Ontario Farm Research Articles

Inflow Parameter Effects on Wind Turbine Tower Cyclic Loading

Wind turbine towers are fatigue-critical structures subjected to a variety of atmospheric wind regimes at onshore installations. At a commercial wind farm in Southwestern Ontario, the structural steel supporting tower of a multi-megawatt horizontal-axis turbine has been instrumented with a fiber Bragg grating strain gauge array. A nearby meteorological mast allows wind conditions to be classified on the basis of horizontal turbulence intensity and vertical wind shear. Data has been collected over a measurement campaign spanning multiple months, and a sample of the tower's cyclic loading history has been compiled. Comparisons are drawn between accumulated hourly loading cycle spectra for operation across different upwind inflow parameters.

Producer concern and prevalence of subclinical intramammary infections between lactations on 10 dairy goat farms in Ontario, Canada

For many dairy goat producers, a key deciding factor for keeping does in the herd is the animal’s ability to maintain milk production. Subclinical intramammary infections (IMIs) are known to decrease milk production in does by as much as 20% (Contreras et al, Livest Prod Sci, 2003). Somatic cell count (SCC) is a reliable and inexpensive predictor of infection in dairy cows; however, this measure is highly variable in goats depending on factors such milk production, stage of lactation, and estrus activity (Leitner et al, J Dairy Sci, 2004; Paape et al, Small Rumin Res, 2007; Persson et al, Small Rumin Res, 2014), making identification of infected glands by SCC level problematic. Thus, it is likely that producers underestimate infection prevalence on their farms. While IMIs are possible throughout lactation, the highest risk period for infection is when does are transitioning from one lactation to the next. On many farms, goats are dried-off (i.e., milking is ceased) and during the dry period infections may go unchecked and new infections begin. In other situations, does are not dried-off between lactations. The aims of this study were 2-fold: 1) to assess the attitudes of the producers regarding IMIs on their farms, and 2) to determine the prevalence of these infections during the dry period.

Evaluation of the utility of subjective clinical parameters for estimating fecal egg counts and packed cell volume in Canadian sheep flocks

A study was conducted in sheep on Canadian farms to describe the relationship between packed cell volume (PCV) or fecal egg counts (FEC) and subjective clinical parameters that may indicate the severity of parasitic gastroenteritis. Twenty-one farms in Ontario (ON) and 8 farms in Quebec (QC) were purposively selected and visited during April–May (spring) and August (summer) 2007. At each farm visit, blood and fecal samples were collected from 10 ewes and 10 female lambs; body condition score (BCS), dag score (DS), fecal consistency score (FCS) and FAMACHA score were recorded for all sampled sheep. Packed cell volume was determined for all blood samples, and FEC were performed for all fecal samples. Summary statistics and simple correlations were performed for the parameters recorded. Two mixed models with random effects at the farm level were developed; one using PCV as the response variable and another using the natural log of eggs per gram of feces (lnEPG). Finally, the residuals from both models were correlated to the covariates in the models. The mean PCV values during the spring were 29.7% and 36.7% for lambs, and 28.8% and 31.1% for ewes, in ON and QC, respectively. During the summer, the mean PCV was 32.0% and 32.8% for lambs, and 30.1% and 29.9% for ewes, in ON and QC, respectively. The arithmetic mean FEC per gram of feces (EPG) during the spring was 3 and 2 for lambs, and 1266 and 789 for ewes, in ON and QC, respectively, whereas during summer the arithmetic mean EPG was 907 and 237 for lambs, and 458 and 246 for ewes, in ON and QC, respectively. Results from simple correlations indicated that PCV was negatively correlated with lnEPG (r=−0.255; r2=6.5%) and FAMACHA (r=−0.312; r2=9.7%), and positively correlated with BCS (r=0.317; r2=10%). LnEPG was negatively correlated with BCS (r=−0.232; r2=5.4%) and PCV (r=−0.255; r2=6.5%), but positively correlated with FAMACHA (r=0.178; r2=3.2%) and DS (r=0.086; r2=0.7%). Results from the models indicated that PCV and lnEPG residuals were negatively correlated with FAMACHA, FCS and almost all categories of BCS and DS, although the correlations were very low. The main results from this study suggested that none of the subjective clinical parameters evaluated were highly correlated with PCV or lnEPG and therefore were not good predictors of lnEPG or PCV on the studied farms in Ontario and Quebec.

