Python™, Yt–615, and Optimizer™ Ear Tags for Winter–Time Control of Cattle Lice in Wyoming, 1992

Abstract

Abstract The objective of this study was to evaluate PYthon™, YT𠄣615, and Optimizer™ ear tags applied at one tag per animal, and PYthon™ ear tags at two tags per animal for winter-time control of cattle lice. The experiment was performed at the University of Wyoming Research and Extension Center, Torrington, Wyoming. The experimental cattle were born in the spring of 1991. All were male castrates and were primarily Gelbvieh X Angus crosses. Animals were individually identified by numbered ear tags in both ears. The cattle were housed in ten separate pens at the rate of 5 or 6 animals per pen. Each pen was 20 X 60 ft with a 20-ft feed bunk across one end. Each animal received a finishing ration, free-choice, average weight gain was 2 lb per head per d. Salt, mineral mix, and water were provided ad libitum. Lice infestations were naturally acquired. Most cattle were infested with Linognathus vituli and Bovicola bovis. A few animals were infested with Solenopotes capillatus. Prior to treatment, the pens were ranked by total counts of L. vituli. The five pens with the highest mean counts and the five pens with the lowest mean counts were randomly assigned to one of the five ear tag treatments. All species of lice present on the animals were counted. Counts were performed by visual inspection of the cattle on d 0 (pretreatment), and 14, 28, 42, and 56 DAT. Lice were counted in eight examination sites on each animal. Specimens were identified by species and life stage (either adult or nymph). Examination sites and dimensions were as follows: topline 5 X 15 cm, withers 5 X 15 cm, around right eye 10 X 15 cm, around left eye 10 X 15 cm, right cheek 5 X 10 cm, left cheek 5 X 10 cm, muzzle 5 X 25 cm and dewlap 5 X 15 cm. These sample sites include predilection areas of L. vituli, B. bovis, and S. capillatus. For purposes of examination, cattle were individually restrained in a squeeze chute with a head catch. A high intensity light provided illumination. Total lice counts were transformed using In (total count + 1). A general linear model procedure (SAS) was used to analyse the transformed counts. Total variation in the lice count was partitioned into that attributable to the treatment, animal within treatment, sampling d, treatment X sampling d interaction, and residual. Geometric means for lice counts were estimated for each treatment group on each sampling d. Percentage reduction in lice numbers from the first to the last d of the study were calculated from the geometric means of the treated and untreated cattle using the formula: