Backgrounding methods for growing beef cattle and strategies for incorporating alternative feedstuffs into diets of finishing beef cattle.

University of Minnesota Ph.D. dissertation. May 2011. Major: Animal sciences. Advisors: Dr. Alfredo DiCostanzo and Dr. Ryon Walker. 1 computer file (PDF); xiv, 211 pages.Volatile commodity and cattle markets present challenges for profitable beef production. Four experiments were conducted to evaluate backgrounding methods for growing cattle and utilizing alternative feedstuffs in finishing diets to improve feedlot performance and efficiency. Experiment 1 evaluated the effectiveness of grazing stockpiled and swathed annual ryegrass as backgrounding systems on forage quality and beef stocker cattle performance. Results of experiment 1 suggest grazing stockpiled and swathed annual ryegrass may be viable backgrounding systems; however, forage maturity and winter weather conditions may reduce forage quality and accessibility to levels that can limit stocker cattle performance. Experiment 2 evaluated the effects of reproductive status (spayed vs. intact heifers supplemented with melengestrol acetate) and terminal implant strategy (moderate vs. aggressive) on beef feedlot heifer performance during backgrounding and finishing phases and on carcass characteristics. Results of experiment 2 suggest intact heifers supplemented with melengestrol acetate had greater performance during backgrounding; however, use of moderate or aggressive terminal implant strategies may allow similar performance during finishing and comparable carcass characteristics between spayed and intact beef feedlot heifers. Experiment 3 evaluated the effects of partially replacing dry-rolled corn in traditional corn-based finishing diets with either 35% conventional dried distillers grains plus solubles or 35% high protein dried distillers grains on beef steer feedlot performance and carcass characteristics. Results of experiment 3 suggest that although overall feed intake tended to be reduced, high protein dried distillers grains may successfully replace conventional dried distillers grains plus solubles or up to 35% of dry-rolled corn in finishing beef cattle diets. Experiment 4 evaluated effects of supplemental manganese in high-sulfur feedlot diets containing dried distillers grains plus solubles on in vitro and in vivo ruminal fermentation and hydrogen sulfide gas production. In vitro results of experiment 4 suggest that 1,000 ppm manganese in high-sulfur diets appeared to release less total hydrogen sulfide gas than 0 or 500 ppm manganese; whereas in vivo results suggest beef steers consuming 1,000 ppm manganese may have a less acidic ruminal environment prior to feeding to result in a tendency for reduced average ruminal hydrogen sulfide concentration