Browsing by Author "Pajor, Edmond"

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    Assessment and Impacts of Newborn Beef Calf Vigour
    (2016) Homerosky, Elizabeth Rose; Kastelic, John; Windeyer, Claire; Timsit, Edouard; Pajor, Edmond
    Modified APGAR scores, intended to identify compromised calves with reduced vigour, yield inconsistent results and are not widely adopted. Data were collected from 77 newborn beef calves to determine calving characteristics and clinical examination parameters associated with abnormal blood parameters and a calf’s ability to consume colostrum by 4 h after birth. Calves born to primiparous dams, with increased calving difficulty, a weak suckle reflex, or incomplete tongue withdrawal, had decreased blood pH and increased L-lactate at 10 min after birth (P<0.05). Calves with a weak suckle reflex were 41.6 times more likely to fail to consume colostrum by 4 h compared to calves with a strong suckle reflex (P<0.0001). Calves that failed to consume colostrum by 4 h were 2.8 times more likely to be treated prior to weaning (P=0.03). In conclusion, good newborn beef calf vigour is a vital survival characteristic that helps ensure timely colostrum consumption, contributing to long-term health.
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    Consequences of Testicular Heat Stress and Potential Amelioration Strategies
    (2023-01-12) Mohamed, Abdallah Mohamed Shahat; Kastelic, John; Kovalchuk, Igor; Pajor, Edmond; Pearson, Jennifer; Thundathil, Jacob; de Graaf, Simon; Honaramooz, Ali
    Heat stress (HS) is a worldwide problem due to temperature elevations associated with global warming. Monitoring temperature changes in testes and scrotum over time is important to understand thermoregulatory capacity of testes and scrotum. Temperature data loggers (DLs) are reliable devices that can be implanted in scrotal subcutaneous tissues to serially record intrascrotal temperature without altering animal behavior. Testicular HS causes a variety of outcomes, depending on the degree and duration of testicular heating. Some effects of testicular HS on testicular tissues, blood flow and sperm quality and attempts to prevent them, by treating animals or semen extender, have been reported. The overall objective of this study was to investigate impacts of HS on sperm quality and use various ameliorative strategies to mitigate these detrimental effects, using bull and ram models. We validated data loggers as a reliable, less invasive and serial method to measure intrascrotal temperature. Scrotal subcutaneous temperature was significantly increased by scrotal insulation or whole-body heating, but not by scrotal neck insulation; however, all three heat-stress models decreased sperm motility and morphology in bulls and rams. In addition, our hypothesis that melatonin or L-arginine improve quality of frozen-thawed sperm from HS rams was supported; 1 mM of either gave best results, except 0.5 mM minimized DNA Fragmentation Index (DFI%). Moreover, during hot weather, bulls voluntarily accessed shade, significantly lowering scrotal subcutaneous temperatures and improving sperm quality. In rams exposed to testicular HS, slow-release melatonin significantly improved testicular blood flow, protected sperm motility and morphology, and lessened HS-induced reductions in post-thaw sperm quality. Therefore, melatonin has potential for mitigating effects of testicular HS under field conditions.
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    Detection, Prevention and Control of Lameness and Foot Lesions in Canadian Dairy Herds
    (2016) Solano Quesada, Laura; Orsel, Karsina; Barkema, Herman; Pajor, Edmond; Mason, Steve; LeBlanc, Stephen
    Lameness is a multifactorial condition and a clinical sign of painful disorders related to the locomotor system. Furthermore, it is a severe welfare issue and production-limiting disorder, ranking third as the most significant health problem in dairy cattle. Approximately 90% of lameness is caused by foot lesions. Understanding the multifactorial nature and interconnected risk factors of lameness and foot lesions is essential for disease prevention and control. This thesis comprises two parts that explore the epidemiology of lameness and foot lesions across Canada. In Part 1, research focused on estimating prevalence and identifying risk factors for lameness and foot lesions, in addition to evaluating automated measures of lying behavior as a diagnostic tool for lameness. Lameness affected 21% of cows; prevalence was higher on farms with poor comfort of surfaces for standing and lying. Lying behavior was not a sensitive diagnostic tool for lame cows, as it was subject to wide variability due to intrinsic cow factors. The most prevalent foot lesion was digital dermatitis (DD), affecting 15% of cows and 94% of herds in Alberta. Digital dermatitis is an infectious foot lesion that causes painful skin erosions, and has large economic and welfare implications. The use of footbaths is the most common herd-level approach to control spread of DD. Suboptimal footbath management was an important reason for the high DD prevalence in Alberta. Therefore, in Part 2, an intervention study was conducted to evaluate effectiveness of a standardized footbath protocol in decreasing DD prevalence. The protocol was based on current scientific literature, including footbath design and management. Additionally, a method for simple and reliable detection of DD lesions was validated and proven highly sensitive (92%) and specific (88%). The footbath intervention was effective in achieving and maintaining a lower prevalence of cows with active DD lesions and a higher prevalence of cows without DD. In addition, cows with poor leg cleanliness more often had DD. Ultimately, adopting management practices intended to improve cows’ comfort and hygiene of surfaces for lying and standing, along with improvements in footbath design and protocol, could decrease prevalence of foot lesions and lameness.
