Changes in antimicrobial resistance of Staphylococcus aureus in bovine quarter milk samples from Southern Germany between 2012 and 2022.

The objective of this study was to describe the in vitro resistance of Staphylococcus (S.) aureus from bovine quarter milk samples obtained by the udder health laboratory of the Bavarian Animal Health Services between 2012 and 2022. All S. aureus samples were tested for ß-lactamase production and only forwarded to further microbroth susceptibility testing either if the ß-lactamase result was positive or upon explicit request by the submitter. The growth of most S. aureus isolates was inhibited at the lowest evaluated minimum inhibitory concentration (MIC) of tested antimicrobials, with the MIC50 and MIC90 mostly beneath the respective breakpoint. On average, about a quarter (24%, n = 5,718) of tested isolates was resistant to erythromycin. However, the prevalence of resistant isolates dropped from 53% (n = 1,018) in 2012 to 8% (n = 113) in 2022. The second highest prevalence of in vitro resistance was to penicillin (17%, of all isolates tested for ß-lactamase production, n = 28,069). Less than 14% of isolates were resistant to the remaining assessed antimicrobial agents (cefoperazone, pirlimycin, kanamycin-cefalexin, marbofloxacin, amoxicillin-clavulanate, cefquinome, or cefazolin, respectively). Over the years, 4% (n = 959) of the S. aureus isolates selected for microbroth susceptibility testing (and 0.8% (n = 1,392) of all submitted S. aureus isolates) were methicillin-resistant S. aureus (MRSA), and 5% (n = 1,162) of S. aureus isolates were multidrug-resistant. However, there was an overall trend toward fewer resistant isolates. These findings are consistent with those of several European monitoring programs that reported a slight decrease of AMR of bovine S. aureus in countries where antibiotic use in veterinary medicine was reduced. Notably, isolates of clinical mastitis cases were consistently less likely to express in vitro resistance than isolates obtained from milk of healthy cows or subclinical mastitis cases. In conclusion, antimicrobial resistance (AMR) of S. aureus was decreasing and penicillin should remain the first-choice antimicrobial in the attempt of treating S. aureus intramammary infections in Bavaria.

Apparent prevalence and risk factors for udder skin diseases and udder edema in Bavarian dairy herds.

The objective of this cross-sectional study was to assess the prevalence and risk factors for teat warts, udder edema, udder thigh dermatitis, and udder cleft dermatitis on Bavarian dairy farms. Udder health and hygiene scores of lactating cows were recorded on 152 farms in Bavaria, Germany. Management practices (e.g., housing, milking systems, and feeding regimens) were assessed with a comprehensive questionnaire. Adjusted prevalence estimates were determined using regression analysis with herd as the random effect. Mann-Whitney U or Fisher's exact on herd level and regression analyses on cow level were performed to determine risk factors. Of the 6,208 cows examined, 4.0% had teat warts, 1.1% udder edema, 0.2% udder thigh dermatitis, and 0.3% udder cleft dermatitis. The apparent median within-herd prevalence was less than 4% for all 4 diseases. Herd-level factors that were associated with the presence of teat warts on a farm were the proportion of cows with poor teat ends as well as conventional milking systems compared with milking robots. At a cow level, teat warts were associated with high somatic cell counts. Herds with poor depth (<5 cm) of bedding material and cows with days in milk less than 60 d had increased odds for udder edema. First-lactating cows had higher odds for udder thigh dermatitis. Freestall housing and comfort rubber mats were identified as risk factors for udder cleft dermatitis on a herd level. In conclusion, although most nonmastitis udder diseases were rarely observed in this study, some herd management practices and cow factors were associated with their presence on a farm or cow level. Future studies are needed to further investigate risk factors for each disease in more detail.

Efficacy of non-antibiotic treatment options for digital dermatitis on an organic dairy farm.

