Host transcriptome response to heat stress and Eimeria maxima infection in meat-type chickens.

Eimeria (E.) maxima parasite infects chickens' midgut disrupting the jejunal and ileal mucosa causing high morbidity and mortality. Heat stress (HS) is a seasonal stressor that impacts biological functions leading to poor performance. This study elucidates how HS, E. maxima infection, and their combination affect the ileum transcriptome. Two-hundred and forty 2-week-old males Ross708 chickens were randomly allocated into four treatment groups: thermoneutral-control (TNc), thermoneutral-infected (TNi), heat-stress control (HSc), and heat stress-infected (HSi), with 6 replicates each of 10 birds. Infected groups received 200x103 sporulated E. maxima oocysts/bird, and heat-treated groups were raised at 35°C. At 6-day post-treatment, ileums of five randomly selected chickens per group were sampled, RNA was extracted and sequenced. A total of 413, 3377, 1908, and 2304 DEGs were identified when applying the comparisons: TNc vs HSc, TNc vs TNi, HSi vs HSc, and TNi vs HSi, respectively, at cutoff ≥1.2-fold change (FDR: q<0.05). HSc vs TNc showed upregulation of lipid metabolic pathways and degradation/metabolism of multiple amino acids; and downregulation of most immune-related and protein synthesis pathways. TNc vs TNi displayed upregulation of most of immune-associated pathways and eukaryotic mRNA maturation pathways; and downregulation of fatty acid metabolism and multiple amino acid metabolism pathways including tryptophan. Comparing HSi versus HSc and TNi revealed that combining the two stressors restored the expression of some cellular functions, e.g., oxidative phosphorylation and protein synthesis; and downregulate immune response pathways associated with E. maxima infection. During E. maxima infection under HS the calcium signaling pathway was downregulated, including genes responsible for increasing the cytoplasmic calcium concentration; and tryptophan metabolism was upregulated, including genes that contribute to catabolizing tryptophan through serotonin and indole pathways; which might result in reducing the cytoplasmic pool of nutrients and calcium available for the parasite to scavenge and consequently might affect the parasite's reproductive ability.

Effect of Glucose Supplementation on Apoptosis in the Pectoralis major of Chickens Raised under Thermoneutral or Heat Stress Environment.

Reduced feed intake during heat stress (HS) disrupts glucose homeostasis, thereby resulting in endoplasmic reticulum (ER) stress and triggering apoptosis in chickens. We hypothesize that glucose supplementation could reduce apoptosis in chickens raised under HS. This study comprised 456 28-day-old broiler chickens randomly assigned to four treatment combinations under glucose supplementation and HS. The treatments were TN0, TN6, HS0, and HS6 with two glucose levels (0% and 6%) and two temperature levels (25 °C (thermoneutral-TN) and 35 °C (8.00 AM to 8.00 PM, (HS)). After 7 days post-HS, the blood glucose level for the HS6 group was higher than for TN0, TN6, and HS0. We studied the mRNA expression of genes and caspase-3 activity in the four experimental groups. The expressions of GCN2, ATF4, CHOP, and FOXO3a increased during HS regardless of glucose supplementation, while PERK and MAFbx increased only under HS with glucose supplementation. We show that under TN conditions, glucose supplementation led to a significant increase in cellular apoptosis in the Pectoralis (P.) major. However, under HS with glucose, the level of apoptosis was similar to that of chickens raised under TN conditions with no glucose supplementation. The utility of glucose to curtail apoptosis under HS should be tested under other intense models of HS.

Glucose Supplementation Improves Performance and Alters Glucose Transporters' Expression in Pectoralis major of Heat-Stressed Chickens.