Prevalence of antibodies to Leptospira in wild mammals trapped on livestock farms in Ontario, Canada.

To determine the prevalence and diversity of Leptospira serogroups circulating in wildlife on farms in Ontario, we tested samples from 51 raccoons (Procyon lotor), seven skunks (Mephitis mephitis), four rats (Rattus norvegicus), and three opossums (Didelphis virginiana) that were trapped on 27 livestock (swine [Sus scrofa], cattle [Bos taurus]) farms in 2010. Seventeen of 51 raccoons (33%; 95% confidence interval [CI], 21-48%) sampled were positive for at least one Leptospira serogroup using the microscopic agglutination test. None of the other 14 animals had detectable Leptospira antibodies. On swine farms, 13 of 30 raccoons (43%; 95% CI, 27-61%) were antibody positive, and on cattle farms, four of 21 raccoons (19%; 95% CI, 8-40%) were positive. Leptospira antibody prevalence in raccoons did not differ between swine and cattle farms. Raccoons were positive to serovars representative of serogroups Grippotyphosa, Australis, Icterohaemorrhagiae, and Pomona and were negative to serovars of serogroups Autumnalis, Canicola, and Sejroe. The prevalence of Leptospira antibodies in raccoons in this study is similar to what has been reported previously; however, the diversity of serogroups was higher in this study than what has been reported in raccoons from an urban area of Ontario, Canada. Understanding the prevalence and distribution of Leptospira serogroups in wildlife in Ontario, Canada, is important for the development and maintenance of appropriate disease management strategies in humans, livestock, and companion animals.

Testing for Aleutian Mink Disease Virus in the River Otter (Lontra canadensis) in Sympatry with Infected American Mink (Neovison vison)

Aleutian mink disease virus (AMDV) occurs in the American mink (Neovison vison) in wild populations and on mink farms and can cause illness and death. The North American river otter (Lontra canadensis) may be exposed to AMDV because of shared space and habitat with mink. Using serology and real-time PCR, we tested river otters across Ontario for AMDV infection. We found no evidence of infection in otters, a surprising finding given the sympatric distribution, niche overlap, and close phylogenetic relationship of the river otter and the American mink. Our results are consistent with the hypothesis that the major point of spillover of AMDV between mink farms and wildlife is manure and composting carcasses on mink farms. Mink farms in Ontario are generally in agricultural landscapes; it is unlikely that river otter use these habitats and thus are likely not exposed to AMDV. We found no evidence that AMD is an important disease for the river otters in Ontario.

Linuron Biologically Effective Dose for Glyphosate-Resistant Giant Ragweed (<i>Ambrosia trifida</i> L.) Control in Soybean (<i>Glycine max</i> L.)

Glyphosate-resistant (GR) giant ragweed (Ambrosia trifida L.) was first identified in Canada in 2008 and has since been found throughout southwestern Ontario. Six field trials were conducted over a two-year period (2012, 2013) on Ontario farms with GR giant ragweed to evaluate the efficacy of linuron applied pre-plant (PP) in soybean (Glycine max (L.) Merr.). The dose required for 50%, 80%, and 95% GR giant ragweed control was 1238, 2959, and 6018 g·ai·ha-1 four weeks after application (WAA), respectively. The linuron dose needed for 50%, 80%, and 95% reduction in density was 1554, 3181, and 5643 g·ai·ha-1 and 1204, 2496, and 4452 g·ai·ha-1 for dry weight, respectively. Application of 7874 g·ai·ha-1 linuron was needed to obtain soybean yields that were 90% of the weed-free control; approximately 3.5 times the maximum field recommended dose. To achieve 95% and 98% yields, greater than 8640 g·ai·ha-1 linuron was required. Application of linuron plus glyphosate PP in soybean will help to control GR giant ragweed as well as reduce GR selection pressure.