The objective of this study was to evaluate the efficacy of two non-antibiotic treatment options for digital dermatitis (DD) on an organic certified dairy farm. A randomized clinical trial was conducted using 70 multiparous Holstein cows with an early DD lesion at a USDA certified organic dairy farm in Northern Colorado, USA. Cows were enrolled in the study based on the presence of early DD lesions (scores M1 and M2) and randomly assigned to one of three treatments: (1) topical application of copper sulfate and iodine (CUI); (2) topical application of honey and iodine (HOI); and (3) control subject to no treatment (CON). Cows were evaluated at enrolment and on days 3, 12, 28, and 120 post treatment for pain and lesion size and received a locomotion and a lesion score. Cure was defined as the transition from active to non-active stages (M1/M2 to M0 or M4). The formulations had variable effects on the treatment of DD. The cure rate was numerically higher for CUI on all follow up days. The proportion of cows experiencing pain on d3 after treatment was greater in CON, followed by HOI and CUI. However, this proportion increased in HOI during the follow up period. The CUI group had a greater reduction in lesion size and larger lesions persisted in HOI. Non-antibiotic treatment formulations were partially effective in the treatment of DD in organic dairy cows: The two non-antibiotic formulations resulted in an earlier transition to mature lesions compared with the control group. The CUI combination was the most effective treatment in reducing lesion size, pain, and lameness in affected cows. However, this combination had short-term efficacy, which did not persist throughout the duration of the study. The HOI combination produced only transient reduction in lesion size.

Short communication: Effects of mesh leggings on fly pressure and fly avoidance behaviors of pastured dairy cows.

Ectoparasitic stable flies (Stomoxys calcitrans [L.]), horn flies (Haematobia irritans [L.]), and face flies (Musca autumnalis De Geer) negatively affect dry matter intake, milk production, and health of pastured dairy cows. These flies cause fly avoidance behaviors and are a major welfare concern for dairy producers. The objective of this study was to evaluate the effects of mesh Shoofly Leggins (Stone Manufacturing & Supply, Kansas City, MO) on fly avoidance behaviors and numbers of flies attacking pastured dairy cows. In a crossover design, lactating dairy cows (n = 80) were randomly assigned to groups with and without leggings (Shoofly Leggins worn on all legs). All cows were managed in one group. Cows were observed for 2-wk periods, and then treatments were reversed in the next 2-wk interval. Counts of stable flies, horn flies, and face flies on all cows were recorded twice daily (once in morning per cow: 0930 to 1230 h; and once in the afternoon per cow: 1330 to 1630 h), 3 times per wk on Tuesday, Wednesday, and Thursday of each week during the study period. The total number of flies per cow was greater on cows with leggings than cows without leggings. The number of horn flies per cow was greater on cows in with leggings (26.4 flies/side) compared with cows without leggings (24.1 flies/side). Stable fly numbers were similar for cows with and without leggings (12.8 flies/leg). A random subset of 20 focal cows per group was observed during 5-min intervals to record frequencies of 4 behaviors: leg stomps, head tosses, skin twitches, and tail swishes. Counts of head tosses (2.6 vs. 3.1), skin twitches (20.9 vs. 19.6), and tail swishes (21.3 vs. 19.3) were similar for cows without leggings versus cows with leggings, respectively. However, foot stomps were 39% lower for cows with leggings compared with cows without leggings, and leg stomps were 26% higher in the afternoon than in the morning (2.9 vs. 2.4, respectively). A positive correlation was observed between stable and horn flies and all insect avoidance behaviors. Numbers of stable flies were 1.5 times greater in the afternoon than in the morning. The results of this study indicated that flies were associated with cow fly avoidance behaviors regardless of the use of leggings, but leggings effectively reduced foot stomps by 39%, so their use may provide some relief from stable fly injury to pastured dairy cows.

Effects of winter housing system on hygiene, udder health, frostbite, and rumination of dairy cows.

