Genome-wide association study of resistance/susceptibility to infectious bovine keratoconjunctivitis in Brazilian Hereford cattle

Genome-wide association studies were conducted to identify the more informative genomic regions and SNPs, as well as to identify candidate genes associated with infectious bovine keratoconjunctivitis (IBK) resistance/susceptibility in Hereford cattle. A Bayes B statistical approach was initially applied in genome-wide association studies by using deregressed estimated breeding values for IBK resistance/susceptibility. To estimate the combined effect of a genomic region that is potentially associated with QTL, 2504 non-overlapping 1-Mb windows that varied in SNP number were defined, with the most informative 24 windows including 427 SNPs and explaining more than 20% of the estimated genetic variance for IBK resistance/susceptibility. These regions were explored with respect to their biological functions through functional analysis to map potential candidate genes. The significant SNPs were mapped on chromosomes 1, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 18, 20, 23, and 28, and candidate genes were detected as related to the IBK. Most informative SNPs in term of genetic variance were located in proximity of genes related to phenotypic expression of lesions and biological processes associated to the IBK. Knowledge about phenotypic and genomic variation generated in the present study can be used to on design selection strategies to improve the resistance to IBK of Hereford cattle herds.

Methionine supplementation during a hydrogen peroxide challenge alters components of insulin signaling and antioxidant proteins in subcutaneous adipose explants from dairy cows

Enhanced postruminal supply of methionine (Met) during the peripartal period alters protein abundance of insulin, AA, and antioxidant signaling pathways in subcutaneous adipose tissue (SAT). Whether SAT is directly responsive to supply of Met and can induce molecular alterations is unknown. Our objective was to examine whether enhanced Met supply during an oxidative stress challenge in vitro alters insulin, AA, inflammation, and antioxidant signaling-related protein networks. Four late-lactation Holstein cows (average 27.0 kg of milk per day) were used for SAT collection. Tissue was incubated in duplicate for 4 h in a humidified incubator with 5% CO₂ at 37°C according to the following experimental design: control medium with an "ideal" profile of essential AA (CTR; Lys:Met 2.9:1), CTR plus 100 μM H₂O₂ (HP), or CTR with greater Met supply plus 100 μM H₂O₂ (HPMET; Lys:Met 2.5:1). Molecular targets associated with insulin signaling, lipolysis, antioxidant nuclear factor, erythroid 2 like 2 (NFE2L2), inflammation, and AA metabolism were determined through reverse-transcription quantitative PCR and western blotting. Data were analyzed using the MIXED procedure of SAS 9.4 (SAS Institute Inc.). Among proteins associated with insulin signaling, compared with CTR, HP led to lower abundance of phosphorylated AKT serine/threonine kinase (p-AKT) and solute carrier family 2 member 4 (SLC2A4; insulin-induced glucose transporter). Although incubation with HPMET restored abundance of SLC2A4 to levels in the CTR and upregulated abundance of fatty acid synthase (FASN) and phosphorylated 5'-prime-AMP-activated protein kinase (p-AMPK), it did not alter p-AKT, which remained similar to HP. Among proteins associated with AA signaling, compared with CTR, challenge with HP led to lower abundance of phosphorylated mechanistic target of rapamycin (p-MTOR), and HPMET did not restore abundance to CTR levels. Among inflammation-related targets studied, incubation with HPMET led to greater protein abundance of nuclear factor kappa B subunit p65 (NFKB-RELA). The response in NFKB observed with HPMET was associated with a marked upregulation of the antioxidant transcription regulator NFE2L2 and the antioxidant enzyme glutathione peroxidase 1 (GPX1). No effects of treatment were detected for mRNA abundance of proinflammatory cytokines or antioxidant enzymes, underscoring the importance of post-transcriptional regulation. Overall, data indicated that short-term challenge with H₂O₂ was particularly effective in reducing insulin and AA signaling. Although a greater supply of Met had little effect on those pathways, it seemed to restore the protein abundance of the insulin-induced glucose transporter. Overall, the concomitant upregulation of key inflammation and antioxidant signaling proteins when a greater level of Met was supplemented to oxidant-challenged SAT highlighted the potential role of this AA in regulating the inflammatory response and oxidant status. Further studies should be conducted to assess the role of postruminal supply of Met and other AA in the regulation of immune, antioxidant, and metabolic systems in peripartal cow adipose tissue.

Gallic acid anti-myotoxic activity and mechanism of action, a snake venom phospholipase A2 toxin inhibitor, isolated from the medicinal plant Anacardium humile

Snakebite envenoming is the cause of an ongoing health crisis in several regions of the world, particularly in tropical and neotropical countries. This scenario creates an urgent necessity for new practical solutions to address the limitations of current therapies. The current study investigated the isolation, phytochemical characterization, and myotoxicity inhibition mechanism of gallic acid (GA), a myotoxin inhibitor obtained from Anacardium humile. The identification and isolation of GA was achieved by employing analytical chromatographic separation, which exhibited a compound with retention time and nuclear magnetic resonance spectra compatible with GA's commercial standard and data from the literature. GA alone was able to inhibit the myotoxic activity induced by the crude venom of Bothrops jararacussu and its two main myotoxins, BthTX-I and BthTX-II. Circular dichroism (CD), fluorescence spectroscopy (FS), dynamic light scattering (DLS), and interaction studies by molecular docking suggested that GA forms a complex with BthTX-I and II. Surface plasmon resonance (SPR) kinetics assays showed that GA has a high affinity for BthTX-I with a K_D of 9.146 × 10^-7 M. Taken together, the two-state reaction mode of GA binding to BthTX-I, and CD, FS and DLS assays, suggest that GA is able to induce oligomerization and secondary structure changes for BthTX-I and -II. GA and other tannins have been shown to be effective inhibitors of snake venoms' toxic effects, and herein we demonstrated GA's ability to bind to and inhibit a snake venom PLA₂, thus proposing a new mechanism of PLA₂ inhibition, and presenting more evidence of GA's potential as an antivenom compound.