Glucose level in birds' tissue decreases due to heat stress (HS)-induced reduction in feed intake (FI); impairing metabolism and growth. The effect of glucose supplementation on the performance of broiler chickens was evaluated under thermoneutral (TN) and HS conditions. Glucose was supplemented at 0 and 6% under TN-(25 °C) and HS-(25 °C-35 °C-25 °C) conditions. The treatments were TN + 0%-glucose (TN0); TN + 6%-glucose (TN6), HS + 0%-glucose (HS0) and HS + 6%-glucose (HS6). There were 6 replicates (19 birds each)/treatment. Heat and glucose supplementation were applied from d28-35. At d35, Pectoralis (P.) major was sampled from one bird/replicate to determine glucose transporters' mRNA expression. Heat application lowered (p < 0.05) FI, body weight gain, and increased feed and water conversion ratios. Glucose supplementation increased total energy intake by 4.9 and 3.2% in TN and HS groups, respectively but reduced FI under TN and HS conditions. The P. major- and drumstick-yield reduced (p < 0.05) in HS0 compared to TN0, TN6 and HS6. Under HS, glucose supplementation improved eviscerated carcass weight by 9% and P. major yield by 14%. Glucose supplementation increased SGLT1 expression with/without heat treatment while HS independently increased the expression of GLUT 1, 5 and 10. Glucose supplementation under HS could improve performance of broilers.

Growth Rate Distribution and Potential Non-Linear Relationship between Body Weight and Walking Ability in Turkeys.

The aim of this study was to investigate the potential non-linear relationship between growth and walking ability (WA). The phenotypic data included body weights at 12 and 20 weeks and WA at 20 weeks of age measured on 276,059 male turkeys. The growth rate at three age periods (0 to 12, 12 to 20 and 0 to 20 weeks) was calculated. Each bird was assigned to one of the quartiles of the growth rate distribution for each age period. Between the first and fourth quartiles, the incidence of score 1 (bad WA) increased by 31, 18, and 33% for the first, second, and third age periods, respectively. For good WA (scores 4, 5, and 6), the incidence decreased by 55, 66, and 72% between the first and fourth quartiles for the first, second, and third age periods, respectively. Estimates of heritability of WA ranged between 0.18 and 0.26. The genetic correlations between adjacent growth rate quartiles were high and decayed as the interval between quartiles increased. The magnitude of the variation in the incidence of walking scores and genetic correlations across the growth rate quartiles point towards a non-linear relationship between growth and mobility suggesting other factors may affect walking ability.

Quantitative and molecular aspects of water intake in meat-type chickens.

Even though water is the most essential nutrient for poultry production, adequate data on individual water intake in broiler chickens and its relationship with other traits of economic importance is scant. Water is provided to chickens in an unrestricted manner in spite of being a finite resource. Climate change continues to affect water sources and efficient bird use of water is long overdue. Understanding the biological basis of water intake is essential for sustainability of the poultry industry. Individual water and feed intake, and growth data was collected on 520 commercial broilers aged 14 to 42 days. We introduced the concepts of water conversion ratio (WCR) and residual water intake (RWI) as parameters that can be used to assess water intake efficiency. Water conversion ratio was defined as the amount of water consumed per unit of body weight gain, and RWI was defined as the difference between the actual water intake (WI) of a given bird and the expected WI by an average bird from the population with the same metabolic body weight, feed intake (FI) and body weight gain (BWG). The correlation between WI and FI was positive (r=0.77; P<0.0001), and the correlation between WI and BWG was positive (r=0.80; P<0.0001). Based on the distribution of RWI, the bottom 5 birds (LRWI) and the top 5 birds (HRWI) for RWI were selected for mRNA expression differences. The average broiler consumed about 7.8 L (± 1L) of water from 14 to 42 days of age. The mRNA expression of arginine vasopressin (AVP) antidiuretic hormone, calcium sensing receptor (CasR), sodium channel epithelial 1 subunit alpha (SCNN1A) and SCNN1D in the hypothalamus was upregulated in the LRWI group compared to the HRWI group. Similarly, kidney aquaporins (AQP) 2, 3, and 4 were upregulated in the LRWI group compared with the HRWI group. Given that water was provided ad libitum, the up-regulation of AVP and AQP gene mRNA expressions seem to indicate that the LRWI birds were more efficient in water reabsorption in the kidney compared to their HRWI counterparts. Increased water reabsorption will reduce the amount of water consumed to attain hydration. The water reabsorption potential was reflected in the excreta moisture levels as the LRWI birds had significantly lower excreta moisture than the HRWI birds. Excreta moisture level require further studies and could be considered as a potential proxy trait for water intake.

Research Note: Analysis of body weight and walking ability in turkeys and the prediction of categorical responses across systematic effect classes using a linear threshold model.

Heavy selection for growth in turkeys has led to a decay in leg soundness and walking ability. In this study, different models and traits were used to investigate the genetic relationships between body weight (BW) and walking ability (WA) in a turkey population. The data consisted of BW and WA traits collected on 276,059 male birds. Body weight was measured at 12 and 20 wk and WA at 20 wk of age. For WA, birds were scored based on a 1 (bad) to 6 (good) grading system. Due to the small number of records with scores 5 and 6, birds with WA scores of 4, 5, and 6 were grouped together resulting in only 4 classes. Additionally, a binary classification of WA (scores 1 and 2 = Similarly, an estimate of the genetic correlation between WA and BW at 20 wk was -0.45, indicating a more pronounced class 1; scores 3, 4, 5, and 6 = class 2) was evaluated. The inheritability estimates of WA ranged between 0.25 and 0.27 depending on the number of classes. The Heritability of BW at 12 and 20 wk was 0.44 and 0.51, respectively. The genetic correlation between WA and BW at 12 wk was around -0.35, indicating that heavy birds tend to have poor WA. antagonistic relationship between BW and WA. The genetic correlation between BW at 12 and 20 wk was positive and high (0.80). The residual correlation between WA and BW at 12 and 20 wk of age was -0.07 and -0.02, respectively. The residual correlation between body weight traits was 0.57. Similar results were observed when a binary classification was adopted for WA. The probability of an individual with a given genetic merit expressing a certain class of WA was determined for different fixed effect designations. Predictive probabilities clearly showed that birds when hatched in the winter would have a small chance to exhibit good WA phenotypes.

Fuzzy Logic as a Strategy for Combining Marker Statistics to Optimize Preselection of High-Density and Sequence Genotype Data.

The high dimensionality of genotype data available for genomic evaluations has presented a motivation for developing strategies to identify subsets of markers capable of increasing the accuracy of predictions compared to the current commercial single nucleotide polymorphism (SNP) chips. In this simulation study, an algorithm for combining statistics used in the preselection and prioritization of SNP markers from a high-density panel (1.3 million SNPs) into a composite "fuzzy" ranking score based on a Sugeno-type fuzzy inference system (FIS) was developed and evaluated for performance in preselection for genomic predictions. FST scores, and p-values were evaluated as inputs for the FIS. The accuracy of genomic predictions for fuzzy-score-preselected panel sizes of 1-50 k SNPs ranged from -0.4-11.7 and -0.3-3.8% higher than FST and p-value preselection, respectively. Though gains in prediction accuracies using only two inputs to the FIS were modest, preselection based on fuzzy scores yielded more accurate predictions than both FST scores and p-values for the majority of evaluated panel sizes under all genetic architectures. FIS have the potential to aggregate information from multiple criteria that reflect SNP-trait associations and biological relevance in a flexible and efficient way to yield higher quality genomic predictions.

Thrombin as a Potential Proxy to Select for Horn Fly Abundance in Beef Cattle.

Horn flies are a major nuisance to cattle and induce significant economic losses. Fly abundance varies within and across breeds and genetic analyses have shown sufficient genetic variation to permit selection. A major bottleneck for selecting against horn fly abundance is the complexity of measuring fly attraction phenotypes. Easy-to-measure proxy phenotypes could be an attractive option to indirectly estimate fly abundance. In the current study, thrombin was investigated as a potential proxy to assess fly abundance. Fly counts and blood samples were collected on 355 cows. Pearson correlation between subjective fly count and thrombin was -0.13, indicating a decrease in fly abundance with the increase in thrombin concentration. When thrombin was discretized into three classes, there was a 22% difference in fly count between the top and bottom classes. Heritability estimates of thrombin were 0.38 and 0.39 using linear and threshold models, respectively. The correlation between estimated thrombin breeding values and fly count was around -0.18. There was a noticeably lower density of high fly counts among animals with high breeding values for thrombin. These results indicate that thrombin could be used in combination with other biological factors to estimate fly abundance and as a proxy for selection against fly abundance.

Heat stress modulates the disruptive effects of Eimeria maxima infection on the ileum nutrient digestibility, molecular transporters, and tissue morphology in meat-type chickens.

Eimeria (E.) maxima is one of the most pathogenic Eimeria spp persistently invading the middle jejunum and ileum, damaging the intestinal mucosa of chickens. Heat stress (HS) is a common stressor and equally contributes to inflammation and oxidative stress. We investigated the effect of E. maxima infection and HS on ileal digestibility, mRNA expression of nutrient transporters, and ileal tissue morphology in broiler chickens. There were four treatment groups: thermoneutral control (TNc), thermoneutral infected (TNi), heat stress control (HSc), and heat stress infected (HSi), 6 replicates each of 10 birds per treatment. Chickens were fed a diet containing 0.2% TiO2. At 6-day-post infection, ileal content and tissue were collected to quantify ileal digestibility of crude protein and fat, mRNA levels of nutrient transporters and histopathology. Growth and feed intake were reduced in all treatment groups, compared with the TNc. Contrary to expectation, the combination of two major stressors (E. maxima and HS) in the TNi group exhibited almost normal digestibility while only the TNi birds expressed severe digestibility depression, compared with the TNc group. The TNi group showed the lowest mRNA expression of the transporters: SGLT1, GLUT2-5-8-10-12, FABP1-2-6, and PEPT1 compared with the other treatment groups. The expression of the absorptive enterocytes' gene markers (ACSL5, IAP, and SGLT1) supported by the ileal tissue morphology indicated that the TNi group had the highest enterocytic destruction. The expression of oxidative genes (iNOS and CYBB) dramatically increased only in the TNi group compared with the other treatment groups. Our results showed that exposing broiler chickens to HS can mitigate the disruptive effect of E. maxima on the ileal digestibility and absorption by limiting the parasite-induced tissue injury and suppressing the enterocytic inducible oxidative damage.

Heat Stress Alters the Effect of Eimeria maxima Infection on Ileal Amino Acids Digestibility and Transporters Expression in Meat-Type Chickens.

Eimeria (E.) maxima invades the midgut of chickens and destroys the intestinal mucosa, impacting nutrient digestibility and absorption. Heat stress (HS) commonly affects the broiler chicken and contributes to inflammation and oxidative stress. We examined the independent and combined effects of HS and E. maxima infection on apparent amino acid ileal digestibility (AID) and mRNA expression of amino acid transporters in broiler chickens (Ross 708). There were four treatment groups: thermoneutral-control (TNc) and infected (TNi), heat-stress control (HSc) and infected (HSi), six replicates of 10 birds/treatment. Ileal content and tissue were sampled at 6 d post infection to determine AID and transporters expression. Surprisingly, the HSi chickens exposed to two critical stressors exhibited normal AID. Only the TNi group displayed reduction in AID. Using TNc as control, the HSc group showed upregulated CAT1, LAT4, TAT1, SNAT1, and SNAT7. The HSi group showed upregulated CAT1 and LAT1, and downregulated b0,+AT, rBAT, SNAT1, and SNAT2. The TNi group showed upregulated CAT1, LAT1, and SNAT1 and downregulated B0AT1, b0,+AT, rBAT, LAT4, and TAT1. The expression of all enterocytic-apical and about half of the basolateral transporters was higher in the HSi group than in the TNi group, indicating that HS can putatively alleviate the E. maxima adverse effect on ileal digestion and absorption.

