Variation in potential feeding value of triticale forage among plant fraction, maturity stage, growing season and genotype.

Cereal forages, such as triticale forage, progressively gain interest as alternative crop for maize. The main study objective was to investigate the variation in potential feeding value of triticale forage among maturity stage, growing season and genotype, using total plant and stem fractions. Therefore, near infrared spectroscopy (NIRS) was evaluated as fast screening tool. The prediction ability was good (ratio of prediction to deviation, RPD ≥3.0) for total plant residual moisture, starch, sugars and for stem crude ash (CAsh) and neutral detergent fibre (aNDFom); suitable for screening (2.0 ≤ RPD <3.0) for total plant CAsh, acid detergent fibre (ADFom), in vitro digestibility of organic matter (IVOMD), in vitro digestibility of neutral detergent fibre (IVNDFD) and for stem total lignin (TL) and IVNDFD; poor (1.5 ≤ RPD <2.0) for total plant crude protein, crude fat, aNDFom, lignin (sa) and for stem Klason lignin (KL); unreliable (RPD <1.5) for stem residual moisture and acid soluble lignin (ASL). The evolution in potential feeding value of 36 genotypes harvested at the medium and late milk to the early, soft and hard dough stage was followed. The most important changes occurred between the late milk and early dough stage, with little variation in quality after the soft dough stage. During 2 growing seasons, variation in feeding value of 120 genotypes harvested at the soft dough stage was demonstrated. Interestingly, variation in stem IVNDFD is almost twice as high as for the total plant (CV 12.4% versus 6.6%). Furthermore, Spearman correlations show no link between dry matter yield and digestibility of genotypes harvested at the soft dough stage. Based on linear regression models ADFom appears as main predictor of both plant IVOMD and plant IVNDFD. Stem IVNDFD is particularly determined by KL.

The effect of crude protein reduction on performance and nitrogen metabolism in piglets (four to nine weeks of age) fed two dietary lysine levels1.

Lowering the CP level in piglet diets reduces the risk of postweaning diarrhea and N excretion to the environment. The question remains at what point CP becomes limiting. An experiment was designed with 2 standardized ileal digestible (SID) Lys levels (10 and 11 g) and 6 CP levels (140, 150, 160, 170, 180, 190 g/kg) in a 2 × 6 factorial design (with 6 pens of 6 animals each per treatment). Linear and quadratic (QP) mixed models of performance in function of CP were fitted to study the effect of SID Lys and CP and their interaction. To determine optima, QP models and broken line models with linear (BLL) or quadratic (BLQ) ascending portions were fitted through the data. It was hypothesized 1) that the response to a decreasing digestible CP level could be described with broken line models and 2) that the break point of these models is dependent on the dietary SID Lys level. Decreasing the CP level decreased ADG (P < 0.001). For G:F, the effect of decreasing CP level depended on the SID Lys level (P of the interaction = 0.028 in the linear model and P = 0.002 in the QP model). According to the BLL model, with 11 g SID Lys in the diet, G:F started to decline with CP levels < 176 g CP [SID Lys:CP = 0.062, SID Lys:apparent total tract digestible (ATTD) CP = 0.077], and with 10 g SID Lys, CP levels < 165 g/kg (SID Lys:CP = 0.061, SID Lys:ATTD CP = 0.075) depressed performance. Serum creatinine levels showed a linear decrease with increasing SID Lys:CP levels (P < 0.001). Across both SID Lys levels, when fitting a BLL model, minimal serum urea levels were reached at an SID Lys:CP ratio of 0.064. This seems to be the point where CP and not Lys limits muscle deposition. The small difference in break point between serum urea level and performance suggests that the composition of nonessential AA may also be at stake. The effect of decreasing CP level depends on SID Lys, and using a maximal SID Lys:CP ratio may be useful for optimizing the AA profile of dietary CP. When the SID Lys:CP ratio exceeds 0.064 (SID Lys:ATTD CP > 0.079), protein and not individual AA limits growth in most piglets between 4 and 9 wk of age.

Presence and analysis of plasmids in human and animal associated arcobacter species.

In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration.

Towards a typing strategy for Arcobacter species isolated from humans and animals and assessment of the in vitro genomic stability.

Arcobacter species have a widespread distribution with a broad range of animal hosts and environmental reservoirs, and are increasingly associated with human illness. To elucidate the routes of infection, several characterization methods such as pulsed-field gel electrophoresis (PFGE), amplified fragment-length polymorphism, and enterobacterial repetitive intergenic consensus (ERIC)-PCR have already been applied, but without proper validation or comparison. At present, no criterion standard typing method or strategy has been proposed. Therefore, after the validation of PFGE, those commonly applied typing methods were compared for the characterization of six human- and animal-associated Arcobacter species. With a limited number of isolates to be characterized, PFGE with restriction by KpnI is proposed as the first method of choice. However, ERIC-PCR represents a more convenient genomic fingerprinting technique when a large number of isolates is involved. Therefore, a first clustering of similar patterns obtained after ERIC-PCR, with a subsequent typing of some representatives per ERIC cluster by PFGE, is recommended. As multiple genotypes are commonly isolated from the same host and food, genomic plasticity has been suggested. The in vitro genomic stability of Arcobacter butzleri and A. cryaerophilus was assessed under two temperatures and two oxygen concentrations. Variability in the genomic profile of A. cryaerophilus was observed after different passages for different strains at 37°C under microaerobic conditions. The bias due to these genomic changes must be taken into account in the evaluation of the relationship of strains.

Occurrence of putative virulence genes in arcobacter species isolated from humans and animals.

