations ranged from nondetectable (ND; less than .1 nmol/g dry matter) to .6 nmol/g dry matter. Two legume hays had NMH concentrations of .9 and 2.0 nmol/g dry matter, respectively. For corn silage, high-moisture corn, beet pulp and soybean meal, NMH concentrations were 1.3, 1.1, 1.5 and 2.2 nmol/g dry matter, respectively. Duodenal digesta NMH concentrations ranged from ND to 1.2 nmol/g dry matter. When pure NMH (1 mM) was incubated with rumen fluid in vitro for 8 h, only 14% was degraded while leucine (1 mM) was totally degraded. From the feedstuffs used in this study, results show that exogenous (dietary) NMH is not a concern in skeletal muscle protein turnover studies in cattle using urinary NMH excretion because it can be calculated that potential NMH intake from the preceding feedstuffs would be less than 1% of normal urinary excretion and that ruminal microbes are not a potential source of NMH. NMH was resistant to in vitro ruminal degradation. The in vitro ruminal NMH degradation results suggest that when feedstuffs containing at least 15 nmol/g dry matter are fed (far greater than values observed in this study) a significant proportion of urinary NMH would arise directly from exogenous sources and would invalidate the use of this technique in assessing protein turnover in cattle.     

Effect of a saponin-based surfactant and aging time on ruminal degradability of flaked corn grain dry matter and starch

The objectives of this study were to investigate the effect of a saponin-based surfactant, Grain Prep surfactant (GP), and hot flake aging time on starch characteristics and ruminal DM and starch degradability of steam-flaked corn grain. In 2 experiments, the moisture content of incoming corn was automatically adjusted using the Grain Prep Auto Delivery System to 19.8% (Exp. 1) and 18.5% (Exp. 2). The application rate of GP was 22 mg/kg (as-is basis). Control corn was treated with water alone. Processed corn in Exp. 2 was stored in insulated containers for 0, 4, 8, or 16 h. Flaked corn samples were incubated in the rumen of lactating dairy cows for 0, 2, 4, 6, 16, or 24 h. In Exp. 1, GP increased, compared with the control, the soluble fraction and effective degradability (ED) of DM by 17.2 and 8.6%, respectively. The ED of cornstarch was increased by 6.7%. In Exp. 2, the concentration of soluble DM and starch were increased by GP by 15 and 24% compared with the control. The ED of DM and starch were also increased by 3 and 4%, respectively. No differences in gelatinization temperatures were observed due to treatment, except that GP-treated grain had a slightly greater mean gelatinization enthalpy in Exp. 2. In a pilot study, DM degradability parameters were not affected by germination of the corn kernels. Aging of the hot flakes for up to 16 h resulted in a quadratic decrease in DM and starch ruminal degradability. The aging process affected starch gelatinization enthalpy values of flaked grain in a manner opposite to that observed for ruminal DM and starch degradation. This phenomenon was most likely explained by increased starch intramolecular associations or crystallinity associated with starch annealing, or both. This study confirmed our previous observations that Grain Prep surfactant increases flaked corn DM and starch degradability in the rumen. Because the rate of degradation was not affected by the surfactant, the increase in degradability was attributed mainly to increases in DM and starch solubility.     

Extent and site of mineral release from six forage species incubated in mobile dacron bags

A study was conducted to measure the extent of DM disappearance and mineral release from six forage species within the rumen, abomasum and intestines of the adult bovine using the mobile bag technique. Three nonlactating Holstein cows, fitted with ruminal and duodenal cannulas, were given ad libitum access to alfalfa hay. One gram (DM) of alfalfa, rhizoma peanut, dwarf elephantgrass, bahiagrass, bermudagrass, and limpograss was individually weighed into 8-cm x 3-cm dacron bags. After ruminal incubation for 24 h, bags were incubated in an acid-pepsin solution (a simulated abomasal environment) for 1 h, inserted into the duodenum via cannula, and collected in the feces upon excretion. Ruminal incubation accounted for 86% to 100% of total DM disappearance. Release of Ca from all forages was at least 65%, with the majority having extents of release of over 70%. Most Ca was released in the rumen, but acid-pepsin incubation and washing increased Ca release an additional 17 to 272%. Forages with the highest NDF concentration (bermuda, bahia, and limpograss) sequestered Ca in the intestines. Total tract P release ranged from 84 to 98%, with an average of 7.5 percentage units occurring postabomasally. Grasses released more P in the intestines than legumes. Eighty-eight to 98% of total Mg was released in the rumen. Acid-pepsin incubation increased Mg release only slightly, with some Mg being sequestered in the intestines. Potassium release was complete in the rumen. Ranking of minerals based on maximal extent of release was K greater than Mg greater than P greater than Ca. With the exception of K, legumes released more of their minerals than grasses.     

Effect of harvest date and variety on ruminal degradability of ensiled maize grains in dairy cows.

In this study we investigated the influence of harvest date and genotype on the ruminal degradability of the organic matter of ensiled maize grains. Grains of the varieties Avenir, Byzance, CGS 5104 and CGS 5107 from six different harvest dates were available; they are classified as intermediate types between flint and dent corn. The six harvest dates, during which time the dry matter content of the ensiled grains rose from 52% to 66%, extended from 1st September to 19th October. Assuming a passage rate of k = 0.08, the effective ruminal degradability declined in this period on average from 93% to just under 79%; variety-specific deviations also increased markedly during this period. The dry matter content (x, DM in %) of the ensiled grains had a profound influence on ruminal degradation: a highly significant curvilinear decline in ruminal degradability (y) was calculated at increasing DM levels (k = 0.08), which can be described by the equation y = -0.072x2 (+/- 0.010) + 7.417x (+/- 1.186) - 98.71 (+/- 34.58) (B = 0.96; sy.x[%] = 1.36). The ruminal degradability of ensiled maize grains is about 5-10% higher than that of fresh maize grains.     

大豆皮替代羔羊饲粮中玉米或纤维成分对瘤胃消化率和生长性能的影响

通过瘤胃尼龙袋消化试验 (试验 1)和生长性能试验 (试验 2 )评价大豆皮替代羔羊饲粮中玉米或纤维饲料(玉米秸 )对瘤胃消化和生长性能的影响。饲粮处理为大豆皮替代饲粮中全部玉米 (SH C)、饲粮中 5 0 %纤维饲料(SH F)和对照饲粮 (CK)。试验 1结果表明 ,以大豆皮替代羔羊饲粮中全部玉米对于 2 4h和 4 8h干物质消化率(DMD)没有显著影响 (P >0 .0 5 ) ,但极显著降低了 2 4h和 4 8h细胞壁消化率 (NDFD) (P <0 .0 1) ;以大豆皮替代饲粮中 5 0 %纤维饲料显著提高了羔羊饲粮 2 4h和 4 8hDMD(P <0 .0 1)以及 4 8hNDFD(P <0 .0 5 )。试验 2结果表明 ,与对照组相比 ,SH C处理不影响羔羊日粮干物质采食量 (P >0 .0 5 )、日增重 (P >0 .0 5 )和饲料转化效率 (P >0 .0 5 ) ,但可以降低单位增重的饲料成本 ;SH F处理可以显著提高羔羊日粮干物质采食量 (P <0 .0 5 )、增重速度 (P <0 .0 1)和饲料转化效率 (P <0 .0 5 )。     

Effect of different methods for conserving rice grain on in situ ruminal degradation and in vivo nutrient digestion and rumen fermentation in steers

We investigated the effects of different rice conservation techniques on in situ ruminal degradation and in vivo nutrient digestibility and rumen fermentation in steers. Raw rice grain was dried before crushing (DRY), ensiled after crushing (ENS‐A), or ensiled before crushing (ENS‐B). Six ruminally cannulated steers were used in a replicated 3 × 3 Latin square design with three dietary treatments: diets containing DRY, ENS‐A, or ENS‐B at 36% of the dietary dry matter. The in situ rapidly degradable fraction and effective ruminal degradability were higher for ensiled rice than for DRY, and higher for ENS‐A than for ENS‐B. The ruminal pH was lower and the lactic acid and total volatile acid concentrations were higher for the steers fed ensiled rice than those fed the DRY diet, but a treatment effect was not observed in the comparison between ENS‐A and ENS‐B. The whole‐tract digestibility of crude protein and ether extract was improved when the rice grain was ensiled, but there were no differences in nutrient digestibility between ensiling methods. These results show that ensiling treatment can be a strategy to improve the nutrient value of rice grain, but the ensiling method has little impact on in vivo digestion.     