Dissection of the impact of prioritized QTL-linked and -unlinked SNP markers on the accuracy of genomic selection1.

BACKGROUND: Use of genomic information has resulted in an undeniable improvement in prediction accuracies and an increase in genetic gain in animal and plant genetic selection programs in spite of oversimplified assumptions about the true biological processes. Even for complex traits, a large portion of markers do not segregate with or effectively track genomic regions contributing to trait variation; yet it is not clear how genomic prediction accuracies are impacted by such potentially nonrelevant markers. In this study, a simulation was carried out to evaluate genomic predictions in the presence of markers unlinked with trait-relevant QTL. Further, we compared the ability of the population statistic FST and absolute estimated marker effect as preselection statistics to discriminate between linked and unlinked markers and the corresponding impact on accuracy. RESULTS: We found that the accuracy of genomic predictions decreased as the proportion of unlinked markers used to calculate the genomic relationships increased. Using all, only linked, and only unlinked marker sets yielded prediction accuracies of 0.62, 0.89, and 0.22, respectively. Furthermore, it was found that prediction accuracies are severely impacted by unlinked markers with large spurious associations. FST-preselected marker sets of 10 k and larger yielded accuracies 8.97 to 17.91% higher than those achieved using preselection by absolute estimated marker effects, despite selecting 5.1 to 37.7% more unlinked markers and explaining 2.4 to 5.0% less of the genetic variance. This was attributed to false positives selected by absolute estimated marker effects having a larger spurious association with the trait of interest and more negative impact on predictions. The Pearson correlation between FST scores and absolute estimated marker effects was 0.77 and 0.27 among only linked and only unlinked markers, respectively. The sensitivity of FST scores to detect truly linked markers is comparable to absolute estimated marker effects but the consistency between the two statistics regarding false positives is weak. CONCLUSION: Identification and exclusion of markers that have little to no relevance to the trait of interest may significantly increase genomic prediction accuracies. The population statistic FST presents an efficient and effective tool for preselection of trait-relevant markers.

Molecular and Cellular Responses of DNA Methylation and Thioredoxin System to Heat Stress in Meat-Type Chickens.

Heat stress (HS) causes molecular dysfunction that adversely affects chicken performance and increases mortality. The responses of chickens to HS are extremely complex. Thus, the aim of this study was to evaluate the influence of acute and chronic exposure to HS on the expression of thioredoxin-peroxiredoxin system genes and DNA methylation in chickens. Chickens at 14 d of age were divided into two groups and reared under either constant normal temperature (25 °C) or high temperature (35 °C) in individual cages for 12 days. Five birds per group at one and 12 days post-HS were euthanized and livers were sampled for gene expression. The liver and Pectoralis major muscle were sampled for cellular analysis. mRNA expression of thioredoxin and peroxiredoxins (Prdx) 1, 3, and 4 in the liver were down-regulated at 12 days post-HS compared to controls. The liver activity of thioredoxin reductase (TXNRD) and levels of peroxiredoxin1 (Prdx1) at 12 days post-HS were significantly decreased. The results reveal that there was a significant decrease in DNA methylation at 12 days post HS in liver tissues. In conclusion, pathway of thioredoxin system under HS may provide clues to nutritional strategies to mitigate the effect of HS in meat-type chicken.

Grid search approach to discriminate between old and recent inbreeding using phenotypic, pedigree and genomic information.

