Coprophagia in early life tunes expression of immune genes after weaning in rabbit ileum.

Coprophagia by suckling rabbits, i.e. ingestion of feces from their mother, reduces mortality after weaning. We hypothesized that this beneficial effect of coprophagia is immune-mediated at the intestinal level. Therefore, this study investigated immune development after weaning by analyzing the ileal transcriptome at day 35 and 49 in rabbits with differential access to coprophagia in early life. Rabbit pups had access between day 1 and 15 to (i) no feces (NF) or (ii) feces from unrelated does (Foreign Feces, FF) or (iii) feces from unrelated does treated with antibiotics (FFab). 350 genes were differentially expressed between day 35 and day 49 in suckling rabbits with access to coprophagia. These genes coded for antimicrobial peptides, a mucin, cytokines and chemokines, pattern recognition receptors, proteins involved in immunoglobulin A secretion and in interferon signaling pathway. Strikingly, prevention of coprophagia or access to feces from antibiotic-treated does in early life blunted immune development between day 35 et 49 in the ileum of rabbits. Thus, coprophagia might be crucial for the maturation of intestinal immunity in rabbits and could explain why this behavior improves survival.

Effect of dietary supplementation with algae extracts on growth performance and caecal microbiota of broiler chickens.

1. The objective of this study was to test the dose response of dietary supplementation with algae extracts rich in marine-sulphated polysaccharides (MSP1 and MSP2) on the growing performance, body composition at slaughter and caecal microbiota of broiler chickens.2. Male broiler Ross 308 chicks 1-d-old were distributed into eight groups, a control group (unsupplemented), four groups supplemented with increasing doses of algae extract MSP1 (40, 81, 121 and 162 g/ton feed) and three groups supplemented with increasing doses of algae extract MSP2 (40, 81 and 162 g/ton feed). Each group comprised six pens of 56 chickens.3. All chickens were reared under challenging conditions, i.e. high rearing density of 42 kg/m2, fed growing and finishing diets containing, palm oil, rye and high levels of wheat and subjected to short daily fasting periods. The growth performance was recorded during rearing. At 10, 22 and 31 d of age, 12 chickens per group were euthanised to collect the caecal contents and determine microbiota composition and short-chain fatty acid levels. At d 35, the quality of litter and the condition of feathers, footpads and tarsals were scored. At d 36, 7 chickens per pen were slaughtered under commercial conditions to determine carcass composition and breast meat quality (ultimate pH and colour).4. Algal extract MSP1 increased the weight of the caeca and butyrate concentration in the caeca at d 22 (p ≤ 0.05). It increased the ultimate pH of breast fillet measured after slaughter at d 36 (p ≤ 0.05). Moreover, the group receiving 162 g/t MSP1 had a more diverse microbiota at d22. However, algal extract MSP2 had negligible effect on the different measured parameters.

Milk replacer feeding once or twice a day did not change the ruminal metabolomic profile and the microbial diversity of dairy calves from birth to weaning.

In commercial dairy production systems, feeding calves once a day could be an alternative to reduce labor expenses. Several studies comparing once (OAD) versus twice (TAD) a day milk feeding systems have not evidenced differences in calf growth, rumen development, blood parameters or health scores, but impact on ruminal microbiota remains to be investigated. The objective of this study was to determine the effects of OAD or TAD on the establishment of the ruminal microbiota and its metabolic activity. Sixteen male calves (45.9 ± 5.7 kg at birth) were involved in the trial from birth to weaning (63 d). After the colostrum phase, 2 feeding programs based on a milk replacer were tested and calves were allocated to these programs on d 5. To study the establishment of the bacterial community, ruminal fluid was obtained from each calf one hour after the morning meal at 7 (d 7), 35 (d 35) and 63 (d 63) days of age. The ruminal metabolome was evaluated at a 7 d interval from d 1 to d 63. Ruminal microbiota and metabolite profiles were characterized by 16 S rRNA gene sequencing- and by H-NMR spectroscopy, respectively. Our results showed that feeding milk replacer once or twice a day did not change the ruminal microbiota and metabolites of dairy calves from birth to weaning. Microbial data showed that diversity and richness increased with age, suggesting a shift from an heterogeneous and less diverse community after birth (d 7) to a more diverse but homogeneous community at 35 and 63 d. These findings suggest that feeding milk once a day can be successfully applied to a calf feeding system without compromising microbial establishment and functions.

