Effects of dietary additives identified as potential methane mitigators on production characteristics, wool quality and yield and tissue fatty acid composition of sheep

Effects of dietary additives identified as potential methane mitigators on production characteristics, wool quality and yield and tissue fatty acid composition of sheep The ability of dietary strategies to mitigate CH4 emissions must be balanced with their effects on animal performance in order to be widely adopted by producers. This thesis investigated promising supplements [P. freudenreichii, crude glycerin and two species of micro-algae (A. nodosum and Schizochytrium spp.)] in terms of their CH4 mitigation potential, effects on lamb production, fatty acid (FA) profile of lamb; and wool yield and quality characteristics. It is noted that there is a strong consumer push for a healthier FA composition of lamb and as such producers will inevitably shift production to meet consumer demands. Results presented here indicate the potential of P. freudenreichii to reduce CH4, but showed little effects on FA biohydrogenation. Supplementation of crude glycerin successfully replaced wheat in Merino ewe diets; however, no improvements were observed on wool yield or quality. The supplementation of Tasco® (A. Nodosum) did not affect production performance, but failed to favourably alter the FA profile of lamb as compared to other dietary oils. Conversely, DHA-Gold (Schizochytrium spp.) supplementation elicited a favourable shift in the FA profile of lamb through n-3 enrichment of both adipose tissue and skirt muscle. A further molecular investigation into the regulation of adipogenesis in lambs revealed differences in miRNA expression between subcutaneous and perirenal adipose tissues that could be influenced by micro-algae supplementation. As such, the results presented in this thesis suggest that although supplements may have the potential to reduce CH4 emissions, their effects on production may not always be favourable. In the current case, the supplementation of micro-algae (Schizochytrium spp.) proved to be the most effective at positively modifying the FA profile of lamb

A Pan-Global Study of Bacterial Leaf Spot of Chilli Caused by Xanthomonas spp.

Bacterial Leaf Spot (BLS) is a serious bacterial disease of chilli (Capsicum spp.) caused by at least four different Xanthomonas biotypes: X. euvesicatoria pv. euvesicatoria, X. euvesicatoria pv. perforans, X. hortorum pv. gardneri, and X. vesicatoria. Symptoms include black lesions and yellow halos on the leaves and fruits, resulting in reports of up to 66% losses due to unsalable and damaged fruits. BLS pathogens are widely distributed in tropical and subtropical regions. Xanthomonas is able to survive in seeds and crop residues for short periods, leading to the infections in subsequent crops. The pathogen can be detected using several techniques, but largely via a combination of traditional and molecular approaches. Conventional detection is based on microscopic and culture observations, while a suite of Polymerase Chain Reaction (PCR) and Loop-Mediated Isothermal Amplification (LAMP) assays are available. Management of BLS is challenging due to the broad genetic diversity of the pathogens, a lack of resilient host resistance, and poor efficacy of chemical control. Some biological control agents have been reported, including bacteriophage deployment. Incorporating stable host resistance is a critical component in ongoing integrated management for BLS. This paper reviews the current status of BLS of chilli, including its distribution, pathogen profiles, diagnostic options, disease management, and the pursuit of plant resistance

The structural and functional capacity of ruminal and cecal microbiota in growing cattle was unaffected by dietary supplementation of linseed oil and nitrate

Microorganisms in the digestive tract of ruminants differ i n their functionality and ability to use feed constituents. While cecal microbiota play an impo rtant role in post-rumen fermentation of residual substrates undigested in the rume n, limited knowledge exists regarding its structure and function. In this trial we inves tigated the effect of dietary supplementation with linseed oil and nitrate on methane emi ssions and on the structure of ruminal and cecal microbiota of growing bulls. Animals we re allocated to either a CTL (control) or LINNIT (CTL supplemented with 1.9% linseed and 1.0% nitrates) diet. Methane emissions were measured using the GreenFeed system . Microbial diversity was assessed using amplicon sequencing of microbial genomic DN A. Additionally, total RNA was extracted from ruminal contents and functional mcrA and mtt genes were targeted in amplicon sequencing approach to explore the diversity of functional gene expression in methanogens. LINNIT had no effect on methane yield (g/kg D MI) even though it decreased methane production by 9% (g/day; P < 0.05). Methanobrevibacter- and Methanomassiliicoccaceae -related OTUs were more abundant in cecum (72 and 24%) compared to rumen (60 and 11%) irrespective of the diet ( P < 0.05). Feeding LINNIT reduced the relative abundance of Methanomassiliicoccaceae mcrA cDNA reads in the rumen. Principal component analysis revealed significa nt differences in taxonomic composition and abundance of bacterial communities betwee n rumen and cecum. Treatment decreased the relative abundance of a few Ruminococcaceae genera, without affecting global bacterial community structure. Our resea rch confirms a high level of heterogeneity in species composition of microbial consort ia in the main gastrointestinal compartments where feed is fermented in ruminants. There wa s a parallel between the lack of effect of LINNIT on ruminal and cecal microbial commu nity structure and functions differences in Rumen and Cecum Microbiomes on one side and methane emission changes on the other. These re sults suggest that the sequencing strategy used here to study microbial diversity and function accurately reflected the absence of effect on methane phenotypes in bulls treated with linseed plus nitrate

