Alterations in Host Metabolism by the Specific and Anorectic Effects of the Cattle Tick (Boophilus Microplus) I. Food Intake and Body Weight Growth

Abstract

This experiment was designed to measure the effects of infestation by B. microplus on cattle and to separate the effects of reduced food intake ("anorectic effect") from those due to the remaining factors of tick infestation ("specific effect"). Hereford cattle kept on a high-quality diet were studied over a treatment period of 11 weeks with the tick-infested animals being infested regularly with equal larval doses for each animal.The anorectic effect accounted for approximately 65% of the depression of body weight due to tick infestation. Body weights were not related to the numbers of maturing female ticks counted on the infested animals. However, the body weights were related to food intake, the large variation in which was considered a reflection of the variable effect of the toxic principle of the tick on the appetite of the cattle.After treatment, tick-infested cattle were kept clear of tick and run with the two control groups of cattle. Pasture was supplemented with extra rations. The compensatory gain made by the infested group was less than that of the group which had been matched with it for food intake and kept tick-free. This indicates a severe effect on the metabolism of the tick-infested animals, with prolonged after-effects.

Alterations in Host Metabolism by the Specific and Anorectic Effects of the Cattle Tick (Boophilus Microplus) III. Metabolic Implication of Blood Volume Body Water and Carcass Composition Changes

“…The experimental design is fully described in a previous paper (Seebeck, Springell, and O'Kelly 1971). Twenty-one 13-months-old Hereford steers at pasture were allocated to three groups of seven animals, so that each group covered a similar weight range.…”

“…Tick infestations had to be reduced on days 40-63 because of its serious effects on food intake and body weight. Female ticks maturing in the TI group of animals were counted by the procedure described by Seebeck, Springell, and O'Kelly (1971). Studies were performed immediately prior to infestation, then again at the end of infestation (11 weeks later), and finally at slaughter.…”

“…Studies were performed immediately prior to infestation, then again at the end of infestation (11 weeks later), and finally at slaughter. The diet during the recovery phase consisted of free access to pasture together with cattle cube supplementation (Seebeck, Springell, and O'Kelly 1971).…”

“…This could be caused by a drop in the red cell volume, or by an increase in the plasma volume or both. In order to understand more fully how the parasite exerts its effect on the host, it was necessary to determine whether apparent changes in the concentration of metabolites (O'Kelly, Seebeck, and Springell 1971) reflected genuine alterations in the amounts of each metabolite, or whether the changes were caused by water transfer in or out of the vascular system.…”

Alterations in Host Metabolism by the Specific and Anorectic Effects of the Cattle Tick (Boophilus Microplus) II. Changes in Blood Composition

“…The experimental design is fully described in Part I (Seebeck, Springell, and O'Kelly 1971). Briefly, the tick resistance of 21 13-month-old Hereford steers at pasture was assessod after two artificial tick infestations (0·5 g and 1· 0 g larvae).…”