Hydroxychloroquine with or without Azithromycin in Mild-to-Moderate Covid-19

BACKGROUND

Hydroxychloroquine and azithromycin have been used to treat patients with coronavirus disease 2019 (Covid-19). However, evidence on the safety and efficacy of these therapies is limited.

METHODS

We conducted a multicenter, randomized, open-label, three-group, controlled trial involving hospitalized patients with suspected or confirmed Covid-19 who were receiving either no supplemental oxygen or a maximum of 4 liters per minute of supplemental oxygen. Patients were randomly assigned in a 1:1:1 ratio to receive standard care, standard care plus hydroxychloroquine at a dose of 400 mg twice daily, or standard care plus hydroxychloroquine at a dose of 400 mg twice daily plus azithromycin at a dose of 500 mg once daily for 7 days. The primary outcome was clinical status at 15 days as assessed with the use of a seven-level ordinal scale (with levels ranging from one to seven and higher scores indicating a worse condition) in the modified intention-to-treat population (patients with a confirmed diagnosis of Covid-19). Safety was also assessed.

RESULTS

A total of 667 patients underwent randomization; 504 patients had confirmed Covid-19 and were included in the modified intention-to-treat analysis. As compared with standard care, the proportional odds of having a higher score on the seven-point ordinal scale at 15 days was not affected by either hydroxychloroquine alone (odds ratio, 1.21; 95% confidence interval [CI], 0.69 to 2.11; P = 1.00) or hydroxychloroquine plus azithromycin (odds ratio, 0.99; 95% CI, 0.57 to 1.73; P = 1.00). Prolongation of the corrected QT interval and elevation of liver-enzyme levels were more frequent in patients receiving hydroxychloroquine, alone or with azithromycin, than in those who were not receiving either agent.

CONCLUSIONS

Among patients hospitalized with mild-to-moderate Covid-19, the use of hydroxychloroquine, alone or with azithromycin, did not improve clinical status at 15 days as compared with standard care. (Funded by the Coalition Covid-19 Brazil and EMS Pharma; ClinicalTrials.gov number, NCT04322123.).

Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows

The objective for this study was to determine the effect of glucose dose and days following peak milk yield on plasma glucose, serum insulin, and plasma nonesterified fatty acids (NEFA) kinetics during an intravenous glucose tolerance test (IVGTT) in lactating dairy cattle. Six lactating Holstein dairy cows (3 primiparous and 3 multiparous) were assigned to 2 squares and received 0.092, 0.15, or 0.3 g of glucose/kg of body weight (BW) during an IVGTT at 74 and 221 d in milk (DIM), representing early (post-peak) lactation and mid lactation, respectively. Treatments were applied in a replicated Latin square design using contiguous 7-d periods within each stage of lactation. Milk production and dry matter intake were determined daily during the first 6 d of each period. The IVGTT was performed on d 7. For the IVGTT, cows were prepared with indwelling catheters in each jugular vein, and blood samples were collected at -15, -10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to the glucose infusion. Samples were analyzed for plasma glucose, serum insulin, and plasma NEFA concentrations. Increasing the glucose dose during the IVGTT increased plasma glucose area under the curve (AUC), decreased glucose half-life, and increased maximal plasma glucose concentrations in plasma during the IVGTT. Greater glucose dose during the IVGTT elevated serum insulin AUC and increased nadir NEFA concentrations. Maximal plasma glucose concentration during the IVGTT was lower, whereas maximum NEFA concentration, NEFA AUC, and NEFA clearance rate were greater at 74 than at 221 DIM. Only glucose half-life was responsive to stage of lactation × glucose dose effects during the IVGTT, and the decrease in glucose half-life with increasing glucose dose was greater at 74 than at 221 DIM. Glucose AUC was greater and NEFA AUC lower for cows at 74 than at 221 DIM. For the doses tested, a glucose dose greater than 0.092 g/kg of BW resulted in peak blood glucose concentration that exceeded the previously reported renal glucose excretion threshold of 8.3 mM. There is a need for accompanying data to determine if this is the case for the glucose doses evaluated in this experiment. Based on maximal peak glucose concentrations and effects on glucose half-life, we identify 0.092 g of glucose/kg of BW (0.46 g/kg of metabolic body weight) as the preferred dose for the IVGTT for cows at 74 and 221 DIM in this study.

Neutralization of a bothropic PLA2-like protein by caftaric acid, a novel potent inhibitor of ophidian myotoxicity

Envenoming by snakebite is an important global health issue that has received little attention, leading the World Health Organization to naming it as neglected tropical disease. Several snakebites present serious local symptoms manifested on victims that may not be efficiently neutralized by serum therapy. Phospholipase A₂-like (PLA₂-like) toxins are present in Viperidae venoms and are responsible for local myotoxic activity. Herein, we investigated the association between BthTX-I toxin and caftaric acid (CFT), a molecule present in plants. CFT neutralized neuromuscular blocking and muscle-damaging activities promoted by BthTX-I. Calorimetric and light-scattering assays demonstrated that CFT inhibitor interacted with dimeric BthTX-I. Bioinformatics simulations indicated that CFT inhibitor binds to the toxin's hydrophobic channel (HCh). According to the current myotoxic mechanism, three different regions of PLA₂-like toxins have specific tasks: protein allosteric activation (HCh), membrane dockage (MDoS), and membrane rupture (MDiS). We propose CFT inhibitor interferes with the allosteric activation, which is related to the conformation change leading to the exposure/alignment of MDoS/MDiS region. This is the first report of a PLA₂-like toxin fully inhibited by a compound that interacts only with its HCh region. Thus, CFT is a novel candidate to complement serum therapy and improve the treatment of snakebite.

