Selecting dairy cows for dry-off therapy by the somatic cell count

Abstract

The objective of this study was to test new type of dry-off treatment by analysis of the somatic cell count (SCC) before dry-off, in order to reduce the antibiotic use in dry cows. Nowadays the prophylactic antibiotic treatment during the dry-period is widely spread, to cure subclinical mastitis. This study shows, that the use of antibiotics can be reduced for healthy cows during the dry-off. This study was carried out on a commercial dairy farm in Hungary with 95 Holstein-Friesian cows. Before the cows were dried off, samples from each quarter had been taken and used for bacterial analyses and somatic cell count. The SCC was determined with a flouro-optical-counting system (Lactoscan SCC, Milkotronic Ltd., Nova Zagora, Bulgaria). Based on the SCC results, each teat quarter was assigned to one of two groups. Teats with a SSC above 200,000 cells/milliliter received an antibiotic treatment (Ubrostar, Boehringer Ingelheim) and teat sealant (OrbeSeal, Zoetis), all others received only teat sealant. Cows with 0 AB-treated quarters were the NONE group, cows with both treated and not treated quarters were assigned to the MIXED group, and those with all quarters treated were the ALL group. The presence of blind teat quarters were also taken to account. An existing linear SCC scoring method was also used (1 to 9). After parturition, new samples were taken (Day 3 to Day 5 post partum). Altogether 345 milk samples were taken both before dry-off and after calving. Of these samples, 91 had a SCC lower than 200,000 cells/ml (NO-AB), with a median cell count of 109,699 cells/ml, and 254 samples had a higher SCC (AB), 759,742 cells/ml on average. Mean linear SCC scores were 3 and 6, respectively. Based on this, 49 cows received AB in all quarters (ALL), 38 were in the MIXED group, and 8 received no AB treatment (NONE). Bacterial growth was found in 229 quarters. After calving, the NOAB and the AB teat quarters had significant difference in their median SCC-s (537,302 38 cells/ml and 210,660 cells/ml, respectively, P<0.05). Linear scores changed to 5 and 4.39, respectively. Median SCC of the cow groups (ALL, MIXED, NONE) were 149,204 cells/ml, 576,766 cells/ml and 235,347 cells/ml, respectively. The difference between the groups was also significant (P<0.05). The presence of a blind teat quarter had a negative effect on the SCC (P<0.05). Bacterial growth decreased to 89 quarters, but it did not have an effect on the SCC. After calving, 37.1% of the teat quarters received antibiotic treatment for mastitis, and there was no significant difference between the dry-off treatment groups (NO-AB: 38.46%, AB: 36.61%, P>0.05). In high SCC herds selective dry-off treatment doesn’t increase the occurrence of mastitis after calving, but it increases the SCC in the NO-AB group, though other factors (blind teat quarter) also play a role. However, not using AB at dry-off can be more economically beneficial in low SCC herds.