Genetic relationships between efficiency traits and gut microbiota traits in growing pigs being fed with a conventional or a high-fiber diet.

In pigs, the gut microbiota composition plays a major role in the process of digestion, but is influenced by many external factors, especially diet. To be used in breeding applications, genotype by diet interactions on microbiota composition have to be quantified, as well as their impact on genetic covariances with feed efficiency (FE) and digestive efficiency (DE) traits. This study aimed at determining the impact of an alternative diet on variance components of microbiota traits (genera and alpha diversity indices) and estimating genetic correlations between microbiota and efficiency traits for pigs fed a conventional (CO) or a high-fiber (HF) diet. Fecal microbes of 812 full-siblings fed a CO diet and 752 pigs fed the HF diet were characterized at 16 weeks of age by sequencing the V3-V4 region of the 16S rRNA gene. A total of 231 genera were identified. Digestibility coefficients of nitrogen, organic matter, and energy were predicted analyzing the same fecal samples with near infrared spectrometry. Daily feed intake, feed conversion ratio, residual feed intake and average daily gain (ADG) were also recorded. The 71 genera present in more than 20% of individuals were retained for genetic analyses. Heritability (h²) of microbiota traits were similar between diets (from null to 0.38 ±â€…0.12 in the CO diet and to 0.39 ±â€…0.12 in the HF diet). Only three out of the 24 genera and two alpha diversity indices with significant h² in both diets had genetic correlations across diets significantly different from 0.99 (P < 0.05), indicating limited genetic by diet interactions for these traits. When both diets were analyzed jointly, 59 genera had h² significantly different from zero. Based on the genetic correlations between these genera and ADG, FE, and DE traits, three groups of genera could be identified. A group of 29 genera had abundances favorably correlated with DE and FE traits, 14 genera were unfavorably correlated with DE traits, and the last group of 16 genera had abundances with correlations close to zero with production traits. However, genera abundances favorably correlated with DE and FE traits were unfavorably correlated with ADG, and vice versa. Alpha diversity indices had correlation patterns similar to the first group. In the end, genetic by diet interactions on gut microbiota composition of growing pigs were limited in this study. Based on this study, microbiota-based traits could be used as proxies to improve FE and DE in growing pigs.

The link between the composition of the gut microbiota, i.e the composition of microorganisms in the gut, in pigs and their feed efficiency, i.e. their ability to utilize nutrients, as well as their ability to digest were studied from a genetic point of view. A family structure of 1,564 pigs were studied and fed with two different diets. One of the full-sib was fed a conventional diet used in breeding farms and the other one an alternative diet containing raw materials, less expensive but with a higher content of dietary fibers more difficult to digest. This study has shown that some microbiota microorganisms were genetically correlated with feed and digestive efficiency performances, positively or negatively, depending on the microorganisms. In addition, the diversity of microorganisms in the animal's gut was favorably correlated with the feed and digestive performances studied. Therefore, there is a genetic link between these performances and the composition of the animal's gut microbiota. Thus, a potential genetic selection on some intestinal microorganisms or diversity of microorganisms would allow to improve these performances, and in particular when pigs are fed with diet more difficult to digest.

Evolution of gut microbial community through reproductive life in female rabbits and investigation of the link with offspring survival.

The digestive microbiota plays a decisive role in shaping and preserving health throughout life. Rabbit younglings are born with a sterile digestive tract but then it gets progressively colonised by the microbiota of the nursing mother, by entering in contact with or ingesting the maternal droppings present in the nest. Here we posit that (i) offspring survival and (ii) lifespan of female rabbits are linked to how diverse their microbiota are. To test the hypothesis that maternal microbiota evolves in females having had different levels of offspring survival in their lifetime, we obtained 216 hard faecal samples from 75 female rabbits at ages 19.6, 31.6, 62.6 and 77.6 weeks. The annual mean offspring survival (MOS) at 64 days was calculated for each female then crossed against three alpha-diversity indexes (operational taxonomic units (OTUs), inverse Simpson index and Shannon index). Age was also analysed against these three parameters. The alpha-diversity indexes of the female faecal microbiota did not correlate with MOS, but they did decrease with age (e.g. from 712 OTUs at age 19.6 weeks to 444 OTUs at 77.6 weeks; P < 0.05). The age effect was also found in beta-diversity non-metric multidimensional scaling plots using the Bray-Curtis dissimilarity index and the unweighted UniFrac index but not for MOS. The ability of the microbiota composition from the faecal samples of young females (19.6 weeks old) to predict their lifespan was also evaluated. After subdividing the initial population into two classes (females that weaned a maximum of three litters and females living longer), we found no clear distinction between these two classes. To our knowledge, this is the first long-term study to characterise the gut microbiota of adult female rabbits through their reproductive life, thus laying foundations for using the gut microbiota data and its influence in studies on adult rabbits.

