Estimation of economic values and financial losses associated with clinical mastitis and somatic cell score in Holstein dairy cattle

High-throughput analysis of CircRNA in cows with naturally infected Staphylococcus aureus mammary gland

Circular RNAs (CircRNA) are a special type of non-coding RNA molecule with a closed ring structure and are not affected by RNA exonucases. It has stable expression, is not easy to degrade, and exists in most eukaryotes. However, circRNA regulation of cow mastitis has not been widely recognized. Mammary epithelial tissues were collected from healthy Holstein cows (HCN) and mastitis Holstein cows (HCU). RNA sequencing (RNA SEQ) was performed for the differentially expressed circRNAs, and analysis results showed that 19 differentially expressed circRNAs were identified in HCN and HCU, among which 6 circRNAs were up-regulated and 13 circRNAs were down-regulated. We randomly selected nine circRNAs for Q-PCR verification, and the results showed consistent expression. Three circRNAs: circRNA2860, circRNA5323 and circRNA4027 were confirmed to be significantly differentially expressed circRNAs in cow mastitis. Also, their host genes TRPS1, SLC12A2 and MYH11 might be directly or indirectly play a role in cow mastitis. Furthermore, RNA polymerase transcription factor binding and tight junction are most enriched in GO and KEGG pathways, respectively. In addition, the regulatory network of circRNA-miRNA has been inferred from a bioinformatics perspective, which may help to understand the underlying molecular mechanism of circRNAs involved in regulating mastitis in cows.

Economic values for production, fertility and mastitis traits for temperate dairy cattle breeds in tropical Sri Lanka

Economic values for annual milk yield (MY, kg), annual fat yield (FY, kg), annual protein yield (PY, kg), age at first calving (AFC, days), number of services per conception (NSC), calving interval (CI, days) and mastitis episodes (MS) were derived for temperate dairy cattle breeds in tropical Sri Lanka using a bio‐economic model. Economic values were calculated on a per cow per year basis. Derived economic values in rupees (LKR) for MY, FY and PY were 107, −162 and −15, while for AFC, NSC, CI and MS, economic values were −59, −270, −84 and −8,303. Economic values for FY and PY further decreased with higher feed prices, and a less negative economic value for FY was obtained with increased price for fat. Negative economic values for FY and PY show that genetic improvement for these traits is not economical due to the high feed costs and/or the insufficient payment for fat and protein. Therefore, revision of milk fat and protein payments is recommended. Furthermore, the breeding objective developed in this study was dominated by milk production and fertility traits. Adaptability and functional traits that are important in a temperate dairy cattle breeding programme in tropical Sri Lanka, such as longevity, feed efficiency, disease resistance and heat tolerance should be recorded to incorporate them in the breeding objective. Continued trait recording of all traits is recommended to ensure dairy cows can be selected more effectively in a tropical environment based on a breeding objective that also includes adaptability and functional traits.

Genomic studies of milk-related traits in water buffalo (Bubalus bubalis) based on single-step genomic best linear unbiased prediction and random regression models

Genomic selection has been widely implemented in many livestock breeding programs, but it remains incipient in buffalo. Therefore, this study aimed to (1) estimate variance components incorporating genomic information in Murrah buffalo; (2) evaluate the performance of genomic prediction for milk-related traits using single- and multitrait random regression models (RRM) and the single-step genomic best linear unbiased prediction approach; and (3) estimate longitudinal SNP effects and candidate genes potentially associated with time-dependent variation in milk, fat, and protein yields, as well as somatic cell score (SCS) in multiple parities. The data used to estimate the genetic parameters consisted of a total of 323,140 test-day records. The average daily heritability estimates were moderate (0.35 ± 0.02 for milk yield, 0.22 ± 0.03 for fat yield, 0.42 ± 0.03 for protein yield, and 0.16 ± 0.03 for SCS). The highest heritability estimates, considering all traits studied, were observed between 20 and 280 d in milk (DIM). The genetic correlation estimates at different DIM among the evaluated traits ranged from -0.10 (156 to 185 DIM for SCS) to 0.61 (36 to 65 DIM for fat yield). In general, direct selection for any of the traits evaluated is expected to result in indirect genetic gains for milk yield, fat yield, and protein yield but also increase SCS at certain lactation stages, which is undesirable. The predicted RRM coefficients were used to derive the genomic estimated breeding values (GEBV) for each time point (from 5 to 305 DIM). In general, the tuning parameters evaluated when constructing the hybrid genomic relationship matrices had a small effect on the GEBV accuracy and a greater effect on the bias estimates. The SNP solutions were back-solved from the GEBV predicted from the Legendre random regression coefficients, which were then used to estimate the longitudinal SNP effects (from 5 to 305 DIM). The daily SNP effect for 3 different lactation stages were performed considering 3 different lactation stages for each trait and parity: from 5 to 70, from 71 to 150, and from 151 to 305 DIM. Important genomic regions related to the analyzed traits and parities that explain more than 0.50% of the total additive genetic variance were selected for further analyses of candidate genes. In general, similar potential candidate genes were found between traits, but our results suggest evidence of differential sets of candidate genes underlying the phenotypic expression of the traits across parities. These results contribute to a better understanding of the genetic architecture of milk production traits in dairy buffalo and reinforce the relevance of incorporating genomic information to genetically evaluate longitudinal traits in dairy buffalo. Furthermore, the candidate genes identified can be used as target genes in future functional genomics studies.

