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The warming climate is causing livestock to experience heat stress at an increasing frequency. Holstein cows are particularly susceptible to heat stress because of their high metabolic rate. Heat stress negatively affects immune function, particularly with respect to the cell-mediated immune response, which leads to increased susceptibility to disease. Cattle identified as having enhanced immune response have lower incidence of disease. Therefore, the objective of this study was to evaluate the impact of in vitro heat challenge on blood mononuclear cells from dairy cattle, that had previously been ranked for immune response, in terms of heat shock protein 70 concentration, nitric oxide production, and cell proliferation. Bovine blood mononuclear cells, from Holstein dairy cattle previously ranked for immune response based on their estimated breeding values, were subjected to three heat treatments: thermoneutral, heat stress 1 and heat stress 2. Cells of each treatment were evaluated for heat shock protein 70, cell proliferation and nitric oxide production. Blood mononuclear cells from dairy cattle classified as high immune responders, based on their estimated breeding values for antibody and cell-mediated responses, produced a significantly greater concentration of heat shock protein 70 under most heat stress treatments compared to average and low responders, and greater cell-proliferation across all treatments. Similarly, a trend was observed where high responders displayed greater nitric oxide production compared to average and low responders across heat treatments. Overall, these results suggest that blood mononuclear cells from high immune responder dairy cows are more thermotolerant compared to average and low immune responders, Comment: 37 pages, 3 figures, submitted to BMC Journal of Veterinary Research

Knowledge that certain nutraceuticals can modulate the immune system is not new. These naturally occurring compounds are known as immunoceuticals, which is a novel term that refers to products and systems that naturally improve an individual’s immuno-competence. Examples of immunoceuticals include vitamin D3, mushroom glycans, flavonols, quercetin, omega-3 fatty acids, carotenoids, and micronutrients (e.g., zinc and selenium), to name a few. The immune system is a complex and highly intricate system comprising molecules, cells, tissues, and organs that are regulated by many different genetic and environmental factors. There are instances, such as pathological conditions, in which a normal immune response is suboptimal or inappropriate and thus augmentation or tuning of the immune response by immunoceuticals may be desired. With infectious diseases, cancers, autoimmune disorders, inflammatory conditions, and allergies on the rise in both humans and animals, the importance of the use of immunoceuticals to prevent, treat, or augment the treatment of these conditions is becoming more evident as a natural and often economical approach to support wellness. The global nutraceuticals market, which includes immunoceuticals, is a multi-billion-dollar industry, with a market size value of USD 454.55 billion in 2021, which is expected to reach USD 991.09 billion by 2030. This review will provide an overview of the immune system, the importance of immunomodulation, and defining and testing for immunocompetence, followed by a discussion of several key immunoceuticals with clinically proven and evidence-based immunomodulatory properties.

Bovine milk contains bioactive components that are nutritionally and immunologically important to calves and humans. Dairy cows classified as high (H) immune responders using the patented high immune response technology have higher concentrations of immunoglobulin and specific antibodies in sera and milk compared with average (A) and low (L) responders. MicroRNA post-transcriptionally regulate expression of milk bioactive components and are enriched in extracellular vesicles known as exosomes, which protect them from degradation. The bioactivity of colostrum and milk exosomes at the human intestinal epithelial barrier remains to be explored, particularly in the context of the high immune response technology. Therefore, the purpose of this study was to evaluate the functional role of bovine milk exosomes compared with colostrum exosomes from H, A, and L responders at the intestinal interface using human colorectal adenocarcinoma epithelial (Caco-2) cells. Exosomes were isolated by successive ultracentrifugation and confirmed by western blot analysis for the presence of common exosomal proteins (CD9, CD63, and heat shock protein 70). Fluorescent labeling of exosomes using PKH67 dye confirmed their uptake by Caco-2 cells, demonstrating their potential bioavailability. The MTT assays showed that colostrum and milk exosomes maintain Caco-2 metabolic activity and are not cytotoxic to these cells. Specifically, metabolic activity after co-incubation with colostrum and milk exosomes from H responder cows was significantly greater than after co-incubation with exosomes from L responders. Caspase 3 activity, an indicator of apoptosis, was significantly lower after co-incubation of Caco-2 cells with milk exosomes compared with colostrum exosomes, suggesting that unlike colostrum exosomes, particularly those from L responders, milk exosomes do not activate the caspase 3 pathway in Caco-2 cells. This study helps us better understand the functional importance of colostrum and milk exosomes from dairy cows and emphasizes differences in functionality among exosomes from H, A, and L immune responders.

Breeding stress-resilient livestock is a potential strategy to help mitigate the negative effect of environmental and pathogenic stressors. The hypothalamic-pituitary-adrenal axis and immune system are activated during stress events and release mediators into the circulation that help restore physiological homeostasis. The purpose of this study was to assess a comprehensive set of circulatory mediators released in response to an acute immune stress challenge to identify candidate biomarkers that can be used for the selection of stress-resilient animals. Fifteen female lambs were stress challenged with an intravenous bolus of lipopolysaccharide (LPS; 400 ng/kg), and blood was collected from the jugular vein at 0, 2, 4, and 6 h after LPS challenge to identify and monitor candidate stress biomarkers; temperature was also recorded over time. Biomarker responses were evaluated with a repeated-measures model to compare time points with baseline values. As expected, all sheep had a monophasic febrile response to LPS challenge, and cortisol increased and returned to baseline by 6 h. The cytokines tumor necrosis factor-α, IL-6, IFN-γ (proinflammatory), and IL-10 (anti-inflammatory) increased, but only tumor necrosis factor-α returned to baseline during the monitoring period. The cytokines IL-1α, IL-1β, IL-17α (proinflammatory), and IL-4 (anti-inflammatory) did not respond to LPS challenge. All chemokines (CCL2, CCL3, CCL4, CXCL10, and IL-8) responded to LPS challenge; however, only CCL2, CCL3, CCL4, and CXCL10 increased over time, and only CCL3, CCL4, and CXCL10 returned to baseline during the monitoring period. MicroRNA (miR-145, miR-233, and miR-1246) also increased and remained elevated during the study. In summary, the LPS challenge induced a strong stress response in Rideau-Dorset sheep that could be monitored with a distinct profile of circulatory biomarkers.

