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ADVICE AND INSIGHTS FROM UBC FACULTY ON REACHING OUT TO SUPERVISORS
These videos contain some general advice from faculty across UBC on finding and reaching out to a potential thesis supervisor.
Graduate Student Supervision
Doctoral Student Supervision
Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.
Dairy cow behaviour and estrous expression: effects of disease and management (2021)
Management of modern dairy farms spend a considerable amount of time ensuring that every cow produces a calf every year, that all cows stay healthy. Despite these laudable goals, fertility and disease continue to be two of the major challenges facing the dairy industry. In this thesis I address both of these areas in an attempt to improve the health and welfare of dairy cattle and to aid farmers in the early identification of sick cows and identifying ways of improving fertility on their farms. My first aim was to assess changes in rumination and feeding behaviour associated with diseases common after calving (Chapter 2). The results indicate that monitoring rumination and feeding behaviour during the time around calving is helpful in the detection of cows with metabolic problems. The second aim focused on understanding how stocking density affects estrous expression and biomarkers of stress (Chapter 3). The results from Chapter 3 showed only mild effects of short-term exposure of lactating dairy cows to housing conditions where there is insufficient lying space for all cows to lie down at the same time, suggesting that many dairy cows are relatively resilient to short-term sub-optimal housing conditions. Lastly, I examined how standing and lying time, in general and around estrus, are affected by stocking density (Chapter 4). This chapter showed that even a short-term increase in stocking density to 133% (cow to stall ratio of 4:3) can have detrimental effects on the standing behaviour of healthy lactating dairy cattle and that individual standing times can be an indicator for the onset of estrus, particularly in understocked cows. In summary, this body of work shows how an improved understanding of behaviour can identify cows at risk for disease, that the choices made by farmers regarding how much lying space cows are given can affect standing and lying behaviour, and that changes in standing behaviour can be used detect estrus in dairy cows.
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Precision dairy technology and its association with estrous expression and fertility outcomes in Holstein cattle (2021)
Technologies developed to detect estrus have the potential to improve dairy cattle fertility; however, there is still need for better understanding of how the readers of automated activity monitors (AAM) are associated with fertility outcomes and reproductive physiology. The objectives of this thesis were to determine 1) if estrous expression, detected by AAM can be used within an ovulation synchronization program for timed artificial insemination (AI) and embryo transfer (ET), and 2) the relationship between estrous expression, ovulation rates, viability and quality of embryo, progesterone and estradiol concentrations, and fertility and pregnancy loss. In Chapter 2, it was demonstrated that following the use of a timed AI synchronization protocol, cows showed different intensities of estrus detected by an AAM and that greater intensity of estrous expression resulted in greater fertility and decreased pregnancy losses. In Chapter 3, I investigated the intensity of estrous expression at the end of a superovulation protocol, for embryo collection, in Holstein heifers and its association with production and viability of embryo. Heifers with greater intensity of estrus, detected by an AAM or a breeding indicator, had greater percentage and number of viable embryos compared with animals that had lower intensity of estrus. In Chapter 4, I examined the association between estrous expression and the success of ET, and found that the intensity of estrous expression, and the occurrence of estrus prior to ET, improved fertility. Finally, in Chapter 5, I summarized work that investigated if the concentrations of progesterone (P4) around estrus is related to the intensity of estrus and fertility of Holstein cows. Greater concentrations of P4 and lower concentrations of E2 at AI were associated with lower intensity estrous, while greater concentrations of P4 prior to AI were associated with greater estrous expression and fertility. Future research is needed to further understand the association of intensity estrous expression and fertility and pregnancy loss.