Impact of feed restriction and housing hygiene conditions on specific and inflammatory immune response, the cecal bacterial community and the survival of young rabbits.

Limiting the post-weaning intake of the young rabbit is known to improve its resistance to digestive disorders, whereas a degradation of its housing hygiene is assumed to have a negative impact on its health. This study aims at providing insights into the mechanism of digestive health preservation regarding both host (growth and immune response) and its symbiotic digestive microbiota. A 2×2 factorial design from weaning (day 28) to day 64 was set up: ad libitum intake or restricted intake at 70% of ad libitum, and high v. low hygiene of housing (n=105 per group). At day 36 and day 45, 15 animals/group were subcutaneously immunized with ovalbumin (OVA) to assess their specific immune response. Blood was sampled at 36, 45, 57 and 64 days of age to determine total and anti-OVA immunoglobulin type G (IgG) and haptoglobin levels. The cecal bacterial community was explored (18 per group) by 454 pyrosequencing of genes coding for the 16S ribosomal RNA, whereas cecal pH, NH3 and volatile fatty acid (VFA) concentrations were measured to characterize fermentative activity. A 30% reduction in feed intake reduced the growth by only 17% (P<0.001), and improved the feed conversion ratio by 15% (P<0.001), whereas the degradation of hygiene conditions slightly decreased the feed intake in ad libitum fed rabbits (-3.5%, P<0.02). As poor hygiene conditions did not affect weight gain, feed conversion was improved from day 42 (P<0.05). Restricted feeding led to a lower mortality between day 28 and day 40 (P=0.047), whereas degraded hygiene conditions decreased overall morbidity (7.8% v. 16.6%; P<0.01). Both a reduced intake and low hygiene conditions of housing affected microbiota composition and especially dominant genera belonging to the Ruminococcaceae family (P<0.01). Moreover, low hygiene was associated with a higher Ruminococcaceae/Lachnospiraceae ratio (3.7 v. 2.4; P<0.05). Cecal total VFA and pH were increased (+19%; P<0.001) and decreased (-0.1 pH unit; P<0.05), respectively, in feed-restricted rabbits. Neither specific anti-OVA IgG nor haptoglobin was affected by treatments. Total IgG concentrations were the highest in animals raised in poor hygiene conditions after 8 days of restriction, but decreased after 19 days of restriction in high hygiene conditions (-2.15%; P<0.05). In conclusion, the degradation of hygiene conditions failed to induce a systematic specific and inflammatory response in rabbit, but reduced morbidity instead. Our results suggest that the microbiota composition would be a helpful source of biomarkers of digestive health.

Survey of cattle tick, Riphicephalus (Boophilus) microplus, resistance to amitraz and deltamethrin in New Caledonia.

The evolution of tick resistance to acaricides in New Caledonia was followed in two ways: through two large scale surveys in 1998 and 2014 and through the routine analysis of samples of ticks with suspected resistance. The results of the two approaches were qualitatively similar though analysis of ticks with suspected resistance gave higher frequencies of resistance, as expected of a biased sample. Resistance tests using a larval packet test have been conducted since 1993 for deltamethrin and 2003 for amitraz. Deltamethrin was used in country-wide control from 1986 to 2003 and amitraz since 1996. This study analyzed the variation of resistance parameters such as lethal concentration 50 (LC50) and the resistance factor over 21 years for deltamethrin and LC99 over 11 years for amitraz. There was an increase in deltamethrin's annual mean LC50 from 1993 to 2004 when it reached 2.9 g/l and then a progressive decrease, reaching a level consistently below 1g/l since 2007. Even though breeders stopped using deltamethrin in New Caledonia in 2003, the percentage of susceptible strains has remained below 30% since 1998. Amitraz's LC99 mean increased significantly from 0.31 g/l in 2003 to 2.96 g/l in 2014. Whereas all tested strains in 2003 were susceptible, only 40% of strains tested at the request of farmers were susceptible in 2014. The recent territory-wide survey showed that 76.7% of strains are still susceptible. This study established that resistance to amitraz has developed slowly in New Caledonia. A reversion phenomenon may have occurred concerning deltamethrin resistance, visible through the decrease of LC50 mean and the decreased proportion of very resistant strains; however the proportion of susceptible strains remains at a low level and there is anecdotal evidence that high resistance can re-emerge rapidly.