BACKGROUND: Although inbreeding caused by the mating of animals related through a recent common ancestor is expected to have more harmful effects on phenotypes than ancient inbreeding (old inbreeding), estimating these effects requires a clear definition of recent (new) and ancient (old) inbreeding. Several methods have been proposed to classify inbreeding using pedigree and genomic data. Unfortunately, these methods are largely based on heuristic criteria such as the number of generations from a common ancestor or length of runs of homozygosity (ROH) segments. To mitigate these deficiencies, this study aimed to develop a method to classify pedigree and genomic inbreeding into recent and ancient classes based on a grid search algorithm driven by the assumption that new inbreeding tends to have a more pronounced detrimental effect on traits. The proposed method was tested using a cattle population characterized by a deep pedigree. RESULTS: Effects of recent and ancient inbreeding were assessed on four growth traits (birth, weaning and yearling weights and average daily gain). Thresholds to classify inbreeding into recent and ancient classes were trait-specific and varied across traits and sources of information. Using pedigree information, inbreeding generated in the last 10 to 11 generations was considered as recent. When genomic information (ROH) was used, thresholds ranged between four to seven generations, indicating, in part, the ability of ROH segments to characterize the harmful effects of inbreeding in shorter periods of time. Nevertheless, using the proposed classification method, the discrimination between new and old inbreeding was less robust when ROH segments were used compared to pedigree. Using several model comparison criteria, the proposed approach was generally better than existing methods. Recent inbreeding appeared to be more harmful across the growth traits analyzed. However, both new and old inbreeding were found to be associated with decreased yearling weight and average daily gain. CONCLUSIONS: The proposed method provided a more objective quantitative approach for the classification of inbreeding. The proposed method detected a clear divergence in the effects of old and recent inbreeding using pedigree data and it was superior to existing methods for all analyzed traits. Using ROH data, the discrimination between old and recent inbreeding was less clear and the proposed method was superior to existing approaches for two out of the four analyzed traits. Deleterious effects of recent inbreeding were detected sooner (fewer generations) using genomic information than pedigree. Difference in the results using genomic and pedigree information could be due to the dissimilarity in the number of generations to a common ancestor. Additionally, the uncertainty associated with the identification of ROH segments and associated inbreeding could have an effect on the results. Potential biases in the estimation of inbreeding effects may occur when new and old inbreeding are discriminated based on arbitrary thresholds. To minimize the impact of inbreeding, mating designs should take the different inbreeding origins into consideration.

Evolvement of taste sensitivity and taste buds in chickens during selective breeding.

Chickens have been reported to have a low taste bud count and thus low taste acuity. However, more recent studies indicate that the earlier reported count of chicken taste buds may have been significantly underestimated. To answer the question of whether the taste sensing system in broiler chickens evolved during the breeding selection over the past decades, we compared the taste sensitivity to bitter and taste buds between a meat-type control strain - the 1955 Athens Canadian Random Bred (ACRB), and a modern high-yielding broiler strain - the 2012 Cobb 500. The behavioral tests showed that the ACRB did not avoid bitter taste solutions of quinine hydrochloride (QHCl) at the examined concentrations (0.5, 1, 2, and 4 mM) (P > 0.05), while the Cobb 500 significantly avoided both the 2 mM and 4 mM QHCl solutions (P < 0.01). The labeling of chicken taste buds using the molecular marker Vimentin revealed that Cobb 500 chickens had a slightly higher number (P < 0.1), but lower density of taste bud clusters in the palate (P < 0.01) and the base of the oral cavity (P < 0.05) compared to the ACRB. We also found that a single amino acid change occurred in the bitter taste receptor T2R7. However, the functional analyses using HEK293T cells transiently expressing T2R7 revealed that the functions of T2R7 were comparable between the two strains. Taken together, our results demonstrated that taste sensitivities could be affected by the selection of the broiler chickens. The modern high-yielding broilers, which have massive feed intake and appetite, had a higher sensitivity to bitter taste stimuli than the meat-type chicken strain which was established decades ago. This evolvement of taste sensitivities may be associated with the alterations of an upper level of taste system, rather than the peripheral taste system, including distribution of taste buds and functions of taste receptors.

Runs of homozygosity and analysis of inbreeding depression.

