Papers by Scott Mcdougall
Journal of Dairy Science
The objectives of the study were to define the sensitivity and specificity of the California Mast... more The objectives of the study were to define the sensitivity and specificity of the California Mastitis Test (CMT) in determining the presence of intramammary infection in postpartum dairy goats and to determine whether antibiotic therapy increased bacteriological cure rate and lowered somatic cell count (SCC) compared with untreated controls. A CMT was performed and milk samples were collected for bacteriology from 211 glands of 106 does between 0 and 10 d after kidding. From a population of 3,239 glands from goats in 4 commercial herds, goats with one or both glands with a CMT score of >1 and from which bacteria were isolated were either assigned to be treated with 3 intramammary infusions at 12-h intervals of 75 mg of sodium ampicillin and 250 mg of sodium cloxacillin (n=57 glands) or left as untreated controls (n=49 glands). Milk samples were collected again 14 ± 3 and 21 ± 3 d later for bacteriology and SCC determination. Composite milk yield, goat SCC, length of lactation, an...
New Zealand veterinary journal
Abstract AIMS: The main aim was to investigate the efficacy of a novel internal teat sealant (ITS... more Abstract AIMS: The main aim was to investigate the efficacy of a novel internal teat sealant (ITS) formulation containing bismuth subnitrate and the antiseptic chlorhexidine, in adult cows (Trial A) and nulliparous heifers (Trial B), to reduce the incidence of new intramammary infection (IMI) between treatment and calving and reduce the prevalence of IMI within 6 days following calving. In Trial A dairy cows (n = 326) without history of clinical mastitis and with a maximum composite milk somatic cell count <200,000 cells/mL during the current lactation were enrolled from three spring-calving mainly pasture-based herds immediately following the final milking. In Trial B all heifers (n = 166) were enrolled from two herds approximately 3 weeks before the start of calving. Glands were randomly assigned to controls or treatment with ITS, and mammary secretion samples were taken from all glands prior to treatment, and on two occasions 0-4 and 3-6 days post-calving to determine the inci...
New Zealand veterinary journal
To determine the prevalence of intramammary infection (IMI) of lactating dairy goats between 0 an... more To determine the prevalence of intramammary infection (IMI) of lactating dairy goats between 0 and 4 days postpartum, the prevalence and incidence rate of new IMI at Weeks 2, 14 and 27 of lactation, and the relationship between herd-level prevalence of IMI and bulk tank somatic cell count (BTSCC). Milk samples were collected from 8% of a herd (total 624 does) from 18 dairy goat herds in the Waikato region of New Zealand, for bacteriology and somatic cell count (SCC) determination, from both glands within 4 days of kidding (Week 0) and again at Weeks 2, 14 and 27. Prevalence of IMI was determined at each time point and incidence rate calculated for Weeks 0-2, 2-14, and 14-27. Greenwood and Reed-Frost models were compared for estimation of the transmission parameter for all pathogens, and for Staphylococcus aureus, coagulase negative staphylococci (CNS) and Corynebacterium spp. separately. Bacteria were isolated from 1,122/4,814 (23.3%) glands, with CNS (13.4%) and Corynebacterium spp...
Theriogenology, 2005
The objectives of this study were to evaluate the effect using two doses of progesterone (P4) rel... more The objectives of this study were to evaluate the effect using two doses of progesterone (P4) releasing devices in two different programs on reproductive performance of anestrous dairy cows. Cows (n = 1555) not detected in estrus by 10 d before the planned start of the seasonal breeding program and in which no CL was palpable were treated with an intravaginal P4-releasing device ('Single'; $1.56 g of P4) or a modified device with triple the normal P4 dose ('Triple'; $4.7 g of P4). The devices were in place for either 6 d ('Short') or 8 d ('Long'), with 1 mg estradiol benzoate (EB) given 24 h after device removal. The 'Long' program also included treatment with 2 mg EB at device insertion. The Long program resulted in a higher first service conception rate (RR = 1.18 (95% CI = 1.03-1.33); P = 0.02), but had no effect on the 28-d, 56-d or final pregnancy rate compared to the Short program. There were no effects of dose of P4 on any outcome. In conclusion, the Long compared to the Short program, but not the dose of P4, improved first service conception rates in anestrous cows. #
Journal of Dairy Science, 2012
