Analyses

Using the default values in the spreadsheets, one can readily see that on a kg primary product/MJ fossil energy basis, milk production is most efficient, followed by eggs, poultry meat, swine, beef and sheep (Table 5). Considering an energy basis, however, places poultry meat first (presumably due to the water content of milk). Moreover, inclusion of byproducts of slaughtering and food processing also changes the rankings, with dairy still in front, followed by poultry meat and eggs, sheep, beef and swine last. A number of factors influence the efficiency of each production system.

First, the biology of the animal is paramount. As seen in Table 6, livestock production is the largest component in the animal product chain, in contrast to the situation with cereals (Leach, 1976). Production required from 79% (poultry meat) to 94% (eggs) of the total cost of animal products up to the moment of consumption. Of course, these values will change depending on the actual inputs, but the importance of productive efficiency will remain. Within the costs of production, pasture and feed are the largest components, comprising from 40 to 78% of the total energy costs of the systems (Table 7). Of the feed costs, poultry (with their high reproductive efficiency) need only 7% to support the breeding flock, whereas beef cattle need over 50% just to maintain the cow herd.

Table 5. Efficiency of fossil energy use in animal production – default systems
 

Products	Poultry meat	Eggs	Swine	Dairy	Beef	Sheep
Primary only, MJ·kg-1	.028	.033	.022	.063	.019	.016
" " , J·J-1	.414	.233	.320	.204	.284	.238
Primary + byproducts, MJ·kg-1	.036	.035	.023	.063	.026	.029
" + " , J·J-1	.525	.268	.342	.204	.379	.438

Second, processing costs vary widely, due to differences in processes and also in scale. Egg processing requires little fossil energy, but the meats require more energy. The processing costs for dairy given in Table 6 are low, since the default is fluid milk. Changes in the product mix (e.g., to spray-dried milk powder) would increase this cost. Transportation and storage are relatively small contributors to overall costs, but preparation can be expensive. Costs of preparation of dairy products are very low, those of meats are higher. Poultry meat is highest, due to the assumption that the entire carcass (including skin and bone) is cooked.

Table 6. Components of fossil energy use in animal production – default systems
 

Component	Poultry meat	Eggs	Swine	Dairy	Beef	Sheep
Production	79.3	93.5	85.4	88.7	86.8	79.0
Processing	9.8	1.5	10.3	7.5	8.5	17.0
Transportation	0.5	0.7	0.3	2.4	1.0	0.9
Storage	0.5	1.3	0.2	1.2	0.4	0.3
Preparation	9.8	3.0	3.8	0.2	3.4	2.8

Table 7. Contributions of feed and the reproductive stock to total fossil energy costs
 

Component	Poultry meat	Eggs	Swine	Dairy	Beef	Sheep
Feed as % of total	40	54	55	78	78	73
Reproductive stock as % of feed costs	7	-	17	-	51	36