Pedigree information was traditionally used to assess inbreeding. The availability of high-density marker panels provides an alternative to assess inbreeding, particularly in the presence of incomplete and error-prone pedigrees. Assessment of autozygosity across chromosomal segments using runs of homozygosity (ROH) has emerged as a valuable tool to estimate inbreeding due to its general flexibility and ability to quantify the chromosomal contribution to genome-wide inbreeding. Unfortunately, the identification of ROH segments is sensitive to the parameters used during the search process. These parameters are heuristically set, leading to significant variation in the results. The minimum length required to identify an ROH segment has major effects on the estimation of inbreeding and inbreeding depression, yet it is arbitrarily set. To overcome this limitation, a search algorithm to approximate mutation enrichment was developed to determine the minimum length of ROH segments. It consists of finding genome segments with significant effect differences in trait means between animals with high and low burdens of autozygous intervals with a specific length. The minimum length could be determined heuristically as the smallest interval at which a significant signal is detected. The proposed method was tested in an inbred Hereford cattle population genotyped for 30,220 SNPs. Phenotypes recorded for six traits were used for the approximation of mutation loads. The estimated minimum length was around 1 Mb for yearling weight (YW) and average daily gain (ADG) and 4 Mb for birth weight and weaning weight. These trait-specific thresholds estimated using the proposed method could be attributed to a trait-dependent effect of homozygosity. The detection of significant inbreeding effects was well aligned with the estimated thresholds, especially for YW and ADG. Although highly deleterious alleles are expected to be more frequent in recent inbreeding (long ROH), short ROH segments (<5 Mb) could contain a large number of less deleterious mutations with substantial joint effects on some traits (YW and ADG). Our results highlight the importance of accurate estimation of the ROH-based inbreeding and the necessity to consider a trait-specific minimum length threshold for the identification of ROH segments in inbreeding depression analyses. These thresholds could be determined using the proposed method provided the availability of phenotypic information.

SARS-CoV-2 Receptor ACE2 Is Enriched in a Subpopulation of Mouse Tongue Epithelial Cells in Nongustatory Papillae but Not in Taste Buds or Embryonic Oral Epithelium.

As a result of the COVID-19 pandemic, evidence revealed that SARS-CoV-2 infection caused taste loss at a rate higher than that of influenza. ACE2, the entry receptor of SARS-CoV-2, has been identified in the oral epithelium; however, it is unclear at what developmental stage ACE2 expression emerges and whether ACE2 is expressed in taste buds. To identify the specific developmental stage, we analyzed RNA-Seq data from embryonic and newborn mouse oral tissue. We found that robust ACE2 expression was observed in the newborn oral epithelium. In contrast, only extremely low levels, if any, of ACE2 transcripts in the embryonic stage oral tissue were found (E12.5 and E14.5). Analyses of three public scRNA-seq data sets of adult mouse tongue epithelial cells showed that receptors for various viruses were enriched in distinct clusters of tongue epithelial cells. ACE2 was enriched in a subpopulation of epithelial cells in the basal region of nongustatory filiform papillae but not in the taste papillae or taste buds. Expression of ACE2 was detected in a small proportion of type III taste cells. Our results indicate that when applied across species, nongustatory papilla epithelial cells are the prime targets for SARS-CoV-2 infection in the tongue; thus, taste loss in COVID-19 patients is likely not caused by a direct infection of SARS-CoV-2 to taste bud cells. Additionally, fetuses at different stages of development may have distinct susceptibility to SARS-CoV-2 infection.

Heat stress reduces sexual development and affects pathogenesis of Eimeria maxima in meat-type chickens.

Coccidiosis, caused by Eimeria spp. presents a self-limiting intestinal infection of poultry. Intestinal replication of the parasite causes severe morphological alterations to the host gastrointestinal tract, marked, among others, by the disruption of the intestinal barrier. We have previously reported a significant reduction in merozoite replication and oocyst shedding in E. tenella in vitro and in vivo. The objective of this study was to investigate the pathogenesis of E. maxima infection in broiler chickens under heat stress (HS) and mRNA expression of host cytokines that might affect the curtailed development of the parasite. We herein demonstrate that there is a significant detrimental effect of HS on the pathogenesis of E. maxima infection in broilers. There was a restricted replication of the parasite in HS chickens evidenced by significantly reduced oocyst shedding and disruption of the intestinal blood barrier. Gene expression of parasite genes demonstrated curtailed sexual reproduction of E. maxima in HS chickens. There was downregulation of Eimeria spp. genes related to gamete fusion, oocyst shedding, mitosis and spermiogenesis. Host gene expression indicates alterations in the cytokine expression that could be related to reduced parasite development in vivo.