Analyses of the genetic relationships between lactose, somatic cell score, and growth traits in Simmental cattle

Lactose and somatic cell score (SCS) are major economic traits of milk. However, for many countries, they are typically not directly considered in the national genetic evaluation of Simmental cattle. This study aimed to estimate the genetic relationships between lactose, SCS, and growth traits of Simmental cattle to provide information for the national genetic evaluation of the selection of traits of this cattle population. The data of 1781 animals with 6519 records obtained over a period of 41 years (1975-2016) were collected from Xinjiang Hutubi Farm, China. The analyzed traits included 305 days of milk yield (305MY), milk fat percentage (MFP), milk protein percentage (MPP), milk lactose percentage (MLP), total solids (TS), SCS, body height (BH), body length (BL), chest girth (CG), abdominal circumference (AC), rump width (RW), rump length (RL), leg circumference (LC), and cannon circumference (CC). The multiple-trait repeatability model was adopted to estimate (co)variance components using the average information-restricted maximum likelihood method implemented using the DMU statistical package. The heritability estimates for milk components and growth traits ranged from 0.09 (SCS) to 0.51 (BH). Genetic correlations for milk components ranged from 0.03 ± 0.14 (MFP and MLP) to 0.81 ± 0.08 (MFP and MPP). Genetic correlation between MLP and SCS was moderate and negative (-0.50 ± 0.15) compared with that among other traits. Genetic correlations between the milk components and growth traits ranged from 0.00 ± 0.07 (305MY and RW) to -0.64 ± 0.15 (MLP and BL). Genetic correlations of BL, LC, RW, and RL with MLP were moderate to high and negative ranging from -0.39 to -0.64. Somatic cell score showed the highest correlation with BL (0.41) followed by LC (0.21). An increase in MLP would result in an increase in 305MY or TS and a decrease in BL, LC, RW, and RL. Additionally, a decrease in SCS would occur with the selection of increased MLP and reduced BL. We conclude that selection based on easily and inexpensively measured growth traits could improve the milk quality from Simmental cattle.

Financial and economic analyses of the impact of cattle mastitis on the profitability of Egyptian dairy farms

Aim:

This study aimed to evaluate and quantify the different factors affecting the costs of mastitis in cattle, to quantify the annual and monthly financial losses attributed to mastitis, and to estimate production losses using average linear scores found on The Dairy Herd Improvement Association somatic cell count (SCC) sheets and bulk tank SCC per lactation number.

Materials and Methods:

All data (bovine mastitis-associated costs and expenditures in Egyptian dairy herds) were analyzed using SPSS/PCT, 2001. A partial budget technique using spreadsheet software and the general linear model procedure was used to analyze the productive and financial measures.

Results:

Mastitis was present in 57.1% of cows (240/420), while clinical mastitis (CM) was present in 19% of them (80/420). The geometric mean of SCC/ml in bulk tank milk samples of 150 cattle dairy farms was 556.3×10³. The annual subclinical mastitis (SCM)-related economic loss was 21,933,258.6 LE, and the two most important cost components were the subsequent decrease in milk production and quality premium losses (93% and 7% of SCM costs, respectively). The quality premium loss was 1,369,602.1 LE. On the other hand, the annual economic loss due to decreased milk production as a result of SCM was 20,563,656.5 LE. The total cost of 80 CM cases, including the failure and preventive costs, was 1,196,871.4 LE, including 1,169,150.4 LE failure costs (106,336.0 LE in direct costs and 1,062,814.4 LE in indirect costs) and 27,721.0 LE preventive costs. The average cost per CM case was 28,760.9 LE, including veterinary time and consultation fees of 250.0 LE (1%), labor 562.5 LE (2%), premature culling 736,000.0 LE (77%), decreased milk production 4085.18 LE (13.7%), discarded milk 185.3 LE (1%), and drugs and treatments 328.9 LE (1%). The total costs of CM (expenditures) extra control and preventive measures, including the diagnosis of CM for 80 cows annually in 20 Egyptian dairy farms were 27,721.0 LE, representing 346.5 LE or 1% of the total cost of CM cases. The cost of monitoring and diagnostic measures was 8635.2 LE, representing 107.9 LE or 1% of the total cost of a case of CM.

