- A series of four trials was conducted to evaluate activated
sewage sludge (AcSS) as a protein source. In the first trial the protein
efficiency ratio (PER) of sun-dried and auto-claved, sun-dried
AcSS was measured with rats. Growth of AcSS-fed rats was extremely
poor as compared to those rats fed casein, brewers yeast or cottonseed
meal. Autoclaving did not increase performance. These findings
indicate that the protein quality of AcSS is poor.
The second trial examined the effects of increasing levels of
AcSS (0, 30, 40, 50 percent) on growth rate, feed intake, sodium
pentobarbital sleeping times, organ weights and tissue metals accumulation,
in male Long-Evans rats. Average daily gain(g) for 30 days
was 5.6, 4.9, 5.1 and 4.8 for 0, 30, 40 and 50 percent AcSS.
Pentobarbital sleeping time(35 mg pentobarbital/kg body weight) was
reduced (P<.01) in the 50 percent AcSS group as compared to the 0 percent
AcSS group indicating stimulated hepatic drug metabolism. Liver
weight as percent body weight was increased (P<.05) in the 40 and 50
percent AcSS groups. Tissue mercury, lead and cadmium in the liver,
kidney, heart and muscle of the 50 percent AcSS-fed rats were 0.10,
0.11, 1.01; 0.78, 0.13, 1.22; 0.23, 0.08, 0.67 and 0.05. 0.03, 0.33
ppm respectively. The diet contained 3.2, 5.2 and 217 ppm mercury, cadmium and lead. These results indicated hepatic metabolism of
toxic constituents in AcSS.
The performance of zero and 30 percent AcSS-fed rats was assessed
over three generations. Birth weight, weaning weights, average daily
gain, feed intake and tissue heavy metals accumulation were studied.
Birth weights were greater (P<.05) for the 30 percent AcSS -'fed groups;
apparently average litter sizes were slightly less. Post weaning
average daily gain was lower (P<.05) for the F3 male and female 30
percent AcSS-fed rats than the zero percent AcSS-fed rats. Performance
and tissue heavy metals accumulation in this and the previous trial
are sufficiently low that AcSS appears to have minimal use as a feed
A fourth trial was conducted to determine the general chemical
nature of the toxic constituent(s) of AcSS through pentobarbital
sleeping times. Ashed and solvent extracted preparations of AcSS
were incorporated into a diet at a level equivalent to 50 percent
unaltered AcSS. Zero percent and 50 percent unaltered AcSS diets were
included. Pentobarbital sleeping times (35 mg pentobarbital/kg body
weight) of the groups fed ashed and solvent (hexane, ether) extracted
AcSS were not different (P<.05) than the zero percent AcSS -'fed group.
These results indicate the major toxic factor(s) in AcSS to be of an
These trials indicate because AcSS is a low quality protein with
substantial quantities of heavy metals it is not likely to have
application as a protein supplement for non-ruminant animals,
The solvent extracted meal from a potential industrial oil seed
crop, Limnanthes, was evaluated as a protein source in three trials, In the first trial the protein quality was measured through a PER.
Unaltered Limnanthes meal is unacceptable as the sole source of
protein in the monogastric diet. Limnanthes with the goitrogens
extracted and the endogenous enzyme inactivated was shown to be a
protein equal to that of cottonseed meal.
Protein digestibility in Limnanthes was examined in a second
trial. A 60 percent digestibility coefficient indicates likely
interference of the fibrous hull fraction with protein digestibility.
In a thrid trial the response of rats to increasing levels (0, 5,
10, 15, 20, 25, 30 and 50 percent) of an enzyme inactivated Limnanthes
mealwere examined. Rats fed 20 percent Limnanthes had average daily
gains and feed intake not different (P<.05) from the zero percent
Limnanthes-fed rats. At the 25, 30 and 50 percent levels daily gains
and feed intake were lower (P<.05) in the 25, 30 and 50 percent
Limnanthes meal is a poor quality protein when used alone in
non-ruminant diets. Protein digestibility appears to be reduced by
the hull fraction. Adequate growth performance with no apparent side
effects is obtained in rats with dietary levels of 20 percent or less.
Low saponin alfalfa was evaluated as a protein source for nonruminants.
The contribution of saponin to the negative effects of
drying on the quality of alfalfa was examined in trial one. Average
daily gains of rats fed air-dried, low saponin alfalfa were higher
(P<.05) than rats fed freeze-dried low and high saponin alfalfa.
These results indicate saponins do not undergo heat stimulated reactions
which decreases the palatability of alfalfa, Freeze-drying
appears to decrease the nutritive value of alfalfa. In a second trial the growth inhibitory effect of high saponin
alfalfa was studied through a pair-feeding regime. Low saponin
alfalfa-fed rats had daily gains not different (P<.05) than the high
saponin alfalfa-fed group with which they were pair-fed, results which
indicate growth inhibition is largely due to reduced feed intake.
The level at which a low or high saponin alfalfa diet would be
rejected in favor of a control diet was examined. Rats consistently
preferred the control diet. Rabbits rejected low saponin at the five
percent level and high saponin at the 15 percent level. These results
indicate rabbits have a preference for bitterness whereas rats do not.
In a second palatability study, intake of high saponin and low
saponin alfalfa was examined. At all levels rats chose the low saponin
diet over the high saponin diet. Rabbits rejected the high saponin
diet at the 20 percent level, results which confirm the species difference
of the previous study and indicate saponin to affect diet acceptability
in the rat.
The growth response of pigs to high and low saponin alfalfa diets
was measured. Pigs on the low saponin diet had growth rates not different
(P<.05) than the controls. The high saponin groups had growth
rates different (P<.05) from the low saponin and control group. There
were no differences (P<.05) in feed intake or feed efficiency. Dietary
saponin is a significant factor in growth inhibition in pigs.