Assessing different chemoprophylactic protocols against bovine tick-borne diseases and their influence on the weight gain of calves

Resumo

In the present study, 87 Aberdeen Angus calves were used to assess the effects of low dose, agent-specific drugs on weight gain after a babesiosis and anaplasmosis outbreak. All animals were weighed on weaning (day –34) and again on day zero, with a mean (on day zero) of 223.46 Kg and an average individual daily weight gain (ADG) of 0.258 Kg. The animals were then separated in three groups: G1 was composed of 37 calves with below average ADG; G2 was composed of 35 animals with below average ADG; and G3 was composed of 15 animals with above average ADG. On day zero animals in G1 were treated with 1.17 mg Kg-1 of diminazene diaceturate and 6.7 mg Kg-1 of oxytetracycline; those in G2 were treated with 1.2 mg Kg-1 of imidocarb dipropionate; and those in G3 were not treated. The animals were then monitored daily for the onset of disease, and on days 15 and 34 they were weighed and had their blood harvested. Animals in G1 had the better overall ADG (0.613 Kg day-1) (P<0.05), with no clinical cases during the experiment. The performance in G2 was moderate, not differing from either G1 or G3 (mean ADG = 0.528 Kg day-1), however, this group had two clinical cases of anaplasmosis during the experiment. Animals in G3 had the worst performance, considering ADG (0.343 Kg day-1). When total weight gain per animal is compared for the study period (35 days), those in G1 gained an average of 20.851 Kg, followed by animals in G2 with 17.957 Kg, and then animals in G3 with 11.667 Kg. These results show that a low dose, agent specific (G1) drug protocol will considerably reduce the detrimental effects of subclinical tick borne diseases in the post weaning period and can be recommended as a rearing tool for calves destined for early slaughter.