Determining the Cost Of Energy
The key to maximising feedlot performance is to maximise animal daily energy intake. This is achieved through maximisation of dietary energy through use of available ingredients. Therefore, when reviewing rations or feedstuff options it is best to look at each item on a cost of dry matter energy basis, what may be the cheaper option may not necessarily be cheaper, in terms of cost of feeding the animal.

Item Ration A Ration B
Ration Cost ($/t) $350 $400
Dry Matter % 85% 90%
Ration Cost DM basis ($/t) $350*0.85 = $412 $400*0.9 = $444
Metabolisable Energy DM Basis (MJ/kg) 10.5 MJ/kg 12.5 MJ/kg
Energy Cost $/MJ 412/10.5/1000 = $0.0392 $444/12.5/1000 = $0.0355

As shown in the table above, while ration A appears cheaper, due to lower DM and energy value, it is in fact more expensive on a cost of energy basis ($/MJ). In terms of animal performance cattle on ration A would need to consume more feed for the same level of performance as ration B, and most likely will not perform as well as the cattle on ration B. This is highlighted in the table below where performance projections were run on the 2 rations feeding a 300 kg steer through to 400 kg.

Cattle Performance Parameters
ADG 1.29 1.88
DMC 6.93 4.69
DOF 77 53
As Fed kg/hd/d 10.5 9.8
As Fed Conversion 8.15 5.21

Production Costs A B
Feed Cost of Gain $/kg $ 2.85 $ 2.08
Feed Cost $/d $ 3.69 $ 3.92
Total Feed Cost $/hd $ 285.25 $ 208.27

As shown the steers consuming ration B are projected to perform significantly higher due to the higher energy content of ration (1.88 kg/hd/d versus 1.29 kg/hd/d). Due to the higher level of performance, the cattle on ration B can be fed for a shorter period at 53 days versus 77 days for steers on ration A. It is also highlighted that the cattle on ration B will have a lower feed consumption to achieve this performance, at 9.8 kg/hd/d versus 10.5 kg/hd/d for ration A.

Because of the better performance, lower daily feed intake, and less days on feed it is therefore cheaper across all measures (except for $/d; cost per head per day), to feed the more expensive ration B. This is best represented in a lower cost of gain at $2.08/kg gained for ration B against $2.85/kg for ration A, and overall cost of feeding the animal which was $208/d for ration B, against $285/hd for ration A. This is despite ration B costing $50/t more.

Philip Dew BRurSc MS
Consulting Nutritionist