Conclusion:

The method used for cost estimation, in this study, is highly adaptable to individual cattle farms and had a major role in assessing specific control and management measures. The concepts described in this paper help to improve our understanding of the full economic impact of clinical and subclinical mastitis in cattle in Egypt. Assessing the economic losses from mastitis to determine the economic costs and losses occurring in Egyptian dairy farms is critical for encouraging farmers to acknowledge the scale of the problem and implement effective management practices aimed at improving mastitis control and reducing the associated costs.

Effect of Lipopolysaccharide and Muramyl Dipeptide on Apoptosis of Bovine Mammary Gland Lymphocytes

Simple Summary

Inflammation of the mammary gland in dairy cattle is a global problem and causes huge financial loss to dairy farmers. Inflammation is caused by many species of bacteria penetrating through the teat canals into the udder. Those bacteria are usually eliminated by treatment with intramammary injection of antibiotics, while they are also eliminated by the immune cells of the cow. One of the immune cells are lymphocytes which are responsible for specific immunity. When viable, they are able to carry out their normal functions. The present study focused on the investigation of cell death of lymphocytes during bovine mammary gland inflammation. We analyzed apoptosis in mammary gland lymphocytes under the stimulation of lipopolysaccharides and muramyl dipeptide as the endotoxin of Gram-negative bacteria and the natural content of the cell wall of Gram-positive bacteria. We found that they induce lymphocyte apoptosis in the early phase of inflammation, which can be associated with the expression of CD44 receptors on lymphocytes. This receptor is important in many physiological processes, including apoptosis of cells. For a better understanding of immune responses in mammary glands and for developing of immunotherapy without antibiotics, the process of inflammation, including cell death of immune cells necessitates further holistic studies.

Abstract

The aim of this study was to evaluate whether apoptosis of lymphocytes is modulated by stimulation by lipopolysaccharide (LPS) of Escherichia coli or muramyl dipeptide (MDP). Cell populations were obtained by lavaging of the mammary glands 24, 48, 72, and 168 h following intramammary induced inflammation. The portion of apoptotic lymphocytes peaked at 48 h after treatment with LPS or MDP. The analysis of CD44 expression of the same cell populations showed a higher percentage of CD44-positive lymphocytes 24- and 48-h following induction of inflammation by LPS or MDP. The results demonstrate that during both experimental infection of bovine mammary glands with LPS or MDP, apoptosis of lymphocytes was induced in the initial phase of the inflammatory response and CD44 was also overexpressed at the beginning of inflammation. These data suggest a connection of lymphocyte apoptosis with the expression of CD44 receptors.

In vivo model to study the impact of genetic variation on clinical outcome of mastitis in uniparous dairy cows

BACKGROUND

In dairy herds, mastitis causes detrimental economic losses. Genetic selection offers a sustainable tool to select animals with reduced susceptibility towards postpartum diseases. Studying underlying mechanisms is important to assess the physiological processes that cause differences between selected haplotypes. Therefore, the objective of this study was to establish an in vivo infection model to study the impact of selecting for alternative paternal haplotypes in a particular genomic region on cattle chromosome 18 for mastitis susceptibility under defined conditions in uniparous dairy cows.

RESULTS

At the start of pathogen challenge, no significant differences between the favorable (Q) and unfavorable (q) haplotypes were detected. Intramammary infection (IMI) with Staphylococcus aureus 1027 (S. aureus, n = 24, 96 h) or Escherichia coli 1303 (E. coli, n = 12, 24 h) was successfully induced in all uniparous cows. This finding was confirmed by clinical signs of mastitis and repeated recovery of the respective pathogen from milk samples of challenged quarters in each animal. After S. aureus challenge, Q-uniparous cows showed lower somatic cell counts 24 h and 36 h after challenge (P < 0.05), lower bacterial shedding in milk 12 h after challenge (P < 0.01) and a minor decrease in total milk yield 12 h and 24 h after challenge (P < 0.01) compared to q-uniparous cows.

