Frontiers in Veterinary Science

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ISSN / EISSN : 2297-1769 / 2297-1769
Published by: Frontiers Media SA (10.3389)
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, Ewan T. MacLeod, Dennis Muhanguzi, Charles Waiswa, Alexandra P. Shaw, Susan C. Welburn
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.611141

Background: Tsetse-transmitted human African trypanosomiasis (HAT) remains endemic in Uganda. The chronic form caused by Trypanosoma brucei gambiense (gHAT) is found in north-western Uganda, whereas the acute zoonotic form of the disease, caused by T. b. brucei rhodesiense (rHAT), occurs in the eastern region. Cattle is the major reservoir of rHAT in Uganda. These two forms of HAT are likely to converge resulting in a public health disaster. This study examines the intricate and intrinsic links between cattle herd dynamics, livestock trade and potential risk of spread of rHAT northwards. Methods: A bio-economic cattle herd model was developed to simulate herd dynamics at the farm level. Semi-structured interviews (n = 310), focus group discussions (n = 9) and key informant interviews (n = 9) were used to evaluate livestock markets (n = 9) as part of the cattle supply chain analysis. The cattle market data was used for stochastic risk analysis. Results: Cattle trade in eastern and northern Uganda is dominated by sale of draft and adult male cattle as well as exportation of young male cattle. The study found that the need to import draft cattle at the farm level was to cover deficits because of the herd structure, which is mostly geared towards animal traction. The importation and exportation of draft cattle and disposal of old adult male cattle formed the major basis of livestock movement and could result in the spread of rHAT northwards. The risk of rHAT infected cattle being introduced to northern Uganda from the eastern region via cattle trade was found to be high (i.e. probability of 1). Conclusion: Through deterministic and stochastic modelling of cattle herd and cattle trade dynamics, this study identifies critical links between livestock production and trade as well as potential risk of rHAT spread in eastern and northern Uganda. The findings highlight the need for targeted and routine surveillance and control of zoonotic diseases such as rHAT.
Juan Omar Hernández-Ramírez, Rubén Merino-Guzmán, Guillermo Téllez-Isaías, Alma Vázquez-Durán,
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.677965

In vivo experiments were conducted to evaluate the effectiveness of a yeast cell wall fraction (YCW) to reduce the negative impact of aflatoxin B1 (AFB1) to the intestinal epithelium in broiler chickens. Zeta potential (ζ-potential), point of zero charge (pHpzc), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques were used to characterize the YCW. Two hundred one-day-old male Ross 308 broiler chickens were randomly allocated into four treatments: (1) control, chickens fed an AFB1-free diet; (2) AF, chickens feed an AFB1-contaminated diet (500 ng AFB1/g); (3) YCW, chickens fed an AFB1-free diet + 0.05% YCW; and (4) AF + YCW, chickens fed an AFB1-contaminated diet (500 ng AFB1/g) + 0.05% YCW. At the end of the 21-day feeding period, fluorescein isothiocyanate dextran (FITC-d) was administered to chicks by oral gavage to evaluate gastrointestinal leakage. Blood and duodenum samples were collected to assess serum biochemistry and histomorphology, respectively. Compared to the control group, chicks of the AF group significantly diminished weight gain (WG) and average daily feed intake (ADFI), and increased feed conversion ratio (FCR), mortality rate (MR), and intestinal lesion scores (p < 0.05). Alterations in some serum biochemical parameters, and damage to the intestinal integrity were also evident in the AF-intoxicated birds. YCW supplementation improved WG and FCR and increased villus height, villus area, crypt depth, and the number of goblet cells in villi. The effects of YCW on growth performance were not significant in chicks of the AF + YCW group; however, the treatment decreased MR and significantly ameliorated some biochemical and histomorphological alterations. The beneficial effect of YCW was more evident in promoting gut health since chickens of the AF + YCW group presented a significant reduction in serum FITC-d concentration. This positive effect was mainly related to the changes in negative charges of YCW due to changes in pH, the net negative surface charge above the pHpzc, the higher quantities of negative charged functional groups on the YCW surface, and its ability to form large aggregates. From these results, it can be concluded that YCW at low supplementation level can partially protect broilers' intestinal health from chronic exposure to AFB1.
Takumi Nagasawa, Mitsuaki Ohta, Hidehiko Uchiyama
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.680843