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Use of estrous expression within reproductive management and its association with conception and ovulation rates in dairy cows (2020)
Automated technologies have been developed to improve dairy cattle reproductive efficiency, yet there is still need for better understanding of how these technologies can be used and determine how the information collected relates to key events important for fertility. The aims of this thesis were to determine 1) if automated activity monitors (AAM) can predict estrus and be used within reproductive management, and 2) the interrelationship between estrous expression, ovulation and fertility. In Chapter 2, I provide evidence that AAM can be successfully incorporated into reproductive management without impeding the outcomes of an AI protocol and that increased estrous expression is associated with improved fertility. Chapter 3 investigates if changes in rumen-reticular temperature can be used to detect ovulation. Rumen-reticular temperature is shown to increase at the time of estrus and then declines near the time of ovulation, but the magnitude increase at estrus is dependent on the intensity of estrous expression as well as temperature and humidity at the onset of estrus. In Chapter 4 I demonstrate that the intensity of estrous expression is associated with the timing and failure of ovulation, where cows with lesser estrous expression had shorter intervals from estrus alert to ovulation and lower ovulation rates. Finally, in Chapter 5 I summarize work that investigated if the administration of GnRH at the moment of AI could increase fertility of cows with reduced estrous expression by increasing ovulation rates and modifying progesterone concentrations post-AI. The administration of GnRH increased fertility of cows with lesser estrous expression, but did not affect ovulation or progesterone profiles. Future research is merited to further understand the relationship between estrous expression and fertility of dairy cows.
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Characteristics of estrous behaviour in heifers and lactating cows and its associations with fertility (2017)
Detection of estrus in dairy cows is challenging, partly because of poor behavioural expression. Automated activity monitors allow quantification of estrus expression based on restlessness. The main goals of this thesis were to use automated measurements and visual observation of behaviour to increase understanding of estrus characteristics, variation among animals, risk factors for poor expression, and its association with fertility. In the first study, the behaviour of heifers was video-recorded and activity peaks were identified from accelerometer data; estrus was validated by ovarian ultrasonography. Chin rest, sniff, back mount, crossover, and follow had the largest increase in frequency during estrus. Estrus relative increase in walking activity (290 ± 160%) and duration (14 ± 4 h) varied greatly and were affected by estrus order, season and time of the day. The second study investigated how estrus affected automated measurements of lying and standing behaviour, a less explored aspect of estrus. At estrus, bout frequency was lower, daily standing time was greater, and heifers stood uninterruptedly for twice longer than at baseline. Relative changes in standing behaviour at estrus were smaller for estrus starting between 1200 h and 0300 h. The third experiment investigated the agreement between estrus characteristics in heifers fitted with two accelerometers. Both systems were precise (PPV = 84.7% and 98.7% ) and provided similar characterization and timing. Plasma estradiol was not correlated with follicle diameter, duration, intensity, or presence of estrus signs. Finally, estrus lying behaviour of lactating cows and its associations with fertility were studied. Daily lying time and bout frequency were reduced at estrus (65 ± 21% and 65 ± 24% of baseline). Ovulation and pregnancy at d 32 after AI were 4.9 and 1.6 times more likely if estrus lying time was 75% of baseline. Collectively, results suggest potential application of lying behaviour towards fertility prediction. We have also highlighted features such as variability, risk factors and basal activity that can contribute to assessment of methods and practices for increased expression. Additional future directions include investigation of physiological bases of estrus-fertility association and real-time applications of characterization data.
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Master's Student Supervision
Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.
Luteinizing hormone profile following exogenous GnRH at the time of artificial insemination in spontaneous estrous events of lactating Holstein cows (2024)
The administration of gonadotropin-releasing hormone (GnRH) at the time of artificial insemination (AI) has been associated with improvements in the fertility of lactating dairy cows with low estrous expression. However, the mechanism underlying this association remains unclear. This thesis aimed to evaluate the effect of GnRH at the supposed time of AI and intensity of estrous expression, measured by automated activity monitors (AAM), on the release of luteinizing hormone (LH) following GnRH administration in lactating Holstein cows. The secondary objectives were to explore additional associations of GnRH administration considering concentrations of progesterone (P4) and the uterine response to produce prostaglandin metabolite (PGFM) after an estradiol-oxytocin challenge. In Chapter 1, the scientific literature was reviewed to provide information on the importance of elucidating the effect of GnRH administration at the time of artificial insemination in lactating Holstein cows. In Chapter 2, I demonstrated that the administration of GnRH increased LH concentration during the first two hours following treatment, and the duration of estrus was positively associated with LH concentration. The effect of GnRH administration on LH levels was not associated with P4 levels of the previous estrous cycle or 7d post-estrous event. The administration of GnRH tended to increase circulating levels of PGFM following an oxytocin challenge 16 days post-estrus. In Chapter 3, I discuss the limitations of the randomized controlled study and provide recommendations for future research directions. In conclusion, the results presented in this thesis suggest that administration of GnRH at the supposed time of AI increases circulating LH concentration, which could elicit benefits for dairy cows' fertility. Further research is needed to elucidate the association of P4 concentration of the previous cycle on the response to GnRH administration and on the effect of GnRH administration on P4 concentration 7d post-estrus and uterine capacity to produce PGFM.