From pre- to postweaning: Transformation of the young calf's gastrointestinal tract

The ruminant gastrointestinal tract (GIT) faces the challenge of protecting the host from luminal contents and pathogens, while supporting the absorption and metabolism of nutrients for growth and maintenance. The GIT of the calf in early life undergoes some of the most rapid microbial and structural changes documented in nature, and these adaptations in GIT function make the young calf susceptible to GIT diseases and disorders. Despite these challenges, the calf's GIT has a certain degree of plasticity and can sense nutrient supply and respond to bioactive ingredients. Calf GIT research has historically focused on the transition during weaning and characterizing ruminal papillae development using microscopy and digesta metabolite responses. Through the use of new molecular-based approaches, we have recently shown that delaying the age of weaning and providing a step-down weaning protocol is associated with a more gradual shift in ruminal microbiota to a postweaned state. In addition to ruminal adaptations during weaning, nutrient flow to the lower gut changes dramatically during weaning, coinciding with a wide array of structural and microbiological changes. Structural and gene expression changes suggest that the lower gut of the dairy calf undergoes alterations that may reduce barrier function when solid feeds are consumed. More recently, in vivo data revealed that the weaning transition increases total gut permeability of the calf. Interestingly, the lower gut may be able to communicate with the forestomach, meaning that a nutrient can be sensed in the lower gut and cause subsequent adaptations in the forestomach. An improved understanding of how diet, microbiota, and functional ingredients interact to affect growth and barrier function of the intestinal tract would greatly benefit the dairy calf industry. A mechanistic understanding of such adaptations would also aid in the formulation of specific management regimens and provision of functional ingredients required to characterize and enhance gut function in young calves

Isotopic natural abundance as biomarkers of between-animal variation in feed efficiency in ruminants

International audienceCurrent methods of determining feed efficiency in ruminants are laborious and difficult to measure and consequently, alternative biomarkers are being explored. Based on the idea of isotopic fractionation, we measured the natural abundance of δ15N and δ13C (‰) in plasma proteins of 54 Charolais cattle and performed a regression analysis against different feed efficiency indices to determine their potential a as biomarker to predict between-animal variations of feed efficiency. The cattle were examined for feed conversion efficiency (FCE) and residual feed intake (RFI), beginning at 11-13 months of age, over two years (n=20 in 2014 and n=34 in 2015). Despite identical dietary constituents, the crude protein composition varied across the two years (13 vs 15% DM in 2014 and 2015, respectively) and consequently, animals from each year were analyzed separately. The natural abundance of δ15N in plasma proteins was higher in 2014 cattle (δ15N av.=6.22), vs 2015 (δ15N av.=5.54). Whereas, δ13C was higher in animals from 2015 (δ13C av.=-24.61) vs 2014 (δ13C av.=- 25.13). A significant negative correlation was observed between δ15N and FCE in animals from both 2014 and 2015 (R2=0.62 and R2=0.52, respectively). Similarly, δ13C in plasma proteins showed a moderate negative correlation with FCE in 2014 (R2=0.34), but no correlation with FCE was observed in 2015 (R2=0.09). Nor was a correlation observed between RFI and either δ15N (R2=0.07 and R2=0.09) or δ13C (R2=0.04 and R2=0.005) in 2014 or 2015. The repeatability of the relationship between δ15N in plasma protein and feed conversion efficiency in the two groups of cattle indicates its potential as a biomarker between-animal variations of feed efficiency, measured as FCE but not RFI, in ruminants

The origin of N isotopic discrimination and its relationship with feed efficiency in fattening yearling bulls is diet-dependent

