Browsing Rangeland Ecology & Management / Journal of Range Management by Authors
Breed and stocking rate effects on Chihuahuan Desert cattle productionWinder, J. A.; Bailey, C. C.; Thomas, M.; Holechek, J. (Society for Range Management, 2000-01-01)Productivity of Barzona, Brangus, and Beefmaster cattle was evaluated on conservatively (n=2) (40 ha AU-1) and moderately (28.5 ha AU-1) stocked pastures (n=2) in the Chihuahuan Desert of south-central New Mexico. Equivalent numbers of suckled, first-calf heifers of each breed (n=31) weighing 333+/-11 kg were randomly assigned to the study pastures in the spring of 1992. Pastures were grazed continuously and herd productivity data were collected from 1992-1994. In late August 1994, all pastures were destocked due to onset of severe drought. No effect of breed (P > 0.10) was detected in the analyses, so data were pooled across breeds and compared between the stocking rates. Calf crop percentages (1993, 1994) were higher in conservative than moderate stocked pastures (82 vs 62%, respectively, P < 0.01). Financial analyses standardized to a hypothetical medium size (8,094 ha) New Mexico Chihuahuan Desert cattle range showed net returns per ha did not differ (P > 0.10) between stocking rates. However, the main effect of year and stocking rate X year interaction were significant (P < 0.05). These analyses suggest that the drought in 1994 lowered returns per ha compared to 1993 when precipitation was near average and that conservative stocking may present less financial risk than moderate stocking when drought occurs. These data are consistent with other studies from arid and semi-arid rangelands demonstrating that conservative stocking can give financial returns from cattle production equal to or greater than those from moderate stocking.
Effect of breed on botanical composition of cattle diets on Chihuahuan desert rangeWinder, 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.
Genetic aspects of diet selection in the Chihuahuan desertWinder, J. A.; Walker, D. A.; Bailey, C. C. (Society for Range Management, 1995-11-01)Fecal microhistology and chemistry were used to evaluate botanical composition and quality of diets selected by Brangus cattle grazing Chihuahuan desert range in 3 seasons; fall: October, 1991; winter: January, 1992; and summer: July, 1992. Fecal samples were collected from 100 head in fall (58 2-8 year cows and 42 calves), 53 head (2-8 year-old cows) in winter, and 44 head (2-8 year-old cows) in summer. Paternal half sib analyses were used to estimate genetic and phenotypic variances and heritability estimates. Heritability is the proportion of total (phenotypic) variation which is due to additive genetic effects. The effect of sire within age was observed for percentage of Aristida spp. (P= 0.01), Sporobolus spp. (P= 0.09), total grasses (P = 0.02), Croton pottsii (Klotzsch) Muell.-Arg. (P= 0.03), and total forbs (P =0.02) in fall diets. The number of grass species in diets was also affected by sire (P=0.03). Heritability estimates were 0.87, 0.51, 0.78, 0.76, and 0.79 for percentages of Aristida spp., Sporobolus spp., total grasses, Croton pottsii, and total forbs, respectively. Heritability estimates for number of grass and forb species in fall diets were 0.68 and 0.26, respectively. Heritability estimates for winter samples were 0.40, 0.00, 0.37, and 0.27 for percentages of Sporobolus spp., total grasses, Yucca elata Engelm., and total shrubs, respectively. Heritability estimates for the number of grass and total species observed in winter diets were 1.11 and 0.47, respectively. Heritability estimates for percentages of Bouteloua spp., total grasses, Croton pottsii, Dalea spp., and total forbs in summer samples were 0.20, 0.55, 0.58, and 0.46, respectively. Heritability estimates for the number of grass and total species in summer diets were 0.49 and 0.79, respectively. These data suggest that genetic composition of beef cattle may affect diet selection under Chihuahuan desert conditions.