Defining risk for low reticuloruminal pH during the diet transition period in a commercial feedlot in western Canada.

The objective of the current study was to measure reticuloruminal pH in cattle in a commercial feedlot setting to determine the incidence and extent of low reticuloruminal pH for steers and heifers as they transition to a high-concentrate finishing diet. Reticuloruminal pH was measured in 16 "mixed breed" steers (4 steers/pen with 4 pens) and 16 "mixed breed" heifers (4 heifers/pen with 4 pens) housed in commercial feedlot pens, with 227 ± 13 and 249 ± 6 cattle/pen cohort steers and heifers, respectively, for the diet transition period. Cattle were transitioned from a diet of 53.5% forage and 46.5% concentrate to a diet of 9.5% forage and 90.5% concentrate on a DM basis using a 40-d transition with 5 dietary steps with the diets containing 41.4, 44.8, 49.8, 52.5, 55.1, and 64.0% nonfibrous carbohydrate. In addition, wheat replaced barley as the grain source during the dietary transition. Reticuloruminal pH was measured using orally administered pH measurement devices that were retrieved at slaughter. Data were analyzed using a mixed model including the fixed effects of sex, diet, and the 2-way interaction to evaluate the effect of diet and sex and with the fixed effects of sex, diet, and day relative to each dietary change along with the 2- and 3-way interactions to evaluate temporal responses as a result of diet change. A repeated measures statement was included for the effect of day. Both the mean and minimum reticuloruminal pH values decreased as the proportion of concentrate in the diet increased ( < 0.001). The area and duration that pH was <5.6 increased with greater inclusion of concentrate in the diet ( < 0.001). The number of cattle experiencing low reticuloruminal pH, defined as pH < 5.6 for >180 min, increased with increasing concentrate, and by the end of the 40-d dietary transition, 83% of the cattle had experienced at least 1 bout of low reticuloruminal pH, with most experiencing between 1 and 3 bouts/diet. These data are interpreted to suggest that cattle are at high risk for experiencing low reticuloruminal pH during the dietary transition but that the extent of low reticuloruminal pH is mild. Moreover, the data suggest that the risk for low reticuloruminal pH increases with increasing proportion of concentrate in the diet. The results also suggest that susceptibility to low reticuloruminal pH may differ between steers and heifers.

Effect of dietary energy substrate and days on feed on apparent total tract digestibility, ruminal short-chain fatty acid absorption, acetate and glucose clearance, and insulin responsiveness in finishing feedlot cattle.

The objective of this study was to determine the effect of dietary energy substrate and days on feed on apparent total tract digestibility, ruminal fermentation, short-chain fatty acid (SCFA) absorption, plasma glucose and acetate clearance rates, and insulin responsiveness. Eight ruminally cannulated, crossbred growing heifers were randomly allocated to 1 of 2 dietary treatments. The control (CON) diet consisted of 75.2% barley grain, 9.8% canola meal, 9% mineral and vitamin supplement, and 6% barley silage (DM basis). To evaluate the effect of energy source, a high-lipid, high-fiber byproduct pellet (HLHFP) was included in the diet by replacing 55% of the barley grain and 100% of canola meal. The study consisted of 4 consecutive 40-d periods (P1 to P4), with data and sample collection occurring in the last 12 d of each period. Dry matter intake tended ( = 0.10) to decrease by period and HLHFP-fed heifers tended to eat less ( = 0.09). The ADG of the CON was greater than that of the HLHFP during P1 and P4 (treatment × period, = 0.02). Heifers fed HLHFP tended to have greater mean ruminal pH (6.10 vs. 5.96; = 0.07) than heifers fed the CON, but pH was not affected by period. The CON heifers had a greater digestibility for DM, OM, CP, and NDF ( ≤ 0.03), and the digestibility for DM and OM linearly increased ( = 0.01) and for CP, NDF, and starch quadratically increased ( ≤ 0.04) with advancing period. Total SCFA concentration in the rumen was greater ( < 0.01) for the CON than for the HLHFP (141.6 vs. 128.1 m). The molar proportion of acetate and isobutyrate linearly increased and butyrate and valerate linearly decreased ( ≤ 0.05) with advancing periods. The rate of valerate absorption tended to increase (linear, = 0.06) and the ruminal liquid passage rate tended to decrease (linear, = 0.08) with advancing period. The arterial clearance rate of acetate tended to quadratically increase ( = 0.06) with period, whereas the clearance rate of glucose was not affected by treatment or period. Both fasting plasma insulin and the area under the insulin curve in response to glucose infusion linearly increased ( = 0.04) with period. These data suggest that partially replacing barley grain with HLHFP negatively affects total tract digestibility and performance. Moreover, with advancing days on feed, digestibility and insulin resistance increases without changes in ruminal pH and plasma metabolite clearance rates.

