Selective dry cow therapy effect on milk yield and somatic cell count: A retrospective cohort study

Abstract

Antibiotic dry cow therapy (aDCT) at the end of lactation is an effective mastitis control measure. Selective dry cow therapy means that only infected or presumedinfected cows are treated, instead of aDCT being used as a treatment for all cows. Because antibiotic resistance poses a global threat, livestock production is under increasing pressure to reduce antibiotic use. Changes in management should not, however, impair animal welfare or cause significant economic losses. Our objective was to compare milk yield and somatic cell count (SCC) between aDCT-treated and untreated cows in herds that used selective aDCT, taking into account risk factors for reduced yield and high SCC. The information source was 2015 to 2017 Dairy Herd Improvement data, with 4,720 multiparous cows from 172 Finnish dairy farms. The response variables were testday milk yield (kg/d) and naturally log-transformed composite SCC (×1,000 cells/mL) during the first 154 d in milk (DIM). The statistical tool was a linear mixed-effects model with 2-level random intercepts, cows nested within herds, and a first-order autoregressive [AR(1)] correlation structure. The overall proportion of aDCT-treated cows was 25% (1,176/4,720). Due to the interaction effect, SCC on the last test day prior to dry-off affected postcalving milk yield differently in aDCT-treated cows than in untreated cows. A higher SCC prior to dry-off correlated with a greater daily yield difference after calving between cows treated and untreated. The majority of cows had SCC < 200,000 cells/mL before dry-off, and as SCC before dry-off decreased, difference in yield between aDCT-treated and untreated cows decreased. Postcalving SCC was lower for aDCT-treated cows compared with untreated cows. To illustrate, for cows with an SCC of 200,000 cells/mL before dry-off, compared with untreated cows, aDCTtreated cows produced 0.97 kg/d more milk and, at 45 DIM, had an SCC that was 20,000 cells/mL lower.Higher late-lactation SCC and lactational mastitis treatments were associated with higher postcalving SCC. A dry period lasting more than 30 d was associated with higher yields but not with SCC. Our findings indicate that a missed aDCT treatment for a high-SCC cow has a negative effect on subsequent lactation milk yield and SCC, which emphasizes the importance of accurate selection of cows to be treated.

Economic perspectives on blanket and selective dry cow therapy

“…Based on the DHI data utilized by Niemi et al (2022), only 14% of the SDCT farms treated more than half their cows. In this study, we used the mean, 21%, as the proportion of cows to be treated.…”

“…The microbiological analyses of presumably infected quarters commonly supplement other udder-health information and support treatment decisions (Vilar et al 2018. On Finnish SDCT farms, selection criteria seem to be quite optimal, because the proportion of DCT-treated cows was equivalent to the proportion of cows with SCC ≥200,000 cells ml -1 near dry-off and the post-calving proportions of mastitis treatments between selectively DCT-treated and -untreated cows were similar (Niemi et al 2021(Niemi et al , 2022.…”

Integrierte Tierärztliche Bestandsbetreuung und Selektives Trockenstellen in Deutschland

“…Je nach gewählten Selektionskriterien werden mögliche Anti biotikaeinsparungen von 23,5 % bis 75 % durch Selektives Trocken stellen (ST) in Milchviehbetrieben, im Vergleich zu Betrieben die generell antibiotische Trockenstellpräparate einsetzten, beschrie ben [8][9][10][11][12][13]. Inwieweit das ST in deutschen Nutztierpraxen und Milchviehbetrieben zur Antibiotikareduktion durchgeführt wird und ob bzw.…”

Untersuchungen zu einem kontrollierten, entscheidungsbaumbasierten Verfahren des Selektiven Trockenstellens in Bayerischen Milchviehbetrieben

“…In dieser Studie konnten 39,1 % der Kühe ohne Anwendung eines AB ("ohne AB") trockengestellt werden, betriebsindividuell waren es 23,3 % bis 62,2 % [13]. In verschiedenen Studien werden, abhängig von den gewählten Selektionskriterien, mögliche Antibiotikaeinsparungen von 23,5 % bis 75,1 % durch Selektives TS beschrieben [15][16][17][18][19]. In der Studie von Schmon [13] hatten Kühe, die "ohne AB" trockengestellt wurden, im Vergleich zu antibiotisch trockengestellten Kühen keine schlechtere Eutergesundheit in Bezug auf die Trockenstehphase sowie die Zeit nach der Kalbung.…”