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The effect of progesterone exposure on estrous expression and ovulation timing in holstein heifers (2024)
Concentrations of progesterone (P4) in the estrous cycle preceding AI is positively associated with estrous expression and fertility. Recent research has also shown associations between the estrus to ovulation interval and estrous expression. The aim of this study was to evaluate the associations between P4 concentrations during diestrus with intensity of estrous expression and time from estrus to ovulation in nulliparous Holstein cows. In a randomized cross-over design experiment, post-pubertal heifers (n=31) were pre-synchronized and fitted with a leg-mounted automated activity monitor (AAM). On d-17 relative to estrus, the animals received GnRH, P4 implant for 7 d and GnRH again on d-8. From d-7 to -1, heifers in the high P4 group (HP4) received a new CIDR while the heifers in the low P4 group (LP4) received a second use CIDR. Additionally, heifers in LP4 received multiple PGF2α injection during the diestrus. Heifers in both treatment groups received PGF2α on d-1, and estradiol cypionate on d0. Upon estrus activity alert, and every 4 h after, until ovulation, the ovaries of the heifers were scanned by ultrasonography for the occurrence of ovulation. Blood samples were taken at estrus and 7 d later for P4 analysis. The HP4 treatment had significantly lower P4 concentrations on d0 than the LP4 treatment (P=0.001) and a tendency for higher P4 on d7 after the HP4 treatment (P=0.07). There was no effect of treatment on ovulation timing (hazard of ovulating=1.17 when in the LP4 treatment, 95% CI=0.69–1.98, P=0.56). Estrous expression was not affected by treatment when measured by duration (HP4: 17.7±0.8 h vs LP4: 17.4±0.8 h; P=0.72) or relative increase of activity (HP4: 364.4±24.6 index value vs LP4: 344.6±24.6 index value; P=0.55).
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The impact of plasma concentrations of progesterone during superovulation on estrous behaviour, and ovarian and early embryonic development in Holstein heifers (2022)
Greater progesterone (P4) levels prior to and post estrus in lactating dairy cows has been associated with improved fertility and greater intensity of estrous expression measured by automated activity monitors (AAM). Recently, greater intensity of estrous expression has also been associated with greater embryo production and quality in superovulated dairy heifers. However, it is unclear whether P4 causes greater expression of estrus and increased early embryo development in superovulated heifers. Therefore, the aim of this thesis was to evaluate the effect of different P4 concentrations in plasma during the follicular growth on the intensity of estrous expression, ovarian response to the superovulatory treatment, and embryo production and quality in superovulated Holstein heifers. In Chapter 1, scientific studies are reviewed to highlight gaps in the literature associated with P4 regulation, intensity of estrous expression and reproductive outcomes in dairy cattle. In Chapter 2, I found that different P4 levels during the follicular growth did not affect the maximum intensity of estrous expression or the duration of estrus in superovulated Holstein heifers. However, high P4 concentrations in plasma during the development of follicles increased embryo quality and reduced the number of embryos produced when compared to low P4 concentrations. Although estrous expression did not relate to the quality of embryos, the duration of estrus and the maximum intensity of estrous expression increased the number of embryos recovered 7 d post artificial insemination. In Chapter 3, study limitations and future directions are summarized. In conclusion, my results suggest that P4 concentrations during the follicular growth, and intensity of estrous expression, are important in regulating the quality of embryos and the number of embryos produced by superovulated heifers.