The objective of this study was to evaluate the effects of 2 winter (December to April) housing systems on dairy cow hygiene scores, frostbite, teat condition, clinical mastitis, and activity and rumination across 3 winter seasons (2013, 2014, and 2015). Certified-organic cows (n = 268) were randomly assigned to 2 treatments (2 replicates per system): (1) outdoor straw pack (outdoor) or (2) 3-sided compost-bedded pack barn (indoor). Cows calved during 2 seasons (spring or fall) at the University of Minnesota West Central Research and Outreach Center, Morris, Minnesota, organic dairy. Organic wheat straw was used as bedding for the 2 outdoor straw packs, and bedding was maintained by farm management to keep cows dry and absorb manure throughout the winter. The compost-bedded pack barn (2 pens in the barn) was bedded with organic-approved sawdust, and the bedding material was stirred twice per day with a small chisel plow. Hygiene scores were recorded biweekly as cows exited the milking parlor. Incidence of clinical mastitis was recorded in a binary manner as treated (1) or not treated (0) at least once during a lactation. Frostbite incidence was collected monthly. Activity and rumination times (daily and 2-h periods) were monitored electronically using a neck collar sensor (HR-LD Tags, SCR Dairy, Netanya, Israel). Indoor cows had greater udder hygiene scores (1.75 vs. 1.46) and greater abdomen hygiene scores (1.79 vs. 1.43) compared with outdoor cows. Additionally, the indoor cows had greater upper and lower leg hygiene scores compared with outdoor cows. Incidence of clinical mastitis was greater for indoor cows compared with outdoor cows (27.1% vs. 15.1%, respectively). Frostbite incidence was not different between indoor (30.1%) and outdoor (17.5%) cows. Daily rumination was 509 min/d for indoor cows and 530 min/d for the outdoor cows. In summary, lactating cows housed outdoors on straw-bedded packs had cleaner udders and improved udder health compared with cows housed in a compost-bedded pack barn.

Effects of winter housing systems on production, economics, body weight, body condition score, and bedding cultures for organic dairy cows.

Certified-organic dairy cows (n = 268) were used to evaluate the effect of 2 winter (December to April) housing systems on milk production, somatic cell score (SCS), body weight, body condition score (BCS), and economics across 3 winter seasons (2013, 2014, and 2015). Bedding cultures from the housing systems were also evaluated. Cows were randomly assigned to 2 treatments (2 replicates per group): (1) outdoor (straw pack, n = 140) or (2) indoor (3-sided compost bedded pack barn, n = 128). Cows calved during 2 seasons (spring or fall) at the University of Minnesota West Central Research and Outreach Center, Morris, Minnesota, organic dairy. Milk, fat, and protein production and SCS were recorded from monthly milk recording. Body weight and BCS were recorded biweekly as cows exited the milking parlor. Bedding cultures from the housing systems were collected biweekly. Costs for key inputs and the price received for milk production were recorded for the study period and averaged for use in the profitability analysis. Energy-corrected milk and SCS were not different for the outdoor (15.1 kg/d, 2.64) and indoor (15.7 kg/d, 2.57) housing systems, respectively. In addition, cows in the outdoor and indoor housing systems were not different for body weight (528 vs. 534 kg) and BCS (3.22 vs. 3.23), respectively. Daily dry matter intake was 19.1 kg/d for the outdoor cows and 19.6 kg/d for indoor cows. The total bacteria count from bedding samples tended to be lower in the outdoor (13.0 log10 cfu/mL) compared with the indoor (14.9 log10 cfu/mL) system. Milk revenue and feed cost were not different for the 2 housing systems. Labor and bedding costs were lower and net return was higher for the outdoor housing system. The outdoor straw pack system had a $1.42/cow per day net return advantage over the indoor compost bedded pack barn. In summary, lactating cows housed outdoors on straw-bedded packs did not differ for production or SCS, or for body weight, BCS, or dry matter intake, but had greater profitability than cows housed in an indoor compost bedded pack barn.

Short communication: Iodine concentrations in serum, milk, and tears after feeding Ascophyllum nodosum to dairy cows-A pilot study.