An epidemiological investigation into the association between biomarkers and growth performance in nursery pigs

BackgroundBiomarkers are useful tools in research and clinical practice where they are often used to detect and monitor differences in the physiological state of an animal. The proteins IGF-1, IGFBP-3, GHR, CRP, SAA, Hp, IFN-α, IFN-γ, TNF-α, IL-1β, IL-6, IL-10, and IL-18 have been proposed as potential biomarkers for monitoring growth in livestock. The objective of this study was to determine whether hepatic gene expression of these proposed biomarkers is associated with growth performance in nursery pigs. Herd information and growth parameters were collected for 168 piglets from 8 commercial farms in southern Ontario. From these pigs, a subset of liver tissue samples (n = 74) was used for gene expression analysis of the proposed biomarkers. Multivariable linear regression methods were used to determine whether genetic expression of the proposed biomarkers was associated with growth performance in the nursery.ResultsModelling the herd information and individual piglet traits in relation to growth performance revealed that the weight at weaning and the age at weaning are significantly associated with nursery performance. Average daily gain (ADG) was significantly associated with hepatic IGFBP-3 and GHR expression in the liver (P < 0.05), and tended to be associated with hepatic IGF-1 expression (P = 0.071). Similarly, 9-week body weight was significantly associated with hepatic expression of IGFBP-3 and GHR expression (P < 0.05), and tended to be associated with hepatic expression of IGF-1 (P = 0.055).ConclusionThe age and weight at which pigs are weaned is an important determinant for nursery performance. Hepatic gene expression of IGF-1, IGFBP-3, and GHR can be useful biomarkers for monitoring growth performance in nursery pigs.

Efficacy of targeted anthelmintic treatment for suppression of the peri-parturient egg rise in ewes and impact on 50-day lamb weights

This study was conducted to determine whether targeted anthelmintic treatment of peri-parturient ewes lambing in the winter, spring and/or autumn would suppress the peri-parturient egg rise (PPER) and improve 50-day lamb weights. Three farms in Ontario, Canada, that practiced out-of-season lambing were enrolled in 2010 and sampled for three consecutive lambing seasons (winter, spring and autumn). For each lambing season, all farms were visited three times. On the first visit, all ewes due to lamb that season were randomly allocated to treatment with ivermectin, fenbendazole or levamisole at the recommended dosage, or left untreated. Among these treated ewes, 40–60 animals (10–15 ewes per treatment group) were randomly selected for fecal sampling during the 3 sampling visits and processed individually to measure gastro-intestinal nematode (GIN) fecal egg counts (FECs). Ewe and lamb productivity data, including approximate 50-day lamb weights, were collected for all ewes lambing in each season, where available. A Fecal Egg Count Reduction Test was performed on all three farms to determine the ivermectin, fenbendazole and levamisole resistance status. Both farms A and B had fenbendazole resistance, while farm C had ivermectin and fenbendazole resistance; levamisole was effective on all three farms. The effect of targeted treatment on the subsequent PPER depended on the farm, possibly a partial surrogate variable for the different anthelmintic resistance levels on each farm, lambing season and sampling time-point. On farm A, during the winter and autumn lambing seasons, ivermectin and levamisole were more effective at reducing the FECs, compared to fenbendazole. In contrast, during the spring lambing season, treatment of ewes with ivermectin, fenbendazole or levamisole had no effect on the FECs. On farm B, all anthelmintic treatments were associated with a reduction in the FECs during the spring lambing season, while no reduction was observed during the winter and autumn lambing seasons. On farm C, the FECs decreased in ewes treated with levamisole in both the winter and spring lambing seasons, while ivermectin only reduced the FECs in ewes treated in the winter lambing season. Litter size was positively associated with FECs. Anthelmintic treatment was not associated with approximate 50-day lamb weights, although the power to detect significant difference was lower than anticipated due to only having relevant weight data from farm A. These results suggest that the efficacy of targeted treatment for the suppression of the PPER depends on the anthelmintics’ efficacy and time of treatment in relation to the grazing period.

