The use of different nutritional strategies and mathematical models to improve production efficiency, profitability, and carcass quality of feedlot cattle

摘要

Forty eight crossbred steers (BW = 296 ???? 16.7 kg) were fed four dietarytreatments for 56 d: AL-LS (low starch diet fed ad libitum for a rate of gain of 1 kg/d),AL-HS (high starch diet fed ad libitum), LF-HS (a limit fed high starch diet designed tobe isocaloric with AL-LS), and AL-IS (a diet fed ad libitum for the midpoint dailyenergy intake between AL-LS and AL-HS). On d 57 all steers were placed on AL-HSfor finishing until d 140. Steers that consumed more total energy (AL-HS and AL-IS)throughout production achieved greater carcass fatness in the end of the 140 d period,although these responses were difficult to evaluate via real-time ultrasoundmeasurements. No differences in insulin and glucose kinetics were observed. Datasuggested that energy source may influence energy partitioning during the growingperiod, but these effects may be overcome by differences in energy intake. Highermarbling scores (AL-HS and AL-IS) rewarded higher grid values and greater premiums,which increased profitability. This data set was also used for a model evaluation that showed that mathematical models (CVDS and NRC) were able to explain most of thevariation in individual feed requirements of group- fed growing and finishing cattle.Another data set was used for evaluation of a decision support system Cornell NetCarbohydrate and Protein System (CNCPS) as a tool to minimize nutrient excretionfrom fed cattle. One-hundred eight-four group- fed steers were fed a 13% crude protein(CP) diet until reaching 567 kg of BW, when their diets were either maintained at 13%or reduced to 11.5% or 10% CP. Data from the second half of the experiment weremodeled to predict urinary, fecal, and total N excretion. As dietary CP decreased from13 to 11.5%, the model indicated a total N excretion of 16%. An even greater reductionin total N excretion (26%) occurred when dietary CP was decreased from 11.5% to 10%.The overall decrease from 13 to 10% CP resulted in a reduction of total N excretion by38%. Data suggest that decision support sys tems can be used to assist in balancing dietsto meet environment restriction.