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Title: Relationships of cow age and initial cow body weight with calf and cow grazing season weight changes

Author
item GARRELTS, ASHLEY - UNIVERSITY OF WYOMING
item WAGGONER, JAMES - UNIVERSITY OF WYOMING
item HART, RICHARD - ARS RETIRED
item SMITH, MICHAEL - UNIVERSITY OF WYOMING
item Derner, Justin

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/5/2006
Publication Date: 2/9/2007
Citation: Garrelts, A., Waggoner, J.W., Hart, R.H., Smith, M.A., Derner, J.D., Hess, B.W. 2007. Relationships of cow age and initial cow body weight with calf and cow grazing season weight changes. Society for Range Management Meeting Abstracts. CDROM Traditions and Transitions #160.

Interpretive Summary:

Technical Abstract: The primary objective in a study implemented during 1975-2001 on northern mixed-grass prairie at the High Plains Grassland Research Station (HPGRS) near Cheyenne, Wyoming, was to evaluate long-term calf and cow grazing season body weight gain responses under 14 different management practices (e.g. the use of complementary forages, manipulation of stocking rates, implementation of a rotational grazing system, delaying the calving date, and early weaning). Specific objectives were to 1) determine the influence of both cow body weight and age on body weight gain of the cow, calf, and cow-calf unit under a traditional management system (March calving, September/October weaning, season long continuous grazing at moderate stocking(1.1 ha AUM-1), 2) determine if spring precipitation influenced the relationship between cow age, cow body weight and calf or cow weight change, and 3) determine if management practices influence the relationships between cow body weight or age and body weight change of the calf or cow. Cow and calf body weight change for each grazing season was calculated by subtracting initial weights from weaning weights. Calf weights were adjusted to 205-d weights. Years were classified as either, dry, average, or wet, as determined by April-May precipitation. Precipitation was found to interact with cow age and cow body weight to influence calf and cow weight gains. Lighter cows exhibited higher production efficiency (calf weight change divided by initial cow weight) in years classified as average, with heavier cows more efficient in the 6 wet and 3 dry years. Results from the management system study varied greatly and thus sound management implications can not be determined from this study and to say on management system is superior to another is risky. Environmental, range, and production conditions vary greatly, even within an ecosystem and thus no one system can be recommended over another.