Effect of repeated through-and-through joint lavage on serum amyloid A in synovial fluid from healthy horses.

The objective of this study was to evaluate the effect of through-and-through joint lavage on systemic and synovial serum amyloid A (SAA), total protein, nucleated cell count and percentage of neutrophils in the synovial fluid of six healthy horses. A prospective experimental study was performed where one healthy tarsocrural joint of each horse was randomly assigned to receive repeated through-and-through joint lavage at 0, 48 and 96 h. Synovial fluid and blood samples were collected at 0 (baseline), 24, 48, 72, 96 and 120 h. Systemic and synovial SAA, total protein, nucleated cell count and percentage of neutrophils were measured and compared to baseline. Concentrations of systemic and synovial SAA percentage of neutrophils were not increased from baseline in contrast to total protein and nucleated cell counts (except for nucleated cell count at 96 h). In conclusion, repeated through-and-through joint lavage did not affect synovial SAA concentrations in horses; however, synovial total protein and nucleated cell count values increased. Some of the total protein and nucleated cell count values observed in this study were within the range reported for septic arthritis 24 h after joint lavage. Hence, synovial SAA may be a valuable marker to evaluate the clinical progression of septic joints after through-and-through joint lavage. Clinical studies evaluating synovial fluid SAA concentrations while treating synovial sepsis with through-and-through joint lavage are warranted.

Interaction of vitamin A supplementation level with ADH1C genotype on intramuscular fat in beef steers.

Previously, the single nucleotide polymorphism in alcohol dehydrogenase (ADH1C c.-64T>C) was shown to have an association with intramuscular fat (IMF) in the longissimus thoracis (LT) muscle when vitamin A was limited in finishing rations of beef steers. The purpose of this study was to determine the optimum vitamin A supplementation level, in combination with ADH1C genotype, to increase IMF of the LT muscle. In total, 45 TT genotype, 45 CT and 27 CC Black Angus crossbred steers were backgrounded on a commercial ration containing 3360 IU vitamin A/kg dry matter (DM). During finishing, the steers were randomly assigned to one of three vitamin A treatments at 25%, 50% and 75% of the National Research Council recommendation of 2200 IU/kg DM. Treatments were administered via an oral bolus. Carcass quality was evaluated and a sample from the LT muscle was collected for analysis of IMF. A treatment×genotype interaction (P=0.04) was observed for IMF; TT steers on the 75% treatment had higher IMF relative to CT and CC steers on the same treatment. Western blot analysis showed that TT steers had higher (P=0.02) ADH1C protein expression in hepatic tissue. Previously, TT steers exhibited increased IMF when fed limited vitamin A. In the current study, the lack of variation in IMF between treatments and genotypes at the lower vitamin A treatment levels was likely due to the majority of the steers grading Canada AAA (USDA Choice). However, the western blot data supports that TT steers are expected to have higher IMF deposition, due to an increased production of ADH1C. The interaction between ADH1C genotype and vitamin A supplementation level has the potential for use in marker-assisted management programs to target niche markets based on increased marbling.

Prognostic value of histologic grading for feline mammary carcinoma: a retrospective survival analysis.