International audienceNitrogen (N) isotopic discrimination (i.e. the difference in natural N-15 abundance between the animal proteins and the diet; Delta N-15) is known to correlate with N use efficiency (NUE) and feed conversion efficiency (FCE) in ruminants. However, results from the literature are not always consistent across studies, likely due to isotopic discrimination pathways that may differ with the nature of diets. The objective of the present study was to assess at which level, from rumen to tissues, Delta N-15 originates and becomes related to NUE and FCE in fattening yearling bulls when they are fed two contrasted diets. Twenty-four Charolais yearling bulls were randomly divided into two groups and fed during 8 months, from weaning to slaughter, either 1) a high starch diet based on corn silage supplying a balanced N to energy ratio at the rumen level (starch) or 2) a high fiber diet based on grass silage supplying an excess of rumen degradable N (fiber). All animals were slaughtered and samples of different digestive pools (ruminal, duodenal, ileal and fecal contents), animal tissues (duodenum, liver and muscle), blood and urine were collected for each animal. Ruminal content was further used to isolate liquid-associated bacteria (LAB), protozoa and free ammonia, while plasma proteins were obtained from blood. All samples along with feed were analyzed for their N isotopic composition. For both diets, the digestive contribution (i.e. the N isotopic discrimination occurring before absorption) to the Delta N-15 observed in animal tissues accounted for 65 +/- 11%, leaving only one third to the contribution of post-absorptive metabolism. Concerning the Delta N-15 in digestive pools, the majority of these changes occurred in the rumen (av. Delta N-15 = 2.12 +/- 0.66 parts per thousand), with only minor N-15 enrichments thereafter (av. Delta N-15 = 2.24 +/- 0.41 parts per thousand), highlighting the key role of the rumen on N isotopic discrimination. A strong, significant overall relationship (n = 24) between Delta N-15 and FCE or NUE was found when using any post-absorptive metabolic pool (duodenum, liver, or muscle tissues, or plasma proteins; 0.52 < r < 0.73; P <= 0.01), probably as these pools reflect both digestive and post-absorptive metabolic phenomena. Fiber diet compared to starch diet had a lower feed efficiency and promoted higher (P <= 0.05) Delta N-15 values across all post-absorptive metabolic pools and some digestive pools (ruminal, duodenal, and ileal contents). The within-diet relationship (n = 12) between Delta N-15 and feed efficiency was not as strong and consistent as the overall relationship, with contrasted responses between the two diets for specific pools (diet x pool interaction; P <= 0.01). Our results highlight the contrasted use of N at the rumen level between the two experimental diets and suggests the need for different equations to predict FCE or NUE from Delta N-15 according to the type of diet. In conclusion, rumen digestion and associated microbial activity can play an important role on N isotopic discrimination so rumen effect related to diet may interfere with the relationship between Delta N-15 and feed efficiency in fattening yearling bulls

Development of ruminal and fecal microbiomes are affected by weaning but not weaning strategy in dairy calves

The nature of weaning, considered the most stressful and significant transition experienced by dairy calves, influences the ability of a calf to adapt to the dramatic dietary shift and thus, can influence the severity of production losses through the weaning transition. However, the effects of various feeding strategies on the development of rumen or fecal microbiota across weaning are yet to be examined. Here we characterized the pre- and post-weaning ruminal and fecal microbiomes of Holstein dairy calves exposed to two different weaning strategies, gradual (step-down) or abrupt. We describe the shifts towards a mature ruminant state, a transition which is hastened by the introduction of the solid feeds initiating ruminal fermentation. Additionally, we discuss the predicted functional roles of these communities, which also appear to represent that of the mature gastrointestinal system prior to weaning, suggesting functional maturity. This assumed state of readiness also appeared to negate the effects of weaning strategy on ruminal and fecal microbiomes and therefore, we conclude that the shift in gastrointestinal microbiota may not account for the declines in gain and intakes observed in calves during an abrupt weaning

Weaning age influences the severity of gastrointestinal microbiome shifts in dairy calves

Ruminants microbial consortium is responsible for ruminal fermentation, a process which converts fibrous feeds unsuitable for human consumption into desirable dairy and meat products, begins to establish soon after birth. However, it undergoes a significant transition when digestion shifts from the lower intestine to ruminal fermentation. We hypothesised that delaying the transition from a high milk diet to an exclusively solid food diet (weaning) would lessen the severity of changes in the gastrointestinal microbiome during this transition. beta-diversity of ruminal and faecal microbiota shifted rapidly in early-weaned calves (6 weeks), whereas, a more gradual shift was observed in late-weaned calves (8 weeks) up to weaning. Bacteroidetes and Firmicutes were the most abundant ruminal phyla in pre- and post-weaned calves, respectively. Yet, the relative abundance of these phyla remained stable in faeces (P >= 0.391). Inferred gene families assigned to KEGG pathways revealed an increase in ruminal carbohydrate metabolism (P <= 0.009) at 9, compared to 5 weeks. Conversely, carbohydrate metabolism in faeces declined (P <= 0.002) following a change in weaning status (i.e., the shift from pre- to post-weaning). Our results indicate weaning later facilitates a more gradual shift in microbiota and could potentially explain the negative effects of early-weaning associated with feeding a high-plane of pre-weaning nutrition

An early life methane inhibitor treatment reduced methane emissions in dairy calves

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