title: Simulation of lean lamb production systems.
abstract: A series of simulations were performed to evaluate the effects of mature size (WMA; 60, 70, 80 and 90 kg), slaughter weight (SW; 55, 60 and 65 kg) and three diets fed to feedlot lambs. Rations included a traditional diet (C2L) or placing weaned lambs on alfalfa for either 30 (A30) or 60 (A60) d before placing them on the C2L diet (A30-C2L and A60-C2L). Two lamb pricing schemes were used in the financial analysis of the biological results: sale price based on weight with or without adjustment for carcass fat. Placing lambs on alfalfa pasture increased ownership by 22 d on average compared to C2L. As WMA and SW increased, ownership increased from 3 to 11 d. Across nutritional treatments, fat decreased by 5.8 to 9.0% as WMA increased from 60 and 90 kg. When market lambs were priced on weight, net returns per lamb were greatest for A30-C2L or A60-C2L ($2.34 and $5.21, respectively above C2L) and for greater SW ($4.77 and $7.16 greater for SW 60 and 65 kg than for SW 55). The combination WMA of 90 kg, a SW of 65 kg and nutritional treatment of A60-C2L proved most profitable. However, when sale price was discounted for excessive fat content, the combinations WMA of 60 or 70 with a SW of 65 and A60-C2L were most profitable. The rank correlation between biological efficiency (weight gain/dry matter feed consumption) and net return, when sale price was based on weight, was found to be -.51. This was because lambs slaughtered at lighter weights had high biological efficiencies but low net returns due to a negative price margin. With negative price margins but positive feeding margins, net returns are greatest for heavier, fatter lambs fed longer.
authors.affiliation: U.S. Sheep Experiment Station, Dubois, ID 83423.
authors.forename: H D
authors.initials: HD
authors.lastname: Blackburn
authors.forename: G D
authors.initials: GD
authors.lastname: Snowder
authors.forename: H
authors.initials: H
authors.lastname: Glimp
mesh_terms: D000273:Adipose Tissue / Q000254:growth & development; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D003198:Computer Simulation; D004435:Eating; D008954:Models, Biological; D012756:Sheep / Q000254:growth & development*