Interest in arcobacters in veterinary and human public health has increased since the first report of the isolation of arcobacters from food of animal origin. Since then, studies worldwide have reported the occurrence of arcobacters on food and in food production animals and have highlighted possible transmission, especially of Arcobacter butzleri, to the human population. In humans, arcobacters are associated with enteritis and septicemia. To assess their clinical relevance for humans and animals, evaluation of potential virulence factors is required. However, up to now, little has been known about the mechanisms of pathogenicity. Because of their close phylogenetic affiliation to the food-borne pathogen Campylobacter and their similar clinical manifestations, the presence of nine putative Campylobacter virulence genes (cadF, ciaB, cj1349, hecA, hecB, irgA, mviN, pldA, and tlyA) previously identified in the recent Arcobacter butzleri ATCC 49616 genome sequence was determined in a large set of human and animal Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii strains after the development of rapid and accurate PCR assays and confirmed by sequencing and dot blot hybridization.

Arcobacter trophiarum sp. nov., isolated from fattening pigs.

In the course of a longitudinal study elucidating the dynamics of Arcobacter populations in pigs, 16 isolates of Gram-reaction-negative, rod-shaped, slightly curved, non-spore-forming bacteria were grouped by amplified fragment length polymorphism analysis into a distinct phenon within the genus Arcobacter. Fragments were generated for all isolates in a genus-specific PCR assay, but no amplicon was obtained in a species-specific multiplex-PCR test. Numerical analysis of the whole-cell protein profiles also showed that all isolates clustered in a single group that was distinct from related members of the genus Arcobacter. DNA-DNA hybridizations between two representative strains, designated 64(T) and 122, of the isolates obtained exhibited a mean DNA-DNA relatedness of 72 %. DNA-DNA hybridizations between strains 64(T) and 122 and reference strains of other animal-related bacteria of the genus Arcobacter revealed binding values of 47 % or less. The DNA G+C contents of the two representative strains were 28.5 and 28.4 mol%, respectively, and analysis of three marker genes identified Arcobacter cryaerophilus, A. thereius, A. cibarius and A. skirrowii as their closest phylogenetic neighbours. Strains 64(T) and 122 could be distinguished from other members of the genus Arcobacter by means of biochemical tests for catalase and urease activities, nitrate reduction, indoxyl acetate hydrolysis, lack of growth at 37 °C, growth in 2 % (w/v) NaCl, growth on 0.1 % sodium deoxycholate and non-supplemented Campylobacter charcoal-deoxycholate base medium and resistance to cephalothin (32 mg l(-1)) and cefoperazone (64 mg l(-1)). Additionally, a PCR assay was developed for the detection and identification of strains 64(T) and 122, which represent a novel species of the genus Arcobacter, for which the name Arcobacter trophiarum sp. nov. is proposed. The type strain is strain 64(T) (=LMG 25534(T) =CCUG 59229(T)).

Identification of five human and mammal associated Arcobacter species by a novel multiplex-PCR assay.

A multiplex-PCR assay with seven primers was developed for the identification of the five human and mammal related species of the emerging foodborne pathogen Arcobacter. The assay was validated using 58 reference and 358 collection strains isolated from humans and mammals. The selected primers on the 23 S RNA gene amplify a 2061 bp fragment from A. butzleri, a 1590 bp fragment from A. thereuis, a 1125 bp fragment from A. cibarius and an A. skirrowii specific fragment of 198 bp. For A. cryaerophilus, a primer set on the gyrA gene amplified a specific fragment of 395 bp. No PCR product was generated for closely related bacteria including Campylobacter and Helicobacter species. Furthermore, examination of the 23 S RNA gene of A. cryaerophilus revealed, besides large heterogeneity, the presence of intervening sequences ranging from 87 to 196 bp.

Reassessment of the taxonomy of Arcobacter cryaerophilus.

Arcobacter cryaerophilus is a heterogeneous species in which two distinct subgroups have been reported. In the present study, the taxonomic status of these subgroups was reassessed using amplified fragment length polymorphism and heat shock protein 60 gene sequence analysis. The results demonstrated that A. cryaerophilus has a complex taxonomic structure, which consists of multiple cores of strains that share intermediate levels of DNA-DNA hybridisation and exhibit low levels of DNA-DNA hybridisation towards other Arcobacter species. One of these cores consisted of the majority of strains and included most subgroup 2 strains from previous studies. A. cryaerophilus subgroup 1 strains represented three distinct cores, among which the type strain occupied a distinct position. These results therefore also demonstrate that the current subgroup nomenclature in A. cryaerophilus should be abandoned, and that the type strain is genetically aberrant and poorly represents strains belonging to this species.

Alternative sampling to establish the Escherichia coli O157 status on beef cattle farms.

Prevalence of Escherichia coli O157 in cattle at the farm level is mostly determined by taking individually rectal samples. From the animal welfare point of view the collection of such samples on the farm is not advisable. The present study evaluated alternative sample types to assess the E. coli O157 status of cattle farms. Twelve closed cattle farms were visited twice with a time interval of 6-8 months. Rectal and hide surface samples (the nose, the neck, the shoulder, the flank, and the round) were collected from beef cattle within the period of 5 months before slaughter and from their environment (overshoes from the pen bedding, swabs from the pen barrier, feed and water). Statistical analysis revealed that from all samples taken only the "overshoe method" might be a good sampling technique to substitute the collection of individual fecal samples to establish the E. coli O157 status of a farm and even a pen. Characterization of the isolates, using pulsed field gel electrophoresis, revealed that on each positive farm only one genotype was presented, even after a period of more than 6 months.