Kelp (Ascophyllum nodosum) is rich in iodine and often fed by organic dairy producers as a mineral supplement to support animal health. A commonly held belief is that kelp supplementation decreases susceptibility to infectious bovine keratoconjunctivitis due to increased iodine concentrations in tears. Whereas serum and milk iodine concentrations are positively correlated and modulated by oral iodine supplementation, nothing is known about the iodine concentration of tears. Therefore, the 3 objectives of this pilot study were to determine (1) the iodine content of tears, milk, and serum of cows after being fed kelp for 30d; (2) the trace mineral and thyroid status of cows before (d 0) and after being fed kelp for 30d; and (3) the in vitro growth rate of bacteria in tears (Moraxella bovis) or milk (Staphylococcus aureus, Escherichia coli, Streptococcus uberis) collected from cows fed no kelp (d 0) or kelp (d 30). Cows (n=3/treatment) were individually fed 56g of kelp per day (n=3/treatment) or not (n=3/no treatment) for 30 d. Daily feed intake of the TMR was recorded and weekly TMR, kelp, milk, blood and tear samples were collected and analyzed for iodine. The feed samples were pooled and further analyzed for other minerals. On d 0 and 30, liver biopsies and blood samples were collected and analyzed for mineral content and thyroid hormone concentrations, respectively. An inhibition test used milk and tear-soaked plates from kelp-fed cows (d 0 and 30) as well as 1 and 7.5% iodine as positive and distilled water as negative control. As expected, serum iodine concentrations were positively correlated with milk and tear iodine concentrations. Whereas the iodine concentrations in serum increased significantly in the kelp-fed cows during the 30-d study, milk and tear iodine concentrations increased only numerically in these cows compared with the control group. Liver mineral profiles were comparable between groups and generally did not change over the course of the study. Thyroid hormones remained overall within the reference range throughout the trial. Neither milk nor tears from kelp-fed cows inhibited in vitro growth of any of the plated bacteria. In summary, serum iodine concentration was correlated with the iodine concentration in milk and tears and feeding kelp increased only the serum iodine levels of cows in this trial. Bacterial growth was not inhibited in milk and tears of kelp-fed cattle in vitro, and prevention of infectious bovine keratoconjunctivitis would not be based solely on increased iodine concentrations in tears.

Management practices on organic and conventional dairy herds in Minnesota.

The objective of this study was to describe and compare husbandry practices on organic and conventional dairy farms of similar sizes in Minnesota. Organic (ORG, n=35), same-sized conventional (SC, n=15, <200 cows) and medium-sized conventional (MC, n=13, ≥200 cows) dairy herds were visited in 2012, and farmers were interviewed once about their farm, herd demographics, and herd management practices concerning nutrition, housing, and reproductive programs. Organic farms had been established as long as conventional farms, and ORG producers had most commonly selected ORG farming because of a negative perception of pesticides for human health. The distribution of cattle breeds and ages differed across farm types. Organic farms had more crossbred cows and a greater number of older cows than conventional farms, who had mainly Holstein cattle. Organic farms did not dock tails, were more likely to use breeding bulls, and were less likely to conduct pregnancy diagnoses in cattle. All conventional farmers fed corn, corn silage, and hay, but no forage or feed supplement was fed by all ORG farms with the exception of pasture. Kelp was supplemented on most ORG farms but on none of the conventional farms. In summary, although there were differences across farm types regarding the use of pasture, feeds, and feed additives, breed and age distribution, reproductive management, and the use of tail docking, observations in other management areas showed large overlap across herd types.

Parasites and parasite management practices of organic and conventional dairy herds in Minnesota.

The objective of this study was to describe the prevalence and practices used to manage internal helminth parasites and external arthropod parasites on organic and conventional dairy herds in Minnesota. All organic (ORG) dairy herds in Minnesota (n=114) and a convenience sample of conventional herds were invited to participate in the study. Thirty-five ORG herds and 28 conventional herds were visited once in summer and fall of 2012. Conventional dairy herds were split into small conventional (SC,<200 cows) and medium-sized conventional herds (MC, ≥200 cows) so that SC herds were comparable in size to the ORG herds. Dairy managers were surveyed to assess their farm management practices and perceptions about parasites, hygiene scores were recorded for adult stock, and fecal samples were collected from a nominal 20 breeding-age heifers to characterize abundance of internal parasites. Nonparametric tests were used to compare fecal egg counts per gram (FEC) among farms grouped by management systems and practices. Organic farms had more designated pasture and were more likely to use rotational grazing compared with conventional farms, but the stocking densities of animals on pasture were similar among farm types. The overall FEC were very low, and only a few individual ORG heifers had FEC >500 eggs/gram. Samples from heifers on ORG farms had significantly more strongyle-type eggs than those on SC and MC farms (ORG: 6.6±2.1; SC: 0.5±0.3; MC: 0.8±0.7), but egg counts of other types of gastrointestinal parasites did not differ significantly among the 3 herd groups. Fly control measures were applied mainly to milking cows and preweaned calves and were used on 88.6% of ORG herds, 60.0% of SC herds, and 91.7% of MC herds. Approximately half of the producers reported having seen skin conditions suggestive of lice or tail mange in their cattle during the previous winter (ORG: 48.6%, SC: 57.1%, MC: 53.9%). Although most conventional producers reported treating these skin conditions, most organic producers stated they had not treated them. In conclusion, gastrointestinal parasite egg counts were low overall at the time of the survey, and most surveyed producers did not perceive gastrointestinal parasites to be a problem for their animals' health. Independent of the herd type, fly control was mostly targeted at the lactating herd and preweaned calves.