Feline mammary carcinoma is highly malignant and generally associated with a poor prognosis, although studies suggest the range of survival times in affected cats is broad. Histologic grading of these tumors is achieved using the Elston and Ellis system, originally developed for human breast cancer. In cats, however, classification using this method has variable prognostic value. Therefore, objectives of this study were (1) to evaluate the Elston and Ellis grading system for feline mammary carcinoma in a predominantly spayed population and (2) to determine whether modification of this system or development of a novel system improved the prognostic value of histologic grading. Survey data and histologic features for 108 carcinomas from 97 cats were analyzed with respect to overall survival. Elston and Ellis grading failed to correlate significantly with overall survival. Using multivariable analysis, lymphovascular invasion, nuclear form, and mitotic count each demonstrated independent prognostic significance (P = .008, <.001, and .004, respectively). Modifications of the Elston and Ellis system and a novel grading system were proposed based on these results; all showed significant correlation with overall survival (P < .001). Median survival times were 27, 29, or 31 months for grade I; 14, 12, or 14 months for grade II; and 13, 5, or 8 months for grade III carcinomas using the mitotic-modified Elston and Ellis, the revised Elston and Ellis, or the novel grading system, respectively. Based on this retrospective study, adoption of the species-specific systems as proposed here may improve the prognostic value of histologic grading for feline mammary carcinoma.

Effect of tibial plateau levelling osteotomy on patellar tendon angle: a prospective clinical study.

OBJECTIVE: To evaluate the effect of the tibial plateau levelling osteotomy (TPLO) procedure on the patellar tendon angle (PTA) in dogs with naturally occurring cranial cruciate ligament rupture. STUDY DESIGN: Prospective observational clinical study. ANIMALS: Dogs with naturally occurring CrCL rupture that had a TPLO performed (n = 40). METHODS: Preoperative tibial plateau angle (TPA) and PTA were measured on radiographic images of affected stifle joints at 90° and standing angle (135°) respectively. The TPA and PTA were measured after TPLO was performed. Regression analysis was performed to evaluate the effect of preoperative TPA and PTA and postoperative TPA on postoperative PTA. Linear regression analysis was performed to evaluate the correlation between postoperative TPA and PTA. RESULTS: The mean (± SD) preoperative TPA and PTA were 26.5 ± 3.8° and 105.7 ± 3.8° respectively. The postoperative TPA and PTA values were 7.6 ± 3.3° and 91.4 ± 5.5°, respectively. Regression analysis showed that higher preoperative PTA and postoperative TPA are associated with a larger difference between the postoperative PTA and 90°. There was a positive correlation between postoperative TPA and PTA. CONCLUSION: The TPLO procedure alters the PTA to 90° in dogs with cranial cruciate ligament rupture similar to tibial tuberosity advancement (TTA). CLINICAL SIGNIFICANCE: The TPLO may provide dynamic stability to the cranial cruciate deficient stifle by altering the TPA relative to the patellar tendon and creating a PTA of 90°. The biomechanical principle and mechanism of action of TPLO may be similar to TTA.

Incidence, prevalence, severity, and risk factors for ruminal acidosis in feedlot steers during backgrounding, diet transition, and finishing.

The objective of this study was to determine the incidence, prevalence, severity, and risk factors for ruminal acidosis in feedlot steers during backgrounding, diet transition, and finishing. Steers were purchased from a local auction market (n = 250; mean ± SD; 330 ± 20.0 kg initial BW) and were grouped together with 28 steers fitted with a ruminal cannula (248 ± 25.5 kg initial BW). Steers were randomly allocated to 1 of 8 pens (3 to 4 cannulated steers per pen with a total of 35 steers/pen). The feeding period (143 d) was divided into 4 phases: backgrounding (BKGD; d 1 to 20), diet transition (TRAN; d 21 to 40), and the first (FIN1; d 41 to 91) and second half (FIN2; d 92 to 143) of finishing. The BKGD diet contained (% DM) barley silage (45.7%), barley grain (41.6%), canola meal (4.2%), and a pelleted mineral and vitamin supplement (8.5%). Steers were transitioned to a finishing diet containing (% DM) barley silage (5%), barley grain (80.9%), canola meal (4.9%), and a pelleted mineral and vitamin supplement (9.2%) using 4 transition diets. Feed was offered to achieve 5% refusals (as-is basis). Ruminal pH was recorded in cannulated steers every 10 min throughout the study, and feed refusals and BW were recorded at 2 wk intervals. Mean ruminal pH (P < 0.01) was 6.4, 6.3, 6.2, and 6.0 ± 0.01 during the BKGD, TRAN, FIN1, and FIN2, respectively. The duration (P < 0.01) pH < 5.5 was 4.1, 12.1, 78.7, and 194 ± 9.4 min/d during BKGD, TRAN, FIN1, and FIN2, respectively. Using a threshold of ruminal pH < 5.5 for at least 180 min to diagnose ruminal acidosis, incidence was defined as the number of times steers experienced ruminal acidosis during each period and prevalence was defined as the percentage of steers that experienced acidosis during each period. On average, the incidence rate (P < 0.01) of ruminal acidosis was 0.1, 0.3, 6.7, and 14.8 ± 0.97 episodes during BKGD, TRAN, FIN1, and FIN2, respectively. In the same order, the prevalence (P < 0.01) was 0.7, 1.7, 15.4, and 37.8 ± 2.0%. Based on multiple regression, factors associated with prevalence of ruminal acidosis and the duration pH < 5.5 were feeding phase (P < 0.01) and DMI (P < 0.01). Overall, the greatest incidence, prevalence, and severity of ruminal acidosis were observed towards the end of the finishing phase and were associated with days on feed and DMI.

