Impact of the carrier state by Theileria annulata on milk yield in Tunisian crossbred (Bos taurus) cattle

ABSTRACTObjectiveTo estimate milk yield losses in Theileria annulata (T. annulata) carrier cows by a trial which was made in two cattle farms in the north of Tunisia.MethodsEight non-infected cows were randomly and equally divided into two groups: the treated and control groups. Eight T. annulata carrier cows were also randomly and equally divided into two groups: the treated and control groups.ResultsThere was a negative correlation between milk yield and parasitemia in both treated (r = −0.495, P = 0.037) and control carrier cows (r = −0.662, P = 0.003). Average adjusted lactation curve showed that milk yield in treated carrier cows was higher than that in control carrier cows. Daily milk yield losses due to T. annulata infection have been estimated at 0.77 kg per of each T. annulata carrier cow.ConclusionsSince T. annulata infection induces a small but persistent decrease of milk yield in T. annulata carrier cows, further studies are needed in a larger animal group to confirm and improve this estimation.