Criollo goats limit their grass intake in the early morning suggesting a prophylactic self-medication behaviour in a heterogeneous vegetation.

Abstract

The present study compared the feeding behaviour of goats in the early morning (EM = 7:00-8:30a.m.) and late morning (LM = 9:30-11:00a.m.) in response to their natural gastrointestinal nematode (GIN) infection status. Twelve female adult goats (37 ± 7.7kg live weight (LW); 5 ± 1years) with browsing experience in the tropical deciduous forest were divided into two groups (n = 6): INF group, with natural GIN infection, and non-infected (NI) group, dewormed with moxidectin (0.4mg/kg LW subcutaneous). Feeding behaviour (dry matter intake (DMI)) of two resource types (grasses vs. shrubs + herbs) was estimated by direct observation for 4weeks on two grazing moments (EM vs. LM). Environmental temperature and relative humidity at pasture level were measured twice weekly. The GIN egg counts and goats' LW were measured on days 0, 14 and 28. Temperature (mean ± standard deviation) at EM (26.2 ± 1.5°C) was lower than at LM (38.7 ± 1°C; P < 0.01). Humidity was higher on the EM (85.1 ± 2.6%) compared to LM (60.4 ± 5.6%; P < 0.01). Irrespective of the infection status, goats consumed similar amounts of grass and shrubs + herbs during EM (P > 0.05). On the other hand, the experimental groups consumed more grass than shrubs + herbs during LM (P < 0.05). The latter suggested prophylactic behaviours strategies to (a) avoid GIN infective larvae, (b) balance the protein:energy ratio of the diet and (c) avoid saturation of detoxification pathways for the secondary compounds consumed from shrubs + herbs. The constant consumption of shrubs + herbs during the study may have reduced the GIN egg count of the INF group.