Method for the estimation of genetic merit of animals with uncertain paternity under Bayesian inference

The use of controlled mating or artificial insemination is impracticable in the case of large herds, mainly because of labour costs and the need to delimit areas during the breeding period. However, the exclusion of information from animals with uncertain paternity reduces genetic progress. The objectives of this study were as follows: (i) propose an iterative empirical Bayesian procedure to implement the hierarchical animal model (ITER); (ii) calculate the posterior probabilities of paternity by the maximum likelihood method following the concepts; (iii) compare an average numerator relationship matrix (ANRM), Bayesian hierarchical (HIER) models and ITER. Records of Nellore animals born between 1984 and 2006 from the zootechnical archive of Agropecuária Jacarezinho Ltda were used. For data consistency, records of contemporary groups (CGs) with fewer than three animals and animals whose records were 3.5 standard deviations above or below the mean of their CG were eliminated. After editing the data, 62,212 animals in the file and 12,876 animals in pedigree file were maintained, respectively. Spearman and Pearson correlations between the posterior mean of the genetic effects of animals were calculated to compare the ranking of animals for selection. Simulated data were used to confirm the veracity of the model. The correlations between ITER and HIER and between ITER and ANRM were similar evaluating different files, which decreased at the same proportion when only high-ranked animals were evaluated. In conclusion, the model proposed herein is a suitable computational alternative to improve the prediction of breeding values of animals in genetic evaluations using large databases, including animals with uncertain paternity.

Genotype by environment interaction effects in genetic evaluation of preweaning gain for Line 1 Hereford cattle from Miles City, Montana

It has long been recognized that genotype × environment interaction potentially influences genetic evaluation of beef cattle. However, this recognition has largely been ignored in systems for national cattle evaluation. The objective of this investigation was to determine if direct and maternal genetic effects on preweaning gain would be reranked depending on an environmental gradient as determined by year effects. Data used were from the 76-yr selection experiment with the Line 1 Hereford cattle raised at Miles City, MT. The data comprised recorded phenotypes from 7,566 animals and an additional 1,862 ancestral records included in the pedigree. The presence of genotype × environment interaction was examined using reaction norms wherein year effects on preweaning gain were hypothesized to linearly influence the EBV. Estimates of heritability for direct and maternal effects, given the average environment, were 10 ± 2 and 26 ± 3%, respectively. In an environment that is characterized by the 5th (95th) percentile of the distribution of year effects, the corresponding estimates of heritability were 18 ± 3 (22 ± 3%) and 30 ± 3% (30 ± 3%), respectively. Rank correlations of direct and maternal EBV appropriate to the 5th and 95th percentiles of the year effects were 0.67 and 0.92, respectively. In the average environment, the genetic trends were 255 ± 1 g/yr for direct effects and 557 ± 3 g/yr for maternal effects. In the fifth percentile environment, the corresponding estimates of genetic trend were 271 ± 1 and 540 ± 3 g/yr, respectively, and in the 95th percentile environment, they were 236 ± 1 and 578 ± 3 g/yr, respectively. Linear genetic trends in environmental sensitivity were observed for both the direct (-8.06 × 10 ± 0.49 × 10) and maternal (8.72 × 10 ± 0.43 × 10) effects. Therefore, changing systems of national cattle evaluation to more fully account for potential genotype × environment interaction would improve the assessment of breeding stock, particularly for direct effects. Estimates of environmental sensitivity parameters could also facilitate identification of genetic limitations to production.

Genomewide association study for production and meat quality traits in Canchim beef cattle

The commercial value of the bovine carcass is determined by a set of traits, such as weight, yield, back fat thickness, and marbling; therefore, the genetic improvement of growth, meat, and carcass quality traits is an important tool to add value to the supply chain. Genomewide association studies (GWAS) enable the identification of loci that control phenotypic expression of quantitative traits (QTL). Therefore, the objective of this work was to perform a GWAS to identify genomic regions and genes associated with growth, carcass traits, and meat quality in Canchim beef cattle. These traits were yearling weight (YW), rib eye area (REA), back fat thickness (BFT), and marbling (MARB). To increase sample size and marker density, genotype imputation was performed, and only markers imputed with greater than 95% accuracy were used. Genomewide association study was performed using a Bayesian approach, by the Bayes B statistical method, incorporating genotypes and phenotypes from 614 animals from both the Canchim breed and the MA genetic group (offspring of Charolais bulls and one-half Canchim + one-half Zebu cows). This investigation identified 1 and 4 genomic regions explaining 0.23 and 7.35% of the genetic variance for REA and YW, respectively. These regions harbor a total of 19 genes, 7 of which were classified for biological functions by functional analysis. Significant associations were not observed for BFT and MARB. The identification of QTL that had been previously described in the literature reinforces associations found in this study.

Expression of paraoxonase types 1, 2 and 3 in reproductive tissues and activity of paraoxonase type 1 in the serum and seminal plasma of bulls

The paraoxonases types 1, 2 and 3 (PON1, PON2 and PON3, respectively) are enzymes that degrade lipid peroxides, preventing oxidative damages relevant for male reproductive function. This study determined the expression of those three paraoxonases in reproductive tissues of bulls and evaluated correlations among the activity of PON1 in the serum and seminal plasma with breeding soundness parameters in bulls. The expression of PON1, PON2 and PON3 was characterised by RT-PCR in samples of testicular parenchyma, vesicular glands and epididymis collected from three slaughtered bulls. All three paraoxonases were expressed in the testicular parenchyma, PON2 and PON3 were both expressed in the epididymis head and PON3 was also expressed in the epididymis tail. The PON1 activity was determined in samples of serum and seminal plasma from 110 bulls submitted to breeding soundness evaluation. There was a strong correlation (r = .90) between the activity of the PON1 in both serum and seminal plasma (p < .0001). The PON1 activity in the seminal plasma was positively correlated with ejaculate's colour, sperm mass activity (p = .04), motility, vigour and viability (all p < .01). Thus, PON1 may be a potential marker for sperm motility and viability in bulls.