Immunoglobulin (Ig) G and natural antibody (NAb) IgM are passively transferred to the neonatal calf through bovine colostrum. Maternal IgG provides pathogen- or vaccine-specific protection and comprises about 85% of colostral Ig. NAb-IgM is less abundant but provides broad and nonspecific reactivity, potentially contributing to protection against the dissemination of pathogens in the blood (septicemia) in a calf's first days of life. In the dairy and beef industries, failure of passive transfer (FPT) of colostral Ig (serum total protein [STP]5.2 g/dL) is still a common concern. The objectives of this study were to: (1) compare colostral IgG concentrations and NAb-IgM titers between dairy and beef cows; (2) assess the effect of beef breed on colostral IgG; (3) compare passive transfer of colostral Ig in dairy and beef calves; and (4) estimate the heritability of colostral IgG and NAb-IgM. Colostrum was collected from Holstein dairy (n = 282) and crossbred beef (n = 168) cows at the University of Guelph dairy and beef research centers. Colostral IgG was quantified by radial immunodiffusion and NAb-IgM was quantified by an enzyme-linked immunosorbent assay. In dairy (n = 308) and beef (n = 169) calves, STP was estimated by digital refractometry. Beef cows had significantly greater colostral IgG (146.5 ± 9.5 standard error of the mean [SEM] g/L) than dairy cows (92.4 ± 5.2 g/L, P0.01). Beef cows with a higher proportion of Angus ancestry had significantly lower colostral IgG (125.5 ± 5.8 g/L) than cows grouped as "Other" (142.5 ± 4.9 g/L, P = 0.02). Using the FPT cutoff, 13% of dairy and 16% of beef calves had FPT; still, beef calves had a significantly larger proportion with excellent passive transfer (STP ≥6.2 g/dL, P0.01). The heritability of colostral IgG was 0.04 (±0.14) in dairy and 0.14 (±0.32) in beef. Colostral NAb-IgM titers in dairy (12.12 ± 0.22, log2 [reciprocal of titer]) and beef cows (12.03 ± 0.19) did not differ significantly (P = 0.71). The range of NAb-IgM titers was 9.18-14.60, equivalent to a 42-fold range in antibody concentration. The heritability of colostral NAb was 0.24 (±0.16) in dairy and 0.11 (±0.19) in beef cows. This study is the first to compare colostral NAb-IgM between dairy and beef cows. Based on the range in NAb-IgM titers and the heritability, selective breeding may improve colostrum quality and protection for neonatal calves in the early days of life.Understanding how breed influences immunoglobulin (Ig) G and natural antibody (NAb) IgM concentrations in colostrum can improve bovine colostrum quality and calf health. Maternal colostral IgG is abundant, persistent, and pathogen specific. Natural antibody-IgM is less abundant but mediates broad, short-lived, nonspecific pathogen protection, and potentially important against septicemia. Colostral IgG and NAb-IgM concentrations were compared between dairy and beef cows and among cross-bred beef cows. Heritabilities were calculated to assess the practicality of selective breeding. Serum total protein (STP) in neonatal dairy and beef calves was estimated using refractometry. Colostrum from beef cows had higher concentrations of IgG than dairy cows. Beef cows with higher Angus ancestry produced colostrum with lower IgG concentrations than other mixed breeds. Heritability of colostral IgG was low (0.04–0.14). Failure of passive transfer was similar in dairy and beef calves, but a significantly larger proportion of beef calves had excellent STP (≥6.2 g/dL). There were no differences in NAb-IgM titers between dairy and beef cows or among beef breeds. Colostral NAb-IgM varied widely among individuals (42-fold) and was moderately heritable (0.11–0.24). These results suggest that selective breeding to improve colostrum quality is feasible and practical to improve calf health.

Individual variation of the hypothalamic-pituitary-adrenal (HPA) axis response to stress could contribute to variable stress resiliency of livestock. During stress events, the innate immune system can also become activated and work in concert with the neuroendocrine system to restore homeostasis, while minimizing tissue damage. The purpose of this study was to assess immune function in variable stress-responding sheep in response to bacterial lipopolysaccharide (LPS) endotoxin immune-challenge. High (HSR, n = 12), middle (MSR, n = 12), and low-stress responders (LSR, n = 12) were selected from a population of 112 female lambs and classified based on serum cortisol concentration after receiving an intravenous bolus of LPS (400 ng/kg). Blood was collected from the jugular vein at 0 and 4 hrs post-LPS challenge to monitor changes in serum pro- and anti-inflammatory cytokines and chemokines, and white blood cell populations. Rectal temperature was recorded hourly to monitor fever. HSR had the greatest increase in rectal temperature and strongest pro-inflammatory IL-6 and IFN-γ cytokine responses compared to MSR and LSR. HSR and MSR had stronger anti-inflammatory IL-10 cytokine and CCL2 chemokine responses than LSR. White blood cell counts changed between 0 and 4 h; however, no differences were detected among the variable stress response groups. The distinct inflammatory response in variable stress responding sheep could contribute to individual differences in stress resiliency and this warrants investigation in the context of other types of stress.

Infectious diseases are the outcome of complex interactions between the host, pathogen, and environment. After exposure to a pathogen, the host immune system uses various mechanisms to remove the pathogen. However, environmental factors and characteristics of pathogens can compromise the host immune responses and subsequently alter the outcome of infection. In this article, genetic and epigenetic factors that shape the individual variation in mounting protective responses are reviewed. Different approaches that have been used by researchers to investigate the genetic regulation of immunity in ruminants and various sources of genetic information are discussed.

Heat stress negatively affects health and production in cows. Examining the cellular response to heat stress could reveal underlying protective molecular mechanisms associated with superior resilience and ultimately enable selection for more resilient cattle. This type of investigation is increasingly important as future predictions for the patterns of heat waves point to increases in frequency, severity, and duration. Cows identified as high immune responders based on High Immune Response technology (HIR) have lower disease occurrence compared to their average and low immune responder herd-mates. In this study, our goal was to identify epigenetic differences between high and low immune responder cows in response to heat stress. We examined genome-wide DNA methylation of blood mononuclear cells (BMCs) isolated from high and low cows, before and after in vitro heat stress. We identified differential methylation of promoter regions associated with a variety of biological processes including immune function, stress response, apoptosis, and cell signalling. The specific differentially methylated promoter regions differed between samples from high and low cows, and results revealed pathways associated with cellular protection during heat stress.

The high immune response (HIR) methodology measures the genetic performance of the adaptive immune system to identify and breed animals with balanced and robust immunity. The HIR methodology has previously been used in dairy and swine to reduce disease but has not been fully investigated in beef cattle. The first objective of the current study was to examine whether the HIR methodology as standardized for use in dairy cattle was appropriate for use in beef cattle. The second objective was to determine the earliest age for immune response phenotyping of beef calves. In this study, beef calves (n = 295) of various ages, as well as mature beef cows (n = 170) of mixed breeds, were immunized using test antigens to assess their antibody- (AMIR) and cell-mediated immune responses (CMIR). Heritability for AMIR and CMIR was estimated at 0.43 and 0.18, respectively. The HIR methodology was appropriate for use in beef cattle; beef calves as young as 2–3 wk of age were capable of mounting AMIR responses comparable with those seen historically in mature Holstein dairy cows. Three-week-old beef calves mounted CMIR responses comparable with those of Holstein cows, but 9-mo-old calves and mature beef cows had significantly higher CMIR responses than Holsteins. The HIR methodology can be used to measure both AMIR and CMIR in beef calves as young as 3 wk of age.

Pathogens induce neuroendocrine-immune interactions in their hosts, which are a basis to overcome the microbial stressor. These interactions result in individual variation of the hypothalamic-pituitary-adrenal (HPA) axis response and could contribute to variable stress resiliency. In present study, a comprehensive set of circulatory markers was assessed in variable stress responding lambs selected from a population (n = 112) and categorized based on cortisol levels as high (HSR, 336.2 ±27.9 nmol/L, n =12), middle (MSR, 147.3 ±9.5 nmol/L, n =12) and low (LSR, 32.1 ±10.4 nmol/L, n =12) responding phenotypes post LPS challenge (400 ng/kg iv). Blood was collected from the jugular vein at 0 (pre-) and 4 hrs post-LPS challenge to monitor changes in serum with a panel of 15 pro- and anti-inflammatory cytokines and chemokines and 84 miRNAs, and white blood cell (WBC) populations. The HSR had the strongest fever and pro-inflammatory IL-6, IFN-γ cytokine responses compared to MSR and LSR. HSR and MSR had stronger anti-inflammatory IL-10 cytokine and CCL2 chemokine responses than LSR. WBC counts changed between 0 and 4 hrs; however, no differences were detected among the variable stress response groups. Three miRNAs, oar-miR-485-5p (+3.82 folds), oar-miR-1193-5p (+2.43 folds) and oar-miR-3957-5p (+3.14 folds) were significantly (P < 0.05) upregulated, and seven miRNAs, oar-miR-376b-3p (-6.6 fold), oar-miR-376c-3p (3.5 folds), oar-miR-411b-5p (-11.69 folds), (oar-miR-376a-3p (-2.28 fold), oar-miR-376b-3p (-6.08 folds), oar-miR-376c-3p (-2.62 folds), oar-miR-381-3p (-3.85 folds) were downregulated (P < 0.05) in HSR compared to LSR and MSR. Functional analysis of miRNAs revealed their roles in activating TGF-beta signalling, Cytokine receptor interaction and Thyroid signalling pathways in HSR phenotypes indicating a hyper-induced acute-phase response. In summary, these results indicate variation in the acute-phase response to stress, and some of these markers could be used as stress biomarkers. Further investigation is warranted to understand the plausible association of cortisol phenotype with other important traits.

