A double-blind, randomized clinical trial was conducted in 5 commercial dairy herds in southern Ontario with 1,362 cows enrolled to evaluate the effect of prepartum administration of recombinant bovine somatotropin (rbST) on health and performance. Cows were randomly assigned to receive either 325 mg of sometribove zinc suspension (n=680) or a placebo injection (n=682; control) subcutaneously every 14 d until calving. Treatments started 28 to 22 d before expected calving, with a maximum of 3 treatments per cow. Serum samples taken at the time of enrollment, 1 wk before calving, and weekly for 3 wk after calving were analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, aspartate aminotransferase, calcium, and haptoglobin. Diseases were recorded by farm staff. Incidences of clinical ketosis, clinical mastitis, displaced abomasum, metritis, retained placenta, milk fever, and lameness were similar between groups. Body condition score was lower for treated than for control cows at 3 wk after calving (3.13 and 3.17, respectively). Serum NEFA tended to be higher for treated than for control cows by 0.01 mmol/L. Overall BHBA was not different between groups, but BHBA for treated cows was higher in wk 1 after calving (750 and 698 μmol/L, respectively) and tended to be higher in wk 2 after calving (779 and 735 μmol/L, respectively). Incidence of hyperketonemia was similar between groups. Treated cows had higher serum glucose compared with control cows (2.8 and 2.7 mmol/L, respectively). We detected no differences in serum aspartate aminotransferase, calcium, or haptoglobin between groups. Milk yield was recorded daily for each cow for 63 d, and did not differ between groups (37.1 ± 0.5 kg and 36.7 ± 0.5 kg, respectively) but we detected a tendency for treated cows to produce 0.8 kg/d more milk than control cows in wk 1 after calving. We observed no difference between groups in the time from calving to first insemination or the probability of pregnancy at the first insemination. Groups did not differ in the proportion of anovular cows at 53 ± 3 d in milk based on serum progesterone measured from a subset of cows (38.0 and 34.3%, respectively, for treated and control groups). We found no difference between groups in dry matter intake from 21 d before calving to 63 d after calving in a subset of cows (17.4 ± 0.4 and 17.5 ± 0.4 kg/d, respectively). Based on results of the current study, biweekly (every 14 d) administration of rbST before calving to prevent disease and enhance performance is not recommended.
AIMS To evaluate the Rapid Mastitis test (RMT, or California Mastitis test) and electrical conductivity (EC) at drying off when used alone or in combination with herd test data (maximum or last herd test somatic cell counts (SCC) before drying off), to define cows or quarters with intramammary infection, using microbiological culture as the gold standard. METHODS Quarter-level milk samples (n=609) from clinically healthy cows (n=153), in three herds in the Waikato region of New Zealand, were tested at drying off using the RMT and EC, and were collected for microbiological culture. The maximum SCC and the SCC at the last herd test of the preceding lactation were determined for each cow. The sensitivity, specificity, and positive and negative predictive values for each test were calculated for different cut-points, using microbiological culture as the gold standard. Receiver operating characteristic curves were generated and the area under the curve (AUC) was calculated for each test. The same parameters were calculated for combinations of two tests in parallel or in series. RESULTS Infection with any pathogen was detected in 62/153 (40.5%) cows and 99/609 (16.3%) quarters, and with major pathogens in 7/153 (4.6%) cows and 8/609 (1.3%) quarters. When predicting infection with any pathogen at the cow-level, the coefficient of agreement was highest for SCC (<0.32) and RMT (<0.28) and lowest for EC (<0.12); the AUC for RMT and EC when used singly ranged from 0.57-0.69, and in combination with SCC ranged from 0.68-0.75. AUC were similar for tests that used either the last or the maximum SCC. CONCLUSIONS AND CLINICAL RELEVANCE When evaluated singly, RMT and EC had only low to moderate diagnostic utility compared to bacteriological culture. When they were combined with SCC and interpreted in parallel, the results were improved, but only moderately. For herds that conduct herd testing, a single herd test late in lactation was as predictive of intramammary infection at drying off as multiple herd tests through the lactation. For herds that do not conduct herd testing, RMT has greater utility than EC.
To reduce antimicrobial use, infusion of antimicrobials into only infected cows at the end of lactation (selective dry cow therapy) is preferable to infusion of every cow with antimicrobials. Use of selective dry cow antimicrobial therapy requires differentiation of probably infected from uninfected cows to enable treatment allocation. Milk somatic cell count (SCC) has been used to distinguish between cows with and without intramammary infection (IMI). However, SCC may be influenced by milk yield, stage of lactation, breed, and herd-level variables such as prevalence of infection. Cut points for SCC, to distinguish between cows with and without an IMI, may need to differ between cow age groups and breeds, or among herds. This study evaluated associations between SCC and major pathogen IMI in one or more quarters of 2,606 cows from 36 herds in 4 regions of New Zealand. In the last week of lactation, cows selected at random had milk samples collected from each quarter, and the teat-end condition and hygiene of the udder were scored. Herd-and cow-level data including age, breed, milk volume, and SCC at each production were recorded, and bulk tank milk SCC and volume of milk shipped were collated. At cow level, the association between average, maximum, and last cow-composite SCC, and presence of a major pathogen IMI in one or more quarters of cows, was examined using receiver operator curves. Predictive logistic regression models were then developed that included potential effect modifiers such as age, milk yield, and bulk tank milk SCC. The population average prevalence of major pathogen IMI was 7.2% of cows (95% confidence interval = 5.9-8.6), and this varied significantly between herds. The average, maximum, and last cow-composite SCC of lactation were all predictive of presence of a major pathogen IMI and did not differ in their ability to discriminate infected from uninfected cows. However, the optimal cut points for the last SCC, the maximum SCC, and average SCC were 108, 152, and 105 × 1,000 cells/mL, respectively. Inclusion of age, bulk tank SCC, and history of clinical mastitis improved overall model fit. However, inclusion of these variables did not improve the discriminatory power of maximum cow-composite SCC used alone. We conclude that cow-composite SCC on its own resulted in sensitivities and specificities of between 0.76 and 0.86, and 0.71 to 0.80, respectively, for determination of presence of major pattern IMI, and the predictive value was not improved by addition of other predictor variables.
OBJECTIVE To estimate the cost of a case of retained fetal membranes (RFM) for dairy herds in the United States. DESIGN Deterministic computer-based spreadsheet analysis. SAMPLE Inputs from published studies and reports. PROCEDURES Economic losses attributable to RFM were direct (reduction in milk yield and longer interval until pregnancy) and indirect (increased risk of developing clinical disease and increased culling risk). Cost attributable to milk loss was calculated as the mean marginal loss of milk production for cows with RFM and cows with RFM complicated by metritis. Cost of the increased risk of developing clinical disease because of RFM was a product of the cost of each clinical disease and the risk of each clinical disease attributable to RFM. Cost attributable to reduced reproductive performance was a function of a longer interval until pregnancy, whereas cost for increased culling attributable to RFM was associated with the market value of cull cows and replacement heifers as well as herd turnover rate. RESULTS Cost of a case of RFM determined by use of default inputs was $386 (reduction in milk yield, $287; increased time until pregnancy, $73; increased disease risk, $25; and increased culling risk, $1). Sensitivity analysis revealed that milk and feed prices were the most influential inputs. CONCLUSIONS AND CLINICAL RELEVANCE Cost of a case of RFM, including uncomplicated cases, was substantial and comparable to that for other common clinical diseases during the transition period. Preventive measures during the nonlactating period should be considered to minimize the incidence of RFM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.