Immunization of cattle with a Rhipicephalus microplus chitinase peptide containing predicted B-cell epitopes reduces tick biological fitness.

Rhipicephalus microplus, the cattle fever tick, is the most important ectoparasite impacting the livestock industry worldwide. Overreliance on chemical treatments for tick control has led to the emergence of acaricide-resistant ticks and environmental contamination. An immunological strategy based on vaccines offers an alternative approach to tick control. To develop novel tick vaccines, it is crucial to identify and evaluate antigens capable of generating protection in cattle. Chitinases are enzymes that degrade older chitin at the time of moulting, therefore allowing interstadial metamorphosis. In this study, 1 R. microplus chitinase was identified and its capacity to reduce fitness in ticks fed on immunized cattle was evaluated. First, the predicted amino acid sequence was determined in 4 isolates and their similarity was analysed by bioinformatics. Four peptides containing predicted B-cell epitopes were designed. The immunogenicity of each peptide was assessed by inoculating 2 cattle, 4 times at 21 days intervals, and the antibody response was verified by indirect ELISA. A challenge experiment was conducted with those peptides that were immunogenic. The chitinase gene was successfully amplified and sequenced, enabling comparison with reference strains. Notably, a 99.32% identity and 99.84% similarity were ascertained among the sequences. Furthermore, native protein recognition was demonstrated through western blot assays. Chitinase peptide 3 reduced the weight and oviposition of engorged ticks, as well as larvae viability, exhibiting a 71% efficacy. Therefore, chitinase 3 emerges as a viable vaccine candidate, holding promise for its integration into a multiantigenic vaccine against R. microplus.

Greenhouse Gas Emissions and Crossbred Cow Milk Production in a Silvopastoral System in Tropical Mexico.

In Mexico, pasture degradation is associated with extensive pastures; additionally, under these conditions, livestock activities contribute considerably to greenhouse gas (GHG) emissions. Among the options to improve grazing systems and reduce GHG emissions, silvopastoral systems (SPS) have been recommended. The objectives of this work were to quantify the N outflow in a soil-plant-animal interface, as well as the CH4 emissions and milk production in an SPS with woody legumes (Leucaena leucocephala) that is associated with stargrass (Cynodon nlemfuensis). This was then compared with stargrass in a monoculture system (MS) in the seasons (dry and rainy period) over a two-year period. Dung was collected from the animals of each of the grazing systems and applied fresh to the land plots. Fresh dung and urine were collected from the cows of each grazing system and were applied to the experimental plots. In addition, the soil CH4 and N2O contents were measured to quantify the emissions. Average milk yield by seasons was similar: MS (7.1 kg per animal unit (AU)/day-1) and SPS (6.31 kg per AU/day-1). Cows in the MS had a mean N intake of 171.9 g/UA day-1 without seasonal variation, while the SPS animals' mean N intake was 215.7 g/UA day-1 for both seasons. For the urine applied to soil, the N2O outflow was higher in the MS (peak value = 1623.9 µg N-N2O m-2 h-1). The peak value for the SPS was 755.9 µg of N-N2O m-2 h-1. The N2O emissions were higher in the rainy season (which promotes denitrification). The values for the feces treatment were 0.05% (MS) and 0.01% (SPS). The urine treatment values were 0.52% (MS) and 0.17% (SPS). The emissions of CH4 showed that the feces of the SPS systems resulted in a higher accumulation of gas in the rainy season (29.8 g C ha-1), followed by the feces of the MS system in the dry season (26.0 g C ha-1). Legumes in the SPS helped to maintain milk production, and the N2O emissions were lower than those produced by the MS (where the pastures were fertilized with N).

Impact of orange essential oil on enteric methane emissions of heifers fed bermudagrass hay.