Including immune response traits in breeding programs has been suggested as a solution to improve overall animal health and enhance disease resistance but is not yet available for Angus cattle in North America. One way to measure immune response is to use the High Immune Response (HIR™) technology, which identifies animals with superior heritable immunity by evaluating antibody-mediated (AMIR) and cell-mediated (CMIR) immune response, allowing for the calculation of an estimated breeding value for total adaptive immune response for each animal. Before HIR™ can be included in beef cattle breeding programs, genetic parameters, including heritability, must be estimated for the traits involved. The objective of this study was to estimate a preliminary heritability for AMIR and CMIR in North American Angus beef cattle. On day 0 of the phenotyping protocol, cattle were immunized intramuscularly with a preparation of type 1 (CMIR) and type 2 (AMIR) antigens with adjuvant. On day 14, cattle received an intradermal injection of 0.1 mL of the CMIR test antigen in the right tail fold, and 0.1 mL PBS in the left tail fold. Change in cutaneous double skinfold thickness after 24 hours was used to assess CMIR. Blood was collected on days 0 and 14 to evaluate serum antibody to the type 2 antigen by ELISA to quantify AMIR. Heritability estimates were calculated for Canada and the USA separately, and then for both countries combined using single-trait animal models in ASReml and are presented in Table 1. The results of this study indicate that the heritabilities of AMIR and CMIR are moderate and emphasize the potential for its inclusion into Angus breeding schemes.

Host&ndash, pathogen interactions are complex and influenced by host genetic and epigenetic modifications. Recently, the significance of microRNAs (miRNAs) in pathogenic infection and the regulation of immune response has been highlighted. However, information on miRNAs&rsquo, role in the course of inflammation is still very limited in small ruminants. The present study was intended to identify changes in the expression of circulatory miRNAs post-lipopolysaccharide (LPS)-challenge. In this study, young ewes (n = 18) were challenged with Escherichia coli LPS (400 ng/kg i.v.) and blood samples were collected for serum miRNA isolation at two-time points, prior to challenge (T0), and 4 h (T4) post-challenge, reflecting the peak cortisol response. A total of 91 miRNAs were profiled, including 84 miRNAs on a commercial ovine miRNA-PCR array, and seven individual miRNAs. Forty five miRNAs were differentially expressed (DE) with 35 being up-regulated (Fold regulation, FR &gt, 2) and 10 being down-regulated (FR &lt, 1, p &lt, 0.05) at T4. Among the up-regulated miRNAs, 14 were significantly (p &lt, 0.05) induced, including oar-miRs: 369-3p, 495-3p, 376a-3p, 543-3p, 668-3p, 329a-3p, 655-3p, 411a-5p, and 154a-3p, which were located on ovine chromosome 18 forming four miRNA clusters within 10 kb. The elevated miRNAs belonged to different functional classes, playing roles in activating the hypothalamic-pituitary-adrenal axis, increasing cell survival and differentiation, and inducing inflammatory responses and targeted PI3K-Akt and MAPK signaling and chemokine signaling pathways. In summary, these results reveal the dynamic nature of ovine serum miRNAs during LPS-induced stress and highlight the potential role of identified miRNA-clusters on chromosome 18 to understand the regulation of the acute-phase response. Some of these identified circulating miRNAs may also serve as stress biomarkers for livestock in the future.

Reactive Nitrogen Species (RNS) are a group of bactericidal molecules produced by macrophages in response to pathogens in a process called oxidative burst. Nitric oxide (NO−) is a member of RNS produced from arginine by inducible Nitric Oxide Synthase (iNOS) enzyme. The activity of iNOS and production of NO− by macrophages following stimulation is one of the indicators of macrophage polarization towards M1/proinflammatory. Production of NO− by bovine monocyte-derived macrophage (MDM) and mouse peritoneal macrophages has been shown to be strongly associated with host genetic with the heritability of 0.776 in bovine MDM and 0.8 in mouse peritoneal macrophages. However, the mechanism of genetic regulation of macrophage response has remained less explored. In the current study, the transcriptome of bovine MDMs was compared between two extreme phenotypes that had been classified as high and low responder based on NO− production. The results showed that 179 and 392 genes were differentially expressed (DE) between high and low responder groups at 3 and 18 hours after exposure to Escherichia coli, respectively. A set of 11 Transcription Factors (TFs) (STAT1, IRF7, SPI1, STAT4, IRF1, HIF1A, FOXO3, REL, NFAT5, HIC1, and IRF4) at 3 hours and a set of 13 TFs (STAT1, IRF1, HIF1A, STAT4, ATF4, TP63, EGR1, CDKN2A, RBL1, E2F1, PRDM1, GATA3, and IRF4) at 18 hours after exposure to E. coli were identified to be differentially regulated between the high and low responder phenotypes. These TFs were found to be divided into two clusters of inflammatory- and hypoxia-related TFs. Functional analysis revealed that some key canonical pathways such as phagocytosis, chemotaxis, antigen presentation, and cell-to-cell signalling are enriched among the over-expressed genes by high responder phenotype. Based on the results of this study, it was inferred that the functional characteristics of bovine MDMs are associated with NO-based classification. Since NO− production is strongly associated with host genetics, this study for the first time shows the distinct proinflammatory profiles of macrophages are controlled by the natural genetic polymorphism in an outbred population. In addition, the results suggest that genetics can be considered as a new dimension in the current model of macrophage polarization which is currently described by the combination of stimulants, only.

The objective of this research was to estimate the genetic correlations between milk mid-infrared-predicted fatty acid groups and production traits in first-parity Canadian Holsteins. Contents of short-chain, medium-chain, long-chain, saturated, and unsaturated fatty acid groupings in milk samples can be predicted using mid-infrared spectral data for cows enrolled in milk recording programs. Predicted fatty acid group contents were obtained for 49,127 test-day milk samples from 10,029 first-parity Holstein cows in 810 herds. Milk yield, fat and protein yield, fat and protein percentage, fat-to-protein ratio, and somatic cell score were also available for these test days. Genetic parameters were estimated for the fatty acid groups and production traits using multiple-trait random regression test day models by Bayesian methods via Gibbs sampling. Three separate 8- or 9-trait analyses were performed, including the 5 fatty acid groups with different combinations of the production traits. Posterior standard deviations ranged from