Research to assess the relationship between cats and humans is in a nascent stage. Some studies have assessed the stress status in cats using physiological indicators, such as the cortisol hormone, but have not focused on the social interaction with humans. Moreover, the role of oxytocin secretion in the relationship between cats and humans remains unclear. In this study, we determined the possibility of quantifying the urinary concentration of oxytocin in cats and assessed the effects of social contact with humans on the levels of urinary oxytocin and cortisol metabolite. Four cats were subjected to two conditions, namely, social (control), and non-social (no social contact with humans) conditions. The levels of cortisol and oxytocin metabolite in urine samples from the cats in both conditions were determined using enzyme-linked immunosorbent assays. The urinary concentrations of cortisol and oxytocin under the non-social condition were significantly higher than those under the social condition. In addition, the concentration of oxytocin significantly correlated with that of cortisol in cats under the non-social condition. In this study, it was possible to quantify the concentration of oxytocin in the urine of cats, and the obtained results suggest that cats recognize the social interaction with humans as important. This information might contribute to the establishment of an assessment method for the welfare of cats and might help in clarifying the relationship between cats and humans.
Léa Cappelaere, Josselin Le Cour Grandmaison, Nicolas Martin,
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.689259

Poultry and swine farming are large contributors to environmental impacts, such as climate change, eutrophication, acidification, and air and water pollution. Feed production and manure management are identified as the main sources of these impacts. Reducing dietary crude protein levels is a nutritional strategy recognized to both decrease the use of high-impact feed ingredients and alter manure composition, reducing emissions of harmful components. For a successful implementation of this technique, feed-grade amino acid supplementation is crucial to maintaining animal performance. Reducing crude protein lowers nitrogen excretion, especially excess nitrogen excreted in urea or uric acid form, improving nitrogen efficiency. At the feed-gate, low–crude protein diets can reduce the carbon footprint of feed production through changes in raw material inclusion. The magnitude of this reduction mainly depends on the climate change impact of soybean meal and its land-use change on the feed-grade amino acids used. Reducing dietary crude protein also lowers the environmental impact of manure management in housing, storage, and at spreading: nitrogen emissions from manure (ammonia, nitrates, nitrous oxide) are reduced through reduction of nitrogen excretion. Moreover, synergetic effects exist with nitrogen form, water excretion, and manure pH, further reducing emissions. Volatilization of nitrogen is more reduced in poultry than in pigs, but emissions are more studied and better understood for pig slurry than poultry litter. Ammonia emissions are also more documented than other N-compounds. Low–crude protein diets supplemented with amino acids is a strategy reducing environmental impact at different stages of animal production, making life cycle assessment the best-suited tool to quantify reduction of environmental impacts. Recent studies report an efficient reduction of environmental impacts with low–crude protein diets. However, more standardization of limits and methods used is necessary to compare results. This review summarizes the current knowledge on mitigation of environmental impacts with low–crude protein diets supplemented with amino acids in poultry and swine, its quantification, and the biological mechanisms involved. A comparison between pigs and poultry is also included. It provides concrete information based on quantified research for decision making for the livestock industry and policy makers.
Jiayuan Mo, Le Sun, Juanru Cheng, Yujie Lu, Yaochang Wei, Guangsheng Qin, , Ganqiu Lan
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.679947