CONCLUSION

An in vivo infection model to study the impact of genetic selection for mastitis susceptibility under defined conditions in uniparous dairy cows was successfully established and revealed significant differences between the two genetically selected haplotype groups. This result might explain their differences in susceptibility towards IMI. These clinical findings form the basis for further in-depth molecular analysis to clarify the underlying genetic mechanisms for mastitis resistance.

Genetic trends and genetic correlations between 305-day milk yield, persistency and somatic cell score of Holstein cows in Brazil using random regression model

The objective was to estimate genetic correlations for persistency, milk yield and somatic cell score (SCS) in Holstein cattle in Brazil. A dataset with 190389 records of test-day milk and of test-day SCS from 21824 cows was used. Two-trait random regression model with a fourth order Legendre polynomial was used. Persistency (PS) was defined as the difference between estimated breeding values (EBV) along different days in milk using two formulae: and PS2=(EBV290–EBV90). Larger values for PS2 or lower ones for PS1 indicate higher persistency. Heritability was 0.24 for 305-day milk yield, 0.14 for SCS up to 305 days, 0.15 for PS1 and 0.14 for PS2. Genetic correlation between 305-day milk yield and SCS up to 305 days was –0.47. Genetic correlation of 305-day milk yield with PS1 and PS2 was –0.32 and 0.30, respectively. Genetic correlation of SCS up to 305 days was 0.25 with PS1 and –0.20 with PS2. The additive genetic correlations between milk yield, SCS and persistency showed that selection for higher persistency or for low somatic cell score will increase 305-day milk yield.

Appropriate selection indices for functional traits in dairy cattle breeding schemes

The objective of this study was to establish different single or multiple trait selection indices to calculate genetic and economic gains by combining some production, reproduction and udder health traits in a population similar to the overall practical situation in Iran, with and without imposing restrictions on genetic change for some traits. The SelAction software was used to perform the analyses based on selection index theory through a deterministic model. Results indicated that among established indices, the index that showed the highest genetic gain for milk yield did not maximize the total genetic and economic gains. Rather, the index that included all production, reproduction and udder health traits yielded the highest genetic and economic gains. When we placed restriction on the selection indices, the economic gain decreased and the amount of reduction depended on the heritability and the correlation of restricted trait(s) with other traits. Generally, regarding the economic genetic gain per generation, the indices based on records of 200 offspring were 4.819% more efficient than those that used information of 100 offspring.

Base-catalyzed hydrolysis and speciation-dependent photolysis of two cephalosporin antibiotics, ceftiofur and cefapirin

Lately, special attention has been given to veterinary cephalosporin antibiotics due to their broad activity spectrum and significant consumption. Indeed, the determination of hydrolytic and photolytic kinetics provides a better comprehension of the undesired persistence of cephalosporins in aqueous matrices. In this work, the two widely used veterinary antibiotics ceftiofur (CEF) and cefapirin (CEPA) showed high instability under alkaline conditions, degrading in few minutes at pH > 11. In buffered solutions at neutral pH and natural temperature (T = 22 ± 1 °C), both drugs presented moderate stability (t½ = 3 d, CEPA and 1.4 d, CEF). Our study also demonstrated that CEPA and CEF speciation did not significantly influence the direct photolysis rates. Using a simulated water disinfection set-up (λ = 254 nm), all ionic species of CEF and CEPA presented fast and similar pseudo-first order degradation rates, k^app 0.0095 ± 0.0004 and 0.0092 ± 0.001 cm² mJ^-1, respectively. Furthermore, using surface water in hydrolysis experiments, CEF demonstrated significant matrix-dependent stability with a half-life (t½ = 14.7 d) tenfold higher than in buffered solutions. In contrast, CEPA presented a very similar hydrolysis rate in river water (t½ = 4.2 d) and a subtle faster photo-degradation rate in this same matrix (k^app 0.0128 ± 0.001 cm² mJ^-1), highlighting the importance of disinfection radiation for cephalosporin depletion in aqueous environments.