The peripartum period is a period of high stress, transition and management changes for dairy cows. It is associated with higher incidence of both metabolic and pathogenic disease. Both antibody-(AMIR) and cell-(CMIR) mediated immune responses play a key role in the maintenance of health in mammals protecting against extracellular and intracellular pathogens, respectively. Generally, interferon gamma (IFN-γ) has been associated with CMIR, whereas interleukin 4 (IL-4) has been associated with AMIR bias, and interleukin 17 (IL-17A) is associated with pro-inflammatory. It has been previously demonstrated that cows can be classified as high (H), average (A), and low (L) immune responders based upon their AMIR and CMIR to test antigens, and that this classification is associated with disease occurrence throughout lactation. The mechanisms behind these differences in phenotype and the effects of the peripartum period have not been fully investigated. The aim of this study was to determine the effects of the peripartum period on cytokine production of CD4+ T-cells or T helper (Th) cells, key mediators of the adaptive immune response. Immune response phenotyped cows were selected based on H-AMIR/L-CMIR (H-AMIR cows; n = 10) and H-CMIR/L-AMIR (H-CMIR cows; n = 11) response to test antigens. Isolated CD4+ T-cells collected at 28 days before calving (prepartum samples), 4 days after calving (early postpartum samples), and 21 days after calving (late postpartum samples) from these groups were stimulated with Concanavalin-A (ConA) with unstimulated controls. Subsequently, IL-4, IFN-γ, and IL-17A concentrations were quantified by ELISA. Overall, there was no obvious decline in IL-4, IFN-γ or IL-17A close to calving observed from CD4+ T-cells from each of these phenotypically distinct groups of cows. However, CD4+ T-cells isolated from H-CMIR secreted higher amounts of IL-4 (746.43 ± 428 pg/mL), IL-17A (446IL ± 62 pg/mL), and IFN-γ (7755.79 ± 4449 pg/mL) than H-AMIR cows (IL-4 (212.15 ± 121 pg/mL), IL-17A (163.15 ± 87 pg/mL), and IFN-γ (2909.771 ± 1671 pg/mL)) on day 21 after calving, late postpartum. This study indicates a genetic predisposition based on immune response phenotype of cytokine production from CD4+ T-cells around calving.

The fatty acid profile of milk is a prevailing issue due to the potential negative or positive effects of different fatty acids to human health and nutrition. Mid-infrared spectroscopy can be used to obtain predictions of otherwise costly fatty acid phenotypes in a widespread and rapid manner. The objective of this study was to evaluate the prediction of fatty acid content for the Canadian dairy cattle population from mid-infrared spectral data and to compare the results produced by altering the partial least squares (PLS) model development set used. The PLS model development sets used to develop the predictions were reference fatty acids expressed as (1) grams per 100 g of fatty acid, (2) grams per 100 g of milk, (3) the natural logarithmic transform of grams per 100 g of milk, and (4) subsets of samples randomly selected by removing excess records around the mean to present a more uniform distribution, repeated 10 times. Gas chromatography measured fatty acid concentration and spectral data for 2,023 milk samples of 373 cows from 4 breeds and 44 herds were used in the model development. The coefficient of determination of cross-validation (Rcv2) increased when fatty acids were expressed on a per 100 g of milk basis compared with on a per 100 g of fat basis for all examined fatty acids. The logarithmic transformation used to create a more Gaussian distribution in the development set had little effect on the prediction accuracy. The individual fatty acids C12:0, C14:0, C16:0, C18:0, C18:1n-9 cis, and saturated, monounsaturated, unsaturated, short-chain, medium-chain, and long-chain fatty acid groups had (Rcv2) greater than 0.70. When model development was performed with subsets of the original samples, slight increases in (Rcv2) values were observed for the majority of fatty acids. The difference in (Rcv2) between the top- and bottom-performing prediction equation across the different subsets for a single predicted fatty acid was on average 0.055 depending on which samples were randomly selected to be used in the PLS model development set. Predictions for fatty acids with high accuracies can be used to monitor fatty acid contents for cows in milk recording programs and possibly for genetic evaluation.

The objective of this study was to estimate the heritability of milk fat globule (MFG) size and mid-infrared (MIR) predicted MFG size in Holstein cattle. The genetic correlations between measured and predicted MFG size with milk fat and protein percentage were also investigated. Average MFG size was measured in 1,583 milk samples taken from 254 Holstein cows from 29 herds across Canada. Size was expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). Analyzed milk samples also had average MFG size predicted from their MIR spectral records. Fat and protein percentages were obtained for all test-day milk samples in the cow's lactation. Univariate and bivariate repeatability animal models were used to estimate heritability and genetic correlations. Moderate heritabilities of 0.364 and 0.466 were found for D[4,3] and D[3,2], respectively, and a strong genetic correlation was found between the 2 traits (0.98). The heritabilities for the MIR-predicted MFG size were lower than those estimated for the measured MFG size at 0.300 for predicted D[4,3] and 0.239 for predicted D[3,2]. The genetic correlation between measured and predicted D[4,3] was 0.685; the correlation was slightly higher between measured and predicted D[3,2] at 0.764, likely due to the better prediction accuracy of D[3,2]. Milk fat percentage had moderate genetic correlations with both D[4,3] and D[3,2] (0.538 and 0.681, respectively). The genetic correlation between predicted MFG size and fat percentage was much stronger (greater than 0.97 for both predicted D[4,3] and D[3,2]). The stronger correlation suggests a limitation for the use of the predicted values of MFG size as indicator traits for true average MFG size in milk in selection programs. Larger samples sizes are required to provide better evidence of the estimated genetic parameters. A genetic component appears to exist for the average MFG size in bovine milk, and the variation could be exploited in selection programs.

Mastitis is a very costly and common disease in the dairy industry. The study of the transcriptome from healthy and mastitic milk somatic cell samples using RNA-Sequencing technology can provide measurements of transcript levels associated with the immune response to the infection. The objective of this study was to characterize the Holstein milk somatic cell transcriptome from 6 cows to determine host response to intramammary infections. RNA-Sequencing was performed on 2 samples from each cow from 2 separate quarters, one classified as healthy (n = 6) and one as mastitic (n = 6). In total, 449 genes were differentially expressed between the healthy and mastitic quarters (false discovery rate0.05, fold change±2). Among the differentially expressed genes, the most expressed genes based on reads per kilobase per million mapped reads (RPKM) in the healthy group were associated with milk components (CSN2 and CSN3), and in the mastitic group they were associated with immunity (B2M and CD74). In silico functional analysis was performed using the list of 449 differentially expressed genes, which identified 36 significantly enriched metabolic pathways (false discovery rate0.01), some of which were associated with the immune system, such as cytokine-cytokine interaction and cell adhesion molecules. Seven functional candidate genes were selected, based on the criteria of being highly differentially expressed between healthy and mastitic groups and significantly enriched in metabolic pathways that are relevant to the inflammatory process (GLYCAM1, B2M, CD74, BoLA-DRA, FCER1G, SDS, and NFKBIA). Last, we identified the differentially expressed genes that are located in quantitative trait locus regions previously known to be associated with mastitis, specifically clinical mastitis, somatic cell count, and somatic cell score. It was concluded that multiple genes within quantitative trait locus regions could potentially affect host response to mastitis-causing agents, making some cows more susceptible to intramammary infections. The identification of potential candidate genes with functional, statistical, biological, and positional relevance associated with host defense to infection will contribute to a better understanding of the underlying genetic architecture associated with mastitis. This in turn will improve the sustainability of agricultural practices by facilitating the selection of cows with improved host defense leading to increased resistance to mastitis.