Heifer mastitis is a disease that potentially threatens production and udder health in the first ... more Heifer mastitis is a disease that potentially threatens production and udder health in the first and subsequent lactations. In general, coagulase-negative staphylococci (CNS) are the predominant cause of intramammary infection and subclinical mastitis in heifers around parturition, whereas Staphylococcus aureus and environmental pathogens cause a minority of the cases. Clinical heifer mastitis is typically caused by the major pathogens. The variation in proportions of causative pathogens between studies, herds, and countries is considerable. The magnitude of the effect of heifer mastitis on an individual animal is influenced by the form of mastitis (clinical versus subclinical), the virulence of the causative pathogen(s) (major versus minor pathogens), the time of onset of infection relative to calving, cure or persistence of the infection when milk production has started, and the host&#39;s immunity. Intramammary infection in early lactation caused by CNS does not generally have a negative effect on subsequent productivity. At the herd level, the impact will depend on the prevalence and incidence of the disease, the nature of the problem (clinical, subclinical, nonfunctional quarters), the causative pathogens involved (major versus minor pathogens), the ability of the animals to cope with the disease, and the response of the dairy manager to control the disease through management changes. Specific recommendations to prevent and control mastitis in late gestation in periparturient heifers are not part of the current National Mastitis Council mastitis and prevention program. Control and prevention is currently based on avoidance of inter-sucking among young stock, fly control, optimal nutrition, and implementation of hygiene control and comfort measures, especially around calving. More risk factors for subclinical and clinical heifer mastitis have been identified (e.g., season, location of herd, stage of pregnancy) although they do not lend themselves to the development of specific intervention strategies designed to prevent the disease. Pathogen-specific risk factors and associated control measures need to be identified due to the pathogen-related variation in epidemiology and effect on future performance. Prepartum intramammary treatment with antibiotics has been proposed as a simple and effective way of controlling heifer mastitis but positive long-lasting effects on somatic cell count and milk yield do not always occur, ruling out universal recommendation of this practice. Moreover, use of antibiotics in this manner is off-label and results in an increased risk of antibiotic residues in milk. Prepartum treatment can be implemented only as a short-term measure to assist in the control of a significant heifer mastitis problem under supervision of the herd veterinarian. When CNS are the major cause of intramammary infection in heifers, productivity is not affected, making prepartum treatment redundant and even unwanted. In conclusion, heifer mastitis can affect the profitability of dairy farming because of a potential long-term negative effect on udder health and milk production and an associated culling risk, specifically when major pathogens are involved. Prevention and control is not easy but is possible through changes in young stock and heifer management. However, the pathogenesis and epidemiology of the disease remain largely unknown and more pathogen-specific risk factors should be identified to optimize current prevention programs.
New Zealand Veterinary Journal, 2014
The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in... more The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in mainly pasture-grazed dairy cows in three dairy-farming regions of New Zealand 7-12, and 35-40 days post-calving. A second aim was to investigate herd- and cow-level factors associated with the prevalence of SCK. A cross-sectional longitudinal prevalence survey was undertaken in 1,620 dairy cows from 57 herds. A random sample of cows without disease in the prior 30 days were enrolled at one farm visit within 5 days of calving, and blood samples were collected 7 and 28 days later (7-12 and 35-40 days post-calving) for measurement of beta-hydroxy butyrate (BHBA) concentrations using an electronic cow-side meter. SCK was defined as blood BHBA concentration ≥1.4 mmol/L. Mean cow-level prevalence of SCK varied with interval post-calving (16.8 and 3.2% at 7-12 days and 35-40 days post-calving, respectively) and age (13.0 and 13.1% of 2-year olds and ≥8-year olds, respectively, compared to 7.2% of 3-4-year-old cows). Mean herd-level prevalence of SCK was 14.3 (min 0, max 60.0)% and 2.6 (min 0, max 24.4)% at 7-12 days and 35-40 days post-calving, respectively, and was greater in Southland (13.3%) than Waikato and Canterbury herds (6.9 and 4.7%, respectively). This is the first population-based report of the prevalence of SCK in New Zealand dairy herds and demonstrates that age and interval post-calving are important risk factors determining prevalence; and that there is wide variation in prevalence between herds. Subclinical ketosis may be unrecognised but common in many New Zealand dairy cows in the first 2 weeks of lactation.
Australian Veterinary Journal, 2009
Objective To investigate the practical application and image quality of transcutaneous ultrasonog... more Objective To investigate the practical application and image quality of transcutaneous ultrasonography across the right flank for the diagnosis of mid-to late-gestation in cattle.
