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Title: Effects of winter stocker growth rate and finishing system on: I. Animal performance and carcass characteristics

item Neel, James - Jim
item Fontenot, Joseph
item Clapham, William
item Duckett, Susan
item Felton, Eugene E
item Scaglia, Guillermo

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2007
Publication Date: 7/20/2007
Citation: Neel, J.P., Fontenot, J.P., Clapham, W.M., Duckett, S.K., Felton, E.D., Scaglia, G. 2007. Effects of winter stocker growth rate and finishing system on: I. Animal performance and carcass characteristics. Journal of Animal Science. 85(8):2012-2018.

Interpretive Summary: Demand for high quality food products increased in recent years. Health conscious consumers include lean beef products in their diets, and grass-fed beef is imported in the United States to satisfy some of this demand. For some, grass finished beef is perceived as being more healthful (lean) and environmentally friendly from a production standpoint (low input production systems). In addition, one of the main problems in the beef industry as a whole is the ability to produce a consistent product. Defining components within the production system which influence this variability is important. Stocker performance on forages can vary greatly, from loss of body weight to exceptional gains and performance during the stocker period may influence meat quality. A multi-year, multi-location experiment was conducted with the objective to evaluate the effect of winter feeding regimes on subsequent pasture or feedlot finishing performance, and meat quality characteristics. With cattle finished to an equal time endpoint, winter rate of gain impacted finishing performance, final weight, carcass weight, dressing percent and carcass quality grade for both pasture and feedlot finished cattle. Results show cattle grown at the lowest rate during winter had a faster rate of gain during finishing, but weighed less and had lighter carcasses than those gaining at the fastest rate during winter. Low and medium winter treatments resulted in lower USDA quality. The results also show that with non-implanted pasture-finished cattle, a highly acceptable quality grade can be achieved. This information will be beneficial in both the development and modeling of conventional and pasture-finishing beef systems.

Technical Abstract: Angus-crossbred steers (n = 216) were used in a three-year study to assess the effects of winter stocker growth rate and finishing system on finishing performance and carcass characteristics. During winter months (December to April) steers were randomly allotted to three stocker growth rates: low (0.23 kg d-1; L), medium (0.45 kg d-1; M), or high (0.68 kg d-1; H). Upon completion of the winter phase, steers were randomly allotted within each stocker treatment to either a corn silage-concentrate or pasture finishing system. All steers regardless of finishing treatment were finished to an equal time endpoint to minimize confounding due to animal age or environmental factors. Upon completion of the finishing phase animals were harvested in two groups (one half of pasture and one half of feedlot cattle each time) and carcass data collected. Winter data were analyzed as a completely randomized design with winter treatment, pen replicate, year and winter x year interaction in the model. Finishing performance and carcass data were analyzed in a completely randomized design with winter growth rate, finishing system and the two way interaction as fixed effects. Year was considered a random effect and animal was the experimental unit for all comparisons. Winter stocker phase treatments resulted in differences (P < 0.0001) in final LBW, ADG and ultrasound LM area between all treatments for that phase. Pasture finished cattle had lower (P < 0.0001) final LBW, ADG, HCW, LM area, fat thickness, KPH fat, dressing percent, USDA yield grade and USDA quality grade. Winter stocker treatment influenced (P < 0.05) final LBW and HCW with L and M being less than H. Steers with L stocker gain had greater (P < 0.05) finishing ADG. Dressing percentage was greater (P < 0.001) for H than L, and USDA quality grade was higher (P < 0.05) for H than L and M. Carcass LM area, fat thickness, KPH fat and USDA yield grade were not influenced by winter rate of gain.