Relationships between Performance, Intake, Diet Nutritive Quality and Fecal Nutritive Quality of Cattle on Mountain Range

Abstract

Correlations were developed between average daily gain (ADC), forage organic matter intake (INT), fiitula sample ln vitro organic matter digestibility (DID), futula sample nitrogen (DN), fecal sample in vitro digestibility (FID), and fecal sample nitrogen (FN) of cattle on forest and grassland range in northeastern Oregon. FN and FID were more closely associated with ADG and INT than DN or DID. Linear regression equations were developed between fistula and fecal samples for both N (rZ= S3)and ID (rj= .71). The inclusion of FN as an independent variable with FID improved the equation for predicting fistula sample ID (Rz = .83). Forage intake could not be well predicted from either FN or FID in either simple or multiple regression equations. The closer relationship between fecal sample nutritive quality and ADG compared to fistula sample nutritive quality and ADG is attributed to greater sampling precision for fecal nutritive quality. Fecal N and ID appear to be closely associate with DN and DID when grasses comprise most of the ruminant diet but this relationship may not hold when the diet is dominated by forbs and shrubs. Nutritive evaluation of feces shows potential for monitoring trends in ruminant diet quality and performance but much more research isneeded before these procedures can be applied. Trends in ruminant fecal nutritive quality are associated to varying degrees with trends in diet quality (Raymond 1948, Fels et al. 1959, Jarrige 1962, Arman et al. 1975, Hinnant 1979, Holloway et al. 1981) and animal performance (Erasmus et al. 1978, Gates and Hudson 198 1). Three studies have shown a close relationship between percentage nitrogen in the diet and percentage nitrogen in the feces of ruminant animals (Raymond 1948, Fels et al. 1959, J.L. Holechek and D. Arthun are assistant professor and graduate assistant, Department of Animal and Range Science, New Mexico State University, Las Cruces. N.M. 88003. Martin Vavra is professor of range nutrition. Oregon State University, Eastern Oregon Agricultural Research Center, Union. 97883. This report is Journal Article 822, Agricultural Experiment Station, New Mexico State University, Las Cruces 88003. JOURNAL OF RANGE MANAGEMENT Xi(6). November 1962 Hinnant 1979). A recent study indicates diet and fecal in vitro digestibility are associated (Holloway et al. 1981). Erasmus et al. (1978), in South Africa, found that trends in wild ungulate body condition were closely associated with trends in fecal nutritive quality. Gates and Hudson (198 1) accounted for 85% of the variation in daily gains of elk with fecal N concentration. Based on these studies it might be possible to monitor changes in ruminant condition and diet using fecal analysis. The study reported, herein, examined the relationships between cattle performance, intake, diet nutritive quality, and fecal nutritive quality on mountain range in northeastern Oregon during 3 grazing seasons. In vitro organic matter digestibility and nitrogen were the nutritive characteristics receiving evaluation.