Factors associated with morbidity, mortality, and growth of dairy heifer calves up to 3 months of age

Calfhood disease is an important problem on many dairy operations that can have substantial effects on heifer survival and productivity, and has economic and welfare impacts. Neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) are the most common causes of morbidity and mortality in young dairy cattle. The objective of this observational study was to investigate factors associated with the risks of morbidity and mortality, and with growth, in commercial dairy heifers calves. A total of 2874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1–7 days of age and followed for approximately 3 months. Using cut-points of serum total protein of 5.2 and 5.7g/dl, the incidences of failure of transfer of passive immunity (FTPI) were 11 and 32%, respectively. A cut-point of 5.7g/dl was the most predictive of BRD before 5 weeks of age (sensitivity=40%, specificity=69%). The positive predictive value was poor (PPV=18%), but the negative predictive value was good (NPV=87%). A cut-point of 5.2g/dl was most predictive of death before 5 weeks of age (sensitivity=27%, specificity=89%, PPV=5%, NPV=98%). Serum total protein during the first week of life was a poor predictor of NCD. Over 23% of calves were treated for diarrhea. Risk factors were weight at enrollment, other diseases before 2 weeks of age, and an interaction between season of birth and herd-level incidence of NCD. Almost 22% of calves were treated at least once for BRD. Factors associated with an increased risk of BRD included herd-level incidence of BRD, season of birth, navel dipping, other diseases before 2 weeks of age, failure of transfer of passive immunity, and manual control of temperature in pre-weaning housing. Administration of supplemental antibody products at birth was associated with a reduced incidence of BRD. Overall mortality was 3.5%. Risk of mortality was increased by treatment for BRD and other diseases. The mean average weight gain was 0.95kg/day (range: 0.11–1.62kg/day; SD=0.2). Twinning status, FTP, treatment for NCD or other diseases, and month of birth influenced body weight. This study illustrated relationships among various diseases, mortality, and growth. Furthermore, it demonstrated the importance of colostrum for protection against BRD and improved growth performance, while bringing into question the optimal method of determining failure of transfer of passive immunity.

Prevalence of Mycobacterium avium subsp paratuberculosis (MAP) ELISA-positive cows and assessment of MAP transmission risk on organic dairy farms in Ontario, Canada

Johne's disease (JD) is caused by Mycobacterium avium spp paratuberculosis (MAP). It is an incurable, chronic inflammation of the gastrointestinal tract of cattle that causes diarrhea, weight loss, and reduced production. Commonly recognized risk factors for MAP transmission include purchase of subclinically infected cows and the infection of calves through ingestion of manure, colostrum or milk containing MAP shed by infected cattle. To limit the negative effects of JD on the dairy industry in Ontario, Canada, the voluntary Ontario Johne's Education and Management Assistance Program (OJEMAP) was implemented in January 2010. Producers can participate in MAP antibody ELISA testing and an on-farm risk assessment and management plan (RAMP) with their herd veterinarian. High RAMP scores are associated with high risk for MAP transmission.&#x0D; Organic farming is one of the fastest growing agricultural sectors worldwide. In Ontario, approximately 80 dairy farms (2% of all dairy farms) are certified organic. While most organic farmers tend to maintain closed herds, which would reduce the risk for JD introduction, they also often support prolonged contact between newborn calves and their dams. These and other factors could potentially influence the risk of MAP transmission as well as JD prevalence and prevention efforts on organic dairy farms. The aim of this cross-sectional study was to assess the Johne's ELISA prevalence and Johne's disease transmission risk on organic dairy farms in Ontario.

Assessing the cryptic invasion of a domestic conspecific: American mink in their native range