Ecotoxicity of the two veterinarian antibiotics ceftiofur and cefapirin before and after photo-transformation

The release of antibiotics into the environment may lead to deleterious effects in non-target organisms as well as pressure in antimicrobial resistance acquirement. Ceftiofur (CEF) and cefapirin (CEPA) are veterinary cephalosporins used for recurrent and economically relevant infections. Both antibiotics have been detected in aquatic environments and their fate during drinking water processing is still unknown. This work investigated the acute and chronic toxicities of CEF and CEPA towards aquatic organisms including stability tests. Complementary, the effects of water disinfection radiation (UV-C, 254nm) on ecotoxicological responses were studied. CEF and CEPA have significant decay during Daphnia magna tests, portraying half-lives (t_1/2) of 49 and 53h, respectively. During tests with green algae (Scenedesmus spec.), CEPA was more instable (t_1/2 88h) than CEF (t_1/2 267h). CEF and its presumable hydrolysis products induced deleterious effects in Daphnia magna (48h EC₅₀ 139, LC₅₀ 179 in μM), which was not observed with Scenedesmus spec. (72h NOAEC 82.5±2.5μM). In the case of CEPA, no toxic effects were observed in either test (48h EC-LC₅₀>510 and 72h NOAEC 57±6, in μM). Photolysis of CEPA resulted in toxic products, which were effective for the cladoceran but not for the green algae. On the other hand, the different radiation doses studied did not affect CEF ecotoxicity. This investigation illustrates the importance of cephalosporin hydrolysis during standard toxicity tests. Furthermore, the potential formation of species-specific toxic compounds during water processing is demonstrated, highlighting the need of further assessing toxicity of both cephalosporins and their transformation products.

Pathogen-specific responses in the bovine udder. Models and immunoprophylactic concepts

Bovine mastitis is a disease of major economic effects on the dairy industry worldwide. Experimental in vivo infection models have been widely proven as an effective tool for the investigation of pathogen-specific host immune responses. Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) are two common mastitis pathogens with an opposite clinical outcome of the disease. E. coli and S. aureus have proven to be valid surrogates to model clinical and subclinical mastitis respectively. Contemporary transcriptome profiling studies demonstrated that the transcriptomic response in the teat reflects the course of pathogen-specific mastitis, being ultimately determined by the immune response of the mammary epithelial cells. After an experimental in vivo challenge, E. coli induces a vigorous early transcriptional response in udder tissue being quantitatively and - notably - qualitatively distinct from the much weaker response against an S. aureus infection. E. coli mastitis models proved that the local response in the infected udder quarters is accompanied by a response in non-infected neighbouring udder quarters modulating systemically their immune responsiveness. Immunomodulation of the udder was investigated in animal models. Pathophysiological consequences were studied after intramammary administration of cytokines, chemokines, growth factors, steroidal anti-inflammatory drugs, or priming of tissue resident cells with pathogen-derived molecules. The latter approaches resulted only in a temporal protection of the udder, reducing transiently the risk of infection but sustained lowering of the severity of an eventually occurring mastitis. They offer an alternative to vaccination trials, which over decades also did not yield protection against new infections.

Determination of acid dissociation constants (pKa) of cephalosporin antibiotics: Computational and experimental approaches

Cefapirin (CEPA) and ceftiofur (CEF) are two examples of widely used veterinarian cephalosporins presenting multiple ionization centers. However, the acid dissociation constants (pK_a) of CEF are missing and experimental data about CEPA are rare. The same is true for many cephalosporins, where available data are either incomplete or even wrong. Environmentally relevant biotic and abiotic processes depend primordially on the antibiotic pH-dependent speciation. Consequently, this physicochemical parameter should be reliable, including the correct ionization center identification. In this direction, two experimental techniques, potentiometry and spectrophotometry, along with two well-known pK_a predictors, Marvin and ACD/Percepta, were used to study the macro dissociation constants of CEPA and CEF. Additionally, the experimental dissociation constants of 14 cephalosporins available in the literature were revised, compiled and compared with data obtained in silico. Only one value was determined experimentally for CEF (2.68 ± 0.05), which was associated to the carboxylic acid group deprotonation. For CEPA two values were obtained experimentally: 2.74 ± 0.01 for the carboxylic acid deprotonation and 5.13 ± 0.01 for the pyridinium ring deprotonation. In general, experimentally obtained values agree with the in silico predicted data (ACD/Percepta RMSE: 0.552 and Marvin RMSE: 0.706, n = 88). However, for cephalosporins having imine and aminothiazole groups structurally close, Marvin presented problems in pK_a predictions. For the biological and environmental fate and effect discussion, it is important to recognize that CEPA and CEF, as well as many other cephalosporins, are present as anionic species in the biologic and environmentally relevant pH values of 6-7.5.

