The kinetics of ruminal

degradation of dry matter, crude protein and ether extract were

determined for fish, meat and bone, and poultry meals. These

meals of animal origin showed characteristics proper of the

species of origin, not only in the soluble fraction but also in

the rates of ruminal degradability of the potentially degradable

fraction. Based on the results of degradation after 48 hours of

ruminal incubation, the true digestible contents of the protein

and the digested ether extract were determined biologically,

making the measurement of the total digestible nutrients, and

the concentration and net rate of digestible energy and feed,

more precise than determinations by chemical methods. The

concentrations of energy for milk production was 2.02, 1.66,

and 2.60 Mcals/kg for fish, meat and bone, and poultry meals,

respectively. The fraction of soluble protein (A) was high in

fish meal (75.29%), intermediate in meat and bone (46.83%),

and low in poultry (25.75%), with a degradable fraction (B) of

10.62, 27.66, and 42.06%, along with an insoluble fraction (C)

of 14.09, 25.51, and 32.19%, respectively. The degraded

protein in the rumen was 83.23, 66.25, and 51.98% in the

same order cited above. The contents of crude protein

effectively retained by the animals during the whole digestive

process were 53.29, 51.86, and 42.05% for fish, meat and

bone and poultry meals, respectively.

Keywords: Net energy, true protein, animal feeds, animal source.