Tick resistance and heat tolerance characteristics in cattle. III. Sweating rate / Resistência ao carrapato E tolerância ao calor em bovinos III. taxa de sudação

ABSTRACT

Cattle in a sustainable tropical livestock should be heat tolerant and resistant to ticks. The relationship between Rhipicephalus (Boophilus) microplus infestation and sweating rate, an important heat tolerance characteristic, was studied in six Nellore and four Holstein steers of seven-month-old. They were artificial infested (a.i.) with 10,000 (Holstein) and 20,000 (Nellore) larvae in 16/Apr/2011. In days 20, 23 and 24 after the infestation, the 10 bigger females ticks found in whole animal were weighed and put in a chamber (27 oC and 80% RH), weighing the egg mass of each female tick fourteen days after. The sweating rate (SRskin, measured by Scheleger and Turner, 1963, method, in a shaved area of shoulder skin) was evaluated in 14/Apr (2 days before the a.i.) and in 05/May (19 days after a.i.). In 14/Apr the Scheleger and Turner, 1963, method was done on the coat not shaved (SRcoat). The sweating rate was measured in the afternoon (from 2 P.M.), after 30 minutes of direct sunlight, on April. On May, the animals remained 60 minutes in direct sunlight because this day was colder. The experimental design was a non-probability sample restricted to the 10 available animals. Data from the steers sweating rate were analyzed using the General linear models of the SPSS® statistical package (version 12.0) using SRskin as dependent variable and breed and sampling date as independent

RESUMO

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