Dairy cattle evaluated for immune responses and identified as high responders are known to have a lower occurrence of economically important diseases, including mastitis, metritis, ketosis, and retained placenta. These high immune responders have also been shown to make more antibody following vaccination and to have improved milk and colostrum quality. Therefore, breeding for improved immune response is expected to have several benefits in the dairy industry. However, a concern of such an approach to improve animal health is the potential cost of lost production due to an allocation of host resources to mount a robust immune response. The objective of this study was to evaluate early- and late-lactation production parameters in cattle classified as having high, average, or low estimated breeding values (EBV) for cell-mediated (CMIR), antibody-mediated (AMIR), and overall immune responses. A total of 561 cows from 6 herds were phenotyped for immune response and ranked based on EBV for CMIR and AMIR. A linear animal model was used to evaluate differences in milk, fat, and protein yields among immune response groups, and a regression analysis was conducted based on immune response EBV. Overall, no difference in production parameters was found based on immune response rank; however, some positive relationships with immune response EBV were found, suggesting that breeding for enhanced immune responsiveness as a prophylactic approach to improve animal health would not come at the cost of lost production.

As the temperature-humidity index (THI) increases, animals are less able to regulate body temperature leading to decreases in production and immune function. The High Immune Response (HIR™) technology classifies animals based on estimated breeding values (EBVs) of their IR capacity as high (H), average (A), or low (L). H-responders with their unique IR genotype have less disease than A or L, but have not been evaluated for adaptation to heat stress. Therefore, rectal temperatures of beef & dairy cows with known IR classification were recorded during THI< 74 (normal) and THI>74 (above normal). Results show that 50% of beef & 65% of dairy cows had body temperature above 39.2 at THI>74. However, cows that ranked H for antibody response were significantly better at regulating temperature and respiration at THI>74, than A or L. In vitro experiments showed variability in PBMC function when cells were heat stressed (42□, 4hrs). PBMC were stimulated with ConA to measure proliferation or LPS to assess nitric oxide (NO) production. HSP70 was measured in control and heat treated cells. Dairy results indicated that H responders had significantly greater cell proliferation across all treatments and greater NO and HSP production with significance depending on the treatment. Beef results indicate that HSP70 from unstimulated PBMC increased after 1 or 2 heat treatments, and the magnitude of the change varied by IR class. Conversely, PBMCs challenged with LPS produced more NO before than after heat treatments. These results indicate that cattle with diverse immune response genotypes vary in their ability to withstand heat stress, and that it should be possible to identify resilient individuals with both greater immunity and adaptation to climate warming.

Climate change with increases in ambient temperature and humidity, affect animal life dramatically decreasing their production and reproduction potential, as well as making them more susceptible to different diseases. This leads to an increase in their core body temperature and respiration rate which in turn decreases their production, reproduction, and immune function. The High Immune Response (HIR™) technology which has been developed at the University of Guelph ranks animals using two arms of adaptive immune system to high (H), average (A), and low (L) immune responders. (H) immune responders have been reported to have fewer incidents of disease and robust immune response. (H) immune responders have been also reported to have better colostrum and milk quality making them an ideal model to examine the effects of climate change on health traits. The objective of this study was to check if (H) immune responder beef cattle are able to regulate their rectal temperature better. In this study, rectal temperatures of 36 beef cows were recorded during normal Temperature-Humidity Index (THI This is the first time that genetic regulation of an immune response trait has been shown to influence the response to in vivo heat stress indicating that it may be possible to select cattle with both improved health and heat tolerance.

Stress is known to contribute to variation in cell-mediated (CMIR) and antibody-mediated (AbMIR) immune responses. Our group previously demonstrated that variation in the ovine cortisol response to immune stress challenge with Escherichia coli lipopolysaccharide (LPS) was associated with immunity; high (HSR) and low (LSR) stress-responsive sheep exhibited heightened CMIR and attenuated AbMIR compared to middle (MSR) stress responders. However, the association of this stress response phenotype with resistance to gastrointestinal nematodes (GIN) has not been investigated, which was the focus of this study. Two hundred GIN-naïve Rideau lambs were LPS challenged, and the peak cortisol response was used to select 15 HSR lambs and 15 MSR lambs from the population. These lambs were then naturally challenged with GINs while co-grazing with a commercial flock in Ontario known to carry GINs for five months in 2016. Infection was confirmed by monitoring fecal egg counts (FEC) every 6–8 weeks, and at the end of the grazing season, the HSR and MSR lambs (n=30) were euthanized to assess GIN burden (abomasum and small intestine). Two-sample T-tests were performed to compare FEC and GIN burden between the HSR and MSR sheep. No significant differences were found in FEC at any of the sampling time points, or in the end-of-season GIN burden. It is possible that the parasite challenge was insufficient to reveal differences in GIN resistance between the groups, since pasture burden was unusually low due to a record drought during the 2016 grazing season. Further investigation into other health phenotypes that may influence GIN resistance, such as high immune response, is warranted.

Concerns regarding food safety and animal health require more effective alternatives with the potential to improve health and productivity. High Immune Response (HIR™) technology is a patented method to identify animals with inherently more robust, balanced and protective immune responses. This approach has been shown to decrease disease incidence in pigs and dairy cattle by about half. Economic benefits of high immune responder dairy cows are in the range of $240/cow/lactation, including reduced treatment costs. Our research focus is on adapting HIR™ for use in Canadian beef feedlots to decrease economically important diseases such as Bovine Respiratory Disease (BRD). HIR test measures IR to non-replicating test antigens (Ag) to elicit both antibody-mediated IR (AMIR) and cell-mediated IR (CMIR). Results on 170 cows of mixed breeds and 126 of their calves at the university research facility demonstrate that calves as young as 3 weeks of age and mature cattle can be ranked for AMIR and CMIR using the HIR test system. A SAS GLM model was used to evaluate the effects of age of dam, parity, and breed composition (y = mu + age + calf/no-calf + breed + error) on IR rank. Regression analysis was used to examine associations between serum IgG of cows and their calves. Results indicated a slight positive correlation between serum IgG in calves of the same dam (R2 = 0.097) when animals of all parities were evaluated, and a greater association was noted when only heifers were evaluated in their first two parities (R2 = 0.64). However, there was no association between AMIR rank of the dam and serum IgG of the calf. There was slight positive association between CMIR rank of the dam and serum IgG of the calf (R2 = 0.05). More dam-calf pairs will be evaluated in the future.

There is a pressing need to identify high producing dairy cows resilient to physiological challenges from climate change. Cows that have high estimated breeding values for Cell-Mediated Immune Response (CMIR) and high Antibody-Mediated Immune Response (AMIR) are at lower risk of developing disease (e.g. mastitis, metritis, hoof lesions) and are less likely to require antibiotics, compared to herd mates. However, no published studies have yet examined the physiological impact of climate change on immuno-phenotyped dairy cows. We hypothesize that high immune response (IR) cows are more resilient to climate change compared to average or low IR. To date, we have investigated the thermoregulation abilities of 10 average IR, lactating cows (8 multiparous, 2 first lactation) randomly selected from two commercial herds in southwestern Ontario. Rectal tempeartures (RT) from these cows were recorded during morning and evening milking over three days at the end of a heatwave in September 2017. The first two days were 10–18°C above seasonal average (20°C) while the third day was 5–10°C below average. A simple ANOVA was performed using evening RT, which indicated a significant difference (p=1.41 e-7) between cows for mean evening RT, with the highest mean RT and highest ambient temperature occuring on the same day. There is significant positive correlation (r=0.68, p=1.38 e-6) between RT and ambient temperature during the study. The low p-value (p=0.07) in an asymptotic test (t=15.89) suggests that the between-cow variation in RT is not due to chance. This variation in thermoregulation between cows during heat stress is under further investigation comparing average (control group) IR to high and low IR cows across multiple herds. Genetic selection for increased climate resilience may be warranted as more information is acquired on the heritability and benefits of this trait in Canadian Holstein, particularly in the context of immunity.