Effect of development system on growth and reproductive performance of beef heifers.

Reproductive performance was evaluated in beef heifers born over a 2-yr period to determine the effects of target breeding weight (TBW) and development system (SYS) on growth and subsequent reproductive efficiency. Spring-born Angus heifers (253 ± 0.7 kg) were randomly allocated over 2 consecutive yr (yr 1, n = 80; yr 2, n = 96) to be developed to either 55% (350 kg) of mature BW (moderate gain, MG) or 62% (395 kg) of mature BW (high gain, HG). Each MG and HG group was further assigned to 1 of 2 replicated systems: (1) bale graze bromegrass-alfalfa round bales in field paddocks (BG) or (2) fed bromegrass-alfalfa round bales in drylot pens (DL). Heifers were fed a diet of bromegrass-alfalfa hay (56.9% TDN; 9.8% CP) and barley grain supplement (85.1% TDN; 12.3% CP). After the 202-d development period, heifers were exposed to bulls for a 63-d breeding season. Target BW × SYS interactions were not detected for any measured parameters. During the winter development period, MG heifers had lower (P = 0.01) ADG than HG heifers and MG heifers had lighter (P = 0.01) BW at breeding. The proportion of heifers attaining puberty by 14.5 mo of age was less (P = 0.05) in MG (20 ± 4%) than HG heifers (52 ± 3%). From the end of the 202-d development period to pregnancy diagnosis, ADG was greater (P = 0.04) in MG heifers than HG heifers (0.83 vs. 0.71 kg/d). First-calf pregnancy rates were 86 and 88% for MG and HG heifers, respectively (P = 0.41). Second- and third-calf pregnancy rates of cows, developed in either a MG or HG system as heifers, were not different (P = 0.74; 94.7 vs. 95.9% and 93.8 vs. 93.9%, respectively). Economic analysis revealed a $58 reduced development cost for heifers developed to 55% compared with 62% of mature BW without a loss in reproductive performance.

Effects of dietary sulfur concentration and forage-to-concentrate ratio on ruminal fermentation, sulfur metabolism, and short-chain fatty acid absorption in beef heifers.

This study evaluated the effects of dietary S concentration and forage-to-concentrate ratio (F:C) on ruminal fermentation, S metabolism, and short-chain fatty acid (SCFA) absorption in beef heifers. Sixteen ruminally cannulated heifers (initial BW 628 ± 48 kg) were used in a randomized complete block design with a 2 × 2 factorial treatment arrangement. The main factors included F:C (4% forage vs. 51% forage, DM basis) and the S concentration, which was modified using differing sources of wheat dried distillers grains with solubles (DDGS) to achieve low- and high-S diets (LS = 0.30% vs. HS = 0.67% S on a DM basis). Elemental S was also added to increase the S content for the HS diets. Serum sulfate concentration from blood, sulfide (S(2-)), and SCFA concentrations from ruminal fluid, hydrogen sulfide (H2S) concentration from the ruminal gas cap, and urinary sulfate concentration were determined. Continuous rumen pH and SCFA (acetate, butyrate, and propionate) absorption were measured. There were no interactions between S concentration and F:C. The F:C did not affect DMI (P = 0.26) or ruminal S metabolite concentrations (P ≥ 0.19), but ruminal pH was lower (P < 0.01) and SCFA absorption was greater (P < 0.01) for low F:C diets. Heifers fed HS diets had less DMI (P < 0.01) but greater ruminal pH (P < 0.01), greater concentrations of ruminal H2S (P < 0.01) and serum sulfate (P < 0.01), and greater urinary sulfate concentration (P < 0.01) and output (P < 0.01) relative to heifers fed LS diets. Ruminal H2S was positively correlated with serum sulfate (r = 0.89; P < 0.01). Ruminal acetate concentration was not affected (P = 0.26) by dietary S concentration. Heifers fed the HS diet had lower (P = 0.01) ruminal propionate concentration and tended to have lower (P = 0.06) butyrate concentration than heifers fed the LS diet. Ruminal acetate was greater (P = 0.01) and butyrate was less (P < 0.01) with the high F:C diet than the low F:C diet. Both HS (P = 0.06) and low F:C (P = 0.07) diets tended to reduce urine output. Feeding HS diets reduced SCFA absorption (P < 0.05). In summary, S metabolism in beef heifers was not influenced by the F:C, but HS reduced DMI, inhibited SCFA absorption, and increased urinary S excretion.

