Mountain Big Sagebrush Browse Decreases Dry Matter Intake, Digestibility, and Nutritive Quality of Sheep Diets

Abstract

A metabolism study evaluated the influence of increasing quantities (O-30% dry matter basis) of mountain big sagebrush (Artemisia trident&a ssp. vaseyana Rydb. Beetle) on dry matter intake and in vivo digestibility of wether diets. Diets consisted of band-harvested, coarse-ground and frozen current year's growth of mountain big sagebrush leaves and twig tips mixed with chopped native grass hay. Dry matter intake decreased from 93 to 23 g dry matter day" kg metabolic weight' and in vivo dry matter digestibility from 59 to 0% with increasing levels of sagebrush in the diet. With increasing levels of sagebrush in the diet, water, lignin, and nitrogen contents increased in the diet, but decreased iu the dung, while fiber components decreased in both the diet and dung. Total nitrogen intake decreased from 1.58+0.041 to 0.406+0.070 g day" kg metabolic weight', and nitrogen retention decreased from 0.80 g day-' kg metabolic weight-' with no sagebrush to a slight loss of nitrogen with 30% sagebrush in the diet. Mountain big sagebrush was not readily consumed by wethers when fed together with grass; as low as 10% sagebrush in the diet seems to adversely influence intake and digestibility. Therefore, when other more favorable forages are not available, sheep and other ruminants with similar physiological responses to mountain big sagebrush may not meet their nutrient requirements through increased sagebrush consumption.

Sagebrush ingestion by lambs: Effects of experience and macronutrients

“…Thus, we hypothesize terpenes set a limit on the amount of food lambs consumed (i.e., toxin satiation). This hypothesis is consistent with the observation that lambs eating sagebrush/grass diets limited terpenoid ingestion to 170 mg/kg metabolic weight/day (Ngugi et al 1995) and that toxins can limit the amount of foods lambs can ingest (Launchbaugh et al 1993, Wang andProvenza 1997).…”

“…Animals forced to eat a ration of 30% sagebrush show marked depression in in vivo dry matter digestibility (Ngugi et al 1995). Reduced microbial activity decreases digestibility of macronutrients and byproducts of fermentation (i.e., volatile fatty acids), all of which affect food preferences of sheep (Villalba and Provenza 1996, 1997a, 1997b, 1997c.…”

“…Low use of sagebrush is often attributed to its monoterpenoid content (Yabann et al 1986). Terpenoids depress in vitro digestion of sagebrush (Striby et al 1987) and wethers fed grass/sagebrush diets exhibit marked depression in in vivo digestibility (Ngugi et al 1995). Sagebrush can also be lethal to sheep (Johnson et al 1976).…”

Calibrating fecal NIRS equations for predicting botanical composition of diets

“…In the 1998 trial, frozen diets caused a small decrease of forage intake (Fraker 1999), which was associated with an increase in average H and greater deviation from unity of the slope (i.e,1.27 and 1.43 for the dry and frozen diets, respectively). Ngugi et al (1995) reported a much BW on the 0% sagebrush diet to 9 g/kg greater effect of percent sagebrush in the BW on the 30% sagebrush diet with a condiet on intake and digestibility for the comitant decline in apparent dry matter Wyoming trial than was reported for the digestibility of from 59 to -3% in this 1998 trial. Intake declined from 38 g/kg study.…”

“…Age, sex, or physiological status of the animal could affect fecal composition via the effect these factors have on intake and digestibility. Furthermore, the amount of sagebrush in the diet affects both intake and digestibility (Ngugi et al 1995), and these effects are greater for fresh compared to dried sagebrush (Fraker 1999). Typically 60% or more of ruminant feces is composed of metabolic products including bacteria and endogenous waste (Van Soest 1982).…”