Age and Body Condition of Goats Influence Consumption of Juniper and Monoterpene-Treated Feed

Abstract

Redberry juniper (Juniperus pinchotii Sudworth) is an invasive, evergreen tree that is rapidly expanding throughout western and central Texas. Goats will consume some juniper on rangelands; however, intake is limited. The objective of our research was to determine how the age and body condition of goats influence their consumption of juniper and an artificial feed containing 4 monoterpenes. Two separate experiments were conducted. Experiment 1 examined the intake of redberry juniper foliage and used 39 goats either young (2 yr) or mature (> 6 yr). One-half of each age group was fed appropriate basal rations to reach either a high (HBC) or low body condition (LBC). Goats in LBC ate more (P<0.01, 8.6g kg-1 body weight [BW] +/- 0.7 SE) juniper than those in HBC (2.3 g kg-1 BW +/- 0.3 SE), and young animals consumed more (P < 0.05, 7.2 g kg-1 BW +/- 0.7 SE) juniper than mature goats (3.9 g kg-1 BW +/- 0.5 SE) across body condition treatments. In experiment 2, 36 goats, either young (2 yr) or mature (> 6 yr) and in either HBC or LBC, were offered a synthetic ration treated with 20.8 g kg-1 of 4 monoterpenes found in redberry juniper. Goats in LBC ate more (P < 0.01, 25.3 g kg-1 BW +/- 1.0 SE) of the terpene-treated feed than those in HBC (17.5 g kg-1 BW +/- 0.7 SE), and young animals ate more (P < 0.05, 22.5 g kg-1 BW +/- 0.8 SE) than mature goats (20.3 g kg-1 BW +/- 0.8 SE) across body condition treatments. Total intake as a proportion of body weight was also affected by body condition. Age and body condition are important factors that influence intake of chemically defended plants. A better understanding of how these attributes affect diet selection will aid livestock producers in improving grazing management.