Bonnie A Mallard

University of Guelph | UOGuelph · Department of Pathobiology

Dairy cattle face a variety of stressful events on a daily basis. More specifically, climate change has resulted in more frequent heat stress events that increase the incidence of chronic bacterial infections by inducing conditions like leaky gut syndrome, whereby the integrity of the intestinal epithelium is compromised allowing for luminal bacter...

In cattle, maternal immunoglobulins are transferred through colostrum to provide passive immunity to the neonatal calf once they are absorbed into circulation. Cows can be assessed for antibody- and cell-mediated immune responses (AMIR and CMIR, respectively), and through estimated breeding values (EBV) and genomic parent averages (GPA), cows can b...

Gastrointestinal nematode (GIN) infections are considered the most important disease of grazing sheep and due to increasing anthelmintic resistance, chemical control alone is inadequate. Resistance to Gastrointestinal nematode infection is a heritable trait, and through natural selection many sheep breeds have higher resistance. Studying the transc...

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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,...

Dairy cattle routinely face a variety of stressors. For example, climate change has resulted in more frequent heat stress events that increase the incidence of bacterial infections by inducing conditions like leaky gut syndrome, whereby the integrity of the intestinal epithelium is compromised allowing for luminal bacteria and their membrane compon...

The frequency of heat waves and hot days are increasing due to climate change, which leads to an increase in the occurrence of heat stress in dairy cattle. Previous studies have shown that dairy cattle identified as high immune responders have a reduced incidence of disease and improved vaccine response compared to average and low responders. Addit...

The climate in northern latitude countries, such as Canada, are changing twice as fast as in lower latitude countries. This has resulted in an increased frequency of hot days and longer more frequent heat waves. Canadian dairy cattle are therefore at increased risk of heat stress, especially those in management systems without the infrastructure to...

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 wa...

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 percent of colostral Ig. Natural antibody IgM is less abundant but provides broad and non-specific reactivity, potentially contributing to...

The frequency of heat waves are increasing due to climate change, which leads to an increase in the occurrence of heat stress in dairy cattle. Previous studies have shown that dairy cattle identified as high immune responders have a reduced incidence of disease and improved vaccine response compared to average and low responders. Additionally, it h...

Vaccines have been developed at “warp speed” to combat the COVID-19 pandemic caused by the SARS-CoV-2 coronavirus. Although they are considered the best approach for preventing mortality, when assessing the safety of these vaccines, pregnant women have not been included in clinical trials. Thus, vaccine safety for this demographic, as well as for t...

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...

Background 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 susceptibil...

Background In mammalian species, hypoxia is a prominent feature of inflammation. The role of hypoxia in regulating macrophage responses via alteration in metabolic pathways is well established. Recently, oxidative burst-induced hypoxia has been shown in murine macrophages after phagocytosis. Despite the available detailed information on the regulat...

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 pattern...

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 dise...

From the beginning, cattle have made important contributions to the field of immunology, including the development of the first Mycobacterium bovis BCG vaccine for human tuberculosis in 1921. In 1981 the first report of a biosynthesized polypeptide vaccine against Foot and Mouth Disease Virus (FMDV) using the VP3 protein expressed in Escherichia co...

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) respon...

Host–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’ role in the course of inflammation is still very limited in small ruminants. The pres...

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 uniqu...

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...

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...

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 i...

Disease resistance has a complex phenotype because of the dynamic interaction between host, pathogen, and environment. Discovering the mechanisms of how the genome shapes this phenotype is an exceptionally complex process with more than 5000 genes controlling host defense. Various strategies that have been used by researchers are limited. Although...

The dynamic interaction between the host and pathogens, along with environmental factors, influences the regulation of mammalian immune responses. Therefore, comprehensive in vivo immune-phenotyping during an active response to a pathogen can be complex and prone to confounding effects. Evaluating critical fundamental aspects of the immune system a...

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 s...

Control of animal health in the beef industry has long relied on management, medication, and vaccination. Immune response (IR) traits have not yet been incorporated into breeding programs for beef cattle. Inclusion of such traits has been suggested to improve overall animal health and enhance disease resistance. The High Immune Response (HIRTM) tec...

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 respons...

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 les...

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...

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 ex...