Control of invasions is facilitated by their early detection, but this may be difficult when invasions are cryptic due to similarity between invaders and native species. Domesticated conspecifics offer an interesting example of cryptic invasions because they have the ability to hybridize with their native counterparts, and can thus facilitate the introgression of maladaptive genes. We assessed the cryptic invasion of escaped domestic American mink (Neovison vison) within their native range. Feral mink are a known alien invader in many parts of the world, but invasion of their native range is not well understood. We genetically profiled 233 captive domestic mink from different farms in Ontario, Canada and 299 free-ranging mink from Ontario, and used assignments tests to ascertain genetic ancestries of free-ranging animals. We found that 18% of free-ranging mink were either escaped domestic animals or hybrids, and a tree regression showed that these domestic genotypes were most likely to occur south of a latitude of 43.13°N, within the distribution of mink farms in Ontario. Thus, domestic mink appear not to have established populations in Ontario in locations without fur farms. We suspect that maladaptation of domestic mink and outbreeding depression of hybrid and introgressed mink have limited their spread. Mink farm density and proximity to mink farms were not important predictors of domestic genotypes but rather, certain mink farms appeared to be important sources of escaped domestic animals. Our results show that not all mink farms are equal with respect to biosecurity, and thus that the spread of domestic genotypes can be mitigated by improved biosecurity.

Providing elevated ‘getaway bunks’ to nursing mink dams improves their health and welfare

Farmed mink infants (Neovison vison) remain with their mothers beyond natural weaning age. This benefits their welfare, but can stress their mothers and contribute to illness (e.g. ‘nursing sickness’). European studies have explored augmenting cages with structures allowing mothers to get away from their infants (‘kits’); these show that if provided with high, shelf-like structures permitting rest away from kits, dams utilise them. Here, we assessed the benefits of providing an elevated ‘getaway bunk’ – a wire-mesh half-cylinder attached to the cage ceiling – to 80 Black dams on an Ontario farm. Controls comprised nursing females without bunks (n=80), and barren females given bunks (n=40). Behaviour was observed daily over kit ages 23–42 days. Mothers were removed from litters at 42 days (typical for North American farms), at which time health and production parameters were recorded. Mothers used bunks approximately half as much as barren dams, but their bunk-use increased as kits aged, up to c. 7% scans (c. 30min per observation day). Seasonal changes in temperature did not explain this pattern. Bunks increased maternal rest (from 78.9 to 82.3% of scans; c. 16min per observation day), and increased the time spent with teats inaccessible to kits by a similar amount. Dams with bunks showed approximately one third less stereotypy (3.7% scans, compared to 5.4% in bunkless controls): a reduction most evident when kits were aged 30–42 days, when infants transition from milk to water and solid food; and, although apparently not protected from nursing sickness, at the end of lactation they were less likely to have swollen, red and/or crusty teats (which thermal imaging also showed were significantly hotter), suggesting less mastitis. Such benefits seemed particularly strong in multiparous dams: effects of bunks on teat health and stereotypy as a proportion of activity (not scans) were significant in older dams but not first-time mothers when analysed separately. Kits’ suckling opportunities and time spent nursing were not significantly reduced by the bunks, however; nor did bunks compromise kit survivorship or weights at 42 days. Elevated bunks can thus enhance mink mothers’ welfare during the nursing period, seemingly without serious drawbacks for their kits. Unexpectedly, however, all study dams had very high mortality (>20%; more than triple that of non-experimental animals on the farm), suggesting that repeated live observation, or being housed close to barren dams, may elevate risks of nursing sickness.

Soil Phosphorus Effects on Forage Harvested and Nitrogen Fixation on Canadian Organic Dairy Farms

Declining soil‐test phosphorus (STP) levels on eastern Canadian organic dairy farms is a concern because of potential negative impacts on forage growth and biological nitrogen fixation (BNF). This study examined the relationship between STP, forage productivity, and BNF on organic or transitional‐organic dairy farms in Ontario (ON) and Nova Scotia (NS). More than two‐thirds of 28 legume–grass mixed forage fields in the study were low in available P by provincial soil‐test guidelines. Averaged across all fields over 2 yr, forage legume proportion was 46%, forage harvested 5.9 Mg ha–1, BNF 64 kg ha–1, and N harvested 153 kg N ha–1. Forage tissue P concentrations were clearly correlated with STP in the low soil‐test categories (&lt;10 mg Olsen P kg–1 of soil in ON; &lt;30 mg Mehlich‐3 P kg–1 of soil in NS), above which there was little response. Inclusion of soil total P or organic P did not improve the fit of regressions. However, STP explained a very small fraction of variation in forage harvested and BNF. Ninety percent of tissue P concentrations were above 2 g P kg–1 of tissue, a frequently cited critical minimum, and the only apparently P deficient forage crops were on fields that received no manures or fertilizers for more than 5 yr. In the term of this study, low STP was apparently not having a significant impact on forage harvested or BNF on the majority of eastern Canadian organic dairy farms. This result may not apply to seedling‐year forages or other crops.