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Humane pigeon population management using avian contraceptive OvoControl? P at TransLink SkyTrain stations in the Lower Mainland of British Columbia, Canada (2021)
Pigeon abundance in urban environments can result in human-wildlife conflicts in the form of excrement, disease, and nuisance behaviour. Managing human-wildlife conflicts using humane, sustainable and safe methods can help mitigate conflicts and ethically address the humane treatment of animals and the environment. Traditional methods of pigeon control include netting open areas, applying spikes to prevent perching, delivering low electric shock to birds on resting surfaces, lethal control through capture and culling, and flying raptors at chosen sites. These methods rely on principles of exclusion and removal which are not effective long-term, as pigeons typically find alternative spaces to evade exclusion attempts and populations slowly increase to pre-treatment size when culled. A relatively new method of management, OvoControl® P is an avian contraceptive developed by Innolytics and is patented for pigeon control in Canada. The active compound in OvoControl® P is nicarbazin 0.5%, which disrupts the egg laying mechanisms in avian species, preventing the formation of a viable embryo. To test its efficacy as a pigeon management method for a major public transit network, eight TransLink SkyTrain stations in the Lower Mainland region of British Columbia, Canada were chosen as study sites between March 2020 and March 2021. Four control site stations dispensed cracked corn and four experimental site stations dispensed OvoControl® P. Trail cameras actively recorded video clips at each station to provide population estimates and confirm pigeons were ingesting OvoControl® P. Measures of success monitored were daily population estimates and track alarm trigger data. Results found that stations dispensing cracked corn increased pigeon populations before and after treatment, while pigeon populations at stations dispensing OvoControl® P did not change before and after treatment. Further, an unexpected result was that higher numbers of pigeons inversely correlated to track alarm triggers, perhaps due to nesting behaviour. The use of OvoControl® P within a public transportation network has shown that it can be scaled and used as a long-term, humane management approach to deal with pigeon control and testing OvoControl® P over longer time periods is recommended to see if subsequent population declines can be observed.
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The use of calving behaviours and automated activity monitors to predict and detect parturition and uterine diseases in Holstein cattle (2020)
Proactive management practices during the transition period are necessary to reduce therisk and mitigate the effect of transition diseases, such as dystocia and uterine diseases, in dairycows. The aims of this thesis were to 1) investigate the relationship between the duration of labour,calving assistance, and uterine diseases (metritis and subclinical endometritis), and 2) investigatethe test performance of relative changes in activity and lying behaviour using two automatedactivity monitors (AAM) to predict calving time and uterine disease. Holstein cows (n = 567) werefollowed from 3wk before to 3wk after calving. Lying behaviour and activity were monitoredcontinuously by the AAMs. Cameras were used to record calving time and duration and calvingassistance was recorded. Metritis was diagnosed based on vaginal discharge and body temperaturemeasured at 6 and 12DIM, while subclinical endometritis was based on cytological examinationat 42 ± 3DIM. Duration of labour was estimated as time from the appearance of the amniotic sacuntil the calf was expelled. Within study 1, we determined that there was a quadratic relationshipbetween metritis and duration of labour for assisted cows, where the probability of metritis wasgreatest at the shortest and longest durations of labour, but the lowest probability of metritis(28.2%) was at approximately 130 min. Probability of metritis in unassisted cows was notassociated with duration of labour. Subclinical endometritis was not associated with the durationof labour or calving score. For study 2, a relative decrease of 44% in lying time per bout, 8 h beforecalving, resulted in the best performance (AUC = 0.76; Se = 67%; Sp = 77%). Distinct changes inactivity and lying behaviour were observed prior to calving and within cows diagnosed withuterine disease. Although current technologies show promising results for on-farm detection ofcalving, they may not be a reliable method for detection of uterine disease. Future research shouldfocus on refining the efficacy of AAMs for the use of health detection.