Economic values for health and feed efficiency traits of dual-purpose cattle in marginal areas

Economic values of clinical mastitis, claw disease, and feed efficiency traits along with 16 additional production and functional traits were estimated for the dairy population of the Slovak Pinzgau breed using a bioeconomic approach. In the cow-calf population (suckler cow population) of the same breed, the economic values of feed efficiency traits along with 15 further production and functional traits were calculated. The marginal economic values of clinical mastitis and claw disease incidence in the dairy system were -€ 70.65 and -€ 26.73 per case per cow and year, respectively. The marginal economic values for residual feed intake were -€ 55.15 and -€ 54.64/kg of dry matter per day for cows and breeding heifers in the dairy system and -€ 20.45, -€ 11.30, and -€ 6.04/kg of dry matter per day for cows, breeding heifers, and fattened animals in the cow-calf system, respectively, all expressed per cow and year. The sums of the relative economic values for the 2 new health traits in the dairy system and for residual feed intake across all cattle categories in both systems were 1.4 and 8%, respectively. Within the dairy production system, the highest relative economic values were for milk yield (20%), daily gain of calves (20%), productive lifetime (10%), and cow conception rate (8%). In the cow-calf system, the most important traits were weight gain of calves from 120 to 210 d and from birth to 120 d (19 and 14%, respectively), productive lifetime (17%), and cow conception rate (13%). Based on the calculation of economic values for traits in the dual-purpose Pinzgau breed, milk production and growth traits remain highly important in the breeding goal, but their relative importance should be adapted to new production and economic conditions. The economic importance of functional traits (especially of cow productive lifetime and fertility) was sufficiently high to make the inclusion of these traits into the breeding goal necessary. An increased interest of consumers in animal welfare and quality of dairy farm products should probably lead to the incorporation of health traits (clinical mastitis incidence and somatic cells score) into the breeding goal. However, keeping carcass traits in the breeding goal of the Slovak Pinzgau breed does not seem to be relevant to the long-term market situation.

Polymorphisms in the promoter region of the bovine lactoferrin gene influence milk somatic cell score and milk production traits in Chinese Holstein cows

Lactoferrin is an iron-binding protein found in cow's milk that plays an important role in preventing mastitis caused by intramammary infection. In this study, 20 Chinese Holstein cows were selected randomly for PCR amplification and sequencing of the bovine lactoferrin gene promoter region and used for SNP discovery in the region between nucleotide positions -461 to -132. Three SNPs (-270T>C, -190G>A and -156A>G) were identified in bovine lactoferrin, then Chinese Holstein cows (n=866) were genotyped using Sequenom MassARRAY (Sequenom Inc., San Diego, CA) based on the previous SNP information in this study, and the associations between SNPs or haplotype and milk somatic cell score (SCS) and production traits were analyzed by the least squares method in the GLM procedure of SAS. SNPs -270T>C and -156A>G showed close linkage disequilibrium (r(2)=0.76). The SNP -190G>A showed a significant association with SCS, and individuals with genotype GG had higher SCS than genotypes AG and AA. Associations were found between the SNPs -270T>C and -190G>A with SCS and the milk composition. The software MatInspector revealed that these SNPs were located within several potential transcription factor binding sites, including NF-κB p50, KLF7 and SP1, and may alter gene expression, but further investigation will be required to elucidate the biological and practical relevance of these SNPs.

Economic values under inappropriate normal distribution assumptions

The objectives of this study were to quantify the errors in economic values (EVs) for traits affected by cost or price thresholds when skewed or kurtotic distributions of varying degree are assumed to be normal and when data with a normal distribution is subject to censoring. EVs were estimated for a continuous trait with dichotomous economic implications because of a price premium or penalty arising from a threshold ranging between -4 and 4 standard deviations from the mean. In order to evaluate the impacts of skewness, positive and negative excess kurtosis, standard skew normal, Pearson and the raised cosine distributions were used, respectively. For the various evaluable levels of skewness and kurtosis, the results showed that EVs can be underestimated or overestimated by more than 100% when price determining thresholds fall within a range from the mean that might be expected in practice. Estimates of EVs were very sensitive to censoring or missing data. In contrast to practical genetic evaluation, economic evaluation is very sensitive to lack of normality and missing data. Although in some special situations, the presence of multiple thresholds may attenuate the combined effect of errors at each threshold point, in practical situations there is a tendency for a few key thresholds to dominate the EV, and there are many situations where errors could be compounded across multiple thresholds. In the development of breeding objectives for non-normal continuous traits influenced by value thresholds, it is necessary to select a transformation that will resolve problems of non-normality or consider alternative methods that are less sensitive to non-normality.