PRODUCTION EFFECTS OF CATTLE TICK (BOOPHILUS-MICROPLUS) INFESTATION OF HIGH-YIELDING DAIRY-COWS

Forty mid-lactation Holstein-Friesian cows. 100% lot fed, were assigne d to four groups for 15 weeks. Two groups of 10 cows were infested eac h week with a gradually increasing number of Boophilus microplus larva e, while the other two groups were maintained free of ticks. Milk yiel d and composition (including somatic cell count, SCC), liveweight, dry matter intake, packed cell volume (PCV) and total plasma protein (TPP ) were measured throughout the 15 week period. By week 15, control cow s produced 2.861 more milk and 0.14 kg more butterfat each day and had gained 10.6 kg more liveweight than infested cows. Each engorging fem ale tick was estimated to be responsible for the loss of 8.9 ml of dai ly milk production and 1.0 g of bodyweight over the trial period. Milk composition, PCV and TPP were not significantly affected by cattle ti ck infestation. The dry matter intake of control cows was 0.83 kg grea ter than infested cows in week 12. (C) 1998 Elsevier Science B,V.