Use of a culture-independent on-farm algorithm to guide the use of selective dry-cow antibiotic therapy

Abstract

An algorithm using only computer-based records to guide selective dry-cow therapy was evaluated at a New York State dairy farm via a randomized field trial. DairyComp 305 (Valley Ag Software, Tulare, CA) and Dairy Herd Improvement Association test-day data were used to identify cows as low risk (cows that might not benefit from dry-cow antibiotics) or high risk (cows that will likely benefit). Low-risk cows were those that had all of the following: somatic cell count (SCC) ≤200,000 cells/mL at last test, an average SCC ≤200,000 cells/mL over the last 3 tests, no signs of clinical mastitis at dry-off, and no more than 1 clinical mastitis event in the current lactation. Low-risk cows were randomly assigned to receive intramammary antibiotics and external teat sealant (ABXTS) or external teat sealant only (TS) at dry-off. Using pre-dry-off and postcalving quarter-level culture results, low-risk quarters were assessed for microbiological cure risk and new infection risk. Groups were also assessed for differences in first-test milk yield and linear scores, individual milk weights for the first 30 d, and culling and mastitis events before 30 d in milk. A total of 304 cows and 1,040 quarters in the ABXTS group and 307 cows and 1,058 quarters in the TS group were enrolled. Among cows to be dried, the proportion of cows that met low-risk criteria was 64% (n = 611/953). Of cultures eligible for bacteriological cure analysis (n = 171), 93% of ABXTS cured, whereas 88% of TS cured. Of the non-cures, 95% were contributed by the minor pathogens coagulase-negative staphylococci (n = 19/20). These organisms also accounted for 57.5% of new infections (n = 77/134). We found no statistical differences between treatment groups for new infection risk (TS = 7.3% quarters experiencing new infections; ABXTS = 5.5%), milk production (ABXTS = 40.5 kg; TS = 41.2 kg), linear scores (ABXTS = 2.5; TS = 2.7), culling events (ABXTS, n = 18; TS, n = 15), or clinical mastitis events (ABXTS, n = 9; TS, n = 5). Results suggest that the algorithm used decreased dry-cow antibiotic use by approximately 60% without adversely affecting production or health outcomes.

Effect of using internal teat sealant with or without antibiotic therapy at dry-off on subsequent somatic cell count and milk production

“…Milk test-day SCC records and recorded mastitis incidences are useful for identifying animals for drycow treatment, as first reported by Vasquez et al (2018). Although the present study demonstrated no difference in the test-day SCS of LowSCC cows treated with teat sealant only and HighSCC cows (cows with a high SCC or an incidence of mastitis in the previous lactation; Table 3), bacteria were identified at dry-off (after animals were assigned treatment) in the quarters of 28% of HighSCC cow lactations compared with 12% of LowSCC cow lactations.…”

“…However, the pathogens involved, as well as the timing of IMI, differ between heifers and older cows (Pyörälä and Taponen, 2009). Vasquez et al (2018) documented a numerically higher milk yield (P = 0.20) across the first 26 DIM in cows treated with teat sealant only compared with cows treated with antibiotic and teat sealant. Differences in milk yield were only detected later in lactation in the present study (Table 1).…”

“…More recently, Vasquez et al (2018) showed no difference in the cure rate or new infection rate of 611 cows treated with either teat sealant only or antibiotic plus teat sealant, although the teat sealant group tended to perform worse (P = 0.09). However, the study of Vasquez et al (2018) used a single application of an external teat sealant, which is expected to offer less protection than a properly inserted internal teat sealant (Lim et al, 2007), as was used in the present study.…”

Rational Decision On the Use of Antibiotics During the Dry Period in Dairy Cows

“…On the other hand, CNS (54.31%) were more frequent, followed by Corynebacterium spp . (12.69%), in the results of microbiological culture examinations per mammary quarter before and after delivery (42) .…”

“…Using the culture test at the end of the D-70 lactation, it has a greater number of negative teats diagnosed, using fewer antibiotics and reducing the cost of treatment in the dry period. Selective treatment at the time of drying using the culture method may be economically more viable than BDCT if the number of intramammary infections is low with lower intramammary antibiotic expense (9, 42) .…”