Economic selection indexes for Hereford and Braford cattle raised in southern Brazil

Economic selection indexes (EI) are considered the best way to select the most profitable animals for specific production systems. Nevertheless, in Brazil, few genetic evaluation programs deliver such indexes to their breeders. The aims of this study were to determine the breeding goals (BG) and economic values (EV, in US$) for typical beef cattle production systems in southern Brazil, to propose EI aimed to maximize profitability, and to compare the proposed EI with the currently used empirical index. Bioeconomic models were developed to characterize 3 typical production systems, identifying traits of economic impact and their respective EV. The first was called the calf-crop system and included the birth rate (BR), direct weaning weight (WWd), and mature cow weight (MCW) as selection goals. The second system was called the full-cycle system, and its breeding goals were BR, WWd, MCW, and carcass weight (CW). Finally, the third was called the stocking and finishing system, which had WWd and CW as breeding goals. To generate the EI, we adopted the selection criteria currently measured and used in the empirical index of PampaPlus, which is the genetic evaluation program of the Brazilian Hereford and Braford Association. The comparison between the EI and the current PampaPlus index was made by the aggregated genetic-economic gain per generation (Δ). Therefore, for each production system an index was developed using the derived economic weights, and it was compared with the current empirical index. The relative importance (RI) for BR, WWd, and MCW for the calf-crop system was 68.03%, 19.35%, and 12.62%, respectively. For the full-cycle system, the RI for BR, WWd, MCW, and CW were 69.63%, 7.31%, 5.01%, and 18.06%, respectively. For the stocking and finishing production system, the RI for WWd and CW was 34.20% and 65.80%, respectively. The Δ for the calf-crop system were US$6.12 and US$4.36, using the proposed economic and empirical indexes, respectively. Respective values were US$19.87 and US$18.22 for the full-cycle system and US$20.52 and US$18.52 in the stocking and finishing system. The efficiency of the proposed EI had low sensitivity to changes in the values of the economic and genetic parameters. The 3 EI generated higher Δ when using the proposed economic weight compared to the Δ provided by a PampaPlus index, suggesting the use of proposed EI to obtain greater economic profitability in relation to the current empirical PampaPlus index.

Design of selection schemes to include tick resistance in the breeding goal for Hereford and Braford cattle

Ticks are one of the main causes of losses in cattle, causing economic impact by reducing productivity and fertility and by transmission of diseases. The objective of this study was to analyze the genetic gains obtained through different strategies to include traditional (EBV) or genomic EBV (GEBV) for tick count (TC) in selection indexes for Hereford and Braford cattle. Besides TC, we also considered traits currently included in the Delta G Breeding Program Index (DGI): preweaning gain, weaning conformation, weaning precocity, weaning muscling, postweaning gain, yearling conformation, yearling precocity, yearling muscling, and scrotal circumference. Genetic gain per generation (ΔG) was evaluated using the current DGI and including TC in 8 alternative scenarios with TC relative weightings of 10, 50, or 100% and using phenotype or GEBV. Genomic EBV accuracy () ranged between 0.1 and 0.9. As expected, increasing increases the accuracy of the index () for all scenarios in which GEBV were considered. As the relative weight of TC was increased to 50%, greater ΔG differences in relation to the baseline DGI ($53.03) scenario were observed when the GEBV information was included with equal to or greater than 0.7 only for TC (ΔG between $61.06 and $74.26) or equal to or greater than 0.5 for all traits (ΔG between $56.03 and $83.36). To achieve these accuracies for traits with low heritability, a large calibration data set would be required. Focusing only on TC, the availability of genomic information would be desirable to avoid the need to count ticks and the exposure of animals to parasitism risks. However, for = 0.7, the respective numbers for Hereford and Braford would be 4,703 and 6,522 animals. As expected, when comparing the relative index weights of 10, 50, and 100% for TC, the highest response to selection per generation (RS) for TC was in the scenario was with 100% relative weight and GEBV for this trait (SR = -0.09 SD with = 0.9). This would be the recommended scenario to form tick-resistant lines in Hereford and Braford cattle. However, with 50% relative weight for TC, including GEBV information for TC only or for all traits in index ( = 0.9), it should yield 93 or 84% of RS, respectively, compared to that obtained with full emphasis on TC (100% relative weight) and GEBV information. This indicates that in the presence of highly accurate GEBV, despite slightly slower gain for TC, indexes with 50% relative weight for TC are interesting alternatives to jointly improve tick resistance and other relevant traits.

Genomic prediction for tick resistance in Braford and Hereford cattle

One of the main animal health problems in tropical and subtropical cattle production is the bovine tick, which causes decreased performance, hide devaluation, increased production costs with acaricide treatments, and transmission of infectious diseases. This study investigated the utility of genomic prediction as a tool to select Braford (BO) and Hereford (HH) cattle resistant to ticks. The accuracy and bias of different methods for direct and blended genomic prediction was assessed using 10,673 tick counts obtained from 3,435 BO and 928 HH cattle belonging to the Delta G Connection breeding program. A subset of 2,803 BO and 652 HH samples were genotyped and 41,045 markers remained after quality control. Log transformed records were adjusted by a pedigree repeatability model to estimate variance components, genetic parameters, and breeding values (EBV) and subsequently used to obtain deregressed EBV. Estimated heritability and repeatability for tick counts were 0.19 ± 0.03 and 0.29 ± 0.01, respectively. Data were split into 5 subsets using k-means and random clustering for cross-validation of genomic predictions. Depending on the method, direct genomic value (DGV) prediction accuracies ranged from 0.35 with Bayes least absolute shrinkage and selection operator (LASSO) to 0.39 with BayesB for k-means clustering and between 0.42 with BayesLASSO and 0.45 with BayesC for random clustering. All genomic methods were superior to pedigree BLUP (PBLUP) accuracies of 0.26 for k-means and 0.29 for random groups, with highest accuracy gains obtained with BayesB (39%) for k-means and BayesC (55%) for random groups. Blending of historical phenotypic and pedigree information by different methods further increased DGV accuracies by values between 0.03 and 0.05 for direct prediction methods. However, highest accuracy was observed with single-step genomic BLUP with values of 0.48 for -means and 0.56, which represent, respectively, 84 and 93% improvement over PBLUP. Observed random clustering cross-validation breed-specific accuracies ranged between 0.29 and 0.36 for HH and between 0.55 and 0.61 for BO, depending on the blending method. These moderately high values for BO demonstrate that genomic predictions could be used as a practical tool to improve genetic resistance to ticks and in the development of resistant lines of this breed. For HH, accuracies are still in the low to moderate side and this breed training population needs to be increased before genomic selection could be reliably applied to improve tick resistance.

