Lack of Maternal Influence on Lamb Consumption of Locoweed (Oxytropis sericea)1,2

Locoweeds ( Oxytropis and Astragalus spp.) are toxic plants found on many rangelands. Preferences for locoweed are learned; livestock often initially reject the plant, but learn to eat locoweed after continued exposure. Maternal influences are important in shaping diet selection in young animals. We studied the influence of ewe consumption of locoweed on lamb selection of the plant. Twenty-four ewes were divided into three treatment groups (n = 8): 1) ewes conditioned to eat locoweed ( Oxytropis sericea) and avoid sodgrass ( Poa pratensis) (Loco+Sod-); 2) ewes conditioned to avoid locoweed and eat sodgrass (Loco-Sod+); and 3) ewes conditioned to eat sodgrass and not exposed to locoweed (Loco0Sod+). A control group (n = 8) was composed of orphan lambs with no maternal influence (Orphans). All ewes were exposed to locoweed and(or) sodgrass without their lambs for 1 wk. Lambs were exposed to either locoweed or sodgrass with ewes for 5 min/d for 6 d. After weaning, lambs were tested for preferences by offering both locoweed and sodgrass for 3 min/d for 5 d; lambs were then offered only locoweed for 5 min/d for 5 d. Sodgrass was preferred by lambs. Lambs in the Loco+Sodtreatment group tended ( P = .06) to take more bites of locoweed than lambs in the Loco0Sod+ group. Also, lambs in the Loco0Sod+ and Loco-Sod+ groups tended ( P = .07) to take fewer locoweed bites compared with Orphans. Even though these results tended towards significance, the magnitude of the effect was small. There were no treatment effects when locoweed was offered alone. Although exposure with the mother did not strongly influence lambs to eat (or avoid) locoweed, all lambs ate some locoweed during testing. Short-term maternal influence does not seem to be sufficient to condition a preference for locoweed in lambs.