Date of this Version
The Professional Animal Scientist (2001) 17:183-190
Four feeding regimens were evaluated in two different outside facilities [tree windbreak provided (SP) vs no wind protection provided (NP)] over two winter seasons. Feeding regimens were 1) 7.5% (DM basis) alfalfa hay (AH) diet (Low- Low); 2) 15% (DM basis) AH diet switched to a 7.5% (DM basis) AH diet under cold stress conditions (High-Low); 3) 7.5% (DM basis) AH diet switched to a 15% (DM basis) AH diet under cold stress conditions (Low-High); and 4) 15% (DM basis) AH diet (High-High). For feeding regimens High-Low and Low- High, cold stress was determined by use of a model, based on weather conditions and previous DMI, to predict lower critical temperature. Cattle fed in facilities with SP tended to perform better under a Low-Low feeding regimen; cattle fed in facilities with NP tended to benefit from the extra energy provided by switching to a lower fiber diet (High-Low feeding regimen) during cold stress. Across both facilities, the 5-d moving averages of wind chill index (WCI) and WCI >800 units had the best correlation with change in DMI. All diets except the High-High diet displayed significant linear relationships with increases in DMI and climatic variables in the NP facility, whereas cattle fed only the High- High diet displayed significant relationships in the SP facility. Heat production associated with the added fiber does not appear to be greater than that from added grain. Switching feedlot cattle, under cold stress, to higher fiber diets was not beneficial.