Acaricidal activity of five essential oils of Ocimum species on Rhipicephalus (Boophilus) microplus larvae.

The aim of this study was to evaluate the acaricidal activity on the cattle tick Rhipicephalus (Boophilus) microplus of essential oils from three Ocimum species. Acaricidal activity of five essential oils extracted from Ocimum gratissimum L. (three samples), O. urticaefolium Roth, and O. canum Sims was evaluated on 14- to 21-day-old Rhipicephalus microplus tick larvae using larval packet test bioassay. These essential oils were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) showing great variations of their chemical compositions according to the botanical species and even within the O. gratissimum species; the acaricidal activity of their main compounds was also evaluated. The essential oils of O. urticaefolium and O. gratissimum collected in Cameroon were the most efficient with respective LC50 values of 0.90 and 0.98%. The two essential oils obtained from O. gratissimum collected in New Caledonia were partially active at a dilution of 5% while the essential oil of O. canum collected in Cameroon showed no acaricidal activity. The chemical analysis shows five different profiles. Whereas the essential oils of O. urticaefolium from Cameroon and O. gratissimum from New Caledonia contain high amounts of eugenol (33.0 and 22.3-61.0%, respectively), 1,8-cineole was the main component of the oil of an O. canum sample from Cameroon (70.2%); the samples of O. gratissimum oils from New Caledonia are also characterized by their high content of (Z)-ß-ocimene (17.1-49.8%) while the essential oil of O. gratissimum collected in Cameroon is mainly constituted by two p-menthane derivatives: thymol (30.5%) and γ-terpinene (33.0%). Moreover, the essential oil of O. urticaefolium showed the presence of elemicin (18.1%) as original compound. The tests achieved with the main compounds confirmed the acaricidal activity of eugenol and thymol with residual activity until 0.50 and 1%, respectively, and revealed the acaricidal property of elemicin, which was the most efficient compound with 100 % of acaricidal activity at a dilution of 0.25% and could be a valuable acaricide for the control of the cattle tick R. microplus.

Lactobacillus sakei modulates mule duck microbiota in ileum and ceca during overfeeding.

The supplementation with Lactobacillus sakei as probiotic on the ileal and cecal microbiota of mule ducks during overfeeding was investigated using high-throughput 16S rRNA gene-based pyrosequencing and real-time PCR. The ducks were overfed with or without L. sakei for 12 d with 56% ground corn and 42% whole corn. Samples were collected before the overfeeding period (at 12 wk), at 13 wk (meal 12 of overfeeding), and at 14 wk (meal 24), 3 h postfeeding. Whatever the digestive segment and the level of intake, Firmicutes, Bacteroidetes, and Proteobacteria were the dominant phyla in the bacterial community of mule ducks (at least 90%). Before overfeeding, ileal samples were dominated by Clostridia, Bacteroidia, and Gammaproteobacteria (80% and up), and cecal samples by Bacteroidia and Clostridia (around 85%). The richness and diversity decreased in the ileum and increased in the ceca after overfeeding. Overfeeding increased the relative abundance of Firmicutes and especially the Lactobacillus group in ileal samples. Nonmetric multidimensional scaling profiles separated the bacterial communities with respect to overfeeding only in cecal samples. Richness indicators decreased after L. sakei has been added at mid-overfeeding only in the ileum. In the ceca, the decrease of these indexes only occurred at the end of overfeeding. The addition of L. sakei triggers major changes in the ileum, whereas the ceca are not affected. Lactobacillus sakei decreased the relative abundance of Bacteroides at mid-overfeeding and the relative abundance of Enterobacteria at the end of overfeeding in the ileum.

Coprophagous behavior of rabbit pups affects implantation of cecal microbiota and health status.