Background Natural antibodies (NAb) are an important component of the innate immune system, and fight infections as a part of the first line defence. NAb are poly-reactive and can respond non-specifically to antigens. Therefore, NAb may be a key trait when evaluating an animal’s potential natural disease resistance. Variation in NAb is caused by both genetic and environmental factors. In this study genetic parameters of NAb were estimated and a genome-wide association study (GWAS) was performed to gain further understanding on the genes that are responsible for the observed genetic variation of NAb in Canadian Holsteins. Results In total, blood samples of 1327 cows from 64 farms were studied. NAb binding to keyhole limpet hemocyanin (KLH) were determined via indirect ELISA. Immunoglobulin (Ig) isotypes, IgG and IgM, were evaluated. From the sample population, 925 cows were genotyped for 45,187 markers and each individual marker was tested to detect genetic variation in NAb levels. The relationships among animals was accounted for with genomic relationship. Results show heritabilities of 0.27 ± 0.064 (IgG) and 0.31 ± 0.065 (IgM). In total, 23 SNPs were found to be associated with IgG, but no SNPs were associated with IgM (FDR p-value

The objectives of this study were to assess antibody and cellular immune responses in first-lactation dairy heifers reared under a pasture-based production system and to investigate associations between immune competence and stress responsiveness, health, and productivity. A commercial vaccine was used to induce antibody and cellular immune responses and, based on measured responses, animals were classified as above average, average, and below average for each trait independently and in combination (overall immune competence). Overall immune competence phenotypic rankings were generated by combining standardized residual values for antibody and cellular responses measured in individual heifers. Cortisol responses to handling and yarding were used to assess stress responsiveness, worm egg counts were used to assess internal parasite burden, somatic cell counts to assess udder health and estimates of total daily milk volume, and milk fat and milk protein contents to assess productivity. A total of 393 Holstein-Friesian and Holstein-Friesian × Jersey crossbred heifers from 2 herds practicing seasonal calving in a pasture-fed production system were enrolled in the study. The immune competence phenotypes of individual heifers were assessed before their first mating and their subsequent performance during their first lactation was monitored. Animals with below-average antibody and cellular immune competence had higher serum cortisol concentrations compared with their counterparts following handling, suggesting they had a reduced ability to cope with management-induced stress. Furthermore, a significant negative (favorable) correlation was observed between antibody responses and stress responsiveness. Similarly, correlations between antibody responses and internal parasite burden were significant and negative (favorable). No correlations were observed between overall immune competence and milk yield, milk fat, and milk protein content.

The objective of this study was to determine the repeatability of ranking Holstein-Friesian heifers reared in an Australian pasture-based production system for immune responses (IR) when ranking was based on secondary versus tertiary IR. Further objectives were to investigate associations between IR and stress responsiveness, ADG and resistance to internal parasites. A total of 100 heifers were IR phenotyped at 5 to 6 mo of age and again at 12 to 13 mo of age using commercial vaccine antigens to induce measurable IR. Antibody production to tetanus toxoid (TT) was used to assess antibody-mediated IR (AMIR), and delayed-type hypersensitivity reactions to vaccine antigens were used to assess cell-mediated IR (CMIR). Changes in serum cortisol and haptoglobin were used to assess stress responsiveness and fecal egg counts used as a measure of resistance to internal parasites. Based on testing, animals were categorized as either average to above-average (High) or low responders for IR. Secondary and tertiary AMIR were well correlated (r = 0.651, adjusted R(2) = 0.418, P < 0.0001), whereas correlations between secondary and tertiary CMIR were poor (r = 0.078, R(2) = –0.004, P = 0.450). A Cohen kappa (κ) test of agreement was used to test the consistency of ranking of individual animal for IR and, therefore, the ability to consistently identify low immune responder animals within the herd across test periods. The consistency of ranking (High versus low) was moderately high for AMIR (κ = 0.445), poor for CMIR (κ = –0.055), and fair to moderate for combined IR (κ = 0.395). High AMIR phenotype animals had significantly higher serum cortisol concentrations than their low immune responder counterparts (P = 0.045). A similar relationship was observed in heifers categorized for CMIR, with High CMIR responders having higher serum cortisol concentrations than their low responder counterparts (P = 0.008). High AMIR calves had a higher ADG compared with low AMIR calves (0.72 ± 0.02 versus 0.66 ± 0.06 kg/d; P = 0.009). Serum haptoglobin concentrations and worm egg counts were very low and could not be used to investigate associations with immune responsiveness. It is concluded that secondary and tertiary antibody responses to TT were well correlated in the Holstein-Friesian heifers in this study and that by using the testing procedure described here, low antibody responders were able to be consistently identified in the herd.

Gastrointestinal nematode (GIN) infections are a common cause of morbidity and mortality in grazing sheep. Among these GINs, one of the most pathogenic is Haemonchus contortus. Control of this parasite relies heavily on anthelmintics, but alternatives must be explored because H. contortus can rapidly develop anthelmintic resistance. Climate change will not only affect the sheep’s ability to fight GIN infection, but also influence the life cycle, parasite load, and pasture contamination of H. contortus. All of these factors highlight the importance of developing alternative tools, such as genetic selection for resistance to H. contortus infection, which can be used as part of a sustainable integrated parasite-management program. Abomasum tissues, the primary target tissue of H. contortus, were collected from previously phenotyped HIGH and MIDDLE stress responding sheep (n=29) and control sheep (n=8), to examine the abomasum transcriptomic profile associated with the parasite burden. Principle Component Analysis was performed using HIGH (n=14) and MIDDLE (n=15) stress responding sheep using R. The included components were: fecal egg count, cortisol level, CarLA saliva test, red blood cell count, hematocrit and abomasum worm count. Additionally, t-test analysis was performed to confirm significant differences between these two groups (HIGH and MIDDLE). Among these sheep, eight were selected to perform RNA-Sequencing analysis from; HIGH stress responders (n=4) and MIDDLE stress responders (n=4) with a significant difference between these groups of animals (p=0.086). RNA isolation was performed from these selected animals (n=8) in addition to control animals (n=4). Differential gene expression analysis between HIGH and MIDDLE stress responding sheep and identification of structural variants associated with the stress response will be performed using RNA-Sequencing. In addition, climate data will be collected over two grazing seasons, to examine a correlation between climate conditions and H. contortus pasture contamination and host load.

Breeding dairy cattle using diverse phenotypic markers has been suggested as a feasible approach to improve health and decrease the deleterious consequences of infectious diseases. Studies conducted in pigs have demonstrated the value of antibody (AMIR)- and cell (CMIR)-mediated immune responses as quantitative traits for improving immune responsiveness by selecting livestock using estimated breeding values (EBV) for immune response (IR) traits. Studies of cattle have tested the possibility of using IR traits as phenotypic markers to classify cows as high (HR), average (AR) and low (LR) responders. Information is scarce or unavailable about either genetic parameters of AMIR and CMIR or their phenotypic and genetic associations with production, conformation, fertility or health traits in lactating dairy cattle. The objectives of the current study were to evaluate phenotypic and genetic parameters of both AMIR and CMIR as quantitative immunological traits ( n = 6) in comparison with production, fertility and health traits in dairy cattle for their use in a selection index intended to improve bovine health. Results of this study showed significant AMIR and CMIR responses. Most phenotypic correlations between IR traits and production, health or fertility traits were not significant. The highest heritabilities ( h 2 ) were observed for delayed-type hypersensitivity (DTH) to killed Candida albicans whole cell (CaWC) at 48 h (0.54) and AMIR day 14 (0.42). The highest genetic correlations were observed between AMIR 14 and AMIR 21 (0.99) and between DTH to CaWC 24 h and DTH to CaWC 48 h (0.93). Two important and significant sire EBV correlations were noted between AMIR and fat % (0.18), and between CMIR and protein % (−0.15). In conclusion, this study demonstrated that both AMIR and CMIR are heritable traits in cattle and could be considered for their inclusion in a selection index intended to improve health.