In this study, the effects of orange essential oil (OEO) on the rumen fermentation, nutrient utilization, and methane (CH4) emissions of beef heifers fed a diet of bermudagrass (Cynodon dactylon) were examined. In addition, in vitro and in situ experiments were conducted. The in vitro experiment consisted of three treatments: control (CTL, no OEO), OEO1 (0.25% OEO), and OEO2 (0.5% OEO). The forage to concentrate ratio was 70:30 (dry matter [DM] basis) in all treatments. No changes in pH, proportions of volatile fatty acids, and the acetate:propionate ratio were observed (P > 0.05). The addition of 0.25% OEO resulted in a reduction in CH4 production (mL/g) relative to the control (P < 0.05). In the in situ experiment, 5 g of total mixed ration (CTL, OEO1, and OEO2) were incubated for 6, 12, 24, 48, and 72 h. Potential and effective degradability were not affected by OEO supplementation (P > 0.05). In the in vivo study, six crossbred beef heifers (Bos indicus × Bos taurus), fitted with rumen cannulas, were assigned to three different treatments: no additive (CTL), 0.25% OEO (OEO1), and 0.5% OEO (OEO2) in a replicated 3 × 3 Latin square (21-day periods). Heifers were fed at 2.8% body weight. In vivo CH4 production was measured in open-circuit respiration chambers. Reductions in gross energy consumption, apparent total tract digestibility, and rumen valerate concentration were observed for OEO2 compared to the control (P < 0.05). Additionally, decreases in CH4 emissions (g/day; P < 0.05) and CH4 (MJ gross energy intake/day; P < 0.05) were observed in response to supplementation of 0.5% OEO as compared to the CTL treatment. Thus, supplementation of 0.5% OEO reduced CH4 emissions (g/day) by 12% without impacting the DM intake of heifers fed bermudagrass hay as a basal ration.

Effect of Chitosan and Naringin on Enteric Methane Emissions in Crossbred Heifers Fed Tropical Grass.

In order to meet consumer needs, the livestock industry is increasingly seeking natural feed additives with the ability to improve the efficiency of nutrient utilization, alternatives to antibiotics, and mitigate methane emissions in ruminants. Chitosan (CHI) is a polysaccharide with antimicrobial capability against protozoa and Gram-positive and -negative bacteria, fungi, and yeasts while naringin (NA) is a flavonoid with antimicrobial and antioxidant properties. First, an in vitro gas production experiment was performed adding 0, 1.5, 3.0 g/kg of CHI and NA under a completely randomized design. The substrate containing forage and concentrate in a 70:30 ratio on a dry matter (DM) basis. Compounds increased the concentration of propionic acid, and a significant reduction in methane production was observed with the inclusion of CHI at 1.5 g/kg in in vitro experiments (p < 0.001). In a dry matter rumen degradability study for 96 h, there were no differences in potential and effective degradability. In the in vivo study, six crossbred heifers fitted with rumen cannulas were assigned to a 6 × 6 Latin square design according to the following treatments: control (CTL), no additive; chitosan (CHI1, 1.5 g/kg DMI); (CHI2, 3.0 g/kg DMI); naringin (NA1, 1.5 g/kg DMI); (NA2, 3.0 g/kg DMI) and a mixture of CHI and NA (1.5 + 1.5 g/kg DMI) given directly through the rumen cannula. Additives did not affect rumen fermentation (p > 0.05), DM intake and digestibility of (p > 0.05), and enteric methane emissions (p > 0.05). CHI at a concentration of 1.5 g/kg DM in in vitro experiments had a positive effect on fermentation pattern increasing propionate and reduced methane production. In contrast, in the in vivo studies, there was not a positive effect on rumen fermentation, nor in enteric methane production in crossbred heifers fed a basal ration of tropical grass.

Role of Secondary Plant Metabolites on Enteric Methane Mitigation in Ruminants.