Follicular atresia is one of the main factors limiting the reproductive power of domestic animals. At present, the molecular mechanisms involved in porcine follicular atresia at the metabolic level remain unclear. In this study, we divided the follicles of Bama Xiang pigs into healthy follicles (HFs) and atretic follicles (AFs) based on the follicle morphology. The expression of genes related to atresia in granulosa cells (GCs) and the concentration of hormones in the follicular fluid (FF) from HFs and AFs were detected. We then used liquid chromatography–mass spectrometry-based non-targeted metabolomic approach to analyze the metabolites in the FF from HFs and AFs. The results showed that the content of estradiol was significantly lower in AFs than in HFs, whereas that of progesterone was significantly higher in AFs than that in HFs. The expression of BCL2, VEGFA, and CYP19A1 was significantly higher in HFs than in AFs. In contrast, the expression of BAX and CASPASE3 was significantly lower in HFs. A total of 18 differential metabolites (DMs) were identified, including phospholipids, bioactive substances, and amino acids. The DMs were involved in 12 metabolic pathways, including arginine biosynthesis and primary bile acid biosynthesis. The levels of eight DMs were higher in the HF group than those in the AF group (p < 0.01), and those of 10 DMs were higher in the AF group than those in the HF group (p < 0.01). These findings indicate that the metabolic characteristics of porcine AFs are lower levels of lipids such as phospholipids and higher levels of amino acids and bile acids than those in HFs. Disorders of amino acid metabolism and cholic acid metabolism may contribute to porcine follicular atresia.
, Arian Sadeghi, Emma Eriksson, Thomas Segall, Maria Dimopoulou, Olle Korsgren, Angelica Si. Loskog, Thomas H. Tötterman, Akseli Hemminki, Henrik Ronnberg
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.695222

Malignant melanoma is a serious disease in both humans and dogs, and the high metastatic potential results in poor prognosis for many patients. Its similarities with human melanoma make spontaneous canine melanoma an excellent model for comparative studies of novel therapies and tumor biology. Gene therapy using adenoviruses encoding the immunostimulatory gene CD40L (AdCD40L) has shown promise in initial clinical trials enrolling human patients with various malignancies including melanoma. We report a study of local AdCD40L treatment in 32 cases of canine melanoma (23 oral, 5 cutaneous, 3 ungual and 1 conjunctival). Eight patients were World Health Organization (WHO) stage I, 9 were stage II, 12 stage III, and 3 stage IV. One to six intratumoral injections of AdCD40L were given every seven days, combined with cytoreductive surgery in 20 cases and only immunotherapy in 12 cases. Tumor tissue was infiltrated with T and B lymphocytes after treatment, suggesting immune stimulation. The best overall response based on result of immunotherapy included 7 complete responses, 5 partial responses, 5 stable and 2 progressive disease statuses according to the World Health Organization response criteria. Median survival was 285 days (range 20–3435 d). Our results suggest that local AdCD40L therapy is safe and could have beneficial effects in dogs, supporting further treatment development. Clinical translation to human patients is ongoing.
, Carolee A. Carson, Miguel A. Moreno
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.728267