Sensitivity of a real-time polymerase chain reaction for Tritrichomonas fetus in direct individual and pooled preputial samples.

The objective of this study was to evaluate the sensitivity of a commercially available real-time polymerase chain reaction (PCR) test for the detection of Tritrichomonas fetus in individual and pooled direct preputial samples. Two samples were collected and processed once a week from nine T. fetus-infected bulls (n = 121) and placed into either an InPouch TF or 2 mL of PBS. Preputial samples were also collected into both media and PBS from 1016 other bulls. All pouches were cultured and evaluated as per manufacturer's instructions. The prepuce samples collected directly into PBS were individually evaluated using real-time PCR by a commercial diagnostic laboratory. Direct preputial samples were then randomly divided for pooling into groups of 5 and 10 samples, ensuring that every pool had one sample from a known infected bull before testing using real-time PCR. Sensitivity was estimated for culture and real-time PCR of the 121 direct and culture-enriched individual samples from nine infected bulls. There were no differences (P = 0.12) among the sensitivity estimates for culture, 95.0% (95% confidence interval [CI]: 89.6%-97.7%); real-time PCR of culture-enriched samples, 95.9% (95% CI: 90.7-98.2); and direct preputial samples, 90.1% (95% CI: 83.5-94.2). There was also no significant difference (P = 0.08) between the sensitivity of real-time PCR for direct preputial samples in 110 pools of 5 (83.6%, 95% CI: 75.6-89.4) or 10 samples (77.3%, 95% CI: 68.6-84.1). The use of three sequential direct samples, collected in PBS at weekly intervals and tested by real-time PCR, increased the sensitivity to 100% for pools of 5 and 96% for pools of 10. In conclusion, direct preputial samples collected in PBS and tested by real-time PCR individually have comparable sensitivity to culture and real-time PCR in enriched samples. The use of pooled direct preputial samples appears to be relatively sensitive. However, this strategy requires repeated sampling to optimize sensitivity. Real-time PCR testing of preputial samples collected directly into PBS with the option of pooling would decrease the cost associated with screening bulls, and increase the feasibility of large epidemiological studies and active surveillance.

Understanding the role of sulfur-thiamine interaction in the pathogenesis of sulfur-induced polioencephalomalacia in beef cattle.

This study examined the role of sulfur (S) in the pathogenesis of S-induced polioencephalomalacia (PEM) in beef cattle in the context of thiamine status and metabolism. Thiamine, thiamine monophosphate (TMP) and thiamine pyrophosphate (TPP) status in rumen fluid, blood and brain tissue were determined in beef heifers fed 2 levels of S [low S (LS) vs. high S (HS)] at 2 forage-to-concentrate ratios (F:C). High S diet did not affect ruminal and blood thiamine status. Interestingly, however, HS diet showed increased brain thiamine levels. No gross or histopathological changes indicative of PEM were detected in the brains of the heifers. Of note, during the course of the present study, we documented an outbreak of S-induced PEM in commercial feedlot steers. Brain thiamine variables in experimental animals fed HS diet were then contrasted with brain thiamine status in PEM affected feedlot steers. Interestingly, in clinically normal animals, exposure to HS diet resulted in increased levels of both TMP and TPP in the brain tissue, in comparison to animals fed LS diet. In contrast, the PEM affected brains showed overall lower levels of thiamine phosphates. It is noteworthy that TPP levels were 36.5% lower, despite 4.9-fold higher free thiamine in PEM brains compared to normal brains. Our results indicate that high dietary S may increase the metabolic demand for TPP, and that animals incapable of maintaining requisite levels of brain TPP are at high risk to develop fulminant cerebrocortical necrosis.