Response of lactating cows to live yeast supplementation during summer

Dairy cows experiencing heat stress have reduced intake and increased reliance on glucose, making feeding strategies capable of improving diet digestibility plausible for improving postrumen nutrient flow and performance. The effect of yeast on digestion and performance of lactating cows during the warm summer months of southeastern Brazil was evaluated. Cows were individually fed in tie stalls and temperature-humidity index was above 68 during 75.6% of the experiment. Twenty-eight Holstein cows (207±87 d in milk) received a standard diet for 14 d and then a treatment for 70 d, in a covariate-adjusted, randomized block design with repeated measures over time. Treatments were yeast (Saccharomyces cerevisiae) or control. Yeast was top dressed to the diet in the morning, equivalent to 25×10(10) cfu of live cells and 5×10(10) cfu of dead cells. The diet contained corn silage (37.7%), Tifton silage (7.1%), raw soybeans (4.1%), soybean meal (16.5%), finely ground corn (20.7%), and citrus pulp (11.9%). Yeast increased milk (26.7 vs. 25.4 kg/d) and solids yield (3.06 vs. 2.92 kg/d), especially lactose. Response in milk yield was consistent over time and started at d 5. The daily intake of digestible OM, total-tract digestibility of nutrients, urinary allantoin excretion, chewing pattern throughout the day, and dry matter intake did not respond to yeast. A trend was observed for increased plasma glucose with yeast (62.9 vs. 57.3mg/dL), lowered respiratory frequency (48 vs. 56 breaths/min), and increased plasma niacin content (1.31 vs. 1.22 µg/mL), though cows had similar rectal temperature. Ruminal lactate and butyrate as proportions of ruminal organic acids were reduced by yeast, but no effects on other organic acids, ruminal pH, or protozoa content were detected. Plasma urea N over 24h was increased by yeast. On d 72 to 74, citrus pulp was abruptly replaced with finely ground corn to induce acidosis. The increased load of starch increased dry matter intake between 0700 and 1300 h, jugular blood partial pressure of CO2, HCO3-, and base excess, and decreased blood pH for both treatments. The yeast treatment had a higher blood pH compared with the control, 7.34, and 7.31, respectively. Yeast supplementation improved lactation performance of dairy cows under heat stress. Improvement in lactation performance apparently involved the regulation of body homeothermia, rather than improved digestibility.

Genotype by environment interaction for post-weaning weight gain, scrotal circumference, and muscling score of composite beef cattle in different regions of Brazil

The objectives of this study were to characterize and define homogenous production environments of composite beef cattle in Brazil in terms of climatic and geographic variables by using multivariate exploratory techniques; to evaluate the presence of genotype by environment interaction (GxE) for post-weaning weight gain (PWG), yearling scrotal circumference (SC), and yearling muscling (MUS). Hierarchical and nonhierarchical cluster analysis was used to group farms located in regions with similar environmental variables into clusters. Six clusters of farms were formed. The effect of sire-cluster interaction was tested by single-trait analysis. Genetic parameters were estimated by multi-trait analysis considering the same trait to be different in each cluster. The effect of sire-cluster interaction was significant (P <0.01) for PWG and MUS. Estimates of genetic correlations among clusters ranged from 0.31 to 0.93 for PWG, 0.64 to 0.89 for SC, and 0.18 to 0.80 for MUS. These results indicate the need for a genetic analysis on a regional basis or inclusion of the GxE effect in the statistical model to permit appropriate evaluation of the animals.

Bioeconomic model and selection indices in Aberdeen Angus cattle

A bioeconomic model was developed to calculate economic values for biological traits in full-cycle production systems and propose selection indices based on selection criteria used in the Brazilian Aberdeen Angus genetic breeding programme (PROMEBO). To assess the impact of changes in the performance of the traits on the profit of the production system, the initial values ​​of the traits were increased by 1%. The economic values for number of calves weaned (NCW) and slaughter weight (SW) were, respectively, R$ 6.65 and R$ 1.43/cow/year. The selection index at weaning showed a 44.77% emphasis on body weight, 14.24% for conformation, 30.36% for early maturing and 10.63% for muscle development. The eighteen-month index showed emphasis of 77.61% for body weight, 4.99% for conformation, 11.09% for early maturing, 6.10% for muscle development and 0.22% for scrotal circumference. NCW showed highest economic impact, and SW had important positive effect on the economics of the production system. The selection index proposed can be used by breeders and should contribute to greater profitability.

Genotype by environment interaction and model comparison for growth traits of Santa Ines sheep

The objectives of the present study were to compare alternative models for the genetic evaluation and assess the importance of genotype by environment interaction (G×E) in the estimation of genetic parameters and genetic evaluation of birth weight (BW), weight at 60 days of age (W60) and weight at 180 days of age (W180) of Santa Ines sheep. Data comprise 7622 BW, 4673 W60 and 2830 W180 records from animals born in 44 Brazilian herds. Four models were used for the analyses: animal model (AM) with homogeneous residual variance (1), or heterogeneous residual variance (2), hierarchical reaction norms model (HRNM) with homogeneous (1) or heterogeneous residual variance (2). The models that best fit the BW, W60 and W180 data were AM2, HRNM1 and HRNM2 respectively. Thus, models for genetic evaluation that consider heterogeneity of variances are recommended to evaluate growth traits of sheep. The correlation between intercept and slope of the HRNM was higher than 0.70 for all traits studied, indicating that animals with higher average breeding values responded better to improvement in environmental conditions, a fact characterizing the scale effect of G×E. Therefore, G×E is an important factor to be considered in the estimation of genetic parameters and genetic evaluation of growth traits of sheep.