Editorial on the Research Topic Antimicrobial Usage in Companion and Food Animals: Methods, Surveys and Relationships with Antimicrobial Resistance in Animals and Humans, Volume II The best way to quantify antimicrobial use (AMU) in animals has raised wide research interests over the past years. Following the success of the first edition of the Research Topic on “Antimicrobial Usage in Companion and Food Animals: Methods, Surveys, and Relationships with Antimicrobial Resistance in Animals and Humans” Moreno et al., a second edition was launched. The objective was to continue the discussion on AMU metrics and expand the topic to other geographical regions (beyond North American and European Union countries), as well as other animal species (other than cattle, pigs, poultry, cats, or dogs). A total of 14 articles contributed to this collection, including 12 original research papers and two review papers. Among the original research papers, geographical areas covered included Europe (n = 8), North America (n = 2), and Asia (n = 2). Animal species covered included pigs (n = 5), poultry (n = 4), multiple animal species (n = 3), dairy cattle (n = 1), dogs (n = 1), finfish aquaculture (n = 1), and horses (n = 1). Out of the various research questions proposed in the Research Topic scope, the large majority of contributing studies aimed to compare different metrics to characterize AMU in animals (n = 10), while others primarily intended to compare AMU between countries (n = 4), between animal populations or farms, i.e., benchmarking (n = 3), or to monitor AMU trends over time (n = 1). None of the published studies addressed the aspects of linking AMU to antimicrobial resistance (AMR), or linking AMU between human and animal sectors, suggesting there is still room for more integrated and One Health approaches in the AMU metrics area. Most studies relied on end-user (farms or veterinarians) data (n = 12), while only a few studies relied on national (n = 1) or supra-national data (n = 1). This suggests a recent shift from national to end-user data, which are closer to “actual” AMU. Interestingly, this shift was also described by Sanders et al. who reported the development of multiple farm-level monitoring systems in Europe and Canada over the recent years. These are public or private monitoring programs (~50% each), which for some of them manage to achieve full sector coverage. Sanders et al. also reviewed the different AMU indicators being used by farm-level monitoring systems, defined as the amounts of antimicrobials consumed (numerator) normalized by the population at risk of being treated in a defined period of time (denominator). The authors demonstrated a clear lack of harmonization between farm-level indicators across countries and systems. The same observation was made by Narbonne et al. who systematically reviewed AMU indicators in finfish aquaculture. In addition, the calculation of AMU indicators in finfish aquaculture raised specific issues, e.g. related to the lack of average weight at treatment available in this sector. Several contributing studies quantified the gap between different indicators applied to the same dataset, and discussed the impact this had on the study results. Depending on the indicator applied to broiler chicken and turkey farm-level data, Agunos et al. observed variations in reported quantity of use, temporal trends, and relative ranking of the antimicrobials. Discrepancies were also observed by Kuemmerlen et al. and O'Neill et al. when ranking Swiss and Irish pig farms using various AMU indicators, highlighting the fact that different methods of measuring AMU can affect a benchmarking system. Discrepancies appeared higher when comparing weight-based vs. dose-based metrics, while comparisons within dose-based metrics appeared relatively concordant. Similarly, Schnepf et al. reported little deviation when comparing Used Daily Doses with Defined Daily Doses in horses presented at a veterinary university clinic in Germany. Comparisons between populations, e.g., between countries, could be improved by applying a standardization procedure to correct for differences in the composition of livestock demographics, as suggested by Hommerich et al. Some contributing studies also explored associations between AMU quantities and farm management practices. Caekebeke et al. studied associations between AMU and biosecurity levels in broilers and pig farms in Belgium and the Netherlands, and showed that Dutch farms overall had higher biosecurity and lower AMU than Belgian farms. In addition, Echtermann et al. reported positive significant associations between AMU and farm size, as well as between AMU in sows and piglets in Swiss farrow-to-finish pig farms. Olmos Antillón et al. explored variations in AMU between conventional and organic dairy farms in Sweden; while AMU for injectable and lactating cow intramammary treatments statistically differed between production systems, no difference was found for dry-cow therapies. One study by Redding et al. looked at perceptions of AMU indicators by small and large animal veterinarians in the USA. While respondents were quite positive about being part of a benchmarking system, they also reported AMU indicators, and especially dose-based indicators to be confusing, and recommended further guidance on how to interpret the metrics. Hence, the authors stressed the importance of selecting AMU indicators that are meaningful to clinicians for AMU monitoring to have a positive impact on antimicrobial stewardship. Beyond generating meaningful indicators, the issue of accessing detailed data that are necessary to calculate advanced indicators such as dose-based indicators was also raised. In their longitudinal study on AMU in Spanish dogs, Méndez and Moreno called for a pragmatic approach to use the simplest indicators based on the most frequently available information, as a compromise for permitting...
, Emily Awuor Ouma, Nadhem Mtimet, Gideon Aiko Obare
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.611298