During the first few weeks after delivery, female rabbits excrete fecal pellets, which are ingested by their pups. We hypothesized that maternal excretion of hard fecal pellets and the coprophagous behavior of their pups were involved in cecal microbiota implantation. Four groups were compared: in 1 group (FM), pups had free access to maternal fecal pellets; in a second group, ingestion of feces was prevented (NF); and in 2 additional groups, pups had access only to fecal pellets excreted by foreign females receiving either no antibiotic (FF) or tiamulin and tetracycline (FFab). A total of 109 litters in 3 batches were used to quantify excretion and ingestion of feces and mortality. Bacterial composition was assessed by 454 pyrosequencing of the V3 to V4 region of 16S RNA genes and fermentative measurements in 128 rabbits of 1 batch at age 14, 35, 49, and 80 d with 8 rabbits per group for each age with 2 rabbits per litter. The number of fecal pellets excreted by does from 2 to 20 d after delivery ranged widely, but was similar among groups (16.1 ± 12.6 fecal pellets/doe). The excretion peaked during the first 6 d after delivery. Foreign fecal ingestion (FF and FFab groups) was 3 times greater (P < 0.001) than ingestion of maternal feces (9.9 ± 7.8). Ingestion of feces in the FF group was greater than in the FFab groups (35.6 ± 9.3 vs. 29.5 ± 9.7; P < 0.05). Compared with the FM group, ingestion of feces in the FF and FFab groups began later (6 to 7 d vs. 2 to 3 d after birth) and peaked at 14 to 17 d (4.0 ± 1.8 hard fecal pellets·litter(-1) · d(-1)) and 13 to 15 d (3.5 ± 1.7 hard fecal pellets litter(-1) d(-1)), respectively. During the 36 to 49 d period, the FF and NF groups exhibited the least (2.8%) and greatest (9.5%) mortality, respectively (P = 0.03). At age 14 d, the cecal bacterial community was dominated by Bacteroidetes phyla (63.3 ± 15.1%), Bacteroidaceae family (36.0 ± 18.8%), and Bacteriodes genus (36.0 ± 2.3%). With increasing age, Firmicutes phyla, Lachnospiraceae, and Ruminococcaceae families became the dominant taxa (92.0 ± 4.7, 44.0 ± 13.7, 37.9 ± 11.6% at age 80 d, respectively). Impairment of fecal ingestion delayed this ecological succession, with greater and lower relative abundance of Bacteroidaceae and Ruminococcaceae, respectively, than in the other 3 groups at age 35 d (P < 0.10). In conclusion, although excretion of hard fecal pellets by does ranged widely, the coprophagous behavior of their pups affected the implantation of cecal bacterial microbiota.

Establishment of ruminal bacterial community in dairy calves from birth to weaning is sequential.

AIM: Establishment of ruminal bacterial community in dairy calves. METHODS AND RESULTS: Rumen bacterial community was analysed on 6 calves bred according to commercial practices from day one to weaning at day 83 of age, using 454 16S rRNA-based pyrosequencing. Samples taken at day 1 did not produce amplicons. Analysis of data revealed a three-stage implantation process with a progressive but important shift of composition. At day 2, the bacterial community was mainly composed of Proteobacteria (70%) and Bacteroidetes (14%), and Pasteurellaceae was the dominant family (58%). The bacterial community abruptly changed between days 2 and 3, and until day 12, dominant genera were Bacteroides (21%), Prevotella (11%), Fusobacterium (5%) and Streptococcus (4%). From 15 to 83 days, when solid food intake rapidly increased, Prevotella became dominant (42%) and many genera strongly decreased or were no longer detected. A limited number of bacteria genera correlated with feed intake, rumen volatile fatty acids and enzymatic activities. CONCLUSION: The ruminal bacterial community is established before intake of solid food, but solid food arrival in turn shapes this community. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides insight into the establishment of calves' rumen bacterial community and suggests a strong effect of diet.

OligoSpecificitySystem: global matching efficiency calculation of oligonucleotide sets taking into account degeneracy and mismatch possibilities.