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Associations between vaginal temperature and induced estrus expression and fertility in lactating holstein cows (2017)
The objective of this study was to determine the effect of vaginal temperature on levels of physical activity expressed by lactating Holstein cows following induced estrus. Lactating Holstein cows (n = 641; 41.5 9.4 kg milk/d) were fitted with a leg-mounted pedometer resulting in 843 evaluated activity episodes of estrus. Vaginal temperature was monitored using thermometers, attached to an intravaginal device that recorded vaginal temperature every 10 min for 3 d. Ambient temperature and relative humidity were monitored using an external thermometer placed in the center of each pen. Milk production and BCS were collected at the time of thermometer insertion. All statistical analysis was performed in R. Heat stress (HS) was calculated based on the percentage of time the cow spent with a vaginal temperature ≥39.1°C (PCT39) 9-11 d prior to Timed Artificial Insemination (TAI), and was classified as high or low (median: 22.9%). The mean vaginal temperature was 38.9 ± 0.2°C, whereas the mean maximum and minimum vaginal temperatures were 39.7 ± 0.5°C and 38.0 ± 0.8°C, respectively, with an average amplitude 1.71 ± 0.9°C. Mean relative increase (RI) of steps/hr at estrus was 237.0 ± 160 %. Animals with low BCS were associated with lower RI compared to cows with medium BCS (260.31 ± 17.45% vs. 296.42 ± 6.62%). Lower temperature and humidity (THI) values (≤ 65) were associated with greater RI compared with medium (> 65 - 70) and high conditions (≥ 70). There was no association between PCT39 on RI. Cows who displayed greater RI at estrus had stronger associations with pregnancy per artificial insemination (P/AI) compared with low RI (27% vs. 20%) and no RI (27% vs. 12%). An interaction was observed between PCT39 and THI on P/AI, where a subpopulation of cows with high PCT39 were associated with decreased P/AI under high THI conditions, but no differences in P/AI were observed for high PCT39 cows under medium and low THI conditions (13% vs. 24% vs. 26%). Future research should aim to refine variables related to hyperthermia as well as understanding the effects of body temperature on estrus expression and fertility.
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Effect of rumen protected vitamin B complex on metabolic parameters, milk production and day 14 conceptus and endometrial gene expression in Holstein dairy cows (2017)
High milk production is associated with sub-fertility in dairy cows due to metabolic demands placed by lactation on the body. The aim of this project was to determine the effects of a rumen-protected vitamin B complex supplementation (VB) compared with a control diet containing no supplementation (CON) on the endometrial gene expression on d 14 of pregnancy. The secondary aim was to look at effect of VB on milk production and components; concentrations of β-hydroxybutyric acid, haptoglobin and progesterone in blood; and ovarian dynamics. Fifty-one multiparous Holstein cows from the herd at The University of British Columbia Dairy Education and Research Centre were enrolled into the study three weeks prior to parturition and were randomly assigned to one of the two treatments. Biweekly blood samples, weekly milk samples and daily feed intake were collected. Cows were enrolled onto a double-ovsynch protocol at 33±3 days post-partum and inseminated by timed artificial insemination (AI). Ovarian structures were monitored and measured using per rectum ultra-sonography. The uterus was flushed on day 14 post AI for conceptus collection and endometrial samples were collected at the same time. Data was analyzed by analysis of variance (ANOVA) using the generalized linear model (GLM) procedure of SAS. Overall, 42 cows were flushed and 13 embryos were collected. VB supplementation had no effect on the size of the embryo, ovulatory follicle size or CL size at embryo collection. Milk production and milk fat values were also similar between the two groups. BHBA and haptoglobin levels between the two groups were also similar. Analysis of expression of genes showed that OXTR, MUC5B, MUC1, IL1β, SPP, TRD, FZD8 and FOLR1 genes were significantly upregulated in the VB group. SELL, PLAU and MYH9 genes showed a tendency to be more upregulated in the endometrium of cows in the VB group compared to those in the CON group. In conclusion, expression of genes related to embryo development, immune system, adhesion and regulation of folate transport were upregulated by supplementation. VB supplementation did not affect of production and health outcomes in lactating dairy cows.
