Browsing Journal of Range Management, Volume 55, Number 1 (January 2002) by Subjects
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Intake and digestive kinetics of leaf and stem fractionsRuminally fistulated steers were used in a 4 x 4 Latin square to test effects of immature (vegetative) and mature (post reproductive) leaf and stem fractions from subirrigated meadow hay on organic matter intake (OMI), organic matter digestibility (OMD), and digestive kinetics. Hay was harvested 1 June (immature) and 1 October (mature), chopped into 3- to 5-cm lengths, then separated into leaf and stem fractions using a modified Clipper Cleaner Model Super 69D. Steers were provided ad libitum access to fractions and supplemented with urea so that diets were iso-nitrogenous. Particulate passage was determined using Yb labeled large hay particles [greater than or equal to 1.7-mm screen] and Er labeled small particles [< 1.7-mm and greater than or equal to 0.212-mm screen]. Samples were collected from the rumen, omasum, feces, and un-masticated diets for particle size determination. Particle size was determined using wet sieving techniques. Voluntary OMI of immature fractions (15.4 g kg(-1) BW) was greater (P < 0.05) than mature fractions (12.5 g kg(-1) BW). Within maturity OMI and OMD of leaves and stems were similar. Immature fractions had greater (P < 0.05) OMD (63.2%) than mature fractions (55.7%). Large and small particle passage rates were faster (P < 0.05) for immature fractions [3.2% hour(-1) (large) and 4.3% hour(-1) (small)] than mature [(2.3% hour(-1) (large) and 2.9% hour(-1) (small)]. Critical particle size for ruminal escape was less than or equal to 1.18 mm for both leaves and stems regardless of maturity. Differences in OMI and OMD between immature and mature fractions were explained by changes in structural components of the cell wall that made particles more resistant to mechanical and microbial breakdown.
Windrow grazing and baled-hay feeding strategies for wintering calvesManagement practices that lower livestock production costs are of interest to ranch enterprises. Windrow or swath grazing is a strategy where livestock directly graze windrow-stored forage, generally during a time when packaged hay or some other feed is provided. The objectives of this study were: 1) to quantify calf performance and forage intake and waste under windrow grazing (windrow) and bale-fed (bale) management strategies; 2) to quantify hay quality changes as affected by storage method and time; 3) to determine the effects of windrow coverage on subsequent meadow herbage yield and composition; and 4) to compare costs and returns associated with windrow and bale strategies. The forage source was wet meadow dominated by cool-season perennial species with alternating windrows baled and the remaining windrows left in place for direct grazing. Weaned steer calves were fed baled hay or grazed windrows during a November-January period each of 2 years. Windrow grazing calf gains were greater (P < 0.05) than bale-fed during the first year of the study but gains were similar during the second year. Greater weight gain for windrow calves during the first year was likely due to the presence of high quality regrowth that occurred after hay harvest. Diet samples collected from fistulated windrow animals in December contained 14.6% crude protein (CP) compared to 10.4% for hand-collected samples of windrows (P < 0.05). Crude protein content of windrow- and baled-stored forage was similar (10.6%, P > 0.05) during all sampling months (September-February). Crude protein content of standing (stockpiled) forage declined to 5.7% by February. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) were similar between windrow and standing storage treatments during all months and higher than bales from November through February. Herbage yield was 20% less in the area directly covered by windrows the previous fall and winter compared to the control (P < 0.05). However, only about 9% of the total area of a pasture is affected by windrow-coverage when 1-m wide windrows are created 11 m apart, resulting in an overall herbage yield reduction of 1.5%. Total forage production costs for the bale-fed strategy were about 63 ha(-1) (37%) higher than windrow grazing due to baling and bale moving costs. Feed costs averaged 0.16 head(-1) day(-1) for windrow and 0.30 head(-1) day(-1) for the bale strategy. When production data were applied to market prices for the previous 7 years, the mean net return ha(-1) for windrow exceeded the net return for the bale strategy by about 93 and the net return for a strategy that directly sold the hay by 174.