Comparison of a genetic group and unknown paternity models for growth traits in Nellore cattle

The aim of the present study was to compare a model assuming unknown paternity and a model using genetic grouping to indicate the most adequate statistical procedure for the estimation of breeding values for animals with uncertain paternity. After data consistency, 62,212 Nellore animals, offspring of 581 bulls and 27,743 cows, were used in the analyses. The pedigree file contained 75,088 animals, including 22,810 (30.18%) offspring of multiple sires and 12,876 animals belonging to the base population with unknown parents. Three different approaches were adopted to deal with uncertain paternity of multiple-sire (MS) offspring. In the model of unknown paternity, the MS groups were ignored, and the sires of MS offspring were considered to be unknown and to belong to a single base population. In the genetic group approach, 2 definitions were used. In the first definition (GGa), "phantom parents" for animals with uncertain paternity were attributed, defining the genetic group as the MS group. In the other approach, GGb, phantom parents for animals with uncertain paternity were also attributed; however, MS offspring were clustered in genetic groups according to their year of birth, every 3 yr, on the basis of the average of male generation interval. Univariate analyses were performed under the Bayesian approach via Markov chain Monte Carlo methods. Models were compared by deviance information criteria and the conditional predictive ordinate. According to the choice criteria results, the genetic group model defined by the generation interval of males was more appropriate for predicting the genetic merit of animals with uncertain paternity. Therefore, the use of this model is recommended for the prediction of genetic merit and classification of offspring of multiple sires.

PP156. High prevalence of pre-pregnancy overweight and obesity associated with maternal and perinatal complications

INTRODUCTION

High prevalence of pre-pregnancy weight excess, as well as evidence of increased risk of maternal and perinatal complications associated with nutritional states have been observed lately. Considering the possible ethnic and environmental influences few studies have assessed this risk in pregnant Brazilian women.

OBJECTIVES

This study aimed at determining the prevalence of pre-pregnancy weight excess (overweight and obesity) and its association with maternal and perinatal complications in a Brazilian women population.

METHODS

We conducted a prospective cross-sectional study with 3,300 women who had birth care at the Asa Sul Regional Hospital of Brasília - Federal District (FD), from October 2009 to May 2010. Nutritional status was determined by body mass index (BMI), according to WHO criteria (2000): Low weight (BMI<18.5kg/m(2)), Normal weight (BMI between 18.5 and 24.9kg/m(2)), Weight excess (BMI⩾25kg/m(2)), Overweight (BMI between 25 and 29.9kg/m(2)) and obesity (BMI⩾30kg/m(2)). The outcome variables were: pre-clinical complications such as chronic hypertension and diabetes, manifestation of gestational hypertension/preeclampsia, pregnancy duration and resolution as well as perinatal outcomes. The association among these variables was assessed using chi-square (Pearson) and Fisher's exact test. Results were considered significant when p<0.05.

RESULTS

In this population, weight excess before pregnancy had a prevalence of 27.2%, being 19.7% and 7.5% of pregnant women presenting, respectively, overweight and obesity. The prevalence of normal weight was 64.6% and low weight was 8.3%. Comparing the weight excess (BMI⩾25kg/m(2)) group with the normal weight group it was observed predominant hypertension (23% vs. 10%) and diabetes (10.1% vs. 3.6%), prolonged pregnancy (14.4% vs. 10.7%) and cesarean section rate (58.1% vs. 47.2%) in the weight excess group. Newborn weight equal to or greater than 4,000 g (9.5% vs. 4.5%) as well as fetal macrosomia (14.6% vs. 7.4%) also predominated in weight excess group. The comparison among the groups normal weight, overweight and obesity showed predominance of hypertension, diabetes cesarean section rate, newborns weight and fetal macrosomia in the obesity group.

CONCLUSION

In the population analyzed, the prevalence of pre-pregnancy weight excess, particularly obesity, was high and associated with maternal and perinatal complications. Weight excess pre-pregnancy should be considered a risk to the pregnancy, demanding different obstetric care. Efforts should be made so that, in the pre-pregnancy period, women's weight can be as close to the normal weight as possible.

Linear reaction norm models for genetic merit prediction of Angus cattle under genotype by environment interaction

The objectives of this work were to assess alternative linear reaction norm (RN) models for genetic evaluation of Angus cattle in Brazil. That is, we investigated the interaction between genotypes and continuous descriptors of the environmental variation to examine evidence of genotype by environment interaction (G×E) in post-weaning BW gain (PWG) and to compare the environmental sensitivity of national and imported Angus sires. Data were collected by the Brazilian Angus Improvement Program from 1974 to 2005 and consisted of 63,098 records and a pedigree file with 95,896 animals. Six models were implemented using Bayesian inference and compared using the Deviance Information Criterion (DIC). The simplest model was M(1), a traditional animal model, which showed the largest DIC and hence the poorest fit when compared with the 4 alternative RN specifications accounting for G×E. In M(2), a 2-step procedure was implemented using the contemporary group posterior means of M(1) as the environmental gradient, ranging from -92.6 to +265.5 kg. Moreover, the benefits of jointly estimating all parameters in a 1-step approach were demonstrated by M(3). Additionally, we extended M(3) to allow for residual heteroskedasticity using an exponential function (M(4)) and the best fitting (smallest DIC) environmental classification model (M(5)) specification. Finally, M(6) added just heteroskedastic residual variance to M(1). Heritabilities were less at harsh environments and increased with the improvement of production conditions for all RN models. Rank correlations among genetic merit predictions obtained by M(1) and by the best fitting RN models M(3) (homoskedastic) and M(5) (heteroskedastic) at different environmental levels ranged from 0.79 and 0.81, suggesting biological importance of G×E in Brazilian Angus PWG. These results suggest that selection progress could be optimized by adopting environment-specific genetic merit predictions. The PWG environmental sensitivity of imported North American origin bulls (0.046 ± 0.009) was significantly larger (P < 0.05) than that of local sires (0.012 ± 0.013). Moreover, PWG of progeny of imported sires exceeded that of native sires in medium and superior production levels. On the other hand, Angus cattle locally selected in Brazil tended to be more robust to environmental changes and hence be more suitable when production environments for potential progeny is uncertain.