Perception of the importance of human-animal interactions on cattle flow and worker safety on Minnesota dairy farms.

Proper cattle-handling techniques (stockmanship) are important to ensure calm animals and a safe work environment for dairy workers on farm. The objectives of this study were to (1) assess Minnesota dairy herd owners' attitudes toward stockmanship, its perceived importance for cow comfort and worker health, and the establishment of calm cattle movement; and (2) identify current resources and methods of stockmanship training on Minnesota dairy farms. A stratified-random sample of Minnesota dairy farmers were contacted via mail to participate in a 28-question survey. One hundred eight bovine dairy producers participated. Most commonly, respondents learned their cattle handling skills from family members (42.6%) and 29.9% of producers had participated in previous stockmanship training. Producers thought that the skill of the human handler was the most important factor in establishing good cattle flow. Cattle-handling techniques was the third most common topic for new-employee orientation after training in milking parlor protocols and milking parlor disinfection. Time limitations and language barrier were considered serious challenges for worker training. Work-related injuries were responsible for lost work days in the previous year in 13.3% of dairy herds and 73.3% of those injuries occurred while working with cattle. Producers perceived that cattle-related injuries were predominantly the handler's fault: either because of not paying enough attention to the animal or due to poor cattle handling skills. Facility design was considered the least important for the occurrence of worker injuries. Although no causal inference can be made, herds that had workers who had previously participated in stockmanship training had a 810 ± 378 kg (mean ± standard error of the mean) higher rolling herd average than those that did not, even after adjusting for herd size and bulk tank somatic cell count. However, 50% of respondents were not interested in attending future stockmanship training sessions. In conclusion, cattle handling skills are considered important by Minnesota dairy producers to ensure worker safety and cow flow. Limited availability of time, language barrier, and a perceived lack of training materials were considered challenges during the training of workers on farms.

Cow-level association between serum 25-hydroxyvitamin D concentration and Mycobacterium avium subspecies paratuberculosis antibody seropositivity: a pilot study.

Vitamin D deficiency has been associated with various human diseases. Therefore, the objective of this study was to evaluate the cow-level association between serum 25-hydroxyvitamin D [25(OH)D] concentration and Mycobacterium avium ssp. paratuberculosis (MAP) seropositivity of dairy cows, adjusting for diet, breed, hair coat color, stage of lactation, reproductive status, and cow age. The sera of 80 MAP antibody ELISA-positive and 80 test-negative herd mates from 5 Minnesota dairy herds were analyzed for 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. The cows' age, production records, and hair coat color were recorded. Additionally, feed samples were obtained and analyzed for vitamin D(2) and vitamin D(3) content. A linear mixed model was used to identify potential predictors for serum 25(OH)D concentration, accounting for herd of origin. The majority of rations analyzed had over 22,000 IU of vitamin D/day (maximum: 52,000 I U/d) and the study cows' average serum 25(OH)D concentration was 62.5 ± 13.8 ng/mL. Serum ELISA-positive cows had, on average, 5.3 ng/mL lower 25(OH)D serum levels than test-negative herd mates. The reproductive status of cows was also associated with the 25(OH)D levels, with fresh cows having the lowest serum concentration. In this cross-sectional study, a temporal or causal association between MAP antibody ELISA status and serum 25(OH)D concentration could not be evaluated. In addition, the high levels of vitamin D in the rations of participating farms and the average 25(OH)D serum concentration suggest that additional supplementation with vitamin D in the ration is likely to be ineffective.

Short communication: Milk ELISA status for bovine leukosis virus infection is not associated with milk production in dairy cows.