The dairy sector in Rwanda plays a key role in improving nutrition and generating income mostly for rural households. Despite the Rwandan 1994 genocide that left around 80% of dairy cows decimated, the dairy sector has experienced significant growth in the past two decades through government, development organisations, and donor programs, and through the nascent vibrant public–private partnership. In this paper, we reviewed and documented the evolution of the dairy policies, programs, and regulations in Rwanda and how they have contributed to the development of the dairy sector. The policy change has impacted the provision and use of inputs and services that have shaped the sector's milk production and productivity, milk quality, and demand. The results suggest that various policy- and program-level interventions have positively contributed to the growth of the dairy sector and improved the livelihoods of low-income households. This has been achieved through increased access to inputs and services, enhanced capacities of the public and private sector to deliver services, strengthened dairy cooperatives' governance, and increased value proposition to members of various farmer groups and promotion of milk consumption. We find that some of the implemented policies and programs, such as the “Girinka” (one cow per poor family) program, Rwanda Dairy Competitiveness Program II, and Rwanda Dairy Development Project, have resulted in improved farmer access to improved cow breeds and improved milk quality and cow productivity through enhanced health inputs and other services. While the dairy policies, programs, and regulations in Rwanda have paved the way for the development of the dairy sector and contributed to the provision and use of inputs and services, there are still challenges that need to be addressed. Accessibility and use of veterinary and artificial insemination services are limited by the quality of veterinary products, while the inadequate quality of feeds leads to low productivity of improved cow breeds. Consequently, farmers' uptake and use of inputs and services can be enhanced through a strengthened capacity of milk collection centres and health and animal feed policies that guide and control the quality of veterinary products and feeds sold in the markets.
, Barry J. Bradford, Robert P. Rhoads
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.732203