Australian Veterinary Journal, 2009
Objective Evaluate the sensitivity and specificity of transrectal ultrasound and transcutaneous u... more Objective Evaluate the sensitivity and specificity of transrectal ultrasound and transcutaneous ultrasonography across the right flank between days 31 and 196 of pregnancy in the dairy cow.
Australian Veterinary Journal, 2009
To determine bovine fetal characteristics significantly associated with increasing gestational ag... more To determine bovine fetal characteristics significantly associated with increasing gestational age as measured via transcutaneous ultrasonography over the right flank. The length of gestation at date of pregnancy diagnosis via transcutaneous and transrectal ultrasonography was determined for 224 dairy cattle by estimation from subsequent calving dates. A separate dataset was created for each measurable fetal characteristic (i.e. thoracic diameter, abdominal diameter, umbilical diameter, placentome length and placentome height) and risk factors significantly associated with gestational age at pregnancy diagnosis within each dataset, including the fetal characteristic, were identified. Abdominal diameter was the most frequently observed fetal characteristic and thoracic diameter was the least. Gestational age at pregnancy diagnosis (d) was significantly associated with fetal thoracic diameter (P &lt; 0.01), abdominal diameter (P &lt; 0.01) and umbilical diameter (P = 0.02) when measured via transcutaneous ultrasound. Within each model, sire breed, dam breed, dam age and/or calf sex were also significantly associated with gestational age. Gestational age at pregnancy diagnosis was not significantly associated with either placentome height or length (P &gt; 0.05). Fetal thoracic diameter, abdominal diameter and umbilical diameter were found to be significantly associated with gestational age between approximate days 73 to 190 of gestation. Transcutaneous ultrasonography may prove a useful method of estimating gestational age in the absence of accurate breeding records.
Animal Reproduction Science, 2007
Endometritis reduces reproductive performance in dairy cattle. Diagnosis of endometritis is under... more Endometritis reduces reproductive performance in dairy cattle. Diagnosis of endometritis is undertaken using a variety of techniques including vaginoscopy, manual examination, cytology and ultrasonography. The current studies compared a novel test device ("metricheck") that is inserted into the vagina with vaginoscopy and then examined the relationship between the metricheck test score at 35 days before the start of the seasonal breeding programme and subsequent reproductive performance. Cows (n = 191; Study 1) with a history of a peripartum disease were examined by both vaginoscopy and the metricheck device and any material viewed within the vagina (using vaginoscopy) or retrieved (by the metricheck device) was scored on a 0 (no material) to 5 (grossly purulent and with an odour) scale. Within each herd the order of examination was randomized with sequentially presented pairs of cows. All cows (n = 2793; Study 2) from nine herds were examined and scored using the metricheck device 35 days before the start of the seasonal breeding programme. All cows were pregnancy tested to determine date of conception.
Journal of Dairy Science, 2009
An out-of-date version of Figure 5 was presented on page 4429. The corrected version of the figur... more An out-of-date version of Figure 5 was presented on page 4429. The corrected version of the figure is presented here. The authors regret the error. McDougall, S., M. A. Bryan, and R. M. Tiddy. 2009. Effect of treatment with the nonsteroidal antiinflammatory meloxicam on milk production, somatic cell count, probability of re-treatment, and culling of dairy cows with mild clinical mastitis. J. Dairy Sci. 92(9):4421-4431 J. Dairy Sci. 92 :5765-5765
Abstract Subclinical endometritis (SCE) is a form of uterine pathology characterised by an increa... more Abstract Subclinical endometritis (SCE) is a form of uterine pathology characterised by an increased proportion of polymorphonuclear cells (PMN) in the uterus after calving. Recent reports indicate that poorer reproductive outcomes among cows with SCE are associated with local and systemic inflammation. Therefore treatment of SCE needs to focus on reducing inflammation. Normal uterine involution is, however, a prostaglandin-mediated inflammatory event. The hypothesis tested was that treatment with a non-steroidal anti-inflammatory drug (NSAID) at 21-31 days postpartum would reduce the severity (average PMN %) of uterine pathology at 42 days postpartum and not lengthen the postpartum anovulatory interval (PPAI). To test this hypothesis, dairy cows (n = 213) were paired by calving date and Day 14 PMN %, then randomly assigned to three doses of a NSAID (Carprofen 1.4 mg/kg, n = 103) between 21-31 days postpartum or left as untreated controls (n = 108). In this study, ≥ 14% PMN in the c...