Oligonucleotide sets are widely used in molecular biology to target a group of nucleic acid sequences using Polymerase Chain Reaction (PCR)-based technologies. Currently, the global matching efficiency of an oligonucleotide set is considered to be equal to the lower matching efficiency calculated for each oligonucleotide. However, sequences matching the limiting oligonucleotide did not always match the other oligonucleotide of the set, resulting in a biased evaluation of the matching efficiency. The OligoSpecificitySystem program avoid this bias by calculations of the real global matching efficiency of oligonucleotide sets. It can process all kinds of oligonucleotide sets, including the number of oligonucleotides, base pair degeneracy occurrences or mismatch occurrences.

Engineering the rabbit digestive ecosystem to improve digestive health and efficacy.

In rabbits, the bacterial and archaeal community of caecal ecosystem is composed mostly of species not yet described and very specific to that species. In mammals, the digestive ecosystem plays important physiological roles: hydrolysis and fermentation of nutrients, immune system regulation, angiogenesis, gut development and acting as a barrier against pathogens. Understanding the functioning of the digestive ecosystem and how to control its functional and specific diversity is a priority, as this could provide new strategies to improve the resistance of the young rabbit to digestive disorders and improve feed efficiency. This review first recalls some facts about the specificity of rabbit digestive microbiota composition in the main fermentation compartment, and its variability with some new insights based on recent molecular approaches. The main functions of the digestive microbiota will then be explained. Finally, some possible ways to control rabbit caecal microbiota will be proposed and a suitable timing for action will be defined.

Modification of activities of the ruminal ecosystem and its bacterial and protozoan composition during repeated dietary changes in cows.

Dietary change alters the ruminal ecosystem and can be regarded as a disturbance. Studying the response to a disturbance can help us understand the behavior of the ecosystem. Our work is concerned with the response of the ruminal ecosystem (composition and activities) during the application of repeated dietary disturbances to 6 dry Holstein cows. For 2 mo, the cows received a hay-based diet [experimental period (EP) 0], followed by 3 EP of successive changes (EP 1, 2, and 3) comprised of 2 parts: the first (10 d) with a corn silage-based diet and the second (25 d) with a hay-based diet. The measurements and samplings were done on the last days of EP 0 and of each part of EP 1 through 3, with the results of EP 0 used as covariables in the statistical models. The physicochemical measurements (pH and redox potential) and the fermentation variables (VFA, ammonia) were determined hourly between the morning and evening meals (n = 8 measurements/d). Samples of ruminal contents were taken 3 h after the morning meal to determine enzymatic activity [amylase, carboxymethyl cellulase (CMCase), and xylanase], to count the main protozoan genera and to quantify the bacteria by quantitative PCR, and to determine its structure by the capillary electrophoresis single-strand conformation polymorphism process. The pH fell for the corn silage-based diet with the EP (P < 0.05) but not for the hay-based diet. The VFA concentration decreased for both diets with the EP (P < 0.001), with the primary changes in acetate and propionate. The ammonia concentration increased for the corn silage-based diet with the EP (P < 0.05), whereas for the hay-based diet the highest value was observed for EP 2 (P < 0.05). The total quantity of bacteria decreased between EP 1 and 3 (P < 0.05) for both diets. The structure of the bacterial community was not affected by the disturbances for the corn silage-based diet, whereas for the hay-based diet large differences were evident between EP 1 and 3 (P < 0.05) and 2 and 3 (P < 0.01). The number of protozoa increased over the EP, with a more marked effect for the corn silage-based diet (diet × EP interaction, P < 0.05). The specific amylase, CMCase, and xylanase activities decreased over the EP for both diets (P < 0.05). The dietary changes applied in our experiment involved strong modifications of the ruminal ecosystem and alterations of ruminal fermentation and enzymatic activities. These alterations were reinforced with the repetition of the dietary changes.

Rhipicephalus sanguineus (Ixodida, Ixodidae) as intermediate host of a canine neglected filarial species with dermal microfilariae.

