Effect of use of teat sealants at drying off on the uptake of colostral antibodies by calves, as estimated by measuring gamma-glutamyl transferase activity.

To determine the effect of using internal teat sealants in cows at drying off on the immune status of their calves, as indicated by activity of gamma glutamyl transferase (GGT) in serum, within 24 h of birth. Cows in one herd were treated at drying off with intramammary 600-mg cloxacillin and either no additional treatment or treatment with internal teat sealant containing bismuth subnitrate. Subsequently after calving, blood samples were collected from 35 calves after separation from their dams and prior to being fed pooled colostrum. Calves were collected once daily. Activity of GGT in serum was measured. The influence of treatment of the dam with teat sealant on activity of GGT in serum of the calf, and thus the transfer of colostral antibodies directly from the dam to the calf, was assessed. Activity of GGT in serum ranged from 8 to 8,560 IU/L. Of the 35 calves sampled only three (two from dams that were not treated with internal teat sealant) had GGT activity < 200 IU/L, indicative of the failure of passive transfer of antibodies. Median activity of GGT in calves from dams treated with teat sealant was 2,643 IU/L while that in calves from dams which were not treated with teat sealant was 2,286 IU/L. There was no effect of treatment with teat sealant or date of sampling on activity of GGT in serum (p > 0.1). Treatment of cows with internal teat sealant at drying off had no effect on transfer of colostral antibodies following calving. The use of teat sealants is not likely to impact on colostrum uptake on farms where direct transfer of colostral antibodies between dam and calf is good. On farms where such direct transfer is poor, early supplementation of all calves with colostrum is likely to be required to prevent the failure of passive transfer, so any impact of teat sealants on uptake of colostrum is likely to be of little consequence.