The effect of blood contamination on equine synovial fluid analysis.

OBJECTIVE: Based on a systemic complete blood count and a synovial fluid sample, to develop a mathematical model enabling the approximation of corrected values for synovial fluid white blood cell (WBC) count, neutrophil percentage, and total protein concentration in samples of synovial fluid that were contaminated by blood. METHODS: Peripheral venous blood and synovial fluid samples were obtained from ten horses. A pooled synovial fluid sample from each horse was separated into 2 mL aliquots, which were subsequently contaminated with a known percentage of autogenous blood (0 to 50% of the synovial fluid volume). A complete blood count, packed cell volume, total protein (TP) concentration, and differential cytological examination were performed in all the synovial fluid and venous blood samples. Regression analysis was used to generate a model to calculate non-contaminated synovial WBC count, TP concentration and synovial neutrophil percentage. Using a further five horses these models were applied in blinded fashion to contaminated synovial fluid samples. Calculated values were compared to non-contaminated measured values. RESULTS: Model results for synovial WBC count and TP concentration were not significantly different from measured values. Calculated neutrophil percentage of synovial fluid WBC was a mean of 6.6% higher than measured values and was significantly different. There was no effect of the severity of contamination (as a percentage of volume) on the ability of the models to predict any of the outcome variables. CLINICAL SIGNIFICANCE: It is possible to calculate non-contaminated synovial fluid WBC and TP values, but not neutrophil percentage, from heavily contaminated samples. Further study would allow for improved prediction, validation and extrapolation to a wider horse population.

The impact of vitamin A restriction and ADH1C genotype on marbling in feedlot steers.

A novel SNP was discovered within the promoter region of alcohol dehydrogenase 1C (ADH1C c.-64T>C), the C allele eliminating a potential binding site for the transcription factor C/EPBα. The purpose of this study was to examine if an interaction between this SNP and vitamin A restriction had an effect on carcass characteristics in beef cattle. Following backgrounding on a ß-carotene-deficient diet, 130 steers (50 TT, 50 CT, and 30 CC) were finished for 5 mo and received either no supplemental vitamin A (unsupplemented) or 750,000 IU/mo (supplemented). A subgroup of 5 steers • genotype(-1) • treatment(-1) was randomly selected for pre- and postfinishing liver biopsies to assess vitamin A status and measure gene expression. Unsupplemented steers (Bos taurus) had significantly greater (P < 0.05) marbling scores than supplemented steers. There was a significant interaction between genotype and vitamin A supplementation on ether-extractable intramuscular fat (IMF). Within the unsupplemented treatment, TT steers had nearly 23% greater IMF than CC steers. Additionally, unsupplemented TT steers had over 24% greater IMF than supplemented TT steers. Expression of ADH1C in the liver was additive with each additional T allele, potentially due to the elimination of a possible binding site for C/EBPα. It is plausible that CC cattle have reduced ability to metabolize retinol to retinaldehyde (and subsequently retinoic acid) and that a phenotypic effect is only observed when vitamin A is limiting. Therefore, ADH1C c.-64T>C genotype, in combination with reduced vitamin A supplementation, could potentially be implemented in marker-assisted management to maximize marbling in finishing cattle.

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.

Attitudes of Canadian dairy farmers toward a voluntary Johne's disease control program.