Structural and functional studies of a bothropic myotoxin complexed to rosmarinic acid: new insights into Lys49-PLA₂ inhibition

Snakebite envenoming is an important public health problem in many tropical and subtropical countries, and is considered a neglected tropical disease by the World Health Organization. Most severe cases are inflicted by species of the families Elapidae and Viperidae, and lead to a number of systemic and local effects in the victim. One of the main problems regarding viperidic accidents is prominent local tissue damage whose pathogenesis is complex and involves the combined actions of a variety of venom components. Phospholipases A₂ (PLA₂s) are the most abundant muscle-damaging components of these venoms. Herein, we report functional and structural studies of PrTX-I, a Lys49-PLA₂ from Bothops pirajai snake venom, and the influence of rosmarinic acid (RA) upon this toxin's activities. RA is a known active component of some plant extracts and has been reported as presenting anti-myotoxic properties related to bothopic envenomation. The myotoxic activity of Lys49-PLA₂s is well established in the literature and although no in vivo neurotoxicity has been observed among these toxins, in vitro neuromuscular blockade has been reported for some of these proteins. Our in vitro studies show that RA drastically reduces both the muscle damage and the neuromuscular blockade exerted by PrTX-I on mice neuromuscular preparations (by ∼80% and ∼90%, respectively). These results support the hypothesis that the two effects are closely related and lead us to suggest that they are consequences of the muscle membrane-destabilizing activity of the Lys49-PLA₂. Although the C-terminal region of these proteins has been reported to comprise the myotoxic site, we demonstrate by X-ray crystallographic studies that RA interacts with PrTX-I in a different region. Consequently, a new mode of Lys49-PLA₂ inhibition is proposed. Comparison of our results with others in the literature suggests possible new ways to inhibit bothropic snake venom myotoxins and improve serum therapy.

Genotype × environment interaction for long-yearling weight in Canchim cattle quantified by reaction norm analysis

The objective of this study was to investigate the presence of genotype × environment interactions (G×E) for long-yearling weight in Canchim cattle (5/8 Charolais + 3/8 zebu) in Brazil using reaction norms (RN). The hierarchical RN model included the fixed effect of age of the animal (linear coefficient) and random effects of contemporary groups and additive animal genetic intercept and slope of the RN and contemporary group effects as random effects. Contemporary groups as the most elemental representation of management conditions in beef cattle were chosen to represent the environmental covariate of the RN. The deviance information criteria demonstrated that a homoskedastic residual RN model provided a better data fit compared with a heteroskedastic counterpart and with a traditional animal model, which had the worst fit. The environmental gradient for long-yearling weight based on contemporary group effects ranged from -105 to 150 kg. The additive direct variance and heritability estimates increased with increasing environmental gradient from 74.33 ± 22.32 to 1,922.59 ± 258.99 kg(2) and from 0.08 ± 0.02 to 0.68 ± 0.03, respectively. The high genetic correlation (0.90 ± 0.03) between the intercept and the slope of the RN shows that animals with the greatest breeding values best responded to environmental improvement, characterizing scale effect as the source of G×E for long-yearling weight. The phenotypic plasticity demonstrated by the slope of the RN of the animal indicates the possibility to change genotype expression along the environmental gradient through selection. The results demonstrate the importance of accounting for G×E in the genetic evaluation of this population.

Accounting for outliers and heteroskedasticity in multibreed genetic evaluations of postweaning gain of Nelore-Hereford cattle

The objectives of this study were to demonstrate the utility of hierarchical Bayesian models combining residual heteroskedasticity with robustness for outlier detection and muting and to evaluate the effects of such joint modeling in multibreed genetic evaluations. A 3 x 2 factorial specification of 6 residual variance models based on several distributional (Gaussian, Student's t, or Slash) and variability (homoskedastic or heteroskedastic) assumptions was used to analyze 22,717 postweaning gain records from a Nelore-Hereford population (40,082 animals in the pedigree). To illustrate the utility of the 2 robust distributional specifications (Student's t and Slash) for outlier detection and muting, 3 records from the same contemporary group (an extreme residual outlier, a mild residual outlier, and a near-zero residual) were chosen for further study. The posterior densities of the corresponding weighting variables of these records were used to assess their degree of Gaussian outlyingness and the ability of the robust models to mute the effects of deviant records. The Student's t heteroskedastic provided the best-fit model among the 6 specifications and was preferred for genetic merit inference. Kendall rank correlations of the posterior means of the additive genetic effects of the animals, used to compare the selection order of the Student's t and Gaussian models, were reasonably high across all animals within the most frequent genotypes, ranging from 0.83 to 0.91 and from 0.89 to 0.95 for the homoskedastic and the heteroskedastic versions, respectively. However, when considering only animals ranked in the top 10% by the customary Gaussian homoskedastic model, these rank correlations were reduced considerably, ranging from 0.29 to 0.57 and from 0.72 to 0.85 between the 2 residual densities within the homoskedastic and heteroskedastic versions, respectively. Rank correlations between the homoskedastic and heteroskedastic versions within each of the Gaussian and Student's t error models tended to be smaller, with a range from 0.68 to 0.90 across all animals and from 0.28 to 0.67 for animals ranked in the top 10%. These results support the implementation of robust models accounting for sources of heteroskedasticity to increase the precision and stability of multibreed genetic evaluations with proper statistical treatment of deviant records.

