Results and Discussion
Effects of substituting soyhulls for corn on lamb performance are presented in Table 2. Substituting soyhulls for corn at 1/3 of the diet resulted in a 13% increase (P < 0.01) in DM intake, but did not increase daily gains. The smaller amount of corn-diet needed to achieve the same gains as occurred with the soyhull diet suggests that soyhulls had less net energy than corn in this circumstance. When corn and soyhulls were included at 2/3 of the diet a similar response was observed. Lambs fed corn-based diets ate 20% less feed and gained 14% faster than those fed soyhull-based diets (P < 0.01). It seems apparent, that at both inclusion levels, soyhulls provided less net energy than corn. Any positive associative effects of soyhulls or negative associative effects of corn when fed with alfalfa meal were over ridden by the inherent energy content of these feeds. The combination diet containing one-third of each ingredient performed in an intermediate fashion. When soyhulls were substituted for half the corn in the 1/3 alfalfa:2/3 corn diet, intakes went up 8% and gains dropped 8% (P < 0.05). Because lambs fed 2/3 corn gained the fastest, they required less (P < 0.01) time on feed. They had the lowest total feed intake and their feed costs were $1.66 to $4.29 lower than for lambs fed the other diets.
In summary, replacing all or most of the corn in a lamb finishing diet with soyhulls reduced profitability. This occurred in diets where the roughage source was alfalfa meal and there was a $16.80/ton spread in price between soyhulls and corn (corn was priced at $2.15/bu). Although not tested in this trial, positive effects of soyhulls on fiber digestion may be more evident when long stemmed forage is used, due to increases in rate of passage and digestion which can influence feed intake.
References
NRC. 1985. Nutrient Requirements of Sheep. 6th Ed. National Academy Press, Washington, D.C.
SAS/STAT. 1988. SAS/STAT User's Guide: Statistics. SAS Institute, Inc., Cary, NC.