The success of Johne's disease (JD) control programs based on risk assessment (RA) depends on producers' compliance with suggested management practices. One objective of this study was to describe the perception of participating Canadian dairy farmers of the impact of JD, the RA process, and suggested management strategies. The second objective was to describe the cost of changes in management practices following the RA. A telephone survey was conducted with 238 dairy farmers in Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia. The producers agreed to participate in this follow-up study after they had been enrolled in an RA-based voluntary JD control program and had tested their herd with the JD milk ELISA test in 2005 to 2007. The majority of farms had no JD test-positive cows and, although some producers thought they had experienced the economic impact of JD, many did not see JD as a current problem for their herd. The majority of producers enrolled in this program because they were concerned that Mycobacterium avium ssp. paratuberculosis could be perceived by consumers as a cause for Crohn's disease in humans, which could lead to altered purchasing behavior of milk and milk products. Fifty-two farm-specific recommendations had been made after the initial RA. Although the producers generally liked the program and found the recommendations reasonable and feasible, on average only 2 of 6 suggestions made specifically to them were implemented. The recommendation with the highest compliance was culling of JD test-positive cows. The main reasons for noncompliance were that the dairy producer did not believe a change of management practices was necessary or the available barn setting or space did not allow the change. Producers were generally uncomfortable estimating time and monetary expenses for management changes, but found that several suggested management practices actually saved time and money. In addition, 39% of the producers that implemented at least 1 recommendation thought their calf and herd health had improved subsequently. This indicates that the communication of associated benefits needs to be improved to increase the compliance of producers with recommended management practices.

Knowledge and attitudes towards food safety among Canadian dairy producers.

The Canadian dairy industry has recently begun implementing an on-farm food-safety (OFFS) program called Canadian Quality Milk (CQM). For CQM to be effective, producers should be familiar with food-safety hazards in their industry and have an adequate understanding of on-farm good production practices that are necessary to ensure safe food. To assess their knowledge and attitudes towards food safety, a postal questionnaire was administered to all (n=10,474) Canadian dairy producers enrolled in dairy herd-improvement organizations in 2008. The response rate was 20.9% (2185/10,474). Most producers (88.7%) reported that they or their families consume unpasteurized milk from their bulk milk tanks and 36.3% indicated that consumers should be able to purchase unpasteurized milk in Canada. Producers who reported completion of a dairy-health management course (OR=0.74, 95% CI: 0.60, 0.92) and participation in CQM (OR=0.79, 95% CI: 0.64, 0.97) were less likely to support the availability of unpasteurized milk for consumers, while organic producers (OR=2.10, 95% CI: 1.27, 3.47), younger producers (aged <30) and producers with smaller herds were more likely to favour this practice. Two-thirds of producers (66.7%) were concerned that antimicrobial resistance (AMR) might preclude successful treatment of sick cattle. Producers who completed a dairy-health management course (OR=1.37, 95% CI: 1.11, 1.69), organic producers (OR=2.00, 95% CI: 1.09, 3.69) and producers from Quebec compared to each other province were more likely to indicate concern about AMR. Most producers reported that Salmonella (74.2%) and Escherichia coli (73.0%) could be transmitted through contaminated beef or milk to humans, while most were not sure or did not think that Brucella (70.3%) and Cryptosporidium (88.5%) could be transmitted via these routes. Most producers did not perceive that any type of farm visitor has a high risk of introducing infectious agents into their herds. Producers rated veterinarians as very knowledgeable about OFFS (90.9% answered 4 or 5 on a five-point scale) and a favoured (73.1%) source of information about food safety. In contrast, only 13.2% and 30.2% of producers, respectively, indicated that consumers and government personnel are knowledgeable about OFFS. Targeted continuing education for dairy producers in Canada should address the major gaps in knowledge and attitudes towards food safety identified in this study, and veterinarians should be included as key knowledge-transfer informants.

Pain mitigation after band castration of beef calves and its effects on performance, behavior, Escherichia coli, and salivary cortisol.

Eighty-nine steer and bull calves (210 +/- 20 d of age) were randomly assigned to a 2 x 2 factorial arrangement of treatments to study the effect of sham or band castration (CAST) with or without pain medication (MED) on performance, behavior, cortisol, and Escherichia coli shedding. Steers (serving as controls; C) were previously castrated at 34 +/- 10 d of age, whereas bulls (B) remained intact until band application on d 20 of the experiment. One-half of the calves in each group received pain medication (M; xylazine epidural and intravenous flunixin meglumine) or saline (NM) solutions at 0.5 h before castration. Feed intake, ADG, and feeding behavior were measured over a 3-wk period before (used as covariates) and a 6-wk period after castration. Fecal and saliva samples were collected from 32 calves for E. coli enumeration at -7 (covariate), 2, 5, and 7 d, and for cortisol concentration at -0.5 (covariate), 0, 0.5, 1, 2, 4, 24, 48, 168, and 336 h relative to castration, respectively. Lying behavior was measured in the home pen and step length at exit from the chute. There were no significant CAST x MED interactions on growth rate or feed intake. Overall ADG was less in B compared with C (P < 0.001), but feed intake was less during wk 4 only (P = 0.01). On average, M had less intake (P = 0.02) and eating rate (P = 0.04) than NM calves. The BM had less fecal E. coli counts than CM (P = 0.05) and castrated and nonmedicated calves (P = 0.08). Salivary cortisol was less in BM compared with the rest of treatments at 1 and 2 h after banding (P