The life cycles of filarioids of dogs presenting dermal microfilariae have been little studied. Following the recent retrieval of dermal microfilariae identified as Cercopithifilaria sp. in a dog from Sicily (Italy), this study was designed to assess the role of the brown dog tick Rhipicephalus sanguineus as an intermediate host of this filarial species. An experimental tick infestation was performed on an infected dog using 300 nymphs of R. sanguineus. Engorged nymphs were collected and examined by both microscopic dissection and molecular analysis at five time points (i.e., the same day of tick detachment and 10, 20, 30 and 50 days post-detachment) to detect the presence and developmental stage of filariae in the ticks. A total of 270 engorged nymphs were collected from the dog and developing filarioid larvae detected in 10 (5%) out of 200 ticks dissected. Infective third-stage larvae were observed in 4 (2%) of the all dissected ticks, 30 days post-detachment. Twelve (6.6%) out of 181 samples molecularly tested were positive for Cercopithifilaria sp. This study demonstrates that nymphs of R. sanguineus feeding on a dog naturally infected by Cercopithifilaria sp. can ingest microfilariae, which develop up to the third infective stage thus suggesting that this tick species might act as an intermediate host of this little known canine filarioid.

Starch and oil in the donor cow diet and starch in substrate differently affect the in vitro ruminal biohydrogenation of linoleic and linolenic acids.

Trans isomers of fatty acids exhibit different health properties. Among them, trans-10,cis-12 conjugated linoleic acid has negative effects on milk fat production and can affect human health. A shift from the trans-11 to the trans-10 pathway of biohydrogenation (BH) can occur in the rumen of dairy cows receiving high-concentrate diets, especially when the diet is supplemented with highly unsaturated fat sources. The differences of BH patterns between linoleic acid (LeA) and linolenic acid (LnA) in such ruminal conditions remain unknown; thus, the aim of this work was to investigate in vitro the effects of starch and sunflower oil in the diet of the donor cows and starch level in the incubates on the BH patterns and efficiencies of LeA and LnA. The design was a 4 × 4 Latin square design with 4 cows, 4 periods, and 4 diets with combinations of 21 or 34% starch and 0 or 5% sunflower oil. The rumen content of each cow during each period was incubated with 4 substrates, combining 2 starch levels and either LeA or LnA addition. Capillary electrophoresis single-strand conformation polymorphism of incubates showed that dietary starch decreased the diversity of the bacterial community and the high-starch plus oil diet modified its structure. High-starch diets poorly affected isomerization and first reduction of LeA and LnA, but decreased the efficiencies of trans-11,cis-15-C18:2 and trans C18:1 reduction. Dietary sunflower oil increased the efficiency of LeA isomerization but decreased the efficiency of trans C18:1 reduction. An interaction between dietary starch and dietary oil resulted in the highest trans-10 isomers production in incubates when the donor cow received the high-starch plus oil diet. The partition between trans-10 and trans-11 isomers was also affected by an interaction between starch level and the fatty acid added to the incubates, showing that the trans-10 shift only occurred with LeA, whereas LnA was mainly hydrogenated via the more usual trans-11 pathway, whatever the starch level in the substrate, although the bacterial communities were not different between LeA and LnA incubates. In LeA incubates, trans-10 isomer production was significantly related to the structure of the bacterial community.

Effects of stocking density on the growth performance and digestive microbiota of broiler chickens.

Increased stocking densities are frequently reported to depress chicken growth performance, but the mechanisms behind this are not fully understood. This study was conducted to investigate the effects of stocking density on growth performance and digestive microbiota, known to be sensitive to environmental factors. Chickens were reared at 2 stocking densities, 12 or 17 birds/m(2). Growth performance was recorded between d 1 and 39, and litter was scored for quality on d 25, 31, and 37. Digestive microbiota was analyzed along the digestive tract (crop, ileum, ceca) of 3- and 6-wk-old chickens by using 2 molecular approaches: a qualitative method (fingerprinting by temporal temperature gradient gel electrophoresis) and a quantitative method (real-time PCR). An increase in stocking density was found to negatively affect the feed conversion ratio (+3.1%) and depress the daily BW gain of broilers (-5.5%) during the period from d 32 to 39 (P ≤ 0.05). Litter quality was reduced with the high stocking density as early as d 25. At 3 wk of age, stocking density strongly affected the fingerprint profiles of the bacterial community, with the highest modifications observed in the crop and ceca (R analysis of similarity = 0.77 and 0.69, respectively, P ≤ 0.05). At 6 wk of age, significant differences in the fingerprint profiles between the stocking densities appeared in the crop and ceca (R analysis of similarity = 0.52 and 0.27, respectively, P ≤ 0.05). The abundance of bacterial groups targeted by real-time PCR was affected by stocking density, but only to a limited extent. Because digestive microbiota may have consequences on the physiology of the digestive tract, its modification by an increase in stocking density may be involved in the reduced growth performance of the bird.

