S.C. Loerch1, G.D. Lowe, and D.D. Clevenger
The Ohio State University Department of Animal Sciences
Abstract
Corn grain and pelleted soybean hulls are two relatively inexpensive feeds available to lamb feeders. Although the metabolizable energy value of corn is listed as being 50% greater than that of soyhulls (NRC, 1985), in practice this may not be the case due to associative effects of starch and fiber based feeds on digestion. The objective of this trial was to determine the effect of substituting soybean hulls for corn on lamb performance and cost of gain. One hundred (50 ewes and 50 wethers) Targhee x Hampshire lambs (initial weight 61 ± 0.5 lb) were used in a randomized complete block design experiment. Five diets were investigated: 1) 2/3 alfalfa:1/3 soyhulls; 2) 2/3 alfalfa:1/3 corn; 3) 1/3 alfalfa:2/3 soyhulls; 4) 1/3 alfalfa:2/3 corn; and 5) 1/3 alfalfa:1/3 soyhulls:1/3 corn. 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). Positive effects of soyhulls on fiber digestion may be more critical when long stemmed forage is used, due to increases in rate of passage and digestion which can influence feed intake.
Introduction
Corn grain and pelleted soybean hulls are two relatively inexpensive feeds available to lamb feeders. Although the metabolizable energy value of corn is listed as being 50% greater than that of soyhulls (NRC, 1985), in practice this may not be the case. Most of the metabolizable calories from corn come from starch. In feedlot diets, fermentation of starch lowers rumen pH and inhibits fiber digestion. Soybean hulls do not contain starch. The calories in soybean hulls are derived from the fermentation of the high quality, readily digestible fiber. While corn starch will depress fermentation of dietary fiber, soybean hulls actually enhance fiber fermentation. In this case, actual energy value of the diet may be greater than what would be predicted from book values. This phenomenon is called a "positive associative effect". The substitution value of soybean hulls for corn in growing lamb diets has not been previously determined. The objective of this trial was to determine the effect of substituting soybean hulls for corn on lamb performance and cost of gain.