Dietary methionine level alters growth, digestibility, and gene expression of amino acid transporters in meat-type chickens.

Imbalance in nutrients can affect digestibility of amino acids by altering gene expression of amino acid transporters. We investigated digestibility and molecular transporters of essential amino acids in chickens fed a methionine-deficient diet. A total of 40 chicks (23 D old) were randomly assigned to either a control (0.49% methionine) or a deficient (0.28%) diet until 41 D when they were sampled for Pectoralis (P.) major, kidney, ileum, and hypothalamus for mRNA expression analysis. The ileal content was collected for apparent ileal digestibility (AID) analysis. Birds fed the deficient diet had reduced growth and worse feed efficiency compared to control. The AID of methionine was similar between both groups. The AID of other essential amino acids was higher in the deficient group than control. mRNA expression of b0,+ AT and LAT4 were upregulated in the ileum and kidney but LAT1 was downregulated only in kidney of the deficient group compared to control. In the P. major, SNAT1, SNAT2, and CAT1 were upregulated in the deficient group compared to control. A diet deficiency in methionine affects digestibility of essential amino acids and cysteine, but not the digestibility of methionine. The change in digestibility is reflected in the mRNA expression of amino acid transporters across different tissues.

Alteration of dietary cysteine affects activities of genes of the transsulfuration and glutathione pathways, and development of skin tissues and feather follicles in chickens.

The dietary requirement for cysteine is not determined in poultry since it is not an essential amino acid. The cysteine need is expected to be met through the transsulfuration pathway where homocysteine, a precursor of methionine, is converted to cysteine. Cysteine is a major component of plumage, and the degree to which cysteine is involved in plumage and other keratized proteins are unknown. We randomly assigned chicks to control and treatment (deficient in cysteine) diets for 49 d. The thickness of the skin layers, feather follicle length, and thickness were measured at days 10, 24, 34, and 49. We also measured the hepatic mRNA expressions of cystathionine beta synthase (CBS), cystathionine γ-lyase (CTL), cysteine dioxygenase (CDO), and glutathione synthetase (GSS). Chickens fed the treatment diet had reduced epidermis thickness and shorter feather follicles compared with the controls. The chicken fed the treatment diet also had increased mRNA expression of CBS and CTL indicating a disruption of the transsulfuration pathway. The treatment chickens also had a decreased hepatic CDO and increased GSS mRNA expressions which are in concordance with the homeostatic regulation of cysteine. Compromised cysteine metabolism could affect thermoregulation and subsequently affect feed efficiency and welfare of the birds.

A Weighted Genomic Relationship Matrix Based on Fixation Index (FST) Prioritized SNPs for Genomic Selection.

A dramatic increase in the density of marker panels has been expected to increase the accuracy of genomic selection (GS), unfortunately, little to no improvement has been observed. By including all variants in the association model, the dimensionality of the problem should be dramatically increased, and it could undoubtedly reduce the statistical power. Using all Single nucleotide polymorphisms (SNPs) to compute the genomic relationship matrix (G) does not necessarily increase accuracy as the additive relationships can be accurately estimated using a much smaller number of markers. Due to these limitations, variant prioritization has become a necessity to improve accuracy. The fixation index (FST) as a measure of population differentiation has been used to identify genome segments and variants under selection pressure. Using prioritized variants has increased the accuracy of GS. Additionally, FST can be used to weight the relative contribution of prioritized SNPs in computing G. In this study, relative weights based on FST scores were developed and incorporated into the calculation of G and their impact on the estimation of variance components and accuracy was assessed. The results showed that prioritizing SNPs based on their FST scores resulted in an increase in the genetic similarity between training and validation animals and improved the accuracy of GS by more than 5%.