• Effect of breed on botanical composition of cattle diets on Chihuahuan desert range

      Winder, J. A.; Walker, D. A.; Bailey, C. C. (Society for Range Management, 1996-05-01)
      Fecal microhistology was used to estimate botanical composition of samples taken from Hereford (N = 11), Angus (N = 11) and Brangus (N = 37) 3 to 5 year-old cows in 3 seasons (October, 1991 and January and July, 1992) and from Hereford (N = 10), Angus (N = 9) and Brangus (N = 34) calves in October. Breed differences in botanical composition of diets and relationships between dam and offspring botanical composition of diets were examined. Breed differences were observed for cows in all 3 seasons and for calves in October. Brangus cows showed greater preference (P < 0.05) for Sporobolus than Hereford cows in October, January, and July. Brangus cows also showed greater preference for Sporobolus than Angus cows in January and July. Brangus and Angus calves showed greater preference for Sporobolus than Hereford calves in October (P < 0.05). Brangus cows had a stronger preference for Yucca and total shrubs in January than either Hereford or Angus cows. Hereford cows and calves had stronger preference for Aristida than either Angus or Brangus in October (P < 0.05). Regression of October calf botanical components on dam botanical components indicated significant relationships for only 2 genera, Aristida (P < 0.01) and Sporobolus (P< 0.06). These data suggest that genetic composition of the animal is an important factor determining utilization of key plant species on Chihuahuan desrt ranges.
    • Influence of grazing management on intake and composition of cattle diets

      Hirschfeld, D. J.; Kirby, D. R.; Caton, J. S.; Silcox, S. S.; Olson, K. C. (Society for Range Management, 1996-05-01)
      A study was conducted to evaluate the influences of seasonlong and short duration grazing management on the botanical composition, chemical composition, and organic matter intake of cattle diets in the Northern Great Plains. Four sampling periods; spring, early summer, late summer, and early fall, were conducted during the grazing seasons of 1990 and 1991. Six ruminally cannulated crossbred steers were used to collect diets while 10 ruminally cannulated crossbred heifers were used to establish intake values. In each sampling period, diet collections were obtained from the steers, allowed to graze for 60 to 90 min in each of the treatments after total rumen evacuation. Intake was estimated using an indigestible marker and twice-daily fecal collections from 5 heifers under each of the 2 treatments. The primary constituent of cattle diets in both seasonlong and short duration treatments was graminoid which was consumed in slightly greater quantity under short duration management. Nutritional content of the diet was improved under short duration management. This is most notable with regard to nitrogen and digestibility, which were higher (P < 0.05) in the short duration treatment in 5 of the sampling periods. Organic matter intake trended higher for cattle under short duration management with 3 of the analyzed sampling periods showing differences (P < 0.10). These results suggest that livestock grazing under a properly implemented rotational grazing system may be presented with an opportunity to consume more of higher quality forage.
    • Monitoring mule deer diet quality and intake with fecal indices

      Hodgman, T. P.; Davitt, B. B.; Nelson, J. R. (Society for Range Management, 1996-05-01)
      Few studies have evaluated fecal indices for monitoring diet quality and intake of North American deer. We conducted 11 digestion trials with black-tailed (Odocoileus hemionus columbianus Richardson) and mule deer (O. h. hemionus Rafinesque) to examine relationships between several chemical constituents of deer feces (i.e., fecal nitrogen, fecal 2,6-diaminopimelic acid (DAPA), fecal neutral detergent fiber (NDF), fecal acid detergent fiber, and fecal acid detergent lignin) and dry matter intake, digestible energy, digestible energy intake, diet crude protein content, crude protein digestibility, and digestible crude protein intake. We developed regression equations to predict diet quality and intake and also evaluated 2 alternative methods (organic matter basis and neutral detergent fiber (ndf) basis) for quantifying fecal indices. Concentrations of DAPA, fecal NDF, and fecal N were the most precise for estimating diet quality and intake. Extracts from 5 of 11 diets precipitated only small amounts of protein and influence of tannins on protein digestion probably was slight. Quantifying fecal indices per unit organic matter and neutral detergent fiber in the feces was comparable to the standard dry matter basis and under some field conditions should improve their predictive ability. We believe our best equations are suitable for management purposes where diets are similar and intake and quality are believed to be within the ranges we documented.
    • Season and sex influences on botanical composition of cattle diets in southern New Mexico

      Mohammad, A. G.; Ferrando, C. A.; Murray, L. W.; Pieper, R. D.; Wallace, J. D. (Society for Range Management, 1996-05-01)
      We conducted a study in southern New Mexico to determine seasonal variation in botanical diet composition of cattle and to compare cow and steer diets. The climate and vegetation is typical of semidesert grassland. Fecal samples were obtained from a group of cows and steers during spring, summer, fall, 1989; winter and summer, 1990. Results showed that cattle diets were highest in grass content during spring (57%), summer (78%), and winter (54%), while fortes comprised the highest proportion of cattle diets during the fall (47%). Shrubs were moderately important during winter (18%). Dropseeds (Sporobolus spp.), black grama (Bouteloua eriopoda [Torr.] Torr.), threeawn species (Aristida spp.), and leatherweed croton (Croton pottsii [Klotzch] Muell. Arg.) were key forage species for cattle. The importance of these species varied with season, availability, physiological stage, and presence of other species. Differences between cow and steer diets varied with season. The relative similarity ranged from 70% (fall) to 90% (summer). The lower fall similarity compared to that in the summer might be related to physiological variation or past differences in grazing experience between cows and steers. For practical purposes, steer diets might generally be used to represent cow diets, but caution should be exercised during periods of low forage quality.
    • Soil water effects on growth and nutrition in upland pastures

      MacKlon, A. E. S.; Mackie-Dawson, L. A.; Shand, C. A.; Sim, A. (Society for Range Management, 1996-05-01)
      Normally the oceanic climate of Scotland maintains soils at low levels of soil water deficit. Field data for such a year are presented and compared with those for an unusually dry year, with the objective of assessing to what degree dry spells might limit herbage production in upland pastures. One meter square plots were sampled on selected dates on reseeded pastures growing on each of 3 cambisols, each derived from different parent materials. The swards were unfertilized and maintained at nominal heights of 2, 4, 7, and 10 cm by cutting every 2 or 3 weeks to manipulate growth and demand for P and N. Overall yield was 25 to 50% lower in the dry year compared with an average year. Peaks and troughs in growth rates, measured as yield at each cutting, and in P and N content, corresponded to changes in soil water deficit in the top meter of soil. The linear correlation coefficient between soil water deficit and growth rate was -0.894 (P = 0.001). Although there was some variation in volumetric water content between soils, soil water deficits were similar in all the cambisols. Yields and nutrient contents were generally similar for herbage harvested from the 2 soils having basic parent material (one a eutric and one a dystric cambisol) and lower on the dystric cambisol derived from schists. The effects of water content largely over-rode cutting treatments, demonstrating that dry spells occasionally occurring in the oceanic climate of Scotland can significantly affect grassland production.