Short communication: Analysis of health and survival in a population of Ontario Holstein heifer calves

The objective of the present study was to investigate health and survival in heifer calves, from 16 farms in southwestern Ontario. Research technicians visited the farms on a weekly schedule for 16mo, starting in January 2008, and collected blood samples and various measurements to determine the overall health status of the calves. Data of 1,588 Holstein heifer calves from birth until 90 to 120d of age were analyzed. Initially, a survival analysis was carried out to determine which factors surrounding birth increased a calf's risk of mortality. The factors examined were type of birth, calving ease, season of birth, serum total protein, weight during first week of life, treatment status during first week of life, total number of treatments, and bovine respiratory disease status. In general, calves born in fall (October–December), low serum total protein, low weight, and calves treated for illness during the first week of life, increasing number of treatments, and being treated for bovine respiratory disease all increased a calf's risk of mortality. Genetic parameters for requiring treatment for illness, survival, bovine respiratory disease, other diseases, height, and weight were estimated. Heritabilities for treatment, survival, and diseases were low, ranging from 0.04 to 0.07, and were not significant. Moderate and significant heritabilities were found for height (0.33 to 0.45) and weight (0.24 to 0.44). Treatment and survival to 90 to 120d of age were favorably correlated, indicating that calves requiring less treatment have a higher survival rate and vice versa. Further, body weight was found to have a tendency of favorable genetic correlation (−0.22 to −0.53) with treatment for diseases, indicating that calves with higher body weight in their first month of life were genetically more resistant to diseases than those with average body weight. Overall, our results show the potential of using data on calfhood disease and survival in future dairy cattle breeding programs. Further investigation and improved data collection are required to determine the full impact of genetics on health and survival in dairy heifer calves.

Foraging habitat and diet of Song Sparrows (Melospiza melodia) nesting in farmland: a stable isotope approach

Agricultural intensification has been linked to declines in farmland and grassland bird populations in Europe and in North America. One factor thought to be behind these declines is reduced invertebrate food abundance in the breeding season, leading to reduced reproductive success. However, little is known about foraging habitat or diet of farmland birds in North America. We used stable isotopes to study foraging habitat and diet of Song Sparrows ( Melospiza melodia (A. Wilson, 1810)), a common hedgerow-breeding bird, by collecting claw clippings of Song Sparrow nestlings from farms in eastern Ontario, Canada. Mean values of δ13C and δ15N were compared between claws and invertebrate food sources from adjacent land-cover types, using a Bayesian mixing model. The portion of nestling diet that came from seminatural and forage habitats was higher than expected, based on the proportion of seminatural and forage cover at the nest. This was particularly evident at nests with low seminatural cover, where hedgerows were the only noncrop habitat. The most important food sources for Song Sparrow nestlings were hoppers (Auchenorrhyncha) and caterpillars (Lepidoptera). Management actions to increase invertebrate abundance in hedgerows may benefit Song Sparrows and other farmland birds with minimal impact on crop yield.

An economic and functional tool for assessing the financial feasibility of farm-based anaerobic digesters

Anaerobic digester (AD) technology is a form of renewable energy with significant upside potential and little public resistance. However, previous studies have generally found ADs to be a poor investment for private firms without public assistance. The mixed results on the financial feasibility of ADs could be due to the site of the analysis since results vary with size, geographic location or the type of AD system, which are not standardized but rather customized to the individual situation. Given the public and private interest in AD technology and the need to assess the feasibility by site, a decision-making tool that can be adapted for each location and system would aid assessing the investment. This paper presents a freely available workbook to determine the financial feasibility of a farm-based AD and to demonstrate its use. The decision-making tool identifies the technical and financial parameters affecting the returns to an AD and the sensitivity of the assumption to changes in the value of those parameters. An application of the workbook for the Ontario livestock sector demonstrates its usefulness. Investment in an AD is financially feasible only for the largest dairy farms in Ontario under current electricity prices, which are approximately six times greater than the wholesale price. Shifting to a duel fuel continuous system would improve returns, as would the availability of additional substrate material in the form of solid grease and vegetative waste. Reductions in capital cost and improvements in the efficiency of the technology are probable given the relatively infant status of the biogas sector but these future enhancements would likely only alter the investment decisions for large commercial dairy farms.

