Abstract

A study was conducted on foothills rangeland to determine whether grazing patterns differed among cow breeds and to determine whether there was a relationship between individual grazing patterns and performance of beef cows. Hereford (HH), Tarentaise (TT), 3/4 Hereford x 1/4 Tarentaise (3H1T), 1/2 Hereford x 1/2 Tarentaise (HT), and 1/4 Hereford x 3/4 Tarentaise (1H3T) cows were observed during the summers of 1997 (n = 183) and 1998 (n = 159).

Locations of individual cows were recorded two to three times per week during 1.5- to 2.5-h periods in the morning by observers on horseback. Statistical models included cow breed, age, and nursing status. Data from each year were analyzed separately. During 1997 and 1998, non-lactating cows were located at greater (P < 0.05) vertical distances from water than lactating cows. In 1998, nonlactating cows used steeper (P < 0.05) slopes than lactating cows.

However, nonlactating cows did not travel as far horizontally from water (P < 0.05) as lactating cows in 1997. Younger cows (3 yr) traveled further (P < 0.05) from water both vertically and horizontally than older cows (5+ yr) in 1997, but not during 1998. Tarentaise and 1H3T cows were observed at greater (P < 0.05) vertical distances from water than HH cows during both years of the study. During 1998, TT and 1H3T cows used steeper (P < 0.05) slopes than HH cows.

Using residual correlations, there were no consistent relationships between topographic aspects of individual grazing locations and cow weight, height, and body condition score. In 1997, cows with earlier calving dates and correspondingly heavier calf weaning weights used areas that had greater vertical distances to water; however, in 1998 there were no relationships (P > 0.05) of calving date and weaning weight with cow location.

During both years, pregnant and non-pregnant cows used terrain similarly (P > 0.05), which suggests that cow reproductive performance was not related to terrain use. Grazing patterns in foothills rangeland varied among cow breeds. Performance of cows that used more rugged topography was similar to cows using gentler terrain.

Introduction

The distribution of grazing livestock is an important facet of proper rangeland management (Vallentine, 1990). If cattle are not dispersed evenly, preferred areas are overgrazed and other areas are underused. Developing water, salting, supplementing, herding, and fencing have been successfully used to modify livestock grazing distribution (Skovlin, 1957; Cook, 1966; Bailey and Welling, 1999). Another suggested approach for improving livestock grazing distribution is to cull animals with undesirable grazing patterns and to select animals with desirable grazing patterns (Roath and Kruegar, 1982; Howery et al., 1996, 1998). Over time, the selected herd might use rugged and varying topography more evenly. Howery et al. (1996) found that some cows preferred upland areas in an Idaho mountain pasture whereas others spent more time in riparian areas. Livestock producers with extensive rangeland pastures could use breeds that travel further from water or use steeper slopes to improve uniformity of grazing. Herbel and Nelson (1966) found that Santa Gertrudis cows traveled further than Herefords.

An important consideration when evaluating the feasibility of a selection program for grazing distribution is the relationship between animal performance and spatial grazing patterns. If cows that prefer gentle terrain near water raise calves with heavier weaning weights than cows using steeper terrain and areas farther from water, then a selection program for improved grazing distribution may not be practical. Researchers have spent little, if any, time evaluating the relationship between where cows graze in rugged topography and their corresponding performance. The objectives of this study were to determine whether there were differences among cattle with Hereford, Tarentaise, and Hereford x Tarentaise breeding and to examine the phenotypic relationships between where cows graze on foothills rangeland and their performance.

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2001