The rumen microbiome plays a fundamental role in all ruminant species, it is involved in health, nutrient utilization, detoxification, and methane emissions. Methane is a greenhouse gas which is eructated in large volumes by ruminants grazing extensive grasslands in the tropical regions of the world. Enteric methane is the largest contributor to the emissions of greenhouse gases originating from animal agriculture. A large variety of plants containing secondary metabolites [essential oils (terpenoids), tannins, saponins, and flavonoids] have been evaluated as cattle feedstuffs and changes in volatile fatty acid proportions and methane synthesis in the rumen have been assessed. Alterations to the rumen microbiome may lead to changes in diversity, composition, and structure of the methanogen community. Legumes containing condensed tannins such as Leucaena leucocephala have shown a good methane mitigating effect when fed at levels of up to 30-35% of ration dry matter in cattle as a result of the effect of condensed tannins on rumen bacteria and methanogens. It has been shown that saponins disrupt the membrane of rumen protozoa, thus decreasing the numbers of both protozoa and methanogenic archaea. Trials carried out with cattle housed in respiration chambers have demonstrated the enteric methane mitigation effect in cattle and sheep of tropical legumes such as Enterolobium cyclocarpum and Samanea saman which contain saponins. Essential oils are volatile constituents of terpenoid or non-terpenoid origin which impair energy metabolism of archaea and have shown reductions of up to 26% in enteric methane emissions in ruminants. There is emerging evidence showing the potential of flavonoids as methane mitigating compounds, but more work is required in vivo to confirm preliminary findings. From the information hereby presented, it is clear that plant secondary metabolites can be a rational approach to modulate the rumen microbiome and modify its function, some species of rumen microbes improve protein and fiber degradation and reduce feed energy loss as methane in ruminants fed tropical plant species.

The Role of Chitosan as a Possible Agent for Enteric Methane Mitigation in Ruminants.

Livestock production is a main source of anthropogenic greenhouse gases (GHG). The main gases are CH4 with a global warming potential (GWP) 25 times and nitrous oxide (N2O) with a GWP 298 times, that of carbon dioxide (CO2) arising from enteric fermentation or from manure management, respectively. In fact, CH4 is the second most important GHG emitted globally. This current scenario has increased the concerns about global warming and encouraged the development of intensive research on different natural compounds to be used as feed additives in ruminant rations and modify the rumen ecosystem, fermentation pattern, and mitigate enteric CH4. The compounds most studied are the secondary metabolites of plants, which include a vast array of chemical substances like polyphenols and saponins that are present in plant tissues of different species, but the results are not consistent, and the extraction cost has constrained their utilization in practical animal feeding. Other new compounds of interest include polysaccharide biopolymers such as chitosan, mainly obtained as a marine co-product. As with other compounds, the effect of chitosan on the rumen microbial population depends on the source, purity, dose, process of extraction, and storage. In addition, it is important to identify compounds without adverse effects on rumen fermentation. The present review is aimed at providing information about chitosan for dietary manipulation to be considered for future studies to mitigate enteric methane and reduce the environmental impact of GHGs arising from livestock production systems. Chitosan is a promising agent with methane mitigating effects, but further research is required with in vivo models to establish effective daily doses without any detrimental effect to the animal and consider its addition in practical rations as well as the economic cost of methane mitigation.

Molecular epidemiology of bovine anaplasmosis with a particular focus in Mexico.

Bovine anaplasmosis, caused by the rickettsia Anaplasma marginale, has a worldwide distribution and is the cause of great economic losses in developing countries where it is highly endemic. Transmission is carried mainly by ixodid ticks: Dermacentor spp. and Rhipicephalus (Boophilus) spp. Mechanical transmission is important in disseminating the disease within and across herds. The relationship between the rickettsia, the host and the vector is complex. Several surface proteins (Msps) have been described with functions that span from adhesins towards the erythrocyte and tick cells to evasion of the immune system of the host through the generation of antigenic variants. Biologic transmission of A. marginale through Dermacentor ticks has been well studied but many questions are unresolved as to how this organism spreads within and across herds and little is known about the role Rhipicephalus (Boophilus) ticks play in transmission in the Americas. Mechanical transmission in the absence of ticks and lack of transmission through ticks are questions that need to be addressed. Phylogenetic studies of the rickettsia show wide antigenic and genetic mosaics which affects the design of new vaccines. In the present work we will discuss the molecular elements in the relationship between the rickettsia, the tick and the mammalian host associated to the distribution and persistence of the pathogen in nature.