The objective of this study was to assess whether the milk ELISA status for antibodies against bovine leukemia virus was associated with 305-d milk production in Canadian dairy cattle. Test results and test-day production data from 19,785 dairy cows were available for analysis. A linear mixed model was used with the estimated 305-d milk production as the outcome and lactation number, somatic cell count, calving season, days in milk, and breed as fixed effects. Herd nested in province was included as random effect. In conclusion, bovine leukemia virus antibody milk ELISA status was not associated with milk production.

Changes in management practices and apparent prevalence on Canadian dairy farms participating in a voluntary risk assessment-based Johne's disease control program.

The objectives of this study were (1) to describe the change in Mycobacterium avium ssp. paratuberculosis (MAP) antibody milk ELISA-positive prevalence in Canadian dairy herds that participated in a risk assessment (RA)-based Johne's disease (JD) control program; (2) to describe the distribution of so-called high-risk management practices on Canadian dairy farms; and (3) to assess if compliance with selected recommendations translated into changes in the scores of associated RA questions. In Ontario and western Canada, 226 herds voluntarily participated in a RA-based JD control program for several years. In 2005-2007, a previsit survey, RA, and MAP-antibody milk ELISA of the entire milking herd were conducted. Therefore, the interpretation of the results of this study is strictly for the MAP-antibody milk ELISA status of cows or herds, because no culture of MAP (of fecal or environmental samples) was conducted due to economic restrictions. In early 2008, a telephone interview was used to determine compliance with recommended management changes after the first RA. In 2008-2009, a second RA and another whole-herd MAP antibody milk ELISA were performed. At both herd tests, about 35% of the farms had at least one MAP-antibody milk ELISA-positive cow, classifying them as a MAP-antibody milk ELISA-positive herd. However, 28.8% of herds had changed their MAP-antibody milk ELISA status between the 2 tests, demonstrating that a single herd test was insufficient to determine the long-term MAP-antibody ELISA status of a herd. The average within-herd MAP-antibody milk ELISA-positive prevalence changed from 5.4 to 4.2% over the study period, but management practices did not change much throughout the 2- to 3-yr period and were similar to those reported in other parts of North America. The overall RA scores decreased at the second RA, in particular for management practices in the calving and preweaned calf area, and when herds were test-positive at the first test. This was not surprising, because many of the recommendations at the first RA focused on these management areas and compliance with some recommended farm-specific management practices in this area might be linked to reduced scores for associated RA questions. In conclusion, the participating farms did, on average, decrease their within-herd MAP-antibody milk ELISA positive-prevalence and RA total scores. Changes in RA scores could be linked to improved management practices, indicating that the RA questions appropriately reflected management practices. Some herds changed their MAP-antibody milk ELISA status between tests, which underlines that a current test of the entire milking herd is necessary to determine the present MAP-antibody milk ELISA status of a dairy herd.

Associations between paratuberculosis milk ELISA result, milk production, and breed in Canadian dairy cows.

The 3 objectives of this study were (1) to quantify milk production differences among cows with different paratuberculosis (ParaTB) milk ELISA results; (2) to determine if production differences existed in lactations preceding the test among cows with different ParaTB milk ELISA results; and (3) to assess whether Channel Island breeds were more likely to test positive with the ParaTB milk ELISA than other dairy breeds. Current and completed lactation records from 35,591 dairy cows in Ontario and western Canada that had been tested with a commercial ParaTB milk ELISA were included in the analysis. The first occurrence of the highest categorical test result was used to classify the cow. Cows were then grouped by the lactation in which the first high-positive (HTP), low-positive, or negative milk ELISA occurred, and comparisons were made within lactation groups. High test-positive cows were defined as those that had an optical density ≥ 1.0 on at least 1 ParaTB milk ELISA. The associations between ParaTB milk ELISA status and milk production, as measured by the 305-d milk yield, were assessed with a series of linear mixed models. The effect of breed on the likelihood of testing positive with the milk ELISA was assessed using a logistic mixed model for the lactation in which the first negative or positive ParaTB milk ELISA occurred. Test-positive cows produced on average 2.9 to 6.8% less milk than negative herdmates in the lactation in which they were tested. The HTP cows produced on average 466, 514, and 598 kg less milk than low-positive herdmates in lactations 1, 2, and 4, respectively. Cows testing low-positive in their second lactation had, on average, a 218-kg higher milk yield in their first lactation than their test-negative herdmates. Otherwise, no association was found between test result and milk production in preceding lactations. Differences in milk production among negative, test-positive, and HTP cows increased with increasing parity. Cows of the Channel Island breeds had 1.4 to 8.3 times the odds to test positive compared with other dairy breeds. The findings of this study are consistent with previous studies that have reported that milk production is lower in test-positive animals. The differences in milk production increased with increasing ELISA optical density scores and parity in which the animal tested positive. However, with the exception of second-lactation cows, no differences in milk production were observed in tests preceding lactations. The differences in milk ELISA status among dairy breeds support the need for further studies investigating the genetic component of ParaTB susceptibility.