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The effect of expression of estrus at artificial insemination on target genes in the endometrium, conceptus and corpus luteum of beef cows (2015)
The aim of this study was to test the effect of expression of estrus at artificial insemination (AI) on the endometrium, conceptus and corpus luteum (CL) gene expression. Twenty-three multiparous non-lactating Nelore cows were enrolled on an estradiol (E2) and progesterone (P4) based timed-AI protocol (AI = d 0), then slaughtered for endometrium, CL and conceptus collection on d 19. Body condition score (BCS), blood samples and ultrasound examination was performed on d 0, 7 and 18 of the experiment followed by RNA extraction and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis of 58 target genes. Data was checked for normality and analysed by ANOVA for repeated measures using proc GLM, MIXED and UNIVARIATE. Estrous expression had no correlation with parameters such as BCS, pre-ovulatory follicle and CL diameter, P4 concentration in plasma on d 7 and 18 after AI and IFN-tau concentration in the uterine flushing (P > 0.05); however, a significant increase was observed in conceptus size (P = 0.02; 38.3 ± 2.8 vs 28.2 ± 2.9). The majority of transcripts affected by estrous expression in the endometrium belong to the immune system and adhesion molecule family (MX1, MX2, MYL12A, MMP19, CXCL10, IGLL1 and SLPI) (P ≤ 0.05). Genes related to apoptosis, P4 synthesis and prostaglandin receptor were down-regulated (CYP11A, BAX and PGF2α receptor) (P 0.05) in the CL tissue of cows in estrus. In addition, four genes were identified as differentially expressed in the 19 old conceptus from cows observed in estrous (ISG15, PLAU, BMP15 and EEF1A1; P0.05). There was also a significant effect of P4/d7 mainly affecting immune system, adhesion molecules and wnt signaling pathway of endometrium (IGLL1, MX2, SLPI, TRD, APC, WNT2, GLYCAM1 and MYL12A) (P0.05). A significant interaction between estrus expression and P4 concentration on d 7 was more pronounced in immune system genes (MX1, MX2, TRD, SLPI and IGLL1; P0.05). This study demonstrated that estrous expression at the time of AI, in spite of ovulation being induced by E2, could alter the gene expression profile in reproductive tissues during the pre-implantation phase.
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Hair Cortisol: Sampling Methodology and Associations with Health and Reproduction in Dairy Cows (2014)
Dairy cattle are often challenged with stressful practices and conditions. Cortisol is often used as a biomarker to detect stress. Hair is a promising new medium to detect long- term changes of circulating cortisol. This thesis investigated methodologies for the collection and processing of hair for cortisol analysis, and determined associations of hair cortisol concentrations with health disorders and fertility in lactating Holstein cows.First, we investigated the effects of hair colour, sampling location, and processing method on the amount of cortisol extracted from hair samples of 18 black and white Holstein dairy cows. Second, we investigated the associations between hair cortisol with clinical and subclinical disease, and reproductive success. Hair samples were collected from the tail switch of lactating Holstein cows to determine the effects of clinical disease and fertility (n = 64), or subclinical disease (n = 54).White hair had greater cortisol concentrations than black hair (Geometric Mean [95% CI]) (7.8 [6.8, 9.2] vs. 4.2 [3.6, 5.0] pg/mg). When only white samples were analyzed, hair from the tail switch had more cortisol than the shoulder (11.0 [7.6, 16.0] vs. 6.2 [4.2, 9.2] pg/mg). Processing with a ball mill yielded greater concentrations of extracted cortisol than when using scissors (10.4 [5.8, 18.8] vs. 4.7 [2.6, 8.4] pg/mg). In Holsteins, the tail switch is always white and grows faster making it an ideal location for measuring hair cortisol.Animals with clinical disease presented higher hair cortisol concentrations than clinically healthy animals (8.8 [7.8, 9.9] vs. 10.7 [9.6, 12.0] pg/mg); however, animals diagnosed with subclinical disease did not differ (11.5 [9.7, 13.7] vs. 11.3 [9.6, 13.3] pg/mg for healthy and subclinical groups, respectively). Multiparous cows that became pregnant by 100 days postpartum had lower hair cortisol concentrations at 42 and 84 DIM.Overall, using standard and consistent methods to sample, cortisol in hair offers important insights into long-term changes of circulating cortisol. Hair cortisol concentrations appear to be associated with clinical disorders and have a direct association with pregnancy outcomes; however, hair cortisol concentrations may not be suited to differentiate situations of stress with lower magnitudes, such as subclinical disease.
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