• Cattle preferences for a hybrid grass: chemical and morphological relationships

      Truscott, D. R.; Currie, P. O. (Society for Range Management, 1989-01-01)
      Forty-six clonal lines of a hybrid cross between Pseudoroegneria spicata [Pursh.] Scribn. and Smith × Elytrigia repens [L.] Beauv. were used to evaluate the influence of various chemical and morphological characteristics on cattle preference. Variables examined included total carbohydrates as well as several individual sugars, silica, nitrogen, moisture, leaf and growth form, phenology and plant height. In 3 of 4 trials, over 60% of the variation in preference as measured by bite counts was accounted for in the analyses. However, dominant factors controlling preference varied from trial to trial. Predictive equations developed for each trial (N=46) produced R2 values which ranged from 0.53 to 0.81. Common variables that influenced predictions included basal area, phenology, nitrogen, leaf score, and digestibility. Basal area was the most important single variable positively related to preference with an R2 value of 0.70 over all trials. Individual sugar analyses were not significantly (P>0.05) related to bites for most trials but became important from mid-June to mid-July. Equations which included sugar analyses (n=20), accounted for 73 to 87% of the variation in bites. However, basal area and phenology were the dominant variables in these equations. Therefore no single equation could be used to accurately predict preferences.
    • Factors affecting dietary preferences for genotypes of a hybrid wheatgrass

      Truscott, D. R.; Currie, P. O. (Society for Range Management, 1987-11-01)
      Interspecific hybridization of grasses represents a valuable plant breeding procedure for developing new species with superior grazing value for livestock. Evaluations were made of the hybrid cross between quackgrass (Elytrigia repens [L.] Beauv.) × bluebunch wheatgrass (Pseudoroegneria spicata [Pursh.] Scribn and Smith) to determine how animal preferences for these hybrids were influenced by grazing season and year. Significant differences in the preference shown by steers as measured by bite counts in 1981 and percent utilization (P<0.01) in 1982 existed among the 46 clonal lines for each of the 2 successive years. Preference rankings for lines selected the first year were not identical to those selected a second year although lines with high preference rankings the first year were generally preferred the second year. A clonal line, designated line 30, was most preferred in 7 of 8 subtrials in 1981 and ranked in the top 3 preferred plants in all trials in 1982. There was a 4-week period in early summer when preference differences were minimal. It was attributed to the abundant regrowth on all lines at this time and was found to have a significant (P<0.01) effect on steers' dietary choices.