Characterisation of IgE antibody responses to Anoplocephala perfoliata

Between April 2006 and September 2007, ceco-colic intussusceptions were diagnosed in four standardbred horses aged 1-3 years on a well-managed farm in southern Ontario, Canada. Throughout this period there were approximately 90 standardbred horses maintained on the farm. Surgery on all four horses with ceco-colic intussusceptions revealed the presence of large numbers of Anoplocephala perfoliata in all four animals. Blood samples were collected from all horses on the farm in October 2007 and examined for antibody to a 12/13 kDa A. perfoliata secretory protein [1,2]; 61 of 67 (91%) horses were seropositive and themean optical density (OD) of all horses was 1.391 (median 1⁄4 1.538). Among the seropositive horses, 4 (6% of total) and 57 (85% of total) had OD values indicative of moderate (0.201-0.600) and high (>0.600) infection intensity, respectively. This is in contrast to a 2003-2004 study of 234 horses in southern Ontario of multiple breeds, 117with colic and 117 controls; 131 (56%) were seropositive to A. perfoliata and the mean OD of all horses was 0.509 (median 1⁄4 0.243). Among the seropositives, 65 (27.9% of total) and 66 (28.1% of total) had OD values indicative of moderate and high infection intensity, respectively. Assuming data independence, horses on the standardbred farm were significantly more likely to be seropositive than the 2003-2004 reference population (odds ratio 1⁄4 8.0; 95% CI 1⁄4 3.3-19.6; p < 0.0001). The reason for the high prevalence and high intensity of A. perfoliata infection among horses on the standardbred farm are unclear. In November each year, for multiple years, all yearlings and adult horses on the farm were treated for tapeworms with double-dose pyrantel. In contrast, only 23% of the reference population had received treatment with a cestocide in the year prior to sampling. Since neither underdosing nor use of outdated product appear to have been a concern, it is possible that the problemwas associatedwith resistance to pyrantel in A. perfoliata. However, because of the lack of a sensitive diagnostic method for current infection, this was not possible to prove.

Evaluation of external biosecurity practices on southern Ontario sow farms

External biosecurity protocols, aimed at preventing the introduction of new pathogens to the farm environment, are becoming increasingly important in the swine industry. Although assessments at the individual farm level occur regularly, efforts to cluster swine herds into meaningful biosecurity groups and to summarize this information at the regional level are relatively infrequent. The objectives of this study were: (i) to summarize external biosecurity practices on sow farms in southern Ontario; (ii) to cluster these farms into discrete biosecurity groups and to describe their characteristics, the variables of importance in differentiating between these groups, and their geographic distribution; and (iii) to identify significant predictors of biosecurity group membership. Data were collected using the Production Animal Disease Risk Assessment Program's Survey for the Breeding Herd. A subset of variables pertaining to external biosecurity practices was selected for two-step cluster analysis, which resulted in 3 discrete biosecurity groups. These groups were named by the authors as: (i) high biosecurity herds that were open with respect to replacement animals, (ii) high biosecurity herds that were closed with respect to replacement animals, and (iii) low biosecurity herds. Variables pertaining to trucking practices and the source of replacement animals were the most important in differentiating between these groups. Multinomial logistic regression provided insight into which demographic and neighborhood variables serve as significant predictors of biosecurity group membership (p<0.05). Variables in the final regression model include: herd density within a 4.8km radius, number of sows on the premises, and site production type. The odds of belonging to the high biosecurity group that was open with respect to replacement animals, relative to the low biosecurity group, increased 1.001 times for each additional sow (p=0.001). The odds of belonging to the high biosecurity group that was open with respect to replacement animals, relative to the low biosecurity group, were 6.5 times greater for farms that produced genetic animals than for farms that produced commercial animals (p=0.003). The information obtained through this work allows a better understanding of biosecurity in sow herds at the regional level, and the implementation of biosecurity protocols in North American swine herds in general.