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...

Abstract 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 cau...

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 betwee...

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...

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 f...

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...

Genetc selecton can play a key role in reducing disease incidence in catle. Since 2013, semen from sires tested and identfied to have superior immune response genetcs has been available to commercial dairy producers. Health records collected in herd software from large commercial dairy farms in North America were interrogated to determine the impac...

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 predict...

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 Hol...

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...

Common health problems observed during peripartum include milk fever, mastitis, fatty liver disease, ketosis, dystocia, retained placenta, metritis, hypomagnesaemia and abomasal displacements. The increased incidence of health problems observed during the periparturient period can be partly attributed to suboptimal immune responses. Factors contrib...

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 qua...

The objective of this study was to evaluate IgG and β-lactoglobulin (β-LG) concentrations in colostrum and milk of Canadian Holsteins (n = 108) classified as high (H), average (A), or low (L) for antibody-mediated (AMIR) or cell-mediated immune responses (CMIR) based on estimated breeding values. It was hypothesized that H-AMIR and H-CMIR cows prod...

The objective of this study was to assess the immune and stress responsiveness of cows identified as extremely high and low feed conversion efficiency phenotypes. The study utilised 16 Holstein-Friesian cows in their third to fourth lactation, and identified as having either extremely high (n = 8) or extremely low (n = 8) feed conversion efficiency...

Genetic selection for enhanced immune response has been shown to decrease disease occurrence in dairy cattle. Cows can be classified as high (H), average, or low responders based on antibody-mediated immune response (AMIR), predominated by type-2 cytokine production, and cell-mediated immune response (CMIR) through estimated breeding values for the...

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...

Background Technical feasibility of RNA quantification by real time RT-PCR has led to enormous utilization of this method. However, real time PCR results need to be normalized due to the high sensitivity of the method and also to eliminate technical variation. Normalization against a reference gene that is constitutively transcribed and has minimum...

The immune system is a sensing structure composed of tissues and molecules that are well integrated with the neuroendocrine system. This integrate system ensures non-self from self-discrimination. In this capacity the immune system provides detection and protection from a wide range of pathogens. In mammals, the immune system is regulated by severa...

Mastitis is one of the most prevalent and costly diseases in the dairy industry with losses attributable to reduced milk production, discarded milk, early culling, veterinary services, and labor costs. Typically, mastitis is an inflammation of the mammary gland most often, but not limited to, bacterial infection, and is characterized by the movemen...

Lactic acid bacteria (LAB) are of interest because of their potential to modulate immune responses. The effects of LAB range from regulation to stimulation of the immune system. A series of studies were performed in vitro to study the effects of six lactic acid bacteria (LAB), Lactobacillus helveticus LH-2, Lactobacillus acidophilus La-5, La-115, L...

Abstract Text: Toll-like receptor 2 (TLR2) is a pattern recognition receptor expressed on the surface of epithelial cells and some leukocytes. Binding of bacterial ligands such as lipoproteins and lipopeptides to TLR2 induces proinflammatory innate responses and contributes to the development of adaptive immune responses. In the present study we...

Abstract Text: The objective of this study was to investigate phenotypic profiles of lactoferrin (LF) and total immunoglobulin G (IgG) in colostrum from Canadian Holsteins (n=87) previously classified as having High, Average or Low immune responses. A general linear model was used to account for parity, barn and first milking volume. Preliminary re...

Abstract Text: Over the past two decade epigenetics has influenced the investigation of disease susceptibility. DNA methylation has been extensively studied in CD4+ T-cell immune responses (IR) and it has been shown that specific DNA methylation sites within cytokine promoters influence cytokine production. The objective of this study was to determ...

Abstract Text: A total of 1,046 milk samples from 188 Canadian Holstein cows were analyzed for mean milk fat globule size and casein micelle size. Milk fat globule size was calculated as both as volume moment mean and surface moment mean. High heritabilities were found for both expressions of the trait at 0.57 and 0.50, respectively. Additionally,...

Abstract Text: Selection for enhanced immune responsiveness using the High Immune Response Technology is a genetic approach to improve animal health. Previous genomic research has shown promise for the inclusion of immune response in genomic breeding objectives; however the research was based on a small number of cows or bulls that were selective...