Prepartal concentration of estradiol-17beta in heifers with stillborn calves.

This study was conducted to investigate hormonal imbalances preceding stillbirths and dystocia in primiparous heifers. The study was conducted between 2003 and 2004 on a German dairy farm, including 433 heifers. Starting 3 wk before calving, a weekly blood sample was collected. At calving, another blood sample was obtained, and the calving ease (grade 0 = unassisted to grade 2 = heavy pull with mechanical calf puller), sex, birth weight, as well as vitality status (stillborn, alive) of the calf were recorded. The blood serum was analyzed for estradiol-17beta and progesterone concentration. At parturition, the measured estradiol-17beta concentration was greater in heifers delivering bulls than in those with female calves and was increasing with greater birth weight of the calf and increasing calving difficulty score. Already 2 wk before calving, the serum estradiol-17beta concentration was significantly smaller in heifers with stillborn than live calves. On the other hand, the progesterone concentration was greater 2 wk before calving in heifers with stillborn calves, but it was unaffected by the birth weight or sex of the calf or the calving difficulty score. Stillborn and live calves did not differ in birth weight or pregnancy duration. The smaller estradiol-17beta concentrations of the heifers with stillborn calves could indicate an abnormality of the placenta or an abnormality of hormonal signals from the calf to the placenta in the weeks before the calving.

Evaluation of the Dairy Comp 305 module "Cow Value" in two Ontario dairy herds.

The study was conducted to evaluate how the "Cow Value" module of Dairy Comp 305 (Valley Agricultural Software, Tulare, CA) performed under commercial conditions. The "Cow Value" module, COWVAL, computes a farm-specific net present value relative to an average replacement heifer for each cow in the milking and dry herd, which allows a ranking of the cows on the farm compared with replacing her with a typical replacement heifer on that farm. The average replacement heifer is used as the baseline for comparison and has a COWVAL of $0. Retaining a cow with a negative COWVAL is projected to be less profitable than replacing that cow with a new heifer. The objectives of the study were to explore trends in COWVAL over and during multiple lactations for the same cows; to describe factors that influence changes in COWVAL from one monthly Dairy Herd Improvement test to the next; and to evaluate the behavior of COWVAL after it drops below a baseline of $0 during the lifetime of a cow. Monthly Dairy Comp 305 backup cow files from 2 On-tario dairy herds between December 1999 and Decem-ber 2005 were used to generate COWVAL and list production, reproduction, and disease data for the milking cows. In total, 1,463 cows and 20,071 tests were analyzed. Within the first 60 d in milk (DIM), COWVAL was unstable and showed large fluctuations over a range of several thousand Canadian dollars (Can$). After 60 DIM COWVAL was relatively stable. The variability from month to month became less as the lactation progressed and the risk of a change in reproductive status decreased. The reproductive status of the cow influ-enced COWVAL: fresh, open, and pregnant cows had a greater COWVAL than cows declared "do not breed." As parity increased, there was a tendency toward lower COWVAL and smaller monthly changes in COWVAL. The COWVAL of 170 cows dropped below the baseline of $0 after 60 DIM. The COWVAL of 54% of those cows remained below $0, whereas 31.6% had a subsequent COWVAL > $500 (Can$). Farm management should not rely exclusively on COWVAL for culling decisions, particularly for cows that have not had at least 3 milk tests.