The objectives of this study were to evaluate (1) natural antibodies (NAb) in Canadian Holstein cows, (2) genetic parameters and associations between NAb and specific antibody (SpAb), and (3) the association of NAb with clinical mastitis and differences in incidence rates of clinical mastitis (IRCM) among cows classified as high, average, or low responders for NAb. Natural antibodies (IgG and IgM) to keyhole limpet hemocyanin and SpAb to a type 2 test antigen were measured on 451 Holsteins from 41 herds across Canada. A series of uni- and tri-variate linear animal models were used to estimate genetic parameters and breeding values for NAb and SpAb. The models included the fixed effects of parity and stage of lactation and the random effects of herd-technician, animal, and residual. Using estimated breeding values for NAb, cows were classified as high, average, or low responders and phenotypic associations with the IRCM were investigated and a logistic regression performed. The estimated heritability was 0.27 for SpAb, and was 0.32 and 0.18 for NAb of the IgG and IgM isotypes, respectively. No significant genetic correlations were found between SpAb and NAb. Although no significant differences in the IRCM were found when cows were classified based on NAb IgG, cows classified as high responders for NAb IgM tended to have a lower IRCM compared with other cows. Immunoglobulin-M was associated with a decreased risk of clinical mastitis (odds ratio=0.958). Results of this study suggest the potential to use NAb IgM as an additional tool to select for disease resistance in cattle, but results need to be validated with a larger sample size.

The objective of this study was to compare the incidence rate of clinical mastitis (IRCM) between cows classified as high, average, or low for antibody-mediated immune responses (AMIR) and cell-mediated immune responses (CMIR). In collaboration with the Canadian Bovine Mastitis Research Network, 458 lactating Holsteins from 41 herds were immunized with a type 1 and a type 2 test antigen to stimulate adaptive immune responses. A delayed-type hypersensitivity test to the type 1 test antigen was used as an indicator of CMIR, and serum antibody of the IgG1 isotype to the type 2 test antigen was used for AMIR determination. By using estimated breeding values for these traits, cows were classified as high, average, or low responders. The IRCM was calculated as the number of cases of mastitis experienced over the total time at risk throughout the 2-year study period. High-AMIR cows had an IRCM of 17.1 cases per 100 cow-years, which was significantly lower than average and low responders, with 27.9 and 30.7 cases per 100 cow-years, respectively. Low-AMIR cows tended to have the most severe mastitis. No differences in the IRCM were noted when cows were classified based on CMIR, likely due to the extracellular nature of mastitis-causing pathogens. The results of this study demonstrate the desirability of breeding dairy cattle for enhanced immune responses to decrease the incidence and severity of mastitis in the Canadian dairy industry.

Lameness is a major animal welfare issue affecting Canadian dairy producers, and it can lead to production, reproduction, and health problems in dairy cattle herds. Although several different lesions affect dairy cattle hooves, studies show that digital dermatitis is the most common lesion identified in Canadian dairy herds. It has also been shown that dairy cattle classified as having high immune response (IR) have lower incidence of disease compared with those animals with average and low IR; therefore, it has been hypothesized that IR plays a role in preventing infectious hoof lesions. The objective of this study was to compare the prevalence of digital dermatitis in Canadian dairy cattle that were classified for antibody-mediated (AMIR) and cell-mediated (CMIR) immune response. Cattle (n = 329) from 5 commercial dairy farms in Ontario were evaluated for IR using a patented test protocol that captures both AMIR and CMIR. Individuals were classified as high, average, or low responders based on standardized residuals for AMIR and CMIR. Residuals were calculated using a general linear model that included the effects of herd, parity, stage of lactation, and stage of pregnancy. Hoof health data were collected from 2011 to 2013 by the farm's hoof trimmer using Hoof Supervisor software (KS Dairy Consulting Inc., Dresser, WI). All trim events were included for each animal, and lesions were assessed as a binary trait at each trim event. Hoof health data were analyzed using a mixed model that included the effects of herd, stage of lactation (at trim date), parity (at trim date), IR category (high, average, and low), and the random effect of animal. All data were presented as prevalence within IR category. Results showed that cows with high AMIR had significantly lower prevalence of digital dermatitis than cattle with average and low AMIR. No significant difference in prevalence of digital dermatitis was observed between high, average, and low CMIR cows. These results indicate that having more robust AMIR is associated with lower prevalence of digital dermatitis hoof lesions.

The objectives of this study were to investigate the sources of variation in milk fat globule (MFG) size in bovine milk and its prediction using mid-infrared (MIR) spectroscopy. Mean MFG size was measured in 2,076 milk samples from 399 Ayrshire, Brown Swiss, Holstein, and Jersey cows, and expressed as volume moment mean (D[4,3]) and surface moment mean (D[3,2]). The mid-infrared spectra of the samples and milk performance data were also recorded during routine milk recording and testing. The effects of breed, herd nested within breed, days in milk, season, milking period, age at calving, parity, and individual animal on the variation observed in MFG size were investigated. Breed, herd nested within breed, days in milk, season, and milking period significantly affected mean MFG size. Milk fat globule size was the largest at the beginning of lactation and subsequently decreased. Milk samples with the smallest MFG on average came from Holstein cows, and those with the largest were from Jersey and Brown Swiss cows. Partial least squares regression was used to predict MFG size from MIR spectra of samples with a calibration data set containing 2,034 and 2,032 samples for D[4,3] and D[3,2], respectively. Coefficients of determination of cross validation for D[4,3] and D[3,2] prediction models were 0.51 and 0.54, respectively. The associated ratio of performance deviation values were 1.43 and 1.48 for D[4,3] and D[3,2], respectively. With these models, individual mean MFG size could not be accurately predicted, but results may be sufficient to screen samples for having either small or large MFG on average. Significant but low correlations of D[4,3] and D[3,2] with milk fat yield were estimated (0.16 and 0.21, respectively). Significant and moderate Pearson correlation coefficients for fat percent with D[4,3] and D[3,2] were assessed (0.34 and 0.36, respectively). This correlation was greater between milk fat percentage and predicted MFG size than with measured MFG size with coefficients of 0.47 and 0.49 for D[4,3] and D[3,2], respectively. The MIR prediction equations are potentially overusing the correlation between fat and MFG size and exploiting the strong relationship between the MIR spectra and total milk fat. However, the predictions of MFG size are able to determine variation in mean globule size beyond what would be achieved just by looking at the correlation with fat production.

