. "Appendix D: Nitrogen and Sulfur Contents of Animal Products and Live Animals -- Sample Excretion Predictions." Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs. Washington, DC: The National Academies Press, 2003.
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Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs
TABLE D-1 Typical Nitrogen and Sulfur Content of Animal Products
Milk (% of milk weight)
Eggs (% of whole egg weight including shell)
At <30% of mature weight
Growing (30-80% of mature weight)
Mature breeding cattle
Growing (6-80% of mature weight)
Mature breeding pig
Layers and breeders
CALCULATIONS AND ASSUMPTIONS FOR TABLE D-1
Approximately 93 percent of milk nitrogen is contained in true protein, while the remainder is found in nonprotein components. Therefore, milk crude protein can be calculated from milk true protein by dividing by 0.93 (NRC, 2001a). Milk nitrogen (N) can be calculated by dividing milk crude protein by 6.38 (USDA, 1941). Milk protein contains 2.4 g/16 g N as methionine and 0.87 g/16 g N as cystine (Hurrel et al., 1980). Methionine in a peptide is 21.8 percent sulfur (S), while cystine is 23.7 percent. Thus, the N:S ratio is 21.9 g/g, and sulfur in milk was determined by dividing the weight of nitrogen by 21.9.
For a medium egg (mass = 58 g), the edible portion is 51.6 g (Royal Society of Chemistry, 1991), which means that 11 percent of the whole egg is shell. The edible portion is 65, 50, 44 and 37 g for jumbo, large, medium, and small eggs, respectively (USDA, 2002b), or 73, 56, 49, and 42 g for eggs including shells. The edible portion is 12.4 to 12.6 percent protein and 0.18 percent sulfur (Royal Society of Chemistry, 1991; USDA, 2002b). Nitrogen is calculated as crude protein divided by 6.25 (USDA, 1941).