The effects of viral vaccination of dairy heifer calves on the incidence of respiratory disease, mortality, and growth

Bovine respiratory disease (BRD) is one of the most common infectious causes of morbidity and mortality in young dairy cattle. The objective of this randomized clinical trial was to determine the effectiveness of 1 or 2 doses of a 5-way, modified-live viral vaccine, administered to heifer calves before weaning to aid in the prevention of BRD. The hypotheses were that vaccination would reduce the incidence of BRD and mortality, and that 2 doses would be more effective than 1. A total of 2,874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1 to 7d of age and were followed until 3mo of age. Calves were randomly assigned to receive a commercial, intramuscular, modified-live vaccine against bovine viral diarrhea virus types 1 and 2, bovine respiratory syncytial virus, bovine herpesvirus type 1, and parainfluenza virus type 3 at 15 to 21d of age (2wk only), 35 to 42d (5wk only), both 2 and 5wk, or sterile saline at both times (unvaccinated controls). The incidence of failure of passive transfer was 11 or 32%, using cut-points of serum total protein of 5.2 and 5.7g/dL, respectively. Overall, 22% of calves were treated at least once for BRD. The incidence risk of naturally occurring BRD was 7.7% before 2wk of age, 8.0% between 2 and 5wk, and 9.5% between 5wk and 3mo of age, and was not different between vaccination groups. Overall mortality throughout the 3-mo study period was 3.5%. Mortality was 1.6% before 2wk of age, 0.5% between 2 and 5wk, and 1.2% between 5wk and 3mo of age. The risk of mortality was not affected by vaccination. Mean average daily gain of 1.07kg/d from 5wk to 3mo of age was not different between vaccine groups. In this population of commercial, home-raised calves, with an overall low incidence of failure of passive transfer, intramuscular vaccination with a multivalent, modified live viral vaccine at 2 or 5wk of age or both was not associated with a decreased risk of BRD or mortality, or with growth until 3mo of age. Reasons for these findings may include interference by maternal antibodies, unresponsiveness of the neonatal immune system, timing of immunity relative to pathogen exposure, disease caused by pathogens other than the viruses in the vaccine, or herd immunity. However, in populations with higher incidence of failure of passive transfer or risk of BRD, calves with low levels of specific antibodies may respond differently to vaccination.

Glyphosate-resistant giant ragweed (Ambrosia trifida L.) control with preplant herbicides in soybean [Glycine max (L.) Merr.

Vink, J. P., Soltani, N., Robinson, D. E., Tardif, F. J., Lawton, M. B. and Sikkema, P. H. 2012. Glyphosate-resistant giant ragweed ( Ambrosia trifida L.) control with preplant herbicides in soybean [ Glycine max (L.) Merr.]. Can. J. Plant Sci. 92: 913–922. Giant ragweed populations in southwestern Ontario have evolved resistance to glyphosate. Glyphosate-resistant (GR) giant ragweed interference in field crops can lead to significant yield losses. Eleven field trials [five with preplant (PP) burndown only and six with PP burndown plus residual herbicides] were conducted in 2010 and 2011 on Ontario farms with GR giant ragweed to evaluate the efficacy of various PP herbicides applied prior to soybean planting. Glyphosate applied at the recommended field dose failed to adequately control GR giant ragweed. The PP herbicides 2,4-D ester, cloransulam-methyl and saflufenacil applied alone and with glyphosate provided 97–99, 68–100 and 71–94% control, respectively and resulted in soybean yields equivalent to the weed-free check. Combinations of glyphosate plus cloransulam-methyl or linuron controlled GR giant ragweed 8 wk after application (WAA), 75–95 and 95–98%, respectively. Residual control with glyphosate plus linuron resulted in soybean yield equivalent to the weed-free check. Based on these results, GR giant ragweed can be controlled prior to soybean planting in southwestern Ontario.