Attitudes towards the Canadian quality milk program and use of good production practices among Canadian dairy producers.

To harmonize good production practices (GPP) for dairy producers in Canada, the Canadian dairy industry has developed and is implementing a program called Canadian Quality Milk (CQM). A postal questionnaire was administered to all Canadian dairy producers enrolled in dairy herd-improvement organizations in 2008 (n=10,474) to investigate their attitudes towards the program and to establish baseline information on their use of GPP. The response percentage was 20.9% (2185/10,474). Two-thirds of producers (67.6%) reported participation in CQM and 61.4% of these indicated that the requirements were easy to implement. Most producers (85.0%) reported the use of cats as a pest-control method in their barns. For dead-livestock disposal, 65.0% and 38.0% indicated use of a collection service and burial, respectively. Nearly 40.0% of respondents indicated that they purchase replacement cattle, and somatic cell-count score was the main health indicator considered before purchase. Over 70% of producers reported that they clean and disinfect maternity, calf and weaned-calf pens, while only 34.1% and 53.1% reported that they provide visitors and employees, respectively, with clean clothes and boots. Through latent-class analysis, five groups (classes) of producers with distinctive patterns of reported use of GPP were identified. These were labelled as "minimal", "sanitation-only", "employee-visitor hygiene", "typical" and "ideal" user groups, with 11.1%, 23.8%, 20.2%, 37.1% and 7.7% of respondents, respectively. Respondents in the "ideal users" group had a higher probability of reporting the use of each GPP and were more likely to have completed an educational course in food safety compared to respondents in each other group. They were also more likely to have a herd size in the uppermost quartile (>65 cows) and report participation in CQM compared to each other group except the "employee-visitor hygiene users". The greatest differences were observed when compared to the "minimal users" group for completion of a food-safety course (OR=2.81), participation in CQM (OR=2.39) and having a herd size of >65 vs. <36 cows (OR=3.04). Targeted education of dairy producers on the importance of various GPP (e.g. detailed health assessments of replacement cattle before purchase) for infection control is warranted.

The effects of triiodothyronine augmentation on antithrombin III levels in sepsis.

Sepsis and multisystem organ failure are often associated with disseminated intravascular coagulation and consumption of coagulation inhibitors such as antithrombin III (ATIII). The "sick euthyroid syndrome" is also seen in association with significant illnesses and consists of decreased levels of circulating triiodothyronine (T3). We evaluated whether T3 supplementation would affect ATIII levels in septic rats. Thirty Sprague-Dawley rats were divided into three groups: sham laparotomy (S) plus saline, cecal ligation and puncture (CLP) plus saline, and CLP plus T3 (3 ng/hour) via an osmotic minipump. Twenty-four hours after laparotomy blood was drawn, and T3 and ATIII levels were then compared with baseline values. T3 supplementation partially negated the sepsis-induced decrease in circulating T3 levels. The levels are expressed as percentage change from the levels before surgery (S, -12.9 +/- 3.1; CLP, -60.0 +/- 5.3; CLP + T3, -34.9 +/- 4.3; mean +/- standard error; P < 0.05). T3 supplementation also statistically changed the percentage difference in ATIII levels toward the control (S, 9.6 +/- 2.8; CLP, -37.9 +/- 5.4; CLP + T3, -16.0 +/- 4.5; mean +/- standard error; P < 0.01). T3 supplementation reduced the sepsis-induced decrease in ATIII levels. Whether this was accomplished by decreased consumption or increased production of ATIII via the direct anabolic effect of T3 on acute-phase protein synthesis in the liver is unknown and warrants further investigation.