Browsing Rangeland Ecology & Management, Volume 60, Number 1 (January 2007) by Subjects
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Brangus Cow-Calf Performance Under Two Stocking Levels on Chihuahuan Desert RangelandCow-calf productivity on 2 lightly (25%-30% use) and 2 conservatively grazed pastures (35%-40% use) were evaluated over a 5-year-period (1997 to 2001) in the Chihuahuan Desert of south-central New Mexico. Spring calving Brangus cows were randomly assigned to study pastures in January of each year. Experimental pastures were similar in area (1 098 +/- 69 ha, mean +/- SE) with similar terrain and distance to water. Use of primary forage species averaged 28.8% +/- 4.3% in lightly stocked pastures and 41.8% +/- 4.4% on conservatively grazed pastures. Perennial grass standing crop (168.8 +/- 86 vs. 173.6 +/- 58.3 kg ha-1) and adjusted 205-day calf weaning weights (279.1 +/- 7.5 vs. 270.7 +/- 7.8 kg) did not differ among lightly and conservatively grazed pastures. Cow body condition scores in autumn, winter, and spring were similar among grazing levels as were autumn and winter body weights. However, cow body weights tended to be heavier (P < 0.10) in lightly grazed pastures relative to conservatively grazed pastures (524 vs. 502 +/- 9.7 kg) in spring. Lightly grazed pastures yielded greater (P < 0.05) kg of calf weaned ha-1 and calf crop percent than conservatively grazed pastures in 1998 due to destocking of conservatively grazed pastures during that year’s drought. Conversely, pregnancy percent tended to be greater (P < 0.1) in conservatively relative to lightly grazed pastures (92.6% vs. 87.7%); however, this advantage is explained by herd management as cows in the conservatively grazed pastures were removed during drought of 1998, avoiding exposure to the drought stress experienced by cows in the lightly grazed pastures. Nonetheless, pregnancy percents from both grazing treatments would be acceptable for most range beef production systems. Results suggest that consistently applying light grazing use of forage is a practical approach for Chihuahuan Desert cow-calf operations to avoid herd liquidation during short term drought.
Integrating Ranch Forage Production, Cattle Performance, and Economics in Ranch Management Systems for Southern FloridaThe presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha cow-1 on summer pastures and 0.93, 1.62, and 2.16 ha cow-1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility. Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant (P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves ha-1) was increased (P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch’s fixed cost structure.