Changes over time in the bacterial communities associated with fluid and food particles and the ruminal parameters in the bovine rumen before and after a dietary change.

This work aimed to study the changes over time in the bacterial communities associated with the fluid and food particle fractions of the cow rumen following a change in diet. Four cannulated cows were fed a hay-based diet for 21 days and were then switched to a corn-silage-based diet for 33 days. The bacterial communities were regularly characterized by capillary electrophoresis - single-strand conformation polymorphism (CE-SSCP) and qPCR, and the main ruminal parameters were determined. The dietary change led to slight reductions in the diversity index, bacterial concentration, pH, and NH(3)-N concentration, and to an increase in the redox potential and volatile fatty acid concentrations. CE-SSCP profiles were not significantly affected by the dietary change but did change over time, with frequent fluctuations in both fluid and food particle fractions before and after the dietary change. The food particle fraction had a higher diversity index of bacterial community (+1.2 points, P < 0.001) and slightly more total bacteria than the fluid fraction of the rumen.

Rapid adaptation of the bacterial community in the growing rabbit caecum after a change in dietary fibre supply.

This work aimed to study the response of the growing rabbit caecal ecosystem (bacterial community and caecal environmental parameters) after a switch from a control to a low-fibre diet (LFD). A group of 160 rabbits were fed ad libitum a control diet (ADF: 20.4%) from weaning (36 days). At 49 days of age (day 0), 75 rabbits were switched to a LFD group (ADF: 10.7%), whereas 85 others (control group) remained on the control diet, for 39 days. Caecal contents were regularly sampled throughout the trial (60 rabbits per group). The bacterial community structure was characterized using CE-SSCP (capillary electrophoresis single strand conformation polymorphism) and total bacteria were quantified using real-time PCR. Redox potential (Eh), pH, NH(3)-N, volatile fatty acid (VFA) were measured in the caecum to characterize environmental parameters. The reduction of fibre in the diet modified the CE-SSCP profiles (P < 0.001) but not the diversity index (5.6 ± 0.8, ns). The number of 16S rRNA gene copies of total bacteria decreased (P < 0.01) in LFD rabbits compared with controls. In LFD rabbits, the caecal environment was less acid (+0.2 units; P < 0.01), more reductive (-11 mV; P < 0.05) and drier (+3.4 g 100 per g; P < 0.001), with an increase in NH3-N (+77%; P < 0.001) and a decrease in total VFA concentration (-17%; P < 0.001). We found significant correlations between the bacterial community, the quantity of bacteria and the caecal traits of the caecal ecosystem. Indeed, in both groups, the caecal traits barely constrained the total inertia of the CE-SSCP profile set (less than 14%), whereas total bacteria were positively related to total VFA, acetic acid and butyric acid levels, and Eh, and negatively related to pH. All the microbial and environmental modifications had occurred by day 2 and remained stable thereafter. These results suggest that the bacterial community in the growing rabbit caecum is able to adapt quickly after a change to in the dietary fibre supply to reach a new steady-state equilibrium.

Temperature and duration of heating of sunflower oil affect ruminal biohydrogenation of linoleic acid in vitro.

Sunflower oil heated at 110 or 150 degrees C for 1, 3, or 6h was incubated with ruminal content in order to investigate the effects of temperature and duration of heating of oil on the ruminal biohydrogenation of linoleic acid in vitro. When increased, these 2 parameters acted together to decrease the disappearance of linoleic acid in the media by inhibiting the isomerization of linoleic acid, which led to a decrease in conjugated linoleic acids and trans-C18:1 production. Nevertheless, trans-10 isomer production increased with heating temperature, suggesting an activation of Delta(9)-isomerization, whereas trans-11 isomer production decreased, traducing an inhibition of Delta(12)-isomerization. The amount of peroxides generated during heating was correlated with the proportions of biohydrogenation intermediates so that they might explain, at least in part, the observed effects. The effects of heating temperature and duration on ruminal bacteria community was assessed using capillary electrophoresis single-strand conformation polymorphism. Ruminal bacterial population significantly differed according to heating temperature, but was not affected by heating duration. Heating of fat affected ruminal biohydrogenation, at least in part because of oxidative products generated during heating, by altering enzymatic reactions and bacterial population.