In vitro ruminal biotransformation of benzimidazole sulphoxide anthelmintics: enantioselective sulphoreduction in sheep and cattle

The comparative in vitro sulphoreduction of the (+) and (-) enantiomers of albendazole sulphoxide (ABZSO) and oxfendazole (OFZ) by ruminal fluid obtained from sheep and cattle, was investigated, under anaerobic conditions, in this study. Ruminal fluid samples were obtained from Holstein steers fitted with a permanent rumen fistula and from Corriedale lambs via an oesophageal tube. Albendazole sulphoxide, incubated as either the racemic (rac) mixture or as each individual enantiomeric form, was extensively sulphoreduced to form albendazole (ABZ) by ruminal fluid from both species. The concentrations of ABZ formed at different incubation times were between 55 and 158% greater after the incubation of cattle ruminal fluid with (+) ABZSO, compared with that produced when (-) ABZSO was the incubated substrate. Similarly, the concentrations of ABZ were 1.3--3.0-fold higher when (+) ABZSO was incubated with sheep ruminal fluid. Significantly higher rates of depletion were observed for the (+) enantiomeric form when ABZSO was incubated with ruminal fluid from both species. The rates of ABZ formation from both ABZSO enantiomeric forms were significantly higher in sheep compared with cattle ruminal fluid. Fenbendazole (FBZ) was the metabolite formed after the incubation of the racemic form of OFZ with ruminal fluid obtained from both species. The metabolic profile of both OFZ enantiomers followed a similar pattern to that observed for ABZSO enantiomers. A bi-directional chiral inversion of one enantiomer into its antipode was observed. The (+) enantiomer appeared in the incubation medium when (-) ABZSO was the incubated substrate, and also the (-) antipode was detected after (+) ABZSO incubation with ruminal fluid obtained from both species. The results reported here demonstrate an enantioselective ruminal sulphoreduction of ABZSO and OFZ (substrate enantioselectivity). These findings contribute to interpret the chiral behaviour of benzimidazole-sulphoxide anthelmintics.     

Effect of field pea level on intake, digestion, microbial efficiency, ruminal fermentation, and in situ disappearance in beef steers fed growing diets

Effects of increasing level of field pea (variety: Profi) on intake, digestion, microbial efficiency, and ruminal fermentation were evaluated in beef steers fed growing diets. Four ruminally and duodenally cannulated crossbred beef steers (367+/-48 kg initial BW) were used in a 4 x 4 Latin square. The control diet consisted of 50% corn, 23% corn silage, 23% alfalfa hay, and 4% supplement (DM basis). Treatments were field pea replacing corn at 0, 33, 67, or 100%. Diets were formulated to contain a minimum of 12% CP, 0.62% Ca, 0.3% P, and 0.8% K (DM basis). Each period was 14 d long. Steers were adapted to the diets for 9 d. On d 10 to 14, intakes were measured. Field pea was incubated in situ, beginning on d 10, for 0, 2, 4, 8, 12, 16, 24, 36, 48, 72, and 96 h. Bags were inserted in reverse order, and all bags were removed at 0 h. Ruminal fluid was collected and pH recorded at -2, 0, 2, 4, 6, 8, 10, and 12 h after feeding on d 13. Duodenal samples were taken for three consecutive days beginning on d 10 in a manner that allowed for a collection to take place every other hour over a 24-h period. Linear, quadratic, and cubic contrasts were used to compare treatments. There were no differences in DMI (12.46 kg/d, 3.16% BW; P > 0.46). Ruminal dry matter fill (P = 0.02) and mean ruminal pH (P = 0.009) decreased linearly with increasing field pea level. Ruminal ammonia-N (P < 0.001) and total VFA concentrations (P = 0.01) increased linearly with increasing field pea level. Total-tract disappearance of OM (P = 0.03), N (P = 0.01), NDF (P = 0.02), and ADF (P = 0.05) increased linearly with an increasing field pea level. There were no differences in total-tract disappearance of starch (P = 0.35). True ruminal N disappearance increased linearly (P < 0.001) with increasing field pea level. There were no differences in ruminal disappearance of OM (P = 0.79), starch (P = 0.77), NDF (P = 0.21), or ADF (P = 0.77). Treatment did not affect microbial efficiency (P = 0.27). Field pea is a highly digestible, nutrient-dense legume grain that ferments rapidly in the rumen. Because of their relatively high level of protein, including field peas in growing diets will decrease the need for protein supplementation. Based on these data, it seems that field pea is a suitable substitute for corn in growing diets.