Inflammation of the endometrial lining of the uterus (endometritis) often develops in dairy cows ... more Inflammation of the endometrial lining of the uterus (endometritis) often develops in dairy cows soon after calving. Afflicted animals can develop chronic infections of the uterus due to pathogenic bacteria. This disease causes poor reproductive performance, decreased energy balance, lower milk yield, and potentially hepatocellular damage. The objective of the current study was to uncover molecular changes induced by endometritis using expression profiling of liver and adipose transcriptomes. Postpartal liver and adipose tissue samples were harvested at slaughter from healthy (NUI; n = 6) cows or cows with endometritis (UIN; n = 6) at 29 d postpartum. Endometritis was defined as >6% of uterine fluid nucleated cells being polymorphonuclear (PMN) cells; healthy cows had ≤1% PMN. Transcriptome expression was performed via bovine microarray (~13,000 oligonucleotides) and RT-PCR. Functional analysis of differentially expressed genes (DEG; P < 0.05, fold-change cut off ≥ or ≤ 1.5 UI...
animal
There has been a long history of herd health and production management programmes in many dairy i... more There has been a long history of herd health and production management programmes in many dairy industries around the world, but evidence for the efficacy of such programmes is limited. In response to a perceived decline in fertility of dairy cows, a herd reproductive management programme (InCalf) was introduced in New Zealand in 2007. This programme uses a management cycle approach that includes an assessment of the current herd status, identification of areas for improvement, development of a plan, implementation of this plan and finally a review process. The programme uses facilitators who work with farmers either in a one-to-one manner or in a formalised group setting that involves a series of meetings over a 12-month period (the farmer action group). The hypothesis that involvement in a reproductive management programme would improve herd reproductive performance was tested using a herd-level controlled randomised study (the National Herd Fertility Study) involving herds in fou...
Journal of Dairy Science
The objective of this study was to determine if the inflammation associated with subclinical endo... more The objective of this study was to determine if the inflammation associated with subclinical endometritis (SCE) is a part of the mechanism by which reproductive performance is reduced in cows with this disease. If it is, reducing inflammation associated with SCE with a nonsteroidal antiinflammatory drug (NSAID) should reduce the severity [as measured by average polymorphonuclear cell (PMN) percentage] of uterine pathology and improve reproductive performance. It was also investigated whether the NSAID treatment reduced metabolic indicators of systemic inflammation previously reported to be altered in cows with SCE. Holstein-Friesian and Friesian-Jersey cross dairy cows (n = 213) were paired by calving date and d-14 uterine PMN percentage and randomly assigned to 3 injections at intervals of 3 d of an NSAID (1.4 mg of carprofen/kg; n = 104) between 21 and 31 d postpartum or left as untreated controls (n = 109). Cows with ≥14% PMN (upper quartile of PMN percentage) in the cytological ...
The Veterinary Journal
A group-based reproductive management extension programme has been designed to help managers of d... more A group-based reproductive management extension programme has been designed to help managers of dairy herds improve herd reproductive performance. The aims of this study were, firstly, to assess effects of participation by key decision makers (KDMs) in a farmer action group programme in 2009 and 2010 on six key management outcomes (KMOs) that affect reproductive performance over 2 years (2009–2010 and 2010–2011), and secondly, to describe KDM intentions to change management behaviour(s) affecting each management outcome after participation in the programme. Seasonal calving dairy herds from four regions of New Zealand were enrolled in the study. Intentions to modify management behaviour were recorded using the formal written action plans developed during the extension programme. KMOs assessed were calving pattern of the herd, pre-calving heifer liveweight, pre-calving and premating body condition score (BCS), oestrus detection, anoestrus cow management and bull management. Participa...
Journal of Dairy Science
Previous research results have indicated an increase in pregnancy rate in pasture-grazed cows tre... more Previous research results have indicated an increase in pregnancy rate in pasture-grazed cows treated with a nonsteroidal antiinflammatory drug (NSAID) 3 to 4 wk postcalving, when a high proportion of nucleated cells from within the uterus were polymorphonucleated; however, no effect on milk production was detected. It was hypothesized that this lack of effect on milk production was because the administration of the NSAID was too late after calving. The aims of the current study were to evaluate the timing of administering a propionic acid-derived NSAID (i.e., carprofen) on milk production, metabolic status, uterine health, and reproductive performance. Six-hundred and thirty-nine cows (134 primiparous and 505 multiparous) calving between July 4 and September 5, 2012, in 2 herds (herd 1: n = 228; herd 2: n = 411) were enrolled. Using a randomized block design, cows were allocated to 1 of 3 treatment groups as they calved: (1) no treatment (control; n = 221), (2) NSAID administered o...
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Papers by Scott Mcdougall