The objectives of this study were to evaluate antibody (AMIR) and cell-mediated immune responses (CMIR), survival, and somatic cell score (SCS) between purebred Holstein (HO) and crossbred Norwegian Red × Holstein (NRHO) first-calf heifers postpartum. Additionally, immune response traits observed as calves in a previous study were correlated with their immune response traits as first-calf heifers. Heifers, previously immunized as calves, were bled and reimmunized 6 to 9 d postcalving with known type 1 and type 2 antigens and human serum albumin (HSA). Seven days later, heifers were rebled, and background skinfold measurements of the tail fold were taken. Intradermal injections of PBS and type 1 antigen were administered on either side of the tail fold. On d 9 final skinfold measurements were taken and used to assess delayed-type hypersensitivity (DTH) as an indicator of CMIR. Blood samples were also collected for a final time on d 14 from heifers that received the antigen HSA. Serum was obtained from blood collected on d 0, 7, and 14 and analyzed by ELISA to assess AMIR. Data on survival and somatic cell count, which was converted to SCS, were obtained from CanWest Dairy Herd Improvement (DHI). All SCS, survival, and immune response data were analyzed using general linear models to determine significance between HO and NRHO first-calf heifers. To determine residual correlations between immune response traits observed in calves to their responses as first-calf heifers, residuals were obtained from models, and correlations between traits were determined using PROC CORR in SAS. Results showed NRHO had a greater primary IgG antibody response to HSA and greater tertiary IgG antibody response to the type 2 antigen compared with HO. Crossbreds (NRHO)also had significantly greater DTH response (P < 0.05) and, in general, greater survival from calving to 100 d in milk (dim), 100 to 305 dim, calving to 305 dim, and age at immune response testing as calf to 305 dim. No difference was observed between breeds for SCS. Results also showed most correlations between calf and first-calf heifer immune response traits were found to be positive and significant (P < 0.05). In conclusion, NRHO heifers have greater survival, which likely relates at least in part to increases in aspects of both AMIR and CMIR and could indicate that crossbred heifers have enhanced disease resistance.

The objective of this study was to use previously calculated estimated breeding values for cell- (CMIR) and antibody-mediated immune responses (AMIR) to determine associations between immune response (IR) and economically important diseases of dairy cattle. In total, 699 Holsteins were classified as high, average, or low for CMIR, AMIR, and overall IR (combined CMIR and AMIR), and associations with mastitis, metritis, ketosis, displaced abomasums, and retained fetal membranes were determined. The incidence of mastitis was higher among average cows as compared with cows classified as high AMIR [odds ratio (OR)=2.5], high CMIR (OR=1.8), or high IR (OR=1.8). Low-CMIR cows had a higher incidence of metritis (OR=11.3) and low-IR cows had a higher incidence of displaced abomasum (OR=4.1) and retained fetal membrane (OR=2.8) than did average responders. Results of this study show that cows classified as high immune responders have lower occurrence of disease, suggesting that breeding cattle for enhanced IR may be a feasible approach to decrease the incidence of infectious and metabolic diseases in the dairy industry.

Selection for production traits with little or no emphasis on health traits has led to an increase in the incidence of disease in Canadian dairy herds. We describe here a patented protocol for estimating the breeding value for immune responsiveness in heifers that combines measures of both cell-mediated (CM) and antibody-mediated (AM) immune responses (IR). The ability of putative type 1 and type 2 antigens used to induce CMIR and AMIR, respectively, was assessed in replacement Holstein heifers, and the effects of age and pregnancy on type 1 and type 2 IR bias were estimated. Results demonstrated that the type 1 and type 2 antigens induced polarized type 1 and type 2 responses in heifers regardless of age and pregnancy status, and can therefore be used to identify animals with superior overall immune responsiveness. However, age and pregnancy status had significant effects on adaptive IR profiles, highlighting the need for appropriate statistical modeling of such effects when ranking animals on their ability to mount CM and AMIR. Responses became increasingly type 1 biased as heifers approached 12 mo of age, from which point, responses then became increasingly type 2 biased with age and length of gestation. Knowledge of how age and pregnancy influence the dynamics of type 1 and type 2 IR bias is expected to improve our ability to select animals with enhanced immune responsiveness and aid in the development of effective vaccines through strategic targeting of vaccine components to recipients.

There is a growing interest in how environmental heat stress affects economically important traits in cattle, such as production, health, and fertility. For example, under heat stress, dairy cattle consume less feed, produce less milk, and fertility decreases, all of which result in economic loss. Furthermore, there is a negative correlation between milk production and heat tolerance; thus, selection for high milk production results in less heat tolerant animals. Compared to dairy cattle, less is known about the effect of heat stress on beef cattle. In contrast to dairy cattle, beef cattle spend most the year outside and thus must withstand environmental conditions regularly. To begin our investigation into the effect of heat stress on fertility, we are studying the effect of environmental conditions specifically on beef bull fertility. We examined the relationship between the average temperature-humidity index (THI) and average maximum ambient temperature during the week leading up to motility measurements from 170 bulls (Angus x Simmental crossbreed). Preliminary results show a positive correlation between the average THI and motility (r=0.16, p=0.045). Likewise, there is a positive correlation between the average maximum ambient temperature and motility (r=0.16, p=0.038). Our preliminary results suggest that THI and maximum ambient temperature affect variability in sperm motility measurements. To further investigate factors contributing to the variability in the beef motility data, we are currently conducting a genome-wide association study (GWAS) to identify genetic markers associated with motility using a population of 350 beef bulls. Our GWAS could reveal genetic variation that is associated with overall better motility, as well as better motility during periods of heat stress and therefore better fertility in beef bulls for the future.

Persistence of bovine Staphylococcus aureus mastitis may be associated with the small colony variant (SCV) form that is adapted to intracellular life and resists elimination by the immune system. This study evaluated antibody-mediated (AMIR) and cell-mediated immune responses (CMIR) to two bovine SCV forms and their parent strains isolated from cows with mastitis. Four groups of healthy cows, five cows/treatment group, were challenged by the intramammary route with naturally occurring bovine SCV Heba3231, its parent strain 3231, a hemB mutant displaying the SCV phenotype or its parent strain, Newbould 305. Blood and milk samples were collected at day 0 before challenge and at days 1, 14, 21 and 36 post-challenge to determine antigen-specific immunoglobulin (Ig) IgG(1) and IgG(2) antibody responses as indicators of type 2 and type 1 responses, respectively. At day 24 post-challenge cows in each group were inoculated with the UV-killed homologous strain intradermally in the neck to induce delayed-type hypersensitivity (DTH) as an indicator of CMIR. The SCV Heba3231 and 3231 strains induced significant IgG(1) and IgG(2) antibody responses in sera and in sera and milk whey, respectively. The hemB SCV mutant and Newbould 305 strains induced significant IgG(1) antibody in milk whey, and in sera and milk whey, respectively. The SCV Heba3231 and 3231 strains induced DTH, the hemB mutant induced intermediate hypersensitivity, and Newbould 305 failed to induce DTH. These results indicate marked differences in immune responses induced by parent and SCV forms of the same strain of S. aureus and by the two wild-type strains. This is the first study to evaluate both AMIR and CMIR in the context of persistent bovine mastitis to different and genetically characterized strains of S. aureus including two SCVs. The findings expand our understanding of immune responses to persistent S. aureus mastitis.

Persistent bovine Staphylococcus aureus mastitis is attributable to the versatility of this pathogen within the mammary gland environment and to the formation of small colony variants (SCVs) that can survive within host cells. Previous studies had shown that S. aureus SCV Heba3231, isolated from a cow with chronic mastitis, had invaded and persisted in primary bovine aortic endothelial cells but caused minimal deleterious effects. The objective of this study was to investigate the interaction of SCV Heba3231 with bovine mammary epithelial cells (MAC-T cells) compared to its parent strain 3231 and to prototype strain Newbould 305. Monolayer cells were infected with each strain at various multiplicity of infections (MOIs) for 1 and 3.5h, followed by 20 min incubation with lysostaphin. Recovery of the SCV was significantly higher (P