Editorial on the Research Topic Impact of Climate Change on Immune Responses in Agricultural Animals Livestock production and welfare currently face critical challenges from climate change and global warming that will continue in the future with the predicted increase in the frequency and intensity of heat waves. Filipe et al. aptly described climate change as a very complex problem existing at a global level. Climate change contributes to the impairment of animal welfare and health both by the spread of vector-borne diseases and by its impact on the immune system of the animals, inducing immune suppression and increasing the susceptibility of animals to infections. In livestock, high-yielding animals, characterized by an accelerated metabolism and genetic selection based on production level in near-optimal conditions, may be the most endangered by climate change and the least resilient (1, 2). Based on this, the impact of climate change on production and reproduction of livestock will cause important economic losses (Filipe et al.). The genetic selection of livestock to address immune challenges in the face of more frequent heat stress can be an opportunity. As a result, Filipe et al. suggests that the valorisation of autochthonous livestock breeds known to be highly resilient and disease resistant, to have low dietary needs (acceptable production levels despite frugal rations) and to produce high quality products could be a strategy for future livestock management. Alterations in immune responses are observed in many species under heat stress; in broiler chickens, a particular sensitivity of lymphoid tissues to heat stress has been observed, with a depression of antigen-specific humoral immune responses, a substantial decrease in the number of splenic lymphocytes, and a decrease in immature B cells in bursal follicles. Hirakawa et al. suggest that the alteration in immune responses measured in broiler chicken under heat stress can be related to reduced feed intake and to insufficient macro-energy sources and/or micro-nutrients delivered to the lymphoid tissues, resulting in the incomplete proliferation and differentiation of T and B cells. As a matter of fact, the maintenance of tissue-specific homeostasis requires sufficient amounts of nutrients (e.g., glucose, fatty acids, amino acids, minerals, and vitamins) to meet the specific tissue requirements. The insufficient nutritive supply to primary and secondary lymphoid tissue induced by heat stress may cause pathological atrophy of tissues, reducing lymphocyte number and degrading functional structures. However, one of the species most negatively affected by heat stress is cattle, and particularly dairy cows during their entire life cycle, as documented in the extensive review by Dahl et al.. Heat stress impacts cows starting from gestation, when elevated maternal temperatures can be detrimental to embryonic and fetal development by altering cell proliferation, migration, differentiation, and programmed cell death. These effects are probably attributed to altered nutrient partitioning responsible for restricting the ontogeny of the fetal immune system. Maternal hyperthermia during early stages of fetal development may impact the differentiation, migration, and/or establishment of the highly proliferative pool of lymphoid-hematopoietic progenitor cells that are destined to become immune cells. In addition, the postnatal period is critical for the passive transfer of immunity; prenatal heat stress impairs passive transfer of colostral IgG. Newborn calves from heat-stressed dams, fed colostrum from their respective mothers, have reduced apparent efficiency of IgG absorption, compared with calves born to cooled dams and receiving their dam's colostrum, thus compromising the immune function of offspring from birth through weaning (3). Heifers also suffer from hyperthermia as their ability to dissipate metabolic heat gradually decreases, resulting in reduced heat tolerance during heifer development. Negative impacts of heat stress on lactational performance are well-known, but heat stress also has substantial impacts on a mature dairy cow's immune function and health, as suggested by the association of summer season with increased disease incidence. Finally, recent studies provide solid evidence that during the dry period, heat stress has significant negative effects on innate and adaptive immune function of both the dam and the offspring, influencing the morbidity and mortality of early lactation cows and calves from birth to first calving. Heat abatement by physical modification of the environment is an effective and profitable strategy to manage heat stress in dairy cattle leading to successful outcomes that minimize the negative impacts of heat stress on animal health. Although heat abatement for mature dairy cows, especially those housed in barns, has been extensively studied, additional effort is needed to develop effective and affordable cooling strategies for grazing dairy cattle, preweaned calves, and growing heifers to maintain immune function and optimal performance of these animals under field conditions. In a retrospective study, Broadway et al. found no correlation between summer temperature patterns and cattle morbidity/mortality in feedlots in the Texas Panhandle. However, some of the negative effects of heat stress observed in a controlled study appeared to be mitigated by prophylactic yeast and yeast cell wall supplementation in nearly finished beef cattle. Heifers supplemented with a combined live yeast and yeast cell wall product had decreased vaginal temperature and respiration rate and increased water intake in comparison to non-supplemented control heifers (Broadway et al.). In contrast to cattle, the dromedary camel can be considered a model of different immune reactivity to heat stress, thus helping to better understand thermotolerance mechanisms developed in livestock adapted to hot climates. In his manuscript,...
Jv Zhang, Juncai Chen, Qianjun Huang, Brett MacKinnon, Omid Nekouei, Hong Liu, Peng Jia, Jinjin Wang, Na Li, Liqing Huang, et al.
Frontiers in Veterinary Science, Volume 8; doi:10.3389/fvets.2021.689085

Copper-based fungicides have a long history of usage in agriculture and aquaculture. With the rapid development of metal-based nanoparticles, copper-based nanoparticles have attracted attention as a potential material for prevention and control of Saprolegnia parasitica. The present study investigated the effectiveness of copper/carbon core/shell nanoparticles (CCCSNs) and a commercial CCCSNs filter product (COPPERWARE®) against S. parasitica in a recirculating system. Results showed that the growth of agar plugs with mycelium was significantly suppressed after exposure to both CCCSNs powder and COPPERWARE® filters. Even the lowest concentration of CCCSNs used in our study (i.e., 100 mg/mL) exhibited significant inhibitory effects on S. parasitica. The smallest quantity of the filter product COPPERWARE® (3.75 × 3.7 × 1.2 cm, 2.58 g) used in our aquarium study also demonstrated significant inhibition compared with the control group. However, we observed leaching of copper into the water especially when larger quantities of COPPERWARE® were used. Water turbidity issues were also observed in tanks with the filter material. Besides these issues, which should be further investigated if the product is to be used on aquatic species sensitive to copper, CCCSNs has promising potential for water disinfection.
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