TABLE D-1 Typical Nitrogen and Sulfur Content of Animal Products

Product

N (%)

S (%)

Milk (% of milk weight)

0.5

0.023

Eggs (% of whole egg weight including shell)

1.78

0.16

Live Cattle

 

At <30% of mature weight

2.9

0.19

Growing (30-80% of mature weight)

2.6

0.17

Finished cattle

2.0

0.13

Mature breeding cattle

2.2

0.15

Live Swine

 

Nursing piglet

2.0

0.13

Growing (6-80% of mature weight)

2.3

0.15

Finished pig

2.0

0.13

Mature breeding pig

2.2

0.15

Live Poultry

 

Starters

2.6

0.17

Growers

2.5

0.17

Finished broiler

2.3

0.15

Layers and breeders

2.4

0.16

CALCULATIONS AND ASSUMPTIONS FOR TABLE D-1

Milk

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.

Eggs

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).



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