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    High intensity, short duration pulling in heavy horses: physiological effects of competition and rapid weight change
    (2017-11-07) Greco-Otto, Persephone; Massie, Shannon; Shields, Erin; Roy, Marie-France; Pajor, Edmond; Léguillette, Renaud
    Abstract Background The Heavy Horse Pull is a competition where teams of two horses pull an increasingly heavy sled for a short distance. Similar to human wrestlers, some horses may undergo rapid weight change in order to enter a lower weight category. The objectives were to study the physiological effects of this practice as well as of the pulling competition in draft horses. Results Fifty horses were divided into light-, middle- and heavyweight categories based on their arrival weights and competed 1–3 days after. Body weight was measured upon arrival and pre-competition. Blood was sampled for chemistry and high sensitivity cardiac troponin T (hscTnT) at arrival, pre- and post-competition in 34, 26 and 20 horses, respectively. Body weight increased significantly between arrival and pre-competition for light (7.2% (Median: 62.8Kg (41.7–77.0)) and middle (8.6% (Median: 80.5Kg (62.7–90.9)) weight categories. Change in body weight was correlated (r = 0.69, p = 0.002) with competition ranking for middleweights. The ratios of weight pulled to team body weight were 2.7 (1.9–2.8), 2.6 (2.5–2.6) and 2.4 (2.2–2.5) for the lightweights, middleweights and heavyweights, respectively. Blood chemistry indicated hemoconcentration on arrival in the middleweight and lightweight horses. Hemoconcentration was not seen on arrival in some horses with marked rapid weight change. Overall, no chemistry parameter changed between pre- and post-competition. The hscTnT stayed within normal range post-competition. Conclusions While horses arrived to the event with indications of hemoconcentration, they appeared to have sufficient time to rehydrate prior to competition, and the effects of the competition were reversible within 3 h.
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    Impact of Age and Duration of Maternal Separation on Processing Stress and Vaccine Responses in Pre-weaned Beef Calves
    (2022-06) Silas, Haley; Pajor, Edmond; Windeyer, Claire; Galezowski, Angelica; Janzen, Eugene
    Spring processing is a common practice in western Canadian cow-calf herds that involves separating calves from their dams and restraining the calves while they receive a combination of procedures that may include vaccination, castration, branding, and dehorning. Spring processing events are thought to be stressful for the calf; however, the impact of their age and the duration of maternal separation is not known. The first study (Chapter 2) assessed impacts of age and duration of maternal separation on stress experienced by calves at processing. It was found that four- and eight-week old calves had similar behavioural indicators of stress and cortisol concentrations after processing. Calves separated for five hours before processing were less active after processing than calves separated for one hour before processing. This decrease in activity in calves separated for longer could indicate they have become exhausted or acclimatized to their pen. The second study (Chapter 3) assessed the impact of age and stress on immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody responses to intranasal vaccination with a modified live vaccine against bovine herpesvirus type 1 (BHV1), parainfluenza virus type 3 (PIV3), and bovine respiratory syncytial virus (BRSV; Inforce3®, Zoetis Inc., New Jersey, USA). In this study, BRSV, PIV3, and BHV1 IgG concentrations remained relatively similar from baseline to post-vaccination, while BRSV, PIV3, and BHV1 IgM concentrations increased during the same period. Furthermore, this increase was greater in eight-week old calves than four-week old calves, potentially because old calves were more responsive immunologically than the younger calves. Cortisol concentration proved to have minimal association with antibody concentrations after vaccination, with only some weak positive correlations between cortisol at certain timepoints and BRSV IgG or BHV1 IgG concentrations post-vaccination. Overall, there was no difference between vaccinated and unvaccinated calves, suggesting that maternally derived antibodies may have prevented a detectable humoral immune response to vaccination. To our knowledge, this study was the first to consider IgG and IgM immune responses to vaccination at industry-relevant processing ages.
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    Optimizing passive immunity in beef calves: An evaluation of colostrum management strategies and the impact of total and specific immunoglobulin G on health and growth
    (2021-09-20) Gamsjäger, Lisa; Windeyer, Claire; Pajor, Edmond; Lévy, Michel; Yates, Robin
    Inadequate transfer of immunoglobulins from dam to calf via colostrum continues to present a challenge on cow-calf operations. Therefore, the aim of this thesis was to investigate management strategies to optimize the transfer of passive immunity (TPI) in beef calves and to identify risk factors associated with and impacts of total and specific immunoglobulin G (IgG) concentrations. Chapter 2 demonstrated that Brix refractometry is a practical, accurate tool for on-farm assessment of IgG concentrations in beef cow colostrum and that thresholds of <24 and ≥30% Brix indicate low- and high-IgG colostrum, respectively. In Chapter 3, calves fed a moderate volume and IgG concentration (1.4L, 70g/L IgG) of colostrum product nursed their dams significantly sooner than calves fed a small (1L) or large volume (2L) with a high IgG concentration (100 g/L), as did calves fed by nipple bottle compared to those fed by oro-esophageal tube feeder. Calf serum IgG concentrations were similar among all interventions studied. Chapter 4 evaluated optical and digital serum total protein (STP) refractometers, and the Brix refractometer for on-farm assessment of serum IgG concentration in beef calves. All three refractometers demonstrated excellent test characteristics, and STP concentrations of ≤5.8 g/dL and Brix percentages of ≤8.7 % can be used to detect inadequate TPI (i.e., <24 g/L IgG). Lastly, in Chapter 5, colostrum intervention was the most consistent predictor of poor TPI, and dam parity was the most consistent predictor of pathogen-specific IgG concentrations. We identified poor producer compliance with vaccine label instructions and variable impacts of pre-calving vaccination on specific calf serum IgG concentrations. Calves with poor TPI were more likely to get treated and die and showed lower weight gains in the pre-weaning period, while higher bovine rotavirus-specific IgG concentrations were associated with lower pre-weaning mortality. Our findings suggest room for improvement regarding on-farm vaccination strategies, particularly in heifers, and the need for further improvement of colostrum management in beef calves. Overall, this thesis identified important risk factors associated with poor TPI, highlighted the negative effects it had on pre-weaning health and growth, and offers a first step towards the development of practical, beef calf-specific colostrum management guidelines.