Multiple-breed genetic inference using heavy-tailed structural models for heterogeneous residual variances1

Multiple-breed genetic models recently have been demonstrated to account for the heterogenous genetic variances that exist between different beef cattle breed groups. We extend these models to allow for residual heteroskedasticity (heterogeneous residual variances), specified as a function of fixed effects (e.g., sex, breed proportion, breed group heterozygosity) and random effects such as contemporary groups (CG). We additionally specify the residual distributions to be either Gaussian or based on heavier-tailed alternatives such as the Student's t or Slash densities. For each of these three residual densities using either homoskedastic (homogeneous variance) or heteroskedastic error specifications, we analyzed 22,717 postweaning gain records from a Nelore-Hereford population based on a Markov chain Monte Carlo animal model implementation. The heteroskedastic Student's t error model (with estimated df = 7.33 +/- 0.48) was clearly the best-fitting model based on a pseudo-Bayes factor criterion. Breed group heterozygosity and, to a lesser extent, calf sex seemed to be marginally important sources of residual heteroskedasticity. Specifically, the residual variance in F1 animals was estimated to be 0.70 +/- 0.16 times that for purebreds, whereas the male residual variance was estimated to be 1.13 +/- 0.09 times that for females. The CG effects were important random sources of residual heteroskedasticity (i.e., the coefficient of variation of CG-specific residual variances was estimated to be 0.72 +/- 0.06). Purebred Nelores were estimated to have a larger genetic variance (124.84 +/- 21.75 kg2) compared with Herefords (40.89 +/- 6.70 kg2) under the heteroskedastic Student's t error model; however, the converse was observed from results based on a homoskedastic Student's t error model (46.24 +/- 10.90 kg2 and 60.11 +/- 8.54 kg2, respectively). These results indicate that allowing for robustness to outliers and accounting for heteroskedasticity of residual variances has potentially important implications for variance component and genetic parameter estimates from data on multiple-breed populations.

Hierarchical Bayes multiple-breed inference with an application to genetic evaluation of a Nelore-Hereford population

The primary objective of this study was to demonstrate the utility of a hierarchical Bayes implementation of a multiple-breed animal model (MBAM) to estimate breed composition means and additive genetic variances as well as on variances due to the segregation between breeds. The MBAM and a conventional animal model (AM) were both applied to five simulated data sets derived from each of two different populations. Population I consisted of crosses between two breeds having a twofold difference in genetic variance and a nonzero segregation variance. Population II had the same population structure as Population I, except that the two breeds had the same genetic variance with no segregation variance; that is, Population II was essentially single breed in its genetic architecture. For Population I, posterior means of all variance components obtained by MBAM were unbiased, with 95% posterior probability intervals (PPI) having the expected coverage based on five replicates. The MBAM showed a slightly superior performance over the AM for genetic predictions in Population I, although there was no evidence that the use of the MBAM translated into greater genetic gains relative to the use of the AM. Nevertheless, the MBAM was clearly demonstrated to have superior fit to the data using pseudo-Bayes factors (PBF) as the basis for model choice. As expected, the MBAM and AM performed equally well in Population II. A data set consisting of 22,717 postweaning gain (PWG) records of a Nelore-Hereford population (40,082 animals in the pedigree) also was analyzed. The MBAM inference on Nelore and Hereford additive heritabilities (h2A) substantially differed. Herefords had a posterior mean h2A of 0.20 with a 95% PPI of 0.15 to 0.25, whereas the corresponding values for the Nelores were 0.07 and 0.04 to 0.11, respectively. The posterior mean genetic variance due to the segregation between these breeds was 8.4 kg2, with a 95% PPI of 2.3 to 24.8 kg2, and represented 35.4% of the Nelore but only 9.9% of the Hereford posterior mean genetic variance. The posterior mean h2A using the AM was 0.15, presumed common across the two breeds, with a 95% PPI of 0.11 to 0.19. The PBF heavily favored the MBAM over the AM for the PWG data. Accordingly, the MBAM represents a viable alternative to AM for multiple-breed genetic evaluations, providing the necessary flexibility in modeling heteroskedastic genetic variances of breed composition groups.

Hyperimmunization of Steers with J5 Escherichia coli Bacterin: Effects on Isotype-Specific Serum Antibody Responses and Cross Reactivity with Heterogeneous Gram-Negative Bacteria

Isotype-specific antibody responses and cross reactivity were profiled following hyperimmunization of steers with J5 Escherichia coli bacterin. The vaccine was administered at time 0, 30 d later, and every 2 wk for 10 subsequent immunizations. Blood was collected preimmunization and multiple times following each immunization. Isotype-specific anti-J5 Escherichia coli antibody response profiles in diluted sera harvested from each sample were assayed by ELISA and recorded as optical density. Selected sera were assayed for anti-J5 Escherichia coli antibody titers and used to determine cross reactivity against a variety of gram-negative bacteria. Immunization number and day postimmunization influenced response profiles for anti-J5 E. coli IgM, IgG(1)and IgG(2) antibodies. Two immunizations increased mean serum IgM and the IgG(1)antibody profiles above preimmunization levels, but 5 immunizations were required to detect significant IgG(2) antibody responses that were above preimmunization levels. Isotype-specific cross reactivity of the serum antibodies with a variety of heterologous gram-negative bacteria was also increased by hyperimmunization. However, no cross reactivity was observed for Staphylococcus aureus, purified lipopolysaccharide, or lipid A. Our results indicate that multiple booster doses of J5 E. coli bacterin may be required to elicit high levels of cross-reactive serum IgG(2) antibodies.

Basic concepts in statistics for veterinary ophthalmologists

Abstract This review article provides a comprehensive coverage of basic statistical procedures commonly used in biologic experiments and is intended to be a basic guide to the selection of appropriate tests and also to aid the reader in the evaluation of published studies. The focus is on the use, interpretation and presentation of the main statistical tests and their key concepts for the practicing veterinary ophthalmologist. Several examples derived from actual ophthalmic research are presented in the text. Lastly, the article discusses computer-based statistical analysis, provides a list of different software available and gives a practical example of a 'real life' statistical analysis.